JP5890139B2 - Drawing apparatus and focus adjustment method thereof - Google Patents

Description

  The present invention relates to a drawing apparatus that draws light by irradiating a substrate surface with a light beam, and a focus adjustment method of the drawing apparatus.

  In a drawing apparatus that performs drawing by focusing a light beam on the surface of a substrate placed on a stage, it is necessary to adjust the focus of a converging optical system in order to correctly focus the light beam on the surface of the substrate. However, since it is difficult to simultaneously detect whether or not the image is in focus while performing drawing, the relative position of the substrate with respect to the converging optical system is indirectly controlled by feedback control according to the focal position of the converging optical system. An autofocus technique for adjusting the focus has been proposed.

  For example, in the technique disclosed in Patent Document 1, the surface of the substrate irradiated with the drawing laser beam is irradiated with another light from an oblique direction with respect to the optical axis, and the reflected light from the substrate is received. Focus adjustment is performed by adjusting the height of the drawing head with respect to the substrate by utilizing the fact that the light receiving position of the reflected light changes according to the distance from the surface.

  Further, for example, in the technique described in Patent Document 2, a convergent optical image on the projection surface is detected by a CCD sensor provided on the opposite side of the drawing head across the projection surface of the laser beam from the drawing head, and the contrast of the image is maximized. The position of the focusing lens is adjusted so that the laser beam converges on the projection surface.

JP-A-9-318869 (for example, paragraph 0048) JP 2009-246165 A (for example, FIG. 2)

  The technique described in Patent Document 1 is based on the premise that the focal position of the focusing optical system of the drawing head does not vary. That is, control is performed such that the distance between the drawing head and the substrate is maintained at a predetermined value. However, since the focal position of the converging optical system actually varies and changes with time, the focal position can always be made to coincide with the substrate surface by simply maintaining a constant distance between the drawing head and the substrate. Is not limited.

  The technique described in Patent Document 2 can grasp the actual focal position of the converging optical system including changes over time. However, the focus control at the time of drawing on the substrate is described in Patent Document 2. Not. For this reason, it is unclear whether or not the focal position at the time of drawing can be matched with the substrate surface. In addition, since observation is performed on a preset projection plane, for example, a configuration that is not disclosed in Patent Document 2 is considered necessary in order to cope with a case where the thickness of the substrate changes. .

  As described above, there is room for improvement in the conventional technique in that the focal position of the converging optical system is appropriately adjusted on the surface of the substrate at the time of drawing while accommodating the temporal change of the converging optical system. In particular, it cannot be said that a focus adjustment technique capable of dealing with substrates having different thicknesses has been established at present.

  The present invention has been made in view of the above problems, and in a drawing apparatus for drawing by irradiating a light beam onto a substrate surface and a focus adjustment method thereof, it is possible to cope with a change with time of a converging optical system, and It is a first object of the present invention to provide a technique capable of appropriately adjusting the focal position of the converging optical system on the substrate surface during drawing. It is a second object of the present invention to provide a technique capable of appropriately adjusting the focal position of the converging optical system on the surface of each substrate corresponding to substrates having different thicknesses.

In order to achieve the first and second objects, a drawing apparatus according to the present invention has a stage on which a substrate can be placed in a horizontal state, and convergence optics for converging light from a light source on the substrate surface from a substantially vertical direction. A drawing means for drawing on the surface of the substrate with a converged light beam, and an irradiation position of the light beam from the drawing means relative to the substrate placed on the stage in a horizontal direction. A moving means for moving; an observation light receiving surface for receiving the light beam at a position different from the position of the substrate placed on the stage; and an observation means for observing an optical image incident on the observation light receiving surface; Observation height changing means for changing the vertical position of the observation light receiving surface, and before the vertical position is set substantially equal to the vertical position of the substrate surface placed on the stage by the observation height changing means A focus adjusting unit that adjusts a focus position in a vertical direction of the converging optical system based on an optical image observed by the observation unit in a state where the light beam from the drawing unit is irradiated on the observation light receiving surface; Detecting a vertical distance between the focusing optical system whose focal position has been adjusted and the observation light receiving surface and storing it as a reference distance, and at the time of drawing on the substrate surface by the drawing means, Distance detecting means for detecting a vertical distance from the substrate surface irradiated with the light beam as a drawing distance, and imaging a reference portion provided on the substrate surface placed on the stage, the substrate and the substrate and a position detecting means for detecting a relative position in the horizontal direction of the irradiation position of the light beam, the focal position in the vertical direction of the position detecting means, wherein the reference distance is detected Match of the vertical position of the observation light receiving surface, the focus adjusting means, the time by the drawing on the substrate surface rendering means, the drawing time distance between the reference distance and the vertical of the converging optical system based on It is characterized by adjusting the focal position in the direction.

In addition, in order to achieve the first and second objects, the focus adjustment method according to the present invention converges the light from the light source on the substrate surface from a substantially vertical direction, and a stage on which the substrate can be placed in a horizontal state. A drawing unit having a focusing optical system for drawing on the surface of the substrate by the converged light beam, and an irradiation position of the light beam from the drawing unit in a horizontal direction with respect to the substrate placed on the stage A moving means for relatively moving the image and a reference portion provided on the surface of the substrate on which the drawing apparatus is placed on the stage to detect a relative position in the horizontal direction between the substrate and the irradiation position of the light beam a focus adjusting method of the drawing apparatus having a position detecting means, for, unlike on the substrate where the horizontal position is placed on the stage, and vertical position is placed on the stage A reference setting step of setting the observation light receiving surface at a position substantially equal to the vertical position of the substrate surface, and observing the optical image of the light beam incident on the observation light receiving surface so that the optical image becomes the smallest A pre-focus adjustment step for adjusting a focal position in the vertical direction of the convergence optical system; a storage step for storing a vertical distance between the convergence optical system after the focus position adjustment and the observation light receiving surface as a reference distance; Drawing is performed by irradiating the surface of the substrate placed on a stage with the light beam, and detecting a vertical distance between the surface of the substrate irradiated with the light beam and the converging optical system; based on said reference distance, the focal position of the converging optical system and a rendering time focusing step of bringing the substrate surface, and the focal position in the vertical direction of the position detecting means, said reference setting It is characterized in that to match the vertical position of the observation light receiving surface set in extent. Here, “the optical image is the smallest” means a state in which the light beam is most narrowed and the contrast of the image is maximized.

  In the invention configured as described above, the focal position of the converging optical system is adjusted by observing the optical image of the light beam connected to the observation light receiving surface, as in the technique described in Patent Document 2. In addition, the vertical position of the observation light receiving surface can be changed, and the vertical position of the observation light receiving surface is set to be substantially the same as the substrate surface on the stage. The vertical distance between the convergent optical system and the observation light receiving surface when adjusted is stored as a reference distance. When drawing on the substrate surface by the drawing means, the focal position of the converging optical system is adjusted based on the distance (drawing distance) between the converging optical system and the substrate surface at that time and the reference distance. Thereby, the first and second objects are achieved.

  More specifically, it is as follows. First, Japanese Patent Application Laid-Open No. 2003-228561 describes a technique of adjusting the focal position of the converging optical system by detecting the distance between the converging optical system and the substrate surface at the time of drawing. However, in the technique described in Patent Document 1, there is no means for reflecting the actual focal position of the converging optical system at the target focal position corresponding to the reference distance of the present invention. On the other hand, in the present invention, the focal position in the actual converging optical system is adjusted by observation on the observation light receiving surface, and the distance between the converging optical system and the observation light receiving surface at that time is set as the reference distance. Therefore, the focal position can be matched with the substrate surface by adjusting the focal position at the time of drawing based on the reference distance. Further, even if the characteristics of the distance detecting means and the convergence optical system change with time, the reference distance corresponding to the characteristics at that time is set and the focus adjustment is performed by performing the operation as described above. It is possible to deal with changes with time. Thereby, the first object is achieved.

Further, such setting of the reference distance, performed using the observation light receiving surface provided on the substantially same position as the substrate surface in the vertical direction, and since the vertical position of the observation light receiving surface is variable, the thickness of the substrate Even when the vertical position of the substrate surface changes due to changes in the position, the focal position can be accurately set according to the position. Thereby, the second object is achieved. In addition, the image sensor includes a position detection unit that detects a relative position in the horizontal direction between the substrate and the irradiation position of the light beam by imaging a reference portion provided on the surface of the substrate placed on the stage. By configuring the focal position to match the vertical position of the observation light receiving surface when the reference distance is detected, horizontal alignment between the substrate and the irradiation position of the light beam, that is, alignment adjustment is possible. It is. Then, by aligning the focal position of the position detection means with the vertical position of the observation light receiving surface when the reference distance is detected, the position detection means, the focus adjustment means and the distance detection means are all unified through the observation light reception surface. Therefore, the drawing operation performed in cooperation with each other can be controlled with higher accuracy.

  In the drawing apparatus according to the invention, for example, the observation light receiving surface is formed of a material having transparency to the light beam, and the observation means observes the optical image of the observation light reception surface from the side opposite to the incident direction of the light beam. It may be configured. In this way, an optical image can be observed on the optical axis of the light beam, and the size can be detected with high accuracy, so that the focal position can be adjusted with high accuracy.

  In addition, for example, the distance detection unit includes an irradiation unit that irradiates light on a substrate surface irradiated with a light beam from a direction different from the incident direction of the light beam, and a reflected optical image formed by reflecting the light on the substrate surface. And a light receiving unit that detects the distance between the converging optical system and the substrate surface based on the position of the reflected optical image received by the light receiving unit. In this case, the distance between the converging optical system and the substrate surface is reflected in the position of the reflected optical image incident on the light receiving unit. By detecting this, the distance between the converging optical system and the substrate surface is grasped. It is possible. In addition, by receiving the reflected optical image from the observation light receiving surface with the same configuration, the distance between the converging optical system and the observation light receiving surface can be similarly obtained.

Further, for example, a reference pattern for adjusting the focal position of the position detecting means may be provided on the observation light receiving surface. By doing so, it is possible to adjust the focal position of the position detecting means using the reference pattern on the observation light receiving surface, and at the same time, the common reference setting for the focus adjusting means and the distance detecting means can be performed. Thus, the adjustment operation before drawing can be performed efficiently.

  In these drawing apparatuses, for example, the converging optical system may include a focusing lens that can move in the vertical direction, and the focus adjustment unit may control the vertical position of the focusing lens. As a result, it is not necessary to move the entire light source and the converging optical system, and the accuracy of position control can be improved.

  In the focus adjustment method according to the present invention, for example, in the focus adjustment step during drawing, the focus position set in the pre-adjustment step is changed to a position changed by a distance corresponding to the difference between the detection result and the reference distance. The focal position of the system may be adjusted. By doing so, the focal position can be changed so as to cancel the difference between the distance between the converging optical system and the substrate surface at the time of drawing and the reference distance, and the light beam can be converged on the substrate surface.

Further, for example, a reference pattern may be provided on the observation light receiving surface, the reference pattern may be imaged by the position detection means, and the focus position may be adjusted based on the result.

  In these cases, for example, the distance between the position detection means and the observation light receiving surface when the focus position in the vertical direction of the position detection means matches the vertical position of the observation light receiving surface set in the reference setting step is stored. You may make it leave. This distance is a reference for focus adjustment in the position detection means, as is the reference distance in focus adjustment of the converging optical system. Therefore, by storing this together with the reference distance, each part can be controlled while grasping the relative positional relationship in the vertical direction between the converging optical system and the position detecting means. Further, for example, when there is a change in the thickness of the substrate to be drawn, it is possible to execute control taking the change into each of the convergent optical system and the position detection unit.

  Further, in these focus adjustment methods, after drawing by the drawing unit on the first substrate, when drawing by the drawing unit on the second substrate different from the first substrate, for example, If the substrates have the same thickness, the reference setting step, the pre-focus adjustment step, and the storage step for the second substrate are omitted, and the drawing focus adjustment step is executed using the reference distance in the first substrate, while different thicknesses are used. In this case, the reference setting process, the pre-focus adjustment process, the storage process, and the drawing focus adjustment process may be executed on the second substrate.

  When drawing back and forth with respect to a plurality of substrates, if the substrate thickness is the same, there is no need to change the adjustment result in the vertical direction. Throughput can be improved. On the other hand, if the thickness is different, the above operation is performed again, and the adjustment that reflects the state of the device at that time is performed. Therefore, stable and highly accurate drawing can be performed in response to changes in the device over time. Can be done.

  According to the present invention, the focusing optical system is adjusted based on the optical image of the light beam connected to the observation light receiving surface provided at substantially the same position as the substrate surface in the vertical direction, and the convergence optical system and the observation light receiving surface at that time are adjusted. Is stored as a reference distance, and at the time of drawing on the substrate surface, the focal position of the convergence optical system is adjusted based on the distance between the convergence optical system and the substrate surface and the reference distance. Thereby, the focal position of the converging optical system at the time of drawing can be made to coincide with the substrate surface stably regardless of changes in the characteristics of the converging optical system and the position detecting means with time.

It is a front view showing one embodiment of a pattern drawing device concerning the present invention. It is a top view of the pattern drawing apparatus of FIG. It is a figure which shows the structure of the optical head 40a in more detail. It is a figure which shows the structure for performing a calibration. It is a figure which shows the detailed structure of an alignment unit. It is a flowchart which shows the calibration operation | movement in this apparatus. It is a figure which shows typically a part of process in the operation | movement of FIG. It is a flowchart which shows the focus adjustment operation | movement at the time of drawing. It is a figure which shows typically the focus adjustment operation | movement at the time of drawing.

  FIG. 1 is a front view showing an embodiment of a pattern drawing apparatus according to the present invention. FIG. 2 is a plan view of the pattern drawing apparatus of FIG. The pattern drawing apparatus 100 is an apparatus that draws a pattern by irradiating light on the upper surface of a substrate W on which a layer of a photosensitive material such as a resist is formed. The substrate W may be any of various substrates such as a semiconductor substrate, a printed substrate, a color filter substrate, a glass substrate for a flat panel display provided in a liquid crystal display device or a plasma display device, and an optical disk substrate. In the illustrated example, the upper layer pattern is drawn so as to overlap the lower layer pattern formed on the surface of the circular semiconductor substrate.

  The pattern drawing apparatus 100 includes an inside of the main body formed by attaching cover panels (not shown) to the ceiling surface and the peripheral surface of the skeleton composed of the main body frame 101, and an outside of the main body that is outside the main body frame 101. The various components are arranged.

  The main body of the pattern drawing apparatus 100 is divided into a processing area 102 and a delivery area 103. Among these areas, the stage 10, the stage moving mechanism 20, the stage position measuring unit 30, the optical unit 40, and the alignment unit 60 are mainly arranged in the processing area 102. On the other hand, in the transfer area 103, a transfer device 70 such as a transfer robot for transferring the substrate W to and from the processing area 102 is arranged.

  Further, an illumination unit 61 that supplies illumination light to the alignment unit 60 is disposed outside the main body of the pattern drawing apparatus 100. In addition, a control unit 90 that is electrically connected to each unit of the pattern drawing apparatus 100 and controls the operation of each unit is disposed outside the main body.

  In addition, a cassette placement unit 104 for placing the cassette C is disposed outside the main body of the pattern drawing apparatus 100 at a position adjacent to the transfer area 103. Further, the transfer device 70 corresponding to the cassette placement unit 104 and disposed in the transfer area 103 inside the main body takes out the unprocessed substrate W accommodated in the cassette C placed on the cassette placement unit 104. The substrate W is loaded into the processing region 102 (loading), and the substrate W is unloaded from the processing region 102 and is stored in the cassette C. Delivery of the cassette C to the cassette mounting unit 104 is performed by an external transport device (not shown). The loading process of the unprocessed substrate W and the unloading process of the processed substrate W are performed by operating the transfer device 70 in accordance with an instruction from the control unit 90.

  The stage 10 has a flat outer shape, and is a holding unit that places and holds the substrate W in a horizontal posture on the upper surface thereof. A plurality of suction holes (not shown) are formed on the upper surface of the stage 10, and by applying a negative pressure (suction pressure) to the suction holes, the substrate W placed on the stage 10 is placed on the stage 10. It can be fixedly held on the upper surface of the. Then, the stage 10 is moved by the stage moving mechanism 20.

  The stage moving mechanism 20 is a mechanism that moves the stage 10 in the main scanning direction (Y-axis direction), the sub-scanning direction (X-axis direction), and the rotation direction (rotation direction around the Z axis (θ-axis direction)). The stage moving mechanism 20 includes a base plate 24 that supports a support plate 22 that rotatably supports the stage 10, a sub-scanning mechanism 23 that moves the support plate 22 in the sub-scanning direction, and a main plate that moves the base plate 24 in the main scanning direction. And a scanning mechanism 25. The sub scanning mechanism 23 and the main scanning mechanism 25 move the stage 10 in accordance with an instruction from the control unit 90.

  The sub-scanning mechanism 23 includes a linear motor 23 a configured by a moving element (not shown) attached to the lower surface of the support plate 22 and a stator (not shown) laid on the upper surface of the base plate 24. In addition, a pair of guide portions 23 b extending in the sub-scanning direction is provided between the support plate 22 and the base plate 24. For this reason, when the linear motor 23 a is operated, the support plate 22 moves in the sub-scanning direction X along the guide portion 23 b on the base plate 24.

  The main scanning mechanism 25 has a linear motor 25 a composed of a mover attached to the lower surface of the base plate 24 and a stator laid on the base 106 of the pattern drawing apparatus 100. A pair of guide portions 25b extending in the main scanning direction is provided between the base plate 24 and the base 106. Therefore, when the linear motor 25 a is operated, the base plate 24 moves in the main scanning direction Y along the guide portion 25 b on the base 106.

  The stage position measurement unit 30 is a mechanism that measures the position of the stage 10. The stage position measurement unit 30 is electrically connected to the control unit 90 and measures the position of the stage 10 in accordance with an instruction from the control unit 90. The stage position measurement unit 30 is configured by a mechanism that irradiates a laser beam toward the stage 10 and measures the position of the stage 10 by using interference between the reflected light and the emitted light, for example. The operation is not limited to this. In this embodiment, the stage position measurement unit 30 includes an emission unit 31 that emits laser light, a beam splitter 32, a beam bender 33, a first interferometer 34, and a second interferometer 35. The emission unit 31 and the interferometers 34 and 35 are electrically connected to the control unit 90 and measure the position of the stage 10 in accordance with an instruction from the control unit 90.

  The laser light emitted from the emission unit 31 first enters the beam splitter 32 and is branched into first branched light that goes to the beam bender 33 and second branched light that goes to the second interferometer 35. The first branched light is reflected by the beam bender 33, enters the first interferometer 34, and is irradiated from the first interferometer 34 to the first portion of the stage 10. Then, the first branched light reflected by the first part is incident on the first interferometer 34 again. The first interferometer 34 is a positional parameter corresponding to the position of the first part based on the interference between the first branched light traveling toward the first part of the stage 10 and the first branched light reflected by the first part. Measure.

  On the other hand, the second branched light is incident on the second interferometer 35 and the second part of the stage 10 from the second interferometer 35 (however, the second part is a position different from the first part. .). Then, the second branched light reflected by the second part is incident on the second interferometer 35 again. The second interferometer 35 corresponds to the position of the second part based on the interference between the second branched light traveling toward the second part of the stage 10 and the second branched light reflected by the second part of the stage 10. The measured position parameter is measured.

  The control unit 90 obtains a position parameter corresponding to the position of the first part of the stage 10 and a position parameter corresponding to the position of the second part of the stage 10 from each of the first interferometer 34 and the second interferometer 35. get. Then, the position of the stage 10 is calculated based on each acquired position parameter.

  The alignment unit 60 images an alignment mark (not shown) formed on the upper surface of the substrate W. The alignment unit 60 includes an alignment camera 601 having a lens barrel, an objective lens, and a CCD image sensor. The CCD image sensor provided in the alignment camera 601 is constituted by, for example, an area image sensor (two-dimensional image sensor). The alignment unit 60 is supported by a lifting mechanism (not shown) so as to be lifted and lowered within a predetermined range.

  The illumination unit 61 is connected to the lens barrel via the fiber 601 and supplies illumination light to the alignment unit 60. The light guided by the fiber 601 extending from the illumination unit 61 is guided to the upper surface of the substrate W through the lens barrel of the alignment camera 601, and the reflected light is received by the CCD image sensor through the objective lens. As a result, the upper surface of the substrate W is imaged and image data is acquired. The alignment camera 601 is electrically connected to the image processing unit of the control unit 90, acquires imaging data in accordance with an instruction from the control unit 90, and transmits the acquired imaging data to the control unit 90.

  Based on the imaging data provided from the alignment camera 601, the control unit 90 detects the reference mark provided at the reference position of the substrate W and performs an alignment process for positioning the relative position between the optical unit 40 and the substrate W. Then, pattern writing is performed by irradiating a predetermined position of the substrate W with a light beam modulated according to the drawing pattern from the optical unit 40.

  In the present embodiment, the optical unit 40 includes two optical heads 40a and 40b. The optical heads 40a and 40b both have the same configuration, and modulate the laser light supplied from the light irradiation unit based on strip data corresponding to the drawing pattern. Here, the configuration related to the optical head 40a will be described with reference to FIG. 1, but the optical head 40b is configured similarly. The number of optical heads installed is not limited to this and is arbitrary.

  The light irradiation unit 41 includes a laser driving unit 411, a laser oscillator 412, and an illumination optical system 413. In the light irradiation unit 41, laser light is emitted from the laser oscillator 412 by the operation of the laser driving unit 411, and is introduced into the optical head 40 a via the illumination optical system 413. The optical head 40a is provided with a light modulation element, and modulates the laser light based on the strip data. Then, the optical head 40a exposes the substrate W held on the stage 10 by directing the modulated laser light onto the substrate W moving immediately below the optical head 40a, thereby drawing a pattern. As a result, the upper layer pattern (drawing pattern) is drawn over the lower layer pattern formed on the unprocessed substrate W.

  FIG. 3 is a diagram showing the configuration of the optical head 40a in more detail. The configuration of the other optical head 40b is also the same. The optical head 40a includes a light modulation unit 421 having a diffraction grating type spatial light modulator. The laser light L from the laser oscillator 412 is guided by the illumination optical system 413 and the mirror 422 to the light modulation unit 421 in which the normal line of the reflection surface thereof is inclined with respect to the optical axis.

  At this time, the incident light from the laser oscillator 412 is converted into linear light (light having a cross section of the light beam) having a uniform intensity distribution by the illumination optical system 413, and enters the effective region of the modulation operation on the spatial light modulator 421. Irradiated. In the spatial light modulator 421, the light from the mirror 422 is spatially modulated based on a control command from the control unit 90 and is incident on the lens of the projection optical system 430 along the optical axis.

  The light that has passed through the lens of the projection optical system 430 is guided to the zoom lens and is guided onto the substrate W through the focusing lens 431 at a predetermined magnification. The focusing lens 431 is attached to the focus drive mechanism 432, and the focus drive mechanism 432 moves the focusing lens 431 up and down along the vertical axis (Z axis) in response to a control command from the focus control unit 901 of the control unit 90. The light beam emitted from the focusing lens 431 is converged on the surface S of the substrate W.

  In addition, under the housing of the optical head 40a, as an autofocus unit, for example, a laser diode (LD) is used as a light source, and light is directed toward the surface S of the substrate W in accordance with a control signal from the LD drive unit 902 of the control unit 90. An irradiation unit 441 that irradiates and an image sensor 442 that includes, for example, a CMOS sensor or a one-dimensional CCD image sensor that receives reflected light from the substrate surface S of the irradiation light is provided.

  Here, consider a case where the distance between the optical head 40a and the substrate surface S varies. In the figure, when the substrate surface S moves away from the optical head 40a as shown by a solid line arrow or when the substrate surface S approaches the optical head 40a as shown by a broken line arrow, the optical path of the reflected light from the substrate surface S is respectively It changes in the direction shown by the solid line arrow and the broken line arrow, and the received light amount at each light receiving position of the image sensor 442 also varies. That is, the peak position of the received light amount in the image sensor 442 changes as indicated by solid line arrows and broken line arrows, respectively. The autofocus unit uses this to detect the distance between the optical head 40a and the substrate surface S.

  Specifically, the distance detection unit 903 of the control unit 90 receives a signal output from the image sensor 442, and uses this for focus control as information corresponding to the distance between the optical head 40a and the substrate surface S. Further, the information is stored in the storage unit 904 as necessary. The information corresponding to the distance between the optical head 40a and the substrate surface S may be the result of calculating the distance from the output signal of the image sensor 442, or the peak position itself of the amount of light received by the image sensor 442. There may be. This is because these correspond one-to-one.

  When the distance between the optical head 40a and the substrate surface S varies, the focal position of the light beam emitted from the focusing lens 431 deviates from the substrate surface S, and the resolution of the drawing pattern decreases. In order to prevent this, the focus control unit 901 controls the focus drive mechanism 432 to move the focusing lens 431 up and down, thereby preventing the focus position from being shifted. By performing feedback control using the output signal of the image sensor 442, the focal position of the focusing lens 431 is moved up and down following the vertical position fluctuation of the substrate surface S, and the light beam is stably directed to the substrate surface S. Can be converged to.

  In order to make the above autofocus operation function effectively, it is necessary to know in advance the distance between the optical head 40a and the substrate surface S when the focusing lens 431 is focused on the substrate surface S. This distance does not change much in the short term, but it varies over time as the device is used for a long time. Next, a configuration for calibration for correcting this will be described.

  FIG. 4 is a diagram showing a configuration for performing calibration. As shown in FIG. 4A, an observation optical system 80 for receiving the light beam emitted from the optical heads 40a and 40b and observing the optical image is provided on the side of the stage 10. In the observation optical system 80, for example, a transparent dummy substrate 801 formed in a flat plate shape from quartz glass is provided substantially horizontally. As shown in FIG. 4B, a reference mask pattern 802 is formed on the surface (upper surface 801a) of the dummy substrate 801, and is used for focus adjustment of the alignment unit 60 as described later.

  An observation camera 803 having an imaging unit composed of, for example, a two-dimensional CCD image sensor and an optical system for converging incident light is provided below the dummy substrate 801, that is, on the opposite side to the optical heads 40a and 40b across the dummy substrate 801. Provided. The dummy substrate 801 and the observation camera 803 are respectively attached to and integrated with the case 804, and the focal position of the optical system of the observation camera 803 is adjusted to match the upper surface 801 a of the dummy substrate 801.

  The case 804 is supported by a support frame 805 erected on the support plate 22 so as to be movable up and down, and its vertical position is adjusted by an observation system control unit 920 of the control unit 90 and an observation system lift mechanism 806 having an appropriate drive mechanism. Is controlled. That is, the dummy substrate 801 and the observation camera 803 of the observation optical system 80 are integrally moved with the stage 10 in the horizontal direction, and can be moved up and down independently of the stage 10 in the vertical direction. ing.

  While the observation optical system 80 is positioned immediately below the optical head 40a (or 40b) and the upper surface 801a of the dummy substrate 801 is positioned at substantially the same position as the upper surface S of the substrate W placed on the stage 10, The observation camera 803 picks up an optical image that is incident on the dummy substrate upper surface 801a from the optical head 40a and forms an image. The output signal is subjected to data processing by the image processing unit 910 of the control unit 90. The focus control unit 901 changes the vertical position of the focusing lens 431 while taking an image with the observation camera 803 so that the optical image becomes the smallest (so that the contrast of the image is maximized). Set the direction position. As a result, the focusing lens 431 is focused on the upper surface 801a of the dummy substrate. At this time, the distance between the optical head 40a and the dummy substrate upper surface 801a is set as a “reference distance”, and the distance detection unit 903 stores information corresponding to the reference distance in the storage unit 904.

  In subsequent drawing operations, the position of the focusing lens 431 is controlled based on a comparison between the distance between the optical head 40a and the substrate surface S facing the optical head 40a and the above-described reference distance. S can be adjusted. In addition, by periodically performing this calibration operation at a predetermined timing, it is possible to stably adjust the focal position over a long period of time in response to the temporal change of the projection optical system 430.

  FIG. 5 is a diagram showing a detailed configuration of the alignment unit. In the figure, for comparison with the alignment unit 60, an autofocus portion of the optical head 40a is also shown. The alignment unit 60 detects the reference mark on the substrate surface to grasp the horizontal position between the optical head 40 a and the stage 10 or the substrate W, and detects the reference mask pattern 802 of the observation optical system 80 to detect the alignment unit 60. Focus adjustment is performed.

  As shown in FIG. 5, the alignment unit 60 includes an alignment camera 601 that images the substrate surface S, and an irradiating unit 641 having the same function as the irradiating unit 441 provided in the optical head 40 a as an autofocus unit. In addition, a light receiving unit 642 having a function equivalent to that of the light receiving unit 442 provided in the optical head 40a is provided. Similar to the autofocus unit of the optical head 40a, the distance detection unit 906 provided in the control unit 90 detects the distance between the alignment camera 601 and the substrate surface S based on the output of the light receiving unit 642, and the focus control unit 930. However, the vertical position of the alignment unit 60 is controlled so that the focal position of the alignment camera 601 coincides with the substrate surface S.

  Even in this case, information on a distance that serves as a reference for the alignment of the alignment camera 601 is necessary, and the distance may change over time. Therefore, the reference mask pattern 802 is used on the upper surface 801a of the dummy substrate of the observation optical system 80. That is, the observation optical system 80 is positioned directly below the alignment unit 60, the image processing unit 910 performs data processing on the reference mask pattern 802 captured by the alignment camera 601, and the alignment camera 601 and the dummy substrate when the pattern becomes the clearest By detecting the distance from the upper surface 801a and storing it as a reference, the autofocus operation of the alignment camera 601 becomes possible. Further, by periodically performing the above operation, it is possible to perform a stable autofocus operation over a long period of time in response to a change in characteristics of the alignment camera 601 over time.

  So far, the principle of control operation for each unit has been described. Next, a calibration operation in the entire pattern drawing apparatus 100 based on the above principle will be described. When the calibration process described below is executed, the focal position can be adjusted for each of the optical heads 40a and 40b and the alignment unit 60, and the vertical direction (Z-axis) between the optical heads 40a and 40b and the alignment unit 60 can be adjusted. The pattern drawing apparatus 100 can be operated in the best state by relatively adjusting the focal position in (direction) based on the same reference.

  FIG. 6 is a flowchart showing the calibration operation in this apparatus. FIG. 7 is a diagram schematically showing a part of the process in the operation of FIG. This calibration operation is an operation that is performed, for example, immediately after activation of the apparatus or at a regular timing (for example, once a day) and before the substrate W is carried into the apparatus.

  First, the initial position of the alignment camera 601 is set. Specifically, the vertical position of the alignment camera 601 is set so that the focal position matches the vertical position of the substrate surface S assumed on the stage 10 according to the thickness of the substrate W to be loaded. (Step S101). As shown in FIG. 7A, since the substrate W has not been carried in at this time, the positioning may be approximate.

  Subsequently, the stage 10 is moved to move the observation optical system 80 directly below the alignment unit 60 (step S102), and the upper surface 801a of the dummy substrate of the observation optical system 80 is matched with the focal position of the alignment camera 601 (step S103). . Specifically, as shown in FIG. 7B, the case 804 of the observation optical system 80 is moved up and down by the observation system lifting mechanism 806 while imaging the reference mask pattern 802 formed on the upper surface 801a of the dummy substrate with the alignment camera 601. Then, the case 804 is positioned at a position where the image of the reference mask pattern 802 is the clearest.

  As a result, the vertical position of the upper surface 801a of the dummy substrate substantially coincides with the position of the surface S of the substrate to be loaded later, and the alignment camera 601 is in focus at that position. Therefore, in order to use the distance between the alignment camera 601 and the dummy substrate upper surface 801a as a reference, information on the distance is obtained from the output of the light receiving unit 642 of the autofocus unit (AF unit) and stored in the storage unit 904. (Step S104). Thereafter, the focus adjustment of the alignment camera 601 at the time of drawing is performed based on this distance. The specific method is as described above.

  Note that the position setting of the dummy substrate upper surface 801a in this calibration operation is approximate, and does not always completely coincide with the position of the substrate surface S placed on the stage 10. However, since the focal position of the alignment camera 601 and the information related to the distance of the autofocus unit corresponding thereto are associated by the above operation, the position of the substrate surface S actually placed on the stage 10 is the upper surface of the dummy substrate. Even if it is slightly deviated from the position 801a, it is possible to focus on that position. However, if calibration is performed in a state where the position of the dummy substrate upper surface 801a is largely deviated from the position of the substrate surface S at the time of drawing, the substrate surface S at the time of drawing may be out of the focus adjustment range. In this sense, it is effective to perform calibration by matching the vertical position of the dummy substrate upper surface 801a with the assumed position of the substrate surface S. This also applies to the following calibration of the optical head.

  Next, focus adjustment of the optical heads 40a and 40b is performed. Although the operation for the optical head 40a is illustrated here, the operation for the optical head 40b is the same. First, the observation optical system 80 is moved and positioned directly below the optical head 40a (step S105). Then, as shown in FIG. 7C, the vertical position of the focusing lens 431 is determined while observing the optical image of the laser light incident on the dummy substrate upper surface 801a through the focusing lens 431 of the projection optical system 430 with the observation camera 803. By changing, the position of the focusing lens 431 is set to the position where the spot size of the optical image becomes the smallest (step S106).

  Thereby, the projection optical system 430 is focused on the dummy substrate upper surface 801a. Then, using the distance between the optical head 40a and the dummy substrate upper surface 801a at this time as a reference distance, information on the reference distance is obtained from the output of the light receiving unit 422 and stored in the storage unit 904 (step S107). Thereafter, the focus adjustment of the projection optical system 430 at the time of drawing is performed based on this reference distance. The specific method is as described above in principle, but will be described in more detail in accordance with the present embodiment.

  FIG. 8 is a flowchart showing the focus adjustment operation during drawing. As shown in FIG. 3, the optical head 40a faces the substrate surface S at the time of drawing. In this state, information on the distance between the optical head 40a and the substrate surface S is obtained based on the output from the light receiving unit 442 of the autofocus unit (AF unit) (step S201), and the reference distance stored in the storage unit 904 and Is obtained (step S202). Here, if there is no difference between the two, the focal point is in alignment with the substrate surface S and there is no need to change it. However, if there is a difference, the focal point position is offset from the substrate surface S, and the difference is corrected. Specifically, in order to move the focusing lens 431 in a direction that eliminates the above difference in distance, the driving amount (for example, the moving distance of the focusing lens 431 in the vertical direction, the number of pulses of the driving motor that realizes the driving distance) is calculated. Then (step S203), the focusing lens 431 is moved upward or downward by the calculated drive amount (step S204). The above operation is continued until drawing is completed (step S205).

  FIG. 9 is a diagram schematically showing a focus adjustment operation at the time of drawing. As shown in FIG. 9A, the distance between an appropriate reference position (in this example, the lower end) of the optical head 40a and the substrate surface S is represented by reference numeral D1. Further, the driving amount of the focusing lens 431 for focus adjustment (in this example, the movement distance in the vertical direction) is represented by the symbol D2. Regarding the distance D1, the direction from the lower end of the optical head 40a toward the substrate surface S is the positive direction. With respect to the driving amount D2, the focusing lens 431 is set upward, that is, the direction away from the substrate surface S is the positive direction.

  If the distance D1 coincides with the reference distance as a result of the previous calibration operation, it can be said that the projection optical system 430 is focused on the substrate surface S. Accordingly, the driving amount D2 at this time is zero, that is, the vertical position of the focusing lens 431 is maintained at the position set by the calibration operation. On the other hand, when the distance D1 is greater than the reference distance, the drive amount D2 is set to a negative value, that is, the focusing lens 431 is moved downward to eliminate the focus shift. On the other hand, when the distance D1 is smaller than the reference distance, the driving amount D2 is set to a positive value and the focusing lens 431 is moved upward to eliminate the focus shift. The greater the deviation of the distance D1 from the reference distance, the greater the driving amount D2 of the focusing lens 431. In this way, the focal position of the projection optical system 430 is stably maintained on the substrate surface S.

  As described above, in this embodiment, in the observation optical system 80 having the dummy substrate 801 and the observation camera 803, the dummy substrate 801 and the observation camera 803 are integrally movable in the vertical direction. In the calibration operation, a light beam from the optical head 40a is incident on the dummy substrate upper surface 801a in a state where the upper surface 801a of the dummy substrate 801 is positioned at an assumed position on the surface S of the substrate W placed on the stage 10. The vertical position of the focusing lens 431 is set so that the optical image becomes the smallest by observing this with the observation camera 803. Information on the reference distance obtained from the output of the autofocus unit at this time is stored, and based on the reference distance and the distance between the optical head 40a and the substrate surface S obtained from the output of the autofocus unit at the time of drawing. Adjust the focus. Even if the reference distance fluctuates due to changes in the autofocus unit and the projection optical system 430 with time, the reference distance at that time is set by performing such calibration, and focus adjustment based on the reference distance is performed. In addition, it is possible to adjust the focus with high accuracy and long-term stability.

  Further, the focus adjustment of the alignment unit 60 is also performed using the reference mask pattern 802 formed on the upper surface 801a of the dummy substrate 801 set at the same position as above, so that the focal position of the optical head 40a and the focus of the alignment unit 60 are adjusted. The relative positional relationship in the vertical direction with the position is associated through the dummy substrate upper surface 801a, which is a common position reference. For this reason, it is possible to achieve cooperation between two units that are originally controlled independently. Thereby, the pattern drawing apparatus 100 can be operated in the best state.

  Since the upper surface 801a of the dummy substrate, which serves as a vertical position reference for the optical head 40a and the alignment unit 60, can be raised and lowered according to the surface position of the substrate W placed on the stage 10, the substrate has various thicknesses. It is possible to perform highly accurate and stable focus adjustment for W.

  That is, after performing the calibration operation and the drawing operation corresponding to the first substrate having a predetermined thickness, if the next substrate has the same thickness, without performing a new calibration operation, A drawing operation can be performed using the result of the calibration operation for the previous substrate. The new calibration operation may be performed periodically at predetermined intervals, for example, when the number of processed substrates, the operation time, etc. reach a certain value.

  On the other hand, when performing a drawing operation on a second substrate having a different thickness from the previous substrate, a new calibration is performed according to the thickness of the substrate and the reference distance is reset, Similarly for the second substrate, the focus adjustment at the time of drawing can be performed with high accuracy and stability.

  As described above, in this embodiment, the optical heads 40a and 40b and the light irradiation unit 41 function as a “drawing unit” of the present invention. Among these, the laser oscillator 412 functions as the “light source” of the present invention, while the projection optical system 430 functions as the “converging optical system” of the present invention.

  In this embodiment, the stage moving mechanism 20 functions as the “moving means” of the present invention. In this embodiment, the observation optical system 80 functions as the “observation means” of the present invention, and the upper surface 801a of the dummy substrate 801 corresponds to the “observation optical surface” of the present invention. The reference mask pattern 802 corresponds to the “reference pattern” of the present invention. Further, the observation system lifting mechanism 806 and the observation system control unit 920 function as the “observation height changing unit” of the present invention as a unit.

  In this embodiment, the focus control unit 901 and the focus drive mechanism 432 function as a “focus adjustment unit” of the present invention. Further, the irradiation unit 441 and the light receiving unit 442 constituting the autofocus unit integrally function as the “distance detection unit” of the present invention. Furthermore, in this embodiment, the alignment unit 60 functions as the “position detecting means” of the present invention.

  In the calibration operation of this embodiment shown in FIG. 6, step S103 corresponds to the “reference setting step” of the present invention, and step S106 corresponds to the “pre-focus adjustment step”. Step S107 corresponds to the “storage process” of the present invention. Further, steps S201 to S204 in FIG. 8 correspond to the “focus adjustment step during drawing” of the present invention.

  The present invention is not limited to the above-described embodiment, and various modifications other than those described above can be made without departing from the spirit of the present invention. For example, in the calibration operation of the above embodiment, the calibration of the optical head 40a (40b) and the calibration of the alignment unit 60 are performed together. The present invention may be applied only to the focus adjustment operation to be performed.

  In the calibration operation of the above embodiment, the vertical position of the alignment unit 60 is set so that the focus position of the alignment camera 601 is the assumed position of the substrate surface S, and the position of the dummy substrate upper surface 801a is set accordingly. Thus, the approximate position of the dummy substrate upper surface 801a is set to the position of the substrate surface S. However, the present invention is not limited to this. For example, the position of the upper surface 801a of the dummy substrate may be set first, and then the position of the alignment unit 60 may be adjusted so as to be focused.

  In addition, the autofocus unit in the alignment unit 60 and the optical heads 40a and 40 in the above embodiment irradiates the substrate surface S with light and receives the reflected light, and detects the distance based on the position of the reflected image. However, the distance detection means is not limited to this, and any means can be applied.

  The pattern drawing apparatus 100 of the above embodiment is an apparatus that performs pattern drawing by modulating a light beam with a spatial modulator 421 using a diffraction grating. However, the modulation method of the light beam is not limited to this, and is arbitrary. It is possible to apply the present invention to a drawing apparatus that uses this modulation method.

  The present invention can be applied to any drawing apparatus that performs drawing by focusing a light beam on the surface of a substrate. As a substrate to be processed, various substrates such as a semiconductor substrate, a printed substrate, a color filter substrate, a glass substrate for a flat panel display provided in a liquid crystal display device or a plasma display device, and an optical disk substrate can be used. is there.

10 stage 20 stage moving mechanism (moving means)
40a, 40b Optical head (drawing means)
41 Light irradiation part (drawing means)
60 Alignment unit (position detection means)
80 Observation optical system (observation means)
412 Laser oscillator (light source, drawing means)
430 Projection optical system (convergence optical system, drawing means)
432 Focus drive mechanism (focus adjustment means)
441 Irradiation unit (distance detection means)
442 Light-receiving part (distance detection means)
801a (Dummy substrate 801) upper surface (observation optical surface)
802 Reference mask pattern (reference pattern)
806 Observation system lifting mechanism (observation height changing means)
901 Focus control unit (focus adjustment means)
920 Observation system control unit (observation height changing means)
S Substrate surface S103 Reference setting step S106 Prefocus adjustment step S107 Storage step S201 to S204 Drawing focus adjustment step W substrate

Claims (10)

A stage on which the substrate can be placed horizontally;
A drawing unit that has a converging optical system for converging light from a light source on the substrate surface from a substantially vertical direction, and drawing on the substrate surface by a converged light beam;
Moving means for moving the irradiation position of the light beam from the drawing means in a horizontal direction relative to the substrate placed on the stage;
An observation light receiving surface for receiving the light beam at a position different from the position of the substrate placed on the stage, and an observation means for observing an optical image incident on the observation light receiving surface;
Observation height changing means for changing the vertical position of the observation light receiving surface;
The light beam from the drawing unit is irradiated onto the observation light receiving surface whose vertical position is set substantially equal to the vertical position of the substrate surface placed on the stage by the observation height changing unit. In a state, a focus adjustment unit that adjusts a focus position in the vertical direction of the convergent optical system based on an optical image observed by the observation unit;
A vertical distance between the converging optical system whose focal position is adjusted and the observation light receiving surface is detected and stored as a reference distance, and the converging optical system and the light are drawn when drawing on the substrate surface by the drawing means. Distance detecting means for detecting a vertical distance from the substrate surface irradiated with the beam as a drawing time distance ;
Position detecting means for detecting a relative position in the horizontal direction between the substrate and the irradiation position of the light beam by imaging a reference portion provided on the surface of the substrate placed on the stage ;
The focal position in the vertical direction of the position detection means coincides with the vertical position of the observation light receiving surface when the reference distance is detected,
The focus adjustment means adjusts a focus position in a vertical direction of the convergent optical system based on the drawing distance and the reference distance when drawing on the substrate surface by the drawing means. apparatus.   The observation light-receiving surface is formed of a material having transparency to the light beam, and the observation unit observes the optical image of the observation light-receiving surface from a side opposite to the incident direction of the light beam. Drawing device.   The distance detecting means includes an irradiation unit that irradiates light on the substrate surface irradiated with the light beam from a direction different from the incident direction of the light beam, and reflective optics formed by reflecting the light on the substrate surface. The drawing apparatus according to claim 1, further comprising: a light receiving unit that receives an image, and detecting a distance between the convergent optical system and the substrate surface based on a position of the reflected optical image received by the light receiving unit. . The drawing apparatus according to claim 1, wherein a reference pattern for adjusting a focal position of the position detecting unit is provided on the observation light receiving surface. The converging optical system comprises a possible focusing lens moves in a vertical direction, the focal point adjusting means drawing device according to any one of claims 1 to 4 for controlling the vertical position of the focusing lens. A stage capable of placing the substrate in a horizontal state; a drawing means for drawing on the substrate surface by a converged light beam having a converging optical system for converging light from the light source on the substrate surface from a substantially vertical direction; and A moving means for moving the irradiation position of the light beam from the drawing means relative to the substrate placed on the stage in a horizontal direction; and the drawing apparatus provided on the substrate surface on which the stage is placed. In a focus adjustment method for a drawing apparatus , the image sensor includes a position detection unit that images a reference portion and detects a relative position in a horizontal direction between the substrate and the irradiation position of the light beam .
Reference setting for setting the observation light receiving surface at a position where the horizontal position is different from that on the substrate placed on the stage and the vertical position is substantially equal to the vertical position of the substrate surface placed on the stage Process,
A pre-focus adjustment step of observing an optical image of the light beam incident on the observation light-receiving surface and adjusting a focus position in the vertical direction of the convergent optical system so that the optical image is minimized;
A storage step of storing a vertical distance between the convergent optical system after the focus position adjustment and the observation light receiving surface as a reference distance;
Drawing is performed by irradiating the surface of the substrate placed on the stage with the light beam, and detecting a vertical distance between the surface of the substrate irradiated with the light beam and the converging optical system. wherein based on the reference distance, the focal position of the converging optical system and a rendering time focusing step of bringing the substrate surface and,
A focus adjustment method, characterized in that a focus position in a vertical direction of the position detection means is matched with a vertical position of the observation light receiving surface set in the reference setting step . In the drawing focus adjustment step, the focus position of the convergence optical system is adjusted to a position where the focus position set in the pre-adjustment step is changed by a distance corresponding to the difference between the detection result and the reference distance. The focus adjustment method according to claim 6 . 8. The focus adjustment method according to claim 6 , wherein a reference pattern is provided on the observation light receiving surface, the reference pattern is imaged by the position detection means, and a focal position of the position detection means is adjusted based on the result. The distance between the position detection unit and the observation light receiving surface when the focus position in the vertical direction of the position detection unit matches the vertical position of the observation light reception surface set in the reference setting step is stored. Item 9. The focus adjustment method according to any one of Items 6 to 8 . After performing drawing by the drawing unit on the first substrate, and performing drawing by the drawing unit on a second substrate different from the first substrate,
If the first substrate and the second substrate have the same thickness, the reference setting step, the pre-focus adjustment step, and the storage step for the second substrate are omitted, and the first substrate and the second substrate are omitted. While performing the drawing focus adjustment step using a reference distance,
If the first substrate and the second substrate have different thicknesses, the reference setting step, the pre-focus adjustment step, the storage step, and the drawing focus adjustment step are performed on the second substrate. focus adjustment method according to any of claims 6 to 9.

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