JP2000031028A - Exposure method and exposure apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance throughput of forming a type of pattern in multiple exposure by forming a plurality of patterns on a negative and setting the negative and a substrate to be exposed in the direction of scanning with the shortest processing time to scan and expose them. SOLUTION: In the case of forming an F pattern 21 such as a phase shift mask and an R pattern 24 such as a real element pattern on a reticle, considering a lighting condition such as σ and exposing volume different between the F pattern 21 and the R pattern 24, dimension and pattern interval of each of the pattern 21 and 24 on the negative, a shot arrangement and order of the exposure on the substrate to be exposed, and an exposure condition, etc., the total exposure time may be various in the direction of scanning. Accordingly, a plurality of scanning directions (e.g. x-direction and y-direction) are prepared, the total exposure time in selecting each of the scanning directions is derived from an experiment, a simulation or a calculation, and the scanning direction with the shortest exposure time among them is selected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an exposure method and an exposure apparatus, and more particularly to an exposure method and an exposure apparatus for exposing a fine circuit pattern onto a substrate to be exposed. Such an exposure method and an exposure apparatus are used, for example, in the manufacture of various devices such as semiconductor chips such as ICs and LSIs, display elements such as liquid crystal panels, detection elements such as magnetic heads, and imaging elements such as CCDs.

[0002]

2. Description of the Related Art At present, the mainstream of a projection exposure apparatus used for manufacturing devices such as ICs, LSIs and liquid crystal panels by using a photolithography technique uses an excimer laser as a light source. However, in a projection exposure apparatus using this excimer laser as a light source, a line width of 0.1
It is difficult to form a fine pattern of 5 μm or less.

In order to increase the resolution, it is theoretically necessary to increase the NA (numerical aperture) of the projection optical system or to reduce the wavelength of the exposure light. It is not easy to reduce the wavelength of the exposure light. That is, the depth of focus of the projection optical system is inversely proportional to the square of NA and proportional to the wavelength λ.
Is increased, the depth of focus becomes smaller, focusing becomes difficult, and productivity decreases. Also, the transmittance of most glass materials is extremely low in the far ultraviolet region, for example, λ = 248
Even fused silica used in nm (KrF excimer laser) drops to almost zero below λ = 193 nm. At present, a glass material that can be used practically in a region of an exposure wavelength λ = 150 nm or less corresponding to a fine pattern having a line width of 0.15 μm or less by ordinary exposure has not been realized.

Therefore, by performing double exposure of two-beam interference exposure and normal exposure on the substrate to be exposed, and by giving a multi-level exposure amount distribution to the substrate to be exposed at that time, higher resolution is achieved. Is disclosed in Japanese Patent Application No. 9-304232, "Exposure method and exposure apparatus".
(Hereinafter referred to as the prior application). According to this method, a pattern having a minimum line width of 0.10 μm can be formed using a projection exposure apparatus in which the exposure wavelength λ is 248 nm (KrF excimer laser) and the image side NA of the projection optical system is 0.6. .

[0005]

In the embodiment of the prior application, the two-beam interference exposure is performed by so-called coherent illumination using a phase shift mask (or reticle) having a line width of 0.1 μmL & S (line and space). afterwards,
Normal exposure (for example, exposure by partial coherent illumination) is performed using a mask (or reticle) on which an actual element pattern having a minimum line width of 0.1 μm is formed. As described above, in the double exposure method, two exposure steps with different exposure information are required for each shot in order to form one pattern. For this reason, there is a problem that the throughput becomes slow.

SUMMARY OF THE INVENTION It is an object of the present invention to improve the throughput of a multiple exposure method in which a plurality of types of patterns are overprinted on the same shot on a substrate to be exposed to form one type of pattern.

[0007]

In order to achieve the above object, according to the present invention, a part of a pattern image of an original is illuminated in a slit shape and projected onto the substrate to be exposed while synchronizing the original with the substrate. When exposing a pattern image of an original on the substrate to be exposed by scanning relative to the slit-shaped illumination, a plurality of patterns are formed on one original, and scanning exposure is performed using the original. In such a case, the processing time for each scanning direction is obtained, the scanning direction in which the processing time is the shortest is determined, and an original and a substrate to be exposed are set in the scanning direction to perform scanning exposure.

[0008]

In order to improve the throughput of a multiple exposure system in which a plurality of types of patterns are overprinted on the same shot on a substrate to be exposed to form one type of pattern, the present inventors use these types of patterns. By forming the mask on one mask (or reticle), the replacement time of the mask (or reticle) was shortened.

FIG. 2 shows a pattern (hereinafter referred to as an F pattern) 21 such as the phase shift mask and a pattern (hereinafter referred to as an R pattern) 22 such as an actual element pattern.
Are formed on a single reticle. The illumination conditions such as σ and the exposure amount are different between the F pattern and the R pattern. For example, when the F pattern 21 is 0.1 μm
When the R pattern 22 is a real element pattern having a minimum line width of 0.1 μm, for example, the optimum σ at the time of exposure of the F pattern 21 is 0.3 to
0.2, and the optimum σ at the time of exposure of the R pattern 22 is 0.1.
The exposure amount is 6 to 0.8, and the exposure amount is 2 to 3 times that of the F pattern.

When a single reticle has regions with different illumination conditions, a scanning exposure apparatus having only one illumination system usually uses a masking blade to illuminate an illumination region for each region where the reticle illumination conditions are the same. First, the F pattern 21 is exposed to all shots on the substrate to be exposed, and then the R pattern 22 is exposed by switching the illumination conditions and the illumination area. In this case, considering the dimensions and pattern intervals of each pattern on the original plate, the shot arrangement and exposure sequence on the substrate to be exposed, exposure conditions, and the like, there may be a difference in the overall exposure time depending on the scanning direction.

Therefore, in the present invention, a plurality of types of scanning directions (for example, the x direction and the y direction) are set, and the total exposure time when each scanning direction is adopted is obtained by an experiment, simulation, calculation, or the like. And the scanning direction in which the exposure time is the shortest. Thereby, the throughput of multiple exposure can be improved.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows the configuration of a scanning multiple exposure apparatus according to one embodiment of the present invention. In FIG. 1, reference numeral 1 denotes an exposure light source, here a pulse light source such as a KrF excimer laser. 2 is a half mirror, 3 and 4 are dimming filters, 5, 7
Is a half mirror, 6 and 8 are light quantity sensors, 9 and 10 are illumination optical systems, 11 is a half mirror, 12 is a beam splitter, 13 is a reticle, 14 is a projection lens, and 15 is a wafer.

FIG. 2 shows the configuration of the reticle 13 when a fine pattern having a minimum line width of 0.1 μm is transferred onto a wafer using the exposure apparatus shown in FIG. In FIG. 2, reference numeral 22 denotes a so-called Levenson type phase shift pattern (diffraction grating) (F pattern), and reference numeral 24 denotes an actual element pattern (R pattern) similar to the conventional element except that the minimum line width is as narrow as 0.1 μm. It is.

Returning to FIG. 1, the half mirror 2 divides the light beam emitted from the laser light source 1 into two light beams.
The light reflected by the half mirror enters the illumination system 9 via the neutral density filter 3 and the half mirror 5, and after the illumination system 9 controls illumination conditions (such as σ and the amount of exposure), the beam splitter 12 To illuminate the reticle 13. On the other hand, the light transmitted through the half mirror enters the illumination system 10 via the neutral density filter 4 and the half mirror 7, and after the illumination system 10 controls illumination conditions (such as σ and the amount of exposure), the beam splitter 12 And illuminates the reticle 13. In this case, by shifting the illumination area of the illumination system 9 and the illumination area of the illumination system 10 in the scanning direction, the distance between the F pattern 22 and the R pattern 24 projected on the wafer as the substrate to be exposed is adjusted on the reticle 13. The interval can be different.

The illumination system 9 includes a slit material for illuminating the first pattern 24 on the reticle 13 in a slit shape, and the slit material before the first pattern 24 reaches the exposure field and after passing through the exposure field. Shutters or movable blades for blocking the illumination of the illumination. Similarly, the illumination system 10 has a slit material for illuminating the second pattern 22 on the reticle 13 in a slit shape, and the slit material before the second pattern 22 reaches the exposure field and after passing through the exposure field. A shutter or a movable blade for shielding the illumination is provided. The illumination systems 9 and 10 are further provided with a diaphragm mechanism for setting σ. The neutral density filters 3 and 5 are for setting the exposure amounts of the first pattern 24 and the second pattern 22, respectively, and include, for example, ND filters with variable transmittance.

In the exposure apparatus shown in FIG. 1, a shot arrangement and an exposure order on a wafer as a substrate to be exposed, a pattern arrangement and dimensions on a reticle as an original, illumination conditions for each pattern, etc. The data is read from the storage device and stored in a storage unit (for example, a RAM) of a control device (not shown) that controls the operation of the exposure apparatus. Then, based on these information, y in FIG.
And the processing times t ₁ and t ₂ per wafer for scanning exposure in the x-direction, respectively, are determined from the following equations.

[0017]

(Equation 7)

Here, h ₁ is the width of each of the patterns 22 and 24, h ₂ is the length of each of the patterns 22 and 24, h ₃ is the distance between the patterns 22 and 24, and f (h ₁ ) is the F pattern 22. Time for scanning at a constant speed in the direction of x, r
₁ (h ₁ ) is the time for scanning the R pattern 24 in the x direction at a constant speed, j ₁ (h ₁ ) is the slower of f ₁ (h ₁ ) and r ₁ (h ₁ ), j
₂ (v ₂₎ is j ₁ if (h ₁₎ is _{f 1 (h 1) f 2} (v 1),
r ₂ (v ₂ ) when j ₁ (h ₁ ) is r ₁ (h ₁ ).

Further, the processing time t ₁ calculated by the above equation
Is compared with t ₂ , and the smaller scanning direction is determined as the scanning direction when exposure is performed using the reticle 13.

At the time of scanning exposure, the reticle 13 as an exposure original is set on the reticle stage in a direction corresponding to the determined scanning direction. Further, the scanning exposure is executed by loading the wafer 15 as the substrate to be exposed in the direction corresponding to the scanning direction determined similarly. In the present embodiment, two illumination systems are prepared, and the F pattern 22 and the R pattern 24 are independently illuminated. If the illumination conditions of the illumination systems 9 and 10 are set, the F pattern 22 and the R pattern 24 are simultaneously (one scan) on one shot on the wafer 15 and the shot adjacent thereto in any of the x and y directions. ) Scanning exposure is possible. When scanning in the x direction,
It is also possible to set the illumination conditions of the illumination systems 9 and 10 so that there is a difference in the scanning speed between the F pattern 22 and the R pattern 24. However, in this case, the gap between the F pattern 22 and the R pattern 24 needs to have a difference in a range that can be accelerated or decelerated to a constant scanning speed during scanning. Since there may be a difference in the scanning speed, the degree of freedom of the illumination conditions of the illumination systems 9 and 10 is increased, and the speed can be set to further increase the throughput.

In the above-described embodiment, a plurality of illumination systems are provided to simultaneously illuminate a plurality of reticle patterns under independent illumination conditions. However, the present invention employs a conventional scanning type exposure system having only one illumination system. It can also be applied to devices. In this case, the F pattern 22 and the R pattern 24 cannot be exposed simultaneously (in one scan), and are exposed separately as described above. However, the processing time for each of the x and y scanning directions is as follows. For example, it may be obtained by the following equation.

[0022]

(Equation 8) However, if the scanning speed can be deflected in the gap between the F pattern 22 and the R pattern 24, the F pattern 22 and the R pattern 2
In the arrangement direction of No. 4, exposure can be performed by one scan. In that case, it may be obtained by the following equation.

[0023]

(Equation 9)

Further, in the above description, when setting the reticle and loading the wafer, the reticle is placed in a direction corresponding to the determined scanning direction. However, a 90 ° rotating mechanism is provided on the wafer stage and the reticle stage. After setting, the orientation at the time of setting and loading may be fixed, and then rotated by 90 ° as needed.

[0025]

[Embodiment of Device Production Method] Next, an embodiment of a device production method using the above-described projection exposure apparatus or method will be described. FIG. 3 shows a micro device (a semiconductor chip such as an IC or an LSI, a liquid crystal panel, a CCD, a thin film magnetic head,
2 shows a flow of manufacturing a micromachine or the like. Step 1
In (Circuit Design), a device pattern is designed. Step 2 is a process for making a mask on the basis of the designed pattern. Step 3 (wafer manufacturing)
Then, a wafer is manufactured using a material such as silicon or glass. Step 4 (wafer process) is called a pre-process,
An actual circuit is formed on the wafer by lithography using the prepared mask and wafer. The next step 5 (assembly) is called a post-process, and is a process of forming a semiconductor chip using the wafer prepared in step 4, and includes processes such as an assembly process (dicing and bonding) and a packaging process (chip encapsulation). including. In step 6 (inspection), inspections such as an operation confirmation test and a durability test of the semiconductor device manufactured in step 5 are performed. Through these steps, a semiconductor device is completed and shipped (step 7).

FIG. 4 shows a detailed flow of the wafer process. Step 11 (oxidation) oxidizes the wafer's surface. Step 12 (CVD) forms an insulating film on the wafer surface. Step 13 (electrode formation) forms electrodes on the wafer by vapor deposition. In step 14 (ion implantation), ions are implanted into the wafer. Step 15
In (resist processing), a photosensitive agent is applied to the wafer. In step 16 (exposure), the circuit pattern of the mask is printed on the wafer by exposure using the above-described exposure apparatus or method. Step 17 (development) develops the exposed wafer. In step 18 (etching), portions other than the developed resist image are removed. In step 19 (resist stripping), unnecessary resist after etching is removed. By repeating these steps, multiple circuit patterns are formed on the wafer.

By using the production method of this embodiment, it is possible to manufacture a highly integrated device, which was conventionally difficult to manufacture, at low cost.

[0028]

As described above, according to the present invention, a plurality of patterns are arranged in a scanning direction on one original plate, and focus and exposure conditions are set for each pattern. Can be improved.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a scanning multiple exposure apparatus according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a reticle used in the apparatus of FIG.

FIG. 3 is a diagram showing a flow of manufacturing a micro device.

FIG. 4 is a diagram showing a detailed flow of a wafer process in FIG. 3;

[Explanation of symbols]

1: pulse light source, 2, 5, 7, 11: half mirror,
3,4: neutral density filter, 6,8: light intensity sensor, 9.1
0: illumination optical system, 12: beam splitter, 13: reticle, 14: projection lens, 15: wafer, 22: F pattern, 24: R pattern.

Claims (6)

[Claims] 1. A method according to claim 1, wherein a part of the pattern image of the original is illuminated in a slit shape and projected onto the substrate to be exposed while the original and the substrate to be exposed are synchronously scanned and relatively scanned with the slit illumination. In the method of exposing a pattern image of an original on an exposure substrate, a plurality of patterns are formed on one original, and the processing time for each scanning direction when performing scanning exposure using this original is determined to minimize the processing time. Determine the scanning direction of
An exposure method, comprising: setting the directions of an original plate and a substrate to be exposed in the determined scanning direction. 2. In a case where the first and second two patterns are formed on one original, a processing time t ₁ when scanning in the arrangement direction of the two patterns (x direction in FIG. 2).
And the processing time t ₂ when scanning is performed in a direction orthogonal thereto, and the dimensions in the arrangement direction of the two patterns are h ₁ and h
₁ , the interval is h _3, and the dimension in the direction orthogonal to the arrangement direction is h ₂ , Or Or 2. The exposure method according to claim 1, wherein the calculation is performed based on the following formula, and these are compared to determine a scanning direction in which the processing time is shortest. 3. An original and a substrate to be exposed are synchronously scanned relative to the projection optical system while projecting a part of the pattern image of the original onto a substrate to be exposed through a projection optical system in a slit shape. Scanning exposure apparatus for exposing a pattern image of an original onto the substrate to be exposed, wherein a plurality of patterns are formed on one original, and when scanning exposure is performed using the original, Means for calculating the processing time of
An exposure apparatus comprising: means for determining the scanning direction in which the calculated processing time is the shortest; and means for setting the directions of the original and the substrate to be exposed in the determined scanning direction. 4. The calculating means according to claim 1, wherein said one original is a first original.
And the second two patterns,
The processing time t ₁ when scanning in the direction in which the two patterns are arranged (the x direction in FIG. 2) and the processing time t ₂ when scanning in a direction orthogonal thereto are determined by the dimension in the direction in which the two patterns are arranged. h ₁ , h ₁ , the interval is h _3, and the dimension in the direction orthogonal to the arrangement direction is h ₂ , the following expression: Or Or 4. The exposure apparatus according to claim 3, wherein the calculation is performed based on: 5. A device manufacturing method, wherein a device is manufactured using the exposure method according to claim 1 or 2 or the exposure apparatus according to claim 3 or 4. 6. A device manufactured by the device manufacturing method according to claim 5.