JPH02272719A - Projecting aligner - Google Patents

Abstract

PURPOSE:To do more appropriate image surface correction by performing alignment while considering the positional detection output when a carriage mechanism is positioned in each of a plurality of places on the shifting path and the offset quantity peculiar in each position being memorized in advance. CONSTITUTION:The laser beams issued from a laser beam source 60 are scanned by a polygonal mirror 62, and a mask 66 and a wafer 68 are scanned through an optical system 67. The scattered lights form the alignment marks of the mask 66 and the wafer 68 are detected by a photoelectric transducer 70, and alignment slippage is sought in an operation processing circuit 71. When exposure is started initial setting is done, and after inputting the shift quantity of a carriage 72, the offset quantity at every slippage quantity measuring place is input. Next, a wafer 68 is carried in, and after performing alignment to the mask 66 at the center position of the carriage 72 the slippage quantity measurement is done at each slippage quantity measuring place. And after each slippage quantity is measured, the posture adjusting quantity of the carriage 72 is calculated considering the input offset quantity, and based on this the carriage 72 is shifted to do exposure.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a projection exposure apparatus used for manufacturing semiconductor circuit elements, etc., and in particular, the present invention relates to a projection exposure apparatus used for manufacturing semiconductor circuit elements, etc. The present invention relates to a scanning projection exposure apparatus that transfers an image of an original onto an exposed object by integrally scanning an exposed object with a projection optical system.

[Prior Art] A mask, which is an original, and a wafer, which is an object to be exposed, are moved together with respect to a fixed projection optical system, and a slit-shaped light is irradiated and scanned onto the mask through the projection optical system to form a mask. In mounting to expose a pattern on a wafer, a structure (hereinafter referred to as a carriage) that carries the mask and wafer and moves together is generally moved along the scanning direction y-axis and the perpendicular direction x
'Jth coordinate system and axis y' in the horizontal plane of the projection optical system
If the axis and the coordinate system of the X' axis, which is perpendicular to the axis, are misaligned in the rotational direction (angle θ), image plane distortion occurs, and the mask pattern is tilted by 2θ with respect to the xy axis coordinate system on the wafer. transcribed.

As a method for solving these drawbacks, there has conventionally been a method of adjusting transfer errors using an actual mask and wafer. In this method, the amount of deviation between the mask and the squares is measured at a plurality of locations, but positional alignment between the mask and the squares is performed at only one representative location, and only the amount of shift is measured and calculated at other locations. Therefore, the amount of deviation after alignment of the mask and wafer, that is, the amount of offset, is corrected only at the one representative location mentioned above, and at other locations where the amount of deviation is measured, even if there is an offset specific to that measurement location, it is ignored and measured. Then, the posture adjustment is executed by calculating the posture adjustment amount of the carriage mechanism.

[Problems to be Solved by the Invention] However, in this method of adjusting the attitude of the carriage mechanism using a mask for transferring actual semiconductor circuit elements and the like and a wafer to be transferred, the following reasons (1) and (2) are not met. Therefore, the offset value tends to vary depending on the location where the amount of deviation is measured within the plane of the sea urchin.

(1) Along with the formation of semiconductor circuit elements, wafers are repeatedly subjected to processes such as heat treatment and film forming, but due to the anisotropy of film forming, etc., the offset value of the deviation measurement output between the center and periphery of the wafer The trends may be different.

(2) In the exposure process for forming semiconductor circuits, it is necessary to apply photoresist to the wafer, but generally, the photoresist is coated by dropping the required amount of photoresist onto the center of the eight surfaces of the sea urchin and rotating the wafer at high speed. Spread radially and apply to a predetermined thickness. However, uneven coating of the photoresist tends to occur on minute irregularities such as alignment marks on the eight faces of the sea urchin. In particular, the tendency of coating unevenness is often different between the center and the periphery of the wafer.

Therefore, for these reasons, the tendency of the offset amount at the alignment point of the mask and wafer and the offset amount at other deviation measurement points is different, and the attitude adjustment function using the carriage mechanism does not function sufficiently. There is a drawback that image plane distortion may not be corrected even if the image is transferred to a wafer.

[Means for Solving the Problems] In order to achieve the above objects, the projection exposure apparatus of the present invention includes an illumination means for illuminating an original plate, and a projection apparatus for immersing a pattern of the original illuminated by the illumination means onto an exposed object. optical system and
A carriage mechanism that integrally scans the original and the exposed object with respect to the projection optical system by moving the original and the exposed object along a guide mechanism, and a projection optical system that adjusts the positional alignment of the original and the exposed object. The output of the position detecting means when the carriage mechanism is positioned at each of a plurality of locations on its movement path, and the unique offset amount at each position stored in advance are taken into account. The carriage mechanism is provided with a drive control means for driving and controlling the carriage mechanism while adjusting its posture in accordance with each position.

[Operation] In this configuration, the positional relationship between the original and the exposed object, the projection magnification, the scanning direction by the carriage mechanism, etc. change as the carriage mechanism moves.

The offset amount, that is, the amount of deviation from the alignment position between the original and the exposed object at each position on the movement path of the carriage mechanism also changes, but the offset amount specific to each position is determined in advance from the exposure results, etc., and the drive control stored in the means.

During exposure, the attitude of the carriage mechanism is adjusted in consideration of the offset amount unique to each position on the movement path of the carriage mechanism and the alignment state at each position, thereby performing more accurate exposure.

[Example] Hereinafter, the present invention will be explained in detail using the drawings.

FIG. 1 is a schematic configuration diagram of a reflection type projection exposure apparatus according to an embodiment of the present invention.
, polygon mirrors 62 are arranged.

Here, the laser light source 60, the condenser lens 61, and the polygon mirror 62 are shown rotated by 90 degrees around the Z axis, with the laser light source 60, condenser lens 61, and polygon mirror 62 arranged in a direction perpendicular to the drawing (X direction). The laser beam 2 is scanned in the X direction by the rotation of the polygon mirror 62.

Along the optical path of the laser beam 1 reflected by the polygon mirror 62, an f/θ characteristic lens 63, a dividing prism 76 for dividing the laser beam λ into two in the X direction, two half mirrors 64 (one is two objective lenses 65; a mask 66 having accurate alignment marks 101 (described later) at multiple locations; a reflective projection optical system 67; A wafer 68 is positioned having precise alignment marks 102 (described below).

The mask 65 and the wafer 68 are integrally carried by a carriage 72, and the carriage 72 is movable in the Y direction in the figure along a fluid bearing guide 78 by a carriage drive mechanism 77. When the circuit pattern of the mask 66 is exposed onto the wafer 68, the X
Illuminated by a slit-shaped light source (not shown) extending in the direction,
The carriage 72 is on duty.

The reflected light from the mask 66, the projection optical system 67, and the wafer 68 is reflected by two half mirrors 64, and two condenser lenses 69 and two photoelectric conversion elements 70 are arranged along the optical path of this anti-Qf light. . The output of the photoelectric conversion element 70 is applied to an arithmetic processing circuit 71, and the output of the photoelectric conversion element 70 is applied to an arithmetic processing circuit 71.
The relative positional relationship between the mask 66 and the wafer 68 is detected based on the output of valves 79 and 80
, and adjusts the inclination of the optical axis of the projection optical system 67 and the carriage scanning axis, and adjusts the magnification.

The arithmetic processing circuit 71 includes a central processing unit (CPU) 81, C which controls the operation of the arithmetic processing circuit 71.
A ROM 82 in which a program for the operation sequence of the PU 81 is stored, a RAM 83 in which arithmetic processing data is stored,
A mark measurement circuit 84 measures the distance between the marks on the mask 66 and the wafer 68 based on the output of the photoelectric conversion element 70, a carriage drive circuit 85 controls the carriage drive mechanism 77, and converts the arithmetic processing data from digital values to analog values. It is equipped with a drive data set circuit 86 for setting data, a control valve drive circuit 87 for driving seven control valves 80, a human output interface 88, and the like.

FIG. 2(a) shows alignment marks used on the mask 66 and wafer 68, and marks 101a and 101b.
, 101c, and 101d.
1 is formed on the mask 66, and the marks 102a, 102b
An alignment mark 102 is formed on the wafer 68. Actually, as shown in FIG. 3, similar alignment marks are formed at 12 locations.

In FIG. 3, 103 and 104 are alignment marks for visual inspection, one of which is formed on the mask 66 and the other on the wafer 68.

The measurement and adjustment efforts in the above configuration will be explained. Referring to FIG. 1, a laser beam l emitted from a laser light source 6o is scanned by a polygon mirror 62 and divided into two parts by a dividing prism 76 in the X direction. The two divided lights pass through a half mirror 64 and head towards a mask 66 and the like.

The alignment mark 101 of the mask 66 and the alignment mark 102 of the wafer 68 are scanned by the laser beam 1 through the optical system 67, and the scattered light from the marks 101 and 102 reaches the half mirror 64. The light is reflected in the direction of one photoelectric conversion element 70 . mask 6
When the alignment mark 1-01 of the mask 6 and the alignment mark 102 of the wafer 68 are overlapped as shown in FIG.
01 a.

Alignment mark 102 of wafer 68 between 101b
a exists, alignment mark 102b is located between alignment marks 101c and 101d, and laser beam l
is scanned in scanning direction A (X direction) from left to right. The photoelectric conversion element 70 detects pulsed light at the location where the laser beam intersects the alignment marks 101 and 102 as shown in FIG. 2(a), and outputs a waveform voltage as shown in FIG. 2(b). occurs. W,,W,,...1w5
is the interval of pulse signals, and the mark measuring circuit 84 of the arithmetic processing circuit 71 calculates this time interval W,, W2゜...
, W, the misalignment between the mask 66 and the wafer 68 is determined.

That is, if the deviation in the X direction in FIG. 2(a) is Δxo, and the deviation in the Y direction is Δy0, ΔX O= (W 1W
2 + W 4- W 5 ) / 4・・・・・・(
1) Δyo = (-Wl +W2 +W4-Ws) /
4...(2) It becomes. In the aligned state, W,=W2=W4=W5
Therefore, ΔXo and Δy0 are both;

However, the time intervals W1 to W are measured based on photoelectrically converted electrical signals, and even if ΔXO + Δy0 are both zero, the wafer-side alignment mark is actually aligned with the mask-side alignment mark. There may be cases where it is not sorted. This amount of deviation (offset)
remains as is when the mask pattern is transferred onto the wafer. Therefore, if alignment is performed with this amount of deviation taken into account from the beginning, the relative deviation between the two can be reduced to zero when the mask pattern is transferred onto the wafer.

However, the offset value when aligning the mask and wafer differs between the center and the periphery even within the same wafer, so this offset amount is subtracted from the measurement result for each location where the amount of deviation is measured. Calculate the amount of deviation between the actual mask and the quest.

In other words, the offset amount at a certain measurement point is (xo,
310), the actual amount of misalignment between the mask and the wafer is ΔX=ΔX0−XO (1')
Δy=Δyo −yo ・・・・・・・・・
...(2').

However, this offset amount needs to be known in advance.The mask and wafer are aligned, exposure is performed in that state, and the exposure result is measured as the actual deviation between the mask and wafer using a vernier, etc. and register it in RAM83. Alternatively, use manual alignment marks to align the wafer with respect to the mask, and then use a position detection means using photoelectric conversion to determine the deviation m.
(xo, Δyo) is registered in the RAM 83 as an offset amount.

When measuring the actual amount of deviation, as shown in Figure 3,
Measure the alignment marks 101 and 102 at two locations on the mask 66 and the wafer 68 at a distance of C1 in the X direction, and calculate the actual amount of misalignment between the mask and the wafer (1').
and (2'). Misalignment of mark on the right ffl
When Rl is (ΔXRIΔ'Jn+) and the left mark deviation m L I is (ΔX LI+ ΔyL1), the horizontal (X direction) magnification Mx is given by the following equation.

(3) Also, measure the two alignment marks 101 and 102 separated by a distance D1 in the Y direction, and calculate the misalignment amount R2 of the right mark by (ΔX R2 + Δyq2) and the misalignment of the left mark. When M L 2 is (ΔXL2+Δ3/L2), the vertical (Y direction) magnification My is expressed by the following formula (%) Next, the measurement of the angle θ formed with the scanning axes x and y will be described.

Two sets of alignment marks 101 in the X direction at the bottom of Fig. 3
, 102 are respectively located on the optical axes of the two objective lenses 65, and the laser beam l is scanned in the direction A in the figure.
The matching state is detected by the two photoelectric conversion elements 70 and the arithmetic processing circuit 71, and the left matching deviation amount ΔX L l
* Δ'j LI% right deviation amount ΔX Rl r Δ
yR1 is determined. Subsequently, the carriage 72 is moved by a distance 1111tD in the Y direction via the carriage drive mechanism 77 in response to a command from the arithmetic processing circuit 71, and the laser beam l is scanned in the direction B shown in the figure to create another alignment mark tot, 1.
Measure the alignment state of 02, and further subtract the offset amount to obtain the actual deviation amount Δx between the mask and the square. Obtain ΔyL2 and ΔxR2+ ΔyR2. Here, the deviation angle θX between the left and right alignment marks 101 and 102, which are separated by a distance C1 in the X direction between the mask 66 and the wafer 68, is approximately expressed by the following equation.

θx−(1/2C)・(ΔyLI−ΔyR1+Δy,,
2-ΔyR□)・・・・・・・・・(5) Also, distance 1 in the Y direction! The deviation angle θy between the upper and lower alignment marks 101 and 102, which are separated by t Dr r, is approximately expressed by the following equation.

θy-(1/20)・(AXR+-AXL+ AXR
2-ΔXL2) (6) These calculations are performed by the arithmetic processing circuit 71, and the control valve 79 is adjusted while the carriage is moving to reduce this deviation angle, thereby reducing the transfer distortion. Eliminate errors. The amount to be adjusted is θ = (θy - θX)・1/2 (a), where θX is the misalignment component and the optical axis and scanning axis are in the horizontal plane. These are components that are not parallel.

In this way, by determining and adjusting the angle θ to be adjusted at a plurality of locations, the transfer distortion error can be more accurately eliminated.

Next, the exposure procedure using the apparatus shown in FIG. 1 will be explained with reference to FIG.

When you start exposure, first make initial settings (step 4).
01), after inputting the movement amount of the carriage 72 (step 402), inputting the offset amount (Xo, 3'o) for each position where the amount of deviation is measured as described above (step 4).
03).

Next, the first wafer is carried in (step 404), aligned with the mask 66 at the center position of the carriage foot (step 4o5), and then the amount of deviation is measured at each measurement point (steps 406 to 406). 408).

After each amount of deviation is measured, the amount of attitude adjustment of the carriage 72 is calculated taking into account the offset amount manually applied in step 403. Based on this, the carriage 72 is moved while adjusting its attitude, and exposure is performed. (Step 410).

When the exposure of one wafer is completed in this way, the wafer is removed (step 411), and the next wafer is loaded (step 404).

Then, when the exposure for all 10 ts is completed (step 412), the exposure operation is ended.

[Effects of the Invention] Conventionally, alignment was performed taking into account the amount of offset only at the location where the positional alignment between the original and the exposed object was performed, and at other measurement locations, the amount of shift was regarded as image plane distortion. According to , more appropriate image plane correction can be performed by considering the offset amount for other measurement locations as well.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram of a reflection projection type exposure apparatus according to an embodiment of the present invention, and FIG. 2 is an explanatory diagram showing the relationship between the alignment marks on the mask and wafer and the output of the photoelectric conversion element in FIG. 1. , FIG. 3 is a top view of the mask and wafer superimposed,
FIG. 4 is a flowchart showing the operation of the apparatus using the present invention. 66; mask, 67: reflective projection optical system, 68: wafer, 70: photoelectric conversion element, 71: arithmetic processing circuit, 72: carriage mechanism, 77: carriage drive mechanism, 78: fluid bearing guide, 79.80: control Valve, 81: Central processing unit (CPU), : RAM, 84: Mark measurement circuit, : Carriage drive circuit, Two control valve drive circuit, 1.102: Alignment mark.

Claims (1)

[Claims] (1) An illumination means for illuminating the original; a projection optical system for projecting the pattern of the original illuminated by the illumination means onto an exposed object; A carriage mechanism that integrally scans the body relative to the projection optical system, a position detection means that detects the positional alignment state of the original and the exposed object via the projection optical system, and a carriage mechanism that moves the carriage mechanism along the movement path. Drive control that controls the carriage mechanism while adjusting its posture according to each position, taking into consideration the output of the position detection means when positioned at each of a plurality of positions and the unique offset amount at each position stored in advance. A projection exposure apparatus comprising: means.