JPH02174110A - Aligning method - Google Patents

Abstract

PURPOSE:To enhance an accuracy of a measuring operation by a method wherein a first composite pattern to a fourth composite pattern are formed and a die rotation by a setting discrepancy of a reticle is found from a measured value of a gap size of two opposite sides of the composite patterns. CONSTITUTION:Mask patterns whose sides are parallel to an X-direction or a Y-direction of a circuit pattern are formed near four corners of the circuit pattern; in a state that a shift of a wafer is limited to an X-direction and a Y-direction of a stepper, an exposure operation is executed to transcribe mutually different sides to a state that they are faced so as to be situated close to each other on the wafer; a plurality of composite patterns having two opposite sides where opposite sides have been transcribed onto the wafer are formed by changing a combination of the opposite sides. For example, gap sizes (a) to (d) of two opposite sides of a first composite pattern to a fourth composite pattern 48A to 48D are measured; a die rotation by a setting discrepancy of a reticle 3 is found by means of (a-b+c-d)/2; a setting position of the reticle 3 is adjusted in such a way that the die rotation becomes 0; after that, the exposure operation is executed. Thereby, an accuracy of a measuring operation can be enhanced.

Description

[Detailed Description of the Invention] [Summary] When photolithography exposure in semiconductor device manufacturing is performed using a stepper, this is done in order to eliminate die rotation due to misalignment of the reticle prior to exposure for circuit formation. With regard to the method of measuring die-rotation, the purpose is to improve the accuracy and automate the measurement, and if necessary, also to prevent the distortion of the projection lens from affecting the measurement. With the aim of ≧ Move the stepper to X
and under a condition limited to the Y direction, exposure is performed to transfer the mutually different sides to a state in which they are closely opposed to each other on the acid wafer, so that the opposed sides are transferred onto the acid wafer. A plurality of composite patterns each having two opposing sides are formed with different combinations of the opposing sides, and the distance dimension between the two opposing sides of the composite pattern is measured, and from the measured value, it is determined whether the set misalignment of the reticle is caused. Configure to obtain die rotation.

[Industrial application field]

The present invention relates to a photolithography exposure method used in the manufacture of semiconductor devices, and in particular, to a method for reducing die rotation due to misalignment of a reticle to zero prior to exposure for circuit formation when exposure is performed using a stepper. Concerning how to measure rotation.

The stepper uses a reticle provided with a circuit pattern for one semiconductor chip of a semiconductor device as an exposure mask, and moves the wafer, which is the object to be exposed, step by step in the XY force direction, repeating exposure at each step. This involves exposing circuits for multiple semiconductor chips onto a wafer.

During exposure, it is important to set the reticle so that the XY force direction of the circuit pattern on the reticle matches the XY direction of the wafer movement, that is, the XY force direction of the stepper. ) and adjust the reticle set so that the die rotation is 0.

[Conventional technology]

FIGS. 4(a) and 4(b) are plan views illustrating a conventional method for measuring the die rotation described above, in which (a) is a plan view of the main part of the reticle, and ■) is a wafer exposed for measurement. This is a plan view of the main parts.

In FIG. 4(a), the reticle 1 has a main pattern 12 on one side of the opposite edge of the circuit pattern 11 (an area that becomes a dicing line on the wafer) and a vernier pattern 13 on the other side. It is a provision.

The position of the vernier pattern 13 is such that when the exposures before and after the wafer is moved one step in the opposite direction of the opposing edges are repeated, the transfer pattern of the vernier pattern 13 is the same as that of the main pattern 12.
are selected to follow the transfer pattern.

Measurement of die rotation when this reticle 1 is set on a stepper is performed as follows.

That is, in FIG. 4, etc., the wafer 2 is subjected to the first exposure and the second exposure, which is shifted by one step from there, and the circuit pattern 11, the main pattern 12, and the vernier pattern are formed on the wafer 2. 2&l circuit pattern 21, main scale pattern 22 and vernier scale pattern 23 onto which 13 has been transferred
form.

Then, the vernier pattern 23 will be aligned with the main pattern 22 between the two circuit patterns 21.

Therefore, by observing the positional deviation state between the main scale pattern 22 and the vernier scale pattern 23, the desired rotation can be measured.

Then, based on the measurement results, the guirotation is 0.
After adjusting the reticle set so that it is, exposure for circuit formation is performed.

Therefore, the present invention provides a method for measuring gyrorotation, which is performed in order to eliminate gyrorotation due to misalignment of a reticle prior to exposure for circuit formation when photolithography exposure in semiconductor device manufacturing is performed using a stepper. The object of the present invention is to improve the accuracy and automate the measurement, and if necessary, to prevent the measurement from being affected by dust silane of the projection lens.

[Problem to be solved by the invention]

However, in the above-mentioned measurement method, the positional deviation between the main scale pattern 22 and the vernier pattern 23 must be visually observed by a person, which makes it difficult to sufficiently improve measurement accuracy due to individual differences. Even if we talk about automating observation to eliminate this individual difference, it is difficult to automate it.

Further, if there is distortion in the projection lens, there is a problem in that the measurement error increases due to the distortion.

[Means to solve the problem]

Referring to FIGS. 1(a) and 1(b) for explaining the embodiment, the above purpose is to reduce the distance between each of the two adjacent corners of the circuit pattern 31 on the reticle 3 when considering the distortion of the projection lens. X or Y of the circuit pattern 31
The first side 32 and the second side that match one straight line 36 parallel to the direction
A second straight line 37 located near the side 33 and the other two corners of the circuit pattern 3 and parallel to the straight line 36
A mark pattern 32A to 35A having a third side 34 and a fourth side 35 with the side 33 as the third side is provided on the reticle 3, and the reticle 3 is set on a stepper and the mark pattern is placed on the wafer 4. 1 exposure and the wafer 4 is moved in the X and Y directions of the stepper from the first exposure position, the third side 34
under the condition that the wafer 4 is moved from the position of the second exposure in either the X or Y direction of the stepper, Under the third exposure in which the fourth side 35 is opposed to the second side 33 in the first exposure, and the cough wafer 4 is moved mainly in one direction of the X and Y directions of the stepper from the first exposure position, A fourth exposure is performed in which the first side 32 and the second side 33 are close to and opposite to the fourth side 35 and the third side 34 in the first exposure, respectively, and the opposite first side is placed on the cough wafer 4. The first composite pattern 48A has two opposite sides 42.44a to which the opposite sides 32 and 34 are transferred, and two opposite sides 43.45a to which the opposed second sides 33 and fourth sides 35 are transferred. A second composite pattern 48B, a third composite pattern 48C having two opposing sides 44.43a to which the opposing third side 34 and second side 33 are transferred, and the opposing fourth side 3
5 and a fourth composite pattern 48D having two opposite sides 45.42a to which the first side 32 is transferred, and first, second, third and fourth composite patterns 48A to 48D.
According to the measuring method of the present invention, the distance dimensions a, b, c, and d between the two opposing sides of the reticle 3 are measured, and the girotation due to the setting deviation of the reticle 3 is determined by (a − b + c − d ) / 2. If the distortion of the projection lens is not considered, the fourth exposure can be omitted and the gyrotation can be changed to (a).
-b)/2 is solved by the measuring method of the present invention.

[For production]

The difference between the dimensions a and b is the difference between the X or Y direction of the circuit pattern on the reticle 3 and the X or Y direction of the stepper in the interval between the first and second composite patterns 48A and 48B.
The difference between the above-mentioned dimensions C and d is the value obtained by adding the size of the deviation that occurs in the same direction as the above-mentioned deviation direction due to the projection lens distortion to the size of the deviation from the above-mentioned direction. Indicates the magnitude of the deviation caused by the distortion of the projection lens in the same direction as the above deviation direction in the interval between the fourth composite patterns 48C and 48D, and the interval between the third and fourth composite patterns 48C and 48D. teeth,
The distance is approximately equal to the distance between the first and second composite patterns 48A and 48B.

From this, the die rotation when there is no distortion in the projection lens is expressed as (a-b)/2, and when there is distortion in the projection lens, its influence is corrected (a-b+cd). /2 can indicate accurate die rotation.

However, since the dimensions a to d are the distances between the two opposing sides, they cannot be automatically measured with high precision using an automatic pattern width measurement device that is generally used for high precision measurement of the width of fine patterns. is possible.

This makes it possible to improve the precision and automate die rotation measurement, even when there is distortion in the projection lens. Along with this, the die rotation can also be adjusted with high precision.

〔Example〕

Embodiments of the present invention will be described below with reference to FIGS. 1 to 3. 1(a)■) is a plan view for explaining the first embodiment, FIG. 2 is a plan view for explaining the second embodiment, and FIG. 3(a)
) (b) is a plan view illustrating the third embodiment.

The first embodiment is for taking into account the distortion of the projection lens. Fig. 1(a) is a plan view of the main part of the reticle, and Fig. 1(b) is a plan view of the main part of the reticle. FIG.

In FIG. 1(a), the reticle 3 has a line located near two adjacent corners of the circuit pattern 31 parallel to the X or Y direction of the circuit pattern 31 (in this case, the Y direction which is the vertical direction in the drawing). The first side 32 and the second side 33 coincide with the straight line 36, and the second side 33 side coincides with the straight line 37 located near the other two corners of the circuit pattern 31 and parallel to the straight line 636. Third side 34 and fourth side 35 which are three sides
A first mark pattern 32A having a first side 32 and a second mark pattern 3 having a second side 33.
3A, a third mark pattern 34A having a third side 34, and a fourth mark pattern 35A having a fourth side 35 are provided.

These mark patterns 32A to 35A are placed in the SR area that becomes the dicing line on the wafer, and this area is used as the resist removal area (transparent area if the resist on the wafer is positive), so that no resist remains. It is formed in the area.

As described later, these sides 32 to 35 are used to measure die rotation, and since this measurement measures the deviation in the Y direction, a similar measurement can be made in the X direction as well. To make this possible, the individual mark patterns 32A to 35A are key-shaped (L-shaped) so as to sandwich the corners of the circuit pattern 31.

The die rotation of the gap where the reticle 3 is set on the stepper is measured as follows.

That is, in FIG. 1(b), first exposure is performed on the wafer 4. Next, the wafer 4 is moved from the first exposure position in the X and Y directions of the stepper, and the third side 34 is moved onto the first mark pattern 32A in the first exposure so as to be close to and opposite to the first side 32. Then, the wafer 4 is moved from the second exposure position in either the X or Y direction of the stepper (in this case, the Y direction), and the fourth side 35 is exposed in the first exposure position. A third exposure is performed by moving the wafer 4 onto the second mark pattern 33A and facing the second side 33 of the pattern, and then moving the wafer 4 from the first exposure position mainly in one direction of the X and Y directions of the stepper (in this case, the X direction). The first side 32 and the second side 33 are moved onto the fourth mark pattern 35D and the third mark pattern 34C in the first exposure, respectively, and the fourth side 35
Then, a fourth exposure is performed close to and facing the third side 34.

What is important here is that when moving from the second exposure to the third exposure, the wafer 4 must be moved accurately in either the X or Y direction of the stepper;
Sides 32 to 35 facing each side 32 to 35 during exposure
is positioned on the mark patterns 32A to 35A in the first exposure.

Therefore, as long as this condition is ensured, the moving path of the wafer 4 may be arbitrary.

Then, the circuit pattern 31 is placed on the wafer 4 along with the circuit pattern 41 on which the circuit pattern 31 is transferred, and the first side 32 is placed on the opposite side 32.
and a first composite pattern 48A having two opposing sides 42 and 44a to which the third side 34 is transferred, and the second opposing side 48A.
Two opposing sides 43 and 4 to which side 33 and fourth side 35 have been transferred
5a, and two opposing sides 44 to which the opposing third side 34 and second side 33 are transferred.
and 43a, and the opposite side 2 to which the fourth side 35 and the first side 32 of the couplet are transferred.
A fourth composite pattern 48D having sides 45 and 42a is formed.

Next, the two opposing sides 42 and 4 of the first composite pattern 48^
4a and the opposing 2 of the second composite pattern 488
If the distance between the sides 43 and 45a is determined, the third composite pattern 4
The distance C between the two opposing sides 44 and 43a of 8C and the distance d between the two opposing sides 45 and 42a of the fourth composite pattern 480 are measured. This measurement can be performed automatically, extremely easily, and with high accuracy using the automatic pattern width measurement device described above.

Then, the desired rotation is (a-b+c
-d)/2.

Note that (a-b+c-d) obtained here is the deviation in the Y direction in the girotation, but the sides in the X direction of the key-shaped mark patterns 32A to 35A are the sides 32 to 35.
If it can be likened to , then the girotation can be determined by determining the shift in the X direction in the same manner as described above. The girotation measurement may be performed in either the X or Y direction.

After this, from the above measurement results, (a-b+cd)/2=
After adjusting the center of the reticle 3 so that 0 or (a-b+c-d)=0 and setting the gyrotation to 0, exposure for circuit formation is performed.

The second embodiment is a method in which the amount of distortion in the projection lens is negligibly small, and the consideration of the distortion in the projection lens in the first embodiment is omitted. FIG. 2, which explains this, is a plan view corresponding to the previous FIG. 1, etc.

If the projection lens has no distortion, the relationship c=d necessarily holds between the dimensions C and d in the first embodiment.

For this reason, in the second embodiment, the fourth exposure of the first embodiment is omitted, and the composite pattern formed on the wafer 4 is
Only the first composite pattern 48A and the second composite pattern 48B are used. It is sufficient to measure dimensions only by dimensions a and b, and the desired girotation is determined by (a-b)/2.

The third embodiment considers the distortion of the projection lens as in the first embodiment, but unlike the first embodiment, the region of the reticle on the wafer that will become the dicing line is set as the resist remaining region. It is. (a) and 2) in Figure 3 to explain this are the same as (a) and 2) in Figure 1 above.
FIG. 2 is a plan view corresponding to FIG. 1, and the same reference numerals as in FIG.

In FIG. 3(a), the reticle 3 includes a first mark pattern 32A having a first side 32 and a second mark pattern 33A having a second side 33, as in the first embodiment.
, a third mark pattern 34A having a third side 34 and a fourth mark pattern 35A having a fourth side 35 are provided, but since the area that will become the dicing line on the wafer is the resist remaining area, these The mark patterns 32A to 35A are formed in the resist removal area.

Girotation measurement when this reticle 3 is set on a stepper is carried out in the same manner as in the first embodiment, with the following exceptions in order to be able to measure the dimensions a - d.

The difference is that in the second, third and fourth exposures, the sides 32 to 35 opposite to the sides 32 to 35 in the first exposure are changed to the mark pattern 32A in the first exposure in FIG. 3(b). ~35A in close proximity on the outside, the first,
Desired two opposing sides (42 and 44a, 43 and 45a,
44 and 43a3, and 45 and 42a) are formed.

Although the explanation will be omitted, this third embodiment can be applied in the same way as the first embodiment was applied to form the second embodiment.

Further, the key point of the present invention is to form the above-mentioned predetermined composite pattern on the wafer, and if the composite pattern can be formed, the shape of the above-mentioned mark pattern on the reticle is limited to the embodiment. It is not something that will be done.

〔Effect of the invention〕

As explained above, according to the configuration of the present invention, when photolithography exposure in semiconductor device manufacturing is performed using a stepper, this is performed in order to reduce guirotation due to misalignment of the reticle prior to exposure for circuit formation. In a method for measuring die rotation, it is possible to improve the accuracy and automate the measurement, and if necessary, it is also possible to prevent the distortion of the projection lens from affecting the measurement. effective.

[Brief explanation of the drawing]

Figures 1 (a) and (c) are plan views for explaining the first embodiment, Figure 2 is a plan view for explaining the second embodiment, and Figure 3 (a))
is a plan view for explaining the third embodiment, and FIG. 4(a) (2) is a plan view for explaining the conventional example. In the figure, 1, 3 is a reticle, 11.31 is a circuit pattern, 32 to 35 are first to fourth sides, 32A to 35A are mark patterns, 2.4 is a wafer, 21.41 is a transferred circuit pattern, Floor plan diagram 2 to explain Part Z East Crime Example 8! A plan view explaining the conventional method

Claims (2)

[Claims] (1) When performing photolithography exposure in semiconductor device manufacturing using a stepper, the circuit pattern (31) is located near each of two adjacent corners of the circuit pattern (31) on the reticle (3) in the X or Y direction of the circuit pattern (31). The first side (
32) and the second side (33), and the circuit pattern (31)
The second side (33) side is located near each of the other two corners and coincides with a straight line (37) parallel to the straight line (36).
A mark pattern (32A to 35A) having a third side (34) and a fourth side (35) is provided on the reticle, and the reticle (3) is set on a stepper and applied to the wafer (4). A first exposure is performed, and the wafer (4) is subjected to a first exposure.
While moving from the exposure position in the X and Y directions of the stepper, the third side (34) is replaced with the first side (34) in the first exposure.
2) and a second exposure that was closely opposed to the wafer (4);
) is moved from the second exposure position in either the X or Y direction of the stepper, and the fourth side (35) is opposed to the second side (33) in the first exposure. exposure, and the wafer (4) is moved from the first exposure position to the X of the stepper.
The first side (32) and the second side (33) are placed close to the fourth side (35) and the third side (34) in the first exposure, respectively, under the state of moving mainly in one direction in the Y direction. and a fourth exposure facing the wafer (4), and exposing the facing first side (32) on the wafer (4).
and two opposite sides (42, 44) to which the third side (34) has been transferred.
a), and a second composite pattern (48A) having two opposing sides (43, 45a) onto which the opposing second side (33) and fourth side (35) are transferred.
48B), a third composite pattern (48C) having two opposing sides (44, 43a) to which the opposing third side (34) and second side (33) are transferred, and the opposing fourth side. (35) and the two opposite sides (4) to which the first side (32) has been transferred.
5, 42a) and a fourth composite pattern (48D) having the first, second, third and fourth composite patterns (48A to 48
Measure the distances a, b, c, and d between the two opposing sides of D), determine the die rotation due to missetting of the reticle (3) as (a-b+c-d)/2, and calculate the die rotation. The reticle (3
), and then performs exposure for circuit formation. (2) The exposure method according to claim 1, wherein the fourth exposure is omitted and the die rotation is determined by (ab)/2.