JPH0758682B2 - Exposure method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Outline] When performing exposure for photolithography in manufacturing a semiconductor device with a stepper, the die rotation is performed prior to the exposure for forming a circuit in order to eliminate the die rotation due to the reticle set deviation. In order to improve the accuracy and automation of the measurement, it is also necessary to prevent the measurement from being affected by the distortion of the projection lens. A mark pattern having sides parallel to one direction of the X or Y direction of the circuit pattern is provided near the four corners of the circuit pattern above, and the reticle is set on a stepper and the wafer is moved with respect to the wafer. Under the condition that the stepper is limited to the X and Y directions, the mutually different sides are closely opposed to each other on the wafer. The wafer is exposed to light in a state of being transferred, and a plurality of composite patterns having two opposite sides to which the opposed sides are transferred are formed on the wafer with different combinations of the opposed sides, and the composite is formed. The distance dimension between the two opposite sides of the pattern is measured, and the die rotation due to the set deviation of the reticle is obtained from the measured value.

[Industrial application field]

The present invention relates to an exposure method of photolithography in manufacturing a semiconductor device, and in particular, when the exposure is performed by a stepper, the die rotation is performed prior to the exposure for forming a circuit in order to reduce the die rotation due to the reticle set deviation. Regarding measurement method of rotation.

The stepper uses a reticle provided with a circuit pattern for one semiconductor chip of a semiconductor device as an exposure mask, moves a wafer as an exposed object in steps in the XY directions, and repeats exposure for each step. The circuit for exposing a plurality of semiconductor chips is exposed on the wafer.

In the exposure, it is important to set the reticle so that the XY direction of the circuit pattern on the reticle matches the XY direction of the wafer movement, that is, the XY direction of the stepper, and the deviation between them (called die rotation). ), And adjust the reticle set so that the die rotation becomes zero.

[Conventional technology]

FIGS. 4 (a) and 4 (b) are plan views for explaining a conventional example of the method for measuring the die rotation described above, FIG. 4 (a) is a plan view of a main part of the reticle, and FIG. 4 (b) is an exposure for measurement. It is a principal part top view of a wafer.

In FIG. 4A, the reticle 1 has a circuit pattern.
A main scale pattern 12 is provided on one of the outer sides of the facing edge of 11 (a region which becomes a dicing line on the wafer), and a vernier pattern 13 is provided on the other side. The position of the vernier scale pattern 13 is selected so that the transfer pattern of the vernier scale pattern 13 is aligned with the transfer pattern of the main scale pattern 12 when exposure is repeated before and after the wafer is moved one step in the facing direction of the facing edge. ing.

The die rotation when the reticle 1 is set on the stepper is measured as follows.

That is, in FIG.
Two sets of a circuit pattern 21, a main scale pattern, in which the circuit pattern 11, the main scale pattern 12 and the sub-scale pattern 13 are transferred onto the wafer 2 by performing the exposure and the second exposure which is moved by one step 22 and vernier scale pattern 23 are formed.

Then, between the two circuit patterns 21, the vernier scale pattern 23 comes along the main scale pattern 22.

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

Then, based on the measurement result, the die rotation is 0.
The reticle set is adjusted so that

[Problems to be Solved by the Invention]

However, in the above-described measurement method, since the observation of the positional deviation state of the main scale pattern 22 and the vernier scale pattern 23 is a target observation by a person, it is difficult to sufficiently improve the measurement accuracy due to individual differences, and , It is difficult to automate the observation to eliminate this individual difference.

Further, when the projection lens has distortion, it has a problem that the measurement error increases due to the distortion.

Therefore, the present invention provides a method for measuring the die rotation, which is performed in order to reduce the die rotation due to the reticle set deviation to 0 before the exposure for circuit formation when the exposure for the photolithography in the semiconductor device manufacturing is performed by the stepper, It is an object of the present invention to improve the accuracy of the measurement and enable automation, and further to prevent the distortion of the projection lens from affecting the measurement.

[Means for Solving the Problems]

With reference to FIGS. 1 (a) and 1 (b) for explaining the embodiment, the above-mentioned object is to position the circuit pattern 31 on the reticle 3 near two adjacent corners when the distortion of the projection lens is taken into consideration. Then, the first side 32 and the second side 33, which coincide with one straight line 36 parallel to the X or Y direction of the circuit pattern 31, and the straight line 36 respectively located near the other two corners of the circuit pattern 3. A mark pattern 32 having a third side 34 and a fourth side 35, which coincide with a straight line 37 parallel to the second side 33 and whose second side 33 is the third side.
A to 35A are provided on the reticle, the reticle 3 is set on the stepper, and the wafer 4 is subjected to the first exposure and the wafer 4 is moved from the position of the first exposure in the X and Y directions of the stepper. Under the third side 34
The second side of the first exposure side close to the first side 32 in the first exposure.
Under the condition of exposure and movement of the wafer 4 from the position of the second exposure in one of the X and Y directions of the stepper,
The third side with the fourth side 35 facing the second side 33 in the first exposure
Under the exposure and the state in which the wafer 4 is moved from the position of the first exposure in the X and Y directions of the stepper mainly in one direction,
The first side 32 and the second side 33 are respectively the fourth side in the first exposure.
The third exposure is performed by performing a fourth exposure in close proximity to the side 35 and the third side 34, and the first side 32 and the third side 34 which are opposed to each other are formed on the wafer 4.
And a second combined pattern 48B having opposite two sides 43, 45a to which the opposite second side 33 and fourth side 35 are transferred.
And the third combined pattern 48C having the opposite two sides 44 and 43a to which the opposed third side 34 and the second side 33 are transferred, and the opposed fourth side 35 and the first side 32 are transferred. Two opposite sides
A fourth combined pattern 48D having 45, 42a is formed, and the distances a, b, c, and d between the opposing two sides of the first, second, third, and fourth combined patterns 48A to 48D are measured. The die rotation caused by the set displacement of the reticle 3 (a
-B + c-d) / 2, which is solved by the measuring method of the present invention, and when the distortion of the projection lens is not taken into consideration, the fourth exposure is omitted and the die rotation is (a- b) / 2 solved by the measuring method of the invention.

[Action]

The difference between the dimensions a and b is the magnitude of the deviation 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 combined patterns 48A and 48B. , A value obtained by adding the magnitude of the deviation generated in the same direction as the deviation direction due to the distortion of the projection lens, and the difference between the dimensions c and d is the distance between the third and fourth combined patterns 48C and 48D. , Shows the value of the magnitude of the shift generated in the same direction as the shift direction due to the distortion of the projection lens. The distance between the third and fourth combined patterns 48C and 48D is substantially equal to the distance between the first and second combined patterns 48A and 48B.

From this, the dirotation when the projection lens has no distortion is represented by (ab) / 2, and when the projection lens has distortion, the effect is corrected (ab + cd) / 2. The exact dirotation can be shown by.

Of course, since the dimensions a to d are the intervals between the two opposite sides, the pattern width dimension automatic measuring instrument generally used for the high precision measurement of the width dimension of the fine pattern should be used to measure the dimension automatically. Is possible.

From this, it is possible to improve the accuracy and automate the die rotation measurement, including the case where the projection lens has distortion. Along with this, adjustment of die rotation can be performed with high accuracy.

〔Example〕

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

The first embodiment is a case in which the distortion of the projection lens is taken into consideration. (A) of FIG. 1 for explaining the distortion is a plan view of a main part of the reticle, and (b) is an exposed wafer for die rotation measurement. FIG.

In FIG. 1A, the reticle 3 has a circuit pattern.
The circuit pattern 31 is located near each of the two adjacent corners of 31.
The first side 32 and the second side 33 that match a straight line 36 parallel to the X or Y direction (here, the Y direction that is the vertical direction in the drawing) of
And a third side 34 and a fourth side 35 which are located near the other two corners of the circuit pattern 31 and which match one straight line 37 parallel to the straight line 36 and whose second side 33 is the third side. So the first side
A first mark pattern 32A having 32, a second mark pattern 33A having a second side 33, a third mark pattern 34A having a third side 34, and a fourth mark pattern 3 having a fourth side 35.
5A is provided.

These mark patterns 32A to 35A are arranged in a region that will be a dicing line on the wafer, and since that region is a resist removal region (a light-transmitting region when the resist on the wafer is a positive type), it is a resist remaining region. Has been formed.

Then, these sides 32 to 35 are used for the measurement of die rotation as described later, and since the measurement is for measuring the deviation in the Y direction, similar measurement can be performed in the X direction. As can be seen, the individual mark patterns 32A to 35A are formed in a key shape (L-shape) with the corners of the circuit pattern 31 sandwiched therebetween.

The die rotation when the reticle 3 is set on the stepper is measured as follows.

That is, in FIG. 1B, the wafer 4 is first exposed to light. Then, the wafer 4 is moved in the X and Y directions of the stepper from the position of the first exposure, the third side 34 is moved onto the first mark pattern 32A in the first exposure, and the third side 34 is brought close to and opposed to the first side 32. Second exposure, followed by
Move the wafer 4 from the second exposure position to the X or Y of the stepper.
In any one of the directions (here, the Y direction), the fourth side 35 is moved onto the second mark pattern 33A in the first exposure and the third exposure facing the second side 33 is performed. ,
The wafer 4 is moved from the position of the first exposure to a state in which it is moved mainly in one direction (here, the X direction) in the X and Y directions of the stepper, and the first side 32 and the second side 33 are respectively moved to the first side in the first exposure. The fourth mark pattern 35D and the third mark pattern 34C are moved to the fourth mark pattern 35D and the fourth side 35 and the third side 34 of the fourth mark pattern 35D, and the fourth exposure is performed so as to be opposed to the fourth mark 35D.

What is important here is that the wafer 4 is accurately moved in one of the X and Y directions of the stepper when moving from the second exposure to the third exposure.
That is, the sides 32 to 35 facing the respective sides 32 to 35 in the exposure are positioned on the mark patterns 32A to 35A in the first exposure. Therefore, if that state is secured, the movement path of the wafer 4 may be appropriate.

Then, on the wafer 4, a first combined pattern 48A having a circuit pattern 41 to which the circuit pattern 31 is transferred and two opposite sides 42 and 44a to which the above-described first side 32 and third side 34 are transferred, respectively. , The opposite second side 33 and fourth side 3
The second combined pattern 48B having the opposite two sides 43 and 45a to which 5 is transferred, and the third combined pattern 4 having the opposite two sides 44 and 43a to which the above-mentioned opposed third side 34 and second side 33 are transferred.
8C and a fourth combined pattern 48D having opposing two sides 45 and 42a to which the opposed fourth side 35 and first side 32 are transferred are formed.

Next, the distance a between the two opposing sides 42 and 44a of the first combined pattern 48A and the two opposing sides 43 and 45a of the second combined pattern 48B.
Of the third synthetic pattern 48C, the distance c of the two opposing sides 44 and 43a of the third synthetic pattern 48C, and the two opposing sides of the fourth synthetic pattern 48D.
Measure the spacing dimension d of 45 and 42a. This measurement can be automatically and extremely easily and highly accurately performed by the pattern width dimension automatic measuring device described above.

Then, the desired dirotation is (ab + c-
d) / 2.

The (a−b + c−d) obtained here is the deviation in the Y direction in the die rotation, but if the sides in the X direction of the key-shaped mark patterns 32A to 35A can be regarded as the sides 32 to 35, In the same manner as described above, die rotation can be obtained by obtaining the deviation in the X direction. And the measurement of die rotation is X or Y.
Any direction may be used.

After this, from the above measurement results, (ab + cd) / 2 =
The reticle 3 is adjusted so that 0 or (ab + c−d) = 0 and the die rotation is set to 0, and then exposure for circuit formation is performed.

The second embodiment is a method in which the distortion of the projection lens is negligibly small, and the consideration of the distortion of the projection lens in the first embodiment is omitted. FIG. 2 for explaining it is a plan view corresponding to FIG. 1 (b).

When the projection lens has no distortion, the relationship of c = d is inevitably established between the dimensions c and d in the first embodiment.

From this, 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 combined pattern 48A and the second combined pattern 48B are shown. The dimension measurement is required only for the dimensions a and b, and the desired die rotation is determined by (ab) / 2.

The third embodiment considers the distortion of the projection lens as in the first embodiment, but is different from the first embodiment in that the region to be the dicing line on the wafer of the reticle is the resist remaining region. . FIGS. 3 (a) and 3 (b) for explaining it are plan views corresponding to FIGS. 1 (a) and 1 (b), and the reference numerals of the same functional objects as those in FIG. It is common to FIG.

In FIG. 3A, the reticle 3 has a first mark pattern 32 having a first side 32 as in the case of the first embodiment.
A, second mark pattern 33A having second side 33, third side 34
Although the third mark pattern 34A having the above and the fourth mark pattern 35A having the fourth side 35 are provided, since the region which becomes the dicing line on the wafer is the resist remaining region, these mark patterns 32A to 35A is formed in the resist removal area.

The die rotation when the reticle 3 is set on the stepper is measured by the same method as in the first embodiment except for the following points so that the dimensions a to d can be measured.

The difference is that in FIG. 3B, the sides 32 to 35 facing the respective sides 32 to 35 in the first exposure are marked with the mark pattern 32A in the first exposure during the second, third and fourth exposures. ~ 3
The two opposite sides (42 and 44) desired to the first, second, third and fourth combined patterns 48A to 48D are arranged so as to be close to each other outside 5A.
a, 43 and 45a, 44 and 43a3, and 45 and 42a) are formed.

Although not described, the third embodiment can be applied in the same way as the second embodiment by applying the first embodiment.

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

〔The invention's effect〕

As described above, according to the configuration of the present invention, when the exposure of the photolithography in the manufacturing of the semiconductor device is performed by the stepper, it is performed in order to eliminate the die rotation due to the reticle set deviation prior to the exposure for forming the circuit. In the method for measuring the die rotation, it is possible to improve the accuracy of the measurement and to automate the measurement, and if necessary, to prevent the distortion of the projection lens from affecting the measurement.

[Brief description of drawings]

1 (a) and (b) are plan views for explaining the first embodiment, FIG. 2 is a plan view for explaining the second embodiment, and FIGS. 3 (a) and (b) are for explaining the third embodiment. 4A and 4B are plan views for explaining a conventional example. In the figure, 1 and 3 are reticles, 11 and 31 are circuit patterns, 32 to 35 are first to fourth sides, 32A to 35A are mark patterns, 2 and 4 are wafers, 21 and 41 are transferred circuit patterns, 42-45, 42a
.About.45a are transferred sides, 48A to 48D are first to fourth composite patterns, and a, b, c, d are spacing dimensions.

Claims (2)

[Claims] 1. When the exposure of photolithography in the manufacture of a semiconductor device is performed by a stepper, the X or the X of the circuit pattern (31) is located near each of two adjacent corners of the circuit pattern (31) on the reticle (3). The first side (32) and the second side (33) that match one straight line (36) parallel to the Y direction, and the straight line (36) located near each of the other two corners of the circuit pattern (31). Mark pattern (32) having a third side (34) and a fourth side (35) that match a straight line (37) parallel to
A to 35A) are provided on the reticle, and the reticle (3) is set on the stepper and the wafer (4) is set.
On the other hand, under the first exposure and the state where the wafer (4) is moved in the X and Y directions of the stepper from the position of the first exposure, the third side (34) is changed to the first side ( 32) and a second exposure facing the wafer (4) and a second exposure of the wafer (4).
A third exposure in which the fourth side (35) is opposed to the second side (33) in the first exposure under a state where the stepper is moved in one of the X and Y directions of the stepper; Under the condition that the wafer (4) is moved from the position of the first exposure in the X and Y directions of the stepper mainly in one direction, the first side (32) and the second side (33) are respectively moved to the fourth side in the first exposure. Side (3
5) and a fourth exposure which is opposed to the third side (34) in close proximity, and the first side (32) and the third side (34) which are opposed to each other are transferred onto the wafer (4). The first combined pattern (48A) having two opposite facing sides (42, 44a) and the second facing pattern described above.
Two opposite sides (43, 43) to which the side (33) and the fourth side (35) are transferred
Second composite pattern (48B) having 45a), and facing 2 to which the opposed third side (34) and second side (33) are transferred
A third composite pattern (48C) having sides (44, 43a) and a fourth composite pattern having opposing two sides (45, 42a) to which the opposing fourth side (35) and first side (32) are transferred. Pattern (48D)
Is formed, and the distances a, b, c, and d between the opposing two sides of the first, second, third, and fourth combined patterns (48A to 48D) are measured,
The die rotation due to the set deviation of the reticle (3) is obtained by (ab + c−d) / 2, and the set of the reticle (3) is adjusted so that the die rotation becomes 0. An exposure method characterized by performing exposure for formation. 2. The exposure method according to claim 1, wherein the fourth exposure is omitted and the die rotation is determined by (ab) / 2.