JPH09199412A - Semiconductor aligner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the alignment accuracy and transfer accuracy of a mask and a wafer and thereby increase the productivity without decreasing a throughput by eliminating an alignment error between the mask and the wafer caused by the deformation of a mask membrane when moving a stage in a semiconductor aligner. SOLUTION: This equipment, being provided with a position measuring means which measures a positional relationship between a mask 1 having a mask pattern on a mask membrane 3 and a semiconductor wafer, aligns the mask 1 and the wafer based on the positional relationship between the two and then transfers the mask pattern onto the wafer. When aligning the mask 1 and the wafer, the deformation of the mask membrane 3 in the direction vertical to the mask membrane 3 should be taken into consideration.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor exposure apparatus which exposes and transfers a fine pattern of a semiconductor integrated circuit drawn on a mask onto a wafer, and in particular, a mask and a wafer are brought close to each other at a fine interval. The present invention relates to a so-called proximity exposure device that performs exposure.

[0002]

2. Description of the Related Art A typical example of a proximity exposure apparatus is an X-ray exposure apparatus. For example, an X-ray exposure apparatus using an SR light source is disclosed in Japanese Patent Application Laid-Open No. 2-100311.

A general configuration of such an X-ray exposure apparatus is shown in FIG. In FIG. 10, 1 is a mask, 2 is a mask chuck for holding the mask, 3 is a mask membrane,
4 is a mask chuck base. Reference numeral 5 is a wafer, and 6 is a wafer chuck for holding the wafer. Reference numeral 7 is a fine movement stage used for aligning the mask and the wafer, 8 is a coarse movement stage used for movement between shots, and 9 is a stage base to which the guide of the coarse movement stage 8 is fixed. Wafer 5 and wafer chuck 6 are fine movement stage 7
Mounted on top.

In such an X-ray exposure apparatus, generally, exposure is performed by a so-called step-and-repeat method in which a mask pattern is repeatedly exposed on a wafer a plurality of times, and the mask and the wafer are opposed at an interval of 10 to 50 μm. Exposure (proximity exposure). In the X-ray mask, the area where the absorber pattern is formed is 2 μm.
It is a thin film with a thickness of about m (hereinafter referred to as a membrane).

In such a conventional X-ray exposure apparatus,
The procedure for performing exposure by the die-by-die method is as follows.

(1) The coarse movement stage 8 is driven so that the portion for exposing the nth shot of the wafer 5 is below the mask membrane 3. (2) The wafer 5 is moved by the fine movement stage 7, and the gap between the mask 1 and the wafer 5 (hereinafter referred to as the gap) is measured from the gap during the step (hereinafter referred to as AF measurement).
The AF measurement is performed by driving to a position that becomes a gap for performing. (3) After the mask 1 and the wafer 5 are parallelized by the fine movement stage 7, the mask 1 and the wafer 5 are driven to a gap for measuring the positional deviation of the mask 1 and the wafer 5 in the in-plane direction (hereinafter referred to as AA measurement), and AA is measured. Measure. (4) The wafer 5 and the mask 1 are aligned and exposed. (5) Retract the wafer 5 to the gap position at the time of step. Hereinafter, the steps (1) to (5) are repeated.

[0007]

In such a conventional proximity exposure apparatus, since the mask and the wafer are close to each other at a very small interval (several tens of μm), the gap setting, the retracting, the step moving, etc. When moving the stage of
It is assumed that the mask membrane is deformed. Therefore, there are the following problems. (1) The AF measurement value changes by the deformation of the mask membrane. (2) The alignment mark on the membrane is displaced in the in-plane direction due to the deformation of the mask membrane, and the alignment accuracy is reduced.

In order to solve these problems, for example, AF and AA are performed after a sufficient time has elapsed after setting the exposure gap.
Possible methods include measuring, or slowly driving the stage so that the membrane is not deformed.
These methods result in a decrease in throughput.
The object of the present invention is to solve the problems of the conventional art.
In semiconductor exposure equipment, the mask-wafer alignment error due to the deformation of the mask membrane during stage movement is eliminated, thus improving the mask-wafer alignment accuracy and transfer accuracy without lowering the throughput and improving productivity. Is to let.

[0009]

In order to achieve this object, in the present invention, a mask pattern is provided as a mask membrane (3).
A semiconductor is provided which is provided with position measuring means (11) for measuring the positional relationship between the mask and the semiconductor wafer (5) provided above, and the mask and the wafer are aligned based on this positional relationship to expose a mask pattern on the wafer. In the exposure apparatus, the alignment between the mask and the wafer is performed in consideration of the amount of deformation of the mask membrane in the direction perpendicular to the mask membrane.

In this structure, when the mask membrane is deformed in the vertical direction by the operation of the apparatus, an error occurs in the measured value of the positional relationship between the mask and the wafer. Considering this vertical deformation amount (ΔG1, ΔG2). Then, the alignment between the mask and the wafer is performed so that the error is removed.

More specifically, a deformation amount measuring means (1) for measuring the deformation amount at least at one location in the mask membrane.
2) A deformation amount acquisition means (16) for obtaining a deformation amount at a desired position of the mask membrane from the deformation amount, and a correction means (17) for correcting the positional relationship based on the deformation amount at the desired position.

The position measuring means is a means (11) for measuring the distance between the mask and the wafer, and a deviation measuring means (for detecting the marks on the mask and the wafer to measure the in-plane positional deviation thereof). 11). Then, the correction means (17) shifts the mark on the mask in the in-plane direction (Δdα, based on the deformation amount (Δg1) at the desired position.
Δdβ) is obtained, and the measured value of the positional deviation in the in-plane direction is corrected based on this deviation amount. Alternatively, since the measured value of the positional deviation in the in-plane direction has a dependency on the distance, it is corrected based on the measured value of the distance, and the correction means has the deformation amount (Δg2) at the desired position. Based on the above, the measured value of the interval is corrected.

The deformation amount acquisition means may obtain the deformation amounts (Δg1, Δg2) at the desired position based on the relationship between the deformation amount of the at least one location and the convergence of the deformation amount and time. Good.

This apparatus usually has a stage for moving the wafer, but it may be arranged to perform the alignment in consideration of the deformation amount at a desired time based on the drive pattern of the stage (7, 8). Good. In this case, for example, means (12) for obtaining the deformation amount of the mask membrane at a desired time based on the drive pattern of the stage,
And a means for correcting the positional relationship based on the deformation amount.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. However, in FIGS. 1 to 9, the same symbols represent the same elements. (Embodiment 1) FIG. 1 shows the configuration of an X-ray exposure apparatus according to an embodiment of the present invention.

<Description of Device Configuration> In FIG. 1, 1 is a mask, 2 is a mask chuck for holding the mask, 3 is a mask membrane, and 4 is a mask chuck base. Reference numeral 5 is a wafer, and 6 is a wafer chuck for holding the wafer.
Reference numeral 7 is a fine movement stage used for aligning the mask 1 and the wafer 5, 8 is a coarse movement stage used for movement between shots, and 9 is a stage base to which the guide of the coarse movement stage 8 is fixed. The wafer 5 and the wafer chuck 6 are mounted on the fine movement stage 7.

Next, the displacement sensor used in this embodiment will be described. 10 is a direction perpendicular to the mask 1 (hereinafter, Z
Direction), a stage Z sensor 11 for measuring the position of the wafer chuck 6, and a gap 11 between the mask membrane 3 and the surface of the wafer 5 on the mask side (hereinafter, referred to as a gap) and an in-plane deviation amount between them. It is an alignment scope. The alignment scope 11 is mounted on the biaxial stage so that measurement can be performed even if the position of the alignment mark on the mask 1 moves. Although not shown, three stage Z sensors 10 and three alignment scopes 11 are installed so that surface information can be measured. Reference numeral 12 is a non-contact displacement meter that measures the deformation of the mask membrane 3. The non-contact displacement meter 12 is mounted on a uniaxial stage so that it can move back and forth within the exposure area.
The non-contact displacement meter 12 applies laser light to the mask membrane 3 and measures the reflected light.

The entire apparatus is installed in the chamber 13 and is placed in a reduced pressure helium atmosphere during exposure. SR light 14 generated by a light source (not shown) is guided into the chamber 13 through a blocking window 15 (usually a Be window is used). Reference numeral 16 denotes the amount of deformation of the membrane at the position of the alignment mark of the mask 1 and the wafer 5 calculated from the amount of deformation of the membrane 3 delivered from the non-contact displacement meter 12, and the amount of deformation of the membrane 3 causes the mask membrane. 3 is a calculation means for calculating the positional shift of the alignment marks on the surface 3 in the in-plane direction. Further, 17 is a processing means for correcting the information obtained by the alignment scope 11 from the information obtained by the computing means 16.

<Description of Correction Method> The correction of the AF measurement value and the AA measurement value by the deformation amount of the membrane 3 will be described below.

(1) Correction of AF measurement value FIG. 2 shows the deformation and correction method of the membrane 3 during AF measurement. The mask membrane 3 is deformed by ΔG1 as shown in FIG. 2 by the step drive and the drive from the gap position at the time of the step to the gap position for AF measurement. When AF measurement is performed in this state, Δg at the position of the alignment mark 21 with respect to the actual gap G1.
A gap larger by 1 will be measured. If the gap is narrowed from this measured value to the exposure gap, the gap is set smaller than the predetermined exposure gap by Δg1. Further, the wafer 5 and the mask membrane 3 may come into contact with each other depending on the value of Δg1. In order to avoid these, at the same time as the AF measurement, the displacement meter 12 is used to measure the membrane 3
Deformation amount ΔG1 is calculated, the calculation device 16 calculates the deformation amount Δg1 at the position of the alignment mark 21, and the processing means 17 calculates Δg1 with respect to the measured AF measurement value.
Is corrected. Deformation amount of membrane 3 deformation measurement position △
In order to calculate the deformation amount Δg1 from G1 at the alignment mark position, a calculation formula for calculating ΔG1 to Δg1 in the calculation means 16 may be used each time.
The correspondence table of G1 and Δg1 may be stored in the calculation means 16. Also, this table may be created based on a calculation formula, or may be created by performing an experiment in another system and measuring the deformation of the membrane 3.

(2) Correction of AA value due to displacement of alignment mark due to deformation of mask membrane 3 FIG. 3 shows in-plane displacement of the alignment mark 21 on the mask membrane 3 due to deformation of the mask membrane 3. FIG. 4 shows how the alignment mark 21 is displaced from the Z direction. FIG. 5 shows the coordinate system (α, β) of the alignment mark 21. The alignment mark 21 has a direction in which the displacement can be measured (hereinafter, referred to as an alignment direction) with respect to the mark. Therefore, the coordinates (α, β) for the mark are defined separately from the coordinates of the main body.

As shown in FIGS. 3 and 4, the membrane 3 is Z
By being deformed in the direction, the position of the alignment mark on the mask membrane 3 is changed to Δd in the α direction and Δd in the β direction.
Move by β. A method for correcting this deviation will be described below.

When the alignment direction is the α direction in FIG. 5, Δdα is a deviation in the alignment direction, which is an error in the AA measurement value. Since Δdβ is not in the alignment direction, Δdβ does not directly cause an error in the AA measurement value.
However, generally, if there is a deviation between the alignment marks in the direction perpendicular to the alignment direction, the error in the AA measurement value increases. To correct this, the membrane deformation is measured at the same time as the AA measurement. Measured deformation amount in Z direction Δ
The deviation (Δdα, Δdβ) in the in-plane direction is calculated from G1 by the calculating means 16. This deviation (Δdα, Δdβ) is Z
The calculation means 16 calculates the calculation formula from the deformation amount ΔG1
You may keep it inside and calculate it each time, (Δd
The relationship between α, Δdβ) and ΔG1 may be stored as a table in the computing means 16 in advance, and (Δdα, Δdβ) may be calculated. Alternatively, the amount of deformation in the Z direction at the deformation measurement position of the mask membrane 3 and the in-plane displacement at each mark position may be measured in advance by another experimental system and provided as a table in the computing means 16. The AA value measured by this calculated (Δdα, Δdβ) is corrected. In order to correct Δdβ, it is beforehand measured how the deviation between the alignment marks in the direction perpendicular to the alignment direction affects the AA measurement value.
This may be measured in advance on the exposure apparatus, or may be measured by a separate experimental device. Regarding Δdα, the AA measurement value after being corrected by Δdβ is further corrected.
Even when the alignment direction is the β direction in FIG. 5, the correction method is the same except that the coordinates α and β are exchanged.

<Explanation of exposure procedure> A procedure for correcting the AF and AA measurement values from the deformation amount of the membrane, which is a feature of the present invention, will be described below along with the operation of the exposure apparatus. FIG. 6 is a flowchart showing this procedure.

In this embodiment, a procedure for performing exposure by the die-by-die method will be described.

First, the coarse movement stage 8 is driven stepwise so that the portion of the wafer 5 where the nth shot is exposed is under the mask 1 (step S1). At this time, in order to avoid the interference between the wafer 5 and the mask 1, the gap between the wafer 5 and the mask 1 at the time of step is determined to be a sufficiently large value in consideration of the flatness of both and the wedge. In this embodiment, 100 μ
m or more. Simultaneously with this step driving, the displacement meter 12 is positioned within the exposure surface angle of the mask membrane.

Next, the alignment scope 11 sets A
F measurement is performed (step S2). At the same time, the displacement gauge 12 measures the amount of deformation of the mask membrane 3. Then, the measured AF measurement value is corrected by the deformation amount of the mask membrane 3 (step S3), the stage 7 is driven based on the corrected AF measurement value, and the mask 1 and the wafer at the gap position during AA measurement. 5 are parallel to each other (step S4).

Next, the alignment scope 11 sets A
A is measured, and at the same time, the deformation amount of the mask membrane 3 is measured (step S5). Then, the measured AA measurement value is corrected from the deformation amount of the mask membrane 3 (step S6), and the fine movement stage 7 is driven based on the corrected AA measurement value to align the mask 1 and the wafer 5. (Step S7).

Next, if the amount of deformation of the membrane 3 is less than or equal to the allowable value, the mask membrane deforming means is retracted from the exposure field angle (step S8) and exposure is performed (step S).
9). Then, when the exposure is completed, the gap is set to the step driving gap (100 μm) (step S1).
0), the coarse movement stage 8 is driven so that the portion for exposing the (n + 1) th shot is below the mask 1 (step S).
11).

The above steps S1 to S11 are repeated to expose the wafer 5 for a predetermined number of shots.

As described above, in the present embodiment in which the AF and AA measurement values are corrected based on the deformation amount of the mask membrane 3, the AF and AA measurements can be performed with high accuracy while the mask membrane 3 is deformed. Throughput can be improved.

In this embodiment, the case of the die-by-die alignment method has been described, but the above correction is also effective for the alignment of the mask and the wafer of the global alignment method. Further, as the non-contact displacement type 12 for measuring the deformation of the mask membrane 3, other than the one using a laser, an interferometer for measuring the interference fringes of the mask membrane 3, an air micro, or the like can be used to measure the displacement in a non-contact manner. I wish I had it.

In this embodiment, the case where the AF measurement gap and the AA measurement gap (= exposure gap) are different, that is, the case where the AF measurement range is larger than the exposure gap has been described.
It is effective even when the measurement gap is the same. The correction of the AF measurement value when the AA and AF measurement gaps are set is the same as when the above gaps are different. In the correction during the AA measurement, the gap changes and the membrane 3 is deformed due to the parallel alignment of the mask and the wafer after the AF measurement. Therefore, as in the case where the AA measurement gap and the AF measurement gap are different from each other, the membrane 3 is measured during the AA measurement. The deformation of is measured and corrected.

(Embodiment 2) Next, an embodiment of correction when the AA measurement value varies depending on the gap between the mask and the wafer will be described. In this case, after performing the correction described in the first embodiment, it is necessary to further correct the AA measurement value by the deformation amount of the membrane 3 because the AA measurement value has the gap dependency. That is, in the method of detecting the positional relationship between the mask and the surface of the wafer by the center of gravity of the spot of the measurement light diffracted by the diffraction grating formed on the mask and the wafer and imaged on the sensor, The gap variation causes an error in the AA measurement value. That is, the imaged spot is the sum of lights that have passed through two different optical paths, and if the gap between the mask and the wafer changes, the change in the amount of light will differ between the lights that have passed through the two optical paths. Therefore, an error occurs in the center of gravity of the spot. Further, when the AA measurement light is not perpendicular to the wafer surface, the AA detection method is not limited to the AA detection method using the diffraction grating.

FIG. 7 is a diagram for explaining this embodiment. A gap is measured in the AF measurement gap G1, the fine movement stage 7 is driven, the gap is narrowed to the AA measurement gap G2, the mask 1 and the wafer 5 are parallelized, and AA measurement is performed. At this time, the surface of the wafer has undulations and the like, and the gaps are different at the positions of the respective alignment marks even if they are aligned in parallel. So A
Deviations δ1 and δ2 from the specified value of the gap at each mark position are calculated from the F measurement value, and the AA measurement value is corrected with the calculated values. However, as shown in FIG. 7, when the gap is narrowed from G1 to G2, the mask membrane 3
Is deformed by ΔG2, and the gap during AA measurement is A
Δg2 at the position of the alignment mark 21 compared to when measuring F
Only changing. In order to correct this, the displacement measuring means 12 measures the deformation ΔG2 of the membrane 3 at the time of AA measurement, the calculating means 16 calculates the deformation amount Δg2 at the position of the alignment mark 21, and at each mark position calculated by the calculated value. The gap deviations δ1 and δ2 are corrected. The AA measurement value is corrected based on the corrected deviation of the gap.

By performing the above correction, AA
Highly accurate positioning is possible even in the AA measurement method in which the measurement value causes an error due to the gap. The flow of correction of this embodiment is the same as that of the flow chart of the first embodiment shown in FIG. 6 because the number of correction items during AA measurement only increases. Further, the case of the present embodiment is also effective when the AF measurement gap and the AA measurement gap are the same as in the case of the first embodiment.

(Third Embodiment) FIG. 8 is a flowchart showing an exposure procedure according to the third embodiment of the present invention. In the present embodiment, the processing means 1 uses the curve of displacement and time from the deformation of the mask membrane 3 to the convergence as a table.
7, the displacement is measured once after driving the stage, and thereafter the displacement at each time point is calculated using the table from the time after the displacement of the membrane 3 is measured. Further, the relationship between the displacement of the membrane 3 and the time is measured in advance on the exposure device and stored in the processing means 17. In order to improve the accuracy, it is effective to have a table for each mask. By having the displacement information as a table as described above, the following effects can be obtained.

It is sufficient to measure the displacement of the membrane once each time the stage is driven. Immediately after the measurement, the displacement gauge 12 can be retracted from the exposure angle of view by the membrane deformation measuring means (step S81). The exposure can be started without waiting for the displacement meter 12 to retract. Therefore, the throughput can be improved. (Embodiment 4) FIG. 9 is a flowchart showing an exposure procedure according to the fourth embodiment of the present invention. In the present embodiment, the required parameters of the stage drive pattern, that is, the stage drive amount, the drive speed, the drive initial position, the drive final value, and the time after the stage positioning are selected according to the stage drive direction, and the time is selected from those parameters. The calculation means 16 is a table for calculating the deformation amount of the membrane 3 of FIG.
To have. Thereby, the membrane 3 at the time of AF and AA measurement
The amount of deformation is calculated by the calculating means 16 using the stage drive pattern immediately before the measurement and the time of measurement from the stage positioning as a parameter (step S92). Based on the calculated deformation amount of the mask membrane 3, the AF and AA measurement values are corrected as shown in the first and second embodiments. In order to make a table of the drive pattern of the stage, the time after the stage is positioned, and the deformation amount of the mask membrane 3, the main body of the apparatus is used, and a membrane deformation amount measuring means, which is separate from the main body, is installed in the main body in advance. The deformation of the membrane may be measured, or the amount of deformation of the membrane may be measured by an experiment device different from the main body. By having a table of such a stage drive pattern, the time after stage positioning and the deformation amount of the membrane 3,
Since it is not necessary to provide the deformation measuring means in the main body, the device configuration becomes simple.

[0039]

As described above, according to the present invention,
It is possible to eliminate the alignment error between the mask and the wafer due to the deformation of the mask membrane when the stage is moved.
Therefore, the alignment accuracy between the mask and the wafer and the productivity can be improved. Further, by performing the alignment in consideration of the deformation amount of the mask membrane based on the drive pattern of the stage, the device configuration can be simplified.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an X-ray exposure apparatus according to a first embodiment of the present invention.

FIG. 2 is a conceptual diagram showing a method for correcting an AF measurement value in the apparatus shown in FIG.

FIG. 3 is a conceptual diagram showing a method of correcting an AA measurement value in the apparatus of FIG.

FIG. 4 is a view of the alignment mark shift in FIG. 3 seen from above.

5 is a diagram showing a coordinate system of the alignment mark in FIG.

6 is a flowchart showing a correction procedure in the apparatus of FIG.

FIG. 7 is a conceptual diagram showing a method of correcting an AA measurement value according to a second embodiment of the present invention.

FIG. 8 is a flowchart showing a correction procedure according to the third embodiment of the present invention.

FIG. 9 is a flowchart showing a correction procedure according to the third embodiment of the present invention.

FIG. 10 is a schematic configuration diagram showing a conventional X-ray exposure apparatus.

[Explanation of symbols]

1: mask, 2: mask chuck, 3: mask membrane, 4: mask chuck base, 5: wafer, 6: wafer chuck, 7: fine movement stage, 8: coarse movement stage,
9: Stage base, 10: Stage Z sensor, 11:
Alignment scope, 12: non-contact displacement meter, 13: chamber, 14: SR light, 15: blocking window, 16: deviation calculating means, 17: correcting means, 21: alignment mark.

Claims (8)

[Claims] 1. A position measuring means for measuring a positional relationship between a mask having a mask pattern on a mask membrane and a semiconductor wafer is provided. Based on this positional relationship, the mask and the wafer are aligned to form the mask pattern. In the semiconductor exposure apparatus for exposing the wafer, the alignment between the mask and the wafer is performed in consideration of a deformation amount of the mask membrane in a direction perpendicular to the mask membrane. 2. At least one in the mask membrane
Deformation amount measuring means for measuring the deformation amount of a location, deformation amount acquisition means for obtaining the deformation amount at a desired position of the mask membrane from the deformation amount, and correction means for correcting the positional relationship based on the deformation amount at the desired position The semiconductor exposure apparatus according to claim 1, further comprising: 3. The semiconductor exposure apparatus according to claim 2, wherein the position measuring means has means for measuring a distance between the mask and the wafer. 4. The position measuring means has a deviation measuring means for detecting marks on the mask and the wafer and measuring positional deviations of the marks on the mask and the wafer, and the correcting means measures the amount of deformation at the desired position. The displacement amount of the mark on the mask in the in-plane direction is obtained based on the displacement amount, and the measured value of the positional displacement in the in-plane direction is corrected based on the displacement amount. Semiconductor exposure equipment. 5. The position measuring means comprises a deviation measuring means for measuring a deviation in the in-plane direction between the mask and the wafer and a distance measuring means for measuring a distance between the mask and the wafer, and the position in the in-plane direction. Since the measured value of the deviation has a dependency on the interval, it is corrected based on the measured value of the interval, and the correction means corrects the measured value of the interval based on the deformation amount at the desired position. The semiconductor exposure apparatus according to claim 2, wherein the semiconductor exposure apparatus is provided. 6. The deformation amount acquisition means obtains the deformation amount at the desired position based on the relationship between the measured deformation amount and the convergence of the deformation amount and time. The semiconductor exposure apparatus according to claim 2. 7. The half-body exposure according to claim 1, further comprising a stage for moving the wafer, and performing alignment in consideration of the deformation amount at a desired time based on a drive pattern of the stage. apparatus. 8. A means for obtaining a deformation amount of the mask membrane at a desired time based on a drive pattern of the stage, and a means for correcting the positional relationship by the deformation amount. 7. The semiconductor exposure apparatus according to 7.