TWI667458B - Reticle transmittance measurement method, projection exposure device, and projection exposure method - Google Patents

Abstract

When the grating is used for the first time, the grating is actually placed in the apparatus, and the tilt measurement/random measurement is performed, whereby even if the number of samples is not increased, the risk of bias sampling can be avoided, and the grating transmittance of the entire grating as the mother can be grasped. Further, the same measurement effect can be obtained by changing the incident angle which is generally fixed and changing the incident angle according to the measurement point size.

Description

Grating transmittance measuring method, projection exposure device and projection exposure method

The present invention relates to a transmittance measuring method used for a grating for manufacturing a semiconductor device, and a projection exposure apparatus and a projection exposure method used for the measurement.

In a projection exposure apparatus, such as a stepper, if a grating is used for the first time, a grating is actually placed in the apparatus, and a mercury lamp of the light source is used for exposure, and the transmission/incident energy is calculated and sent back as a grating transmittance. . At this time, the grating pattern is entirely exposed at equal intervals for sampling. When the whole grating is regarded as a mother, the characteristics must be estimated, but it is extremely difficult to identify what kind of pattern is in reality, and therefore, there is a tendency to become a biased sampling. For example, in a pattern that is reversed by the same pitch as the sampling, the result of returning as the grating transmittance deviates from the actual value. In the projection exposure apparatus, if the amount of transmitted light increases, the correction function can function to cancel the effect of lens expansion accompanying heat generation when the exposure load becomes large, but if it is not correctly fed, the focus shifts, the line is caused. The unevenness of the width is increased, or the shape of the resist cannot maintain a rectangular shape, and it is difficult to form a desired pattern. A short circuit/open circuit occurs in the wiring pattern, which may impair the quality.

Therefore, it is desirable to grasp the entire grating as the parent by increasing the number of samples. However, if measured at equal intervals, there is a risk of biased sampling. Even if it is assumed that the measurement can be performed correctly, there is a problem that it takes a large amount of time in the measurement, which impairs the productivity of the projection exposure apparatus.

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2001-297961

[Patent Document 2] Japanese Patent Laid-Open No. Hei 6-236838

As described in the prior art, if there is a pattern which is repeated at the same pitch as the sampling, the result of the grating transmittance may cause a problem of deviating from the actual value. For example, if the grating transmittance of the pattern feature is taken into consideration, as shown in Patent Document 1, there is a method of performing total light amount measurement of the grating when the shot is different for each shot, and the memory is projected. The data is obtained by calculating the exposure portion of the actual grating from the opening and closing of the shielding blade and calculating the grating transmittance. In order to calculate the actual exposed portion of the grating, it is premised that the total amount of total light can be accurately measured at the beginning. Even if it is desired to open and close the shielding blade, the exposed portion is actually calculated, and there is also a pattern which is repeated at the same pitch as the sampling. In the case of the case, the result of returning as the grating transmittance is actually deviated from the actual, and it is difficult to calculate the exposed portion of the actual grating.

Further, if the grating transmittance is to be accurately measured, it is desirable to grasp the entire grating as the parent by increasing the number of samples. Further, as shown in Patent Document 2, there is an image data in which a grating is actually placed in a device, exposed by a mercury lamp of a light source, and a transfer image of the formed grating pattern is taken in, and image data obtained therefrom are obtained. A method of outputting a grating transmittance, but any one of them increases the number of samples and takes a large amount of time for measurement, which may impair the productivity of the projection exposure apparatus.

The present invention has been made in view of the above problems, and a novel measuring method and a projection exposure apparatus for measuring a grating transmittance for calculating a load used for exposure load correction are included as projection exposure apparatuses. A measure of the focus shift caused by the expansion of the lens with an increased exposure load.

In order to solve the above problems, the following methods are used in the exposure method of the semiconductor device of the present invention.

When the grating is used for the first time, the grating is actually placed in the apparatus, and the tilt measurement/random measurement is performed, whereby the risk of bias sampling can be avoided even if the number of samples is not increased, and the entire grating as the mother can be grasped. As a result, the result of returning as the grating transmittance is higher than that of the actual one. Further, the size of the fixed measurement spot is variable, and the change of the incident angle according to the size of the measurement point is performed, thereby obtaining the same The effect.

Further, in the sampling, the grating transmittance of the entire grating is obtained by measuring the transmittance of at least one of the wafer regions to which the grating of the same wafer is applied.

In addition, the feature is as follows: by switching the design data of the grating pattern, even if the grating transmittance is not actually measured, in order to obtain the grating transmittance in a short time, a standard CAD tool is used to create a grating pattern. The design of the data; the design data, in accordance with the standard file format of the streaming format (called GDSII) or cif format, such as the data written by the mask for data conversion; the converted design The data, the calculation of the grating transmittance, and the engineering of the obtained grating transmittance. Further, it is formed as a semiconductor exposure apparatus or a method of exposure, which is characterized in that the grating transmittance is not measured using an actual grating, and the grating transmittance is directly obtained from the data.

According to the present invention, it is possible to provide a method of obtaining a grating transmittance with high precision and a short time even in a pattern having any characteristic, that is, a method of obtaining a correct grating transmittance without impairing productivity, as a projection exposure A countermeasure against focus shift in the device due to lens expansion accompanying an increase in exposure load.

1‧‧‧Lighting Optics

2‧‧‧Raster (original)

3‧‧‧Projection Optics

4‧‧‧Mobile stage

5‧‧‧Sucker

6‧‧‧Photodetector

7‧‧‧CPU (exposure load correction device)

8‧‧‧Grating transmittance memory device

9‧‧‧Design materials

10‧‧‧Spot meter (spot) (point of measuring light amount)

11‧‧‧Measurement points viewed from the front (small size, eg 0.3mm Situation)

12‧‧‧An angle of inclination θ1 from the surface of the grating

13‧‧‧Measurement points viewed from the front (large size, eg 1.0mm Situation)

14‧‧‧An angle of inclination θ2 from the surface of the grating

15‧‧‧A wafer area for transmittance measurement

16‧‧‧ Four wafer areas for transmittance measurement

17‧‧‧The transmittance measurement is concentrated in the area of 1/4 of the entire grating

Fig. 1 is a configuration diagram of a stepping machine according to an embodiment of the present invention.

Fig. 2 is a structural diagram of a conventional stepping machine.

Fig. 3 is an explanatory view for explaining a method of performing tilt measurement of a grating transmittance.

4 is an explanatory view for explaining a method of randomly measuring a grating transmittance.

Fig. 5 is an explanatory diagram for explaining a method of performing tilt measurement in accordance with a small measurement point size.

Fig. 6 is an explanatory diagram for explaining a method of performing tilt measurement in accordance with a large measurement point size.

Fig. 7 is an explanatory view for explaining a method of measuring transmittance of a wafer region.

Fig. 8 is an explanatory view for explaining a method of measuring transmittance of four wafer regions.

FIG. 9 is an explanatory diagram for explaining a method of measuring transmittance in a region concentrated in an arbitrary region.

Fig. 1 is a configuration diagram of a stepping machine which is one of projection exposure apparatuses according to an embodiment of the present invention, and has a function of performing exposure load correction from design data. The stepper system has: an illumination optical system 1; an original plate for actually measuring the grating transmittance, that is, a grating 2; for reducing the grating pattern to, for example, one-fifth, and transferring the desired pattern by exposure a projection optical system 3 on the wafer; a stage 4 for moving the wafer to a predetermined measurement spot for measuring the transmittance of the grating; a suction pad 5 for supporting the wafer; and a measurement projection The optical detector 6 of the optical system; and the exposure load correction by the measured grating transmittance, or the grating transmittance by the design data, and the exposure load correction is performed to control the illumination optical system 1 or the stage 4 Driven by CPU7.

The grating transmittance memory device 8 is a memory device for storing data of the actually measured grating transmittance or data of the grating transmittance calculated by the design data 9. The method of using design data 9 will be described later.

A block diagram of a conventional stepper is shown in Figure 2 for reference. The clear difference is that in the conventional stepper, there is no connection with the design data, and the raster transmittance memory device 8 does not effectively utilize the data of the grating transmittance calculated from the design data.

According to the above configuration, if there is a pattern which is reversed at the same pitch as the sampling, it is possible to solve the conventional problem that the result of returning as the grating transmittance deviates from the actual value. The method of measuring the grating transmittance will be specifically described below.

The first method is as shown in FIG. 3. For example, it is conventionally measured at a pitch of 0.2 mm in the X and Y directions. For example, the light measuring point 10 is obliquely taken into a diagonal shape of the grating, and the measurement is performed at a pitch of 0.2 mm. By obliquely diagonally herein is meant a straight line that is inclined along the four sides of the grating and that generally does not coincide with the diagonal. At this time, the sampling in the X and Y directions is set so as to have different intervals with respect to the reverse pattern of the grating. Further, the measurement point 10 may be obliquely obtained in a diagonal shape of the grating, and the transmittance may be measured at different pitches such as 0.2 mm, 0.3 mm, 0.2 mm, and 0.3 mm. At this time, the sampling in the X and Y directions is also set with respect to the reverse pattern of the grating so as to be superimposed into different patterns without overlapping the same pattern.

The grating transmittance as a characteristic of the entire grating is obtained from the above-described sampling, and is stored in the grating transmittance memory device 8. According to the obtained grating transmittance, the CPU (exposure load correction device) 7 of FIG. 1 performs exposure load correction in combination with focus, lens distortion, and magnification as needed, and feeds back to the projection optical system 3 of FIG. Projection exposure.

The second method is as shown in FIG. 4, for example, it is conventionally measured in the X and Y directions at a pitch of 0.2 mm, for example, the pitch of the measurement points 10 has a width of 0.2 to 1.0 mm, which is originally X, In the Y direction, the individual moves in sequence and randomly move, and the irregular measurement is performed. The reversed pattern of the raster is set so that the sampled actor is superimposed in a different pattern without overlapping the same pattern.

The third method is shown in FIG. 5, and the conventional measurement point is, for example, 0.3 mm. For the fixer, at 0.3mm ~1.0mm To be variable, the tilt angle is changed according to the size of the measurement point. The size of the measurement point 11 viewed from the front is small, for example, 0.3 mm At the time of viewing from the front side, the grating transmittance is measured by attaching a small inclination of 10 to 30 degrees from the inclination angle θ1 (12) of the surface of the grating 2. As described above, in the case where the size of the measurement point is small, the effective measurement area can be largely ensured. On the other hand, as shown in FIG. 6, the size of the measurement point 13 viewed from the front side is large, for example, 1.0 mm. At the time of viewing from the front side, the grating transmittance is measured by a large inclination between 70 and 90 degrees from the inclination angle θ2 (14) of the surface of the grating 2. This is based on the fact that if the size of the measurement point is large, a large measurement area can be ensured. As described above, by changing the size of the measurement point, sampling by the same pattern can be prevented.

In the fourth method, as shown in FIG. 7, in a multi-faceted grating composed of a plurality of identical wafers, only one wafer region is sampled to measure transmittance, and a method of calculating a grating transmittance is obtained. The one wafer region 15 as used herein means, for example, a region surrounded by an operation region of the semiconductor element and an outer region thereof which is surrounded by a region to the center (middle) of the dicing line which is cut by the dicing. In addition, in the case of a full area with multiple faces, it means that the gratings including all of the unit areas are comprehensive. These lines are formed as pre-sampled areas and full areas with multiple faces to input parameters at the device. The area ratio of one wafer region 15 to the entire area with a plurality of faces is calculated, and the grating transmittance of the entire grating is obtained and stored in the grating transmittance memory device 8. According to the obtained grating transmittance, the CPU (exposure load correction device) 7 of FIG. 1 performs exposure load correction in combination with focus, lens distortion, and magnification as needed, and feeds back to the projection optical system 3 of FIG. Projection exposure.

The fifth method is a method of calculating the transmittance of the grating by sampling four wafer regions 16 in a multi-faceted grating composed of a plurality of identical wafers, as shown in FIG. The area ratio of the four wafer regions 16 to the entire area with the multi-faceted area is calculated, and the total transmittance of the grating is obtained, whereby the exposure load correction similar to the fourth method can be performed.

In the sixth method, as shown in FIG. 9, in a multi-faceted grating composed of a plurality of identical wafers, a region 1/4 concentrated in the entire grating is sampled to measure transmittance, and the result is obtained. A method of calculating the grating transmittance. By concentrating on the 1/4 area of the entire grating 17 and attaching more The area ratio of the entire area of the surface is calculated, and the grating transmittance of the entire grating is obtained, thereby shortening the time required for the normal 1/4, and the exposure load correction similar to the fourth and fifth methods can be performed.

The seventh method is different from the above method, and actually, the transmittance measurement is not performed to determine the grating transmittance. In order to obtain the design material 9 of Fig. 1, the design data of the grating is first made CAD for the full layer. Next, the design data is converted into a standard file format streaming format (referred to as GDSII) or cif format. Next, from the converted data, the grating transmittance is obtained from the occupied area of the light-shielding film on the grating, and the data is stored as the grating transmittance in the raster transmission rate device 8 of FIG. According to the raster transmittance of the data storage, the CPU (exposure load correction device) 7 of FIG. 1 performs exposure load correction in combination with focus, lens distortion, and magnification as needed, and feeds back to the projection optical system 3 of FIG. Thereby, the transmittance measurement is not performed by the actual grating, and the grating transmittance can be obtained in a short time. By comparing the grating transmittance obtained by the measurement in such a manner with the grating transmittance obtained by the first to sixth methods, the accuracy of the grating transmittance can be improved from the CAD data. Or to achieve the appropriate sampling in the measurement, can improve the accuracy.

[Industrial availability]

It is possible to use a device that is capable of performing microfabrication with engineering using a photolithography technique using a grating in a projection exposure apparatus such as a semiconductor substrate or a MEMS.

Claims (10)

A method for measuring a grating transmittance, which is a method for measuring a grating transmittance of a sample in a projection exposure apparatus that projects a pattern of a grating onto a wafer and obtains a predetermined pattern on the wafer, and is characterized by: sampling in the foregoing In the above, the transmittance is measured obliquely in the diagonal direction of the grating, and the pitch is set so as to overlap the reverse pattern of the grating so as not to overlap the same pattern. A method for measuring a grating transmittance, which is a method for measuring a grating transmittance of a sample in a projection exposure apparatus that projects a pattern of a grating onto a wafer and obtains a predetermined pattern on the wafer, and is characterized in that the sampling system is A value having a fixed pitch in the X and Y directions is not obtained, and a value of a predetermined range is randomly obtained, whereby the reverse pattern provided in the grating is set so as to overlap the different patterns without overlapping the same pattern. . A method for measuring a grating transmittance, which is a method for measuring a grating transmittance of a sample in a projection exposure apparatus that projects a pattern of a grating onto a wafer and obtains a predetermined pattern on the wafer, and is characterized in that the measurement point is made The size of the measurement is variable, and if the size of the measurement point is small, the inclination angle θ1 of the grating surface viewed from the front side is gently inclined from 10 degrees to 30 degrees. The transmittance is measured. If the size of the measurement point is large, the inclination angle θ2 of the grating surface viewed from the front side is inclined by a steep slope between 70 degrees and 90 degrees, by using the size of different measurement points. The aforementioned sampling is used to determine the grating transmittance. A method for measuring a grating transmittance, which is a method for measuring a grating transmittance of a sample in a projection exposure apparatus that projects a pattern of a grating onto a wafer and obtains a predetermined pattern on the wafer, and is characterized by: sampling in the foregoing In the measurement, the transmittance of at least one of the wafer regions of the grating of the same wafer to which the plurality of faces are added is measured, and the grating transmittance is calculated. The method for measuring a grating transmittance according to claim 4, wherein the one wafer region is a unit region surrounded by an operation region of the semiconductor element and an outer region thereof by a region to the center of the surrounding cutting line. A projection exposure method for performing exposure load correction according to a grating transmittance obtained by a grating transmittance measuring method according to the first aspect of the patent application. The projection exposure method of claim 6, wherein the exposure load correction is at least one of focus correction, lens distortion correction, and magnification correction. A projection exposure apparatus capable of performing a grating transmittance measurement using sampling, projecting a pattern of a grating onto a wafer, and obtaining a predetermined pattern on the wafer, wherein the sampling is performed The transmittance measurement is performed obliquely in the diagonal direction of the grating, and the pitch can be set so as to be different from the reverse pattern of the grating. A projection exposure apparatus capable of performing a grating transmittance measurement using sampling, projecting a pattern of a grating onto a wafer, and obtaining a predetermined pattern on the wafer, wherein: The sampling system does not have a value in which the pitch in the X and Y directions is fixed, and a value in a predetermined range is randomly obtained, whereby the reverse pattern provided in the grating can be set so as not to overlap and be different patterns. . A projection exposure apparatus capable of performing a grating transmittance measurement using sampling, projecting a pattern of a grating onto a wafer, and obtaining a predetermined pattern on the wafer, wherein: in the sampling, The size of the measurement point is made variable, and in the variable range, if the size of the measurement point is small, the inclination angle θ1 of the grating surface viewed from the front side is a gentle inclination close to 0 degree. The grating transmittance is measured, and if the size of the measurement point is large, the grating is measured by the inclination angle θ2 of the grating surface viewed from the front side, and the inclination of the grating is measured by a steep slope of approximately 90 degrees, by making the size of the measurement point The aforementioned sampling was changed to determine the grating transmittance.