JP2016072598A - Reticle transmissivity measuring method, projection exposure device and projection exposure method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for calculating reticle transmissivity without impairing productivity even for a pattern having any features as measures to cope with out-of-focus caused by lens expansion with increase of an exposure load in a projection exposure device.SOLUTION: When using a reticle for the first time, the reticle is actually put into a device and oblique measurement/random measurement is performed. Therefore, even without increasing the number of times of sampling, the risk of erroneous sampling can be avoided and the entire reticle that is a mother group can be captured. A fixed measurement spot size is made variable and an incidence angle is changed in accordance with the measurement spot size, thereby also obtaining similar effects.SELECTED DRAWING: Figure 3

Description

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

  When a first reticle is used in a projection exposure apparatus such as a stepper, the reticle is actually put into the apparatus, exposure and transmission / incident energy are calculated with a mercury lamp as a light source, and returned as reticle transmittance. At this time, the entire reticle pattern is exposed and sampled at equal intervals. When the entire reticle is viewed as a population, it is necessary to estimate the characteristics. However, since it is practically difficult to recognize what kind of pattern it is, there is often a risk of biased sampling. For example, in a pattern repeated at the same pitch as sampling, the result returned as the reticle transmittance is different from the actual. In the projection exposure apparatus, when the amount of light transmitted increases, the correction function works to cancel the influence of lens expansion due to heat generation when the exposure load increases. As a result, it is difficult to form a desired pattern due to an increase in the variation of the resist pattern and the resist profile, and it is difficult to form a desired pattern.

  For this reason, by increasing the number of samplings, an attempt is made to capture the entire reticle as a population. However, when measuring at equal intervals, the risk of biased sampling remains. Even if it can be measured accurately, there is a problem that the measurement takes a long time and the productivity of the projection exposure apparatus is impaired.

JP 2001-297916 A JP-A-6-236838

  As described in the background art, when there is a pattern repeated at the same pitch as the sampling, there is a problem that the result returned as the reticle transmittance is different from the actual one. For example, when calculating the reticle transmittance in consideration of the characteristics of the pattern, as in Patent Document 1, when the area is different for each shot, the total amount of light of the entire reticle is measured, and the data for the projection image is stored. There is a method of calculating the reticle transmittance by calculating the actual exposure portion of the reticle from the data and opening / closing of the masking blade. In order to calculate the actual exposed portion of the reticle, it is a precondition that the total light quantity measurement on the entire reticle surface can be accurately performed first. Even if the exposure part is actually calculated by opening and closing the masking blade, if there is a pattern that repeats at the same pitch as the sampling, the result returned as the reticle transmittance will deviate from the actual, and the actual exposure part of the reticle will be It becomes difficult to calculate.

  In addition, in order to accurately measure the reticle transmittance, the entire reticle as a population is captured by increasing the number of samplings. Further, as in Patent Document 2, a reticle is actually placed in an apparatus, exposed with a mercury lamp as a light source, image data of a transfer image of the formed reticle pattern is taken in, and based on the image data obtained thereby. In any case, there is a method for obtaining the reticle transmittance. However, in any case, the enormous number of samplings increases, so that enormous time is required for the measurement and the productivity of the projection exposure apparatus is impaired.

  The present invention has been made in view of such a problem, and its problem is to calculate a load used for exposure load correction as a countermeasure against a focus shift due to lens expansion accompanying an increase in exposure load in the projection exposure apparatus. It is an object of the present invention to provide a new measuring method and a projection exposure apparatus for measuring reticle transmittance.

In order to solve the above problems, the following means are used in the exposure method of the semiconductor device of the present invention.
When using the reticle for the first time, it is possible to avoid the risk of biased sampling without increasing the number of samplings by actually putting the reticle into the device and performing oblique measurement and random measurement, and the entire reticle as a population can be avoided. It becomes possible to capture. As a result, the result returned as the reticle transmittance can be obtained with higher accuracy than the actual result. In addition, it is possible to obtain the same effect by changing the size of the fixed measurement spot and changing the incident angle according to the size of the measurement spot.

  In the sampling, the reticle transmittance of the entire reticle is determined by measuring the transmittance of at least one chip region of the reticle having a plurality of identical chips.

  In addition, by using the reticle pattern design data, the reticle pattern design data can be created using a standard CAD tool in order to obtain the reticle transmittance in a short time without actually measuring the reticle transmittance. A step of converting the design data into a standard file format stream format (referred to as GDSII) and cif format as data written in mask CAD, and a reticle from the converted design data. The method is characterized by comprising a step of obtaining the transmittance and a step of storing the obtained reticle transmittance. In addition, a semiconductor exposure apparatus or an exposure method is characterized in that the reticle transmittance is obtained directly from data without measuring the reticle transmittance using an actual reticle.

  According to the present invention, as a countermeasure against a focus shift caused by lens expansion accompanying an increase in exposure load in a projection exposure apparatus, a method for obtaining a reticle transmittance with high accuracy and in a short time even for a pattern having any characteristics, That is, it is possible to provide a method for obtaining accurate reticle transmittance without impairing productivity.

It is a block diagram of the stepper which concerns on embodiment of this invention. It is a block diagram of the conventional stepper. It is explanatory drawing for demonstrating the method of measuring a reticle transmittance | permeability diagonally. It is explanatory drawing for demonstrating the method of measuring a reticle transmittance | permeability at random. It is explanatory drawing for demonstrating the method of measuring the inclination according to small measurement spot size. It is explanatory drawing for demonstrating the method of measuring the inclination according to measurement spot size size. It is explanatory drawing for demonstrating the transmittance | permeability measuring method of one chip | tip area | region. It is explanatory drawing for demonstrating the transmittance | permeability measuring method of four chip area | regions. It is explanatory drawing explaining the method of measuring the transmittance | permeability in the area | region narrowed down only to arbitrary areas.

  FIG. 1 is a block diagram of a stepper according to an embodiment of the present invention, which has a function of correcting exposure load from design data. The stepper includes an illumination optical system 1 of the projection exposure apparatus, a reticle 2 which is an original for actually measuring the reticle transmittance, and a desired pattern as an object to be exposed by reducing the reticle pattern to 1/5, for example. Projection optical system 3 for transferring the image onto the wafer, stage 4 for moving to a predetermined measurement spot for measuring the wafer and reticle transmittance, chuck 5 for supporting the wafer, and photodetector 6 for measuring the amount of light passing through the projection optical system. The CPU 7 has a CPU 7 that corrects the exposure load from the measured reticle transmittance, calculates the reticle transmittance from the design data to correct the exposure load, and controls the driving of the illumination optical system 1 and the stage 4.

  The reticle transmittance storage device 8 is a storage device for storing actually measured reticle transmittance data and reticle transmittance data calculated from the design data 9. A method of using the design data 9 will be described later.

  For reference, a block diagram of a conventional stepper is shown in FIG. A clear difference is that the conventional stepper has no linkage with the design data, and the reticle transmittance storage device 8 does not effectively use the reticle transmittance data calculated from the design data.

  Using the above configuration, when there is a pattern repeated at the same pitch as the sampling, it is possible to solve the conventional problem that the result returned as the reticle transmittance deviates from the actual value. Hereinafter, a method for measuring the reticle transmittance will be described in detail.

  As shown in FIG. 3, the first method is, for example, a conventional method in which the measurement is performed at a pitch of 0.2 mm in the X and Y directions. Measurement is performed at a pitch of 2 mm. Here, diagonally diagonal means a straight line that is diagonal to the four sides of the reticle and that is along a straight line that does not normally coincide with the diagonal line. At this time, the sampling in the X and Y directions is set so as to have a different interval with respect to the repeated pattern of the reticle. Alternatively, the measurement spot 10 may be diagonally inclined to the reticle, and the transmittance may be measured at different pitches such as 0.2 mm, 0.3 mm, 0.2 mm, and 0.3 mm. Also in this case, the sampling in the X and Y directions is set so that it overlaps with a different pattern without overlapping with the same pattern with respect to the pattern in which the reticle is repeated.

  The reticle transmittance, which is a characteristic of the entire reticle, is obtained from the above sampling and stored in the reticle transmittance storage device 8. Based on the obtained reticle transmittance, a CPU (exposure load correction device) 7 in FIG. 1 performs exposure load correction in combination with focus, lens distortion, and magnification as necessary, and feeds back to the projection optical system 3 in FIG. Projection exposure is performed.

  As shown in FIG. 4, the second method is, for example, a conventional method in which the measurement spot 10 is sequentially measured at a pitch of 0.2 mm in the X and Y directions. For example, the pitch of the measurement spot 10 is 0.2 to 1.0 mm. , And move randomly, combining the ones that have been moved sequentially in the X and Y directions separately, perform measurement without regularity, and do not overlap the same pattern for repeated patterns of the reticle The sampling operation is set so as to overlap with different patterns.

  As shown in FIG. 5, the third method is that the conventional measurement spot is fixed at, for example, 0.3 mmφ, and is variable from 0.3 mmφ to 1.0 mmφ, and depending on the size of the measurement spot, The inclination angle is changed. When the size of the measurement spot 11 viewed from the front is small, for example, 0.3 mmφ, the tilt angle θ1 (12) from the surface of the reticle 2 when viewed from the side is provided with a small tilt between 10 and 30 degrees. Measure reticle transmission. In this way, a large effective measurement area can be secured even when the measurement spot size is small. On the other hand, as shown in FIG. 6, when the size of the measurement spot 13 is large when viewed from the front, for example, 1.0 mmφ, the inclination angle θ2 (14) from the surface of the reticle 2 when viewed from the side is 70 to 90 degrees. The reticle transmission may be measured with a large slope between. This is because a large measurement area can be secured when the size of the measurement spot is large. By changing the size of the measurement spot in this way, sampling with the same pattern can be prevented.

  As shown in FIG. 7, the fourth method is to measure the transmittance by sampling only one chip area in a multi-faceted reticle composed of a plurality of the same chips, and calculate the reticle transmittance from the result. This is a calculation method. One chip region 15 here refers to, for example, an operation region of a semiconductor device and a region serving as a unit surrounded by a region up to the center (intermediate) of a scribe line to be ground by dicing. Further, the entire area of multiple imposition refers to the entire reticle surface including all these unit areas. These parameters are input to the apparatus in advance as an area to be sampled in advance and an entire area for multiple imposition. The reticle transmittance is calculated from the area ratio between one chip region 15 and the entire multi-faceted region, and is stored in the reticle transmittance storage device 8. Based on the obtained reticle transmittance, a CPU (exposure load correction device) 7 in FIG. 1 performs exposure load correction in combination with focus, lens distortion, and magnification as necessary, and feeds back to the projection optical system 3 in FIG. Projection exposure is performed.

  As shown in FIG. 8, the fifth method is to measure transmittance by sampling only four chip regions 16 in a multi-faceted reticle composed of a plurality of identical chips, and from the result, reticle transmittance is measured. Is a method of calculating By calculating from the area ratio of the four chip regions 16 and the entire area of the multiple imposition, the same exposure load correction can be performed.

  In the sixth method, as shown in FIG. 9, in a multi-faceted reticle composed of a plurality of identical chips, only the region 17 narrowed down to 1/4 of the entire reticle is sampled, and the transmittance is measured. This is a method of calculating reticle transmittance from the result. By calculating from the area ratio of the area 17 narrowed down to 1/4 of the entire reticle and the entire area of multiple imposition, the reticle transmittance on the entire surface of the reticle is obtained. The exposure load can be corrected.

Unlike the above method, the seventh method is a method of obtaining reticle transmittance without actually measuring transmittance. In order to obtain the design data 9 of FIG. 1, first, CAD design data for the reticle is generated for the reticle. Next, the design data is converted into a standard file format stream format (called GDSII) and cif format. Then, the reticle transmittance is obtained from the converted data from the occupied area of the light shielding film on the reticle, and is stored as reticle transmittance in the reticle transmittance storage device 8 of FIG. 1 via the LAN network. A CPU (exposure load correction device) 7 in FIG. 1 performs exposure load correction in combination with focus, lens distortion, and magnification as necessary based on the reticle transmittance stored in the data. The projection optical system 3 in FIG. give feedback. By doing so, it is possible to obtain the reticle transmittance in a short time without measuring the transmittance with an actual reticle. The reticle transmittance obtained without performing measurement in this way is compared with the reticle transmittance obtained by measuring by the above first to sixth methods, so that the accuracy of obtaining the reticle transmittance from CAD data can be increased or measured. In this case, it is possible to optimize the sampling in the process, and it is possible to further improve the accuracy.

  The present invention can be used for manufacturing a device that requires fine processing including a process using a photolithography technique using a reticle in a projection exposure apparatus such as a semiconductor substrate and a MEMS.

1 Illumination optical system 2 Reticle (original)
3 Projection Optical System 4 Moving Stage 5 Chuck 6 Photodetector 7 CPU (Exposure Load Correction Device)
8 Reticle transmittance storage device 9 Design data 10 Light quantity measurement spot (Point for measuring light quantity)
11 Measurement spot viewed from the front (small size, eg 0.3mmφ)
12 Inclination angle θ1 from reticle surface
13 Measurement spot as seen from the front (large size, for example, 1.0mmφ)
14 Inclination angle θ2 from reticle surface
15 One chip area for measuring transmittance 16 Four chip areas for measuring transmittance 17 Area narrowed down to 1/4 of the whole reticle for measuring transmittance

Claims (12)

A reticle transmittance measuring method using sampling in a projection exposure apparatus that projects a reticle pattern onto a wafer and obtains a predetermined pattern on the wafer,
In the sampling, the transmittance is measured diagonally diagonally of the reticle, and the pitch is set so that the repeated pattern provided on the reticle does not overlap the same pattern but overlaps different patterns. Reticle transmittance measurement method characterized by comprising: A reticle transmittance measuring method using sampling in a projection exposure apparatus that projects a reticle pattern onto a wafer and obtains a predetermined pattern on the wafer,
The sampling does not have a value in which the pitch in the X and Y directions is fixed, but by taking a value in a predetermined range at random, it overlaps the same pattern with respect to the repeated pattern provided on the reticle. A reticle transmittance measuring method characterized in that the operation is set so as to overlap different patterns. A reticle transmittance measuring method using sampling in a projection exposure apparatus that projects a reticle pattern onto a wafer and obtains a predetermined pattern on the wafer,
When the size of the measurement spot is variable and the size of the measurement spot is small within the variable range, the inclination angle θ1 from the reticle surface viewed from the side is a gentle inclination between 10 degrees and 30 degrees. When the transmittance is measured and the size of the measurement spot is large, the inclination angle θ2 from the reticle surface viewed from the side is a steep slope between 70 degrees and 90 degrees, and a different measurement spot size is used. A method for measuring a reticle transmittance, wherein the reticle transmittance is measured by the sampling. A reticle transmittance measuring method using sampling in a projection exposure apparatus that projects a reticle pattern onto a wafer and obtains a predetermined pattern on the wafer,
In the sampling, a reticle transmittance measuring method is characterized in that the reticle transmittance is calculated by measuring the transmittance of at least one chip region of a reticle having a plurality of same chips.   5. The reticle transmittance measuring method according to claim 4, wherein the one chip region is a unit region surrounded by an operation region of the semiconductor device and a region outside the semiconductor device in the vicinity of the center of the surrounding scribe line.   6. A projection exposure method comprising a step of correcting an exposure load based on the reticle transmittance obtained by the reticle transmittance measuring method according to claim 1.   7. The projection exposure method according to 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 measuring reticle transmittance using sampling, projecting a reticle pattern onto a wafer, and obtaining a predetermined pattern on the wafer,
In the sampling, the transmittance is measured diagonally diagonally of the reticle, and the pitch can be set so as to be different patterns without overlapping with the repeated patterns provided on the reticle. Projection exposure apparatus. A projection exposure apparatus capable of measuring reticle transmittance using sampling, projecting a reticle pattern onto a wafer, and obtaining a predetermined pattern on the wafer,
The sampling does not have a fixed value in the pitch in the X and Y directions, and does not overlap with a repeated pattern provided in the reticle by randomly taking a value in a predetermined range. A projection exposure apparatus characterized in that it can be set to have different patterns. A projection exposure apparatus capable of measuring reticle transmittance using sampling, projecting a reticle pattern onto a wafer, and obtaining a predetermined pattern on the wafer,
In the sampling, the size of the measurement spot is variable, and when the size of the measurement spot is small within the variable range, the inclination angle θ1 from the reticle surface viewed from the side is a gentle inclination close to 0 degrees. The reticle transmittance is measured, and when the size of the measurement spot is large, the reticle transmittance is measured at an inclination where the inclination angle θ2 from the reticle surface seen from the side is a steep slope close to 90 degrees, and the measurement is performed. A projection exposure apparatus, wherein reticle transmittance is measured by the sampling with the spot size changed. A projection exposure method using reticle design data,
Creating reticle design data; and
Converting the design data into a stream format or a cif format;
Obtaining reticle transmittance from the converted design data;
Storing the obtained reticle transmittance in a reticle transmittance storage device of a projection exposure apparatus;
Performing exposure load correction based on the stored reticle transmittance;
A projection exposure method comprising:   12. The projection exposure method according to claim 11, wherein the exposure load correction is at least one of focus correction, lens distortion correction, and magnification correction.

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