TWI585512B - Method for improving pattern fidelity - Google Patents

Description

Method of improving the precision of a pattern

This invention relates to a semiconductor process and, more particularly, to a method of enhancing the precision of a pattern.

With the rapid development of semiconductor process technology, in order to improve the speed and performance of components, the size of the entire circuit components must be continuously reduced, and the accumulation of components must continue to increase. In general, lithography processes play a pivotal role in the overall process as semiconductors tend to shrink the design of circuit components.

The lithography process first forms a layer of photosensitive photoresist on the surface of the wafer. Then, the photoresist exposure step and the development step are sequentially performed to transfer the desired pattern to the photoresist material layer on the surface of the wafer by using the pattern on the photomask to form a desired photoresist pattern.

In the tendency of the line width of the element and the pitch to be reduced, it is easy to cause a deviation in the pattern transfer in the exposure step, that is, a so-called optical proximity effect (OPE). Since the accuracy of lithography imaging directly affects the yield of the product, in order to solve this problem, some methods for improving the resolution of the reticle are constantly being proposed. For example, using optical proximity correction (optical Proximity correction (OPC) is a modification of the reticle pattern whose main purpose is to eliminate the critical dimensional deviation caused by the optical proximity effect, that is, to reduce the deviation between the photoresist pattern and the reticle pattern.

In general, key patterns can be optimized by manual OPC (manual OPC). For example, some pattern blocks are placed on the reticle pattern, and according to the desired result pattern, the position of each pattern block is checked to find an appropriate pattern block placement position. This will cost a lot of time and process costs.

The invention provides a method for improving the precision of a pattern, which can improve the precision of the pattern and reduce the time for establishing the optical proximity correction model, which can help save the process cost.

The method of improving the precision of a pattern of the present invention comprises the following steps. Provide the target pattern. The target pattern is decomposed into a plurality of division patterns. A plurality of photoresist intensity distributions are respectively generated by the plurality of division patterns. A plurality of photoresist intensity distributions of the plurality of division patterns are processed to obtain a photoresist intensity distribution image. A high-sensing area and an insufficient-intensity area are defined according to the photoresist intensity distribution image. Correcting an insufficient intensity region of the photoresist intensity distribution image. The resulting pattern is obtained from the corrected photoresist intensity distribution image.

In an embodiment of the invention, the step of decomposing the target pattern into a plurality of division patterns comprises: decomposing the target pattern into a main pattern and a secondary pattern.

In an embodiment of the invention, the step of processing the plurality of photoresist intensity distributions of the plurality of split patterns to obtain the photoresist intensity distribution image comprises: placing the main pattern The photoresist intensity distribution superimposes the photoresist intensity distribution of the secondary pattern.

In an embodiment of the invention, the step of defining the high photosensitive region and the insufficient intensity region according to the photoresist intensity distribution image includes: comparing the photoresist intensity distribution image with the photoresist intensity distribution image of the target pattern.

In an embodiment of the invention, the step of modifying the intensity-deficient region of the photoresist intensity distribution image includes performing manual OPC correction.

In an embodiment of the invention, the step of modifying the intensity-deficient region of the photoresist intensity distribution image includes performing model OPC correction.

In an embodiment of the invention, the target pattern is a pattern having an end cap structure, the main pattern is a linear pattern, and the secondary pattern is an island pattern. The "NOT" Boolean operation is used to superimpose the photoresist intensity distribution of the main pattern with the photoresist intensity distribution of the secondary pattern.

In an embodiment of the invention, the target pattern is a pattern having an end cap structure, the main pattern is a line pattern, and the secondary pattern is a hole pattern. The "AND" Boolean operation is used to superimpose the photoresist intensity distribution of the main pattern with the photoresist intensity distribution of the secondary pattern.

In the method for improving the precision of a pattern of the present invention, the photoresist intensity distribution image obtained by superposing the photoresist intensity distributions of the plurality of divided patterns and the photoresist intensity distribution image of the initial pattern are compared with each other to perform OPC correction. By eliminating complex computational inferences, it is possible to reduce the time required to establish an optical proximity correction model while improving the precision of the pattern, which can help to save process costs.

In order to make the above features and advantages of the present invention more apparent, the following is a special The embodiments are described in detail below in conjunction with the drawings.

S100, S200, S202, S204, S206, S208, S210, S212, S214, S216, S218, S220, S222, S224, S226, S228, S300, S400, S500‧‧

502‧‧‧resist pattern

504‧‧‧mask pattern

506‧‧‧ pattern block

600‧‧‧ target pattern

602‧‧‧ main pattern

604‧‧‧ secondary pattern

900, 906‧‧‧Revision pattern

902, 908‧‧‧ result pattern

904, 910‧‧‧ simulation pattern

1 is a flow chart showing the steps of fabricating a reticle in accordance with an embodiment of the present invention.

FIG. 2 is a flow chart showing the steps of the reticle compositing process in accordance with an embodiment of the present invention.

3 is a photographic view of a photoresist pattern on a wafer obtained from a reticle having an initial pattern.

FIG. 4 is a design diagram of a target pattern.

FIG. 5 is a schematic diagram showing a basic accuracy improvement scheme of the initial pattern.

FIG. 6A is a schematic diagram of a target pattern.

FIG. 6B is a schematic diagram of a main pattern.

FIG. 6C is a schematic diagram of a secondary pattern.

7A and 7B respectively show the photoresist intensity distribution of the split pattern.

FIG. 8A illustrates a photoresist intensity distribution image processed by superposition.

FIG. 8B illustrates a photoresist intensity distribution image of the initial pattern.

FIG. 9A is a schematic diagram showing the layout of a photomask according to the existing OPC.

9B is a schematic view showing the layout of a reticle of an OPC according to the present invention.

Figure 10 is a photographic view of a photoresist pattern on a wafer obtained by a reticle obtained by the method of the present invention.

1 is a flow chart showing the steps of fabricating a reticle in accordance with an embodiment of the present invention. FIG. 2 is a flow chart showing the steps of the reticle compositing process in accordance with an embodiment of the present invention.

Referring to FIG. 1, in step S100, a design pattern is provided. This design pattern is the original drawing of the original designed line layout pattern, which is, for example, a geometric pattern used to describe the integrated circuit layout to be transferred to the wafer. In one embodiment, the design pattern includes information such as geometric patterns of different critical dimensions, different pattern densities, and different line width spacings. Hereinafter, a pattern having an end cap shape is produced as an example, but the present invention is not limited thereto.

Next, in step S200, a mask synthesis process is performed. That is, the optical proximity effect correction (OPC) of the reticle is performed according to the design pattern. The original pattern to be exposed on the semiconductor substrate of the wafer is calculated and corrected by using a computer and a software package operation, and the resulting image is input into a computer for archiving. The resulting pattern based on optical proximity effect correction (OPC) is fabricated on a reticle through which the pattern of the light beam projected onto the semiconductor substrate can be nearly identical to the original pattern. The pattern on the reticle originally created is hereinafter referred to as the initial pattern. Here, the photomask synthesizing process of the present invention will be further described based on Fig. 2 .

Referring to FIG. 2, in step S202, an initial pattern is provided. This initial pattern has a problem of accuracy based on the initial pattern produced by the design pattern. The initial pattern was transferred to the photoresist layer to obtain a photoresist pattern. 3 is a photographic view of a photoresist pattern on a wafer obtained from a reticle having an initial pattern. As shown in FIG. 3, the end cap structure of the photoresist pattern on the wafer has a sharp shape, and the end cap structure is outside. The shape is preferably an arc shape. Therefore, the photoresist pattern on the wafer has a problem of accuracy, indicating that the design pattern on the mask needs further correction.

In step S204, a target pattern is provided. The target pattern refers to a pattern to be exposed on a semiconductor substrate of a wafer. FIG. 4 is a design diagram of a target pattern. As shown in FIG. 4, an end cap structure having a circular arc shape is used as a target pattern.

In step S206, the initial pattern is analyzed. That is, the difference between the initial pattern and the target pattern is found by comparing the initial pattern with the target pattern. In this step, the initial pattern deficiencies are found based on the photoresist pattern transferred from the initial pattern onto the wafer compared to the target pattern.

In step S208, a key area of the initial pattern is defined. Figure 5 is a schematic diagram showing the basic accuracy improvement scheme of the initial pattern. That is, after finding the difference between the initial pattern and the target pattern, the area (key area) to be corrected by the initial pattern is defined based on these differences. That is, the resist pattern 502 is compared with the target pattern similar to that shown in FIG. 4 to find the area to be corrected.

In step S210, a basic accuracy improvement scheme is provided. A modification of the difference between the initial pattern and the target pattern is provided according to the key area of the initial pattern. As shown in FIG. 5, some of the pattern blocks 506 are placed on the reticle pattern 504 to find an improvement scheme to achieve better contour results. If an accuracy improvement scheme is found, the initial pattern is corrected by manual OPC (step S226) or model OPC (step S228), and the subsequent step S300 is performed (mask underline: after the pattern is written into the mask, the mask is The pattern on the top is transferred to the photoresist layer). If the accuracy improvement scheme is not found, the method for improving the precision of the pattern described in the present invention is performed (step S212 to step) S224) to regenerate the target pattern.

In step S212, the target pattern is decomposed into a plurality of division patterns. It is considered to use a combination of various patterns to generate a target pattern. Step S212 will be exemplified below with reference to FIGS. 6A to 6C. Figure 6A is a schematic view of the target pattern. Fig. 6B is a schematic view of the main pattern. A schematic view of the secondary pattern is shown in Figure 6C. The target pattern 600 shown in FIG. 6A is, for example, a pattern having an end cap shape, and the target pattern 600 can be obtained by synthesizing a plurality of division patterns. In this step, the target pattern 600 shown in FIG. 6A is decomposed into the main pattern 602 shown in FIG. 6B and the sub-pattern 604 shown in FIG. 6C. The main pattern 602 is, for example, a line pattern; the secondary pattern 604 is, for example, an island pattern or a hole pattern.

In step S214, a plurality of photoresist intensity distributions are generated. 7A and 7B respectively show the photoresist intensity distribution of the split pattern. A plurality of splitting patterns are used to generate a plurality of photoresist intensity distributions by computer simulation. That is, the photoresist intensity distribution shown in FIG. 7A is generated from the main pattern 602 shown in FIG. 6B; the photoresist intensity distribution shown in FIG. 7B is generated from the main pattern 604 shown in the pattern 6C.

In step S216, a plurality of photoresist intensity distributions of the plurality of division patterns are processed to obtain a photoresist intensity distribution image. Fig. 8A shows an image of a photoresist intensity distribution subjected to superposition processing. The photoresist intensity distribution image shown in Fig. 8A is obtained by superimposing the photoresist intensity distribution of the main pattern shown in Fig. 7A on the photoresist intensity distribution of the secondary pattern shown in Fig. 7B. The processing of the plurality of photoresist intensity distributions of the plurality of division patterns is obtained by calculation using a computer program. When the secondary pattern 604 is an island pattern, the "NOT" Boolean operation is used to stack the photoresist intensity distribution of the main pattern and the photoresist intensity distribution of the secondary pattern. Add together. When the secondary pattern 604 is a hole pattern, the "AND" Boolean operation is used to superimpose the photoresist intensity distribution of the main pattern and the photoresist intensity distribution of the secondary pattern.

In step S218, a high photosensitive area is defined in accordance with the photoresist intensity distribution image. FIG. 8B illustrates a photoresist intensity distribution image of the initial pattern. Comparing the photoresist intensity distribution image shown in FIG. 8A with the photoresist intensity distribution image of the initial pattern shown in FIG. 8B, indicating that the two are different, thereby finding and defining a high sensitivity region, wherein A darker area indicates an area of insufficient strength. The difference between the photoresist intensity distribution image shown in FIG. 8A and the photoresist intensity distribution image of the initial pattern shown in FIG. 8B is a position where correction is required.

In step S220, pattern correction guidance information is generated to confirm the position that needs to be corrected.

In step S222, manual correction is performed. Manually correct the area of the intensity of the photoresist intensity distribution image. Based on the pattern correction guide information, the patch pattern is added to the portion to be corrected, and then the influence of each block on the contour performance of the pattern is checked.

In step S224, model OPC guidance is performed. The model OPC guide is used to correct the insufficient intensity region of the photoresist intensity distribution image. According to the guide information of the pattern correction, the correction is performed by the OPC guide in the database. That is, in step S224, a guide pattern of the model OPC is generated, and the guide pattern is added to the target pattern to be corrected by the model OPC.

In step S226, manual OPC correction is performed to initialize the pattern, and Result pattern.

In step S228, model OPC correction is performed to initialize the pattern to obtain a resulting pattern.

After the end of step S200, step S300 follows.

In step S300, the mask is taken offline. The resulting pattern is written on the reticle to create a patterned reticle. The method of writing the resulting pattern on the reticle is, for example, performing a writing step including performing an electron beam or a laser beam. Thereafter, the pattern on the reticle is transferred to the photoresist layer to form a plurality of photoresist patterns correspondingly in the photoresist layer. The method of transferring the pattern on the photomask to the photoresist layer is, for example, an exposure step and a development step, and this step is a technique well known to those skilled in the art, and thus will not be described herein.

In step S400, the photoresist pattern on the wafer is inspected. If the photoresist pattern on the wafer meets the requirements, the fabrication of the mask is completed (step S500: completion); if the photoresist pattern on the wafer does not meet the requirements and the defect is correctable, return to step S200 to correct defect.

FIG. 9A is a schematic diagram showing the layout of a photomask according to the existing OPC. 9B is a schematic view showing the layout of a reticle of an OPC according to the present invention. In FIGS. 9A and 9B, the pattern drawn by the thin broken line indicates the correction patterns 900, 906 obtained by adding the correction portion to the base pattern; the pattern drawn by the thin solid line indicates that the correction pattern 900, 906 after the OPC calculation, the result pattern 902, 908 is obtained, that is, the pattern is written on the reticle; the pattern drawn by the thick solid line indicates the simulated pattern 904 obtained by the result pattern 902, 908 being simulated by the computer program. 910, that is, by The resulting profile of the photoresist pattern transferred to the wafer is simulated. As shown in FIG. 9A, with the conventional OPC correction method, the correction pattern 900 merely adds some block patterns at the end of the base pattern, and the correction pattern 906 as shown in FIG. 9B cannot be obtained. In Fig. 9B, the correction pattern 906 is obtained by the above steps S210 to S224 of the present invention; and the result pattern 908 is obtained by the above steps S226 to S228 of the present invention. Comparing the simulated pattern 904 and the simulated pattern 910 in FIGS. 9A and 9B, the method of the present invention can obtain a pattern in which the end cap structure has a circular arc shape, that is, a pattern with better precision. Figure 10 is a photographic view of a photoresist pattern on a wafer obtained by a reticle obtained by the method of the present invention. Comparing Figures 3 and 10, the end cap structure of Figure 3 has a sharp shape, while the end cap structure of Figure 10 has a circular arc shape. The method of the present invention can obtain a pattern with better precision.

In the method for improving the precision of the pattern of the present invention, the photoresist intensity distribution image obtained by superimposing the photoresist intensity distributions of the plurality of division patterns is compared with the photoresist intensity distribution image of the initial pattern, and can be found and defined. A highly sensitive area by which the graphics are corrected and the resulting image is obtained. Therefore, the error between the mask pattern and the photoresist pattern can be reduced, thereby improving the precision of the pattern, and saving patterning and developing time.

In addition, the method of the present invention utilizes existing equipment and software packages to obtain a correction pattern formed on the reticle and establish an optical proximity correction model, thereby eliminating complicated computational inferences, thereby reducing the credibility of the lithography process and reducing Establishing the computational time of the optical proximity correction model can help save process costs.

In summary, in the method for improving the precision of the pattern of the present invention, The photoresist intensity distribution image in which the photoresist intensity distribution of the split pattern is superimposed and the photoresist intensity distribution image of the initial pattern are compared with each other to perform OPC correction, thereby eliminating complicated arithmetic inference, thereby improving the precision of the pattern. At the same time, it can reduce the time to establish an optical proximity correction model, which can help save process costs.

Although the present invention has been disclosed in the above embodiments, it is not intended to limit the invention, and any one of ordinary skill in the art can make a few changes and refinements without departing from the spirit and scope of the invention. Therefore, the scope of the invention is defined by the scope of the appended claims.

S202, S204, S206, S208, S210, S212, S214, S216, S218, S220, S222, S224, S226, S228‧‧ steps

Claims (9)

A method for improving pattern precision, comprising: providing a target pattern; decomposing the target pattern into a plurality of division patterns; respectively generating a plurality of photoresist intensity distributions by the plurality of division patterns; processing the plurality of division patterns The plurality of photoresist intensity distributions obtain a photoresist intensity distribution image; defining a high photosensitive region and an insufficient intensity region according to the photoresist intensity distribution image; and correcting the insufficient intensity of the photoresist intensity distribution image And obtaining a result pattern according to the corrected photoresist intensity distribution image, wherein the step of defining the high photosensitive region and the insufficient intensity region according to the photoresist intensity distribution image comprises: displaying the photoresist intensity distribution image The photoresist intensity distribution images of the target pattern are compared with each other. The method of improving pattern precision according to claim 1, wherein the step of decomposing the target pattern into the plurality of division patterns comprises: decomposing the target pattern into a main pattern and a secondary pattern. The method for improving pattern precision according to claim 2, wherein the processing the plurality of photoresist intensity distributions of the plurality of division patterns to obtain the photoresist intensity distribution image comprises: The photoresist intensity distribution of the main pattern superimposes the photoresist of the secondary pattern Degree distribution. The method of improving pattern precision according to claim 1, wherein the step of correcting the insufficient intensity region of the photoresist intensity distribution image comprises performing manual OPC correction. The method of improving pattern precision according to claim 1, wherein the step of correcting the insufficient intensity region of the photoresist intensity distribution image comprises performing model OPC correction. The method of improving pattern precision according to claim 2, wherein the target pattern is a pattern having an end cap structure, the main pattern is a line pattern, and the secondary pattern is an island pattern. The method for improving the precision of a pattern according to claim 6, wherein the "NOT" Boolean operation is used to superimpose the photoresist intensity distribution of the main pattern with the photoresist intensity distribution of the secondary pattern. . The method of improving pattern precision according to claim 2, wherein the target pattern is a pattern having an end cap structure, the main pattern is a line pattern, and the secondary pattern is a hole pattern. The method for improving the precision of a pattern according to claim 8, wherein the "AND" Boolean operation is used to superimpose the photoresist intensity distribution of the main pattern and the photoresist intensity distribution of the secondary pattern. together.