TW594432B - Method of reducing critical dimension bias of dense pattern and isolation pattern - Google Patents

Abstract

A method of reducing a critical dimension (""CD"") bias between a dense pattern and an isolation pattern is disclosed. The method includes a first step of providing a mask having a dense pattern, an isolation pattern and the other area of the mask is transparent, in which mask the dense pattern has a first opaque pattern and the isolation pattern has a second opaque pattern. The second step of the method is forming a virtual pattern around the isolation pattern, in which a distance between the virtual pattern and the isolation pattern is y, and the virtual pattern has a pattern line width x. By forming the virtual pattern around the isolation pattern, the flare effect of the isolation pattern is close to that of the dense pattern, thus the CD bias between a dense pattern and an isolation pattern is reduced, and the process window does not shrink.

Description

594432 V. Description of the invention (1) [Technical field to which the invention belongs] The present invention relates to a lithography process, and in particular to a method for eliminating the critical dimensional deviation of dense patterns and single patterns. [Prior art] In the case where circuit accumulation is required to be higher and higher, the design of the entire circuit element size is also forced to continue to shrink in size. The most important part of the entire semiconductor process is the photolithography process, which is related to the metal-Oxide-Semiconductor (M0S) element structure.

For example, the pattern of each layer of the film (Pat tern) and the region doped with impurities (D opa n t s) are determined by the lithography step. Moreover, whether the integration of components in the entire semiconductor industry can be continued to a smaller line width below 0 · 18 mm depends on the development of lithography process technology. Generally speaking, on the same photomask, there are usually a single (Isolation) pattern area and a dense (Dense) pattern area. For example, for a memory-only memory, static and random access memory, flash memory, or dynamic random access memory and logic

The system on a chip (System On a Chlp) is usually a dense pattern in the memory area of the film, and a single pattern in the logic circuit area. However, j performs the exposure step of transferring dense patterns and single-patterns to the photoresist layer =, because the so-called astigmatism effect (FUre Effect) will occur, the critical dimensions of the pattern pattern and the exposure pattern in the single pattern region deviate. , Which seriously affects the efficiency of components

10719twf.ptd $ 7 pages 594432 V. Description of the invention (2) The conventional method to solve this astigmatism effect is Optical Proximity Correction (0PC), which is to reduce the original pattern to be transferred, reducing Or increase the line width of the original pattern to make the correction so that the line width of the pattern exposed in the dense pattern area and the isolated pattern area remains the same. However, as the effect of astigmatism caused by different exposure machines is not the same, different correction values must be added to the original pattern. In addition, the modified original pattern will make the process window of the single pattern area and the dense pattern area inconsistent, which will make the lithography process difficult. In addition, because the astigmatism effect is also related to the pattern density, a good key size uniformity cannot be obtained even with the optical proximity correction method. [Summary of the Invention] In view of this, an object of the present invention is to provide a method for eliminating the critical dimension deviation of a dense pattern and a single pattern, which can reduce the critical dimension deviation of a dense pattern and a single pattern caused by the astigmatism effect. The invention provides a method for eliminating the critical dimension deviation between a dense pattern and a single pattern. This method first provides a photomask. The mask is at least divided into a dense pattern area and a single pattern area. Each of the dense pattern area and the single pattern area is provided with a mask. Opaque film pattern, and other parts of the mask are light-transmitting areas. Then, a virtual pattern is formed around the single pattern area, and a distance y is formed between the virtual pattern and the first pattern area, and the virtual pattern has a pattern line width X. The above-mentioned distance y is at least 0.1 micron, the pattern line width X is 0.5 micron $ X S 10 cm, and the light transmittance of the virtual pattern is less than 100%.

10719twf.ptd Page 8 594432 V. Description of the invention (3) The present invention forms a virtual pattern around a single pattern area, so that the single pattern area and the dense pattern area receive the same astigmatism effect, which can be the key size of the single pattern Deviation, but also does not reduce the size of the compact key. The size of the key is divided into the light-transmitting area of the project area, which makes the gloss rate high. Then the distance between the masks is 3%. (Invention provides a method of elimination. This method first provides a mask in addition to the relationship between the dense pattern and a single pattern. This mask reaches the case area and the single pattern area. The dense pattern area and The single image has an opaque film pattern, and the other parts of the mask are not. An open area is formed around the single pattern area, and the open opaque area is as early as 0.5 micrometers away from the pattern area. Distance z. $ Y $ 10 cm, and the open area is transparent because of the open area around the single pattern area, so that the single pattern area and the dense pattern area receive the same astigmatism effect, which can reduce the key size deviation between the dense pattern and the single pattern. In order to make the above and obviously understandable of the present invention, a detailed description is given below in detail as follows: [Embodiment] The first embodiment, FIG. 1A to FIG. 1B, are as follows: The mask of the first embodiment is shown separately. First, please refer to FIG. 1A. The purpose, features, and advantages of the mask can be further implemented in accordance with the accompanying drawings. A light 10 0. This mask 100

10719twf.ptd Page 9 594432 V. Description of the invention (4) The material can be quartz glass. The mask 100 is divided into at least a dense pattern area 102 and a single pattern area 104. Opaque film patterns are formed in the dense pattern area 102 and the single pattern area 104. Among them, the dense pattern area 102 refers to an area with dozens of opaque films (19 in the figure are taken as an example), and the single pattern area 104 refers to an area plated with only a few opaque films (picture Take 3 as an example). The other parts of the photomask 100 are transparent areas. When the exposure process is performed with the photomask 100 in FIG. 1A, if the key pattern of the exposure pattern of the dense pattern area 10 2 is, for example, line width = 0. 3 8 / pitch = 0. 2, such line width / The exposure energy of the pitch is, for example, 90% from the main light source and 10% from the astigmatism effect. When the single pattern area 104 is exposed with the same light source, the exposure energy compensated by the astigmatism effect will be greater than 10% because the single pattern area 104 is surrounded by empty light-transmitting areas, which may make the single pattern area 104 The key size of the exposure pattern becomes line width = 0.35 / space = 0.23. As a result, the critical dimensions of the exposed patterns in the dense pattern region 102 and the single pattern region 104 may be deviated. Next, referring to FIG. 1B, in order to solve the above-mentioned problem, the method for eliminating the key dimension deviation between the dense pattern and the single pattern of the present invention is to form a dummy pattern 106 around the single pattern region 104. There is a distance y between the dummy pattern 106 and the single pattern region 104, and the dummy pattern 106 has a pattern line width X. The distance y is, for example, at least 0.1 micrometer, and the pattern line width X is, for example, 0.5 micrometers. The light transmittance of the virtual pattern 106 is, for example, less than 100%. When the exposure process is performed with the photomask 100 in FIG. 1B, the same key pattern of the exposure pattern in the dense pattern area 1 2 is, for example, line width = 0. 3 8 / space

10719twf.ptd Page 10 594432 V. Description of the invention (5) 20 0.2, the exposure energy that exposes such line width / space is, for example, 90% from the main light source and 10% from the astigmatism effect. When a single pattern region 104 is exposed with the same light source, since a virtual pattern 106 is formed around the single pattern region 104, the virtual pattern 106 can maintain the exposure energy compensated by the astigmatism effect by 10%, so Therefore, the critical size of the dense pattern area 102 can be the same as that of the exposure pattern in the single pattern area 104. Moreover, by adjusting the light transmittance of the virtual pattern, the exposure energy compensated by the astigmatism effect can also be adjusted. In the present invention, by forming a virtual pattern around the single pattern region 104, the single pattern region 104 and the dense pattern region 102 receive the same astigmatism effect, which can reduce the critical dimensional deviation between the dense pattern and the single pattern, and also Does not reduce process margin. Second Embodiment FIG. 2A to FIG. 2B are schematic diagrams showing a conventional photomask and a photomask according to the second embodiment of the present invention, respectively. First, please refer to FIG. 2A to provide a photomask 2 0 0. The material of the mask 2 0 0 can be quartz glass. The mask 200 is at least divided into a dense pattern area 202 and a single pattern area 204. A denser opaque pattern is formed in the dense pattern region 202. A single-pattern region 204 is formed with a light-tight film pattern having a smaller density. That is, the dense pattern area 202 refers to an area having dozens of opaque films (19 are taken as an example in the figure), and the single pattern area 204 refers to a plate with only a few opaque films. Area (3 in the figure as an example). The mask 200 is opaque except for the dense pattern area 202 and the single pattern area 204.

10719twf. If the spacing is 0.2, the exposure energy of such line width / spacing exposure is, for example, 90% from the main light source and 10% from the astigmatism effect. When the single pattern area 204 is exposed with the same light source, the exposure energy compensated by the astigmatism effect will be less than 10% because the single pattern area 204 is surrounded by opaque areas. The key size of the exposure pattern becomes line width = 0 · 4 2 / pitch two 0.16. As a result, the critical dimensions of the exposure patterns in the dense pattern region 102 and the single pattern region 104 are deviated. Next, referring to FIG. 2B, in order to solve the above-mentioned problem, the method for eliminating the key dimension deviation between the dense pattern and the single pattern of the present invention is to form an open region 206 around the single pattern region 204. The open area 206 is a distance z from the light-opaque area of the mask 200 to the single pattern area 204. Among them, the distance z is, for example, about 0.5 micrometers. The light transmittance of the dummy pattern 106 is, for example, more than 3%. When the exposure process is performed with the mask 200 of FIG. 2B, similarly, if the key pattern of the exposure pattern of the dense pattern region 202 is, for example, line width = 0. 3 8 / pitch 0.2, the exposure is Such line width / spacing exposure energy is, for example, 90% from the main light source and 10% from the astigmatism effect. When a single pattern area 204 is exposed with the same light source, since an open area 2 06 is formed around the single pattern area 104, the open area 2 06 can maintain the exposure energy compensated by the astigmatism effect by 10%, so It is possible to reduce the key size difference between the exposed pattern in the dense pattern region 202 and the single pattern region 204. Moreover, by adjusting the light transmittance of the virtual pattern, it can also be adjusted by the astigmatism effect.

10719twf. Ptd Page 12 594432 V. Description of the invention (7) Exposure energy. In the present invention, the open area 206 is formed around the single pattern area 204, so that the single pattern area 204 and the dense pattern area 202 receive the same astigmatism effect, and the key size deviation between the dense pattern and the single pattern can be reduced, and Nor does it reduce the process margin. In short, the present invention is to form a virtual pattern (or an open area) around a single pattern area so that the single pattern area and the dense pattern area are subjected to the same astigmatism effect, which can avoid the critical dimensions of the dense pattern and the single pattern caused by the scattering effect Deviation, which is conducive to reducing the size of the wire, reducing the line width spacing ratio, and obtaining a larger common process space of a single pattern area / dense pattern area. < Although the present invention has been disclosed as above with a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art can make some changes and decorations without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be determined by the scope of the appended patent application.

10719twf. Ptd Page 13 594432 Brief description of the drawing * Figure 1 A is a schematic diagram showing a conventional photomask. FIG. 1B is a schematic diagram illustrating a photomask according to the first embodiment of the present invention. FIG. 2A is a schematic diagram illustrating another conventional photomask. FIG. 2B is a schematic diagram showing a photomask according to the second embodiment of the present invention. [Illustration of drawing symbols] 1 0 0: photomask 102, 202: dense pattern area 104, 204: single pattern area 1 0 6: virtual pattern 2 0 6: open area X: pattern line width y, z: distance

10719twf. Ptd Page 14

Claims (1)

594432 VI. Scope of patent application 1. A method for eliminating the critical dimension deviation between a dense pattern and a single pattern, the method includes: providing a photomask, the mask is at least divided into a dense pattern area and a single pattern area, and the dense pattern area An opaque film pattern is provided separately from the single pattern area, and other parts of the photomask are transparent areas; and a virtual pattern is formed around the single pattern area, and the virtual pattern is spaced from the single pattern area. A distance y, and the virtual pattern has a pattern line width X. 2. A method for eliminating a critical dimension deviation between a dense pattern and a single pattern as described in item 1 of the scope of the patent application, wherein the distance y is at least 0.1 micrometer. 3. The method for eliminating the key dimension deviation of a dense pattern from a single pattern as described in item 1 of the scope of patent application, wherein the line width X of the pattern is 0.5 micrometers $ X $ 10 cm. 4. The method for eliminating the critical dimension deviation between a dense pattern and a single pattern as described in item 1 of the scope of patent application, wherein the transmittance of the virtual pattern is less than 100%. 5. A method for eliminating key dimension deviation between a dense pattern and a single pattern, the method comprising: providing a photomask, the mask is at least divided into a dense pattern area and a single pattern area, and the dense pattern area and the single pattern area are respectively An opaque film pattern is provided, and other parts of the reticle are opaque areas; and an open area is formed around the single pattern area, and the open area makes the opaque area of the reticle to the single pattern The zones are separated by a distance z. 10719twf. Ptd Page 15 594432 6. Scope of patent application 6. The method for eliminating the critical dimension deviation of dense patterns and single patterns as described in item 5 of the scope of patent application, wherein the distance z is 0.1 micron $ z $ 1 0 cm. 7. The method for eliminating the critical dimension deviation between a dense pattern and a single pattern as described in item 5 of the scope of patent application, wherein the light transmittance of the open area is greater than 3%. 10719twf.ptd Page 16