CN1354494A - Lithographic Fabrication Method That Reduces Proximity Effects - Google Patents

Abstract

A photoetching process for reducing proximity effect includes providing a wafer, forming the first photoresist on it, exposing and developing with a photomask to form the first photoresist, patterning the first photoresist, forming the first element pattern and the first virtual pattern on the photomask, transferring the first element pattern and the first virtual pattern to the first photoresist, and forming the second element pattern and the second virtual pattern on the first photoresist. A second photoresist is formed on the patterned first photoresist. And carrying out a second exposure and development manufacturing process, removing part of the second photoresist, and only exposing the second element pattern of the first photoresist.

Description

Lithographic Fabrication Method That Reduces Proximity Effects

The invention relates to a photolithography manufacturing method, and in particular to a photolithography manufacturing process capable of reducing the proximity effect.

Under the condition that circuit integration is required to be higher and higher, the design of the size of the entire circuit element is also forced to advance in the direction of continuous reduction in size. The most important part of the entire semiconductor manufacturing process is the photolithography (Photolithography) manufacturing process, which is related to the structure of Metal-Oxide-Semiconductor (MOS) components, such as: the pattern of the prepared film (Pattern), And the regions doped with impurities (Dopants) are determined by the step of photolithography. In addition, whether the component integration level of the entire semiconductor industry can continue to be smaller than 0.18μm is also determined by the development of photolithography manufacturing technology. In order to meet this requirement, some methods for improving the resolution of photomasks have been continuously proposed, such as Optical Proximity Correction (Opcical Proximity Correction, OPC) and Phase Shift Mask (Phase ShiftMask, PSM) and so on.

The purpose of OPC is to eliminate the critical dimension deviation caused by the proximity effect. Proximity Effect is that when the light beam passes through the pattern on the photomask and projects on the wafer, on the one hand, the beam will be enlarged due to the phenomenon of scattering of the light beam. On the other hand, the light beam will pass through the photoresist layer on the surface of the wafer and reflect back through the semiconductor substrate of the wafer, resulting in interference phenomenon, so the exposure will be repeated, and the actual exposure amount on the photoresist layer will be changed. .

Due to the weak light intensity and insufficient exposure at the edge of the exposure pattern, it is easy to cause the pattern edge pattern formed on the photoresist to be distorted or shortened compared with the pattern on the actual photomask , and affect the accuracy of the key dimension of the edge of the exposure pattern, resulting in errors in line width or pattern transfer.

Therefore, in general, in order to reduce the influence of the proximity effect on the edge of the exposure pattern, an auxiliary pattern is usually formed on the edge of the exposure pattern on the photomask. 1A and 1B are schematic top views of a conventional photomask with auxiliary patterns. 1A is a schematic top view of a region with a higher pattern density on the photomask 100 , and FIG. 1B is a schematic top view of a photomask with a single pattern region on the photomask 100 .

Please refer to FIG. 1A , because the edge pattern 102a of the region 102 with a higher pattern density is weaker than the light intensity received by the central dense pattern 102b during the pattern transfer exposure step, so an additional light will be added beside the edge pattern 102a. Auxiliary pattern 106 .

Similarly, please refer to FIG. 1B , on the same photomask 100 , the single pattern 104 is compared with the dense pattern area 102 . The required exposure light intensity is stronger. In order to make the required exposure light intensity of all patterns in the same photomask equal, an auxiliary pattern 106 is added respectively on both sides of the single pattern 104, so that the pattern density of the single pattern 104 It is equivalent to the density of the dense pattern area 102 .

In order to prevent the auxiliary pattern 106 from being transferred to the photoresist when the pattern is transferred, the line width b of the general auxiliary pattern 106 is smaller than the line width a of the device pattern (including the dense pattern area 102 and the single pattern 104). (that is, a > b), and in order to make the outline of the edge pattern 102a or the single pattern 104 more obvious, the distance D between the auxiliary pattern 106 and the edge pattern 102a and the single pattern 104 needs to be about the same as the exposure wavelength ( ) or Smaller to achieve auxiliary effect.

However, as the integration of components becomes higher and higher, the line width becomes smaller and smaller, and the component patterns become more complex, the line width of the component patterns on the photomask is also reduced, and the line width of the auxiliary pattern is also narrower. The manufacturing difficulty of the photomask is thus increased. In addition, since the distance between the edge pattern 102a of the auxiliary pattern 106 and the single pattern 104 needs to be about the same as the exposure wavelength, when the device pattern becomes more and more complex and dense, it is necessary to reserve a space on the photomask that is as wide as the exposure light wavelength. Forming the auxiliary pattern further increases the difficulty and cost of manufacturing the photomask. In addition to the great difficulty in manufacturing the photomask, it is also extremely difficult to debug defects in the auxiliary pattern after the photomask is manufactured.

Therefore, the object of the present invention is to provide a photolithographic fabrication method which can reduce the proximity effect.

In order to achieve the above object, the present invention provides a photolithographic manufacturing method, comprising: providing a wafer, forming a first photoresist on it, and then using a photomask to perform the first exposure and development manufacturing process, patterning The first photoresist, wherein the first element pattern and the first dummy pattern are formed on the photomask, and the first dummy pattern is located at the periphery of the first element pattern, and the first element pattern on the photomask The first dummy pattern is transferred to the first photoresist, and the second device pattern and the second dummy pattern are formed corresponding to the first photoresist. Next, a second photoresist is formed on the patterned first photoresist. Finally, a second exposure and development process is performed to remove part of the second photoresist and only expose the second element pattern of the first photoresist.

According to a preferred embodiment of the present invention, wherein the line width of the first element pattern is the same as the line width of the first dummy pattern, and a density of the first element pattern is the same as a density between the first dummy pattern and the first element pattern same.

Since the line width of the first element pattern on the photomask is the same as the line width of the first dummy pattern, it is possible to reduce the difficulty of making the photomask as the line width of the element becomes smaller and smaller, and the formation of the photomask The subsequent inspection and repair are also easier than the existing auxiliary photomask, and in addition, the manufacturing process margin of the photolithography manufacturing process can be improved.

In order to make the above and other objects, features, and advantages of the present invention more comprehensible, a preferred embodiment is specifically cited below and described in detail with accompanying drawings. In the attached picture:

FIG. 1A is a schematic top view of a conventional photomask with auxiliary patterns;

FIG. 1B is a schematic top view of a conventional photomask with auxiliary patterns;

FIG. 2A is a schematic top view of a photomask that can reduce the proximity effect photolithography process according to a preferred embodiment of the present invention;

2B is a cross-sectional view of the photomask 200 of FIG. 2A along line 2B-2B'; and

3A to 3C are schematic cross-sectional views of a process flow for reducing proximity effect lithography with the photomask shown in FIG. 2A according to a preferred embodiment of the present invention.

Among them, the relationship between each icon number and component name is as follows:

100, 200: Photomask

102, 202, 302: pattern dense area

102a: Edge pattern

102b: central dense pattern

104, 204, 304: single pattern

106: auxiliary pattern

206a, 206b, 306a, 306b: dummy patterns

300: chip

308: Patterned photoresist

309: buffer layer

310: Photoresist

Example

FIG. 2A is a schematic top view of a photomask of a photolithographic fabrication method capable of reducing proximity effects according to a preferred embodiment of the present invention. FIG. 2B is a cross-sectional view of the photomask 200 of FIG. 2A along line 2B-2B'. 3A to 3C are schematic cross-sectional views of a process flow for reducing proximity effect lithography with the photomask shown in FIG. 2A according to a preferred embodiment of the present invention.

Please refer to FIG. 2A and FIG. 2B. First, a photomask 200 is provided. This photomask 200 can be a bright field photomask (clear field mask) or a dark field photomask (dark field mask), and in In this embodiment, a bright field photomask is taken as an example. A device pattern is formed on the photomask 200 , including a pattern-dense area 202 and a single pattern 204 . Dummy patterns (dummy patterns) 206a and 206b are formed around the pattern dense area 202 and the single pattern 204 respectively.

The line width b' of the dummy pattern 206a located around the pattern dense area 202 is not smaller than the pattern line width a' of the pattern dense area 202, preferably the line width b' of the dummy pattern 206a is equal to the pattern line width a' of the pattern dense area 202. Similarly, the line width d' of the dummy pattern 206b around the single pattern 204 is not less than the line width c' of the single pattern 204 , preferably the line width d' of the dummy pattern 206b is equal to the pattern line width c' of the single pattern 204 . In addition, the distance D' between the virtual pattern 206a and the pattern-intensive area 202 is equal to the distance D" between the patterns in the pattern-intensive area 202, that is, the line spacing and pattern density of the virtual pattern 206a are respectively the same as the pattern density in the pattern-intensive area 202. The line spacing and pattern density are the same, except that the pattern density formed by the single pattern 204 and the surrounding dummy patterns 206 b is the same as that of the pattern-dense area 202 .

Next, referring to FIG. 3A , a wafer 300 is provided, and a patterned photoresist 308 is formed on the wafer 300 . The patterned photoresist 308 is, for example, a positive photoresist or a negative photoresist. Taking the bright field photomask provided in FIG. 2A as an example of a photoresist on a patterned wafer 300, the patterned photoresist 308 is a negative photoresist, and on the wafer 300 The method for forming the patterned photoresist 308 includes first forming a photoresist layer (not shown) on the wafer 300, and then performing a soft bake (Soff Bake) manufacturing process. The role of the soft-baking process is to remove the solvent in the photoresist, increase the adhesion of the photoresist, and increase the selectivity of the developer used in subsequent steps to the exposed and unexposed photoresist etc.

Next, an exposure fabrication process is performed with the bright field photomask provided in FIG. etchant (not shown). Then, a post-exposure baking process (Post Exposure Bake) is performed, followed by a development process to form a patterned photoresist 308 with a dense pattern area 302, dummy patterns 306a and 306b, and a single pattern 304 . The dense pattern area 302 , the dummy patterns 306 a and 306 b and the single pattern 304 correspond to the dense pattern area 202 , the dummy patterns 206 a and 206 b and the single pattern 204 on the photomask 200 .

This embodiment takes a bright-field photomask 200 and forming a pattern on a negative photoresist as an example, but in practical applications, a dark-field photomask can be matched with a positive photoresist to carry out the present invention The provided photolithographic fabrication process. In addition, the same as the photomask 200, in the patterned photoresist 308, the line width f of the dummy pattern 306a located around the pattern-intensive area 302 is not smaller than the pattern line width e of the pattern-intensive area 302. The line width f of the pattern 306 a is equal to the pattern line width e of the pattern dense area 302 . Similarly, the line width h of the dummy pattern 306b around the single pattern 304 in the patterned photoresist 308 is not less than the line width g of the single pattern 304, and the preferred dummy pattern 306b line width h is equal to the pattern of the single pattern 304 line width g. In addition, the distance E between the virtual pattern 306a and the pattern-intensive area 302 is equal to the distance E' between the patterns in the pattern-intensive area 302, that is, the line spacing and pattern density of the virtual pattern 306a are respectively the same as the pattern lines in the pattern-intensive area 302. The pitch width and pattern density are the same.

Since the pattern density of the dummy pattern 206a on the photomask is the same as the pattern density of the pattern-dense area 202, and the line widths b' and d' of the dummy patterns 206a and 206b are respectively the same as the pattern line width a' and d' of the pattern-dense area 202 The line width c' of the single pattern 204 is the same, so when the patterned photoresist 308 on the wafer 300 is formed, the edge pattern of the pattern-dense region 202 and the edge of the single pattern 204, because there are dummy patterns 206a and 206b assist, and relatively increase the light intensity and exposure amount of the edge pattern of the pattern dense area 202 and the edge of the single pattern 204, so the pattern (patterned photoresist 308) formed on the photoresist is compared with the photoresist The component pattern on the mask 200 will not be distorted too much, so the proximity effect will not be generated due to weak exposure light intensity and insufficient exposure as in the prior art, resulting in pattern deformation.

Furthermore, since the line widths of the dummy patterns 206a and 206b on the photomask 200 are the same as the pattern of the pattern-dense area 202 and the line width of the single pattern 204, and the distance from the dummy pattern 206a to the edge of the pattern-dense area 202 and the dummy pattern The distance from 206b to the single pattern 204 is not limited by the length of the exposure wavelength as the distance between the auxiliary pattern and the device pattern in the prior art, therefore, the difficulty in manufacturing the photomask is greatly reduced.

In addition, the existing auxiliary pattern must be very small, which causes the difficulty of forming the auxiliary pattern on the photomask, while the line width of the dummy pattern of the present invention is equivalent to the line width of the device pattern, so it can reduce the size of the line width on the photomask. Difficulty in forming dummy patterns, and at the same time reduce the difficulty of testing and correction after photomask manufacturing. Similarly, the virtual pattern of the present invention can also be more easily added to the original layout diagram designed by the customer. In addition, since the dummy patterns 206 a and 206 b can narrow the pattern density difference between the pattern dense area 202 and the single pattern 204 , the manufacturing process margin can be greatly improved.

Next, please refer to FIG. 3B , a layer of photoresist 310 is formed on the patterned photoresist 308 and fills up the pattern-dense region 302 , the dummy patterns 306 a and 306 b and the single pattern 304 . Wherein, the photoresist 310 can be a positive photoresist or a negative photoresist.

Next, referring to FIG. 3C , the soft-baking process of the photoresist 310 is performed. Next, an exposure process and a post-exposure baking process are performed sequentially, followed by a development process to remove part of the photoresist 310 to form a patterned photoresist 308 exposed The photoresist 310 a of the densely patterned area 302 and the single pattern 304 .

Wherein, before forming the photoresist 310 , a buffer layer 309 can be formed on the wafer 300 . The buffer layer 309 is, for example, a hydrophilic anti-reflection coating or a material with a hydrophilic chemical structure. Since the buffer layer 309 is composed of a hydrophilic material, when the second photoresist 310 is developed, the part of the buffer layer 309 not covered by the photoresist 310a can be followed by development. Wash and remove together. Because a buffer layer 309 is formed between the patterned photoresist 308 and the photoresist layer 310, it is possible to avoid the patterned photoresist 308 and the photoresist layer 310 in the process of forming the photoresist 310. The photoresist 310 produces an intermixing process.

Since on the patterned photoresist 308, another layer of photoresist 310 is directly formed, and the patterned photoresist 310 is formed to cover the dummy pattern 306a in the patterned photoresist 308 with 306b, only the required element pattern (that is, the pattern dense area 302 and the single pattern 304) is exposed, so when the element pattern is transferred from the photoresist to the wafer 300 later, the dummy pattern 306a and the dummy pattern 306a will not be simultaneously exposed. 306b are transferred together. The element pattern of the patterned photoresist 308 exposed by the photoresist 310a is also formed by transferring the above-mentioned photomask 200 with dummy patterns 206a and 206b, so the edge of the pattern-dense area 302 and the single pattern 304 There is no proximity effect at the edges.

In summary, the present invention has the following advantages:

1. In the present invention, because the pattern density of the dummy pattern on photomask is identical with element pattern density, and, the line width of dummy pattern is identical with the line width of element pattern respectively, therefore patterned photoresist on formation wafer When the agent is used, the edge of the element pattern is relatively improved due to the assistance of the dummy pattern, and the light intensity and exposure amount of the edge of the element pattern are relatively increased. Patterns are not distorted, and proximity effects are reduced.

2. In the present invention, because the line width of the dummy pattern on the photomask is the same as that of the component pattern, and the distance from the dummy pattern to the edge of the component pattern is not limited as the distance between the existing auxiliary pattern and the component pattern The limitation of the length of the exposure wavelength, therefore, greatly reduces the difficulty of photomask fabrication.

3. The existing auxiliary pattern must be very small to prevent the auxiliary pattern from being transferred to the photoresist during the exposure and development process, but it causes difficulties in forming the auxiliary pattern on the photomask. However, the virtual pattern line of the present invention The width is the same as the element pattern line width, so the difficulty of forming a dummy pattern on the photomask can be reduced, and at the same time, the difficulty of testing and correction after the photomask is manufactured can be reduced.

4. The virtual pattern of the present invention can also be more easily added to the complex original layout diagram designed by the customer. In addition, since the dummy pattern can shorten the pattern density difference between the pattern-dense area and the single pattern in the part pattern, the manufacturing process margin can be greatly improved.

5. In the present invention, by forming two layers of patterned photoresist in sequence, the dummy pattern of the first layer of patterned photoresist is covered with the second layer of patterned photoresist, so it will not be The dummy pattern is transferred from the photoresist to the underlying wafer.

Although the present invention has been disclosed above in conjunction with a preferred embodiment, it is not intended to limit the present invention. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the present invention The scope of protection should be defined by the appended claims.

Claims (23)

1. A photolithographic manufacturing method that can reduce the proximity effect, comprising: providing a wafer on which a first photoresist is formed; A photomask is used to perform a first exposure and development process to pattern the first photoresist, wherein a first element pattern and a first dummy pattern are formed on the photomask, and the first element pattern has a first line pitch width, the first dummy pattern and the first device pattern have a second line pitch width, and the first dummy pattern is located at the periphery of the first device pattern, and the photomask on the transferring the first element pattern and the first dummy pattern to the first photoresist, and forming a second element pattern and a second dummy pattern corresponding to the first photoresist; forming a second photoresist on the patterned first photoresist; and, A second exposure and development process is performed to remove part of the second photoresist and only expose the second element pattern of the first photoresist. 2. The photolithographic fabrication method capable of reducing proximity effects as claimed in claim 1, wherein when the first photoresist is a negative photoresist, the photomask is a bright field photomask . 3. The photolithographic fabrication method capable of reducing proximity effect as claimed in claim 1, wherein when the first photoresist is a positive photoresist, the photomask is a dark field photomask. 4. The photolithographic fabrication method capable of reducing proximity effect as claimed in claim 1, wherein the second photoresist is a negative photoresist. 5. The photolithographic fabrication method capable of reducing proximity effect as claimed in claim 1, wherein the second photoresist is a positive photoresist. 6. The photolithographic manufacturing method capable of reducing the proximity effect as claimed in claim 1, wherein performing the first exposure and developing manufacturing process further comprises: Carrying out a soft baking manufacturing process; performing an exposure process; performing a post-exposure bake fabrication process; and A development process is performed. 7. The photolithography manufacturing method capable of reducing proximity effect as claimed in claim 1, wherein the first line space width is the same as the second line space width. 8 . The photolithography manufacturing method capable of reducing proximity effects as claimed in claim 1 , wherein a density of the first device pattern is the same as a density between the first dummy pattern and the first device pattern. 9 . The photolithography manufacturing method capable of reducing proximity effects as claimed in claim 1 , wherein a line width of the first device pattern is the same as a line width of the first dummy pattern. 10 . The photolithography manufacturing method capable of reducing proximity effect as claimed in claim 1 , further comprising forming a buffer layer above the wafer before forming the second photoresist. 11 . 11. A photolithographic fabrication method capable of reducing proximity effects, comprising: A wafer is provided, and a patterned photoresist is formed on the wafer, wherein the patterned photoresist has a first element pattern and a first dummy pattern, and the first element pattern has a first pitch width, the first dummy pattern and the device pattern have a second line spacing width, and the first dummy pattern is located around the first device pattern; forming a first photoresist on the patterned photoresist; and A first exposure and development process is performed to remove part of the first photoresist, wherein the remaining first photoresist covers the first dummy pattern. 12. The photolithographic manufacturing method capable of reducing proximity effects as claimed in claim 11, wherein the method for forming the patterned photoresist comprises: forming a second photoresist over the wafer; Carrying out a soft baking manufacturing process; A photomask is used to perform an exposure manufacturing process, wherein a second element pattern and a second dummy pattern are formed on the photomask, the second element pattern has a third line width, the second dummy pattern and the second dummy pattern The second device pattern has a fourth line pitch width, and the second dummy pattern is located around the second device pattern; performing a post-exposure bake fabrication process; and performing a development process, the second element pattern and the second dummy pattern are transferred to the second photoresist to form the patterned photoresist, and the patterned photoresist The first element pattern and the first dummy pattern corresponding to each other are formed. 13. The photolithographic fabrication method capable of reducing proximity effects as claimed in claim 12, wherein when the second photoresist is a negative photoresist, the photomask is a bright field photomask . 14. The photolithographic fabrication method capable of reducing proximity effect as claimed in claim 12, wherein when the second photoresist is a positive photoresist, the photomask is a dark field photomask. 15. The photolithography manufacturing method capable of reducing the proximity effect as claimed in claim 12, wherein the third space width is the same as the fourth line space width. 16. The photolithography manufacturing method capable of reducing proximity effect as claimed in claim 12, wherein a density of the second device pattern is the same as a density between the second dummy pattern and the second device pattern. 17. The photolithographic fabrication method capable of reducing proximity effects as claimed in claim 12, wherein a line width of the second device pattern is the same as a line width of the second dummy pattern. 18. The photolithographic fabrication method capable of reducing proximity effect as claimed in claim 11, wherein the first photoresist is a negative photoresist. 19. The photolithographic fabrication method capable of reducing proximity effect as claimed in claim 11, wherein the first photoresist is a positive photoresist. 20. The photolithography manufacturing method capable of reducing proximity effect as claimed in claim 11, wherein the first line space width is the same as the second line space width. 21. The photolithography manufacturing method capable of reducing proximity effects as claimed in claim 11, wherein a density of the first device pattern is the same as a density between the first dummy pattern and the first device pattern. 22. The photolithographic fabrication method capable of reducing proximity effects as claimed in claim 11, wherein a line width of the first device pattern is the same as a line width of the first dummy pattern. 23. The photolithography manufacturing method capable of reducing proximity effect as claimed in claim 11, further comprising forming a buffer layer on the wafer before forming the second photoresist.

Images