TW591693B - Novel exposure method to form minute contact hole of next generation - Google Patents

Abstract

The exposure method of the present invention to form contact hole array is to use the photomask with densest periodic pitch pattern with twice-exposure technology, so as to form the mutually orthogonal grid point array region. Each orthogonal grid point is a contact hole. The desired regions formed by the cooperation of photomask have more irradiation dosage or less irradiation dosage (depends on the positive/negative photoresist), so that it can be developed to produce the required pattern of contact hole array. Finally, other photomask is used to define the specific region and expose again based on the practical requirement of layout, so as to generate the required contact hole pattern.

Description

V. Description of the invention ------------ Field of the invention: The method of making a visit is used to make the semiconductor lithography process, especially a new exposure for a contact window array. BACKGROUND OF THE INVENTION The integrated circuit (I c) is constantly evolving and improving in technology, and increasing the density of electronic components has suddenly become a trend. By reducing the size of the electronic component ', the integration density of the semiconductor integrated circuit can be increased. As the size of electronic components has been reduced, integrated circuits continue to present many new challenges in the manufacturing process. For example, the reduction in the size of the dynamic random memory (DRAM) unit size 'causes a reduction in storage capacity and results in reliability == increasing wafer density on semiconductor wafers', so the role of the lithography process also plays a role Benefit shape I. In the integrated circuit, the lithography is an important process of multi-layer structure, and it also provides 7 bits. Lithography and engraving include the formation as a veil. Second, the semiconductor layer with a very fine pattern is accurately formed between heavy layers. Because the pattern is in order to build a lithography process with sub-micron resolution capabilities, 4 needs a kind of The result of the process. "Resistance coating will also greatly increase the number of conductive layers and isolation layers by lithography branches in the circuit manufacturing process. The multiple 5 can be formed on the semiconductor substrate, which often determines the shape of the metal interconnects. In the circuit that accurately matches each other, lithography and #engraving are the advantages and disadvantages of making multiple layers of society. The integration also provides accurate alignment between multiple layers. The important process of the ij structure, and the remaining time includes Formation

591693 V. Description of the invention (2) "-* one-by-one photoresist patterns in order to form the required structures such as contact windows, metal interconnects and 7L pieces of + conductors. & The photoresist pattern forms a pattern 幵 y on the film layer and aligns it with the bottom layer. In order to build semiconductor elements with very fine patterns, a lithography process with sub-micron resolution capability is needed. In any optical projection system, including semiconductor lithography, the main key to limiting resolution is the numerical aperture (NA) of the lenses used in this optical system. For a particular wavelength, a larger NA provides better resolution. However, in order to obtain this advantage, it also pays a great price, that is, when the NA increases, the depth of the focal length will be significantly reduced. ,

The optical lithography system plays a very important role. Phase shift masks play an important role in the application of deep ultraviolet technology. Generally, after a quartz substrate is prepared, a phase shifting layer is deposited on the above-mentioned quartz substrate, and a chromium layer is successively formed thereon. A photoresist is applied to the chromium layer using conventional techniques to help define the pattern of the chromium layer. The specific area of the photoresist is scanned with an electron beam to define an area to be exposed, so as to facilitate the generation of a pattern. Thereafter, the above-mentioned photoresist is developed and heat-treated to produce a pattern. The above-mentioned photoresist pattern is used as an etching mask to etch the chrome layer by wet etching, and then the phase shifter is etched by dry etching. One of the previous technologies can be found in Michael E. Kling, et a 1. " Practicing extension of 248nm DUV optical lithography using trim-mask PSM1 'SPIE Microlithography 1999, pp. 10-17. Masanobu Hasegana, et a 1. " Practical appli ations of IDEAL

591693 V. Description of the invention (3) exposure method, SPIE Vol. 3873, pp6 6-77. Generally, the process window of a conventional contact hole array lithography process is very small, which is enough to influence the yield of a wafer process. The main disadvantage of the traditional contact hole array lithography process is that it is difficult to obtain a good process tolerance when it is used in a deep ultraviolet wavelength stepper of 193 nm and 24.8 nm. The process window of the previous exposure technology is shown in Figure 1A, which is based on off-axis illumination. Objective and summary of the invention: The purpose of the present invention is to provide a lithography. Seven ★ Liao ~ table to form a contact window array. Another object of the present invention is to provide an exposure. Vertical and horizontal map macro eight array. '' Ten pattern masks used to get on the contact window

A method for generating a photoresist pattern includes eight steps: you can apply a photoresist pattern to a wafer, and use a periodic circle in the first direction of package 3 and a mask with a thorn pattern to perform exposure. A gB ^ -V ^ mask is used to perform the exposure to produce a predetermined area for exposure, ... The third mask definition used is specific to positive or negative photoresistance and blocks the pattern first. This invention is applicable

Page 6 591693 V. Description of the invention (4) Detailed description of the invention: The method disclosed in the present invention is a method of exposure of a contact window array. At least two exposures are used in combination with a densely spaced periodic line gap pattern to form a mask with mutual In the orthogonal grid point array area, each orthogonal grid point is a contact window. The combination of the photomask is used to form a desired area with a higher or lower irradiation dose (depending on the positive and negative photoresistance) to facilitate the development of the desired contact window array pattern. Finally, according to the actual layout requirements, another mask is used to define a specific area, and then exposed again, and the required contact window pattern is defined. Its detailed description will be as follows. Therefore, forming a regularly arranged contact window array requires two exposure steps, and forming an irregularly arranged contact window array or a specific area requires three exposure steps. The order of the above exposure steps can be reversed arbitrarily, and they should all be included in the spirit of the present invention. Referring to FIG. 2A, a positive photoresist is used as an illustration. The first mask 100 can be used to cover the area where the contact window is not formed for the first exposure. The exposure intensity is controlled so that the light-blocking part of the generated area receives light. A second exposure is performed using a mask having a plurality of periodic horizontal stripe patterns. After that, a third exposure is performed using a mask having a plurality of periodic vertical stripe patterns. Then, a grid-shaped exposure pattern in FIG. 1 can be formed. The above exposures result in patterns whose directions are orthogonal to each other. The exposure dose can be controlled to form a horizontal stripe interval or a vertical stripe interval with different photosensitive doses.

Page 7 591693 V. Description of the invention (5) ^ ------- And the photosensitive state of the same level = interlaced interval is the 20% effect of the above-mentioned horizontal blood vertical state. As known in the prior art, coating with a positive photoresist, the positive photoresist that is irradiated can be removed with a developer, or the degree or thickness of the positive photoresist that is removed is also different depending on the irradiation dose. The required area is formed in two: the array pattern is in the photoresist 'as shown in the figure. Therefore, by using the method of the present invention, it is possible to make a contact window pattern with a very small pitch, so as to surpass the limitation of the prior art due to the optical effect. For example, this method can produce a contact window array of 0.2 micrometers and a pitch of 240 micrometers. The above-mentioned exposure technology can be adopted, but not limited to, phase shift mask (PSM) > attenuated PSM ^ halftone PSM ^ alternating PSM, chromeless PSM. Exposure procedures for positive photoresistance can refer to Figure 3A, in A positive photoresist 410 is coated on the wafer 400, and a first mask 420 is used to define a region where a contact window is to be formed. The exposure-controlling dose is used to generate a positive photoresistance region 430 having a first dose, as shown in FIG. 3B. Next, referring to FIG. 3c, the second and third exposures are performed using the mask 44o formed by the vertical and horizontal patterns described above. Similarly, the exposure dose is controlled to form regions with different exposure doses. Thereafter, a photoresist pattern having a contact window 440 is formed through development, as shown in FIG. 3D. In the same way, the present invention can also be applied to the case of negative photoresist. As known in the prior art, the negative photoresist coated with negative photoresist can be removed with a developer, or depending on the irradiation dose. There is also a state of photoresist removal

IH Page 8 591693 V. Description of the Invention (6) Differences. The mask pattern used is a negative image with positive photoresist. Refer to Figure: A and Figure 4B, with-negative photoresistance as an explanation, respectively = yes; number of masks with parallel horizontal stripe pattern, and masks with multiple parallel vertical stripe pattern for exposure. It can form exposed or unexposed areas with a grid pattern (depending on user needs). The mask pattern used is a negative image with positive photoresist. It is possible to control the doses of two exposures to form horizontal bar intervals or vertical bar intervals with different photosensitivity. The photosensitive state of the horizontal and vertical parental error interval is the combined effect of the above horizontal and vertical states. The above steps can be reversed. Before development, a third mask 200 can be used to cover the area where the contact window is to be formed for the third exposure. Unlit areas will be removed. After that, development \ Therefore, after development, an array pattern of contact windows will be formed in the required area in the negative photoresist. ^ 程序 Exposure procedure of negative photoresistor 'can refer to Figure 5A to Figure 5]), apply negative photoresistor 510 on the wafer 500, and perform the first and second exposures in the above manner. The pattern 5 2 0 defines the area where the contact window is to be formed. A controlled exposure dose is used to create a photoresist region with a first dose. Continuing, referring to FIG. 5C, a mask 530 is used to cover a part of the area for the third exposure. After that, the contact window pattern is formed in the area covered by the photomask 53 after development, as shown in FIG. 5D. ~ Figure 6 is the result of the present invention. The two photomasks have horizontal or vertical stripe patterns, respectively. After exposure and development, a pattern of contact window arrays is formed. Figure

Page 9 591693 V. Description of the invention (7) 7 and Figure 8 are the allowable ranges of the process measured by the present invention, which are processed using alternate PSM and crless PSM respectively. Better than the prior art shown in Figure 1. * Any contact window array pattern can be defined by two exposures using the vertical and horizontal periodic stripe pattern masks of the present invention. Phase shift mask (PSM), attenuated PSM, halftone PSM, alternating PSM, chromeless PSM can be used, but not limited to. Optionally, another photomask can be added for exposure to determine the area where the contact window is to be generated. The effects of the present invention include improved resolution φ degree, image contrast, depth of focus, exposure dose latitude in the process tolerance range, and zero 0PC of microlithography. Using alternating 'PSM technology can increase exposure dose latitude by 10% and depth of focus of 0.6 micron. Therefore, the present invention is very suitable for the deep ultraviolet lithography process, and the chrome less PSM technology has the potential to push the resolution of the deep ultraviolet lithography process to 100 nm. The invention is described above with reference to the preferred embodiment, and those skilled in the art can make some modifications to it without departing from the spirit of the invention. For example, the invention can use a positive or negative photoresistor, and The order of exposure can be adjusted according to the needs, and the scope of patent protection depends on the scope of the patent application and its equivalent fields.

Page 10 591693 Brief Description of Drawings Schematic description: The preferred embodiment of the present invention will be described in more detail with the following figures in the following description: Figure 1 is a diagram of the process tolerance range of the prior art. FIG. 2A is a schematic view of performing three exposures using a positive photoresist, a periodic pattern mask, and a special mask to make a contact window according to the present invention. Fig. 2B is a schematic view of a contact window pattern made by the method of Fig. 2A according to the present invention. FIG. 3A is a schematic diagram of a step of applying a positive photoresist according to the present invention. FIG. 3B is a schematic diagram illustrating the steps of defining a desired window area with a special photomask in the present invention. FIG. 3C is a schematic diagram of the steps of performing two exposures with a periodic pattern mask in the present invention. FIG. 3D is a schematic diagram of a positive photoresist pattern after development according to the present invention. FIG. 4A is a schematic view of performing three exposures using a negative photoresist, a periodic pattern mask, and a special mask to make a contact window according to the present invention. Fig. 4B is a schematic view of a contact window pattern made by the method of Fig. 4A according to the present invention. FIG. 5A is a schematic diagram of a step of applying negative photoresist according to the present invention. Fig. 5B is a schematic diagram showing the steps of defining a desired window area by a special mask in the present invention. FIG. 5C is a schematic diagram of the steps of performing two exposures with a periodic pattern mask according to the present invention. FIG. 5D is a schematic diagram of a negative photoresist pattern after development according to the present invention.

Page 11 591693 Brief Description of Drawings Figure 6 is a schematic diagram of the results of simulation using the technology of the present invention. Figures 7 and 8 are diagrams of the process tolerance range of the present invention

Claims (1)

591693 VI. Application Patent Scope 1. A method for generating a photoresist pattern, the method comprising: coating a photoresist pattern on a wafer, performing exposure using a mask including a periodic pattern in a first direction; and using a mask including a second pattern A mask with a directional periodic pattern performs exposure to generate areas with varying degrees of exposure. 2. The method of generating a photoresist pattern as described in the first patent application, wherein the first direction and the second direction are orthogonal. 3. The method of generating a photoresist pattern as described in the first patent application, wherein the first direction is a horizontal direction. 4. The method for generating a photoresist pattern as described in the first patent application, wherein the second direction is a vertical direction. 5. The method for generating a photoresist pattern according to item 1 of the patent application scope, wherein the periodic pattern in the first direction includes a horizontal stripe pattern. 6. The method for generating a photoresist pattern according to item 1 of the scope of patent application, wherein the periodic pattern in the second direction includes a vertical stripe pattern. 7. The method for generating a photoresist pattern according to item 1 of the patent application range, wherein the second direction is a horizontal direction. Page 13 591693 6. Scope of patent application 8. The method for generating a photoresist pattern as described in the first patent application scope, wherein the first direction is a vertical direction. 9. The method for generating a photoresist pattern according to item 1 of the scope of patent application, wherein the above-mentioned periodic pattern in the second direction includes a horizontal stripe pattern. 10. The method of generating a photoresist pattern according to item 1 of the scope of the patent application, wherein the periodic pattern in the first direction includes a vertical stripe pattern. 11. The method of generating a photoresist pattern according to item 1 of the patent application scope, which further includes defining a specific area for a third exposure using a third mask to define a desired photoresist pattern. 12. —A method for generating a pattern in a positive photoresist, including:-exposing using a mask having a periodic first-direction pattern; exposing using a mask having a periodic second-direction pattern to form the first The directional section or the second directional section has different photosensitivity. Development is performed to remove a part of the photosensitive positive photoresist to form the pattern in the positive photoresist. 13. For example, the method of generating a pattern in a positive photoresistance according to item 12 of the patent application scope, which further includes defining a specific area for exposure using a third mask to define a desired photoresist pattern. Page 14 591693 6. Scope of Patent Application 14. For the method of generating a pattern in a positive photoresistor according to item 12 of the patent application scope, the first direction and the second direction are orthogonal. 15. For the method for generating a pattern in a positive photoresistance according to item 12 of the patent application, wherein the first direction is a horizontal direction. 16. For the method for generating a pattern in a positive photoresistor according to item 12 of the patent application, wherein the second direction is a vertical direction. 17. The method for generating a pattern in a positive photoresistor according to item 12 of the patent application, wherein the above-mentioned periodic pattern in the first direction includes a horizontal stripe pattern. 1 8. The method for generating a pattern in a positive photoresistor according to item 12 of the scope of patent application, wherein the above-mentioned periodic pattern in the second direction includes a vertical stripe pattern. 19. For the method of generating a pattern in a positive photoresistor according to item 12 of the patent application, wherein the second direction is a horizontal direction. 20. For the method for generating a pattern in a positive photoresistor according to item 12 of the patent application scope, wherein the first direction is a vertical direction. 21. The method for generating a pattern in a positive photoresistor according to item 12 of the patent application, wherein the above-mentioned periodic pattern in the second direction includes a horizontal stripe pattern. Page 15 591693 VI. Scope of Patent Application 2 2. The method of generating a photoresist pattern according to item 12 of the patent application scope, wherein the above-mentioned periodic pattern in the first direction includes a vertical stripe pattern. 23. A method for generating a pattern in a negative photoresist, comprising: exposing using a mask having a periodic first-direction pattern; and exposing using a mask having a periodic second-direction pattern to form the first direction The interval or the second direction interval has different photosensitive doses; Φ develops and removes a part of the above-mentioned negative photoresist that is not photosensitive to form the pattern in the negative photoresist. 2 4. If the method of generating a pattern in a negative photoresistance according to item 23 of the scope of the patent application, it further includes using a third mask to define a specific area for exposure to define a desired photoresist pattern. 25. The method for generating a pattern in a negative photoresistor according to item 23 of the scope of patent application, wherein the first direction and the second direction are orthogonal. 2 6. The method for generating a pattern in a negative photoresistor according to item 23 of the scope of patent application, wherein the above-mentioned first direction is a horizontal direction. 27. The method for generating a pattern in a negative photoresistance according to item 23 of the patent application, wherein the second direction is a vertical direction. 2 8. The method of generating a pattern in negative photoresistance as described in item 23 of the scope of patent application Page 16 591693 6. Method of applying for a patent, wherein the above-mentioned periodic pattern in the first direction includes a horizontal stripe pattern. 29. The method for generating a pattern in a negative photoresistance according to item 23 of the patent application, wherein the above-mentioned periodic pattern in the second direction includes a vertical stripe pattern. 30. For the method for generating a pattern in a negative photoresistance according to item 23 of the patent application, wherein the second direction is a horizontal direction. 31. For the method of generating a pattern in a negative photoresistance according to item 23 of the patent application, wherein the first direction is a vertical direction. 3 2. The method for generating a pattern in a negative photoresistance according to item 23 of the scope of patent application, wherein the above-mentioned periodic pattern in the second direction includes a horizontal stripe pattern. 3 3. The method for generating a negative resistance pattern according to item 23 of the scope of patent application, wherein the periodic pattern in the first direction includes a vertical stripe pattern.