CN1261821C - 3D mask - Google Patents

Abstract

The present invention discloses a three-dimensional stereoscopic mask. By increasing the thickness of the opaque layer around the boundary pattern on the mask, the path length of the incident light passing through the boundary pattern is increased, and the optical coherence of the incident light passing through the boundary pattern is improved, thereby reducing the optical proximity effect caused by light interference, reducing the deformation of the exposed boundary pattern or the problem of insufficient focusing depth, so that the three-dimensional stereoscopic mask can expose good graphics.

Description

3D mask

This application is a divisional application of the invention patent application with the application number 01123723.6, the application date being July 26, 2001, and the name "three-dimensional mask".

technical field

The invention relates to a semiconductor device, and in particular to a three-dimensional mask, which can obtain a good boundary pattern and improve the effect of photolithography exposure.

Background technique

In the semiconductor industry, photoresist patterns are made by using photolithography exposure tools such as steppers or scanners to expose on photosensitive materials to define the desired pattern. The steps are first to coat a layer of photoresist layer on the semiconductor substrate, use an exposure tool to project the pattern on the mask onto the photoresist layer, and then use a developer to develop the exposed part of the photoresist layer to make the photoresist layer appear. pattern on the mask. Afterwards, the patterned photoresist layer is used as a mask for subsequent etching or ion implantation processes.

The mask is generally based on a transparent plate, on which opaque lines are formed to define the desired pattern. The transparent plate is generally made of quartz, and the opaque circuit defines the required circuit pattern by etching the chrome (Chrome) layer. The mask is irradiated with the incident light emitted by the radiation source, and an image is formed through pattern shielding of the mask and light diffraction, and a virtual image is projected on the photoresist layer through a projection system. For further explanation on exposure technology, please refer to pages274-276 of VLSI Technology edited by S.M.Sze(1983).

Please refer to FIG. 1 , which is a schematic cross-sectional view of a traditional mask structure. An opaque chromium layer 104 having an opening pattern 106 is formed on the transparent substrate 102 by etching, printing and other techniques, thereby forming the mask 100 . Generally, the opening pattern 106 on the mask 100 is a periodic dense pattern, so when determining the light source conditions, numerical aperture (Numerical Aperture, NA) and optical coherence (coherence) σ are simulated and calculated for an infinite period. However, when it is actually applied to a mask pattern with a limited period, the optical proximity effect (OPE) will occur for the edge pattern, so that the exposed edge pattern is deformed, or the depth of focus (DOF) is insufficient. As shown in FIG. 2 , it represents a pattern 200 exposed on a photoresist layer using a conventional mask 100. It obtains the same pattern as that on the mask 100 in the central portion 202, but deformation occurs in the edge portion 204, making the edge The line width d of the pattern of the portion 204 is enlarged or reduced abnormally. This will easily lead to short circuit or open circuit of the product, thereby reducing the process window of the boundary pattern.

One of the main factors causing the optical proximity effect (OPE) is light interference of adjacent patterns. Traditionally, the method of properly deforming the mask pattern to obtain the correct exposure pattern is called optical proximity correction (OPC). However, the optical proximity correction (OPC) must match the light source conditions. For different light sources, OPC must be modified appropriately to obtain an ideal exposure pattern, which limits the application of OPC masks.

Contents of the invention

In order to overcome the deficiencies of the prior art, the present invention provides a three-dimensional mask, which can improve the phenomenon of boundary pattern deformation and is applicable to various light sources.

The invention provides a three-dimensional mask, which is suitable for a photolithography exposure system. The three-dimensional mask at least includes a base transparent layer and an opaque layer. The opaque layer is located on the base transparent layer, the opaque layer has an opening pattern, and the opening pattern has an edge opening. And a collimating protrusion is arranged on the opaque layer at the periphery of the edge opening. Due to the arrangement of the collimating protrusions, the light interference of adjacent patterns is improved, so that the exposure of the photoresist layer is more accurate.

The invention also provides a three-dimensional mask, which is suitable for a photolithography exposure system. The three-dimensional mask includes a base transparent layer; an opaque layer located on the base transparent layer, the opaque layer has an opening pattern, and the opaque layer in the opening pattern has a curved surface The surface profile, and the thickness of the curved light-proof layer at the edge of the opening pattern is greater than the thickness of the curved light-proof layer at the center of the opening pattern.

The three-dimensional mask of the present invention can solve the problem of deformation of the boundary pattern or insufficient depth of focus caused by the optical proximity effect by changing the exposure condition of the light coherence of the boundary pattern.

The advantages of the present invention are: by increasing the thickness of the opaque layer on the periphery of the border pattern on the mask, the path length of the incident light passing through the border pattern is increased, and the optical coherence of the incident light passing through the border pattern is improved, thereby reducing the optical interference caused by light interference. The resulting optical proximity effect reduces the deformation of the exposed boundary pattern or the problem of insufficient depth of focus, so that the three-dimensional mask can expose good graphics, and can be applied to various light sources.

Description of drawings

Below in conjunction with accompanying drawing and embodiment the present invention is described in detail:

FIG. 1 is a schematic cross-sectional view of a conventional mask structure;

Figure 2 is the pattern exposed on the photoresist layer using a traditional mask, and the problem of deformation or insufficient depth of focus will occur at the boundary of the dense pattern;

3 is a schematic cross-sectional view of a three-dimensional mask structure in a first preferred embodiment of the present invention;

Fig. 4 is the pattern exposed on the photoresist layer using the three-dimensional mask of the present invention, which is the same as the pattern on the mask;

FIG. 5 is a schematic cross-sectional view of a three-dimensional mask structure according to a second preferred embodiment of the present invention.

List of symbols in the figure figure 1 figure 2 image 3 reference sign component or parameter reference sign component or parameter reference sign component or parameter 100 mask 200 exposure pattern 300 mask 102 transparent substrate 202 central part 302 base transparent layer 104 Chrome layer 204 edge part 304 Opaque layer 106 opening pattern d width 306 Alignment protrusion 308 boundary opening h high Figure 4 Figure 5 400 exposure pattern 500 mask 506 surface profile 402 central pattern 502 base transparent layer 508 edge part 404 edge pattern 504 Opaque layer 510 central part 505 opening pattern 512 edge opening

Detailed ways

The invention provides a three-dimensional mask. By forming a three-dimensional mask pattern on the mask, the coherence of the incident light of the edge pattern can be changed, so that the optical proximity effect of the edge pattern can be improved, and the pattern generation of the edge pattern can be reduced. Distortion or lack of focus, and can be applied to a variety of different light sources.

Please refer to FIG. 3 , which is a schematic cross-sectional view of a three-dimensional mask structure according to a first preferred embodiment of the present invention. The three-dimensional mask 300 of the present invention mainly includes a bottom transparent layer 302 whose material is the same as the transparent substrate used in traditional masks, such as highly transparent quartz. On the bottom transparent layer 302 is an opaque layer 304 with a mask opening pattern 305, wherein the opening pattern 305 is a circuit pattern required in a general photolithography exposure process. The material used for the opaque layer 304 is, for example, chromium (Cr), chromium oxide (CrOx), or other opaque materials. Alignment protrusions 306 are provided on the opaque layer 304 around the edge opening 308 of the opening pattern 305 , whereby the alignment protrusions 306 can improve the exposure effect of the edge pattern. The material used for the collimation protrusion 306 is also an opaque material, such as chromium or chromium oxide. Generally, the height h of the collimation protrusion 306 is about 2-15 times the thickness of the opaque layer 304, and the height h can be adjusted according to the optical proximity effect (OPE) of the pattern.

The three-dimensional mask 300 of the present invention is formed by etching, for example. Taking chrome as the material of the opaque layer 304 and chromium oxide as the material of the alignment protrusion 306 as an example. First, a chromium layer and a chromium oxide layer are sequentially formed on the bottom light-transmitting layer 302, and then the alignment protrusion 306 is made by etching with the first pattern, and then the different opening pattern 305 is made by etching with the second pattern. Light-transmitting layer 304 . If different materials are used for the alignment protrusion 306 and the opaque layer 304 , better thickness control can be obtained. If the alignment protrusion 306 is made of the same material as the opaque layer 304 , the opening pattern 305 can be etched in a second pattern after the alignment protrusion 306 is etched through time control.

The three-dimensional mask 300 of the present invention can be directly applied to traditional light sources, and off-axis illumination is preferred, such as annular (annular) light source, quadrapole (quadrapole) light source or dipole (dipole) ) light source, etc., the applied incident light wavelength includes 365nm, 248nm or 193nm, etc. The collimation protrusion 306 of the present invention can change the optical coherence (coherence) of the incident light passing through the edge opening 308, by increasing the path length of the incident light passing through the edge opening 308, the optical coherence of the incident light passing through the edge opening 308 can be increased, In this way, the depth of focus of the edge pattern is improved, and the original pattern is maintained to avoid deformation of the edge pattern. 4 is a pattern 400 exposed on the photoresist layer using the three-dimensional mask 300 of the present invention. The central pattern 402 can maintain the original mask pattern, and the edge pattern 404, that is, the semi-isoline Part (one side of its periphery is a dense pattern, and the other side is a non-pattern area), because the optical coherence becomes better, the light intensity distribution (Aerial image) becomes better, it can maintain the original mask pattern, and obtain a good depth of focus , so the process window during exposure can be expanded and the process conditions can be improved.

Please refer to FIG. 5 , the present invention also provides another three-dimensional mask, which will be described with a second preferred embodiment. The three-dimensional mask 500 of the present invention mainly includes a bottom light-transmitting layer 502 made of, for example, highly transparent quartz. On the bottom transparent layer 502 is an opaque layer 504 having a mask opening pattern 505 , wherein the opening pattern 505 is a pattern in a general photolithography manufacturing process. The material used for the opaque layer 504 is, for example, chromium (Cr), chromium oxide (CrOx), or other opaque materials. The opaque layer 504 at the opening pattern 505 has a curved surface profile 506 , the curved surface profile is concave, low in the middle and high at the edge. Therefore, the thickness of the opaque layer 504 at the edge portion 508 of the opening pattern 505 is greater than the thickness of the opaque layer 504 at the central portion 510 of the opening pattern 505 . Generally, the thickness of the opaque layer 504 at the edge portion 508 is about 2-15 times the thickness of the opaque layer 504 at the central portion 510 . The curved surface profile 506 of the opaque layer 504 needs to be designed according to the opening pattern 505 .

The three-dimensional mask 500 of the present invention can be directly applied to various traditional light sources, such as annular light sources, quadrapole light sources, or dipole light sources. The applied incident light wavelength includes 365nm, 248nm or 193nm and so on. The three-dimensional mask 500 of the present invention calculates the height distribution of the curved surface profile 506 according to the graph of the opening pattern 505, so that the optical coherence of the incident light passing through the opening pattern 505 can be adapted to each opening. In the opening pattern 505, the thickness of the opaque layer 504 around the edge opening 512 is thicker, so the channel at the edge opening 512 is longer, thereby improving its optical coherence, so that the incident light passing through the mask 500 can have Better light intensity distribution.

In summary, the three-dimensional mask provided by the present invention can solve the problem of graphic deformation or insufficient depth of focus of the boundary pattern due to the optical proximity effect by changing the optical coherence of the incident light on the boundary pattern.

As those skilled in the art understand, the above descriptions are only preferred embodiments of the present invention, and are not intended to limit the scope of protection of the present invention; all other equivalent changes that do not deviate from the spirit disclosed in the present invention Or modification, all should be included in the scope of protection of the patent of the present invention.

Claims (6)

1. three-D stereo mask comprises:

One substrate photic zone;

One light non-transmittable layers is positioned on this substrate photic zone, and this light non-transmittable layers has a patterns of openings, and has an edge opening in this patterns of openings; And

One collimation projection is positioned on the light non-transmittable layers of periphery of this rim openings, and thickness of this collimation projection be 2-15 times of this light non-transmittable layers thickness.

2. mask according to claim 1 is characterized in that: the euphotic material of this substrate comprises quartz.

3. mask according to claim 1 is characterized in that: the material of this light non-transmittable layers comprises chromium.

4. mask according to claim 1 is characterized in that: the material of this light non-transmittable layers comprises chromium oxide.

5. mask according to claim 1 is characterized in that: the material of this collimation projection comprises chromium.

6. mask according to claim 1 is characterized in that: the material of this collimation projection comprises chromium oxide.

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