KR20010002127A - A halfton-type phase shift mask and a manufacturing for method the same - Google Patents

Abstract

PURPOSE: A method for manufacturing a halftone phase shift mask is provided to minimize a proximity effect in an exposure process, by making the halftone phase shift mask have multiple transmission factors. CONSTITUTION: A stacked structure of a phase shift layer and a chrome layer is formed on a quartz substrate. The stacked structure is patterned so that one side having a high pattern density and the other side having a low pattern density are formed. A photoresist layer pattern exposing the one side of the pattern of the stacked structure is formed, and a predetermined thickness of the chrome layer on the one side pattern of the stacked structure is etched by using the photoresist layer pattern as a mask. The photoresist layer pattern is removed. A different photoresist layer pattern exposing the other side of the pattern is formed. The chrome layer on the other side pattern of the stacked structure is etched by a thickness different from that of the chrome layer formed on the one side, using the different photoresist layer pattern as a mask. The different photoresist layer pattern is removed to form a chrome layer of a different thickness, the chrome layer being on the stacked structure formed on the one and the other sides.

Description

A halfton-type phase shift mask and a manufacturing for method the same

The present invention relates to a halftone phase shift mask and a method of forming the same. A design rule of 0.20 μm or less is provided by forming a halftone phase shift mask having multiple transmittances for varying the transmittance of each region as necessary. It is a technology that enables high integration of a semiconductor device by being applicable to a semiconductor device having a.

In a semiconductor device manufacturing process, an exposure apparatus forms a pattern of a device on a wafer substrate using a mask. This forms a pattern by exposing light to the photosensitive film of the substrate using the principle of optical pattern transition.

In most exposure apparatuses, the light passing through the mask has an optical limit due to an optical principle, that is, an interference principle of light, and thus, it is difficult to form a pattern according to an optical proximity effect.

This phenomenon is different depending on the patterning capability of the exposure apparatus and the design rule of the device, and the smaller the design rule of the device is, the larger it appears. Therefore, all devices have a resolution limit of the pattern due to optical limitations.

The conventional technology is a basic technology currently used, and after forming a pattern of chromium on a quiz substrate, it is used as a mask disc of an optical exposure apparatus, or a halftone mask or a phase inversion mask is used to improve the lack of process margin. .

In general, in an exposure system that uses light or a laser, a lithography process exposes light to a mask disc so that the chromium patterns block light to distinguish the contrast of the photoresist film on the wafer substrate.

When light passes through the mask, it is based on the interference principle of light, and an image in the air is formed, and the image is transferred to the photosensitive film to form a pattern.

This principle is closely related to the size of the pattern on the mask, the wavelength of the exposure apparatus, and the characteristics of the lens. If a certain wavelength is used, the resolution of the pattern is limited by the interference principle of the above light, and the optical proximity effect by the optical phenomenon has a great influence on the pattern formation in the process.

In recent years, the smaller the size of the device, the greater the effect. These phenomena are natural and cannot be eliminated.

In the case of current chrome masks or phase reversal masks, these phenomena can not be avoided.

In general, the configuration of semiconductor devices (DRAM, SRAM, FeRAM, etc) is as shown in FIG. The area of 1 is called the cell area, and the area of 2 is called the periphery. The capacity of the device is determined by the size of the pattern line widths in 1 and 2, and the smaller the size, the more capacity the device is.

In addition, the pattern is connected to repeating lines in the case of the pattern in the region of 1, and in the case of the region of 2, the circuit is formed by irregular patterns.

In the circuit configuration of the device, repeating patterns such as 3 are formed in the region of 1 as shown in FIG. 2, and irregular patterns such as 4 are drawn in the region of 2.

In recent years, the design rules of devices continue to become smaller, and pattern formation requires less than the limit of exposure equipment. Therefore, the optical interference phenomenon on the mask is very large, and the phenomenon that is reflected in the wafer process is very severe.

For example, if the actual design of the pattern is designed as follows, the general form has the structure of a mask in the form of a line / space (3) and an isolated line (4).

Therefore, when the pattern of this type is exposed, it is difficult to obtain the desired pattern by the optical proximity effect principle mentioned above, and the phenomenon that the line width becomes smaller about 10 nm to 100 nm than the actual design pattern occurs.

In FIG. 2, the darkly colored part is a design pattern, and the part indicated by a dotted line is a result of simulating the pattern shape exposed on the wafer.

The simulation results show that the 0.18 μm design has the same pattern as the dotted line of FIG. 2 in the following pattern, and the optical proximity effect is severe. When describing the phenomenon, patterns of parts such as 5 generally become weak, and patterns in the region become smaller due to the line width, and pattern collapse occurs, and even if they do not fall, the line width of the patterns becomes smaller. Problems arise with the electrical properties. The areas where these phenomena occur severely are very fragile at the end of the pattern, at the end of repeated patterns, and at the exterior of the device design.

This phenomenon is called the optical proximity effect phenomenon, and especially in the case of a pattern independent of the outer shell of the pattern, the light density is severe.

FIG. 3A is a cross-sectional view showing a general chromium exposure mask in which the optical proximity effect is very serious as described above, and shows that the chromium pattern 6 is formed on the quartz substrate 7.

FIG. 3B is a cross-sectional view showing a halftone phase shift mask formed to reduce the disadvantage of the chromium exposure mask, wherein a phase shift film 8 is formed between the quartz substrate 7 and the chrome pattern 6. Shows that.

In the case of the chromium exposure mask that is generally used, the part that transmits light is a quartz substrate, and the part that blocks the light is chrome to block 100% of the light to distinguish the intensity of light. In the case of the halftone phase inversion mask, if the chromium portion is present above or below the phase inversion layer, the resolution of the pattern is increased by allowing the chromium to be transmitted at 4% or more instead of blocking 100% of the chromium transmittance.

In particular, in the case of the half-tone mask, unlike the general mask, light is transmitted to some extent, so that the phase inversion effect occurs at the pattern edge, which is very effective in forming the pattern. Recently, it is widely used in design rules of 0.25 μm or less, and has been applied to the case of line patterns as well as contact holes to obtain many process effects.

However, when the semiconductor device is highly integrated and has a design rule of 0.20 µm or 0.18 µm or less, there is a problem in that the pattern is broken or damaged due to the optical proximity effect, thereby lowering the yield of the device and consequently making the semiconductor device highly integrated.

The present invention has been made in order to solve the above problems of the prior art, to provide a halftone phase inversion mask and a method of forming the same to have multiple transmittances.

1 is a schematic diagram showing the structure and shape of a memory device;

2 is a schematic diagram simulating the actual pattern shape and problems of the memory device.

3 is a cross-sectional view of a general mask and a halftone phase shift mask.

4 is a schematic diagram for explaining an example of a double halftone mask.

FIG. 5 is a graph showing simulation results of line width variation with respect to transmittance of a halftone phase inversion mask. FIG.

6 is a schematic diagram illustrating the principles of the present invention.

7 is a cross-sectional view showing a method for forming a multiple halftone phase inversion mask according to the present invention;

In order to achieve the above object, the halftone phase inversion mask according to the present invention,

A halftone phase inversion mask that varies the transmittance between one side having a high pattern density and the other side having a low pattern density,

The one side and the other side is formed of a laminated structure of a chrome film pattern and a phase inversion film pattern patterned on the quartz substrate,

The chromium film pattern is provided with different thicknesses on the one side and the other side, and the laminated structure of the one side and the other side has different transmittances during the exposure process.

In order to achieve the above object, the halftone phase inversion mask forming method according to the present invention,

Forming a laminated structure of a phase inversion film and a chromium film on the quartz substrate;

Patterning the laminated structure to form one side having a high pattern density and the other side having a low pattern density;

Forming a photosensitive film pattern exposing one side of the laminated structure pattern and etching the chromium film on the one side of the laminated structure pattern by a predetermined thickness using the mask as a mask;

Removing the photoresist pattern;

Forming another photosensitive film pattern exposing the other side of the laminated structure pattern;

Etching the chromium film on the other side of the laminated structure pattern with a thickness different from that of the chromium film formed on the one side using the other photoresist pattern as a mask;

And removing the other photoresist pattern to form different thicknesses of the chromium film on the upper side of the laminated structure formed on one side and the other side, thereby forming different transmittances on one side and the other side.

On the other hand, the principle of the present invention for achieving the above object,

Since the intensity of light transmitted varies depending on the pattern shape and density, even if the pattern has the same line width, a halftone phase reversal mask having multiple transmittances is used to solve the problem that the change in the line width formed on the wafer is different. By automatically compensating for the magnitude of the change in line width, the desired pattern size can be obtained.

Referring to the principle of the present invention in more detail as follows.

The present invention has the possibility of miniaturization of the device since it is possible to fundamentally improve the optical proximity effect discussed in the previous section by using the halftone phase inversion mask and to accurately calculate the correction factor in the design. The technical principle of the present invention is a method of manufacturing a halftone mask having a good resolution by adjusting the transmittance of the halftone mask in two or more multiples to improve the optical proximity effect, rather than using one transmittance. For example, as shown in the example of FIG. 4, the light transmittance of the halftones is produced in one mask according to the characteristics of the pattern.

In general, the amount of change in the line width of the cell and the line width of the peripheral circuit is different when forming the device pattern (optical proximity effect). Therefore, in recent years, since these phenomena occur in the manufacture of ultrafine devices, optical proximity correction (OPC) tools are being developed.

The OPC tool is a method for calibrating a device in designing a device, and the present invention is a method for adjusting a change in line width resulting from the optical proximity effect in hardware on a mask without changing a conventional design. Assuming that a halftone mask having a transmittance of 5% and 10% is fabricated as shown in the figure by designing a 0.20㎛ line as shown in FIG. 4, the change in line width is due to the optical proximity effect when a conventional mask is used. Although the difference in the line width of 20 nm or more is shown, the mask of the present invention can be adjusted to 10 nm or less as shown in the simulation results.

Basically, repeating patterns are designed in the cell area and independent patterns are designed in the surrounding area. When the device using such a pattern is subjected to a pattern forming process, the pattern of the peripheral circuit region shows a much larger change in line width than the pattern of the cell region.

Therefore, when the mask is manufactured as shown in FIG. 4, since the independent pattern of the peripheral circuit region is formed larger as shown in the simulation result of FIG. 5, a result of naturally correcting a line width of 10 nm or more is obtained.

This principle is illustrated in the figure of FIG. As shown in Fig. 9, the pattern of the cell region is a half width pattern and the pattern of 10 is an independent pattern. 11 denotes the part where the transmittance of the peripheral circuit is different.

In the case of using such a mask, the intensity of light passing through the mask is the same as the graph of 12 when the mask is not used, and the size of the line width is large because the light characteristics of 13 are used. Using this principle, the mask can be extended to various parts of the mask, resulting in a hardware compensation for optical proximity. In addition, this method can be a basic technology of device shrinkage because the outer design rules of the device can be made smaller.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

7 (a) to 7 (h) are cross-sectional views illustrating a method of forming a multiple halftone phase shift mask according to the present invention.

First, a phase inversion film 16 is formed on the quartz substrate 17 and a chromium film 15 as a light shielding pattern is formed on the quartz substrate 17.

A first photosensitive film 14 for electron beams is formed on the chromium film 15. (FIG. 7A)

Then, the first photosensitive film 14 is exposed and developed by using the designed exposure equipment to form the first photosensitive film 14 pattern. (FIG. 7B)

In addition, the chromium film 15 and the phase inversion film 16 are etched and patterned using the first photoresist layer 14 as a mask to form a chromium film 15 pattern and a phase inversion film 16 pattern. (FIG. 7C)

Then, the first photosensitive film 14 pattern is removed to form the second photosensitive film 21 for electron beams on the entire surface. (FIG. 7D)

Next, the second photoresist layer 21 is etched to form a second photoresist layer 21 pattern exposing 200 portions of the quartz substrate 17 and coating 100 portions.

Then, the second photoresist layer 21 pattern is used as a mask to etch a portion of the upper portion of the chromium layer 15 pattern on the phase inversion layer 16 pattern to adjust the transmittance. (FIG. 7E)

Next, the second photoresist film 21 pattern is removed, and a third photoresist film 23 for electron beam is formed on the entire surface. (FIG. 7F)

The third photoresist layer 23 is exposed and developed to form a third photoresist layer 23 pattern exposing the 100 portions and applying 200 portions. In this case, the third photoresist layer 23 pattern is formed in a shape opposite to that of the second photoresist layer 21 pattern.

Subsequently, a portion of the upper portion of the chromium film 15 pattern formed in the 100 region is etched using the third photosensitive film 23 pattern as a mask to form a transmittance different from that of the chromium film pattern formed in the 200 region. (Fig. 7g)

Then, the third photoresist layer 23 pattern is removed to form a double halftone phase shift mask provided with different transmittances due to different thicknesses of the chromium layer 15 patterns formed in the 100 and 200 regions. (FIG. 7H)

Herein, the present invention may repeat the process of FIGS. 7D to 7G to form a halftone phase inversion mask having a chromium film pattern which is a multi-permeable membrane having a multi-transmittance instead of a double.

On the other hand, the method of controlling the transmittance of the quartz substrate, as described above to form a laminated structure of the phase inversion film and the chromium film, and instead of etching by adjusting the upper portion of the chromium film to form the laminated structure on the back of the mask. It may be.

In addition, the quartz substrate may be etched instead of the laminated structure of the phase inversion film and the etched chromium film, but the transmittance may be controlled by adjusting the etching thickness. At this time, the etching method is performed by a wet or dry method.

In addition, the anti-reflection film may be patterned instead of the laminated structure of the phase inversion film and the chromium film. Herein, the anti-reflection film may be formed of a multi-layer polymer or an inorganic film.

The transmittance may be changed during the exposure process by plasma treatment, chemical attack, or ion implantation of the surface of the quartz substrate having different transmittances.

The conventional method uses a method of transferring a design pattern to a mask as it is, and the optical proximity effect of the mask is reflected in the wafer process as it is. Therefore, it has a great influence on the formation of the extremely fine pattern, making it difficult to manufacture the extremely fine device, and also requires many design revisions.

The mask pattern manufactured according to the principle of the present invention is manufactured by compensating the optical proximity effect by the transmittance, thereby facilitating the process and controlling the line width during the process, thereby providing many advantages, and basically reducing the number of mask revisions, thereby reducing the cost and It affects yield a lot. In addition, since the scope of application of this technology is more effective for ultra-fine devices, the effect can be maximized when used in the manufacture of devices with 0.20 ㎛ or less.

Finally, the mask manufacturing effect of the present invention has the advantage that can reduce the sulge rule. The general design cannot be miniaturized because the size of the cell and the size of the peripheral furnace cannot be reduced. Its root cause is that the optical proximity effect is so large that the formation of linewidth is impossible. Therefore, the use of the mask of the present invention can eliminate the optical proximity effect, so it is considered that a smaller design is possible.

Claims (16)

A halftone phase inversion mask that varies the transmittance between one side having a high pattern density and the other side having a low pattern density, The one side and the other side is formed of a laminated structure of a chrome film pattern and a phase inversion film pattern patterned on the quartz substrate, The chrome film pattern is provided with different thicknesses on the one side and the other side, each halftone phase shift mask having a transmittance different from the laminated structure of the one side and the other side during the exposure process. The method of claim 1, A halftone phase inversion mask, characterized in that the laminated structure is provided below the quartz substrate. The method of claim 1, The halftone phase inversion mask is characterized in that the one side of the high pattern density is provided with a low transmittance because the thickness of the chromium pattern is thicker than the other side having a low pattern density. The method of claim 1, A halftone phase shift mask comprising a plurality of stacked structures having different transmittances in at least two regions of one side and the other side according to pattern density. The method of claim 1, The laminated structure is a halftone phase inversion mask, characterized in that provided with an antireflection film such as a multi-layer polymer or an inorganic material thin film. The method according to claim 1, wherein A halftone phase shift mask according to claim 1, wherein the laminated structure region is plasma-processed instead of the patterned laminated structure. The method according to claim 1, wherein A halftone phase shift mask according to claim 1, wherein the layered region is chemically treated instead of the patterned layered structure. The method according to claim 1, wherein A halftone phase shift mask according to claim 1, wherein the stacked region is ion implanted instead of the patterned stacked structure. Forming a laminated structure of a phase inversion film and a chromium film on the quartz substrate; Patterning the laminated structure to form one side having a high pattern density and the other side having a low pattern density; Forming a photosensitive film pattern exposing one side of the laminated structure pattern and etching the chromium film on the one side of the laminated structure pattern by a predetermined thickness using the mask as a mask; Removing the photoresist pattern; Forming another photosensitive film pattern exposing the other side of the laminated structure pattern; Etching the chromium film on the other side of the laminated structure pattern with a thickness different from that of the chromium film formed on the one side using the other photoresist pattern as a mask; And removing the other photosensitive film pattern to form different chromium film thicknesses on the upper side of the laminated structure formed on one side and the other side, thereby forming different transmittances on one side and the other side. The method of claim 9, And forming the lamination structure under the quartz substrate. The method of claim 9, A method of forming a halftone phase shift mask according to claim 1, wherein the chromium film on one side having a high pattern density is etched less than the chromium film on the other side having a low pattern density. The method of claim 9, The method of forming a halftone phase shift mask according to claim 1, wherein the etching process of the chromium film on one side and the other side is divided into two or more regions according to the pattern density to form a plurality of stacked structures having different transmittances in two or more regions. The method according to claim 9, The laminated structure is a halftone phase inversion mask forming method, characterized in that formed by an antireflection film such as a multi-layer polymer or an inorganic material thin film. The method according to claim 9, And a plasma treatment of the laminated structure region in place of the patterned laminated structure forming process. The method according to claim 9, And a chemical attack on the laminated structure region instead of the patterned laminated structure forming process. The method according to claim 9, And ion implantation of the layered region instead of the patterned layered structure.