JPH05150439A - Manufacture of phase shift photomask - Google Patents

Abstract

PURPOSE:To manufacture a phase shift photomask which prevents deterioration of a light shield film at the time of a dry etching of a phase shift pattern and has a phase shift pattern of a vertical side face. CONSTITUTION:A process to form a phase shifter 16 is constituter of a process in which an ionizing radiation resist pattern 17 is formed on a part corresponding to the phase shifter pattern using an ionizing radiation resist of the color which shields or attenuates exposure light on a substrate surface on which a light shielding pattern 15 and an uniform thickness of transparent film 16 are formed, a processs in which a photoresist 18 is applied on the whole substrate surface on which the ionizing rediation resist pattern 17 is formed and the whole surface is subjected to exposure 19 from the rear of the substrate to form the photoresist pattern 18 on a part coorresponding to the light shield pattern and the phase shifter pattern and a process in which the uniform thickness of transparent film 19 is sujected to a dry etching 20 using the photoresist pattern 18 as mask and the phase shifter pattern is formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photomask manufacturing method used for manufacturing high density integrated circuits such as LSI and VLSI, and particularly to a phase shift layer for forming a fine pattern with high accuracy. And a method for manufacturing a photomask having the above.

[0002]

2. Description of the Related Art Semiconductor integrated circuits such as ICs, LSIs, and VLSIs are formed by applying a resist onto a substrate to be processed such as a Si wafer, exposing a desired pattern with a stepper, and then developing and etching it. It is manufactured by repeating the lithography process.

Photomasks called reticles used in such lithography processes tend to be required to have higher precision as semiconductor integrated circuits have higher performance and higher integration. The line width of the device pattern formed using these photomasks is 1 Mbit D
1.2 μm for RAM and 0.8 μ for 4-bit DRAM
The m and 16 Mbit DRAMs are required to be further miniaturized to 0.6 μm, and various exposure methods are being researched in order to meet such demands.

However, in the case of a 64-Mbit DRAM class device, for example, a pattern having a line width of 0.35 μm is required, and the stepper exposure method using a reticle used so far becomes the resolution limit of a resist pattern. As a means for overcoming, for example, Japanese Patent Laid-Open No. 58-
A reticle of a new concept called a phase shift photomask has been proposed as disclosed in Japanese Patent Publication No. 173744, Japanese Patent Publication No. 62-59296, and the like. Phase shift lithography using a phase shift reticle is a technique for improving the resolution and contrast of a projected image by manipulating the phase of light passing through the reticle.

Phase shift lithography will be briefly described with reference to the drawings. FIG. 3 is a diagram showing the principle of the phase shift method,
FIG. 4 is a diagram showing a conventional method, which is shown in FIGS.
FIG. 3A is a cross-sectional view of the reticle, FIGS. 3B and 4B.
Is the amplitude of the light on the reticle, FIGS. 3 (c) and 4 (c) are the amplitudes of the light on the wafer, FIGS. 3 (d) and 4 (d) are the light intensities on the wafer, respectively, 1 is Substrate 2, light-shielding film 3, reference numeral 3 indicates a phase shifter, and reference numeral 4 indicates incident light.

In the conventional method, as shown in FIG. 4A, a light-shielding film 2 made of chromium or the like is formed on a substrate 1 made of glass or the like to form a light transmitting portion having a predetermined pattern. However, in phase shift lithography,
As shown in FIG. 3A, a phase shifter 3 made of a transmissive film for inverting the phase (phase difference 180 °) is provided on one of the adjacent light transmissive portions on the reticle. Therefore, in the conventional method, the amplitude of the light on the reticle becomes in-phase as shown in FIG. 4B, and the amplitude of the light on the wafer becomes in-phase as shown in FIG. 4C. As a result, As shown in FIG. 4D, the pattern on the wafer cannot be separated, whereas in phase shift lithography, the light transmitted through the phase shifter is
As shown in (b), since the adjacent patterns are in opposite phases to each other, the light intensity becomes zero at the boundary portion of the patterns, and the adjacent patterns are clearly separated as shown in FIG. 3 (d). be able to. As described above, in the phase shift lithography, it becomes possible to separate a pattern that could not be separated in the past, and the resolution can be improved.

Next, one example of the conventional manufacturing process of the phase shift reticle will be described with reference to FIG. 6. FIG. 6 is a sectional view showing the manufacturing process of the phase shift reticle, as shown in FIG. Then, a chrome reticle completed by providing the chrome pattern 6 on the substrate 5 is prepared, and then a transparent film 7 made of SiO ₂ or the like is formed on the chrome pattern 6 as shown in FIG. Form. Next, as shown in FIG. 3C, an ionizing radiation resist layer 8 such as chloromethylated polystyrene is formed on the transparent film 7, and as shown in FIG. Align,
A predetermined pattern is drawn by ionizing radiation 9 such as an electron beam exposure device, developed and rinsed to form a resist pattern 10 as shown in FIG.

Next, after performing a heat treatment and a descum treatment as needed, as shown in FIG. 1F, the transparent film 7 portion exposed from the opening of the resist pattern 10 is dried by an etching gas plasma 11. Etching is performed to form the phase shifter pattern 12. The phase shifter pattern 12 is formed by etching gas plasma 1
Instead of dry etching according to No. 1, wet etching may be performed.

Next, the remaining resist is ashed and removed by oxygen plasma 13 as shown in FIG. Through the above steps, the phase shift photomask having the phase shifter 12 as shown in FIG.

[0010]

By the way, in the phase shift reticle manufacturing process as shown in FIG. 6, dry etching is usually used for pattern processing of the phase shifter in order to perform highly accurate dimension control. .. Particularly, in the phase shift reticle having the structure in which the chrome pattern 6 is provided on the phase shifter pattern 12 as shown in FIG. 5, an undercut is formed under the edge of the chrome pattern 6 during the phase shifter etching, and the chrome pattern 6 is destroyed. Wet etching cannot be used because it becomes easier.

Therefore, when the phase shifter pattern is etched by dry etching, the chromium layer is formed as shown in FIG.
It functions as an etching mask when manufacturing such a phase shift reticle, and as an etching stopper when manufacturing the phase shift reticle as shown in FIG. In such a case, if a combination of low reflection chromium is used as the light shielding layer, the low reflection chromium surface is etched during dry etching, and the surface reflectance increases. When the surface reflectance increases, the light reflected from the surface of the light shielding film during stepper exposure becomes stray light, which causes deterioration of the resist pattern on the wafer. When the light-shielding film is further etched, the optical density of the light-shielding film is lowered. Obviously, if the optical density of the light shielding film is lowered, the resist pattern on the wafer is deteriorated.

Further, when dry etching is performed by using a normal electron beam resist as a mask, if the shape of the electron beam resist is bad, the phase shift pattern is formed by dry etching and the phase shift pattern has vertical side surfaces. Absent.

The present invention has been made in view of the above circumstances, and an object thereof is to prevent deterioration of a light-shielding film during dry etching of a phase shift pattern, and a phase having a phase shift pattern on a vertical side surface. A method of manufacturing a shift photomask is provided.

[0014]

In view of the above-mentioned problems, the present invention, after patterning an electron beam resist, coats a photoresist such as a novolak resin containing a photosensitive group or a phenol resin containing a photosensitive group on the entire mask surface. ,
The entire surface is exposed from the back surface of the mask to form a photoresist pattern, and by using this pattern as a mask for dry etching, deterioration of the low-reflection light-shielding layer is prevented,
Moreover, they have found that a phase shift pattern having vertical side surfaces can be formed and completed the present invention.

The first method of manufacturing the phase shift reticle of the present invention will be described below with reference to FIG. FIG. 1 is a cross-sectional view showing one of the steps of manufacturing a phase shift reticle according to the present invention. As shown in FIG. 1 (a), a chromium / low-reflection chromium two-layer film as a light-shielding film is formed on a glass substrate 13. A chrome reticle having a light-shielding pattern 15 consisting of is prepared. The layer 14 is a transparent conductive film for preventing charge-up.

As the light-shielding film 15, a chromium / low-reflection film chromium two-layer film is shown, but single-layer chromium, chromium oxide film, chromium oxynitride film, tungsten, molybdenum silicide, etc. are used as a photomask light-shielding film. Other materials or composite films of these materials are applicable as well. Further, since quartz glass having a small coefficient of thermal expansion is generally used as the substrate 13 because high accuracy is required, low thermal expansion glass, soda lime glass or the like can also be applied.

Next, as shown in FIG. 1B, a SOG (spin on glass) film 16 is formed on the entire surface of the chrome reticle.
= [Lambda] / 2 (n-1). This SOG
Instead of the film 16, sputtered SiO ₂ , CVD (Chemica
l vapor deposition) SiO ₂ or SiN film may be used.

Then, an ionizing radiation resist layer containing a dye and containing novolac resin as a main component is formed on the chrome reticle having the SOG film 16, alignment is performed according to a conventional method, and a predetermined amount is given by ionizing radiation from an electron beam exposure apparatus or the like. A pattern is drawn, developed, and rinsed to form an ionizing radiation resist pattern 17, as shown in FIG. As the ionizing radiation resist, it is possible to use a resist having a function of reducing light transmittance, other than a resist containing a novolac resin as a main component.

Next, as shown in FIG. 3D, a photoresist 18 containing a novolac resin as a main component is formed on the entire surface of the chrome reticle on which the ionizing radiation resist pattern 17 is formed.
Coating. Other than the photoresist containing a novolac resin as a main component, any resist having dry etching resistance can be used.

Next, the entire surface of the mask is exposed 19 from the back surface of the mask, and as shown in FIG.
8 is formed. When the photoresist pattern 18 is formed, a dye-containing resist is used as the ionizing radiation resist 17 formed on the shifter layer 16, the ionizing radiation resist 17 absorbs light, and the portion where the ionizing radiation resist 17 is formed. Transmittance is reduced. For this reason, the photoresist 18 remains sufficiently on the ionizing radiation resist 17 and has a sufficient thickness as an etching mask.

Next, as shown in FIG. 6F, the SOG is formed by using the formed photoresist pattern 18 as a mask.
Layer 16 is dry etched using reactive plasma 20 to form phase shifter layer 16.

Next, as shown in FIG. 3G, the remaining resist is ashed and removed by oxygen plasma to complete the phase shift photomask. The removal of the resist is
Instead of the dry etching using oxygen plasma, it is also possible to perform the wet method by using a resist-dedicated stripping solution, acid, or the like.

In the above steps, when the resist used for the ionizing radiation resist pattern 17 has dry etching resistance, it is not always necessary to include a dye in the resist. When a dry etching resistant resist containing no dye is used, as shown in FIG.
In (e), the photoresist pattern 18 formed by the overall exposure 19 from the back surface of the mask is formed only on the light shielding pattern 15. During the dry etching in FIG. 1F, the photoresist pattern 18 on the light shielding pattern 15 and the ionizing radiation resist pattern 17 on the position where the phase shifter is to be formed act as a dry etching mask, and the light shielding layer 15 is formed. And the phase shifter layer 16 will be protected from etching.

Now, instead of the phase shift photomask in which the phase shifter layer 16 is provided on the substrate on which the light shielding pattern 15 is formed as described above, the light shielding pattern is provided on the substrate on which the phase shifter layer is formed as shown in FIG. The manufacturing method of the present invention can also be applied to a phase shift photomask.

That is, referring to FIG. 2, the transparent conductive film 22 is formed on the quartz substrate 21 as shown in FIG.
A substrate on which is formed is prepared. Next, as shown in FIG. 3B, the SOG film 23 is formed on the SOG film 23 by d = λ / 2 (n−1).
A light-shielding film 24 made of chrome and low-reflection chrome is formed thereon to have a film thickness that satisfies the above requirements.

On this substrate, as shown in FIG.
An ionizing radiation resist 25 is coated, and drawing is performed in accordance with a light shielding film pattern by ionizing radiation 26 such as an electron beam exposure device. After developing and rinsing, an ionizing radiation resist pattern 25 is formed as shown in FIG. Using this resist pattern 25 as a mask, the chrome / low-reflection chrome 24 is etched to form a light-shielding film pattern 24 as shown in FIG.

On this substrate, as shown in FIG.
Coating an ionizing radiation resist 27 containing a dye,
Next, alignment is performed according to a conventional method, and a portion corresponding to the phase shifter is drawn by the ionizing radiation 28 such as an electron beam exposure device. After developing and rinsing, an ionizing radiation resist pattern 27 is formed as shown in FIG.

Next, as shown in FIG. 3H, a photoresist 29 is coated on the entire surface of this reticle. Then, the entire surface is exposed to ultraviolet rays 30 from the back surface of the mask.
Next, development and rinsing are performed, and as shown in FIG.
A photoresist resist pattern 29 is formed on a portion corresponding to the phase shifter pattern and the chrome pattern 24.

Next, as shown in FIG. 3J, the SOG is formed using the formed photoresist pattern 29 as a mask.
The phase shifter pattern 2 is formed by dry etching the layer 23.
3 is formed. Then, as shown in FIG. 6K, the remaining resist is ashed and removed by oxygen plasma, and the phase shift photomask is completed.

Also in this case, when the resist used for the ionizing radiation resist pattern 27 has dry etching resistance, it is not always necessary to include a dye in the resist.

As described above, the method of manufacturing a phase shift photomask according to the present invention includes a phase shift photo mask having a light shielding pattern and a phase shifter which provides a phase difference between transparent regions which are separated by the light shielding region and are adjacent to each other. In the method for manufacturing a mask, the step of forming a phase shifter is performed by using an ionizing radiation resist on the surface of a substrate on which at least a light-shielding pattern and a transparent film having a uniform thickness are formed. A step of forming a pattern, a step of coating a photoresist on the entire surface of the substrate on which the ionizing radiation resist pattern is formed, and exposing the entire surface from the back surface of the substrate to form a photoresist pattern on at least a portion corresponding to the light shielding pattern; Photoresist pattern or this photoresist pattern A transparent film of uniform thickness by an ionizing radiation resist pattern as a mask is a manufacturing method characterized by comprising the step of forming the phase shifter pattern is dry-etched.

In this case, it is possible to use an electron beam resist of a color in which the ionizing radiation resist blocks or attenuates the exposure light, a laser-sensitive resist or the like.

On the surface of the substrate on which the ionizing radiation resist pattern is formed, a light-shielding pattern and a transparent film having a uniform thickness may be laminated in this order, and conversely, a transparent film having a uniform thickness and a light-shielding film may be laminated. You may laminate | stack in order of a pattern.

[0034]

In the present invention, the step of forming the phase shifter is performed by ionizing the portion corresponding to the phase shifter pattern using the ionizing radiation resist on the surface of the substrate on which at least the light shielding pattern and the transparent film having a uniform thickness are formed. A step of forming a radiation resist pattern, a step of coating a photoresist on the entire surface of the substrate on which the ionizing radiation resist pattern is formed, and exposing the entire surface from the back surface of the substrate to form a photoresist pattern on at least a portion corresponding to the light shielding pattern. , A step of forming a phase shifter pattern by dry etching a transparent film having a uniform thickness using this photoresist pattern or this photoresist pattern and an ionizing radiation resist pattern as a mask. Since it is formed in a self-aligned manner, It is possible to prevent damage of the light shielding film in etching. That is, it is possible to suppress the decrease in blackening density and the decrease in surface reflectance of the light shielding film. Also, the side surface of the phase shifter pattern can be made vertical.

Therefore, it is possible to prevent the pattern transferred onto the wafer from being deteriorated by preventing the low reflection layer of the light-shielding film from being damaged and preventing the optical density from decreasing.

[0036]

EXAMPLES Examples of the present invention will be described below. Example 1 A description will be given with reference to FIG. As shown in FIG.
On a glass substrate 13 on which a transparent conductive film ITO 14 is formed with a thickness of 50 nm, a chrome reticle having a pattern 15 made of chrome and low reflection chrome, which is a light shielding film, is prepared, and as shown in FIG. An SOG film 16 having a refractive index of 1.41 is formed on the entire surface of the chrome reticle to a film thickness of 445 nm.

Then, as shown in FIG.
An electron beam resist SA is formed on the chrome reticle provided with the film 16.
L603 (manufactured by Shipley Co., Ltd.) was spin-coated to a film thickness of 0.5 μm, then alignment was performed according to a conventional method, SAL603 was drawn by an electron beam exposure apparatus, developed and rinsed to form a SAL603 resist pattern 17. Form.

Next, as shown in FIG.
03 Photoresist AZ5200 (made by Hoechst) 18 on the entire surface of the chrome reticle on which the resist pattern 17 is formed
Is coated to a film thickness of 1 μm, and the entire surface is exposed from the back surface of the mask with the g-line 19. Next, development and rinsing are performed to form an AZ5200 resist pattern 18 on a portion corresponding to the phase shifter pattern and the chrome pattern, as shown in FIG.

Next, as shown in FIG. 3F, the AZ5200 resist pattern 18 thus formed is used as a mask for S
The OG layer 16 is dry-etched using the C ₂ F ₆ gas 20 to form the phase shifter layer 16.

The remaining resist is ashed and removed by oxygen plasma to complete a phase shift photomask as shown in FIG. In the phase shift photomask thus completed, deterioration of the light shielding pattern 15 was not recognized, and the side faces of the phase shift pattern 16 were vertical.

Example 2 This example will be described with reference to FIG. As shown in FIG. 3A, the transparent conductive film ITO2 is formed on the quartz 21.
A substrate on which 2 is formed with a thickness of 50 nm is prepared. Next, as shown in FIG. 7B, the
The G film 23 is formed to a film thickness satisfying 445 nm, and then the light shielding film 24 made of chromium and low reflection chromium is formed to have a thickness of 0.1 μm.

On this substrate, as shown in FIG.
An electron beam resist SAL601 (manufactured by Shipley) 25 is spin-coated to a film thickness of 0.5 μm, and then the electron beam resist 25 is drawn by an electron beam 26 by an electron beam exposure device. After development and rinsing, the figure (d)
As shown in, an electron beam resist pattern 25 is formed. Using this resist pattern 25 as a mask, the chromium / low-reflection chromium layer 24 is etched with a cerium nitrate / ammonium nitrate solution, and as shown in FIG.
The light shielding film pattern 24 is formed.

On this substrate, as shown in FIG.
An electron beam resist SAL603 (manufactured by Shipley) 27 is spin-coated to a film thickness of 0.5 μm, then alignment is performed according to a conventional method, and the electron beam resist 27 in the portion corresponding to the phase shifter is covered with an electron beam exposure apparatus. Drawing with the electron beam 28, development and rinsing are performed to form an electron beam resist pattern 27 as shown in FIG.

Next, as shown in FIG. 6H, a photoresist AZ5200 (made by Hoechst) is formed on the entire surface of the reticle.
29 is coated to have a film thickness of 1 μm, and the entire surface is exposed from the back surface of the mask with the g-line 30. Next, development
After rinsing, as shown in (i) of the figure, AZ5 is applied to a portion corresponding to the phase shifter pattern and the chrome pattern 24.
A 200 resist pattern 29 is formed.

Next, as shown in FIG. 7J, the AZ5200 resist pattern 29 thus formed is used as a mask for S
The OG layer 23 is dry-etched using C ₂ F ₆ gas to form the phase shift pattern 23.

The remaining resist is ashed and removed by oxygen plasma to complete a phase shift photomask as shown in FIG. In the phase shift photomask thus completed, deterioration of the light shielding pattern 24 was not recognized, and the side surface of the phase shift pattern 23 was vertical.

[0047]

As described above, according to the method of manufacturing the phase shift photomask of the present invention, the step of forming the phase shifter is performed at least on the substrate surface on which the light shielding pattern and the transparent film having a uniform thickness are formed. , A step of forming an ionizing radiation resist pattern in a portion corresponding to the phase shifter pattern using the ionizing radiation resist, and a photoresist is coated on the entire surface of the substrate on which the ionizing radiation resist pattern is formed, and the entire surface is exposed from the back surface of the substrate. A step of forming a photoresist pattern on at least a portion corresponding to the light-shielding pattern, and a phase shifter pattern by dry etching a transparent film having a uniform thickness using this photoresist pattern or this photoresist pattern and an ionizing radiation resist pattern as a mask. And the process of forming Since the mask for etching is formed in a self-aligned manner, it is possible to prevent damage to the light-shielding film during dry etching. That is, it is possible to suppress the decrease in blackening density and the decrease in surface reflectance of the light shielding film. Also, the side surface of the phase shifter pattern can be made vertical.

Therefore, it is possible to prevent the pattern transferred onto the wafer from being deteriorated by preventing the low reflection layer of the light-shielding film from being damaged and from lowering the optical density.

The process of coating the entire surface of the mask with photoresist, exposing and developing from the back side does not require a special device such as a vacuum device, and therefore the cost required for manufacturing the phase shift photomask does not increase so much. ..

[Brief description of drawings]

FIG. 1 is a cross-sectional view of each step of one embodiment of a method for manufacturing a phase shift photomask according to the present invention.

FIG. 2 is a cross-sectional view of each step of the manufacturing method of another embodiment.

FIG. 3 is a diagram showing the principle of a phase shift photomask.

FIG. 4 is a diagram showing the principle of a conventional photomask.

FIG. 5 is a cross-sectional view of another structure of the phase shift photomask.

FIG. 6 is a first step of manufacturing a conventional phase shift photomask.
It is sectional drawing which shows an example.

[Explanation of symbols]

 13 ... Transparent substrate 14 ... Transparent conductive film 15 ... Light-shielding layer 16 ... Phase shifter layer 17 ... Ionizing radiation resist layer 18 ... Photoresist layer 19 ... Whole exposure light 20 ... Reactive plasma

Claims (5)

[Claims] 1. In a method of manufacturing a phase shift photomask having a light-shielding pattern and a phase shifter for providing a phase difference between transparent regions which are separated by a light-shielding region and are adjacent to each other, the step of forming the phase shifter includes at least light-shielding. A step of forming an ionizing radiation resist pattern on a portion corresponding to the phase shifter pattern using the ionizing radiation resist on the surface of the substrate on which the transparent film having a uniform thickness is formed, and the substrate on which the ionizing radiation resist pattern is formed. A step of coating a photoresist on the entire front surface and exposing the entire surface from the back surface of the substrate to form a photoresist pattern on at least a portion corresponding to the light-shielding pattern, and using this photoresist pattern or this photoresist pattern and an ionizing radiation resist pattern as a mask A transparent film with a uniform thickness. A method of manufacturing a phase shift photomask, which comprises a step of performing line etching to form a phase shifter pattern. 2. The method of manufacturing a phase shift photomask according to claim 1, wherein the ionizing radiation resist is an electron beam resist of a color that shields or attenuates exposure light. 3. The method of manufacturing a phase shift photomask according to claim 1, wherein the ionizing radiation resist is a laser-sensitive resist. 4. The light-shielding pattern and a transparent film having a uniform thickness are laminated in this order on the surface of the substrate on which the ionizing radiation resist pattern is formed, according to any one of claims 1 to 3. Phase shift photomask manufacturing method. 5. The transparent film having a uniform thickness and a light-shielding pattern are laminated in this order on the surface of the substrate on which the ionizing radiation resist pattern is formed, according to any one of claims 1 to 3. Phase shift photomask manufacturing method.