JP2003121978A - Method for fabricating halftone phase shifting mask - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for fabricating a halftone phase shifting mask in which high-level cleaning and/or phase contrast adjustment can be carried out during fabrication without adversely affecting a translucent film. SOLUTION: Alkali treatment, acid treatment or both the treatments are carried out in a state where a translucent film pattern is protected with a light shielding film pattern.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photomask used for transferring a fine pattern of an LSI or the like by a projection exposure apparatus, and more particularly to a method for easily obtaining a halftone type phase shift mask with high accuracy. .

[0002]

2. Description of the Related Art In manufacturing a semiconductor LSI or the like, a phase shift mask is used as one of photomasks which are fine pattern transfer masks. This phase shift mask is capable of improving the resolution of the transfer pattern by giving a phase difference between the exposure lights passing through the mask. As one of the phase shift masks, a phase shift mask described in JP-A-4-136854 is known as a mask particularly suitable for transferring an isolated hole or space pattern. This phase shift mask forms a semi-transmissive film on a transparent substrate that transmits light having an intensity that does not substantially contribute to exposure and at the same time shifts the phase of light passing therethrough. By selectively removing, a mask pattern composed of a light-transmitting portion that transmits light of intensity that substantially contributes to exposure and a semi-light-transmitting portion that transmits light of intensity that does not substantially contribute to exposure is formed. It was done. The phase shift mask shifts the phase of light passing through the semi-transparent portion so that the phase of light passing through the semi-transparent portion is substantially inverted with respect to the phase of light passing through the transparent portion. By establishing the relationship, the light passing through the translucent portion and the semi-translucent portion in the vicinity of the boundary and wrapping around due to diffraction cancel each other so that the contrast of the boundary portion can be well maintained. This is commonly called a halftone type phase shift mask. In this phase shift mask, when the wavelength of the exposure light is λ and the refractive index of the semitransparent film to the exposure light is n, the value of the film thickness t of the semitransparent film is generally t = λ / {2 (n -1)}, and the transmissivity of the semitransparent film at the wavelength of the exposure light is usually set to about 1 to 50%. As described above, the halftone type phase shift mask has a semitransparent portion that has both a phase shift function and a light shielding function. That is, this semi-translucent portion is made to function as a phase shift layer in the boundary portion of the pattern, and is made to function as a light shielding layer in the other portions. Therefore, a small amount of leaked light also occurs in a portion where it is ideal to completely block the exposure light. Normally, the total exposure amount is adjusted so that even if the leaked light is present, the exposure is not substantially achieved. To maximize the characteristics of the phase shift mask, the phase shift amount should be 18
Ideally, it is 0 °, but in practice it is about ± 3
It is desirable to be in the range of °. Therefore, for example, a semi-transmissive film (halftone film) having a phase difference of 90 ° <φ <180 ° is formed in advance, and after etching the semi-transmissive film, the glass as the substrate is etched by a predetermined amount to form the glass portion and the semi-transmissive film. JP-A-7-152142 discloses a method in which the total phase difference of the light film portion is 180 °. Further, JP-A-10-104815 discloses a method of etching the glass portion with a hydrofluoric acid solution or steam to adjust the phase difference. The halftone phase shift mask containing chromium as a main component is a very simple and effective method because only the glass portion is etched by the hydrofluoric acid solution or vapor.

[0003]

However, in the above publication, for example, in the case of a molybdenum silicide-based semi-transparent film containing molyphden, silicon, oxygen, and nitrogen as main constituents, not only the glass part but also the molybdenum is formed by the above method. The silicide-based semi-translucent film is also slightly etched, but there is a problem that desired characteristics cannot be obtained. This is because the aqueous solution of hydrofluoric acid or vapor is originally used to etch the silicon oxide-based material, so that the oxygen-silicon bonding material contained in the molybdenum silicide-based semi-transparent film is also etched at the same time. Is. Also, in general, for cleaning photomasks,
For example, pickling with hot sulfuric acid, ammonia,
There are two types of alkali cleaning using a hydrogen peroxide solution and a mixed aqueous solution of water, but the latter cleaning method has a problem of low resistance in cleaning the above-mentioned molybdenum silicide-based semi-transparent film. That is, the components constituting the film are eluted by the alkaline aqueous solution, and the optical properties such as the phase difference and the transmittance of the film are changed. Therefore, when carrying out alkali cleaning, special consideration was required, such as limiting the cleaning time and adjusting the concentration of the aqueous solution.

In view of the above problems, according to the present invention, in a phase shift mask, especially in a molyfden silicide type halftone phase shift mask, the phase difference can be controlled easily and accurately, and an advanced cleaning can be performed. The present invention provides a method of manufacturing a halftone type phase shift mask that can be manufactured.

[0005]

In order to solve the above problems, the present invention has the following constitution. (Structure 1) A step of sequentially forming a semi-transparent film and a light-shielding film on a transparent substrate, and further forming a resist pattern on the light-shielding film; and etching the light-shielding film using the resist pattern as a mask to form a light-shielding film pattern. A step of forming, a step of forming a semi-transparent film pattern by etching the semi-transparent film using the resist pattern and the light-shielding film pattern as a mask, and then a step of peeling the resist pattern, and Forming a resist pattern on the light-shielding film pattern and etching the light-shielding film pattern using the resist pattern as a mask to form a light-shielding film pattern in a final shape. Forming a semi-transparent film pattern,
A method for manufacturing a halftone phase shift mask, which comprises performing an alkali treatment, an acid treatment, or both treatments after removing the resist pattern.

(Structure 2) A step of sequentially forming a semi-translucent film and a light-shielding film on a transparent substrate and further forming a resist pattern on the light-shielding film; and etching the light-shielding film using the resist pattern as a mask to shield light. A step of forming a film pattern, then a step of peeling off the resist pattern, and then a step of etching the semitransparent film by using the light shielding film pattern as a mask to form a semitransparent film pattern, and thereafter, A step of forming a resist pattern on the light-shielding film pattern and etching the light-shielding film pattern using the resist pattern as a mask to form a light-shielding film pattern in a final shape. In the method for manufacturing a phase shift mask, after forming the semi-transparent film pattern, an alkali treatment or an acid treatment is performed. A method of manufacturing a halftone type phase shift mask, characterized by performing both or both.

(Structure 3) A step of sequentially forming a semi-translucent film and a light-shielding film on a transparent substrate, and further forming a resist pattern on the light-shielding film, and etching the light-shielding film using the resist pattern as a mask to shield light. A step of forming a film pattern, a step of etching the semitransparent film by using the resist pattern and the light shielding film pattern as a mask to form a semitransparent film pattern, and a step of peeling the resist pattern thereafter. In the method for manufacturing a halftone type phase shift mask, the method further includes the step of removing the light-shielding film pattern by etching, and the semi-transparent film pattern is formed, and the resist pattern is peeled off. Halftone characterized by being subjected to alkali treatment or acid treatment, or both of them later. Of manufacturing a die-type phase shift mask.

(Structure 4) The halftone phase shift mask according to any one of Structures 1 to 3, wherein the alkali treatment is treatment with a mixed alkaline aqueous solution of ammonia water, hydrogen peroxide water and water. Manufacturing method.

(Structure 5) The method for manufacturing a halftone phase shift mask according to any one of Structures 1 to 3, wherein the acid treatment is a treatment with a hydrofluoric acid aqueous solution or a hydrofluoric acid vapor.

(Structure 6) The half-tone phase shift according to any one of Structures 1 to 5, wherein the semitransparent film is made of a substance containing metal, silicon, oxygen and nitrogen as main constituent elements. Mask manufacturing method.

(Structure 7) The structure 1 is characterized in that the light-shielding film is made of a substance containing chromium as a main constituent element.
7. A method for manufacturing a halftone phase shift mask according to any one of 6 to 6.

[0012]

In the above structures 1 to 3, alkali treatment or acid treatment is performed in a state where the light-shielding film pattern is present on the semi-light-transmitting film pattern, that is, in a state where the semi-light-transmitting film pattern is protected by the light-shielding film pattern, or It is characterized in that both processes are performed. In this case, the glass etching process for controlling the phase difference can be performed during the mask manufacturing process (before the completion of all patterning processes), and this process can also serve as the mask cleaning process. That is, in the alkali treatment and / or the acid treatment of the present invention, in addition to the cleaning effect, there is an effect of etching the transparent substrate such as quartz glass. That is, it is possible to positively utilize this etching effect to control the phase difference of the mask before the mask is completed. Further, in the present invention, the cleaning process can be performed during the mask manufacturing process under strong conditions that cannot be performed after the mask is completed. By performing the above-described glass etching treatment and / or cleaning treatment under strong conditions, foreign substances strongly attached to the glass surface are removed at this point (improving the cleanliness of the glass portion), and the surface is smoothed. By doing so, it becomes difficult for foreign matter to adhere to the subsequent process as much as possible. Therefore, the work of the post-process can be smoothly advanced. In other words, if there is a foreign substance firmly attached to the glass surface after the mask is completed,
Although a step of rewashing or removing foreign matter by a laser or the like is required, such a step is not necessary in the present invention. By using the above method, it is possible to perform high-level cleaning and / or phase difference adjustment during the manufacture of the halftone phase shift mask without adversely affecting the semi-transparent film, resulting in high quality. A halftone type phase shift mask can be provided with good yield.

In the above-mentioned structure 4, since the alkaline treatment is a treatment with a mixed alkaline aqueous solution of ammonia water, hydrogen peroxide solution and water, the glass etching treatment and / or the cleaning treatment under strong conditions (in the case where glass etching is involved) (Including) can be effectively performed.
For the purpose of avoiding changes in optical characteristics such as phase difference and transmittance of the film, a mixed aqueous solution of ammonia, hydrogen peroxide solution and water, which has a limited cleaning time or an adjusted aqueous solution concentration, is used. Alkaline cleaning used (for example, cleaning time 3 minutes, and ammonia water: hydrogen peroxide water: water =
1: 1: 10 or ammonia water: hydrogen peroxide water: water =
In the case of 0.5: 1: 5) (again, there is almost no glass etching), it is difficult to effectively remove the foreign matter strongly adhered to the glass surface. Therefore, in the configuration 4, the alkali treatment is performed for a treatment time of 3 to 10 minutes, ammonia water: hydrogen peroxide water: water = 1: 1: 2 to 1: 1:
It is preferably 7.

In the constitution 5, the acid treatment is a treatment with a hydrofluoric acid aqueous solution or a hydrofluoric acid vapor, so that the glass etching treatment and / or the cleaning treatment under a strong condition (including the case involving the glass etching) can be effectively performed. Can be done. In the case of general acid cleaning using hot sulfuric acid (there is almost no glass etching),
It is difficult to effectively remove foreign matter strongly attached to the glass surface. As a hydrofluoric acid aqueous solution, a buffered hydrofluoric acid is preferable because a normal hydrofluoric acid aqueous solution is strong. The treatment time of the buffered hydrofluoric acid aqueous solution is preferably 1 to 3 minutes and the concentration of the hydrofluoric acid aqueous solution is 2 to 10%.

In the above-mentioned structure 6, when the semi-translucent film is made of a material having metal, silicon, oxygen and nitrogen as main constituents, particularly, molybdenum silicide based material having molyfden, silicon, oxygen and nitrogen as main constituents. In the case of a semi-transparent film, since the oxygen-silicon bond substance contained in the semi-transparent film is easily etched at the same time by the alkali treatment and / or the acid treatment of the present invention, the semi-transparent film pattern is a light-shielding film pattern. It is specified because the necessity of carrying out the alkali treatment and / or the acid treatment of the present invention in a protected state is particularly great.

In the above-mentioned structure 7, since the light-shielding film is composed of a film containing chromium as a main component, it is resistant to alkali and acid, and the semi-translucent film is covered with the light-shielding film, which has no influence. The glass etching process or the cleaning process under strong conditions can be performed without receiving the light.

[0017]

EXAMPLE 1 FIG. 1 is an explanatory view of a manufacturing process of a halftone type phase shift mask according to a first example of the present invention. This embodiment will be described below with reference to this drawing. The transparent substrate 1 is a quartz glass substrate (size 6 inch square, thickness 0.25 inch) whose surface is mirror-polished, and is subjected to predetermined cleaning.
First, a semi-transparent film 2 made of molybdenum, silicon, oxygen, and nitrogen was formed on the transparent substrate 1 by a sputtering method to have a film thickness of 100 μm, and then a light shielding film 3 made of chromium was formed to a film thickness of 100 nm. Next, a positive electron beam resist (ZEP7000: manufactured by Nippon Zeon Co., Ltd.) 4 was applied by a spin coating method to a film thickness of 500 nm (FIG. 1 (a)). Next, a desired pattern was subjected to electronic repetitive writing and developed to form a resist pattern 41 ((b) of the same figure). Next, using the resist pattern 41 as a mask, the light-shielding film 3 was etched by dry etching containing chlorine and oxygen to form a first light-shielding film pattern 31 (FIG. 7C). Next, using the resist pattern 41 and the first light-shielding film pattern 31 as a mask, the semi-translucent film is formed into a mixed gas of CF ₄ / O ₂ , a pressure of 0.
Dry etching was performed under the conditions of 4 Torr and RF power of 100 W to form a semi-transparent film pattern 21 (FIG. 7D). Finally, the resist was peeled off to complete a mask patterned up to the first step ((e) of the same figure). Then, strong alkaline washing was performed for 5 minutes with a mixed aqueous solution of ammonia water: hydrogen peroxide water: water = 1: 1: 5. Then, a photoresist (AZ1350: manufactured by Clariant Co., Ltd.) 5 was applied by a spin coating method to a film thickness of 500 nm and baked (FIG. 6 (f)). Next, a desired pattern was exposed and developed to form a resist pattern 51 ((9) in the same figure). Next, using the resist pattern 51 as a mask, the first light-shielding film pattern 31 was etched using an etching solution composed of ceric ammonium nitrate and perchloric acid to form a second light-shielding film pattern 311 (see FIG. h)). Finally, the resist pattern 51 was peeled off and a predetermined cleaning was performed to obtain a halftone phase shift mask (FIG. 11 (j)). In the subsequent defect inspection, a good quality halftone type phase shift mask could be obtained in a short time without detecting foreign matter. Further, when the phase difference was measured, the phase difference expected from the characteristics of the semi-transparent film and the alkaline cleaning conditions was obtained, and the accurate phase characteristic could be obtained. In addition, ammonia water: hydrogen peroxide water: water = 1:
Instead of alkali cleaning with a 1: 5 mixed aqueous solution, hot concentrated sulfuric acid cleaning or alkali cleaning under conditions weaker than the above alkali cleaning was performed. When formed, it is difficult to remove foreign matter that firmly adheres to the glass surface at this stage, because foreign matter tends to remain, and even if a predetermined cleaning is performed after the mask is completed, the foreign matter is detected in the subsequent defect inspection. It was Therefore, a re-cleaning step and a foreign matter removing step by a laser or the like are required, which requires a considerable time. In addition, repeated washing caused damage to the semi-transparent film, and the phase difference and the refractive index deviated from desired values.

Embodiment 2 FIG. 2 is an explanatory view of a manufacturing process of a halftone type phase shift mask according to a second embodiment of the present invention. This embodiment will be described below with reference to this drawing. The transparent substrate 1 is a quartz glass substrate (size 6 inch square, thickness 0.25 inch) having a mirror-polished surface, which has been subjected to predetermined cleaning.
First, a semi-transparent film 2 made of molybdenum, silicon, oxygen, and nitrogen is formed on a transparent substrate 1 by a sputtering method with a thickness of 160 nm, and then a light-shielding film 3 made of chromium with a thickness of 1 is formed.
It was formed with a thickness of 00 nm. Next, a positive electron beam resist (E
(BR-9: manufactured by Toray) 4 by spin coating
It was applied at a thickness of 00 nm ((a) in the same figure). Next, a desired pattern was drawn with an electron beam and developed to form a resist pattern 41 (FIG. 2B). Next, the resist pattern 41
Using the mask as a mask, the light-shielding film 3 was etched using an etching solution composed of cerium ammonium nitrate and perchloric acid to form a first light-shielding film pattern 31 (FIG. 7C). Next, the resist was peeled off and washed (FIG. 7 (d)). Next, using the first light-shielding film pattern 31 as a mask, the semi-light-transmitting film is formed into a mixed gas of CF ₄ / O ₂ at a pressure of 0.
Dry etching was performed under the conditions of 4 Torr and RF power of 100 W to form a semi-transmissive film pattern 21 (FIG. 8E). Next, the mask was dipped in a buffered hydrofluoric acid aqueous solution for 1 minute to etch the glass portion, and further alkali cleaning was performed for 5 minutes with a mixed aqueous solution of ammonia water: hydrogen peroxide solution: water = 1: 1: 5. Then, a photoresist (AZ1350: manufactured by Clariant Co., Ltd.) 5 was applied by a spin coating method to a film thickness of 500 nm and baked (FIG. 6 (f)). Next, a desired pattern was exposed and developed to form a resist pattern 51 ((9) in the same figure). Next, using the resist pattern 51 as a mask, the first light-shielding film pattern 31 was etched using an etching solution composed of ceric ammonium nitrate and perchloric acid to form a second light-shielding film pattern 311 (see FIG. h)). Finally, the resist pattern 51 was peeled off and a predetermined cleaning was performed to obtain a halftone phase shift mask (FIG. 11 (j)). In the subsequent defect inspection, a good quality halftone type phase shift mask could be obtained in a short time without detecting foreign matter. In addition, when the phase difference was measured, the expected phase difference was obtained from the characteristics of the semi-transparent film, the hydrofluoric acid treatment condition, and the alkaline cleaning condition, and the accurate phase characteristic could be obtained. When the alkali treatment was performed after the acid treatment, the clouding of the glass due to the residual acid could be avoided by the neutralizing effect. In addition, the cleanliness of the glass portion could be further improved by performing ultrasonic treatment in the alkali treatment.

Embodiment 3 FIG. 3 is an explanatory diagram of a manufacturing process of a halftone type phase shift mask according to a third embodiment of the present invention. This embodiment will be described below with reference to this drawing. The transparent substrate 1 is a quartz glass substrate (size 6 inch square, thickness 0.25 inch) having a mirror-polished surface, which has been subjected to predetermined cleaning.
First, a semi-transparent film 2 made of molyfden, silicon, oxygen, and nitrogen was formed on the transparent substrate 1 with a thickness of 160 nm by the spackling method, and then a light shielding film 3 made of chromium was formed with a thickness of 100 nm. Next, a positive type electron beam resist (EBR-9: manufactured by Toray Industries, Inc.) 4 was applied by a spin coating method to a film thickness of 500 nm (FIG. 9A). Next, a resist pattern 4 is formed by drawing a desired pattern with an electron beam and developing it.
1 was formed ((b) of the same figure). Next, using the resist pattern 41 as a mask, the light-shielding film 3 was etched using an etching solution composed of cerium ammonium nitrate and perchloric acid to form a light-shielding film pattern 31 (FIG. 7C). Next, the resist was peeled off and washed (FIG. 7 (d)). Next, using the light-shielding film pattern 31 as a mask, the semi-translucent film is mixed with CF ₄ / O ₂ mixed gas at a pressure of 0.4 To.
Dry etching was performed under the conditions of rr and RF power of 100 W to form a semi-transparent film pattern 21 ((e) of the same figure). With this step, the phase difference expected from the time of forming the semi-transparent film is 175.
It was °. Therefore, from the relationship between the etching time and the phase difference change that was obtained in advance, the mask was immersed in a buffered hydrofluoric acid aqueous solution for 2 minutes to etch the glass portion, and finally ammonia water: hydrogen peroxide water: water = 1: 1: 1.
Alkaline cleaning was performed for 5 minutes with the mixed aqueous solution of No. 5. Next, the light-shielding film 31 was etched (whole surface removed) using an etching solution composed of cerium ammonium nitrate and perchloric acid to obtain a halftone type phase shift mask in the final form (FIG. 6 (f)). In the subsequent imperfection inspection, it was possible to obtain a good quality halftone type phase shift mask in a short time without detecting foreign matter. In addition, when the phase difference was measured, the expected phase difference was obtained from the characteristics of the semi-transparent film, the hydrofluoric acid treatment condition, and the alkaline cleaning condition, and the accurate phase characteristic could be obtained.

In the above embodiment, the single-layer semi-transparent film is exemplified, but the semi-transparent film may be a laminated film of two or more layers having different refractive indexes.

[0021]

According to the present invention, a high degree of cleaning and / or phase difference adjustment can be performed during the manufacture of a halftone type phase shift mask without adversely affecting the semitransparent film, and as a result, A high-quality halftone phase shift mask can be provided with good yield. In addition, the phase difference can be adjusted and the cleanliness of the glass portion can be improved before the mask is completed, and the work of the post-process can be carried smoothly so that the mask can be completed in a short time.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view for explaining a manufacturing process of a halftone type phase shift mask according to an embodiment of the present invention.

FIG. 2 is a partial cross-sectional view for explaining a manufacturing process of a halftone type phase shift mask according to another embodiment of the present invention.

FIG. 3 is a partial cross-sectional view for explaining a manufacturing process of a halftone type phase shift mask according to still another embodiment of the present invention.

[Explanation of symbols]

1 transparent substrate 2 Semi-transparent film 3 Light-shielding film 4 resist 5 resist 21 Semi-transparent film pattern 31 First light-shielding film pattern 41 resist pattern 51 resist pattern 311 Second light-shielding film pattern

Claims (7)

[Claims] 1. A step of forming a semi-translucent film and a light-shielding film in order on a transparent substrate, and further forming a resist pattern on the light-shielding film; and a step of etching the light-shielding film using the resist pattern as a mask to form the light-shielding film pattern. And a step of forming a semi-transparent film pattern by etching the semi-transparent film using the resist pattern and the light-shielding film pattern as a mask, and then a step of peeling the resist pattern, Then, a step of forming a resist pattern on the light-shielding film pattern and etching the light-shielding film pattern using the resist pattern as a mask to form a light-shielding film pattern in a final shape. In the method of manufacturing a tone type phase shift mask, the semi-transparent film pattern is formed, and the resist is formed. After peeling off the turn, alkali treatment or acid treatment to,
Or a method of manufacturing a halftone type phase shift mask, characterized in that both processes are performed. 2. A step of sequentially forming a semi-translucent film and a light-shielding film on a transparent substrate, and further forming a resist pattern on the light-shielding film; and a step of etching the light-shielding film using the resist pattern as a mask to form the light-shielding film pattern. Forming a semi-transparent film pattern by etching the semi-transparent film using the light-shielding film pattern as a mask, and then the light-shielding step Forming a resist pattern on the film pattern, and etching the light-shielding film pattern using the resist pattern as a mask to form a final shape of the light-shielding film pattern. In the mask manufacturing method, after forming the semi-transparent film pattern, an alkali treatment or an acid treatment is performed. Or the method of manufacturing a halftone phase shift mask, characterized in that the processing of both. 3. A step of forming a semi-transmissive film and a light-shielding film in order on a transparent substrate, and further forming a resist pattern on the light-shielding film; and a step of etching the light-shielding film using the resist pattern as a mask to form a light-shielding film pattern. And a step of forming a semi-transparent film pattern by etching the semi-transparent film using the resist pattern and the light-shielding film pattern as a mask, and then a step of peeling the resist pattern, Then, in the method of manufacturing a halftone phase shift mask, characterized in that it comprises a step of removing the light-shielding film pattern by etching, after forming the semi-transmissive film pattern and peeling the resist pattern, Alkali treatment or acid treatment,
Or a method of manufacturing a halftone type phase shift mask, characterized in that both processes are performed. 4. The halftone phase shift mask according to claim 1, wherein the alkali treatment is a treatment with a mixed alkali aqueous solution of ammonia water, hydrogen peroxide solution and water. Production method. 5. The acid treatment is a treatment with a hydrofluoric acid aqueous solution or hydrofluoric acid vapor.
A method for manufacturing a halftone phase shift mask according to any one of 1. 6. The halftone type phase shift mask according to claim 1, wherein the semi-transparent film is made of a substance containing metal, silicon, oxygen and nitrogen as main constituent elements. Manufacturing method. 7. The method of manufacturing a halftone phase shift mask according to claim 1, wherein the light-shielding film is made of a substance containing chromium as a main constituent element.