KR20100081608A - Method for forming photomask to suppress haze - Google Patents

Abstract

PURPOSE: A method for forming photomask to suppress a haze is provided to minimize damage to a light shield film by removing residual ion from the surface of the phase inversion layer pattern. CONSTITUTION: A phase inversion layer(110) and a light shield layer are formed on a transparent substrate. A first resist film is coated on the light shield layer. The exposure and the development process of using an electronic beam are performed on the first resist film to form the first resist layer pattern. An etching process is performed by using first resist layer pattern as an etching mask to from the light shield film pattern(121) and the phase inversion layer pattern(111) .

Description

Method for forming photomask to suppress haze}

The present invention relates to a method of forming a photomask, and more particularly, to a method of forming a photo mask that suppresses haze.

The semiconductor device manufacturing process uses a lithography process using a photomask. As circuit pattern sizes of semiconductor devices become smaller, high energy exposure light sources, such as ArF light sources, are used in the lithography process. Since such high energy light is irradiated to the photomask, a problem arises in that ions remaining in the photomask are generated as growthable foreign substances or haze. These hazes are growthable foreign substances such as ammonium sulfate ((NH ₄ ) ₂ SO ₄ ) or ammonium nitrate ((NH ₄ ) ₂ NO ₃ ), and the sulfide ions (SO ₄ ²⁾ remaining from the photomask cleaning process or wet etching process. ^- ) And ammonia ions (NH ^{4 +} ) are probably the cause.

After rinsing with sulfuric acid and hydrogen peroxide mixture (SPM), hot rinse with high temperature deionized water (DIW) or heat-treatment to prevent haze. In this regard, a method of inducing decomposition of residual ions by or additionally performing washing with ozone water in combination with these methods may be considered.

By the way, the cleaning process using ozone water and ultraviolet (UV) irradiation is evaluated to have a limited cleaning ability compared to the SPM, there is a limit to sufficiently remove various contaminants and foreign substances that may occur during the mask manufacturing process. Accordingly, there is a method of decomposing and removing residual ions through the heat treatment by introducing a heat treatment to the photomask, but it is evaluated that there is a limit in decomposing and removing residual sulfide ions by the heat treatment. have. Therefore, the development of the method which can suppress the haze generation | occurrence | production of a photomask is calculated | required.

A photomask forming method of suppressing haze according to the present invention includes forming a molybdenum silicon nitride film (MoSiN) pattern on a quartz substrate; Wet cleaning the molybdenum silicon nitride film (MoSiN) pattern; And etching the molybdenum silicon nitride film (MoSiN) pattern and the substrate surface using chlorine gas and oxygen gas as an etchant to remove ions remaining during the cleaning.

The etching step may further include exciting the chlorine gas and oxygen gas into a plasma.

The etching step may provide the chlorine gas and the oxygen gas in a volume ratio of 4: 1 so that the molybdenum silicon nitride film (MoSiN) pattern and the quartz substrate are etched at an etching rate of 0.2 nm / min.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

1 to 4 are schematic views for explaining a method of forming a photomask to suppress haze according to an embodiment of the present invention. Referring to FIG. 1, a phase inversion film and a light blocking film are formed on the transparent substrate 100. The phase inversion film 110 may be formed using a material including molybdenum (Mo), for example, a molybdenum silicon nitride film (MoSiN). The light blocking film can be formed using, for example, a chromium film Cr. Subsequently, after the first resist film is coated on the light blocking film, an exposure and development process using an electron beam is performed on the first resist film to form the first resist film pattern 130. Next, an etching process using the first resist layer pattern 130 as an etch mask is performed to form the light blocking layer pattern 121 and the phase inversion layer pattern 111, thereby exposing the transparent substrate 100 in a predetermined region. do. Here, the light transmitting area of the photomask is defined by the exposed area of the transparent substrate 100.

Referring to FIG. 2, after removing the first resist film pattern, a second resist film (not shown) is coated on the resultant product on which the light blocking film pattern 121 and the phase inversion film pattern 111 are formed. Next, an exposure and development process using an electron beam is performed on the second resist film to form a second resist film pattern defining the main region A of the photomask. Subsequently, the light blocking film pattern 121 formed in the main region A is removed to expose the phase inversion film pattern 111. Next, the second resist film pattern is removed. In such a series of processes, foreign substances including contaminants such as etching by-products or organic matters may be generated on the surfaces of the transparent substrate 100 and the phase shift pattern 111. In order to remove such foreign matter, a cleaning process and a rinsing process using a cleaning liquid are performed. In this case, the cleaning liquid used may be a mixture of sulfuric acid (H ₂ SO ₄ ) and hydrogen peroxide (H ₂ O ₂ ) (SPM) and ammonia (NH ₄ OH) water diluted with ultrapure water (H ₂ O). The cleaning liquid may remove foreign substances on the surfaces of the transparent substrate 100 and the phase inversion film pattern 111, but residual ions such as sulfide ions (SO ₄ ^2- ) 10 and ammonia ions (NH ⁴⁺ ) by the cleaning liquid may be removed. ) 20 may be adhered to the surfaces of the transparent substrate 100 and the phase shift pattern 111.

Referring to FIG. 3, a fine surface etching process is performed to remove residual ions on the surfaces of the transparent substrate 100 and the phase shift pattern 111. In the surface etching process, residual ions fixed on the surface of the transparent substrate 100 and the phase shift pattern 111 are excited by exciting an etching gas in which chlorine (Cl ₂ ) gas and oxygen (O ₂ ) gas are mixed at a constant volume ratio with plasma. Remove 30. Specifically, the chlorine gas is used to remove the residual ions 30 fixed to the surfaces of the transparent substrate 100 and the phase inversion film pattern 111. However, when the residual ions 30 fixed to the surfaces of the transparent substrate 100 and the phase inversion film pattern 111 are removed using only chlorine gas, the light blocking film pattern 121 may be damaged. Accordingly, the transparent substrate 100 and the phase inversion layer may be removed to minimize the etching of the light blocking layer pattern 121 and to remove residual ions 30 adhered to the surfaces of the transparent substrate 100 and the phase inversion layer pattern 111. It is essential to find process conditions for increasing the etching selectivity of the pattern 111 and the light blocking layer pattern 121. In the case of chlorine plasma etching, the etching selectivity ratio of MoSiN: Cr is about 30: 1. Therefore, since the Cr pattern may be excessively damaged as compared to the MoSiN pattern, it is required to further reduce the etching rate. In order to reduce the etching rate, an additional oxygen gas is provided.

Accordingly, in order to secure an etching selectivity higher than the result of the etching selectivity obtained using the chlorine gas plasma, a gas in which chlorine gas and oxygen gas are mixed at a constant volume ratio is used. Here, chlorine gas and oxygen gas are preferably mixed in a volume ratio of approximately 4: 1. When the etching gas mixed with the chlorine gas and the oxygen gas 4: 1 by volume ratio is excited by the plasma, the transparent substrate 100 and the phase shift film pattern 111 are etched at about 0.2 nm / min. Accordingly, when etching is performed for about 3 minutes, the surfaces of the transparent substrate 100 and the phase shift pattern 111 are estimated to be etched to a thickness of about 0.5 nm to 0.7 nm or less. When the phase inversion film pattern 111 and the transparent substrate 100 are excessively etched, since the pattern line width may deviate greatly from an unintentionally designed value, the pattern line width change may be suppressed by inducing an etching rate low. Accordingly, as shown in FIG. 4, damage to the light blocking layer pattern 121 may be minimized while removing residual ions fixed to the surfaces of the transparent substrate 100 and the phase shift pattern 111. Moreover, by removing residual ions, generation of haze contamination during exposure of the semiconductor substrate can be suppressed in advance, and through this result, the yield of the wafer product can be increased.

1 to 4 are schematic views for explaining a method of forming a photomask to suppress haze according to an embodiment of the present invention.

Claims (3)

Forming a molybdenum silicon nitride film (MoSiN) pattern on the quartz substrate; Wet cleaning the molybdenum silicon nitride film (MoSiN) pattern; And And etching the surface of the molybdenum silicon nitride film (MoSiN) pattern and the substrate using chlorine gas and oxygen gas as an etchant to remove ions remaining during the cleaning. The method of claim 1, The etching step further comprises the step of exciting the chlorine gas and oxygen gas to the plasma haze suppression method of forming a photomask. The method of claim 1, The etching step may include a photomask that suppresses haze for providing the chlorine gas and oxygen gas in a volume ratio of 4: 1 so that the molybdenum silicon nitride film (MoSiN) pattern and the quartz substrate are etched at an etching rate of 0.2 nm / min. Formation method.

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