KR20110061981A - Method for cleaning the photomask - Google Patents

Abstract

PURPOSE: A method for cleaning a photomask is provided to improve yield of masks with no defects by suppressing defects generated in an etching process in advance. CONSTITUTION: A method for cleaning a photomask comprises the steps of: forming a phase shift layer(105) and a light shield layer on a light transmissive substrate; forming resist layer patterns(120) on the light shield layer; forming light shield layer patterns(125) through an etching process; irradiating UV to a polymer layer(135) and defect factors(130) attached to the surface of the phase shift layer; supplying a basic cleaning solution and removing the polymer layer and defect factors; and etching an exposed region of the phase shift layer to form the phase shift layer patterns.

Description

Method for cleaning the photomask

The present invention relates to a photomask, and more particularly, to a method for cleaning a photomask.

A photomask serves to transfer a mask pattern formed on a light transmissive substrate to a wafer to form a desired pattern on the wafer. Such a mask pattern generally forms a mask target film made of a light blocking film or a phase inversion film on a light-transmitting substrate, a photoresist film is formed on the mask film, and then subjected to a photolithography process including exposure, development, and etching. Proceeding to form. In the process of forming the mask pattern as described above, in the process of etching the defects in the raw material, the electron beam scattered by the particles generated in the exposure process using the electron beam, the particles or the mask target film generated in the post-exposure bake process and the developing process. The generated particles all act as a source of photomask defects.

The biggest cause of defects in the patterning process from the first exposure process to the etching process to form the pattern is the process of etching the mask target film composed of the light blocking film or the phase inversion film, and 70% to 80% of the total defect causes Corresponds to%. The hard defects of the pattern, which are mainly generated in the etching process, significantly reduce the quality of the photomask. Accordingly, after the etching process, a repair process is performed to remove defects generated in the etching process. The repair process generally removes defects generated on the mask pattern by using a focus ion beam (FIB) device, an electron beam (E-Beam) device, or an atomic force microscopy (AFM) device. . However, the repair process using such a device is limited in the size and type of defects, which makes it difficult to completely eliminate the defects. In particular, when the size of the defect is several μm or more, there is a problem that the defect is difficult to remove even in the repair process.

In addition, even after the defects have been partially corrected by the repair process, when the simulation results are simulated by AIMS (Aerial Image Measurement System) or the printing result actually transferred onto the wafer, it is remarkably different from the critical dimension (CD) of the normally formed pattern. The difference is shown. When the exposure process is performed on the wafer with a pattern having such a line width, a defective pattern is transferred onto the wafer, which leads to device defects.

The technical problem to be achieved by the present invention is to provide a method for cleaning a photomask which can improve the production yield of a defect-free mask by suppressing the cause of defects generated in the etching process to proceed to manufacture the phase inversion mask in advance. .

In accordance with another aspect of the present invention, a method of cleaning a photomask includes: forming a phase inversion film and a light blocking film on a light transmitting substrate; Forming a resist film pattern on the light blocking film to expose a portion of the surface of the light blocking film; Forming a light blocking film pattern exposing a part of the surface of the phase shift film by an etching process using the resist film pattern as an etching mask; UV light is irradiated on the defect cause material and the polymer film which are generated in the process of forming the resist film pattern and the light blocking film pattern and are attached to the exposed surface of the phase inversion film to oxidize the defect cause material and the polymer film. Proceeding with the first cleaning to decompose; Performing a second cleaning step of supplying a basic cleaning solution to remove the defect cause material and the polymer film oxidized and decomposed in the first cleaning; And etching the exposed region of the phase shift film by using the resist film pattern and the light blocking film pattern which have undergone the cleaning, to form a phase shift film pattern.

In the present invention, the first cleaning may include: loading the light transmitting substrate into a cleaning chamber including a chamber, an ultraviolet lamp, and a gas supply unit supplying an inert gas and an oxygen gas; Ozone (O), which is an oxidizing agent that oxidizes and decomposes the defect cause material and the polymer film by reacting the supplied oxygen gas with ultraviolet light by illuminating the ultraviolet lamp on the light transmitting substrate while supplying oxygen gas into the cleaning chamber. ) And free radicals (O); And supplying an inert gas into the cleaning chamber to desorb the oxidized and decomposed defect cause material and polymer film from the adsorbed surface.

The inert gas includes nitrogen gas, and the first cleaning is performed by irradiating ultraviolet rays of 170 nm to 180 nm wavelength for 3 minutes to 5 minutes at an output of 13 mW to 15 mW so that the loss of the resist film pattern does not exceed 3 nm. Do.

Preferably, the inert gas is supplied at a flow rate of 1 ml to 3 ml, and the oxygen gas is supplied at a flow rate of 0.1 ml to 1 ml.

The basic cleaning solution supplies a dilution solution that does not exceed a conductivity of 1 μS, and the basic cleaning solution includes a diluted ammonia solution, an SC-1 solution, and deionized water.

In the second washing step, it is preferable to proceed by applying the ultrasonic vibration of 1-3MHz frequency while supplying the basic cleaning solution.

After the step of performing the second cleaning, it is preferable to proceed for at least 90 seconds at a rotation speed of 1000rpm to 1200rpm in order to remove the moisture on the surface of the phase inversion film.

According to the present invention, in the patterning process for forming the mask pattern, the cleaning step is performed prior to etching the phase inversion film to remove all the defects generated in the process step and the environment immediately after the development process until the light blocking film is etched. In addition, defects may be suppressed during subsequent phase inversion film etching. Accordingly, the mask failure rate can be reduced.

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 6 are diagrams for explaining the cleaning method of the photomask according to an embodiment of the present invention.

Referring to FIG. 1, a phase inversion film 105, a light blocking film 110, and a resist film 115 are sequentially formed on the light transmissive substrate 100. Here, the transparent substrate 100 is made of a transparent material including quartz (Quartz). The phase inversion film 105 formed on the light transmissive substrate 100 is a material capable of inverting the phase of light to be transmitted to the photomask in the exposure process, and includes a compound including molybdenum (Mo), for example Molybdenum silicon oxynitride (MoSiON) film. The light blocking film 110 formed on the phase inversion film 105 may be formed to include a chromium (Cr) film as a film for blocking transmitted light.

Referring to FIG. 2, the resist film 115 is patterned to form a resist film pattern 120 that selectively exposes the surface of the light blocking film 110. Specifically, an exposure step of irradiating light to a portion of the resist film 115 is performed using an exposure apparatus. Then, the photochemical reaction occurs in the portion irradiated with light in the exposure process, resulting in a difference in solubility. Next, a development process of removing the resist film of the portion where the photochemical reaction has occurred in the resist film 115 subjected to the exposure process with a developer is performed to form a resist film pattern 120.

Next, the exposed portion of the light blocking film 110 is etched using the resist film pattern 120 as an etch mask to form the light blocking film pattern 125. The light blocking layer is etched by a dry etching method, and chlorine (Cl) gas plasma is formed as an etching source to proceed isotropically. In this process, the particles 130 generated in the etching process are adsorbed on the side of the light blocking layer pattern 125 and the surface of the resist film pattern 120, or the polymer film 135 generated in the etching process is formed on the surface of the phase inversion layer 105. Can be generated.

On the other hand, when the light blocking film pattern is formed and the phase inversion film etching process is performed continuously, a large number of particles, which are defect causing materials, may be generated to act as a cause of defects. This is because, in contrast to the light blocking layer etching condition having the isotropic etching characteristic, the phase inversion layer etching condition having the anisotropic etching characteristic is transferred to the defect depending on the presence of particles. Specifically, in the case of etching the light blocking film using chlorine plasma, even if particles are present on the surface of the light blocking film due to the anisotropic etching characteristic, the lower end thereof is normally etched. However, the anisotropic (straight-type) etching method of etching a phase shift film using a carbon tetrafluoride (CF ₄ ) plasma or a sulfur hexafluoride (SF ₆ ) plasma may be performed according to the shape of particles when particles are present on the surface of the phase shift film. Transferring to defects leads to mask failure. Accordingly, the presence of particles when etching the phase inversion film may lead to defects. In addition, the etching chamber in which the phase inversion film is etched is maintained relatively clean compared to the etching chamber in which the light blocking film is etched due to the atmosphere characteristics of the gas (carbon tetrafluoride gas or sulfur hexafluoride gas) used in the etching process. Most of the causes of defects in the etching process are classified before etching the phase inversion film.

Accordingly, in the embodiment of the present invention, before the phase inversion film is etched, a defect process is performed by removing a defect causing material including particles generated in the process of etching the light blocking film.

Referring to FIG. 3, ultraviolet rays (UV) are irradiated onto the particles 130 and the polymer layer 135 generated in the process of forming the resist layer pattern 120 and the light blocking layer pattern 125 to form the particles 130 and First cleaning for oxidizing and decomposing the polymer film 135 is performed. The first cleaning proceeds in a dry cleaning manner.

Specifically, the defective light-transmitting substrate 100 is loaded into a cleaning chamber (not shown) including a chamber, an ultraviolet lamp, and a gas supply unit for supplying an inert gas and oxygen (O ₂ ) gas. The cleaning chamber includes an ultraviolet lamp for irradiating ultraviolet (UV) light on the light transmitting substrate 100, a gas supply part for supplying inert gas and oxygen gas into the cleaning chamber, and a discharge part for discharging foreign matters to the outside. . Next, the ultraviolet lamp is turned on to irradiate ultraviolet (UV) light on the light-transmitting substrate 100. In addition, the inert gas and the oxygen (O ₂ ) gas are supplied through the gas supply unit. Wherein the inert gas comprises nitrogen (N ₂ ) gas and is supplied at a flow rate of 1 ml to 3 ml, and oxygen gas is supplied at a flow rate of 0.1 ml to 1 ml. Ultraviolet rays irradiated onto the light-transmitting substrate 100 are irradiated at a wavelength of 170-180 nm, preferably at a wavelength of 172 nm. Ultraviolet rays are irradiated at an output of 10 mW to 15 mW.

If with the irradiation of ultraviolet light onto the transparent substrate 100 is injected with oxygen (O ₂₎ gas, injected into the washing chamber by means of ultraviolet light having energy of oxygen (O ₂₎ gas is monoatomic active oxygen (O), ozone ( O ₃ ) and repeats decomposition and bonding in three states, such as oxygen (O ₂ ), and serves as an oxidant 140 for removing the polymer film 135 formed on the surface of the phase inversion film 105. Oxygen gas and the injected inert gas serve as a carrier gas to desorb oxidized and decomposed particles or polymer film from the attached mask surface. In addition, an oxide film is formed on the surface of the light blocking film pattern 125 by the influence of free radicals (O). Accordingly, the surface of the light blocking layer pattern 120 is changed from a hydrophobic state to a hydrophilic state, thereby facilitating subsequent second cleaning. In this case, the irradiation time of ultraviolet rays is irradiated for 3 minutes to 5 minutes, and the ultraviolet ray output is irradiated with an output of 10 mW to 15 mW so that the loss of the resist film pattern 120 is not exceeded 3.0 nm.

Referring to FIG. 4, the second cleaning is performed by supplying the basic cleaning solution 215 to the particles 130 and the polymer film 135 oxidized and decomposed in the first cleaning using ultraviolet rays. The second cleaning proceeds by wet cleaning. To this end, the transparent substrate 100 subjected to the first cleaning is disposed in the wet cleaning apparatus. The wet cleaning apparatus is a spin type cleaner, and a spray nozzle for supplying the basic cleaning solution 215 onto the chuck 200 and the light transmitting substrate 100 which are rotatable while the light transmitting substrate 100 is disposed. It comprises a portion 210. The translucent substrate 100 subjected to the first cleaning is disposed on the chuck 200 of the wet cleaning apparatus, and the chuck 200 is rotated in one direction on the translucent substrate 100 through the spray nozzle unit 210. The basic cleaning solution 215 is sprayed to remove the oxidized and decomposed particles 130 and the polymer film 135. The basic washing solution 215 is a diluted ammonia solution (Diluted NH ₄ OH), SC-1 (ammonium hydroxide (NH ₄ OH) solution, hydrogen peroxide (H ₂ O ₂ ) and deionized water) solution and deionized water (DIW; Deionized water). In this case, deionized water may be used as cold water or hot water. The basic cleaning solution 215 uses a low concentration diluent that does not exceed 1 μS conductivity.

The second cleaning may be performed by applying ultrasonic vibration of 1-3 MHz frequency while spraying the basic cleaning solution 215 to include physical cleaning. Ultrasonic vibration applied at a frequency of 1-3MHz can improve the cleaning effect through the cavitation effect in the basic cleaning solution and the transfer of the vibration momentum to the particles themselves. The phase inversion film 105 may include the particles 130 and the polymer film 135, which are generated in an etching process that is performed to form the resist film pattern 120 and the light blocking film pattern 125 by the first cleaning and the second cleaning. Can be removed from the surface.

Next, in order to remove moisture on the surface of the phase inversion film 105 which may act as a cause of the defect, a rotary drying process that proceeds for at least 90 seconds at a rotational speed of 1000 rpm to 1200 rpm is further performed.

Referring to FIG. 5, the exposed region of the phase shift film 105 is etched using the resist film pattern 120 and the light shield film pattern 125 to form a phase shift film pattern 140. Here, the phase inversion film 105 is etched after the dry cleaning and the wet cleaning is completed, the etching proceeds in a state in which the defect causing material such as particles are removed, the etching rate (etch rate) at this time Is the same as the case of the etching process in-situ (in-situ), it can be formed with a line width (CD) of the normal pattern accordingly. Next, the resist film pattern 120 is removed.

Referring to FIG. 6, the light blocking layer pattern to be transferred to the main cell region A is removed, and the light blocking layer pattern 125 to be charged to the frame region B is left, so that the phase inversion layer is formed in the main cell region A. The main pattern 140a is formed, and in the frame region A, a mask pattern having a structure in which the phase shift film frame pattern 140b and the light blocking film pattern 125 are stacked is formed.

The present invention performs a cleaning process in which dry cleaning and wet cleaning are sequentially performed before etching to form a phase inversion film pattern, thereby eliminating all defect-causing substances generated in the process and environment from immediately after the developing process to light blocking film etching. It is possible to suppress the occurrence of a hard defect that may occur in the reverse film etching. Through the application of the present process it is possible to improve the manufacturing yield of the defect free mask to 50% or more.

1 to 6 are diagrams for explaining the cleaning method of the photomask according to an embodiment of the present invention.

Claims (9)

Forming a phase inversion film and a light blocking film on the light transmitting substrate; Forming a resist film pattern on the light blocking film to expose a portion of the surface of the light blocking film; Forming a light blocking film pattern exposing a part of the surface of the phase shift film by an etching process using the resist film pattern as an etching mask; UV light is irradiated on the defect cause material and the polymer film which are generated in the process of forming the resist film pattern and the light blocking film pattern and are attached to the exposed surface of the phase inversion film to oxidize the defect cause material and the polymer film. Proceeding with the first cleaning to decompose; Performing a second cleaning step of supplying a basic cleaning solution to remove the defect cause material and the polymer film oxidized and decomposed in the first cleaning; And And etching the exposed region of the phase shift film using the resist film pattern and the light blocking film pattern which have undergone the cleaning to form a phase shift film pattern. The method of claim 1, The method of claim 1, wherein the first cleaning is performed. Loading the translucent substrate into a cleaning chamber comprising a chamber, an ultraviolet lamp and a gas supply for supplying an inert gas and oxygen gas; Ozone (O), which is an oxidizing agent that oxidizes and decomposes the defect cause material and the polymer film by reacting the supplied oxygen gas with ultraviolet light by illuminating the ultraviolet lamp on the light transmitting substrate while supplying oxygen gas into the cleaning chamber. ) And free radicals (O); And And supplying an inert gas into the cleaning chamber to desorb the oxidized and decomposed defect cause material and polymer film from the adsorbed surface. The method of claim 2, The inert gas is a cleaning method of a photomask containing nitrogen gas. The method of claim 1, The first cleaning is a method of cleaning a photomask in which the loss of the resist film pattern is progressed not to exceed 3nm by irradiating ultraviolet rays of 170nm to 180nm wavelength for 13 minutes to 15mW output for 3 minutes to 5 minutes. The method of claim 2, The inert gas is supplied at a flow rate of 1ml to 3ml, and the oxygen gas is supplied at a flow rate of 0.1ml to 1ml. The method of claim 1, The basic cleaning solution is a cleaning method of the photomask to supply a diluting solution that does not exceed the conductivity of 1μS. The method of claim 6, The basic cleaning solution is a method of cleaning a photomask comprising a diluted ammonia solution, SC-1 solution and deionized water. The method of claim 1, The second cleaning step, the cleaning method of the photomask to proceed by applying the ultrasonic vibration of 1-3MHz frequency while supplying the basic cleaning solution. The method of claim 1, After the step of performing the second cleaning, the cleaning method of the photomask further comprises a rotary drying step of proceeding for more than 90 seconds at a rotational speed of 1000rpm to 1200rpm to remove the moisture on the surface of the phase shift film.

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