KR100712991B1 - Method for removing growable residue - Google Patents

Abstract

According to the present invention, there is provided a method of removing growth impurities in a photomask, the method comprising: cleaning a photomask, loading a photomask having been cleaned into a plasma chamber, and inert gas, water, and oxygen in the plasma chamber. Generating a plasma to remove growth foreign matter on the photomask. According to the present invention, it is possible to prevent unwanted pattern transfer in the process of performing the photolithography process, thereby forming a pattern of the desired profile can increase the process yield.

Photomask, cleaning process, growth debris, sulfate ion

Description

Method for removing growable residue in photomask

Figure 1 is a flow chart shown to explain a method for removing growth of foreign matter in the photomask according to the present invention.

Figure 2 is a sulfate ion (SO ₄ ^-) by the method removes foreign substances growth of the photomask according to the present invention, a graph showing the results of comparing to the case of the residual amount of the other methods.

Figure 3 is a sulfate ion (SO ₄ ^-) according to the oxygen plasma treatment time by removing foreign matters growth method of a photomask according to the present invention, a graph showing the change in the remaining amount.

The present invention relates to a photomask used in the photolithography process, and more particularly, to a method for removing growthable foreign matter from the photomask.

Recently, as semiconductor devices are highly integrated, the size of patterns formed on wafers become fine, and photolithography processes using photo masks have been used to form such fine patterns. According to the photolithography process, a photoresist film is coated on a material film on which a pattern is to be formed, and light is injected into a portion of the photoresist film by using a photomask having a predetermined light blocking pattern. Then, a photoresist film pattern in which a part of the photoresist film is removed by development using a developer is formed. Thereafter, the exposed portion of the material film is removed by an etching process using the photoresist film pattern as an etching mask, thereby forming a material film pattern corresponding to the light blocking pattern of the photomask.

However, in performing the photolithography process, when there is foreign matter in the photomask, the foreign matter is transferred to the photoresist film to form a photoresist film pattern having a desired profile, thereby forming an unwanted pattern in the material film. Can be. Therefore, the cleaning process must be performed on the photomask in order to remove foreign substances from the photomask. Typically, the cleaning process for the photomask includes washing with Sulfuric Acid Peroxide Mixture (SPM), which is a mixture of H ₂ SO ₄ , H ₂ O _2, and H ₂ O, and NH ₄ OH, H _2. And washing with Ammonium Peroxide Mixture (APM, SC (Standard Clean) -1), which is a mixture of O ₂ and H ₂ O, as a washing liquid.

By the way, the SPM and SC-1 cleaning can remove foreign matters or unwanted residues on the photomask, but there is a problem that growth foreign materials are generated during the cleaning process. Specifically, sulfate ions (SO ₄ ⁻ ) from the SPM washing liquid and ammonia (NH ₃ ) from the SC-1 washing liquid remain on the photomask, and in particular, the remaining sulfate ions (SO ₄ ⁻ ) and ammonia (NH ₃ ) React with each other to form the (NH ₄ ) ₂ SO ₄ salt. The (NH ₄ ) ₂ SO ₄ silane salt generated as described above acts as a growth foreign material that increases as the exposure is performed by the addition of energy of the light catalyst during the subsequent exposure. Such growth foreign matter causes unwanted pattern transfer, as described above.

The technical problem to be achieved by the present invention is to provide a method for removing growth foreign matters of a photomask that can effectively remove the growth foreign matters formed by the cleaning process.

In order to achieve the above technical problem, the growth of the foreign matter removal method of the photomask according to the present invention, the step of performing a cleaning for the photomask; Loading the cleaned photomask into a plasma chamber; And generating a plasma including inert gas, water, and oxygen in the plasma chamber to remove growth foreign matter on the photomask.

The washing may include a first washing using a sulfuric acid peroxide mixture as a washing liquid, a second washing using an ammonium peroxide mixture as a washing liquid, and a third washing using hot deionized water.

The growth foreign material preferably contains SO ₄ ions.

Preferably, the plasma treatment is performed for at least 90 seconds.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, embodiments of the present invention may be modified in many different forms, and the scope of the present invention should not be construed as being limited by the embodiments described below.

Figure 1 is a flow chart shown to explain a method for removing growth of foreign matter in the photomask according to the present invention.

Referring to FIG. 1, first, a photomask is manufactured using a conventional method. As is well known, there are many types of photomasks, but in this embodiment, a phase shift mask (PSM) having a phase shift film formed of a MoSiON film will be exemplified. In the case of a phase inversion mask, a light blocking film pattern formed of a Cr film and a phase inversion film pattern formed of a MoSiON film are disposed on a quartz substrate. After the phase inversion mask is formed, a cleaning process is performed to remove residues, such as photoresist residues, generated in the process of forming the light blocking film pattern and the phase inversion film pattern.

First, the SPM cleaning is performed as the first step of the cleaning process (step 110). SPM cleaning is performed using a cleaning liquid in which H ₂ SO ₄ , H ₂ O ₂ and H ₂ O are mixed in a proportion. Next, SC-1 cleaning is performed as the second step of the cleaning process (step 120). SC-1 washing is performed using a washing liquid in which NH ₄ OH, H ₂ O ₂ and H ₂ O are mixed in a proportion. Next, as a third step of the washing process, washing using hot deionized water is performed (step 130). After this cleaning process, the residues generated during the manufacturing of the photomask are removed.

Next, a plasma treatment including inert gas, water, and oxygen is performed on the photomask on which the cleaning process is performed (step 140). To this end, a photomask is first loaded into a plasma chamber. Next, an oxygen (O ₂ ) plasma is formed in the plasma chamber. In order to form the oxygen (O ₂ ) plasma, the pressure in the plasma chamber is maintained at approximately 600 mTorr, the power applied is approximately 600 W, and the oxygen (O ₂ ) flow rate is approximately 100 sccm. Oxygen radical (O ^* ) generated here causes a reaction as shown in Formula 2 below.

_{^{SO 4 - + O * → SO}} 2 + O 2 + O

As shown in Chemical Formula 1, oxygen radical (O ^* ) is generated by the cleaning process to remove sulfate ions (SO ₄ ⁻ ) which are a cause of growth foreign matter. In particular, sulfate ion (SO ₄ ⁻ ) is mainly located on the surface or sidewall of the MoSiON phase inversion film. Although the surface of the MoSiON film has a roughness of 10 nm, the above-described oxygen (O ₂ ) plasma treatment is performed. Sulfate ions (SO ₄ ⁻ ) on the surface or sidewall of the MoSiON film can be easily removed.

Figure 2 is a sulfate ion (SO ₄ ^-) by the method removes foreign substances growth of the photomask according to the present invention, a graph showing the results of comparing to the case of the residual amount of the other methods.

Referring to FIG. 2, in the case of reference (see 260), it shows a residual amount of sulfate ion (SO ₄ ⁻ ) of approximately 0.01 ng / cm 2, and as in the present invention, SPM cleaning, SC-1 cleaning and hot desorption When ion water washing was performed (see 250), a residual amount of sulfate ion (SO ₄ ⁻ ) of approximately 1 ng / cm 2 was shown. In contrast, when only SPM cleaning and cold deionized water washing are performed (see 210), the residual amount of sulfate ion (SO ₄ ⁻ ) is approximately 40ng / cm 2, and only SPM washing and SC-1 washing are performed. (see 220), sulfuric acid ions of approximately 30ng / ㎠ (SO ₄ ^-) indicates a residual amount, SPM cleaning, in case of performing only the SC-1 cleaning, and hot de-ionized water washing (see 230) roughly ions of sulfuric 10ng / ㎠ (SO ₄ ^-) represents the remaining amount, and in case of performing only the PM cleaning with SC-1 cleaning (see 240), sulfate ion (SO ₄ of approximately 3ng / ㎠ ^- shows a) the remaining amount. Therefore, it can be seen that the amount of sulfate ions (SO ₄ ⁻ ) is drastically reduced as the oxygen (O ₂ ) plasma is performed as in the present invention.

Figure 3 is a sulfate ion (SO ₄ ^-) according to the oxygen plasma treatment time by removing foreign matters growth method of a photomask according to the present invention, a graph showing the change in the remaining amount.

Referring to FIG. 3, the residual amount of sulfate ion (SO ₄ ⁻ ) gradually decreases as the oxygen (O ₂ ) plasma treatment is performed for 10 seconds to 90 seconds, but the residual amount of sulfate ion (SO ₄ ⁻ ) is greater than 90 seconds. It can be seen that is no longer reduced. Accordingly, the oxygen (O ₂ ) plasma treatment is preferably performed for about 90 seconds or more.

As described above, according to the method for removing growthable foreign matters of the photomask according to the present invention, after the cleaning process for the photomask is performed, the photolithography process is performed by removing the growth foreign matters on the photomask by performing oxygen plasma treatment. Undesired pattern transfer can be prevented in the process of performing, thereby providing an advantage of increasing a process yield by forming a pattern of a desired profile.

Although the present invention has been described in detail with reference to preferred embodiments, the present invention is not limited to the above embodiments, and various modifications may be made by those skilled in the art within the technical spirit of the present invention. Do.

Claims (4)

Performing a cleaning on the photomask; Loading the cleaned photomask into a plasma chamber; And Generating a plasma containing an inert gas, water, and oxygen in the plasma chamber to remove growth foreign matter on the photomask. The method of claim 1, The cleaning includes a first cleaning using a sulfuric acid peroxide mixture as a cleaning liquid, a second cleaning using an ammonium peroxide mixture as a cleaning liquid, and a third cleaning using hot deionized water. Way. The method of claim 1, The growth foreign matter removal method of the growth foreign material of the photomask, characterized in that it comprises SO ₄ ions. The method of claim 1, And the plasma treatment is performed for at least 90 seconds or more.

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