KR20090044422A - Method for fabricating photo mask to suppress haze - Google Patents

Abstract

Forming a light transmission control layer on a transparent substrate, a thermal oxidation process for the light transmission control layer to form a haze suppression layer on the surface of the light transmission control layer, patterning the haze suppression layer and the light transmission control layer A photomask manufacturing method for forming a mask pattern is presented.

Haze, MoSiN, Thermal Oxidation, Silicon Diffusion, Ammonia

Description

Method for fabricating photo mask to suppress haze

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to semiconductor manufacturing, and more particularly, to a method of manufacturing a photo mask that suppresses haze.

A photo mask is used in a lithography exposure process for implementing a circuit pattern of a semiconductor device on a wafer. As the degree of integration of semiconductor devices increases, the line width of the pattern to be transferred onto the wafer becomes smaller. Accordingly, in order to increase the resolution of the pattern, an exposure source of shorter wavelength band is used for the exposure process. As an exposure source of short wavelength band is used, haze may be caused to the photo mask by relatively strong light energy.

Haze may be caused from a phenomenon in which residual ions remaining on the surface of the photo mask from the manufacturing process cause an optical reaction by energy of an exposure source. Such residual ions may be ions such as SO _x , NO _x , PO _x , F, Cl, NH ₄ , Ca, Mg, and the like. Substantially, due to the increased exposure energy when using an exposure source in the wavelength range of 248 nm or less, the optical reaction between residual ions remaining on the mask surface causes growth defects such as haze.

In order to suppress the haze, the cleaning process is strengthened during the mask manufacturing process. However, when the molybdenum alloy layer containing molybdenum (Mo) is used during the mask manufacturing process, it is difficult to sufficiently suppress the haze by such cleaning alone. For example, molybdenum silicon nitride (MoSiN) used as a phase inversion layer in a phase inversion mask (PSM) may react with a cleaning solution containing ammonia to produce a compound such as 6 (NH ₄ ) ₇ MoO ₃ . As a result, it is difficult to use a standard cleaning SC-1 cleaning process containing ammonia. In addition, it is difficult to suppress the reaction between the ammonia and the MoSiN layer, which may be present in trace amounts in the atmosphere in the wafer fab. As a result, a cleaning method that does not contain sulfuric acid or ammonia has been sought. However, there is a need for development of a new haze suppression method due to a decrease in defect removal rate during cleaning.

The present invention is to propose a method for manufacturing a photo mask that can prevent the growth defects by inhibiting the production of haze (haze).

One aspect of the invention, forming a light transmission control layer on a transparent substrate; Performing a thermal oxidation process on the light transmission control layer to form a haze suppression layer on the surface of the light transmission control layer; And forming a mask pattern by patterning the haze suppression layer and the light transmission control layer.

The light transmission control layer may include a layer containing silicon (Si). In this case, the thermal oxidation process may be performed by thermal diffusion of the silicon and oxidation of the diffused silicon.

The light transmission control layer containing silicon may be formed including a molybdenum silicon nitride (MoSiN) alloy layer.

The forming of the mask pattern may include forming a light blocking layer on the haze suppression layer; Selectively etching the light blocking layer, the haze suppression layer, and the light transmission control layer sequentially; Selectively removing a portion of the light blocking layer to expose a surface of the haze suppression layer to form the mask pattern including the haze suppression layer and the light transmission control layer; And cleaning the exposed portions of the mask pattern and the transparent substrate.

The cleaning may be performed using a cleaning liquid containing ammonia.

Embodiment of the present invention, by performing a thermal oxidation process on the light transmission control layer to form a haze suppression layer including an oxide layer, it is possible to suppress the generation of haze by the molybdenum alloy material constituting the light transmission control layer. have.

Embodiments of the present invention provide a method of forming a haze suppression layer that blocks and inhibits the generation of haze by a thermal oxidation process on a light transmission control layer such as a molybdenum silicon nitride (MoSiN) layer. The haze suppression layer may include silicon oxide (SiO ₂ ) formed by oxidation of silicon (Si) diffused from a lower MoSiN layer. By the thermal oxidation process, the haze suppression layer including silicon oxide may be grown to a thickness of about several tens of microseconds.

1 illustrates a step of forming the light transmission control layer 200 on a transparent substrate 100 such as a quartz substrate. The light transmission control layer 200 may be used as a layer inducing phase inversion and may be formed of a layer containing silicon. For example, a phase inversion layer such as molybdenum silicon nitride (MoSiN) alloy or molybdenum silicon (MoSi) alloy may be used. The light transmission control layer 200 may be deposited by a sputtering process.

2 shows a step of forming a haze suppression layer 201 on the surface of the light transmission control layer 200 by a thermal oxidation process. At least a high temperature heat treatment is performed on the light transmission control layer 200 to provide an oxidizing atmosphere. For example, heat treatment is performed by providing an atmosphere gas containing oxygen gas. Due to the thermal energy provided in the heat treatment, silicon (Si) atoms in the light transmission control layer 200 diffuse to the surface, and the diffused silicon atoms react with an oxidizing gas such as oxygen to form silicon oxide (SiO ₂ ) and the like. Produces the same thermal oxide. The thermal oxide is grown to form a haze suppression layer 201.

As shown in FIG. 6, the haze suppression layer 201 formed by the thermal oxidation process may be confirmed by its component graph. FIG. 6 shows the results of analyzing the components by performing an etching or milling process on the haze suppression layer 201 grown by thermal oxidation on the MoSiN layer. As the etching process proceeds, the component of Si increases, and an increase of O ₂ is also observed. The results of FIG. 6 demonstrate that the haze suppression layer 201 can be grown on a layer containing silicon oxide only by a thermal oxidation process without introducing a separate silicon source.

The haze suppression layer 201 including silicon oxide blocks the contact and reaction between MoSiN and ammonia, thereby suppressing haze generation. Ammonia and the like may be present as residual ions on the photomask in the patterning process or the cleaning process for manufacturing the photomask. Since the haze suppression layer 201 is introduced on the MoSiN layer, the environment in which MoSiN directly reacts with ammonia ions and the like is blocked. In addition, since the haze suppression layer 201 covers the surface even after the MoSiN layer is patterned, ammonia or the like present in the air during the subsequent exposure process is sufficiently prevented from contacting and reacting with the MoSiN.

In addition, the silicon oxide may be etched together by an etching gas for dry etching the MoSiN of the light transmission control layer 200. Therefore, in the process of selectively etching the subsequent light transmission control layer 200 to form a mask pattern, a separate etching step for etching the haze suppression layer 201 may not be additionally introduced. Thus, the introduction of further process steps can be prevented.

Referring to FIG. 3, a light blocking layer 300 such as chromium (Cr) is deposited on the light transmission control layer 200, and the first resist pattern 400 is exposed to electron beam exposure and development on the light blocking layer 300. Form. Subsequently, the light blocking layer 300, the haze suppression layer 201, and the light transmission control layer 200 are sequentially etched sequentially using the first resist pattern 400 as an etching mask. Thereafter, after the first resist pattern 400 is removed and first cleaned, the second resist pattern 500 is formed as shown in FIG. 4. The second resist pattern 500 is formed to selectively cover only the patterned light shielding layer portion 301 positioned at the edge portion of the substrate 100.

Subsequently, an etching process for selectively removing other portions of the inner light blocking layer 300 exposed by the second resist pattern 500 is performed. Accordingly, as shown in FIG. 5, a mask pattern including a haze suppression layer 201 and a light transmission control layer 200 having exposed surfaces is formed. The photo mask including the mask pattern has a phase inversion mask structure.

In the photomask thus formed, a haze suppression layer containing silicon oxide by thermal oxidation protects the surface of the MoSiN layer. Therefore, it is possible to suppress the phenomenon that haze-induced residual ions such as ammonia and the like are activated by exposure energy and react with MoSiN or Mo. That is, defect generation due to haze generation can be suppressed. In addition, since the MoSiN layer is protected, the surface of the photomask can be cleaned using a cleaning solution containing ammonia or the like after patterning. As a result, the cleaning efficiency with respect to the photomask surface can be increased, and defect generation can be prevented more stably.

1 to 5 are cross-sectional views schematically illustrating a method of manufacturing a photomask according to an embodiment of the present invention.

FIG. 6 is a component graph presented to explain a haze suppression layer according to an embodiment of the present invention.

Claims (5)

Forming a light transmission control layer on the transparent substrate; Performing a thermal oxidation process on the light transmission control layer to form a haze suppression layer on the surface of the light transmission control layer; And And forming a mask pattern by patterning the haze suppression layer and the light transmission control layer. The method of claim 1, The light transmission control layer is formed to include a layer containing silicon (Si), The thermal oxidation process is performed with thermal diffusion of the silicon and oxidation of the diffused silicon. The method of claim 2, The light transmission control layer containing the silicon A photomask manufacturing method comprising a molybdenum silicon nitride (MoSiN) alloy layer. The method of claim 1, Forming the mask pattern is Forming a light shielding layer on the haze suppression layer; Selectively etching the light blocking layer, the haze suppression layer, and the light transmission control layer sequentially; Selectively removing a portion of the light blocking layer to expose a surface of the haze suppression layer to form the mask pattern including the haze suppression layer and the light transmission control layer; And Cleaning the exposed portion of the mask pattern and the transparent substrate. The method of claim 1, Said cleaning is performed using a cleaning liquid containing ammonia.

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