KR20090047011A

KR20090047011A - Method for fabricating photomask in semiconductor device

Info

Publication number: KR20090047011A
Application number: KR1020070112965A
Authority: KR
Inventors: 정구민
Original assignee: 주식회사 하이닉스반도체
Priority date: 2007-11-07
Filing date: 2007-11-07
Publication date: 2009-05-12

Abstract

A method of forming a photomask of a semiconductor device according to the present invention may include forming a phase inversion film and a light blocking film on a substrate; Forming a hard mask film having a denser film quality than the photoresist film between the light blocking film and the photoresist film while forming a photoresist film on the light blocking film; Patterning the photoresist film to form a photoresist film pattern exposing the hard mask film; Forming a hard mask film pattern and a light blocking film pattern by an etching process using the photoresist film pattern as a mask; Removing the photoresist film pattern; Measuring a critical dimension of the hard mask film pattern, and correcting the hard mask film pattern having a difference from the target critical dimension; And etching the phase shift layer using the corrected hard mask layer pattern as a mask to form the phase shift layer pattern.

Hard mask, photoresist film, phase shift mask

Description

Method for fabricating photomask in semiconductor device

The present invention relates to a photomask, and more particularly, to a method of forming a photomask of a semiconductor device.

A photomask serves to transfer a pattern including a light blocking film or a phase inversion film onto a wafer to form a desired pattern on the wafer. Such photomasks generally use a binary mask that forms a light blocking film on a substrate and then etches it in a desired pattern so that transmitted light can pass through the substrate and be transferred onto the wafer. However, as the degree of integration of semiconductor devices increases, a mask capable of forming a finer pattern on a wafer than a binary mask is required. Accordingly, a phase shift mask capable of forming a finer pattern on a wafer using a phase inversion material having a transmittance of several percent is proposed and applied.

However, as the degree of integration of semiconductor devices increases, the size of the pattern on the wafer decreases, and the target critical dimension (CD) of the mask used in the photolithography process is also decreasing. In the case of semiconductor devices of 65 nm or less, CD MTT (Mean-to-target) of 3 nm to 4 nm level is required. This level of CD MTT is difficult to meet in the general photomask manufacturing process. There is a critical dimension (CD) correction as a way to satisfy this CD MTT.

The critical dimension (CD) correction is performed by first performing an E-beam writing process on a blank mask on which a phase inversion film, a light blocking film, and a photoresist film are formed on a substrate to form a pattern. Next, the method measures the threshold of the formed pattern, compares the measured threshold with the target threshold, and performs additional etching on the pattern to correct the target threshold. However, the thickness of the photoresist film is reduced in order to improve the CD uniformity of the blank mask currently applied. Therefore, it is difficult to apply a method of correcting the critical dimension by using additional etching. Specifically, when the pattern is formed in a state in which the thickness of the photoresist film of the blank mask is reduced, an extra thickness of the photoresist film may be insufficient during additional etching for the critical dimension correction, thereby damaging the lower film, for example, the phase shift film. This makes additional critical dimension correction difficult. In addition, the upper portion of the photoresist film may be damaged by the cleaning source material in the process of performing the critical dimension correction using the thin photoresist film and then cleaning. As such, when the photoresist film is damaged, an error may occur and increase when etching the lower layer (CD error), which may cause a CD uniformity error.

A method of forming a photomask of a semiconductor device according to the present invention includes forming a phase inversion film and a light blocking film on a substrate; Forming a photoresist film on the light blocking film, and forming a hard mask film having a denser film quality than the photoresist film between the light blocking film and the photoresist film; Patterning the photoresist film to form a photoresist film pattern exposing the hard mask film; Forming a hard mask layer pattern and a light blocking layer pattern by an etching process using the photoresist layer pattern as a mask; Removing the photoresist film pattern; Measuring a critical dimension of the hard mask film pattern and correcting a hard mask film pattern having a difference from a target critical dimension; And etching the phase shift film using the corrected hard mask film pattern as a mask to form a phase shift film pattern.

In the present invention, after the step of forming the phase inversion film pattern, forming a mask film to fill the phase inversion film pattern to the hard mask film pattern; Patterning the mask film to form a mask film pattern defining a light blocking region and a phase inversion region; Selectively exposing the transparent substrate using the mask layer pattern as an etching mask; Etching the hard mask layer pattern and the light blocking layer pattern in the phase shift region; And removing the mask layer pattern.

The hard mask layer is preferably formed by selecting one or more materials from the group consisting of a silicon oxynitride (SiON) film, a titanium nitride (TiN) film, and a bottom anti-reflective film (BARC).

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention.

1 to 9 are diagrams for explaining a method of forming a photomask of a semiconductor device according to an embodiment of the present invention.

Referring to FIG. 1, a phase shifter layer 105 and an absorber layer 110 are sequentially deposited on a substrate 100. Here, the substrate 100 includes quartz and is made of a transparent material that can transmit light. The phase shift film 105 deposited on the substrate 100 is made of a material capable of inverting the phase of light irradiated onto the substrate 100 in a subsequent exposure process. The phase inversion film 105 may include a compound containing molybdenum (Mo), for example, a molybdenum silicon nitride film (MoSiON). The light blocking film 110 formed on the phase inversion film 105 blocks light transmitted through the substrate 100 in an exposure process to be performed later. The light blocking film 110 may include a chromium film Cr. Here, in the conventional case, a chromium oxide film is formed as the anti-reflection film on the light blocking film 110, but the chromium oxide film is not formed in the embodiment of the present invention.

Referring to FIG. 2, a hard mask film 115 is deposited on the light blocking film 110. The hard mask film 115 serves to protect the lower film in an additional etching process to proceed to correct the critical dimension thereafter. The hard mask film 115 may be formed by selecting one or more materials from a group consisting of a silicon oxynitride (SiON) film, a titanium nitride (TiN) film, and a bottom anti-reflective coating (BARC). have. Next, a first mask film 120 is formed on the hard mask film 115. The first mask layer 120 may serve as an etching mask in an exposure process and may be formed as a photoresist layer. The hard mask film 115 may be formed of a film having a denser film quality than the first mask film 120.

Referring to FIG. 3, the first mask layer 120 is patterned to form a first mask layer pattern 125 that selectively exposes the hard mask layer. Specifically, a first photolithography process including an exposure and development process is performed on the first mask layer 120. Then, a difference in solubility due to a photochemical reaction occurs in a region where light is irradiated on the first mask layer 120. In addition, when the portion in which the solubility difference appears using the developer is removed, the first mask layer pattern 125 may be formed to selectively expose the surface of the hard mask layer 115. In this case, the primary photolithography process may be performed by using an E-beam exposure apparatus.

Referring to FIG. 4, the hard mask layer 115 having the first mask layer pattern 125 as a mask is etched to form a hard mask layer pattern 130. The hard mask film pattern 130 exposes a portion of the surface of the light blocking film 110. Subsequently, the light blocking layer 110 having the first mask layer pattern 125 and the hard mask layer pattern 115 as a mask is etched to form a light blocking layer pattern 135 for selectively exposing the phase inversion layer 105. do.

Referring to FIG. 5, the first mask layer pattern 125 is removed. The first mask layer pattern 125 may be generally removed using a strip process of removing the photoresist layer pattern. Next, the critical dimension CD of the hard mask film pattern 130 formed on the substrate 100 is measured by using a critical dimension measuring device. In this case, the threshold dimension CD of the hard mask layer pattern 130 formed on the substrate 100 may be formed as a threshold dimension b of a value deviating by a predetermined range from the target threshold dimension a. As such, when the photomask is formed in a pattern having a threshold dimension (b) out of a target threshold dimension (a), a problem may occur in that a final pattern to be formed on a wafer has a bad pattern. Accordingly, it is preferable to correct the threshold of the hard mask film pattern 130.

Referring to FIG. 6, the hard mask film pattern 130 and the light blocking film pattern 135 are additionally etched by a predetermined thickness c to correct the critical dimensions of the hard mask film pattern 130 and the light blocking film pattern 135. . In the conventional case, a method of correcting the critical dimension of the light blocking layer pattern 135 using the first mask layer pattern 125 is used. However, in the conventional case, the first mask layer pattern 125 including the photoresist layer reduces the initial thickness to improve the uniformity of the critical dimension. Accordingly, there is a difficulty in applying the method of correcting the critical dimension by using additional etching because the thickness of the first mask layer pattern 125 is thin. For example, if the pattern is formed in a state in which the thickness of the first mask layer pattern 125 is reduced, an extra thickness of the photoresist layer may be insufficient during additional etching, thereby damaging the lower phase inversion layer. On the other hand, in the exemplary embodiment of the present invention, the hard mask layer 130 may be added below the first mask layer pattern 125 to prevent defects caused by the thickness of the first mask layer pattern 125. Next, cleaning is performed on the substrate on which further etching has been performed. This cleaning serves to remove residues or impurities caused on the substrate 100 during the further etching process. In this case, in the conventional case, the first mask layer pattern 125 may be further etched and then cleaned to damage the upper portion of the first mask layer pattern 125 by the cleaning source material. As described above, when the mask is formed while the upper portion of the first mask layer pattern 125 is damaged, the critical dimension error may be large or the uniformity of the critical dimension may be uneven. However, in the present invention, the additional etching is performed using the hard mask film pattern 130 and the cleaning solution is not affected by the cleaning solution.

Referring to FIG. 7, the substrate 100 is selectively exposed by etching the hard mask layer pattern 130 having the corrected critical dimension by the additional etching and the phase shift layer 105 exposing the light blocking layer pattern 135 as a mask. A phase inversion film pattern 140 is formed. Subsequently, a second mask layer 145 is formed to fill the hard mask layer pattern 130 to the phase inversion layer pattern 140. The second mask layer 145 may be formed as a photoresist film.

Referring to FIG. 8, the second mask layer 145 is patterned to form a second mask layer pattern 150 having an opening that exposes a region where the phase shift region and the light transmissive region are to be formed. Specifically, a second photolithography process including an exposure and development process is performed on the second mask film 145. Then, a difference in solubility occurs due to a photochemical reaction in a region where light is irradiated on the second mask layer 145. In addition, when the portion having the difference in solubility is removed using a developer, a second mask layer pattern 150 for selectively exposing the hard mask layer pattern 130 and the substrate 100 is formed. In this case, the second photolithography process may be performed by using an E-beam exposure apparatus. Next, the hard mask film pattern 130 of the portion where the phase inversion region is to be formed is removed.

Referring to FIG. 9, the light blocking layer pattern 135 in the region where the hard mask layer pattern 130 is removed is etched using the second mask layer pattern 150 as a mask to expose the phase shift layer pattern 140. Here, a portion blocked by the hard mask layer pattern 130 and the light blocking layer pattern 135 becomes a light blocking region A, and a portion where the phase shift layer pattern 140 is exposed becomes a phase inversion region B. The exposed portion of the substrate 100 becomes the light-transmitting region (C).

In the method of forming a photomask of a semiconductor device according to the present invention, CD MTT errors may be reduced by performing critical dimension correction using a hard mask film during a mask manufacturing process. The CD correction error and the CD uniformity defect caused by the damage of the photoresist film pattern can be eliminated.

Claims

Forming a phase inversion film and a light blocking film on the substrate;

Forming a photoresist film on the light blocking film, and forming a hard mask film having a denser film quality than the photoresist film between the light blocking film and the photoresist film;

Patterning the photoresist film to form a photoresist film pattern exposing the hard mask film;

Forming a hard mask layer pattern and a light blocking layer pattern by an etching process using the photoresist layer pattern as a mask;

Removing the photoresist film pattern;

Measuring a critical dimension of the hard mask film pattern and correcting a hard mask film pattern having a difference from a target critical dimension; And

And etching the light blocking film and the phase inversion film using the corrected hard mask film pattern as a mask to form a phase inversion film pattern.

The method of claim 1,

After the forming of the phase shift film pattern,

Forming a mask film to fill the phase shift pattern with the hard mask pattern;

Patterning the mask film to form a mask film pattern defining a light blocking region and a phase inversion region;

Selectively exposing the transparent substrate using the mask layer pattern as an etching mask;

Etching the hard mask layer pattern and the light blocking layer pattern in the phase shift region; And

And removing the mask layer pattern.

The method of claim 1,

The hard mask layer may be formed by selecting one or more materials from the group consisting of a silicon oxynitride (SiON) film, a titanium nitride (TiN) film, and a bottom anti-reflective film (BARC).