JP4997371B2 - Mask pattern forming method - Google Patents

Description

The present invention relates to a method for forming a mask pattern, and in particular, exposure by a combination of a chemically amplified negative photoresist (positive photo resist) and a positive photoresist (positive photo resist). The present invention also relates to a mask pattern forming method capable of reducing a pattern pitch by development.

As semiconductor products are miniaturized and highly integrated, interest in patterning technology for forming patterns is increasing in order to improve new functions of devices. The current patterning technology having a high degree of integration has been developed as a core technology for semiconductor manufacturing, and a photolithography process is mainly used. In such a photolithography process, a photoresist (Photo Resist; PR), which is a chemical substance that is sensitive to light irradiation, is applied to form a photoresist film, which is then exposed and developed. After forming the mask pattern, patterning is performed by selectively etching the lower film using the formed mask pattern.

Generally, the process capability limit (resolution) of the photoresist film exposure equipment used for patterning is 1/2 of the pattern pitch (Pitch) defined by the sum of the line pattern (Space) and space (Space). The half pitch (Half Pitch) that is double is shown as a reference.

The resolution of the exposure equipment developed so far is 45 nm on the basis of the half pitch, and in order to increase the net die, it is required to reduce the pattern pitch or the half pitch.

  Therefore, the present invention provides a mask pattern forming method capable of forming a mask pattern having a pattern pitch that is half the resolution of the exposure equipment by exposure and development by a combination of a chemically amplified negative photoresist and a positive photoresist. The purpose is to provide.

In order to achieve the above object, a method for forming a mask pattern according to the present invention forms a negative photo resist film on a substrate. A partial region of the negative photoresist film is exposed. The negative photoresist film is developed. A positive photoresist film is formed on the substrate including a negative tone working photoresist film. The substrate is baked so that hydrogen gas diffuses into the positive photoresist film at the boundary of the negative tone working photoresist film. Develop the positive photoresist film.

The method further includes forming a bottom anti-reflective coating (BARC) film before forming the negative photoresist film. Each of the negative photoresist film and the positive photoresist film is formed of a chemically amplified photoresist.

The sum of the spaces between the negative tone working photoresist film and the negative tone working photoresist film has a pattern pitch that is twice the resolution of the exposure equipment. The positive photoresist film takes into account the thickness of hydrogen gas that diffuses into the side of the negative tone working photoresist film by baking, and the thickness of the upper portion of the negative tone working photoresist film is the side of the negative tone working photoresist film. It is formed thinner than the thickness of the hydrogen gas that diffuses into the surface. The positive photoresist film is formed such that the hydrogen gas diffused to the side of the negative tone working photoresist film is thinner than the upper part.

For the mask pattern, the positive photoresist film containing diffused hydrogen gas on the side of the negative tone working photoresist film is removed, and the pattern pitch is adjusted so as to be the target interval. The mask pattern is formed by alternately repeating the negative tone working photoresist film and the positive tone working photoresist film separated by a space.

The mask pattern has the same pattern pitch as the resolution of the exposure equipment, with the sum of the negative tone working photoresist film or the positive tone working photoresist film and the space.

The present invention forms a mask pattern whose pattern pitch is reduced by a factor of two compared to the case of using only one type of existing photoresist film in exposure and development by a combination of a chemically amplified negative photoresist and a positive photoresist. Can do.

The present invention can increase the number of net dies by using a mask pattern having a reduced pattern pitch in a semiconductor element manufacturing process.

Hereinafter, an embodiment of the present invention will be described in more detail with reference to the accompanying drawings. However, the embodiments of the present invention may be modified in various different forms, and the scope of the present invention should not be construed as being limited by the embodiments detailed below, and is universal in the industry. It is preferably construed as being provided to provide a more thorough explanation of the present invention to those skilled in the art.

1 and 2 are process cross-sectional views illustrating a mask pattern forming method according to an embodiment of the present invention.

Referring to FIG. 1A, a bottom anti-reflective coating (BARC) film 110 is formed on the substrate 100. The BARC film 110 is formed in order to control the reflected light of the exposure source reflected from the surface of the substrate 100, and is not necessarily formed.

A negative photo resist film 120 is formed on the BARC film 110. Desirably, the negative photoresist film 120 is formed of a chemically amplified resist.

The chemically amplified resist means a resist having a quantum yield of more than 100%, and is based on a resin (Resin) and a photo acid generator (PAG), and has improved contrast and solubility. A reaction inhibitor (Inhibitor) may be used for control. Here, as a chemically amplified resist, a part of polyhydroxystyrene (PHST) resin is replaced with a t-butthoxycarbonyl (t-BOC) group at an appropriate ratio (n / m). Thus, a matrix resin with controlled solubility in a developer can be used. In this case, the negative photoresist film 120 can be formed by a spin coating method.

Referring to FIG. 1B, a partial region of the negative photoresist film 120 is exposed. Here, ArF or KrF can be used as the exposure source. In this way, the acid formed by exposure is reduced to Ot-BOC with OH and dissolved in an alkaline solution.At this time, the hydrogen gas (H +) emitted as a by-product again becomes the surrounding t- It is used to deprotect BOC and has an amplification effect. As a result, an exposed negative photoresist film 120a containing hydrogen gas (H +) is formed.

In particular, the present invention removes the thickness of the positive photoresist film (not shown) on the side wall of the negative photoresist film 120a exposed through a subsequent baking process to remove the thickness of the hydrogen gas (H +) diffused. This is controlled by adjusting the exposure amount to adjust the thickness of the hydrogen gas (H +) that diffuses into the positive photoresist film.

Referring to FIG. 1C, the exposed negative photoresist film 120a is developed. The photoresist film 120a exposed by the hydrogen gas (H +) formed by exposure undergoes a crosslinking reaction with the photoresist remains undissolved in the developer. As a result, a negative tone working photoresist film 120b, which is a photoresist in which an exposed portion remains in a pattern after exposure, is formed.

The sum of the first spaces 120c between the negative tone working photoresist film 120b and the negative tone working photoresist film 120b is defined by the pattern pitch (P1), and is an interval twice the exposure equipment resolution.

Referring to FIG. 2A, a positive photoresist film 130 is formed on the substrate 100 including the negative tone working photoresist film 120b. Desirably, the positive photoresist film 130 is formed of a chemically amplified resist, and in this case, it can be formed by a spin coating method.

Here, the thickness of the positive photoresist film 130 formed on the negative tone working photoresist film 120b is a hydrogen gas (H +) on the side of the negative tone working photoresist film 120b through a subsequent baking process. The developing solution is made thinner than the thickness removed by diffusion, so that the developing solution can penetrate into a lower portion of a positive photoresist film (not shown) in which hydrogen gas (H +) is diffused.

Referring to FIG. 2B, the substrate 100 on which the positive photoresist film 130 is formed is baked. As a result, hydrogen gas (H +) is diffused by a predetermined thickness over the entire surface of the negative tone working photoresist film 120b, and a positive photoresist film 130a in which hydrogen gas (H +) is diffused is formed. At this time, the positive photoresist film 130a in which hydrogen gas (H +) is diffused is formed such that the thickness of the side portion of the negative tone working photoresist film 120b is thicker than the thickness of the upper portion of the negative tone working photoresist film 120b.

Referring to FIG. 2C, only the positive photoresist film 130 in which hydrogen gas (H +) is diffused is selectively developed. In this case, the positive photoresist film 130a in which the hydrogen gas (H +) is diffused is removed by dissolving the hydrogen gas (H +) in the developer by causing a decomposition reaction with the photoresist. As a result, a positive tone working photo resist layer 130b is formed.

As a result, the negative tone working photoresist film 120b and the positive tone working photoresist film 130b formed thicker than the negative tone working photoresist film 120b are separated by the second space 130c, and the mask pattern 140 that is alternately repeated is completed. Is done. Here, since the positive tone working photoresist film 130b is formed between the negative tone working photoresist film 120b, the interval between the second spaces 130c is more positive than the first space 120c in FIG. The ton-working photoresist film 130b and the second space 130c are thinned.

As described above, the mask pattern 140 includes the second space 130c between the negative tone working photoresist film 120b or the positive tone working photoresist film 130b, the negative tone working photoresist film 120b, and the positive tone working photoresist film 130b. Pattern pitch (P2) defined by the sum of the two, which is the target interval. Therefore, the pattern pitch (P2) of the mask pattern 140 according to the present invention is 1/2 times smaller than the pattern pitch (P1) formed by exposure and development using only the negative photoresist film 120. That is, the mask pattern 140 according to the present invention can implement a pattern pitch having the same interval as the resolution of the exposure equipment.

The mask pattern 140 formed in this manner is used as a hard mask for forming an actual pattern such as a gate electrode or a bit line in a semiconductor device process. Through this, the pattern pitch is reduced. The net die can be increased.

As described in detail above, the present invention has been described with reference to a preferred embodiment. However, the present invention is not limited to this, and any person having ordinary knowledge in the technical field to which the present invention belongs can be used. Various modifications can be made within the scope of the claims, the detailed description of the invention, and the attached drawings, and these are naturally within the scope of the present invention.

It is process sectional drawing which showed the mask pattern formation method by the Example of this invention. It is process sectional drawing which showed the mask pattern formation method by the Example of this invention.

Explanation of symbols

100: PCB
110: Bottom diffuse antireflection film
120: Negative photoresist film
120a: Exposed negative photoresist film
120b: Negative tone working photoresist film
120c: 1st space
130: Positive photoresist film
130a: Positive photoresist film diffused by hydrogen gas
130b: Positiveton working photoresist film
130c: 2nd space
140: Mask pattern

Claims (8)

Forming a negative photoresist film on the top of the substrate with a chemically amplified photoresist ;
Exposing a partial region of the negative photoresist film;
Developing the exposed negative photoresist film; and
Forming a positive photoresist film with a chemically amplified photoresist on the substrate including the negative tone working photoresist film formed by the development; and
Baking the substrate such that H ⁺ diffuses into the positive photoresist film at the boundary of the negative tone working photoresist film;
And developing a positive photoresist film in which the H ⁺ is diffused. The method of claim 1, further comprising a step of forming a bottom irregular reflection preventing film before the step of forming the negative photoresist film. The mask pattern formation according to claim 1, wherein a sum of spaces between the negative tone working photoresist film and the negative tone working photoresist film has a pitch that is twice the resolution of an exposure equipment. Method. The positive photoresist film takes into account the thickness of H ⁺ diffused to the side of the negative tone working photoresist film by baking, and the thickness of the upper portion of the negative tone working photoresist film is the negative tone working photoresist film. 2. The method of forming a mask pattern according to claim 1, wherein the mask pattern is formed thinner than the thickness of H ^<+> diffusing to the side of the film. The method of claim 1, wherein the positive photoresist film is formed such that a thickness of H ⁺ diffused on a side portion of the negative tone working photoresist film is thinner than an upper part. 2. The mask pattern according to claim 1, wherein the positive photoresist film containing diffused H ⁺ on the side of the negative tone working photoresist film is removed, and the pattern pitch is adjusted to be a target interval. The mask pattern formation method as described in any one of. The method of claim 1, wherein the mask pattern is formed by alternately repeating the negative tone working photoresist film and the positive tone working photoresist film separated by a space. The mask pattern, the sum of the space between the negative tone working photoresist film and the positive tonnes working photoresist film, according to claim 7, characterized in that it has the same pattern pitch and exposure equipment resolution Mask pattern forming method.

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