Methods for forming fine photoresist patterns

A method of forming a fine pattern by a tri-layer resist process to overcome a bi-layer resist process is disclosed. When a fine pattern is formed using a silicon photoresist, a gas protection film is coated on a photoresist to prevent exhaustion of silicon gas generated from the photoresist in light examination of high energy. As a result, lens of exposure equipment may be prevented from being contaminated.

This application claims priority to foreign application 2003-42523 filed in the Republic of Korea on Jun. 27, 2003.

TECHNICAL FIELD

The forming of fine photoresist patterns using a tri-layer resist process is disclosed which overcomes problems associated with bi-layer resist processes. As disclosed herein, when a fine photoresist pattern is formed using a silicon photoresist, a gas protection film is coated on a photoresist to prevent exhaustion of silicon gas generated from the photoresist in light examination of high energy. As a result, contamination of the lens of the exposure equipment can be prevented.

DESCRIPTION OF THE RELATED ART

As the size of photoresist pattern used in a semiconductor processes becomes smaller, the thickness of photoresist must be thinner. However, as the thickness of photoresist becomes thinner, the photoresist does not adequately serve as an etching mask in a subsequent etching process. In order to overcome this drawback, a bi-layer resist process has been introduced.

Referring toFIG. 1a, a layer30is coated on an underlying layer20of a semiconductor substrate10. The layer30is used as an etching mask when the underlying layer20is etched. The etching mask layer30is generally an i-line photoresist hardened at a high temperature.

A photoresist40which responds to light is coated on the etching mask layer30. Here, the photoresist40includes silicon. The above-stacked structure is exposed using an exposure mask50.

After the exposure process shown inFIG. 1a, a wet development process is performed to form a photoresist film pattern42as shown inFIG. 1b.

A dry etching process is performed using the photoresist film pattern42as an etching mask with O2 plasma. Here, the photoresist film pattern42including silicon is changed a silicon oxide film60by oxygen.

The lower etching mask layer30is etched using the silicon oxide film60as an etching mask to form an etching mask pattern32shown inFIG. 1c.

Next, the underlying layer20is etched using the etching mask pattern32formed inFIG. 1c. Then, a cleaning process is performed to form an underlying layer pattern22shown inFIG. 1d.

In order to reduce the size of patterns, high-energy light sources such as ArF (193 nm), VUV (157 nm) or EUV (13 nm) are used in a photolithography process. However, when the exposure process is performed using a high-energy light source, the combination of resins in the photoresist is broken down to generate undesired by-product gases. In the case of photoresist including silicon, silicon gas is created. The silicon gas generated by the exposure process reacts to air and the silicon is transformed into SiO2 and then deposited on the lens. There is no known method for removing SiO2, and the expensive lens of the scanner and the stepper must be frequently replaced.

As a result, it is expensive to use the bi-layer resist process with a photoresist that includes silicon.

SUMMARY OF THE DISCLOSURE

A method of forming a fine pattern using a silicon photoresist is disclosed which prevents generation of silicon gas and the problems associated therewith.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

A method of forming a fine photoresist pattern is disclosed wherein a gas protection film is coated on the photoresist film created with a bi-layer resist process.

A disclosed method for forming a fine pattern comprises:

(a) coating an etching mask layer on an underlying layer;

(b) coating a photoresist composition including silicon on the etching mask layer to form a photoresist film;

(c) coating a gas protection film on the photoresist film;

(d) performing a photolithography process on the resulting structure to form a photoresist film pattern;

(e) etching the etching mask layer of the step (b) using the photoresist film pattern as an etching mask to form an etching mask pattern; and

(f) forming an underlying layer pattern by an etching process using the etching mask pattern.

Although the etching mask layer of the step (a) is not necessarily limited, an I-line photoresist or KrF photoresist having etching resistance to an underlying layer is preferably used.

Preferably, the photoresist film used in the step (b) is one of the photoresist films suitable for a photolithographic process employing light sources such as ArF (193 nm), VUV (157 nm) or EUV (13 nm).

The gas protection film of the step (c) is preferably water-soluble polymer material having excellent permeability to light. The gas protection film is capable of absorbing silicon gas generated from the underlying photoresist film upon exposure to light.

The step (c) comprises:

(c-1) spin coating a gas protection composition on the resultant surface of (b); and

(c-2) baking the coated gas protection composition.

A disclosed method of forming a fine pattern in accordance with certain preferred embodiments will be described in detail with reference to the accompanying drawings.

Referring toFIG. 2a, an etching mask layer130is coated on an underlying layer120of a semiconductor substrate110. The etching mask layer130is generally an i-line photoresist or KrF photoresist hardened at a high temperature.

A photoresist140which responds to light is coated on the etching mask layer130. Here, the photoresist140includes silicon as described above. A gas protection film170is spin coated on the photoresist140, and exposed using an exposure mask150.

A silicon gas generated from the photoresist film by the exposure process is adsorbed onto the gas protection film170. As a result, exhaustion of the silicon gas into the exposure equipment is prevented, and lens of the exposure equipment are not damaged by the oxidized silicon gas (SiO2).

After the exposure process ofFIG. 2a, a photoresist film pattern142is formed via a wet development process.

Since the gas protection film170has excellent permeability to light, light reaches easily the lower photoresist film when the gas protection film170is exposed to light. Additionally, since the gas protection film170comprises a water-soluble polymer, it is easily removed by a wet development process.

A dry etching process using O2 plasma is performed on the etching mask layer130using the photoresist film pattern142formed inFIG. 2bas an etching mask.

The photoresist film pattern142including silicon is transformed into a silicon oxide film160by oxygen. The lower etching mask layer130is etched using the silicon oxide film160as an etching mask to form an etching mask pattern132as shown inFIG. 2c.

The underlying layer120is etching using the etching mask pattern132formed inFIG. 2c. Then, a cleaning solution is performed on the resulting structure: to obtain a desired an underlying layer pattern122as shown inFIG. 2d.

As discussed earlier, when a fine pattern is formed using a silicon photoresist in accordance with the disclosed method, a gas protection film is further coated on a photoresist to effectively prevent exhaustion of silicon gas generated by exposure. Accordingly, lens of exposure equipment may not be contaminated by silicon gas.