KR100190083B1 - Method for forming gate electrode of semiconductor device - Google Patents

Abstract

A polysilicon layer and a tungsten silicate layer are sequentially formed on the active region of the semiconductor substrate, an oxide film is formed on the tungsten silicate layer, and the oxide film is patterned to correspond to the gate electrode of the semiconductor device to form an oxide film pattern, A lower structure is patterned using the oxide film pattern as an etching mask to form a polyside structure for the gate electrode, and the polymer adsorbed on the sidewall of the tungsten silicate pattern is removed by oxygen plasma or ozone asher treatment, and the gate electrode The gate electrode is formed by oxidizing the front portion of the film to form a protective oxide film. Therefore, abnormal growth of tungsten silicate grains can be prevented to improve the performance of the LDD transistor.

Description

Gate electrode formation method of semiconductor device

The present invention relates to a method of forming a gate electrode of a lightly doped drain (LDD) transistor, and more particularly, by performing an oxygen plasma treatment in a process of forming a protective oxide film on the front surface of the gate electrode. The present invention relates to a method of forming a gate electrode capable of improving the performance of an LDD transistor by preventing abnormal growth of tungsten silicate forming an electrode polyside structure.

In the semiconductor industry, as the semiconductor devices are highly integrated, the width of the gate electrode of a metal oxide semiconductor (MOS) transistor is gradually decreasing. However, when the width of the gate electrode is reduced by N times, the resistance of the gate electrode is increased by N times, thereby reducing the operation speed of the semiconductor device. Therefore, in order to reduce the resistance of the gate electrode, the low-resistance gate of polycide, which is a laminated structure of the polysilicon layer and the silicide, using the characteristics of the polysilicon layer / oxide layer exhibiting the characteristics of the most stable MOS transistor As a practical application. In addition, a low resistance gate may be formed by stacking a heat resistant metal layer such as tungsten (W) on the polysilicon layer. The most important reason for using polysilicon is that it can be used as a mask to precisely define the source and drain electrodes. This minimizes gate-source / drain overlap, resulting in improved LDD transistor performance.

In the method of forming a gate electrode of a low doping drain (LDD) transistor, after forming a pattern of the gate polysilicon, the gate polysilicon is oxidized at a high temperature before performing an N-type source / drain ion implantation process. The process is essential. This process prevents damage to the lattice of the silicon substrate from ions with high energy. In addition, the shape of the edge of the gate polysilicon is sharp to prevent the gate oxidation due to the concentration of the electric field (electric field).

Recently, in order to improve the speed of DRAM (Dynamic Random Access Memory), low-resistance tungsten silicate (WSix) and polysilicon, a composite film of polysilicon, are used as gate electrode materials, and photoresist (PR) is used. Instead of using it as a mask, a process of patterning an oxide film with a photoresist and patterning a polyside under it using the patterned oxide film as an etching mask has become common.

However, in the case where the protective oxide film is formed on the front surface of the gate electrode after etching the polyside using the oxide film as an etching mask, the polymer or the like generated during the photoresist etching in the previous step partially remains on the wafer and then the tungsten silicate pattern is removed. Can be adsorbed on the sidewalls. As a result, when the protective oxide film is formed on the front surface of the gate electrode at a high temperature, the grains of the tungsten silicate sidewall are abnormally grown unstable, causing an electrical short circuit.

1A to 1D are manufacturing process diagrams of a gate electrode of a conventional LDD transistor.

Referring to FIG. 1A, a field oxide film 3 is formed on a semiconductor substrate 2 to be divided into an active region and an isolation region, and then a gate oxide film is formed on the entire surface of the structure. oxide) (4). Next, polysilicon and tungsten are deposited on the gate oxide film 4 to form a polysilicon layer 6 and a tungsten layer, and then the tungsten layer is heat-treated at a high temperature to form a tungsten silicate layer 8 to form polyside. To form a structure. Next, an oxide film 10 is formed by depositing oxide on the tungsten silicate layer 8 in a plasma enhanced state by a chemical vapor deposition (CVD) method.

Referring to FIG. 1B, after the photoresist is coated on the oxide layer 10 by a spin coating method, the photoresist is patterned using a mask. Then, the oxide film 10 on the tungsten silicate layer 8 is patterned using the patterned photoresist as an etching mask to form an oxide film pattern 10 'for forming a gate electrode, and then the photoresist is removed.

Referring to FIG. 1C, the tungsten silicate layer 8 and the polysilicon layer 6 are sequentially etched using the oxide film pattern 10 ′ as an etching mask, and as illustrated, the tungsten silicate pattern 8 ′ and poly A polyside structure for a gate electrode formed of a composite pattern structure of the silicon pattern 6 'is formed.

Referring to FIG. 1D, a protective oxide film 11 is formed by performing normal wet cleaning and oxidizing the front surface portion including the sidewall portion of the tungsten silicate pattern 8 'of the gate electrode at a high temperature of about 850 ° C.

However, the polymer or the like generated during the patterning of the photoresist may remain partially on the wafer and be adsorbed onto the tungsten silicate pattern 8 'sidewall of the gate electrode because it cannot be completely removed in the wet cleaning. Thus, an abnormal reaction of tungsten silicate is caused in the process of forming the protective oxide film 11 on the front surface of the gate electrode, resulting in a short circuit, thereby degrading the performance of the LDD transistor.

An object of the present invention is to form a polyside structure for a gate electrode made of a composite pattern structure of tungsten silicate pattern and polysilicon pattern in the process of forming a protective oxide film on the front surface of the gate electrode in order to solve the above-mentioned conventional problems The present invention provides a method of forming a gate electrode capable of improving the performance of an LDD transistor by preventing an abnormal reaction of tungsten silicate grains, which is caused in a process of forming a protective oxide film on a front surface of the gate electrode, by performing an oxygen plasma treatment later. It is.

1A to 1D are manufacturing process diagrams of a gate electrode of a conventional LDD transistor.

2A to 2E are process drawings of the gate electrode of the LDD transistor according to the present invention.

Explanation of symbols for the main parts of the drawings

2, 12: semiconductor substrate 3, 13: field oxide film

4, 4 ', 14, 14': gate oxide film

6, 6 ', 16, 16': polysilicon layer

8, 8 ', 18, 18': tungsten silicate layer

10, 10 ', 20, 20': oxide film 11, 21: protective oxide film

22: oxygen plasma

In order to achieve the above object of the present invention, a method of forming a gate electrode according to the present invention comprises the steps of sequentially forming a polysilicon layer and a tungsten silicate layer on the active region of the semiconductor substrate; Forming an oxide film on the tungsten silicate layer; Patterning the oxide film to correspond to the gate electrode of the semiconductor device to form an oxide pattern for forming the gate electrode; Patterning a lower structure using the oxide layer pattern as an etching mask to form a polyside structure for the gate electrode; Removing the polymer adsorbed on the sidewalls of the tungsten silicate pattern forming the polyside structure for the gate electrode; And oxidizing the front surface of the gate electrode to form a protective oxide film.

Preferably an oxygen plasma is used to oxidize the adsorbed polymer on the sidewalls of the tungsten silicate pattern.

Preferably, an ozone asher is used to oxidize the adsorbed polymer on the sidewalls of the tungsten silicate pattern.

When oxygen plasma is used, the process is relatively simple, can be used in a wide range of conditions, and can also reduce damage to the polyside structure formed at the previous stage, that is, polysilicon, tungsten silicate pattern and protective oxide film.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

2A through 2E are manufacturing process diagrams illustrating a method of forming a gate electrode during a manufacturing process of an LDD transistor according to an exemplary embodiment of the present invention.

Referring to FIG. 2A, a field oxide layer 13 is formed on a semiconductor substrate 12 to be divided into an active region and an isolation region, and then a gate oxide layer is formed on the entire surface of the structure. oxide) 14 is grown. Next, polysilicon and tungsten are deposited on the gate oxide film 14 to form a polysilicon layer 16 and a tungsten layer, and then the tungsten layer is heat-treated at a high temperature to form a tungsten silicate layer 18 to form a polyside. To form a structure. Next, an oxide film 20 is formed by depositing oxide on the tungsten silicate layer 18 in a plasma enhanced state by chemical vapor deposition (CVD).

Referring to FIG. 2B, after the photoresist is coated on the oxide layer 20 by a spin coating method, the photoresist is patterned using a mask. Next, the oxide film 20 on the tungsten silicate layer 18 is patterned using the patterned photoresist as an etching mask to form an oxide film pattern 20 'for forming a gate electrode, and then the photoresist is removed.

Referring to FIG. 2C, the tungsten silicate layer 18 and the polysilicon layer 16 are sequentially etched using the oxide film pattern 20 ′ as an etching mask, and as illustrated, the tungsten silicate pattern 18 ′ and poly A polyside structure for a gate electrode is formed, which is a composite pattern structure of the silicon pattern 16 '.

Referring to FIG. 2D, the polymer adsorbed on the sidewall of the tungsten silicate pattern forming the polyside structure for the gate electrode is removed using the oxygen plasma 22. That is, the polymer is oxidized and removed by highly reactive oxygen radicals. In this case, the oxygen plasma treatment may use a tunnel type or a downstream type of asher.

Preferred process conditions for the oxygen plasma treatment use a pressure of 500-5000 millitorr, a radio frequency power of 300-5000 watts (W) and an oxygen flow rate of 100-5000 sccm (standard cubic centimeter). do. By using the radio frequency discharge, plasma can be effectively maintained.

In addition to the oxygen plasma, ozone asher (O3 asher) may be used. Process conditions when using ozone asher are treated at a temperature of 200 to 300 ° C. using a pressure of 500 to 1000 millitorr and an oxygen flow rate of 1000 to 3000 sccm.

In particular, in the case of using an oxygen plasma, the process is relatively simple, which shortens the process time and can be used in a wide range of conditions. In addition, the polysilicon, tungsten silicate pattern and gate oxide film that are already formed there is an advantage that can reduce damage.

Referring to FIG. 2E, the protective oxide film 21 is formed by performing normal wet cleaning and oxidizing the front surface portion including the sidewall portion of the tungsten silicate pattern 18 ′ of the gate electrode at a high temperature of about 850 ° C.

In the method for forming a gate electrode according to the present invention, after forming the polyside structure for the gate electrode, by using an oxygen plasma or an ozone asher, the polymer adsorbed on the sidewall portion of the tungsten silicate pattern of the gate electrode can be effectively removed. have. Thus, the abnormal reaction of tungsten silicate grains caused in the process of oxidizing the front part of the gate electrode to form a protective oxide film can be effectively prevented, thereby improving the performance of the LDD transistor.

Claims (6)

Sequentially forming a polysilicon layer and a tungsten silicate layer on the active region of the semiconductor substrate; Forming an oxide film on the tungsten silicate layer; Patterning the oxide film to correspond to the gate electrode of the semiconductor device to form an oxide pattern for forming the gate electrode; Patterning a lower structure using the oxide layer pattern as an etching mask to form a polyside structure for the gate electrode; Removing the polymer adsorbed on the sidewalls of the tungsten silicate pattern forming the polyside structure for the gate electrode; And Forming a protective oxide film by oxidizing a front surface of the gate electrode. The method of claim 1, wherein the polymer adsorbed on the sidewall of the tungsten silicate pattern is removed by oxygen plasma treatment. The method of claim 2, wherein the oxygen plasma treatment uses a tunnel type or a downstream type of asher. The oxygen plasma processing conditions of claim 2, wherein the oxygen plasma treatment conditions include a pressure of 500 to 5000 millitorr (mt), a radio frequency (RF) power of 300 to 5000 watts, and oxygen of 100 to 5000 sccm (standard cubic centimeter). A method of forming a gate electrode, characterized by using a flow rate. The method of claim 1, wherein the polymer adsorbed on the sidewall of the tungsten silicate pattern is removed by ozone asher treatment. The method of claim 5, wherein the ozone ashing treatment conditions are performed at a temperature of 200 to 300 DEG C using a pressure of 500 to 1000 millitorr and an oxygen flow rate of 1000 to 3000 sccm.