KR20000050641A - Method for etching nitride having high etch selectivity with oxide - Google Patents

Abstract

PURPOSE: A method for etching a nitride layer is provided to prevent a semiconductor substrate from being damaged, by having a high etching selection ratio regarding an oxidation layer. CONSTITUTION: A method for etching a nitride layer having a high etching selection ratio regarding an oxidation layer comprises the steps of: forming an oxidation layer along the surface of the structure formed on a semiconductor substrate; forming a nitride layer on the oxidation layer; and forming a spacer on both sidewalls of the structure by etching the nitride layer, in which the etching process is carried out by etching gas including HBr/Cl2 gas or SF6/He gas in poly-etching facilities having a condition of low pressure and high power.

Description

Nitride Etching Method with High Etch Selectivity to Oxides

The present invention relates to an etching method of a semiconductor device, and more particularly to a nitride film etching method having a high etching selectivity with respect to the oxide film.

In general, a process of forming spacers on both sidewalls of the gate polysilicon film has been applied to form a lightly doped drain (LDD) structure. When the gate electrode is formed of a polyside structure using a metal film such as Co and Ti, spacers are formed on both sidewalls of the gate polysilicon film using an oxide film, and then the top of the gate polysilicon film is formed using a Silicidation Blocking Layer (SBL). One of the Co silicide film and the Ti silicide film is simultaneously formed on the semiconductor substrate. However, at this time, the silicide film may be slightly formed on the sidewalls of the oxide spacer as well as on the gate polysilicon film and the semiconductor substrate. This may cause a short circuit between the gate electrode and the source / drain.

In order to prevent this, a nitride film having a strong silicidation blocking property, such as a Si ₃ N ₄ film, is used instead of the oxide film as a spacer film of the gate electrode to prevent the formation of the silicide film to prevent a short circuit between the gate electrode and the source / drain. It is preventing.

Next, the conventional gate electrode formation method which has the said gate spacer is described.

1A and 1B are flow charts sequentially illustrating conventional gate electrode formation processes with gate spacers.

Referring to FIG. 1A, a conventional method of forming a gate electrode includes a gate oxide film 12a, a gate conductive film 12b, and a gate oxide film 12a on a semiconductor substrate 10 in which an active region and an inactive region (not shown) are defined. The gate mask 12c is formed in turn. The gate electrodes 12 are formed by sequentially etching the gate mask 102c, the gate conductive layer 12b, and the gate oxide layer 12a using a gate electrode forming mask. Subsequently, a gate poly oxide film (GPox) 14, a buffer film 16, and a spacer nitride film 18 are sequentially formed along the surfaces of the structures formed on the semiconductor substrate 10. The buffer film 16 is formed of, for example, an oxide film. Subsequently, by etching the nitride film 18 by an etch back process, gate spacers 18a are formed on both sidewalls of the gate electrodes 12, as shown in FIG. 1B.

Here, the buffer film 16 is a film that serves to prevent damage to the substrate by selectively etching only the nitride film 18 when the nitride film 18 is etched. However, the etching process is performed with etching gases including CF ₄ gas and CHF ₄ gas in an oxide etching apparatus having high pressure and low power processing conditions. The etching selectivity between the nitride film 18 and the oxide buffer film 16 during the etching process under the conditions is not so large that the buffer film 16 and the gate polyoxide film 14 during the etch back process are shown in the drawings. Likewise, the semiconductor substrate 10 may be exposed by being etched together, which may damage the substrate. This causes a problem that a leakage current is generated at the damaged portion of the source / drain region after the formation of the subsequent silicide film.

The present invention has been proposed to solve the above-mentioned problems, and has a high etch selectivity with respect to an oxide film that can prevent damage to a semiconductor substrate by having an etch selectivity with respect to an oxide film during an etching process of a nitride film for forming a gate spacer. The purpose is to provide a nitride film etching method having a.

1A and 1B are flow charts sequentially illustrating conventional gate electrode formation processes with gate spacers; And

2A and 2B are flowcharts sequentially illustrating gate electrode forming processes to which a nitride film etching method having a high etching selectivity with respect to an oxide film according to an embodiment of the present invention is applied.

* Explanation of symbols for the main parts of the drawings

10, 100: semiconductor substrate 12, 102: gate electrode

14, 104: gate polyoxide 16, 106: buffer film

18a, 108a: Gate spacer

According to the present invention for achieving the above object, a nitride film etching method having a high etching selectivity with respect to the oxide film, forming an oxide film along the surface of the structure formed on the semiconductor substrate; Forming a nitride film on the oxide film; Forming a spacer on both sidewalls of the structure by etching the nitride layer, wherein the etching process includes HBr / Cl ₂ gases or SF ₆ / He gas in a poly etching facility provided with low pressure and high power process conditions. Is performed with etching gases containing the same.

Referring to FIG. 2B, in the nitride film etching method having a high etching selectivity with respect to the novel oxide film according to the embodiment of the present invention, an oxide film is formed along the surface of the structure formed on the semiconductor substrate, and the nitride film is formed on the oxide film. Is formed. Subsequently, spacers are formed on both sidewalls of the structure by etching the nitride film. In this case, the etching process may be performed with etching gases including HBr / Cl ₂ gases or SF ₆ / He gases in a poly etching facility provided with low pressure and high power process conditions. Thus by such nitride etching with a high etching selectivity to the oxide film, the etching process of the nitride film for forming a spacer on both side walls of the gate electrode on the poly etch equipment given the process conditions of low pressure and high power HBr / Cl ₂ By performing the etching gases including the gases or SF ₆ / He gases, the nitride film can be etched to have a high selectivity with respect to the oxide film, which is a lower film, thereby preventing damage to the semiconductor substrate. Therefore, it is possible to prevent a short circuit between the source / drain and the gate in forming the subsequent silicide film.

(Example)

Hereinafter, embodiments of the present invention will be described in detail with reference to FIGS. 2A and 2B.

2A and 2B are flowcharts sequentially illustrating gate electrode forming processes to which a nitride film etching method having a high etching selectivity with respect to an oxide film according to an embodiment of the present invention is applied.

Referring to FIG. 2A, in the gate electrode forming method according to the present invention, a gate oxide film 102a and a gate conductive film 102b are first formed on a semiconductor substrate 100 in which an active region and an inactive region (not shown) are defined. And the gate mask 102c are formed in this order. Here, the gate conductive film 102b has a multilayer structure in which a polysilicon film and a silicide film are stacked, for example. Subsequently, the gate mask 102c, the gate conductive layer 102b, and the gate oxide layer 102a are sequentially etched using the gate electrode forming mask until the surface of the semiconductor substrate 100 is exposed. 102 are formed. Low concentration impurity ions are implanted into the semiconductor substrate 100 on both sides of the gate electrodes 102 (not shown).

Next, a gate poly oxide film 104, a buffer film 106, and a nitride film 108 for forming a spacer are sequentially formed along the surfaces of the gate electrodes formed on the semiconductor substrate 100. The gate poly oxide film 104 and the buffer film 106 are each formed to have a thickness of about 100 GPa, and the nitride film 108 is formed within a thickness range of about 1000 GPa to 2000 GPa. The method of forming the gate electrode having the spacers on both side walls as described above is not significantly different from the conventional art, and has been described for better understanding of the present invention.

Subsequently, by dry etching the nitride film 108 by an etch back process, as shown in FIG. 2B, gate spacers 108a are formed on both sidewalls of the gate electrodes 102. In the present invention, the etching process of the nitride film 108 for forming the gate spacer 108a has a high selectivity with respect to the buffer film 106. HBr / Cl ₂ gases in a poly etching facility having an optimal process condition Or etching gases containing SF ₆ / He gases. The application of these etching facilities and process conditions is a novel and most important aspect of the present invention.

Specifically, the etching process for forming the gate spacer 108a is performed by LRA's "RAINBOW POLY ETCHER" facility, and the process conditions are as follows. Pressures in the range 100 mT to 500 mT, power in the range 100 W to 400 W, HBr gas in the range 100 sccm to 200 sccm, etching gases including Cl ₂ gas in the range 100 sccm to 200 sccm or pressures in the same range and power to 100 sccm to 200 sccm at the same range Etch gases comprising SF ₆ gas in the range, He gas in the range of 100 sccm to 200 sccm. When the etching process is performed under such process facilities and process conditions, the nitride film to the oxide film has an etching selectivity of 2: 1 to 100: 1 or more, so that the nitride film is etched to have a high selectivity with respect to the oxide film.

When the process conditions are actually applied, the selectivity ratio of the nitride film 108 and the oxide buffer film 106 is 200 sccm of Cl ₂ gas at a pressure of 250 mT, a power of 400 W, and a process gap of 0.8 cm. , The etching rate of the nitride film 108 is 476 Å / min, and the etch rate of the buffer film 106, which is an oxide film, is 23 때 / min when etched with 100 sccm HBr gas and 7 Torr backside He gas. Etch selectivity is 20: 1.

For other process conditions, 200 sccm Cl ₂ gas, 200 sccm HBr gas, 7 Torr back-side He gas at 250 mT pressure, 300 W power, 0.8 cm process gap process conditions. When etching, the etch rate of the nitride film 108 is 794 Å / min, the etch rate of the buffer film 106 is 6 Å / min, and the etching selectivity is 132: 1.

For other process conditions, etched with 90 sccm SF ₆ gas, 180 sccm He gas, and 10 Torr backside He gas at 500 mT pressure, 325 W power, 0.8 cm process gap. The etch rate of the nitride film 108 is 4452 4 / min, the etch rate of the buffer film 106 is 34 Å / min, and the etching selectivity is 131: 1.

As can be seen from the above results obtained by applying to the actual process, it is possible to obtain a much higher selection ratio than when the oxide etching gas is mainly used in the conventional nitride etching process, and it is very easy to control the etching selectivity according to the process conditions. Able to know. Therefore, the use range of the technique which can etch the nitride film 108 to have a high selectivity with respect to the buffer film 106 which is an oxide film became wide.

In order to obtain uniform etching characteristics during the etching of the nitride film 108 under the process conditions, the process gap of the rainbow equipment is set to 1 cm or less as possible, and the process condition is increased to increase the etching rate of the nitride film 108. Low pressure (about 100mTorr) and high power (about 400W) were used to improve the physical etching characteristics. The back side He gas is supplied because the temperature of the wafer surface is increased during the etching process of the nitride layer 108. This may cause a defect in the process. Therefore, the wafer surface is heated by supplying the He gas. This is to prevent excessive rise. In this case, when a higher etching selectivity is required, the etching process may be performed by setting the pressure of the back side He gas to a high pressure of 10 Torr or more.

As a result, in the present invention, as shown in FIG. 2B, the nitride film 108 is etched to have a high etching selectivity with respect to the buffer film 106 which is an oxide film under the etching facilities and process conditions. The buffer layer 106 on the gate electrodes 102 is left as it is, thereby preventing damage to the semiconductor substrate 100.

During the etching process of the nitride layer 108, an overetch process is performed to completely remove the nitride layer 108 on the buffer layer 106. As a result, as shown in the drawing, the gate spacers 108a are formed on both sides of the gate electrodes 102. Is formed slightly below the buffer film 106. Next, an LDD structure is formed by implanting high concentration impurity ions into the semiconductor substrate 100 on both sides of the gate spacer 108a (not shown). During the impurity ion implantation, the process may be performed using the buffer layer 106 as an ion implantation mask. Thereafter, the buffer layer 106 and the gate polyoxide layer 104 on the semiconductor substrate 100 and the gate electrodes 102 are removed by a wet etching process, and then a subsequent process is performed in a general manner.

The etching process of the nitride film having a high selectivity with respect to the oxide film of the present invention as described above can be applied not only to the gate spacer forming process but also to all processes requiring a high selectivity between the two films.

Although the present invention has been described with reference to preferred embodiments, it will be apparent to those skilled in the art that various modifications may be made without departing from the spirit and scope of the invention.

According to the present invention, the etching process of the nitride film for spacer formation on both sidewalls of the gate electrode is performed by etching gases including HBr / Cl ₂ gases or SF ₆ / He gases in a poly etching apparatus in which low pressure and high power process conditions are given. By performing the process, the nitride film can be etched to have a high selectivity with respect to the oxide film as the lower film, thereby preventing damage to the semiconductor substrate. Therefore, there is an effect that a short circuit between the source / drain and the gate can be prevented when the subsequent silicide film is formed.

Claims (3)

Forming an oxide film along the surface of the structure formed on the semiconductor substrate; Forming a nitride film on the oxide film; Forming a spacer on both sidewalls of the structure by etching the nitride layer, wherein the etching process includes HBr / Cl ₂ gases or SF ₆ / He gas in a poly etching facility provided with low pressure and high power process conditions. A nitride film etching method having a high etching selectivity with respect to the oxide film is performed with the etching gases including. The method of claim 1, The etching equipment is LRC's RAINBOW poly etching equipment, the processing gap of the equipment is 1 cm or less, the pressure conditions are given in the range of 100mT to 500mT, and the power conditions range from 100W to 400W. A nitride film etching method having a high etching selectivity with respect to an oxide film given therein. The method of claim 1, The etching gases HBr gas, Cl ₂ gas, SF ₆ gas, and He gas each have a high etching selectivity with respect to the oxide film used in the range of 100sccm to 200sccm.