KR19980054482A - Method of forming device isolation film in semiconductor device - Google Patents

Abstract

1. TECHNICAL FIELD OF THE INVENTION

Semiconductor device manufacturing method.

2. The technical problem to be solved by the invention

To provide a method of forming a device isolation layer of a semiconductor device to minimize substrate damage caused by the etching gas used as an etchant in the etching process for forming the trench.

3. Summary of Solution to Invention

An elliptical trench in which sidewalls are protected by a polymer is formed by forming a protective film on the semiconductor substrate to prevent damage to the active region in a subsequent process, and etching the protective film and the semiconductor substrate having a predetermined depth by using an isolation mask. And forming an insulating film over the entire structure, and removing the insulating film until the protective film is exposed by an entire etching process using an etching selectivity ratio between the insulating film and the protective film. To provide.

4. Important uses of the invention

It is used in the method of forming a device separator in a semiconductor device manufacturing process.

Description

Method of forming device isolation film in semiconductor device

The present invention relates to a method of forming an isolation film in a semiconductor device.

In general, the device isolation layer electrically and structurally separates the individual elements constituting the integrated device, so that each device can perform its own function without interference from adjacent devices.

Conventionally, the device isolation film as described above is formed by a LOCOS (LOCal Oxidation of Silicon) process or a PBL (Polysilicon Buffered LOCal Oxidation of Silicon (PBL)) process to oxidize a silicon substrate of the device isolation region, or a device isolation region. The silicon substrate was etched to form a trench, and then formed by a trench process of embedding a CVD oxide film.

First, in the case of the PBL process, a pad oxide film, a nitride film, and a polysilicon film are sequentially formed on a silicon substrate, and the polysilicon film and the nitride film are removed until the pad oxide film is exposed using an element isolation mask that overlaps the active region. A field oxide film, which is an insulating film between devices, was formed through a thermal oxidation process.

Subsequently, in the trench process, after the pad oxide film and the nitride film are sequentially formed on the silicon substrate, the trench structure is formed by removing the nitride film, the pad oxide film and the silicon substrate having a predetermined depth by an etching process using an element isolation mask. After depositing an oxide film on the structure, the oxide film was removed by chemical mechanical polishing until the nitride film was exposed to planarize to form a field oxide film as an inter-element insulating film.

However, in the former, the active area is reduced due to the occurrence of a double bird's beak in the device having a design rule of less than 0.30 μm, that is, 256M DRAM and 1 Giga or more, and in the latter, etching for forming trenches During the process, the etching gas used as an etchant remains in the active region, and the substrate is damaged by the remaining etching gas, thereby affecting the threshold voltage of the device in relation to the operation of the transistor.

An object of the present invention is to provide a method for forming a device isolation layer of a semiconductor device for minimizing damage to a substrate by an etching gas used as an etchant during an etching process for forming a trench.

1A to 1C are cross-sectional views of a device isolation film forming process in a semiconductor device according to an embodiment of the present invention.

Explanation of symbols on the main parts of the drawings

10 silicon substrate 20 natural oxide film

20 oxynitride film 40 CVD oxide film

40a: field oxide film 50: photoresist pattern

In order to achieve the above object, the present invention comprises the steps of forming a protective film on the semiconductor substrate to prevent damage to the active region in a subsequent process; Forming a photoresist pattern on the passivation layer, the photoresist pattern overlapping an active region using an isolation mask; Etching the passivation layer and the semiconductor substrate having a predetermined depth by using the photoresist pattern as an etching mask to form an elliptical trench in which sidewalls are protected by a polymer; Removing the photoresist pattern and forming an insulating film on the entire structure; Removing the insulating film until the protective film is exposed by a front surface etching process using an etching selectivity ratio between the insulating film and the protective film; And removing the protective film.

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

1A to 1C are cross-sectional views of a device isolation film forming process of a semiconductor device according to an embodiment of the present invention.

First, FIG. 1A illustrates a photoresist forming an oxynitride layer 30 on a silicon substrate 10 on which a natural oxide layer 20 is already formed, and exposing a device isolation region to be formed in a subsequent process on the oxynitride layer 30. After the pattern 50 is formed, a dry etching process using the photoresist pattern 50 as an etch barrier, and the degree required in the oxynitride film 30, the natural oxide film 20, and the device isolation process The silicon substrate 10 is etched to form a trench structure.

In this case, in the etching process using the photoresist pattern 50 as an etch mask, the polymer 60 generated by reacting with the photoresist pattern 50 and an etching gas used as an etchant in the dry etching process is the trenched silicon substrate. 10, passivation is performed on the natural oxide film 20, the oxynitride film 30, and the sidewalls of the photoresist pattern 50 to form an ellipsoid-shaped trench in which a space decreases as it enters the trenched substrate. .

In addition, the oxynitride layer 30 is formed as a protective layer for preventing the silicon substrate 10 from being damaged during an oxide layer formation and an etch back process for forming a device isolation layer.

Subsequently, FIG. 1B removes the photoresist pattern 50, removes the polymer 60 passivated in the trenched portion through a series of cleaning processes, and then deposits CVD (Chemical Vapor Deposition) on the entire structure. The oxide film 40 is formed to have a thickness enough to fill the trenched silicon substrate 10 by the method, in which the elliptic shape is formed during the DVD film formation process by the DVD method. Due to the trench formation, overhang of the oxide layer may be prevented at the trench inlet (A).

Lastly, FIG. 1C illustrates that when the oxynitride layer 30 is exposed to nitrogen oxide (Nitrogen) in the main etching gas in order to lower the etching selectivity of the oxynitride layer 30 to the oxide layer 40 by the CVD method. After the entire dry etching of the oxide film 40 by the CVD method until the wet etching process using a first BOE / phosphoric acid / a second BOE to remove the oxynitride film 30 and the natural oxide film 20 To form a field oxide film 40a as a device isolation film.

At this time, the second BOE process is performed at a higher temperature than the bath temperature at the time of the first BOE process to remove the peaks of the oxide film in the trench inlet A.

The present invention described above is not limited to the above-described embodiment and the accompanying drawings, and various substitutions, modifications, and changes are possible in the art without departing from the technical spirit of the present invention. It will be evident to those who have knowledge of.

The present invention made as described above can form an elliptic trench during the etching process for forming the trench to prevent an overhang phenomenon that is likely to occur during the field oxide film forming process to be used as an isolation layer for inter-device insulation. Ion implantation and etching process margins can be secured to improve resistance, and the device's latch-up or leaflash characteristics can be improved.

Claims (7)

Forming a protective film on the semiconductor substrate to prevent damage to the active region in a subsequent process; Forming a photoresist pattern on the passivation layer, the photoresist pattern overlapping an active region using an isolation mask; Etching the passivation layer and the semiconductor substrate having a predetermined depth by using the photoresist pattern as an etching mask to form an elliptical trench in which sidewalls are protected by a polymer; Removing the photoresist pattern and forming an insulating film on the entire structure; Removing the insulating film until the protective film is exposed by a front surface etching process using an etching selectivity ratio between the insulating film and the protective film; And And removing the protective film. The method of claim 1, And removing the photoresist pattern, and then performing a series of cleaning processes to remove the polymer. The method of claim 1, The protective film is a device isolation film forming method of a semiconductor device, characterized in that any one of a nitride film and an oxynitride film formed through a natural oxide film in the lower portion. The method of claim 1, And the insulating film is one of an oxide film and a thermal oxide film by a CVD method. The method of claim 1, And a front surface etching process using an etching selectivity between the insulating film and the protective film is performed by adding at least nitrogen gas to lower the etching selectivity of the protective film with respect to the insulating film. The method according to claim 1 or 3, And removing the protective film by wet etching using a first BOE / phosphate / second BOE. The method of claim 6, And the second BOE process is performed at a higher temperature than the first BOE process during the first BOE / phosphate / second BOE process for removing the protective film.