KR20000065392A - Method for fabricating isolation region of semiconductor device - Google Patents

Abstract

PURPOSE: A method for manufacturing an isolation layer of a semiconductor device is provided to reduce a junction leakage by minimizing the damage caused by an etching process to a semiconductor substrate. CONSTITUTION: First and second pad insulating layers are sequentially formed to expose a predetermined region of a semiconductor substrate(21). A first trench is formed on the semiconductor substrate by using the second pad insulating layer as a mask. A first buffer insulating layer is formed on the surface of the first trench. The first buffer insulating layer is formed on the bottom surface of the first trench by using the second pad insulating layer as a mask. A second trench is formed on the semiconductor substrate by using the second pad insulating layer and first buffer insulating layer as a mask. A second buffer insulating layer is formed on the surface of the second trench. An isolation layer is formed within the first and second trenches. An impurity region is formed in the semiconductor substrate on both sides of the isolation layer.

Description

METHODS FOR FABRICATING ISOLATION REGION OF SEMICONDUCTOR DEVICE}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device, and more particularly, to a method of forming an isolation layer of a semiconductor device for effectively lowering a junction leakage property in a portion where a source / drain region and a semiconductor substrate contact each other.

As semiconductors are highly integrated, transistor sizes and the space between active and active decrease, the method of applying a shallow trench isolation (STI) process is used in the isolation layer formation method through the LOCOS process.

Hereinafter, a method of forming the separator using the STI process will be described.

Referring to the accompanying drawings, a method of forming a separator of a conventional semiconductor device is as follows.

1A to 1G are cross-sectional views illustrating a method of forming a separator of a conventional semiconductor device.

In the conventional method of forming an isolation layer of a semiconductor device, as shown in FIG. 1A, a first oxide film and a nitride film are sequentially deposited on a semiconductor substrate 1 in which an active region and a field region are defined, and then a photoresist film is formed on a nitride film, although not shown in the drawing. After applying and selectively patterning the photoresist film so that the field region is exposed, the nitride film and the first oxide film are etched in turn using the patterned photoresist mask as a mask. Subsequently, when the photoresist film is removed, the pad oxide film 2 and the pad nitride film 3 are formed.

Next, as shown in FIG. 1B, the trench 4 is formed by etching the semiconductor substrate 1 with a predetermined depth using the pad nitride film 3 as a mask. The trench 4 is deeper than the source / drain regions to be formed later.

Although not shown in the drawing as shown in FIG. 1C, etching damage occurs on the surface of the semiconductor substrate 1 when the semiconductor substrate 1 is etched to form the trench 4. At this time, the etching damage is the most severe upper corner portion of the trench (4). In order to remove this etching damage, a thermal oxidation process is performed after the annealing process. Accordingly, the sacrificial oxide film 5 is formed on the surface of the trench 4.

Next, as shown in FIG. 1D, after the sacrificial oxide film 5 is removed, a buffer oxide film 6 is formed on the surface of the trench 4 by a thermal oxidation process in order to round the upper corner portion of the trench 4. .

As shown in FIG. 1E, the second oxide film 7 is deposited on the entire surface including the trench 4.

As shown in FIG. 1F, the second oxide film 7 is etched by chemical mechanical polishing to expose the pad nitride film 3. Thereafter, after the pad nitride film 3 is removed, the second oxide film 7 and the pad oxide film 2 are etched again by chemical mechanical polishing to form the isolation oxide film 7a in the trench 4.

Next, although not shown, a gate oxide film and a gate electrode are formed in a predetermined region on the active region.

Thereafter, as shown in FIG. 1G, the source / drain regions 8 are formed in the semiconductor substrate 1 using the gate electrode as a mask. At this time, the source / drain region 8 is in contact with one side of the buffer oxide film 6 on both sides of the isolation oxide film 7a.

The conventional method of forming a separator of a semiconductor device as described above has the following problems.

The source / drain region, that is, the point where the junction end and the semiconductor substrate meet, the etching damage of the semiconductor substrate is relatively large when the trench is etched, so that the junction leakage is likely to occur, thereby reducing the reliability of the device.

Disclosure of Invention The present invention has been made to solve the above problems, and an object of the present invention is to provide a method for forming an isolation layer of a semiconductor device suitable for effectively lowering the junction liquidity characteristics by minimizing the etch damage of the semiconductor substrate of the junction forming portion. .

1A to 1G are cross-sectional views illustrating a method of forming a separator of a conventional semiconductor device.

2A to 2G are cross-sectional views illustrating a method of forming an isolation layer of a semiconductor device according to the present invention.

Explanation of symbols for the main parts of the drawings

21 semiconductor substrate 22 pad oxide film

23: pad nitride film 24: first trench

25: first oxide film 26: second trench

27: second oxide film 28: third oxide film

28a: isolation oxide layer 29: source / drain region

In order to achieve the above object, the method of forming an isolation layer of a semiconductor device according to the present invention comprises the steps of sequentially forming a first and a second pad insulation layer so that one region of the semiconductor substrate is exposed, and using the second pad insulation layer as a mask on the semiconductor substrate. Forming a first trench, forming a first buffer insulating film on a surface of the first trench, removing a first buffer insulating film on a lower surface of the first trench using the second pad insulating film as a mask, and the second pad Forming a second trench in the semiconductor substrate using the insulating film and the first buffer insulating film as a mask, forming a second buffer insulating film on the surface of the second trench, and forming an insulating insulating film in the first and second trenches. And forming impurity regions in both semiconductor substrates of the insulating insulating film.

Referring to the accompanying drawings, a method of forming an isolation film of a semiconductor device of the present invention will be described.

2A to 2G are cross-sectional views illustrating a method of forming an isolation film of a semiconductor device of the present invention.

In the method of forming an isolation film of the semiconductor device of the present invention, as shown in FIG. 2A, an oxide film and a nitride film are sequentially deposited on a semiconductor substrate 21 in which an active region and a field region are defined, and then a photoresist film is formed on the nitride film, although not shown in the drawing. After coating and selectively patterning the photoresist film so that the field region is exposed, the nitride film and the oxide film are sequentially etched using the patterned photoresist mask as a mask. Subsequently, when the photoresist film is removed, the pad oxide film 22 and the pad nitride film 23 are formed.

Next, as shown in FIG. 2B, the semiconductor substrate 21 is etched with a predetermined depth using the pad oxide film 22 and the pad nitride film 23 as a mask to form the first trench 24. In this case, the first trench 24 is a shallow trench and etched only to a depth to form a source / drain region later. At this time, source / drain regions to be formed later are indicated by dotted lines (FIGS. 2B, 2C, 2D, 2E, and 2F).

As shown in FIG. 2C, the surface of the first trench 24 is annealed to the surface of the second trench 24 in order to remove the etch damage generated in the semiconductor substrate 21 when the first trench 24 is formed. A first oxide film 25 serving as a buffer is formed.

Next, as shown in FIG. 2D, the first oxide film 25 formed on the lower surface of the first trench 24 is removed using the pad nitride film 23 as a mask, and then the pad oxide film 22 and the pad nitride film ( The second trench 26 is formed by further etching the semiconductor substrate 21 by using the 23 and the first oxide film 25 as a mask.

As shown in FIG. 2E, a second oxide layer 27 serving as a buffer is formed on the surface of the second trench 26 by a thermal oxidation process. In the process of forming the second buffer oxide layer 27, the upper corner portion of the first trench 24 is rounded.

Next, as shown in FIG. 2F, a third oxide film 28 is deposited on the entire surface including the first and second trenches 24 and 26.

As shown in FIG. 2G, the third oxide film 28 is flatly etched by chemical mechanical polishing so that the surface of the pad nitride film 23 is exposed, and the pad nitride film 23 is removed. Thereafter, the third oxide film 28 and the pad oxide film 22 are etched again by chemical mechanical polishing to form the isolation oxide film 28a so as to evenly fill the first and second trenches 24 and 26.

Next, although not shown, a gate oxide film and a gate electrode are formed in a predetermined region on the active region. Thereafter, the source / drain regions 29 are formed in the semiconductor substrate 21 using the gate electrodes as masks. At this time, the source / drain region 29 is in contact with one side of the first oxide film 25 on both sides of the isolation oxide film 28a.

The isolation film forming method of the semiconductor device of the present invention as described above has the following effects.

When the trench is formed twice and the second trench is formed using the oxide film formed on the surface of the first trench as a buffer, the trench trench damage can be performed on the semiconductor substrate without excessive additional etching damage. It is possible to effectively control junction leakage caused by

Claims (6)

Sequentially forming the first and second pad insulating films so that one region of the semiconductor substrate is exposed; Forming a first trench in the semiconductor substrate using the second pad insulating layer as a mask; Forming a first buffer insulating film on the surface of the first trench, Removing the first buffer insulating film under the first trench using the second pad insulating film as a mask; Forming a second trench in the semiconductor substrate using the second pad insulating film and the first buffer insulating film as a mask; Forming a second buffer insulating film on the surface of the second trench, Forming an isolation insulating film in the first and second trenches, Forming an impurity region in both semiconductor substrates of the isolation insulating film. The method of claim 1, wherein the first and second buffer insulating layers are formed by a thermal oxidation process. The method of claim 1, wherein the first trench is formed only to a depth of the impurity region to be formed later. The method of claim 1, wherein an upper corner of the first trench is rounded during the process of forming the second buffer insulating layer. The method of claim 1, wherein the first pad insulating layer is formed of an oxide film. 2. The method of claim 1, wherein the second pad insulating film is formed of a nitride film.