KR20030052663A - method for isolating semiconductor device - Google Patents

Abstract

PURPOSE: An isolation method of a semiconductor device is provided to be capable of preventing the recess generated at the upper edge portion of a trench and roundly forming the upper portion of the trench by thickly forming bird's beak shaped thermal oxide layer using a heat treatment. CONSTITUTION: After sequentially forming a pad oxide layer(202) and a silicon nitride layer(204) on a semiconductor substrate(200), a trench(210) is formed in the resultant structure. After depositing an HDP(High Density Plasma) oxide layer on the resultant structure, an insulating spacer(221) is formed by polishing the HDP oxide layer. A bird's beak shaped thermal oxide layer(211) is formed at the edge portion of the silicon nitride layer by carrying out a heat treatment. A gap-fill oxide layer(224) is formed in the trench.

Description

Method for isolating semiconductor device

The present invention relates to a method for separating a semiconductor device, and more particularly, to a method for separating a semiconductor device capable of forming a device isolation film by applying a shallow trench isolation (STI) process to a separation region of a substrate.

Semiconductor devices formed on silicon wafers include device isolation regions for electrically separating individual circuit patterns. The formation of the device isolation region is an initial step in all manufacturing steps, and depends on the size of the active area and the process margin of the post-process step. As the semiconductor device becomes highly integrated and miniaturized, the size of each individual device is increased. In addition to miniaturization, research on the reduction of device isolation regions is being actively conducted.

In general, the Locos device isolation method widely used in the manufacture of semiconductor devices has the advantage of simple process, but in the case of highly integrated semiconductor devices of 256M DRAM or higher, the width of the device isolation region decreases due to the Bird's Beak. Punch-through and the thickness reduction of device isolation layers are reaching their limits.

Accordingly, a device isolation method using a trench, such as a shallow trench isolation method (STI), has been proposed as a technique suitable for device isolation of highly integrated semiconductor devices.

1A to 1E are process flowcharts showing a method of separating a semiconductor device according to the prior art.

As shown in FIG. 1A, the semiconductor device isolation method according to the related art includes a pad oxide film 102 that acts as a buffer for the entire surface of the semiconductor substrate 100 in which the device region II and the isolation region I are defined. A silicon nitride film 104 that suppresses oxidation is formed in turn.

Subsequently, a photoresist is applied on the silicon nitride film 104, and then exposed and developed to form a photoresist pattern (not shown) exposing the separation region I.

Next, as shown in FIG. 1B, the photoresist pattern is used as an etching mask, and the shallow trench 110 is formed by etching the silicon nitride layer, the pad oxide layer, and the substrate by a predetermined depth. Then, the photoresist pattern is removed.

Thereafter, as illustrated in FIG. 1C, a thermal oxidation process is performed on the silicon substrate 100 having the trench 110 formed thereon to recover the surface defects caused by the trench etching and to round the trench upper edge. To proceed to form a thermal oxide film 111. The dashed portion shows the trench 110.

Subsequently, after the gap fill oxide film 120 is formed to fill the trench including the thermal oxide film 111, the gap fill oxide film is chemical mechanical polishing (CMP) as shown in FIG. 1D. By etching) to planarize the silicon nitride film 104 to be exposed.

Then, as shown in FIG. 1E, the remaining silicon nitride film is removed, and then the resultant is subjected to wet cleaning using chemicals such as hydrofluoric acid as shown in FIG. 1F. In this case, the gap fill oxide film remaining in the trench 110 becomes the device isolation film 120.

However, in the prior art, during the wet cleaning process using a chemical such as hydrofluoric acid, the upper edge portion of the isolation layer is excessively etched and recessed, and the surface is lower than the active region of the device, thereby causing abnormal operation of the device. .

In addition, when a thermal oxidation process is performed in a furnace for trench rounding, oxidation occurs more quickly than an edge part, and thus there is a problem in that it cannot have a satisfactory round shape.

Accordingly, an object of the present invention is to provide a method of separating a semiconductor device having a round shape while solving a recess in an upper edge portion of a trench.

1A to 1F are cross-sectional views illustrating a method of separating a semiconductor device according to the related art.

2A to 2G are cross-sectional views illustrating a method of separating a semiconductor device in accordance with the present invention.

Explanation of symbols for main parts of the drawings

200. Semiconductor substrate 202. Pad oxide film

204. Silicon nitride film 221. Insulation spacer

210.Trench 211. Thermal Oxidation

220, 224. Gap Fill Oxide a. Thermal oxide

The semiconductor device separation method of the present invention for achieving the above object is to provide a semiconductor substrate having a region defined by the separation of the device, and to form a pad oxide film and silicon nitride film to expose the separation region on the substrate and using Forming a trench, forming an insulating spacer on the sidewalls of the trench, and performing a heat treatment inside the trench including the insulating spacer to form a thermal oxide film having a Buzzbee shape at the edge of the silicon nitride film, and a thermal oxide film. And forming a gap fill oxide film filling the inside of the trench.

The insulating spacer is formed by depositing an HDP oxide film on a substrate including a trench, and then polishing the HDP oxide film.

In addition, the heat treatment process is performed under an oxygen atmosphere, characterized in that to maintain a temperature of 1100 ℃.

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

2A to 2G are cross-sectional views illustrating a method of separating a semiconductor device in accordance with the present invention.

In the method of separating a semiconductor device of the present invention, as shown in FIG. 2A, first, a pad oxide film 202 that functions as a buffer by a thermal oxidation process is formed on an entire surface of a semiconductor substrate 200, and then the pad oxide film 202 is formed. The silicon nitride film 204 which is not oxidized by the chemical vapor deposition process is formed in order on (). In the semiconductor substrate 200, an element region IV and an isolation region III are defined.

Subsequently, a photoresist film is coated on the silicon nitride film 204, and the photoresist film is exposed and developed to form a photoresist pattern (not shown) covering the device region IV and exposing the isolation region III.

Next, as illustrated in FIG. 2B, the shallow trench 210 is formed in the isolation region III by dry etching to a predetermined depth of the silicon nitride layer, the pad oxide layer, and the substrate using the photosensitive layer.

Subsequently, a thermal oxidation process is performed on the substrate on which the trench 210 is formed to form a thermal oxide film 211 on side and bottom surfaces of the trench. At this time, the thermal oxidation process is performed in the furnace, and the rounding effect is inferior since the side surface of the trench appears to be oxidized faster than the edge portion.

Next, the first gap fill oxide film 220 is deposited to a thickness of 400 to 600 kPa on the substrate including the thermal oxide film 211, and then, as shown in FIG. 2C, the first gap fill oxide film is spacer-etched. By etching, the insulating spacer 221 is formed on the sidewall of the trench 210 including the thermal oxide film 211. In this case, an HDP (High Density Plasma) oxide film is used as the first gap fill oxide film 220.

After that, as shown in FIG. 2D, the edge of the insulating spacer 221 is oxidized by performing a heat treatment 230 at a temperature of 1100 ° C. on the resultant product in which the insulating spacer is formed. In other words, in the insulating spacer which is a silicon oxide film component in the trench, the closest portion where oxygen and the silicon component can react with each other to oxidize is an edge portion. In addition, the lower part of the silicon nitride layer is rounded to form a bird's beak. At this time, the grown oxide layer is a thermal oxide layer, and since the etching ratio is very low, it is not easy to be removed by subsequent wet chemicals. The etching ratio is lowered during the heat treatment process.

Subsequently, as illustrated in FIG. 2E, the second gap fill oxide film 224 is deposited on the resultant heat treatment process, and then, as illustrated in FIG. 2F, the second gap fill oxide film is flattened by CMP treatment. . In this case, an HDP oxide film is used as the second gap fill oxide film 224.

Then, as shown in Fig. 2G, the silicon nitride film is removed. At this time, since the thermal oxidation film (a) is formed thick in the burrs beak shape by the heat treatment process at both sides of the trench, no recess is generated even if the silicon oxide film component is removed to some extent in the subsequent wet cleaning process. Do not.

In addition, the thermal oxide film, the insulating spacer, and the second gap fill oxide film remaining in the trench become an isolation layer.

Thereafter, the resultant is subjected to a wet cleaning treatment with chemicals such as hydrofluoric acid.

Subsequently, although not shown in the drawing, the polycrystalline silicon layer for gate formation is deposited on the substrate on which the cleaning process is completed, and then the polycrystalline silicon layer is etched by a photolithography process to form a gate.

As described above, in the method of the present invention, since the thermal oxidation film having a buzz beak is formed thickly in the trench on both sides of the trench, even if the silicon oxide film component is removed to some extent in the subsequent wet cleaning process, the recess is formed. It does not occur.

Therefore, it is possible to remove the abnormal operation of the device generated on the shallow trench structure to improve the electrical characteristics.

In addition, this invention can be implemented in various changes within the range which does not deviate from the summary.

Claims (3)

Providing a semiconductor substrate having an isolation region of the device; Forming respective pad oxide films and silicon nitride films exposing the isolation regions on the substrate and forming trenches using the same; Forming insulating spacers on the trench sidewalls; Heat-treating the inside of the trench including the insulating spacers to form a thermal oxide film having a buzz beak shape at an edge portion of the silicon nitride film; And forming a gap fill oxide film filling the trench including the thermal oxide film. The method of claim 1, wherein the insulating spacer is formed by depositing an HDP oxide film on a substrate including the trench, and then polishing the HDP oxide film. The method of claim 1, wherein the heat treatment is performed under an oxygen atmosphere and is maintained at a temperature of 1100 ° C. 3.