KR20070000062A - Method of filling a opening and method of forming a trench isolation structure using the same - Google Patents

Abstract

A method of filling an opening and a method of forming a trench isolation structure using the same are provided to increase density of a filler of the opening by using an expansible member formed on an inner surface of the opening. An opening(104) is formed by etching partially a substrate(100). An expansible member(106b) is formed on a sidewall of the opening. The expansible member is filled with a plurality of fillers(108a,108b). The volume of the expansible member is enlarged to increase the density of the fillers formed within the opening. The expansible member is formed with polysilicon. The volume of the expansible member is enlarged by performing a thermal oxidation process.

Description

Method of filling a opening and method of forming a trench isolation structure using the same}

The present invention relates to an opening filling method and a method of forming a device isolation structure using the same. More particularly, the present invention relates to a method of filling a space or opening between patterns such as metal wiring in the manufacture of a semiconductor device, or a method of forming an element isolation film formed in an opening to define an element isolation region.

Substrates such as silicon wafers in which semiconductor devices are formed by electrical patterns are largely divided into an active region in which semiconductor elements are formed and an isolation region for providing electrical insulation between the active regions. The device isolation region may be formed by forming an trench and then filling an insulator in the trench. In addition, the empty space formed between the electrical patterns is filled with an insulator for electrically insulating the patterns.

In recent years, as semiconductor devices become highly integrated, the line widths of the electrical patterns, the widths of the spaces between the patterns, and the line widths of the device isolation layers are rapidly decreasing. Accordingly, the technique of densely filling the insulator without voids in the spaces between the patterns has emerged as an indispensable technique for securing the reliability of the semiconductor device. In addition, the device isolation layer may have a seam or void. There is a need for a technique for forming compactly so that does not occur. In view of this, the technique of filling a void or opening having a fine line width has a similar purpose.

Device isolation techniques for forming the device isolation region include a local oxidation of silicon (LOCOS) and a shallow trench isolation method. The LOCOS device separation is excellent in device separation effect, there is an advantage that can be formed through a simple process. However, the LOCOS device isolation requires a relatively larger area than the trench device isolation, and the active area is narrowed due to a phenomenon called bird's beak.

Therefore, in recent years, trench element isolation methods having good device isolation characteristics even in a small area have been mainly used. In the trench isolation process, a trench is formed by etching a substrate in an isolation region using a silicon nitride film as a mask pattern. Subsequently, a filling material such as an oxide film is filled in the opening, and then a chemical mechanical polishing process is performed to form an isolation layer.

However, as the aspect ratio of the opening for forming the device isolation film increases, it is difficult to fill the insulating film without voids in the deep and narrow openings. In particular, a high density plasma (HDP) oxide film is used in an opening having a line width of 90 nm or less, and there is a problem in that device characteristics are degraded due to voids or leakage current caused by a seam.

Accordingly, the generation of voids or seams can be prevented by using an oxide film having a flowable property such as boron doped phosphosilicate glass (BPSG) or spin on glass (SOG) material at a line width of 90 nm or less. However, the flowable oxide film has a very low density compared to the HDP oxide film. That is, since the film quality of the oxide film is not dense, there is a problem that the oxide film is excessively etched beyond a predetermined target thickness when exposed to a wet cleaning process, a wet etching process, or the like. Thereby, there exists a problem that the characteristic of an element falls and the reliability of a semiconductor device falls.

Accordingly, it is a first object of the present invention to provide an opening filling method capable of densifying the film quality of a filling.

It is a second object of the present invention to provide a method for forming a trench isolation structure using the opening filling method.

In the opening filling method according to an aspect of the present invention for achieving the first object, first, the substrate is partially etched to form an opening. An expandable member is formed on the sidewall of the opening. A filling is formed on the inflatable member to sufficiently fill the opening. The volume of the inflatable member is increased to increase the density of the filler present inside the opening.

A method of forming a trench isolation structure according to another aspect of the present invention for achieving the second object, first forms an opening for defining the isolation region in the substrate. A polysilicon film having a first thickness is formed on the inner surface of the opening. An insulating film is formed on the polysilicon film to sufficiently fill the opening. In order to increase the packing density of the insulating film by increasing the volume of the polysilicon film, the polysilicon film is converted into a polysilicon oxide film having a second thickness thicker than the first thickness.

According to one embodiment of the invention, the opening has a line width of 30 to 90nm, the insulating film may be made of SOG composition formed by the SOG process or BPSG oxide formed by the chemical vapor deposition process.

According to the opening filling method, since the polysilicon film expands while being converted into an oxide film, the insulating film filling the opening can be densified by the oxide film. Accordingly, when voids are present in the insulating film, the polysilicon film may expand and the voids may be removed by the insulating film.

Hereinafter, an opening filling method and a method of forming a trench device isolation structure using the same according to preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings, but the present invention is not limited to the following embodiments. Those skilled in the art may implement the present invention in various other forms without departing from the technical spirit of the present invention. In the accompanying drawings, the dimensions of the substrates, layers (films), regions, pads, patterns or structures are shown to be larger than actual for clarity of the invention. In the present invention, each layer (film), region, pad, pattern or structures is formed to be "on", "top" or "bottom" of the substrate, each layer (film), region, pad or patterns. When mentioned, it means that each layer (film), region, pad, pattern or structure is formed directly on or below or below the substrate, each layer (film), region, pad or patterns, or Other layers (films), other regions, different pads, different patterns or other structures may additionally be formed on the substrate. Further, where each layer (film), region, pad, pattern or structure is referred to as "first" and / or "second", it is not intended to limit these members but merely each layer (film), region, pad , To distinguish between patterns or structures. Thus, the "first" and / or "second" may be used selectively or interchangeably for each layer (film), region, pad, pattern or structure, respectively.

1 to 3 are cross-sectional views for explaining the opening filling method according to the present invention.

Referring to FIG. 1, a mask pattern 102 for forming an opening 104 in a semiconductor substrate 100 such as a silicon wafer is formed. The mask pattern 102 may be formed of a photoresist composition or a hard mask material such as silicon nitride (SixNy) or boron nitride (BN).

An opening 104 is formed below the surface of the substrate 100 by partially etching the substrate 100 using the mask pattern 102 as an etching mask. For example, the opening 104 may be formed in various forms such as an inclined sidewall shape having an upper portion having a wider width than a lower portion, or an upper side having a narrower width than a lower portion, and having a bowed shape. . The opening 104 may be formed in various forms by changing etching conditions such as an etching gas, a carrier gas, an etching time, an etching solution, or a pressure of the etching process.

Alternatively, the opening 104 may have a shape extending in the longitudinal direction substantially perpendicular to the width direction. Specifically, patterns such as transistors (not shown) and metal wires (not shown) are formed on the substrate 100. Accordingly, an opening 104, that is, an empty space may be formed between the patterns.

In the present embodiment, an example of the opening 104 formed below the surface of the substrate 100 in order to provide a space in which the device isolation layer is formed is described.

Referring to FIG. 2, a first expandable member 106a having a first thickness is formed on an inner side surface of the opening 104. The first expandable member 106a is then provided to expand the volume under predetermined conditions and to increase the packing density of the material filled in the opening 104 using the pressure caused by the expansion. Therefore, it is preferable that the first expandable member 106a is continuously formed on the sidewall and the bottom surface of the opening 104.

The first expandable member 106a may vary depending on the use of the opening 104. For example, when a device isolation layer is to be formed by filling an insulating layer in the opening 104, poly-Si may be used as the first expandable member 106a. When the polysilicon is oxidized, it is converted into silicon oxide (SiO ₂ ), wherein the converted silicon oxide has a volume larger than that of the initial polysilicon. That is, the polysilicon is converted into silicon oxide having excellent insulation capability by oxidation, and is suitable as the first expandable member 106a because its volume expands.

In addition, when the first expandable member 106a is made of a polysilicon film, the polysilicon film may be formed by a chemical vapor deposition method having excellent step coverage.

A first filling 108a having a first density filling the opening 104 is formed on the first expandable member 106a. When the device isolation layer is formed in the opening 104, the first charge 108a may be formed of an insulating layer. Examples of the insulating film include silicate series such as high density plasma (HDP) oxide film, undoped silicate glass (USG), boron doped silicate glass (BSG), phosphorous doped silicate glass (PSG), and boron doped phosphosilicate glass (BPSG). And an SOG composition containing an oxide film or silazane, silanol, silsesquioxane, or the like.

In particular, when the line width of the opening 104 is 50 to 90nm, the first filler 108a is preferably formed of a flowable BPSG or SOG composition. As a result, an insulating film having a first density exists in the opening 104.

Referring to FIG. 3, the second expandable member 106b having a second thickness larger than the first thickness is formed by increasing the volume of the first expandable member 106a. For example, when the first expandable member 106a is made of polysilicon and the first filler 108a is made of an oxide or SOG composition, the second expandable member 106b is oxidized in the polysilicon. Silicon oxide.

The second expandable member 106b is formed by heat treating the substrate 100 in an oxygen (O) atmosphere. The heat treatment is preferably performed so that the entire polysilicon film is converted to silicon oxide in order to improve the insulating ability of the opening 104.

Here, the volume of the polysilicon film is increased as it is converted to silicon oxide. Specifically, the polysilicon film having an initial first thickness is converted into a silicon oxide film having a second thickness about twice as large as the first thickness by an oxidation process.

Meanwhile, the first filling material 108a having the first density and existing inside the opening 104 has the second expandable member as the first expandable member 106a is converted into the second expandable member 106b. By the expansion pressure of 106b, a second charge 108b having a second density larger than the first density is formed. In other words, the film quality of the second filler 108b may be denser than that of the first filler 108a.

For example, since the polysilicon film is expanded to a silicon oxide film and the volume expands, the insulating film inside the opening 104 is compressed by the expansion pressure. Therefore, the insulating film inside the opening 104 may have a second density greater than the first density. Here, when a void exists in the opening 104, the void may be removed by compression of the insulating layer.

According to the opening filling method as described above, since the packing density of the first filling 108a is increased and the film quality becomes dense, generation of voids therein can be suppressed. When the device isolation layer is formed in the opening 104, since the film quality of the device isolation layer becomes dense, voids and the like may be suppressed, thereby improving insulation ability. In addition, the etching resistance by the subsequent cleaning or etching process may be increased.

4 to 9 are cross-sectional views illustrating a method of forming a trench isolation structure using the opening filling method.

Referring to FIG. 4, a buffer oxide film 202 is formed on a substrate 200 such as a silicon wafer. The buffer oxide layer 202 may include silicon oxide, and may be formed by oxidizing a surface portion of the silicon substrate 200 through a thermal oxidation process.

A hard mask 204 is formed on the buffer oxide layer 202 to open the device isolation region of the substrate 200. The hard mask 204 may be formed of a nitride such as silicon nitride. Here, the buffer oxide film 202 is a film provided to relieve stress that may occur at the interface between the nitride constituting the hard mask 204 and the silicon substrate 200.

The trench 206 is formed by etching the exposed substrate 200 using the hard mask 204 as an etching mask. The trench 206 may be formed by an anisotropic dry etching process. The trench 206 has a line width of about 50 to 90 nm, and the sidewall of the trench 206 has an inclination of about 80 to 90 degrees with respect to the surface of the substrate 200 at an inlet of the trench 206. .

A nitride film liner 208 is formed on the sidewalls and bottom of the trench 206. The nitride film liner 208 functions as a barrier film that prevents oxidation of the inner surface of the trench 206. Specifically, the trench 206 may be prevented from degrading device characteristics by growing at a dislocation through a subsequent heat treatment process such as a point defect or the like on the sidewall of the trench 206 generated by an etching process. . Prior to forming the nitride film liner 208, it is preferable to further form a thermal oxide film (not shown) to mitigate etching damage occurring when the trench 206 is formed.

A polysilicon film 210a having a first thickness is formed on the nitride film liner 208 and the substrate 200. The polysilicon film 210a may be formed to have a substantially uniform thickness of 30 to 200 kPa through a chemical vapor deposition process.

A first insulating layer 212a having a first density is formed on the polysilicon layer 210a. In this case, the first insulating layer 212a is formed to sufficiently fill the trench 206. For example, the first insulating layer 212a may be formed of a high density plasma (HDP) oxide layer, a BPSG oxide layer, or an SOG oxide layer. In this case, since the line width of the trench 206 is very small (90 nm or less), the first insulating film 212a is preferably made of a flowable film. More preferably, the flowable film is formed of an SOG composition. The SOG composition is a liquid silicon oxide organic precursor, which is formed on the substrate 200 and flows into the trench 206 similarly to a method of applying a photoresist composition. At this time, since the SOG composition is substantially liquid, the top surface of the SOG film is formed to be substantially flat before the solvent contained in the SOG composition evaporates.

Referring to FIG. 6, the substrate 200 is heat-treated under oxygen (O) to oxidize the polysilicon film 210a. For example, the heat treatment may be performed at a temperature of about 700 to 1000 ℃ oxygen. Examples of the heat treatment process include nitrogen (N ₂ ) annealing, argon (Ar) annealing, steam (H ₂ O) annealing, oxygen (O ₂ ) annealing, vacuum annealing, and the like.

By the heat treatment process, the polysilicon film 210a is oxidized and converted into a polysilicon oxide film 210b (SiO ₂ , 210b). The heat treatment process may be performed to substantially convert the entire polysilicon film 210a into silicon oxide in order to improve the insulating ability of the trench 206.

In this case, the polysilicon film 210a is converted to silicon oxide, so that its volume increases. Specifically, the polysilicon film 210a having the first first thickness is converted to a silicon oxide film having a second thickness that is approximately twice as large as the first thickness by an oxidation process.

Accordingly, the first insulating film 212a filling the inside of the trench 206 is compressed by the expansion pressure of the polysilicon oxide film 210b surrounding the first insulating film 212a. As a result, the first insulating film 212a existing in the trench 206 may be formed as a second insulating film 212b having a second density greater than the first density, thereby making the film quality dense. Therefore, the second insulating layer 212b may have an increased etch resistance in a subsequent wet etching process to facilitate thickness control during etching. In particular, when a void is present in the trench 206, the void may disappear due to the compression of the insulating layer.

In other words, the insulating film such as SOG has an advantage of easily filling the trench 206 having a fine line width compared to the HDP oxide film due to its flow characteristics. On the other hand, since SOG has a very low density compared to the HDP oxide film, there is a problem that the thickness control is very difficult since it is excessively etched in a chemical mechanical polishing process or a wet etching process. Accordingly, the problem may be easily solved by improving the density of the first insulating film 212a having fluidity using the polysilicon film 210a.

Meanwhile, the volume expansion generated when the polysilicon film 210a is converted to the polysilicon oxide film 210b may be applied to not only the first insulating film 212a but also to sidewalls of the trench 206 positioned in the opposite direction. Stress). Specifically, since the pressure exerts a predetermined stress on the silicon lattice forming the sidewalls of the trench 206, the damage of the silicon lattice may be alleviated. Thus, the operating characteristics of the device can be further improved.

At the same time, the organic materials included in the SOG composition are removed by the heat treatment process, and thus the SOG composition may be formed of silicon oxide. Alternatively, a high curing process for removing the organic solvent included in the fluid film such as the SOG composition may be separately performed before the heat treatment process.

Referring to FIG. 7, portions of the first insulating film 212a, the nitride film liner 208, and the hard mask 204 existing on the upper surface of the substrate 200 are removed. The removal may be performed by a chemical mechanical polishing process or an etch back process. Subsequently, the hard mask 204 and the nitride film liner 208 remaining after the process is completed are completely removed. The removal may be performed by a wet etching process including phosphoric acid (H ₂ PO ₄ ).

Referring to FIG. 8, the buffer oxide layer 202 remaining on the substrate 200 is removed. The removal may be performed through a wet etching process such as SC1. When the buffer oxide layer 202 is removed, a portion of the upper portion of the second insulating layer 212b is also removed. Here, when the second insulating film 212b is an oxide film formed from the SOG composition by the SOG process, the etching ratio may be larger than that of the buffer oxide film 212b. However, since the film quality of the second insulating film 212b is dense by the polysilicon oxide film 210b to increase the etch resistance, the phenomenon that the second insulating film 212b is excessively etched can be suppressed.

Finally, the gate oxide layer 214 is formed on the upper surface of the substrate 200 and the second insulating layer 212b to complete the trench 206 device isolation structure.

According to the present invention, the opening filler film can be densified using the expandable member formed on the inner side of the opening. Accordingly, etching resistance such as wet etching may be increased.

In addition, when the trench filling method is used to form the trench isolation structure, the film quality of the isolation layer can be densified to effectively suppress the voids and to improve the electrical characteristics of the device by curing the silicon lattice generated on the sidewalls of the opening. Can be.

In this way, by securing the electrical characteristics of the device having a line width of 90 nm or less, the reliability of the semiconductor device can be improved.

Although the above has been described with reference to a preferred embodiment of the present invention, those skilled in the art will be able to variously modify and change the present invention without departing from the spirit and scope of the invention as set forth in the claims below. It will be appreciated.

1 to 3 are cross-sectional views illustrating an opening filling method according to an embodiment of the present invention.

4 to 8 are cross-sectional views illustrating a method of forming a device isolation structure according to another exemplary embodiment of the present invention.

Explanation of symbols on the main parts of the drawings

100, 200: substrate 102: mask pattern

104 opening 106a first expandable member

106b: second expandable member 108a: first filler

108b: second charge 202: buffer oxide film

204: Hard Mask 206: Trench

208: nitride film liner 210a: first polysilicon film

210b: polysilicon oxide film 212a: first insulating film

212b: second insulating film 214: gate oxide film

Claims (10)

Partially etching the substrate to form an opening; Forming an expandable member on the sidewall of the opening; Forming a fill on the inflatable member that sufficiently fills the opening; And Increasing the volume of the expandable member to increase the density of the filler present within the opening. The method of claim 1 wherein the expandable member is made of polysilicon. 3. The method of claim 2, wherein increasing the volume of the expandable member is performed by converting substantially all of the polysilicon film into a polysilicon oxide film through a thermal oxidation process. 4. The method of claim 3, wherein the filler is an insulating film. Forming openings in the substrate for defining device isolation regions; Forming a polysilicon film having a first thickness on the inner surface of the opening; Forming an insulating film filling the opening sufficiently on the polysilicon film; And Converting the polysilicon film into a polysilicon oxide film having a second thickness thicker than the first thickness to increase the packing density of the insulating film by increasing the volume of the polysilicon film. 6. The method of claim 5 wherein the opening has a line width of about 30 to 90 nm. The method of claim 6, wherein the polysilicon film is formed to a thickness of 50 to 200 μm. 6. The method of claim 5, further comprising forming a nitride film on the thermal oxide film to prevent oxidation of the inner surface of the opening before forming the polysilicon film. The method of claim 5, wherein the insulating layer is formed of an SOG composition formed through a spin on glass (SOG) process or a BPSG oxide formed by a chemical vapor deposition process. The method of claim 5, wherein the heat treatment is performed through an annealing process under an oxygen (O) atmosphere and a temperature of 700 to 1000 ° C. 7.