JPH08195438A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE: To provide a manufacturing method of a semiconductor device, in which an insulating film can be made flat without lowering the reliability of the semiconductor device. CONSTITUTION: A doped polysilicon film 4 is formed on a TEOS oxide film 3 whose surface has differences in level. After that, impurities in the doped polysilicon film 4 are diffused into the TEOS oxide film 3. Then, the doped polysilicon film 4 is removed, an etching operation whose selectivity with reference to a heavily doped silicon nitride film is executed, and a TEOS oxide film 3a into which the impurities have been diffused is etched. Since the diffusion boundary face S of the impurities in the TEOS oxide film 3 is formed to be nearly flat, the surface of an insulating film is flattened by an etching operation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a semiconductor device having an interlayer insulating film between wirings, and more particularly to flattening the interlayer insulating film.

[0002]

2. Description of the Related Art Currently, semiconductor devices such as LSI (I
In C), there is a strong tendency toward high integration of circuits, and miniaturization of wiring patterns and multilayering of wiring are being promoted every day. In such a semiconductor device having a multi-layer structure, a step is likely to occur in the insulating film formed on the wiring, and due to the increase in the number of wiring layers, a step for each layer is accumulated in the insulating film on the upper layer side. A large unevenness is generated on the surface. Since such a step causes various defects in transfer, etching, film formation, etc., and becomes a major obstacle in manufacturing a semiconductor device, a flattening process for reducing the step of the insulating film is developed. Is being advanced.

There are various methods for the flattening process. One example is a method of dissolving silicon oxide in a solvent, dropping this viscous liquid on the wiring, and then rotating at high speed to form a uniform SOG film. Are known. In this method, the SOG film, which is a spin coating film, is thickly applied to the recesses by the balance between the capillarity and the centrifugal force to form an insulating film having a flat surface.

Also, for example, TEOS (Tetra-Ethyl-Orth)
A method of forming a silicon oxide film (hereinafter referred to as TEOS oxide film) on a wiring pattern by CVD using o-Silicate, Si (C ₂ H ₅ OH) ₅ ) as a source gas is known.

Also, B is formed on the wiring pattern by CVD.
A silicon oxide film (hereinafter referred to as a BPSG film) formed so as to contain (boron) and P (phosphorus) is formed, and then the surface of the BPSG film is subjected to reflow (heat is applied to the BPSG film to fluidize it). A method of flattening is known.

[0006]

However, in the case of a semiconductor device having an SOG film formed by rotating at a high speed, when the film thickness of the recess is increased, the stress generated when the silicon oxide is solidified by the evaporation of the solvent is also increased. Therefore, there is a problem that the base shape is apt to be affected such that cracks are easily generated and the viscous liquid is hard to enter the narrow gap.

Further, in the case of a semiconductor device which is flattened by a TEOS oxide film, the TEOS oxide film is formed so as to sufficiently fill a narrow gap or hole, but in a semiconductor device having a multilayer structure, it is still sufficient. There is a problem that the interlayer insulating film cannot be flattened.

Further, in the case of a semiconductor device in which the BPSG film is flattened by reflow, an oxidizing species (O) is formed even in the wiring located under the BPSG film by heat treatment during reflow.
₂ ) diffuses and oxidizes this wiring, which reduces the reliability of the semiconductor device.

The present invention has been made to solve the above problems, and provides a method for manufacturing a semiconductor device in which a sufficiently flat insulating film can be formed without lowering the reliability of the semiconductor device. The purpose is to

[0010]

In the method of manufacturing a semiconductor device according to the first aspect of the present invention, after forming a doped polysilicon film on a silicon oxide film, impurities in the doped polysilicon film are removed from the silicon oxide film. Then, the doped polysilicon film is removed, and then the silicon oxide film having a high impurity concentration is subjected to highly selective etching to etch the silicon oxide film in which the impurities are diffused. It is something to process.

In the method of manufacturing a semiconductor device according to a second aspect of the present invention, after forming a coating forming film on the silicon oxide film to flatten the surface, nitrogen ions are implanted from the surface of the coating forming film, A flat silicon nitride film is formed in the silicon oxide film, and then etching having a higher selectivity to the silicon oxide film than the silicon nitride film is performed, so that the silicon oxide film is formed until the silicon nitride film appears on the surface. Etching processing is performed.

According to a third aspect of the present invention, there is provided a method of manufacturing a semiconductor device according to the first or second aspect, wherein the silicon oxide film is a TEOS oxide film formed by CVD using TEOS as a source gas. It is a film.

According to a fourth aspect of the present invention, there is provided a method of manufacturing a semiconductor device according to the third aspect, wherein P, which is an impurity, is thermally diffused into the TEOS oxide film.
After removing the doped polysilicon film by dry etching with CF ₄ , T is wet-etched with hydrofluoric acid.
The EOS oxide film is etched.

According to a fifth aspect of the present invention, there is provided a method of manufacturing a semiconductor device according to the second or third aspect, wherein the coating film is planarized by spin coating on the silicon oxide film. It has been formed.

According to a sixth aspect of the present invention, there is provided a method of manufacturing a semiconductor device according to the second aspect, wherein buffered hydrofluoric acid is used as an etching solution for etching.

In the method of manufacturing a semiconductor device according to a seventh aspect of the present invention, nitrogen ions are implanted into a BPSG film having a step on the surface to form a flat silicon nitride film in the BPSG film, and then a silicon nitride film is formed. The BPSG film on the film is reflowed to flatten the surface of the BPSG film.

[0017]

In the method of manufacturing a semiconductor device according to the first aspect of the present invention, the impurity in the doped polysilicon film is diffused into the silicon oxide film having a step on the surface, and the diffusion boundary surface of the impurity is silicon. It is formed flat in the oxide film. Next, a highly selective etching is performed on the silicon oxide film having a high impurity concentration, and the silicon oxide film is etched to form a flat silicon oxide film whose surface is substantially along the impurity diffusion boundary surface. It

In the method of manufacturing a semiconductor device according to a second aspect of the present invention, nitrogen ions are implanted into the silicon oxide film having a step on the surface through the coating forming film to flatten the silicon oxide film. A simple silicon nitride film is formed.
Next, etching having a higher selectivity for the silicon oxide film than the silicon nitride film is performed, and the silicon oxide film is etched to form a flat insulating film having the silicon nitride film on the surface.

In a method of manufacturing a semiconductor device according to a third aspect of the present invention, a TEOS oxide film is formed on a wiring by CVD using TEOS as a source gas as a silicon oxide film.

In the method of manufacturing a semiconductor device according to a fourth aspect of the present invention, the doped polysilicon film is efficiently removed by dry etching with CF ₄ , and the TEOS oxide film is efficiently removed by wet etching with hydrofluoric acid. It

In the method of manufacturing the semiconductor device according to the fifth aspect of the present invention, the coating film is easily planarized on the silicon oxide film by spin coating.

In the method of manufacturing a semiconductor device according to the sixth aspect of the present invention, the silicon oxide film is efficiently etched by buffered hydrofluoric acid.

In the method of manufacturing a semiconductor device according to a seventh aspect of the present invention, after the silicon nitride film is formed in the BPSG film having a step on the surface, the surface of the BPSG film is flattened by reflowing to form a surface. A flat insulating film is formed on. In this case, the silicon nitride film in the BPSG film prevents oxidation of the wiring below the insulating film during reflow.

[0024]

Embodiments of the present invention will be described below with reference to the drawings. Example 1. FIG. 1 is an explanatory diagram of a method of manufacturing a semiconductor device according to an embodiment of the present invention. In the figure, reference numeral 1 is a conductive wiring, and the wiring 1 has a size of, for example, a width of 0.6 μm, a pitch between wirings of 0.3 μm, and a film thickness of 2000 angstrom (hereinafter referred to as A). 3 is T on the wiring 1
EOS (Tetra-Ethyl-Ortho-Silicate, Si (C ₂ H ₅
It is a TEOS oxide film which is a silicon oxide film formed by CVD using OH) ₅ ) as a source gas. Above the TEOS oxide film 3 having excellent flatness, a doping layer 3a in which impurities are diffused is formed with the boundary S as a boundary.
Reference numeral 4 is a doped polysilicon film formed by CVD on the TEOS oxide film 3. The doped polysilicon film 4 is doped with P (phosphorus), for example.

Next, a method of manufacturing a semiconductor device in which the flat TEOS oxide film 3 is formed on the wiring 1 will be described.
When the TEOS oxide film 3 is formed on the wiring 1 to have a film thickness of, for example, 8000 A, an uneven step which is affected by the gap between the wirings 1 is formed on the upper surface of the TEOS oxide film 3. However, since the TEOS oxide film 3 has good flatness and is formed so as to sufficiently fill the narrow gaps and holes, the convex portion 3b on the front surface side is formed.
The groove of the concave portion 3c is formed narrower than that of.

Next, a doped polysilicon film 4 is formed on the TEOS oxide film 3 by CVD with a film thickness of 3000 A, for example, and then the doped polysilicon film 4 side is heated to form the doped polysilicon film 4 therein. Impurity (P) in TE
Heat is diffused into the OS oxide film 3. Then, a doping layer 3a having a film thickness of 6000 A and an impurity (P) concentration of about 10 mol% is formed in the TEOS oxide film 3. In this case, since the groove of the concave portion 3c is sufficiently narrower than the convex portion 3b of the TEOS oxide film 3, the convex portion 3b far from the wiring 1 is formed.
Impurities (P) from the recess 3c side closer to the wiring 1 than the side
Is small, and as a result, the boundary surface S between the doping layer 3a and the TEOS oxide film 3 in which no impurity is diffused is sufficiently flat.

Next, after removing the doped polysilicon film 4 by dry etching using, for example, CF ₄ , an etching method having selectivity for the TEOS oxide film having a high impurity concentration, in this embodiment, for example, a fluorine film is used. Wet etching using acid as an etching solution provides TEO
The S oxide film 3 is etched. In this case, the doping layer 3a is etched quickly, and the TEOS oxide film 3 containing no impurity (P) is etched slowly. Therefore, for example, impurities (P) on the wiring 1
By etching until the film thickness of the TEOS oxide film 3 which does not include is about 2500 A, the flat TEOS oxide film 3 along the boundary surface S can be formed on the wiring 1.

As described above, in this method of manufacturing a semiconductor device, the doping layer is formed on the upper surface of the TEOS oxide film 3 having a stepped surface so that the boundary surface S is flattened through the doped polysilicon film 4. After forming 3a, the TEOS oxide film 3 is etched by an etching method having a selectivity with respect to a silicon oxide film having a high impurity concentration, so that a flat TEOS oxide film is formed on the wiring 1. it can. That is, in this semiconductor device manufacturing method, a sufficiently flat insulating film can be easily formed on the wiring 1.

Example 2. FIG. 2 is an explanatory diagram of a method of manufacturing a semiconductor device according to another embodiment of the present invention. The same parts as those shown in the first embodiment are designated by the same reference numerals and the description thereof will be omitted. In the figure, 5 is a coating film formed on the TEOS oxide film 3. This coating formation film is, for example, a SOG film as a silicon oxide film formed by spin-coating a glass solution dissolved in a solvent on the TEOS oxide film 3 and then performing heat treatment. Reference numeral 6 is nitrogen ions accelerated on the surface side of the coating formation film 5, and 7 is a silicon nitride film formed between the TEOS oxide film 3 and the wiring 1.

Next, a method of manufacturing the semiconductor device of this embodiment will be described. A TEOS oxide film 3 is formed on the wiring 1.
After the film having a thickness of 000 A is formed, a coating formation film 5 is formed on the TEOS oxide film 3 by a spin coating method so as to fill the step on the surface of the TEOS oxide film 3, and the surface is flattened. Next, nitrogen ions 6 are implanted from the flat surface side of the coating formation film 5 at an implantation energy of, for example, 300 Kev, and the silicon nitride film 7 is formed in the TEOS oxide film 3 having a depth of 6000 A from the surface of the coating formation film 5. To form. In this case, since the implantation surface of the nitrogen ions 6 is formed flat by the coating formation film 5, the silicon nitride film 7 is formed flat so as to be parallel to the wiring 1.

Next, the TEOS oxide film 3 on the silicon nitride film 7 is formed by an etching method having a higher selectivity for the silicon oxide film than the silicon nitride film 7, that is, wet etching using buffered hydrofluoric acid as an etching solution in this embodiment. And the coating formation film 5 is removed by etching. In this case, the etching stops the reaction when the silicon nitride film 7 appears, so that TEOS is not formed on the wiring 1.
A flat insulating film is formed by covering the oxide film 3 with the silicon nitride film 7.

As described above, also in this semiconductor device manufacturing method, as in the case of the semiconductor device manufacturing method of the first embodiment, a flat insulating film can be easily formed on the wiring 1. Further, the coating formation film 5, which is an SOG film that easily causes cracks, is finally removed, and a highly reliable semiconductor device can be obtained.

Example 3. FIG. 3 is an explanatory view of a method of manufacturing a semiconductor device according to still another embodiment of the present invention. The same parts as those shown in the first embodiment are designated by the same reference numerals and the description thereof will be omitted. In the figure, 8 is on the wiring 1,
It is a BPSG film which is a silicon oxide film having a melting point lower than that of the TEOS oxide film 3 of the first and second embodiments, which is formed by CVD so as to contain boron (B) and phosphorus (P). 9 is a silicon nitride film formed in the BPSG film 8.

Next, a method of manufacturing a semiconductor device in which a flat insulating film (BPSG film 8 and silicon nitride film 9 in this case) is formed on the wiring 1 will be described. First, the BPSG film 8 is formed on the wiring 1 to have a film thickness of 8000 A, for example. In this case, an uneven step is formed on the upper surface of the BPSG film 8 under the influence of the step (inter-wiring gap) of the wire 1. Next, from the surface of the BPSG film 8, for example, 300
Nitrogen ion 6 is implanted with the implantation energy of Kev, and BP is
A silicon nitride film 9 is formed in the SG film 8 at a depth of 6000 A from the surface, for example. In this case, the silicon nitride film 9 reflects the unevenness of the surface of the BPSG film 8, and the distance between the surface and the silicon nitride film 9 is constant, but is formed in an uneven shape as a whole.

Next, BPS above the silicon nitride film 9
The G film 8 is reflowed (heat is applied to the BPSG film 8 to
The PSG film 8 is fluidized) and the surface of the BPSG film 8 is flattened. When reflowing, oxygen in the air and BPSG
Oxygen in the film 8 moves to the wiring 1 side and tries to oxidize the wiring 1. However, since the silicon nitride film 9 blocks the movement of oxygen to the wiring 1 side, the wiring 1 is hardly oxidized. . Since the BPSG film 8 has a lower reflow temperature than other insulating films such as the TEOS oxide film 3, reflow is facilitated.

As described above, also in this semiconductor device manufacturing method, a flat insulating film can be easily formed on the wiring 1 as in the case of the first embodiment. Further, during the reflow, the silicon nitride film 9 prevents the wiring from being oxidized, so that a highly reliable semiconductor device can be obtained.

Although TEOS was used as the raw material for forming the silicon oxide film in each of the above embodiments, SiH ₄ ,
It may be SiH ₂ Cl ₂ , Si ₄ C ₈ H ₂₄ O ₄ or the like.

[0038]

As described above, according to the method of manufacturing the semiconductor device of the first aspect of the present invention, the impurity in the doped polysilicon film is diffused into the silicon oxide film, and the impurity diffusion boundary is formed. A flat surface can be easily formed by forming a flat surface in the silicon oxide film, then performing etching with high selectivity on the silicon oxide film with a high impurity concentration, and etching the silicon oxide film. It has the effect of being formed.

Further, according to the method of manufacturing a semiconductor device of the second aspect of the present invention, nitrogen ions are implanted into the silicon oxide film through the coating formation film, and flat silicon nitride is formed in the silicon oxide film. A flat insulating film with a silicon nitride film on the surface is easily formed by forming a film, then performing etching with higher selectivity to the silicon oxide film than the silicon nitride film, and etching the silicon oxide film. There is an effect that is done.

Further, according to the method of manufacturing a semiconductor device of claim 3 of the present invention, in the method of manufacturing a semiconductor device of claim 1 or 2, the silicon oxide film is TEO.
TEO on the wiring by CVD using S as a source gas
Since the S oxide film is formed, in addition to the effect of the invention according to claim 1 or 2, TEOS flatter on the wiring is formed.
There is also an effect that an oxide film is formed.

According to the method of manufacturing a semiconductor device of claim 4 of the present invention, in addition to the effect of the invention of claim 3, dry etching by CF _{4 is performed in the} method of manufacturing a semiconductor device of claim 3. The doped polysilicon film is efficiently removed, and the TEOS oxide film is also effectively removed by wet etching with hydrofluoric acid.

According to the semiconductor device manufacturing method of the fifth aspect of the present invention, in addition to the effects of the second and third aspects, in the semiconductor device manufacturing method of the second or third aspect. Another effect is that the coating film is easily flattened on the silicon oxide film by spin coating.

According to the semiconductor device manufacturing method of the sixth aspect of the present invention, in addition to the effect of the second aspect of the invention, the silicon oxide film is effectively etched by the buffered hydrofluoric acid. is there.

According to the semiconductor device manufacturing method of the seventh aspect of the present invention, there is an effect that the surface of the BPSG film is easily planarized by forming the silicon nitride film in the BPSG film and then reflowing. In addition, the silicon nitride film in the BPSG film prevents the wiring under the insulating film from being oxidized during the reflow process, so that a highly reliable semiconductor device can be obtained.

[Brief description of drawings]

FIG. 1 is an explanatory diagram illustrating a method for manufacturing a semiconductor device according to a first embodiment of the invention.

FIG. 2 is an explanatory diagram illustrating a method for manufacturing a semiconductor device according to a second embodiment of the invention.

FIG. 3 is an explanatory diagram illustrating a method for manufacturing a semiconductor device according to a third embodiment of the invention.

[Explanation of symbols]

3 TEOS oxide film, 3a doping layer, 4 doped polysilicon film, 5 coating film, 6 nitrogen ion, 7
Silicon nitride film, 8 BPSG film, 9 silicon nitride film.

Claims (7)

[Claims] 1. A doped polysilicon film is formed on a silicon oxide film, impurities in the doped polysilicon film are diffused into the silicon oxide film, and then the doped polysilicon film is removed. After that, a method for manufacturing a semiconductor device is characterized in that the silicon oxide film having a high impurity concentration is subjected to etching with high selectivity to etch the silicon oxide film in which the impurities are diffused. 2. A coating formation film is formed on a silicon oxide film to planarize the surface, and then nitrogen ions are implanted from the surface of the coating formation film to form a flat silicon nitride film in the silicon oxide film. Formed, and then etching having a higher selectivity for a silicon oxide film than a silicon nitride film is performed, and the etching process of the silicon oxide film is performed until the silicon nitride film appears on the surface of the semiconductor device. Production method. 3. The method of manufacturing a semiconductor device according to claim 1, wherein the silicon oxide film is a TEOS oxide film formed by CVD using TEOS as a source gas. 4. The TEOS oxide film is etched by wet etching with hydrofluoric acid after the impurity P is thermally diffused into the TEOS oxide film, the doped polysilicon film is removed by dry etching with CF _4. The method for manufacturing a semiconductor device according to claim 3. 5. The method of manufacturing a semiconductor device according to claim 2, wherein the coating formation film is formed by planarizing the silicon oxide film by spin coating. 6. The method of manufacturing a semiconductor device according to claim 2, wherein buffered hydrofluoric acid is used as an etching solution for etching. 7. A nitrogen ion is implanted into the BPSG film,
After forming a flat silicon nitride film in the BPSG film, the BPSG film on the silicon nitride film is reflowed to form the BPS film.
A method of manufacturing a semiconductor device, which comprises planarizing a surface of a G film.