JPH07326745A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To contrive the improvement of a method of forming the so-called twin well, which is used in a semiconductor device which is made progress in high miniaturization. CONSTITUTION:An oxide film 12, a first nitride film 13, a polysilicon layer 14 and a second nitride film 15 are formed in order on a semiconductor substrate 11, a resist film 16 is selectively formed on the film 15, the film 15 is removed by etching using the film 16 as a mask, one conductivity type impurities are implanted using the films 16 and 15 as masks and a one conductivity type impurity region layer 17 is formed in the surface layer of the substrate 11. Moreover, the layer 14 is selectively oxidized using the film 15 as a mask to form a selective oxide film 18 on the layer 17, the film 15 is removed, reverse conductivity type impurities are implanted using the film 18 as a mask and a reverse conductivity type impurity region layer 19 is formed in the surface layer of the substrate 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor device, and more particularly to an improvement in a so-called twin well forming method used for a semiconductor device which has been highly miniaturized.

[0002]

2. Description of the Related Art A conventional method of manufacturing a semiconductor device will be described below with reference to the drawings. MOSFE
When forming a semiconductor device such as T, an n-type impurity diffusion layer (n-well) and a p-type impurity diffusion layer (p-w) are formed.
cell) may be formed adjacent to each other to form a so-called twin well.

In this case, in order to form the n-well and the p-well in separate mask processes, the mask process needs to be performed twice, and the n-well and p-well are further required.
In consideration of the misalignment of the mask alignment, it is necessary to create a vacant area with a margin at the boundary between the two, so miniaturization cannot be achieved by the vacant area. Therefore, there is a demand for forming both of them by self-alignment so as to complete the mask process only once.

One of the methods is LOCOS (Local Oxid).
A method of forming a selective oxide film by the cation of silicon) method has been proposed. The method will be described below with reference to FIGS. 11 to 14. First, as shown in FIG. 11, a SiO2 film (2) and a SiN film (3) are sequentially formed on a silicon substrate (1), and then a resist film (so as to expose a region where a p-well is formed). 4) Selectively form
Using the resist film (4) as a mask, the SiN film (3) is etched and removed, boron (B) is ion-implanted, and p-we
to form 11 (5).

Next, the resist film (4) is removed, and FIG.
As shown in FIG. 3, the SiO2 film (2) is selectively oxidized by the LOCOS method to selectively form the selective oxide film (6) on the p-well (5). Then, the SiN film (3) is removed, and FIG.
As shown in, phosphorus (P) is used with the selective oxide film (6) as a mask.
Ions are implanted to form an n-well (7).

Thereafter, as shown in FIG. 14, the selective oxide film (6) and the SiO2 film (2) on the entire surface are etched and removed to expose the surfaces of the p-well (5) and the n-well (7). To do. As described above, the twin well is formed by self-alignment in which it is not necessary to form a vacant region in consideration of misalignment.

[0007]

However, according to the above conventional manufacturing method, although the twin well can be formed by self-alignment, as shown in FIG.
When the selective oxide film (6) is formed, the surface of the semiconductor substrate (1) is oxidized and the selective oxide film (6) on the p-well (5) is embedded in the surface layer of the semiconductor substrate (1). I will end up.

For this reason, when the n-well (7) is formed thereafter, the surface layer of the n-well (7) is flat. Therefore, after removing the selective oxide film (6), the surface of the semiconductor substrate (1) is about 3000 Å. The level difference (ΔL) is formed and the flatness is impaired.

[0009]

The present invention has been made in view of the above-mentioned conventional drawbacks. As shown in FIGS. 1 to 5, an oxide film (12) and a first oxide film (12) are formed on a semiconductor substrate (11). Nitride film (1
3), the polysilicon layer (14) and the second nitride film (1
5) step of sequentially forming the second nitride film (15)
A step of selectively forming a resist film (16) on the upper surface, etching and removing the second nitride film (15) using the resist film (16) as a mask, and the resist film (16)
And a step of implanting an impurity of one conductivity type using the second nitride film (15) as a mask to form an impurity region layer (17) of one conductivity type in a surface layer of the semiconductor substrate (11); Of the first conductivity type impurity region layer (1) by selectively oxidizing the polysilicon layer (14) using the nitride film (15) of (1) as a mask.
7) a step of forming a selective oxide film (18) thereon, and removing the second nitride film (15) to remove the selective oxide film (18).
And a step of injecting an impurity of opposite conductivity type to form an impurity region layer (19) of opposite conductivity type on the surface layer of the semiconductor substrate (11) by self-alignment without a step. A method of manufacturing a semiconductor device that can be formed.

[0010]

[Operation] According to the first method for manufacturing a semiconductor device of the present invention, as shown in FIGS.
An oxide film (12), a first nitride film (13), a polysilicon layer (14) and a second nitride film (15) are sequentially formed on the second nitride film (15) and a resist film (16). ) And are used as a mask to implant an impurity of one conductivity type to form an impurity region layer (17) of one conductivity type on the surface layer of the semiconductor substrate (11) and to form a second nitride film (15). Using the mask as a mask, the polysilicon layer (14) is selectively oxidized to form a selective oxide film (18) on the one conductivity type impurity region layer (17), the second nitride film (15) is removed, and the selective oxide film is removed. (1
Reverse conductivity type impurities are implanted using 8) as a mask to form a reverse conductivity type impurity region layer (19) on the surface layer of the semiconductor substrate (11).

Therefore, in the step of selectively oxidizing the polysilicon layer (14) to form the selective oxide film (18), the first nitride film (13) is formed below the polysilicon layer (14). Since it is provided, the oxidation of the polysilicon layer (14) is stopped here, and the semiconductor substrate (11) thereunder is prevented from being oxidized, so that the selective oxide film (18) is formed on the semiconductor substrate (11). ) Does not go into the surface.

As a result, even if the opposite conductivity type impurity is implanted by using the selective oxide film (18) as a mask and the opposite conductivity type impurity region layer (19) is formed on the surface layer of the semiconductor substrate (11), the selection is performed. Since the oxide film (18) does not sink into the semiconductor substrate (11), it is possible to suppress the generation of a step which has been conventionally caused by this as much as possible, and to prevent the flatness of the semiconductor substrate surface from being impaired as much as possible. Moreover, it is possible to form the twin well by self-alignment.

According to the second method for manufacturing a semiconductor device of the present invention, as shown in FIGS. 6 to 10, an oxide film (22) and a polysilicon layer (2) are formed on a semiconductor substrate (21).
3) and a nitride film (24) are sequentially formed to form a nitride film (24)
And the resist film (25) is patterned and one conductivity type impurities are implanted using these as a mask to form a one conductivity type impurity region layer (26) on the surface layer of the semiconductor substrate (21), and the nitride film (24 ) As a mask, and the polysilicon layer (2
3) is selectively oxidized to form a selective oxide film (27) on the one conductivity type impurity region layer (26).

Therefore, when the selective oxidation film (27) is formed, the semiconductor substrate (2
Since 1) is prevented from being oxidized, the selective oxide film (27) does not sink into the surface layer of the semiconductor substrate (21). As a result, the selective oxide film (21) is removed from the semiconductor substrate (2).
Since it is possible to suppress the generation of a step which has been conventionally caused by being recessed into 1), it is possible to prevent the flatness of the semiconductor substrate surface from being impaired as much as possible, and it is possible to form a twin well by self-alignment. Become.

[0015]

【Example】

(1) First Example Hereinafter, a method for manufacturing a semiconductor device according to a first example of the present invention will be described with reference to the drawings. First, Fig. 1
As shown in FIG.
An oxide film (12) of 300 Å, a first nitride film (13) of 100 to 200 Å film thickness, a polysilicon layer (14) of 2000 to 3000 Å film thickness and a second nitride film (15) of 1000 Å film thickness are sequentially formed. Form.

Next, as shown in FIG. 2, a photoresist is applied on the second nitride film (15), exposed and developed,
After that, patterning is performed so that a region for forming the p-well (17) is exposed to selectively form a resist film (16) having a film thickness of about 1 μm, and the second nitride film is formed using the resist film (16) as a mask. After etching and removing (14), boron (B) is ion-implanted using the resist film (16) and the second nitride film (15) as a mask to p-we
11 (17) is formed.

Then, as shown in FIG. 3, the resist film (16) is removed, the second nitride film (15) is used as a mask, and the polysilicon layer (14) is selectively oxidized by the LOCOS method to obtain a film thickness. 2000-3000Å selective oxide film (1
8) is formed. In this step, a first nitride film (1) having oxidation resistance is formed under the polysilicon layer (14).
3) is formed, the oxidation of the polysilicon layer (14) is stopped up to this point, and the silicon substrate (1) below it is oxidized.
It is not oxidized until 1).

Therefore, the silicon substrate (1
It is possible to prevent the selective oxide film (18) from being dented on the substrate surface due to the oxidation of 1). Next, as shown in FIG. 4, the second nitride film (15) and the polysilicon layer (14) are sequentially etched and removed by dry etching to remove the selective oxide film (1
8) is used as a mask and phosphorus (P) ions are added to the silicon substrate (1
Ions are implanted into the surface layer of 1) to form an n-well (19).

After that, the selective oxide film (18) and the oxide film (12) are removed, and as shown in FIG.
(17) By exposing the n-well (19), twin wells are formed by self-alignment. As a result, since the selective oxide film (18) does not sink into the surface of the silicon substrate (11) as described above, a step which is generated by the conventional selective oxide film sinking into the substrate surface is generated as shown in FIG. Can be suppressed as much as possible, and the twin well can be formed by self-alignment while suppressing the flatness of the silicon substrate (11) as much as possible.

(2) Second Embodiment A semiconductor device manufacturing method according to the second embodiment of the present invention will be described below with reference to the drawings. The first
The description of the items common to those of the first embodiment will be omitted to avoid duplication. First, as shown in FIG. 6, an oxide film (22) having a film thickness of 500Å and a film thickness of 2 are formed on a silicon substrate (21).
A polysilicon layer (23) having a thickness of 000 to 3000 Å and a nitride film (24) having a film thickness of about 1000 Å are sequentially formed.

Next, as shown in FIG. 7, a photoresist is applied on the nitride film (24), exposed and developed, and then p.
-A resist film (25) having a film thickness of about 1 μm is selectively formed by patterning so as to expose a region where a well (26) is formed, and the nitride film (24) is etched using the resist film (25) as a mask.・ After removal,
Boron (B) is ion-implanted by using the resist film (25) and the nitride film (24) as a mask to p-well (2
6) is formed.

Then, as shown in FIG. 8, the resist film (25) is removed, and the nitride film (24) is used as a mask to remove H.
A film thickness of 2000 is obtained by introducing 2 O gas and selectively oxidizing the polysilicon layer (23) for 200 minutes at a temperature of 900 ° C.
A selective oxide film (27) of ˜3000 Å is formed. At this time, by selecting the above conditions, the silicon substrate (21) is simultaneously oxidized during the selective oxidation of the polysilicon layer (14).
Keep it from being oxidized.

Therefore, the silicon substrate (2
It is possible to prevent the selective oxide film (27) from invading the substrate surface due to the oxidation of 1). Next, as shown in FIG. 9, the nitride film (24) and the polysilicon layer (23) are sequentially etched and removed by dry etching, and the selective oxide film (27) is used as a mask to remove phosphorus (P) ions from the silicon substrate ( Ions are implanted into the surface layer of 21) to form an n-well (28).

After that, the selective oxide film (27) and the oxide film (22) are removed, and as shown in FIG.
Twin wells can be formed by exposing l (26) and n-well (28). As a result, since the selective oxide film (27) is not recessed into the surface of the silicon substrate (21) as described above, the step generated by the conventional selective oxide film being recessed into the substrate surface is generated as shown in FIG. Can be suppressed as much as possible, and the twin well is formed by self-alignment while suppressing the flatness of the silicon substrate (21) as much as possible.

Further, unlike the first embodiment, the LO layer is formed without forming the oxidation resistant nitride film under the polysilicon layer.
Since the oxidation of the silicon substrate (21) is suppressed by adjusting the conditions of COS oxidation, the labor saving of the process can be realized because the nitride film for that is not formed.

[0026]

As described above, according to the first semiconductor device manufacturing method of the present invention, the second nitride film (15) is formed.
And the resist film (16) are patterned, and impurities of one conductivity type are implanted using these as a mask, and the semiconductor substrate (1
Forming a one conductivity type impurity region layer (17) on the surface layer of 1),
The polysilicon layer (14) is selectively oxidized by using the second nitride film (15) as a mask to form the one conductivity type impurity region layer (17).
A selective oxide film (18) is formed on the second nitride film (1
5) is removed, and an impurity of opposite conductivity type is implanted using the selective oxide film (18) as a mask to form an impurity region layer of opposite conductivity type (19) on the surface layer of the semiconductor substrate (11).

For this reason, since the selective oxide film (18) is not embedded in the semiconductor substrate (11), it is possible to suppress the occurrence of a step which has been conventionally caused by this as much as possible.
It becomes possible to prevent the flatness of the surface of the semiconductor substrate from being impaired as much as possible and to form the twin well by self-alignment. Further, according to the second semiconductor device manufacturing method of the present invention, the nitride film (24) and the resist film (2
5) is patterned and one conductivity type impurities are implanted using these as a mask to form a one conductivity type impurity region layer (26) on the surface layer of the semiconductor substrate (21), and the nitride film (24) is used as a mask. The selective oxidation film (27) is formed on the one conductivity type impurity region layer (26) by selectively oxidizing the polysilicon layer (23) to such an extent that the semiconductor substrate (21) is not oxidized under appropriate conditions.

Therefore, when the selective oxide film (27) is formed, the semiconductor substrate (2
1) is prevented from being oxidized, and the selective oxide film (21)
Since it is possible to suppress as much as possible the generation of a step that has conventionally occurred when the semiconductor substrate (21) is embedded in the semiconductor substrate (21), it is possible to prevent the flatness of the semiconductor substrate surface from being impaired as much as possible.
In addition, twin wells can be formed by self-alignment.

[Brief description of drawings]

FIG. 1 is a first sectional view illustrating a method for manufacturing a semiconductor device according to a first embodiment of the present invention.

FIG. 2 is a second sectional view illustrating the method for manufacturing the semiconductor device according to the first embodiment of the invention.

FIG. 3 is a third sectional view illustrating the method for manufacturing the semiconductor device according to the first embodiment of the invention.

FIG. 4 is a fourth sectional view illustrating the method for manufacturing the semiconductor device according to the first embodiment of the invention.

FIG. 5 is a fifth sectional view illustrating the method for manufacturing the semiconductor device according to the first embodiment of the invention.

FIG. 6 is a first cross-sectional view illustrating the method for manufacturing the semiconductor device according to the second embodiment of the invention.

FIG. 7 is a second sectional view illustrating the method for manufacturing the semiconductor device according to the second embodiment of the invention.

FIG. 8 is a third cross-sectional view illustrating the method for manufacturing the semiconductor device according to the second embodiment of the invention.

FIG. 9 is a fourth sectional view illustrating the method for manufacturing the semiconductor device according to the second embodiment of the invention.

FIG. 10 is a fifth sectional view illustrating the method for manufacturing the semiconductor device according to the second embodiment of the invention.

FIG. 11 is a first cross-sectional view illustrating the method for manufacturing the semiconductor device according to the conventional example.

FIG. 12 is a second cross-sectional view illustrating the method for manufacturing the semiconductor device according to the conventional example.

FIG. 13 is a third cross-sectional view illustrating the method for manufacturing the semiconductor device according to the conventional example.

FIG. 14 is a fourth cross-sectional view illustrating the method for manufacturing the semiconductor device according to the conventional example.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location H01L 21/316 21/336 9274-4M H01L 21/94 A 29/78 301 P

Claims (2)

[Claims] 1. An oxide film (1) is formed on a semiconductor substrate (11).
2), first nitride film (13), polysilicon layer (14)
And a step of sequentially forming the second nitride film (15), a resist film (16) is selectively formed on the second nitride film (15), and the resist film (16) is used as a mask to form the first film. Etching and removing the second nitride film (15), and the resist film (16) and the second nitride film (15)
Is used as a mask to implant an impurity of one conductivity type to form a one conductivity type impurity region layer (17) on the surface layer of the semiconductor substrate (11); and using the second nitride film (15) as a mask. Selectively oxidizing the polysilicon layer (14) to form a selective oxide film (18) on the one conductivity type impurity region layer (17); removing the second nitride film (15); A step of implanting an impurity of opposite conductivity type using the selective oxide film (18) as a mask to form an impurity region layer (19) of opposite conductivity type on the surface layer of the semiconductor substrate (11). Device manufacturing method. 2. An oxide film (2) is formed on a semiconductor substrate (21).
2), a step of sequentially forming a polysilicon layer (23) and a nitride film (24), and a resist film (25) is selectively formed on the nitride film (24) and the resist film (25) is used as a mask. , Nitride film (2
4) Etching / removing, and using the resist film (25) and the nitride film (24) as a mask, implanting an impurity of one conductivity type to form an impurity region of one conductivity type in a surface layer of the semiconductor substrate (21). Forming a layer (26), and using the nitride film (24) as a mask, the semiconductor substrate (2)
Polysilicon layer (23) to the extent that 1) is not oxidized
Selectively oxidizing the first conductive type impurity region layer (26) to form a selective oxide film (27), and removing the nitride film (24) to remove the selective oxide film (27).
Is used as a mask to implant an impurity of opposite conductivity type to form an impurity region layer of opposite conductivity type (28) on the surface layer of the semiconductor substrate (21).