JP2943855B2 - Method for manufacturing semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention mainly relates to a method for manufacturing a semiconductor device including a bipolar transistor.

[0002]

2. Description of the Related Art FIG. 5 shows a process flow of a conventional method for forming a buried region of a bipolar transistor in a semiconductor device. FIGS. 6A, 6B, and 6C are cross-sectional views of the semiconductor device in steps (f), (j), and (m) of the process flow of FIG. 5, respectively.
Shown in

Referring to FIGS. 5 and 6A to 6C, in a method for forming a buried region of a bipolar transistor, a thickness of about 5 mm is formed on p-type silicon substrate 21 by thermal oxidation.
A silicon oxide film 22 having a thickness of 2,000 ° is formed, and an opening for forming an n-type buried layer 24 is formed through a photolithography process and a wet etching process (steps (a) to (d) in FIG. 5).

Next, after removing the photoresist, a silica glass layer 23 containing arsenic, which is an n-type impurity, is formed on the entire surface, and arsenic ions are thermally diffused into the p-type silicon substrate 21 through the previously formed opening. Diffusion to form a high concentration n-type buried layer 24 (steps (e) to (f) in FIG. 5)
And FIG. 6 (A)).

After that, the silica glass layer 23 containing arsenic and the silicon oxide film 22 are removed, and a silicon oxide film 25 having a thickness of about 600 ° is formed again by thermal oxidation on the entire surface. A region for forming the layer 28 is opened, and a p-type buried layer 28 is formed by implanting boron ions 27 as a p-type impurity (steps (g) to (j) in FIG. 6 (B)).

Finally, after removing the photoresist 26 and the silicon oxide film 25, an n-type epitaxial layer 29 is formed.
(Steps (k) to (m) in FIG. 5 and FIG. 6C).

[0007]

In the prior art,
Since the n-type buried region and the p-type buried region are formed through separate lithography steps, extra steps such as applying a photoresist, patterning the buried region, and removing the photoresist are required. become. Further, an extra mask for patterning the buried region is required. As a result, there is a problem that the number of steps increases.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method of manufacturing a semiconductor device which can be formed by a single photolithography step, thereby reducing the number of steps.

[0009]

According to the present invention, a step of forming a silicon oxide film on a semiconductor substrate by thermal oxidation and a step of implanting boron ions as a p-type impurity to form a first semiconductor layer. A step of forming a photoresist by a photolithography step and selectively removing the first semiconductor layer in a region where an n-type buried layer is to be formed through a dry etching step; Implanting arsenic ions, which are n-type impurities, into the removed opening to form a second semiconductor layer, and removing the photoresist and the silicon oxide film after forming the first and second semiconductor layers Forming an n-type epitaxial layer containing impurities at a lower concentration than the buried region of the second semiconductor layer on the removed portion and on the second semiconductor layer. That the method of manufacturing a semiconductor device can be obtained.

According to the present invention, a step of forming a silicon oxide film on a semiconductor substrate by thermal oxidation, a step of implanting boron ions as a p-type impurity to form a first semiconductor layer, Forming a photoresist on the first semiconductor layer by a photolithography process, performing a dry etching process, and selectively removing the first semiconductor layer in a region where an n-type buried layer is to be formed, and using a hydrazine solution. The first semiconductor layer is etched to remove n from the opening and the etched portion where the first semiconductor layer is removed.
Forming a second semiconductor layer by implanting arsenic ions as a type impurity; removing the photoresist and the silicon oxide film after forming the first and second semiconductor layers; The second semiconductor layer is formed on the second semiconductor layer.
Forming an n-type epitaxial layer containing an impurity at a concentration lower than that of the semiconductor layer.
Method for manufacturing a device can be obtained.

[0011]

[0012]

After forming a first conductivity type layer on a semiconductor substrate, a second conductivity type layer is formed by selectively removing the first conductivity type layer by a photolithography step and an etching step. Is formed. Therefore, the first
Need not be formed in separate photolithography steps.

Therefore, the number of steps is reduced by one photolithography step. Further, a mask for patterning is not required for one process.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows a process flow of a first embodiment of a method of manufacturing a semiconductor device according to the present invention. 2A, FIG. 2B, and FIG. 2B are sectional views of steps (c), (f), and (i) of the process flow of FIG.
It is shown in (C).

Referring to FIGS. 1, 2 (A) and 2 (C),
In the method of manufacturing a semiconductor device according to the first embodiment of the present invention, a silicon oxide film 2 having a thickness of about 600 ° is formed on a p-type silicon substrate (semiconductor substrate) 1 by thermal oxidation, and then a p-type silicon substrate is formed. Boron ions 3 as impurities are implanted into the entire surface to form a high concentration p-type buried layer (first semiconductor layer) 4 (steps (a) to (c) in FIG. 1 and FIG. 2 (A)). ).

Next, a photoresist 5 is formed by a photolithography process, and after a dry etching process,
The p-type buried layer 4 in the region where the n-type buried layer is to be formed is selectively removed. Arsenic ions 6 as an n-type impurity are implanted into the opening from which the p-type buried layer 4 has been removed to form a high-concentration n-type buried layer (second semiconductor layer) 7 (step (FIG. 1)). d) to Step (f) and FIG. 2 (B)).

After forming the p-type buried layer 4 and the n-type buried layer 7, the photoresist 5 and the silicon oxide film 2 are removed, and the n-type buried layer 7 is formed on the removed portion and on the n-type buried layer 7. An n-type epitaxial layer 8 containing an impurity at a lower concentration than the region is formed (steps (g) to (i) in FIG. 1 and FIG. 2C).

Next, a method of manufacturing a semiconductor device according to a second embodiment of the present invention will be described with reference to the drawings.

FIG. 3 shows a process flow of the second embodiment of the present invention. 4A, FIG. 4B, and FIG. 4B are cross-sectional views of steps (c), (g), and (j) of the process flow of FIG.
It is shown in (C).

Referring to FIGS. 3, 4 (A) to 4 (C),
In the method of manufacturing a semiconductor device according to the second embodiment of the present invention, a silicon oxide film 12 having a thickness of about 600 ° is formed on a p-type silicon substrate (semiconductor substrate) 11 by thermal oxidation, and then a p-type silicon substrate is formed. A boron ion 13 as an impurity is implanted into the entire surface and a high concentration p-type buried layer (first semiconductor layer) 1 is formed.
4 (Steps (a) to (c) in FIG. 3)
And FIG. 4 (A)).

Next, a photoresist 15 is formed on the p-type buried layer 14 by a photolithography process, and after a dry etching process, a p-type buried layer (first The semiconductor layer 14 is selectively removed (steps (d) to (e) in FIG. 3). further,
In order to prevent the p-type buried layer 14 and the n-type buried layer 17 from hitting each other, the p-type buried layer 14 is laterally etched by about 1 μm using a hydrazine solution (step (f) in FIG. 3). Then, the arsenic ion 1 as an n-type impurity is formed in the opening where the p-type buried layer 14 is removed and the etched portion.
6 is implanted to form a high concentration n-type buried layer 17.
(G) and FIG. 4 (B)).

After forming the p-type buried layer 14 and the n-type buried layer 17, a photoresist 15 and a silicon oxide film 12 are formed.
Is removed, and an n-type epitaxial layer 18 containing impurities at a lower concentration than the n-type buried layer is formed on the removed portion and the n-type buried layer 17 (steps (h) to (j) in FIG. 3). And FIG. 4 (C)).

In this embodiment, after the p-type buried layer 14 is selectively removed by dry etching, side etching is performed using a hydrazine solution, so that the p-type buried layer 14 The layer 17 is prevented from hitting. Therefore, this manufacturing method can be used for products requiring high withstand voltage.

[0024]

As described above, according to the method of manufacturing a semiconductor device of the present invention, after a p-type buried layer is formed on the entire surface, an n-type buried layer is formed in a region where an n-type buried layer is to be formed. Since a certain p-type buried layer is selectively removed and an n-type buried layer is formed there, conventionally, to form an n-type buried layer and a p-type buried layer, two layers are used. It can be formed by one photolithography process, as compared with the case where one photography process is required.

As a result, the step of forming the buried region can be shortened by one photolithography step (about 10 steps in number) as compared with the conventional method. In addition, a mask for patterning is not required for one step, and the manufacturing cost of a semiconductor integrated circuit including a bipolar transistor can be reduced.

[Brief description of the drawings]

FIG. 1 is a flowchart showing a process flow of a first embodiment of a method for manufacturing a semiconductor device of the present invention.

2A is a cross-sectional view at step (c) in FIG. 1, FIG. 2B is a cross-sectional view at step (f) in FIG. 1,
(C) is a sectional view in step (i) of FIG. 1.

FIG. 3 is a flowchart showing a process flow of a second embodiment of a method of manufacturing a semiconductor device according to the present invention.

4A is a cross-sectional view at step (c) in FIG. 3, FIG. 4B is a cross-sectional view at step (g) in FIG.
FIG. 4C is a cross-sectional view of step (j) of FIG.

FIG. 5 is a flowchart showing a process flow of a conventional method for forming a buried region of a bipolar transistor.

6A is a cross-sectional view at step (f) in FIG. 5, FIG. 6B is a cross-sectional view at step (j) in FIG. 5,
(C) It is sectional drawing in the step (m) of FIG.

[Explanation of symbols]

 1,11,21 p-type silicon substrate 2,12,22,25 silicon oxide film 3,13,27 boron ion 4,14,28 p-type buried layer 5,15,26 photoresist 6,16 arsenic ion 7, 17, 24 n-type buried layer 8, 18, 29 n-type epitaxial layer 23 silica glass layer containing arsenic

Claims (2)

(57) [Claims] A step of forming a silicon oxide film on a semiconductor substrate by thermal oxidation; a step of implanting boron ions as a p-type impurity to form a first semiconductor layer; A step of selectively removing the first semiconductor layer in a region where an n-type buried layer is to be formed through a dry etching step; and an step of removing n-type impurities in the opening from which the first semiconductor layer is removed. Implanting arsenic ions to form a second semiconductor layer; removing the photoresist and the silicon oxide film after forming the first and second semiconductor layers, removing the removed portion and the second semiconductor layer; the method of manufacturing a semiconductor device <br/> which comprises a step of forming a n-type epitaxial layer containing an impurity of lower concentration than the buried region of the second semiconductor layer on the semiconductor layer. 2. A step of forming a silicon oxide film on a semiconductor substrate by thermal oxidation, a step of implanting boron ions as a p-type impurity to form a first semiconductor layer, and a step of forming a first semiconductor layer on the first semiconductor layer. Forming a photoresist by a photolithography step, selectively removing the first semiconductor layer in an area where an n-type buried layer is to be formed through a dry etching step, and using a hydrazine solution to remove the first semiconductor layer. Etching a layer, implanting arsenic ions, which are n-type impurities, into the opening where the first semiconductor layer is removed and the etched portion to form a second semiconductor layer; After the formation of the semiconductor layer, the photoresist and the silicon oxide film are removed, and an impurity containing a lower concentration of impurities than the second semiconductor layer is formed on the removed portion and the second semiconductor layer. The method of manufacturing a semiconductor device which comprises a step of forming a type epitaxial layer.