JPH0428263A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To eliminate crystal defects from layers by a method wherein a first conductivity type epitaxial layer is formed on a second conductivity type impurity diffusion layer, and the first conductivity type epitaxial layer formed on a first bipolar transistor forming region is removed by oxidation. CONSTITUTION:An N<+>-type diffusion layer 18 is formed on the surface of a P-type semiconductor substrate 17, a P<+>-type epitaxial layer 19 is formed thereon, the surface of the layer 19 is oxidized to form an oxide film 20, and a nitride film 21 is formed thereon. After the films 20 and 21 are removed, an N-type epitaxial layer 24 low in N-type impurity concentration is formed. An isolating groove 25 is provided to a boundary between an NPN region and a PNP region, an isolating oxide film 26 is filled into the groove 25, and then P-type impurities are introduced into the N-type epitaxial layer 24 to form a P-type diffusion layer 27. At this point, as the layer 24 is low in impurity concentration, the layer 27 can be easily formed without inducing crystal defects even if P-type impurities are introduced.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is directed to the use of pnp type and npn type semiconductor substrates on the same semiconductor substrate.
The present invention relates to a method of manufacturing a semiconductor device including a type of bipolar transistor.

[Conventional technology]

FIG. 3 is a cross-sectional view of a semiconductor device in which conventional pnp, npn) transistors are mixed, and in the figure, pnpt npn
represent formation regions of a pnpt-transistor and an npn transistor, respectively, and are hereinafter referred to as a pnp region and an npn region.

As shown in the figure, an n-type diffusion layer 2 is formed on the surface of a p-type semiconductor substrate 1, a thin p++ buried layer 3 is formed on the n+-type diffused layer 2 in the pnp region, and an n-type diffusion layer 2 in the npn region is formed. An n-type epitaxial layer 4 is formed on the diffusion layer 2, and
A p-type diffusion layer 5 is formed on the p-type buried layer 3, and an npn,
1) Trench isolation oxide films 6 are formed in predetermined regions such as between np regions to provide isolation between elements.

Furthermore, an N layer for reducing contact resistance is connected to a part of the N type epitaxial layer 4 in the NPN region and is connected to the N type diffusion layer 2.
A type collector all 7 is formed, and a p type collector all 8 for contact resistance reduction connected to the p++ buried layer 3 is formed in a part of the p type diffusion layer 5 in the pnp region.

Then, a p-type intrinsic base layer 9 and an extrinsic base layer 10 are formed in the n-type epitaxial layer 4 of the npn region, and an n-type emitter layer 11 is formed in the intrinsic base layer 9. An n-type intrinsic base layer 12 and an external base layer 13 are formed on the type diffusion layer 2, and a p-type emitter layer 14 is formed in the intrinsic base layer 12.

By the way, 15 is a surface oxide film formed on the entire surface,
Contact holes are formed at predetermined positions in this oxide film 15, and electrodes 16 are connected to external base layers 1, 0, 13, . . . through each contact hole. Emitter layer 11.14. It is connected to collector all 7 and 8 respectively.

[Problem to be solved by the invention]

In the conventional case, p
In order to create the type buried layer 3, for example, if the p++ buried layer 3 is created by ion implantation, the p type impurity must be implanted at a concentration higher than the impurity concentration of the n type diffusion layer 2.
There is a problem in that the introduction of high concentration n-type impurities and high concentration p-type impurities tends to cause crystal defects, which can cause leakage and the like.

Therefore, in order to suppress such crystal defects, it is possible to reduce the amount of p-type impurity implanted. However, if the amount of implanted p-type impurities is reduced, the amount of n-type impurities in the n-type diffusion layer 2 is large, so that the buried layer 3 is effectively The amount of p-type impurity decreases, and as a result, the formed buried layer 3 has a high resistance, resulting in a disadvantage that the operating speed decreases.

In addition, the p++ buried layer 3 is not formed in the n+ type scattered layer 2,
It is also possible to form the p++ buried layer 3 separately from the n+ type diffused layer 2, but in this case, the n+ type diffused layer 2 is formed only in the npn region, and the p++ buried layer 3 is formed only in the pnp region. In order to do so, npn.

A photolithography process must be added for each pnp region, resulting in an increase in the number of processes.

The present invention was made to solve the above-mentioned problems, and an object of the present invention is to improve the characteristics of a semiconductor device without complicating the process.

[Means to solve the problem]

A semiconductor device manufacturing method according to the present invention includes a semiconductor device including a first bipolar transistor having a base layer of a first conductivity type and a second bipolar transistor having a base layer of a second conductivity type on the same semiconductor substrate. A semiconductor device manufacturing method for manufacturing a semiconductor device includes the steps of forming a highly concentrated impurity diffusion layer of a second conductivity type on a semiconductor substrate of a first conductivity type, and forming an epitaxial layer of a first conductivity type on the impurity diffusion layer. a step of stacking an oxide film and a nitride film on the epitaxial layer; forming an etching mask on the nitride film in the region where the second bipolar transistor is to be formed of the nitride film; a step of etching the nitride film and the oxide film in the formation region; a step of completely oxidizing the epitaxial layer in the formation region of the first bipolar transistor after removing the etching mask to form an oxide film; After removing the nitride film and the oxide film in the formation region of the second bipolar transistor and the oxide film in the formation region of the first bipolar transistor, the second bipolar transistor is formed on the entire surface.
forming a conductive type epitaxial layer;
- A step of isolating the formation region of the bipolar transistor and the formation region of the second bipolar transistor with an isolation oxide film.

[Effect]

In this invention, after the epitaxial layer of the first conductivity type is formed on the impurity diffusion layer of the second conductivity type, the epitaxial layer of the first conductivity type in the formation region of the first bipolar transistor is oxidized and then removed. Therefore, there is no need to implant impurities of both conductivity types into one layer at a high concentration as in the conventional case, and the generation of crystal defects is prevented and the operation speed does not decrease.

〔Example〕

1A to 1M show cross-sectional views of an embodiment of the method for manufacturing a semiconductor device of the present invention, and each step will be explained below.

However, in the following explanation, n pn+ pn p
Transistor is the first. The p-type and n-type correspond to the first and second bipolar transistors, respectively. Each corresponds to the second conductivity type.

First, as shown in FIG. 1A, an n-type diffusion layer 18, which is a high concentration impurity diffusion layer, is formed on the surface of a p-type semiconductor substrate 17, and then, as shown in FIG. 1B, an n+-type diffused layer 18 is formed.
(Upper pnp) A p-type epitaxial layer 19, which will become a buried collector layer for a transistor, is formed on the entire surface, and as shown in FIG. 1C, the surface of this p-type epitaxial layer 19 is oxidized to form a thin oxide film 20. Afterwards, a thin nitride film 21 is formed on this oxide film 20.

Next, as shown in FIG. 1D, in order to leave only the p-type epitaxial layer 19 in the pnp region, a resist 22 is formed only on the nitride film 21 in the pnp region by photolithography, and then a resist 22 is formed only on the nitride film 21 in the pnp region. As shown in Figure E, the resist 22
Using as an etching mask, the nitride film 21 and oxide film 20 in the npn region are removed by etching to expose the p-type epitaxial layer 19 in the npn region, and the resist 22 in the pnl) region is further removed as shown in FIG. 1F. do.

Then, as shown in FIG. 1G, a nitride film 2 is formed in the pnp region.
The entire surface is oxidized while leaving 1 and the oxide film 20. At this time, n
After completely oxidizing the p++ epitaxial layer 19 in the pn region to form an oxide film 23, and removing the nitride film 21 and both oxide films 20 and 23 as shown in FIG. Next, an n-type epitaxial layer 24 containing a low concentration of n-type impurities is formed to serve as the collector layer of the npn) transistor and the pnp) transistor.

Next, as shown in FIG. 1J, a separation groove 25 is formed at the boundary between the npn region and the pnp region, and the first
After filling the isolation trench 25 with the isolation oxide film 26 as shown in Figure K, the n-type of the pnp region is filled as shown in Figure 1L.
A p-type impurity is introduced into the epitaxial layer 24 to form a p-type diffusion layer 27.

At this time, since the impurity concentration of the n-type epitaxial layer 24 in the pnp region is low, even if p-type impurities are introduced, the p-type diffusion layer 27 can be easily formed without generating crystal defects.

After that, as shown in the figure, the first M is npn+pn in the same way as the normal bipolar transistor process.
n++ collectorol 28 and p in the f′ region, respectively.
After forming the type collector all 29, a p-type intrinsic base layer 30 and an extrinsic base layer 31 are formed in the n-type epitaxial layer 24 of the npn region, as shown in FIG. In addition to forming an n-type emitter layer 32, an n-type intrinsic base layer 33 and an extrinsic base layer 34 are formed in the p-type diffusion layer 27 of the pnp region, as shown in FIG. A p-type emitter layer is formed inside, a surface oxide film 36 is formed on the entire surface, contact holes are formed at predetermined positions, and electrodes 38 are connected to the external base layers 31, 34 . It is connected to the emitter layers 32 and 35 and the collector layers 28 and 29, respectively.

By the way, the sectional views of each manufacturing process in the portion surrounded by the broken line in FIG. 2 correspond to FIGS. 1A to 1M.

Therefore, after forming the p+ type epitaxial layer 19 on the n+ type scattering layer 18, the p+ type epitaxial layer 19 in the npn region is oxidized and then removed. There is no need to implant the second impurity of both conductivity types at a high concentration, and the generation of crystal defects can be prevented.

Note that in the above embodiment, the first. The second bipolar transistors are npn and pnp) transistors, respectively, and the first
．． Although the case where the second conductivity type is p type and n type has been explained, the first conductivity type is p type and n type. The second bipolar transistors are respectively pnp+npn transistors, and the first bipolar transistors are pnp+npn transistors. Second
The present invention can be similarly implemented even if the conductivity types are n-type and p-type, respectively.

〔Effect of the invention〕

As described above, according to the method for manufacturing a semiconductor device of the present invention, after the first conductivity type epitaxial layer is formed on the second conductivity type impurity diffusion layer, the first conductivity type epitaxial layer is formed on the first conductivity type impurity diffusion layer. Since the conductive type epitaxial layer is oxidized and then removed, there is no need to complicate the process as in the conventional method, and moreover, the first and second conductive layers are not included in one layer. It is not necessary to implant the second impurities of both conductivity types at a high concentration, it is possible to prevent the occurrence of crystal defects, and it is also possible to prevent a decrease in operating speed, thereby providing a semiconductor device with excellent characteristics. can.

[Brief explanation of the drawing]

1A to 1M are cross-sectional views of each manufacturing process of an embodiment of the method for manufacturing a semiconductor device of the present invention, and FIG.
FIG. 3 is a sectional view of a semiconductor device manufactured by the conventional manufacturing method. In the figure, 17 is a p-type semiconductor substrate, 18 is an n1-type diffusion layer, 19 is a p+ type epitaxial layer, 20.23 is an oxide film, 21 is a nitride film, 22 is a resist, 24 is an n-type epitaxial layer, and 26 is an isolation layer. This is an oxide film for use. Note that the same reference numerals in each figure indicate the same or corresponding parts. gu ■ ω -1 -1 Procedural amendment (voluntary) November 5, 1990

Claims (1)

[Claims] (1) A semiconductor device manufacturing method for manufacturing a semiconductor device including a first bipolar transistor having a first conductivity type base layer and a second bipolar transistor having a second conductivity type base layer on the same semiconductor substrate. forming a highly concentrated impurity diffusion layer of a second conductivity type on a semiconductor substrate of a first conductivity type; forming an epitaxial layer of a first conductivity type on the impurity diffusion layer; and forming an epitaxial layer on the epitaxial layer. forming an etching mask on the nitride film in the formation region of the second bipolar transistor of the nitride film, and stacking an oxide film and a nitride film in the formation region of the first bipolar transistor; etching an oxide film; after removing the etching mask, completely oxidizing the epitaxial layer in the formation region of the first bipolar transistor to form an oxide film; and etching the epitaxial layer in the formation region of the second bipolar transistor. forming an epitaxial layer of a second conductivity type on the entire surface after removing the remaining nitride film and the oxide film and the oxide film in the formation region of the first bipolar transistor; and forming the first bipolar transistor. area and said second
1. A method of manufacturing a semiconductor device, comprising the step of isolating a region in which a bipolar transistor is formed using an oxide film for isolation.