JPH01100948A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To decrease a width of a field oxide film for realizing a highly integrated semiconductor, IC, by selectively oxidizing a silicon carbide pattern with a mask resistive to oxidation so that the field oxide film thus formed has a part buried in a semiconductor substrate, said part having approximately vertical end faces. CONSTITUTION:Using a resist film pattern as a mask, an Si3N4 film 7, a CVD- SiO2 film 6 and an SiC layer 5 are patterned sequentially to provide first and second SiC layer patterns 5A and 5B. Then, using these SiC layer patterns 5A and 5B as a mask, an ordinary selective oxidation process is carried out. On the surface of an n-type collector region 3 thus exposed, a first Selectively oxidized film 8 is formed such that its bottom is rooted in the n-type collector region 3. This process can be performed without the selectively oxidized film 8 penetrating into the interface between the SiC layer, patterns 5A, 5B and the n-type collector region 3 like a bird's beak, and the end face E1 of the first selectively oxidized film 8 contacted with the lower regions of the SiC layer patterns 5A and 5B can be formed approximately vertical. Thus, the base region and the collector contact region can be designed in a small area without any margin and a highly integrated element can be realized.

Description

[Detailed Description of the Invention] [Table of Contents] Overview Industrial Field of Application Conventional Technology Problems to be Solved by the Invention Means for Solving the Problems Working Examples Figure) Schematic plan view of SICO5 structure (Figure 2) Process cross-sectional view of application example of the invention (Figure 3) Effects of the invention [Summary] A method for manufacturing a semiconductor device, especially a semiconductor device having an end face perpendicular to the substrate surface Regarding a method for forming a field oxide film by selective oxidation, the present invention provides a selective oxidation method that does not generate bird's beaks and can form a field oxide film having almost vertical end faces, thereby reducing the size and speed of bipolar transistors. A step of forming a silicon carbide layer on a semiconductor substrate by an epitaxial growth method, and a step of patterning the silicon carbide layer to form a silicon carbide pattern corresponding to a functional part formation region on the semiconductor substrate. and a step of performing selective oxidation using the silicon carbide pattern as a mask to form a field oxide film defining a functional part formation region on the semiconductor substrate surface.

[Industrial application field]

The present invention relates to a method of manufacturing a semiconductor device, and particularly to a method of forming a field oxide film having an end face perpendicular to a substrate surface by selective oxidation.

In semiconductor devices, a selective oxidation technique called the TOCOS method is widely used as a method for forming an insulating film for isolation between elements.

However, in the conventional selective oxidation technique using a silicon nitride (SiJa) film as an oxidation-resistant mask, there is a problem in that the isolation region width increases due to the occurrence of bird's beak degrees, leading to a corresponding decrease in the degree of integration.

On the other hand, in bibolar transistors, due to the desire for higher speed, the base region is surrounded by an oxide film to the bottom of the junction to reduce the junction capacitance between the base and the collector, and the oxide film is removed to form the emitter region. The so-called SICOSlC05 (side-ba
However, in the selective oxidation technique using the 5iJn film as an oxidation-resistant mask, the end face of the field oxide film that defines the base region by the bird's beak becomes a downwardly expanding slope; Therefore, there is a problem in that the distance between the active base region formed in the region where the field oxide film is removed and the base extraction electrode becomes long, and the effect of reducing the base resistance by the 5rcos structure described above is diminished.

Therefore, there is a need for a selective oxidation method that does not generate bird's beaks and can form a field oxide film having nearly vertical end faces.

[Conventional technology]

An oxide film isolated bipolar transistor in which a base region and a collector contact region are separated by a field oxide film formed by a conventional selective oxidation method is described below, for example.
It was formed by the method described with reference to Figures (a) to (e).

Referring to FIG. 4(a), for example, a p-type silicon substrate 51 is
selectively forming an n9-type buried layer 52 on the surface of the substrate, forming an n-type epitaxial 9937 layer 153 on the substrate,
An element isolation region 54 made of silicon dioxide (SiOg film is embedded at least in the upper part) is formed in the epitaxial silicon N 153 to form a U-groove structure (at least in the upper part) reaching into the silicon substrate 51 to form the n-type epitaxial silicon. A substrate to be processed is formed in which the layer 153 is defined and separated into an n-type collector region 53 having an n°-type buried layer 52 at the bottom, and this substrate is used to separate the layer 153 from the n-type collector region 53 of the substrate. An underlay oxide film 55 is formed by a normal thermal oxidation method or the like, and a first 5ilN film pattern 56^ corresponding to the base formation region, a second 5iJa film pattern 56^ corresponding to the collector contact formation region are formed on the underlay oxide film 55. A film pattern 56B is formed.

Referring to FIG. 4, the first and second 5isNa film patterns 56A and 56B are then used as masks to perform selective oxidation to define a base formation region 57 and a collector contact formation region 58 on the collector region 53. Thick selective membranes 59A, 59B, and 59C of about 5,000 layers are formed.

Here, thick selective oxide films 59A, 59B, 59C
On the end face of the first and second 5iJ4 film patterns 56A,
A bird's beak 60 is formed that bites into the lower part of 56B.

Refer to No. 4(C) Next, first and second 5iJa film patterns 56^, 56B
After removing the underlying oxide film 55 and forming a damage prevention insulating film 61 on the silicon exposed surface, selective oxide films 59A and 59B are formed through openings 63 of the resist film 62 formed on the substrate and shown by the chain lines. Using as a mask, boron (B) is selectively ion-implanted into the base formation region 57, and after removing the resist film 62, a prescribed heat treatment is performed to activate and redistribute the B, forming a p-type base region. 64
form.

FIG. 4 (see dl) Next, after removing the damage prevention insulating film 61, silicon dioxide D7 is deposited on the substrate by vapor phase growth (CVD).
(A Si(h) film 65 is formed, and the CVD-3iOz film 6
5. First, an emitter contact window 66 and a collector contact window 67 are formed, and arsenic (As''-) is selectively ion-implanted at a high concentration from these windows 66, 67, and then the same C is ion-implanted.
After forming a base contact window 68 in the VD-5iO1 film 61 and selectively implanting (B') ions at a high concentration from the contact window 68, the necessary heat treatment was performed and the implanted ^S' and B' by activating the n° type emitter region 69,
An n1 type collector contact region 70 and a p+ type base contact region 71 are formed.

Refer to FIG. 4(e), and on the contact windows 66, 67, 68, an emitter region 69, a collector contact region 70, a p+ type penis contact) 9! In this method, an emitter wiring 72, a collector wiring 73, and a base wiring 74 are formed to connect the area 71 to the area 71, respectively.

[Problem that the invention seeks to solve]

However, in the selective oxidation method using the 5iJa film as an oxidation-resistant mask, which has been used to form the conventional oxide film isolated bipolar transistor, as shown in FIG.
, 59C etc., 5ixNa pattern 56A, 56B
A bird's beak 60 is formed by digging deeply into the lower part of the base, corresponding to its thickness, and its end face is formed into a slope shape with the lower part widening.

And the base region 6 due to the infiltration of the bird's beak 60
Since the reduction in the area of 4 reduces the alignment margin of the emitter region 69 and the base contact region 71 with respect to the base region 64, it is necessary to design the base region 64 to have a wide area corresponding to the width of the bird's beak 60. However, a problem has arisen in that the area of the transistor increases accordingly and the degree of integration of the semiconductor TC using the bipolar transistor decreases.

In addition, as shown in FIGS. 4(a) to 4(a), the end faces of the selective oxide film 59A, 59tl, 59C, etc. are formed in a slope shape with the bottom part widened, so that the cross section of the main part in FIG. As shown in the figure, the upper part of the selective oxide film 59 is removed,
The base extraction electrode 75 is inserted from the side wall side of the active base region 64A from the p-type packed crystal silicon buried therein, for example.
When trying to derive the so-called 5ICO5 structure and thereby reduce the base resistance and increase the speed of the bipolar transistor, the distance d between the active base region 64A and the base extraction electrode 75 is large. However, there was a problem in that the base resistance became higher and higher speeds could not be achieved sufficiently. In FIG. 5, numeral 76 indicates a thermal oxide film of polycrystalline silicon, and other symbols indicate the same objects as in FIG. 4.

SUMMARY OF THE INVENTION An object of the present invention is to provide a selective oxidation method that does not cause bird's beaks and can form a field oxide film having substantially vertical end faces, thereby reducing the size and speed of bipolar transistors. .

[Means for solving problems]

The above problem is solved by the step of forming a silicon carbide layer on a semiconductor substrate by epitaxial growth means, and the step of patterning the silicon carbide layer to form a silicon carbide pattern that selectively covers the functional part forming area in the semiconductor substrate. Then, selective oxidation is performed using the silicon carbide pattern as an oxidation-resistant mask to define a functional part formation region on the surface of the semiconductor substrate, and an end face in contact with the functional part formation region of the portion that has cut into the semiconductor substrate is The problem is solved by a method of manufacturing a semiconductor device according to the present invention, which includes a step of forming a substantially vertical field oxide film.

[For production]

That is, in the present invention, a silicon carbide (SiC) layer heteroepitaxially grown on the semiconductor substrate is used as a material for an oxidation-resistant mask pattern during selective oxidation.

When selective oxidation was performed using the epitaxially grown SiC layer pattern as an oxidation-resistant mask, Si0
The thermally oxidized SiO□ film does not grow into the bottom of the layer pattern in a bird's beak shape, but instead grows into the semiconductor substrate, i.e., the end surface (side wall surface) of the selective oxide film in contact with the semiconductor substrate. has a substantially vertical cross-sectional shape downward from the edge of the SiC pattern.

Therefore, according to the present invention, it is possible to increase the integration density of a semiconductor IC by reducing the field oxide film width, and to increase the speed of a bipolar transistor by reducing the base resistance in the 5ICO5 structure.

〔Example〕

The present invention will be specifically explained below with reference to illustrated embodiments.

Fig. 1 1a) - (- is a process cross-sectional view of an example of the method of the present invention, Fig. 2 is a schematic plan view showing the main parts of a bipolar transistor with a 5 ICOS structure, Fig. 3 (a) - 弽) FIG. 2 is a schematic side sectional view showing an application example of the present invention.

Identical objects are indicated by the same reference numerals throughout the figures.

When applying the method of the present invention to form a bipolar transistor with a 5ICO5 structure, for example, the method shown in FIG.
The method shown with reference to the process cross-sectional diagrams al to (m) is used.

Referring to FIG. 1(a), as in the conventional case, for example, an n-type buried layer 2 is selectively formed on the surface of a p-type silicon substrate 1, an n-type epitaxial silicon N103 is formed on the substrate, and the epitaxial silicon layer 103 from its surface to silicon substrate 1
An element isolation region 4 is formed with a U-groove structure (at least the upper part is filled with 5iO1, etc.) reaching inside, and the epitaxial silicon layer 103 is formed into an n-type collector region 3 having an n0-type buried layer 2 at the bottom. A substrate to be processed that is separated in a defined manner is used. 'And in the method of the present invention, for example, 5i is added to the growth gas.
The exposed surface of the silicon substrate, that is, the collector region 3, is grown by heteroepitaxial growth using HC1+ and C3H1.
A SiC film with a thickness of about 500 to 1,500 layers is formed as a first oxidation-resistant film thereon, and a CCVD-3 inch film 6 with a thickness of about 2,000 layers is formed on the SiC layer 5 as a stress buffering film. On the 5TO film 6, a 0CiJn film 7 with a thickness of about 2,000 layers is formed as an etching stopper.

Refer to FIG. 1 (1)) Next, using a conventional resist film pattern (not shown) as a mask, the above-mentioned 5isN4 film is etched by reactive-on-etching (RIB) treatment using a required gas. , C.C.
The VD-5in film 6 and the SiC layer 5 are sequentially patterned, and the upper CVD-5iOz film 6 and Si3Nm film 7 are sequentially laminated to form first and second layers corresponding to the shape of the base region and the shape of the collector contact Hff region, respectively. SiC
N patterns 5A and 5B are formed.

Referring to FIG. 1(C), the bottom portion is n
Thickness of about 6000 people dug into mold collector area 3 0
A Sift film, that is, a first selective oxide film 8 is formed.

At this time, the SiC layer patterns 5A and 5B are made of SiC layers epitaxially grown on the lower silicon substrate, that is, the n-type collector fil 3.
A selective oxide film does not grow into the bird's beak at the interface between A and 5B and the n-type collector region 3 (SiC
The end surface et of the first selective oxide film 8 that contacts the lower regions of the layer patterns 5A and 5B is formed substantially vertically. Therefore, there is no need for a margin equivalent to the bird's beak width, so
The base region, the collector contact H1 region, etc. can be designed to have a narrow area without adding extra dimensions, and the device can be highly integrated.

Note that this is a step that corresponds to the gist of the present invention.

Refer to FIG. 1(d). Next, using the 5iJ4 film 7 on the second SiC layer patterns 5A and 5B as a mask, the first selective oxide film 8 is etched back to the extent that a thickness of about 3000 nm is left at the bottom. .

At this time, a height of 2
000 end faces E2 and E of the 0C type collector region 3,
appears. These end surfaces Et and E3 are substantially vertical end surfaces due to the feature that the interface between the silicon substrate and the selective oxide film according to the present invention is formed perpendicularly as described above. Forming the side wall surface of the base forming region vertically is extremely advantageous in bringing the base extraction electrode formed in contact with the side wall surface in the 5ICOS structure closer to the internal (active) base region.

Referring to FIG. 1 (el) Next, a polycrystalline silicon layer 109 having a thickness of about 4,000 yen, for example, is formed on the substrate by CVD to sufficiently fill the recesses between the protrusions of the collector region.

Referring to FIG. 1(f), the polycrystalline silicon layer 109 is then etched back until the 5iJn film 7 on the SiC layer patterns 5A and 5B is exposed. As a result, the concave portion of the collector region 3 having the first thermal oxide film 8 at the bottom is filled with the polycrystalline silicon layer 109 almost flatly.

Referring to FIG. 1, a film pattern IO having a thickness of about 1,000 layers is formed on the substrate through a normal vapor phase growth process and a patterning process to cover the base electrode forming area.

Referring to FIG. 1(h), the polycrystalline silicon layer 109 is selectively oxidized to the bottom using the 5iJ4 film pattern 10 as a mask, and a second selective oxide film 11 is formed to define the polycrystalline silicon pattern 9 that will become the base electrode. form.

Refer to FIG. 1(L) Next, the second selective oxide film 11 and the SiC layer patterns 5^, 5 in which the SiO□ film 6 and the 5tiNa film 7 are laminated are formed.
Using B as a mask, boron (B') ions are selectively implanted into the polycrystalline silicon pattern 9 at a high dose of about IQ "am-".

Refer to FIG. 1 U) Next, the polycrystalline silicon pattern 9 is selectively oxidized using the first SiC layer pattern 5A as a mask, and the surface of the polycrystalline silicon pattern 9 is thermally oxidized to a thickness of about 2000%.
iOtl! form 12. At this time, the thickness of the polycrystalline silicon pattern 9 is about 2000 mm, and the introduced B is activated and redistributed to become a p type packed crystal silicon base extraction electrode 99 having high conductivity. . Furthermore, a p-type external base region 13 is formed by solid-phase diffusion of boron from the p°-type polycrystalline silicon base extraction electrode 99.

Refer to Fig. 1) Then, the S
The iC layer patterns 5A and 5B are selectively removed to expose a first region surface 14A of the collector corresponding to the base formation region and a second region surface 14B of the collector corresponding to the collector contact formation region. 2 areas 14
B is covered with a resist film 15 and the first region 14A of the collector
B+ ions are selectively implanted into the region, and after removing the resist film 15, necessary heat treatment is performed to form a p-type internal base region 16 in this region.

Refer to Figure 1+1) Then apply a thickness of about 2000 to 0 heat VD- on the substrate.
A 5i01 film 17 is formed, and the next step is to form eleventh second and third contact windows 18A, 18B, and 18C penetrating the CVD-5iOt film 17 or the CVD-3iO□ film 17 and the thermally oxidized 5iOz film 12 below it. Then, for example, the third contact 18C is covered with a resist film 19, arsenic (As'') is ion-implanted at a high dose through the first and second contact windows 18A and 18B, and the resist film 19 is removed. Then, an activation heat treatment is performed to form an n'' emitter region 20 and an n'' collector contact region 21.

FIG. 2 is a plan view of the main part of the process completed. Each symbol indicates the same object as in FIG.

Referring to FIG. 1(B), a collector wiring 22 made of aluminum or the like, an emitter wiring 23,
The base wirings A24 are respectively formed, and a bipolar transistor with a 5 ICOS structure is completed by applying the method of the present invention.

Note that by modifying the above embodiment and performing the following steps, it is also possible to form a hetero bipolar transistor with a 5rcos structure that can achieve even higher speeds.

Refer to FIG. 3 18) That is, after completing the process shown in FIG. 1 01 of the above embodiment, the first
, 5iJa film 7 on second SiC patterns 5A, 5B
Then, using a resist mask (not shown), ions of B are selectively implanted through the second SiC pattern 5B, and the first SiC pattern 5A is removed.
As'' is ion-implanted selectively through the wafer, and an activation heat treatment is performed to form a p-type internal base region 16 and an n0-type collector contact region 25.

Referring to FIG. 3(b), a base contact window 26 is then formed in the thermally oxidized Si0g film 12 on the p-type packed crystal silicon base extraction electrode.
Next, the second SiC pattern 5B is selectively removed, and then the collector electrode 22 is formed on the n1 type collector contact region 25, and the emitter electrode 2 is formed on the first SiC pattern 5A.
3. Form base wirings 24 on base contact windows 26, respectively.

Here, since a heterojunction is formed between the first SiC pattern 5A and the p-type internal base region 16, the first SiC pattern 5A functions as an emitter, and a hetero bipolar transistor is formed. .

Note that the method of the present invention is of course effectively applied not only to the above-mentioned embodiments but also to ordinary planar type bipolar transistors and MIS type semiconductor devices as shown in the conventional example.

〔Effect of the invention〕

As explained in the examples above, according to the method of the present invention, when selectively oxidizing the surface of a silicon substrate,
A selective oxide film that is formed by cutting into the semiconductor substrate can be formed so that the side end surface in contact with the semiconductor substrate is substantially vertical without producing a bird's beak.

Therefore, when manufacturing a semiconductor device in which a semiconductor element or a functional head of a semiconductor element is defined by a selective oxide film, there is no need to allow for a margin corresponding to the bird's beak width in the area defined by the selective oxide film. The device can be highly integrated.

Furthermore, in a bipolar transistor with a 5ICO5 structure, the distance between the active base region and the base lead-out electrode can be reduced to reduce the base resistance, so that higher speeds can be achieved.

[Brief explanation of the drawing]

Figures 1+8) to (m) are process sectional views of an embodiment of the present invention, Figure 2 is a process plan view of an embodiment of the present invention, and Figure 3 (a)
) to crest) are process cross-sections showing application examples of the present invention. FIG. 5 is a cross-sectional view of the main part of a conventional 5ICOS structure. In the figure, 1 is a p-type silicon substrate, 2 is an n-type buried layer, 3 is an n-type collector region, 4 is an element isolation region, 5 is a SiC layer, 5A and 5B are SiC patterns, 6.17 is a CVD-5iOz film , 7 is a 5iJ4 film, 8 is a first selective oxide film, 9 is a polycrystalline silicon pattern, 10 is a 5iJa film pattern, 11 is a second selective oxide film, 12 is a thermally oxidized SiO□ film, 13 is a p-type external Base region, 14^ is the first region of the collector, 14B is the second region of the collector, 15.19 is the resist film, 20 is the n° type emitter region, 21 is the n° type collector contact region, 99 is p 109 is a polycrystalline silicon layer, El is an end surface of a selective oxide film, and Ez is a side wall surface of a base region.

Claims (1)

[Claims] A step of forming a silicon carbide layer on a semiconductor substrate by epitaxial growth means, and patterning the silicon carbide layer to form a silicon carbide pattern that selectively covers a functional part formation region in the semiconductor substrate. a step of performing selective oxidation using the silicon carbide pattern as an oxidation-resistant mask to define a functional part formation region on the surface of the semiconductor substrate; and forming a substantially vertical field oxide film.