JPH063807B2 - Semiconductor device and manufacturing method thereof - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a semiconductor device and a method for manufacturing the same, and particularly to a silicon bipolar transistor and a method for manufacturing the same.

[Conventional technology]

In order to speed up and miniaturize the bipolar transistor,
It is well known that a so-called wide-gap emitter structure, which uses a material having a wider bandgap than the base layer in the emitter region, is effective because it increases the injection efficiency.

In a silicon bipolar transistor, an oxygen-doped single crystal film (SIPO) is used as a wide gap emitter material.
S) is famous (Matsushita, Semiconductor Research, Vol. 18, pp. 7-5).
(Page 0, Published by Industrial Research Society, edited by Semiconductor Research Promotion Association).

Also, in the silicon molecular beam epitaxial (MBE) growth, the substrate temperature is set to 67 in an oxygen atmosphere of 10 ⁻⁶ to 10 ⁻⁵ Torr.
It has already been reported that a single crystal silicon film containing 20 to 30 at% oxygen atoms is formed when the growth is carried out while maintaining the temperature at around 0 ° C. This oxygen-doped silicon single crystal film (hereinafter referred to as OX
SIS) has a bandgap wider than that of silicon similarly to the above-mentioned SIPOS, and can be expected to be used as a wide-gap emitter material in a silicon bipolar transistor.

[Problems to be solved by the invention]

However, since the former SIPOS is polycrystal, many interface states exist at the junction with the base portion made of single crystal silicon, and a sufficient recombination current is generated due to the generated recombination current through the level. No gain. Further, since it is a polycrystal, there is a drawback that carriers are heavily scattered at grain boundaries and low resistance cannot be obtained.

On the other hand, in the latter OXSIS, since the junction with the base is a junction between single crystals, the interface state is small and a high emitter injection efficiency can be obtained, and the carrier scattering due to the disorder of the crystal is smaller than that in the polycrystal. As a result, low resistance can be obtained. However, when OXSIS is left in the atmosphere, a large amount of oxygen invades from the surface, and the natural oxide film (50) is much thicker than that of single crystal silicon (10-20Å).
It became clear that ~ 100Å) was formed. As the emitter electrode, a metal such as Al may be formed directly on the emitter by vapor deposition, or a metal layer may be formed via a polycrystalline silicon layer formed by vapor phase growth. It is necessary to take the sample into the atmosphere. Therefore, when the OXSIS film is used as the emitter, a thick natural oxide film is formed at the interface between the emitter and the emitter electrode, and the series resistance of the emitter is significantly increased.

[Means for solving problems]

The semiconductor device of the present invention has been made in view of the above problems, and in a silicon bipolar transistor, an emitter layer has an oxygen-doped silicon single crystal layer formed by epitaxial growth as a lowermost layer, and a silicon single layer formed by epitaxial growth. It has a multilayer structure with the crystal layer as the uppermost layer.

Further, the manufacturing method of the present invention comprises a step of epitaxially growing an oxygen-doped silicon single crystal layer on the base layer and a step of epitaxially growing single-crystal silicon on the oxygen-doped silicon single crystal without taking it out into the atmosphere. Is formed.

[Action]

Compared with the wide-gap emitter structure using SIPOS, since the lower layer film that is joined to the base is a single crystal, the interface state is small and the resistance is low at the junction with the base.
Further, when the emitter electrode is formed, the emitter is exposed to the atmosphere, but the upper-layer single crystal silicon forming the emitter serves to prevent the invasion of oxygen, so that the high resistance layer formed of the natural oxide film is not formed.

〔Example〕

 Hereinafter, the present invention will be described in detail with reference to Examples.

FIG. 1 is a sectional structural view showing an embodiment of the present invention, and shows an example in which an emitter structure is characterized based on a conventional npn transistor. 1 is a p-type substrate, 2 is an n ⁺ collector buried layer, 3 is an n collector layer, 4 is a p ⁺ base compensation region, 5 is a p base layer, 6 is an oxygen-doped silicon single crystal layer which is a part of an emitter, 7 Is also an n ⁺ silicon single crystal layer which is also a part of the emitter, 8 is an emitter extraction electrode made of a metal such as A1 or n ⁺ polycrystalline silicon, 9 is a base extraction electrode made of a metal such as A1 or p ⁺ polycrystalline silicon Reference numeral 10 is a separating insulator such as sio ₂ . However, the oxygen-doped silicon single crystal layer 6 used in this example has a lower temperature (400 to 6) than that of OXSIS described above.
It was formed at 00 ° C.
Call S. The method of forming the LOXSIS layer will be described later.

FIG. 2 is an enlarged view of the vicinity of the emitter of FIG.
a is a polycrystallized region of the oxygen-doped silicon film near the insulator 10, and 7a is a polycrystallized region of the Si film on 6a.

With such a structure, the junction between the base 5 and the LOXSIS layer 6, which is a part of the emitter, is a junction between single crystals having the same crystal structure, and the interface state density is extremely low. In addition, since LOXSIS has an oxygen content of several at% or more, it has a wider bandgap than silicon, and hole injection from the base 5 to the LOXSIS layer 6 side is suppressed, resulting in high emitter injection efficiency and high current amplification. The rate h _FE is obtained. LOXSIS has a smaller oxygen content and thus a smaller bandgap than sio ₂ having a bandgap of about 8 eV. However, if the oxygen content is several at% or more, the band gap can be several tens of meV or more wider than the silicon band gap of 1.11 eV, and sufficiently high emitter injection efficiency can be obtained.

Also, the emitter resistance that reduces the operating speed of the transistor and increases the amount of heat generation is required to be as small as possible. However, in this structure, the LOXSIS layer 6 is a single crystal and the single crystal silicon cap of the layer 7 LO
Since the formation of the high resistance layer on the surface of the XSIS layer 6 can be prevented, the emitter resistance can be made sufficiently small. An extremely thin (about 20 Å) natural oxide film is formed on the surface of the single crystal silicon cap 7 when the electrode 8 is formed, but this is on the surface of the LOXSIS film 6 without the cap (silicon single crystal layer 7). It is much thinner than the oxide film to be formed, and the emitter resistance can be kept at a sufficiently small value for transistor operation.

In FIG. 2, although it is formed by the influence of the polycrystalline or amorphous insulator 10 of 6a and 7a, it does not spread to the joint with the base 5 and the interface level is not increased. Does not happen. Most of the emitter electrodes are LOXSIS.
The polycrystalline regions 6a and 7a hardly contribute to the increase of the emitter resistance because they flow in the low resistance portion which is the central portion of the layer 6 and the single crystal silicon layer 7.

FIG. 3 is a cross-sectional configuration diagram showing a second embodiment of the present invention, which is a fine and high-speed npn type SST transistor structure (Sakai et al., IEDM “International”).
This is an example based on the "Electrode Device Meeting" technical digest, 1985 2.1). In the figure, reference numerals 1 to 10 are the same as those in FIG.
Reference numerals 6a and 7a are the same as the second. Reference numeral 8a is n ⁺ polycrystalline silicon, 11 is p ⁺ polycrystalline silicon, and 12 is a Si ₃ N ₄ film. The characteristics of the emitter portion are the same as those of the first embodiment, but the SST that enables high-speed operation of the entire transistor
Since it is based on a transistor, it can operate at a higher speed than in the first embodiment.

As described above, the emitter structure characterizing the present invention can be applied to various types of silicon bipolar transistors, and can be applied to a mesa type transistor and the like other than the above two embodiments. Also, FIGS. 1 to 3
In the figure, the joint surface between the LOXSIS layer 6 and the base 5 is exactly
The case where it coincides with the n ⁺ p junction surface is shown, but the same effect can be expected even if the n ⁺ impurity is pushed slightly downward (to the side of the base 5) due to heat dissipation diffusion or the like.

FIG. 4 is a diagram for explaining the manufacturing process of the emitter portion in the first and second embodiments. Reference numerals 1 to 7 in the figure indicate the same parts as the reference numerals in FIG.
In this example, the molecular beam epitaxy (MBE) method is used.
As in (a), the substrate is heated to 800 to 900 ° C. in a high vacuum to clean the surface of the base layer. Then, as shown in FIG. 6B, a LOXSIS film 6 having a thickness of about 1000 Å is deposited. As the growth conditions at this time, a partial pressure of O ₂ gas introduced into the growth chamber is about 10 ⁻⁶ Torr, a substrate temperature is 400 to 600 ° C., and a deposition rate of silicon is about 1 Å / sec. Then, the O ₂ gas was exhausted to the outside of the system without taking out this sample into the atmosphere, and then the single crystal silicon film 7 was grown to about 100 to 200 Å at the substrate temperature (400 to 600 ° C.), for example. (c)). The LOXSIS film 6 and the single crystal silicon film 7
In order to make the two-layered film made of n ⁺ into n ⁺ , n-type impurities such as antimony are subjected to molecular beam doping or ion doping during growth, or polycrystalline silicon n-type impurities deposited further on top after growth are ion-implanted, Doping may be performed by thermal diffusion using the polycrystalline silicon as a diffusion source.

As described above, in the present manufacturing method, since the single crystal silicon cap 7 is formed in the same apparatus after the LOXSIS film 6 is formed, even if the sample is taken out into the atmosphere and the electrode formation process is performed thereafter, the single crystal is formed. L generated when the surface of the silicon cap is only slightly oxidized and there is no cap
It is possible to prevent the formation of a thick oxide layer of 50 Å or more on the surface of the OXSIS film.

In this embodiment, the oxygen-doped silicon single crystal film 6 is a LOXSIS film having an interface state density and a resistance value lower than that of OXSIS, but an OXSIS film may be used instead. The lower interface state density and resistance value of LOXSIS than that of OXSIS are mainly due to the lower growth temperature of the film. That is, since the growth temperature of the LOXSIS film is 400 to 600 ° C, the vaporization reaction of SiO is suppressed as compared with the OXSIS film grown at about 670 ° C, and the vacancy formed in the film based on SiO. The number of holes can be significantly reduced. More specifically, at a high growth temperature of about 670 ° C. such as the formation of an OXSIS film, oxygen atoms are taken into the growing silicon film, and at the same time, silicon atoms on the surface form oxygen atoms attached in the vicinity. While a phenomenon in which volatile SiO molecules are formed and vaporized occurs, in the formation of the LOXSIS film, since the growth temperature is relatively low, SiO molecules are hard to be formed. If the voids can be reduced to form a dense film, the interface state at the bonding surface with the base can be reduced, and the resistance can be suppressed low.

Although the MBE method was used as the film deposition method in this embodiment, a CV method using SiH ₄ , Si ₂ H ₆ , SiH ₂ Cl ₂ , SiCl ₄ or the like is used.
The D method may be used.

Further, if the uppermost layer is a single crystal silicon film, the lower layer may have a multilayer structure composed of oxygen-doped silicon single crystal and single crystal silicon. For example, if a single crystal silicon layer is inserted in the middle of the oxygen-doped silicon single crystal layer, it becomes easy to form an oxygen-doped silicon single crystal layer having good single crystallinity.

〔The invention's effect〕

As described above, according to the semiconductor device and the method of manufacturing the same of the present invention, since the oxygen-doped silicon single crystal layer is used for the emitter, compared with the case where the oxygen-doped silicon polycrystalline layer is used, the junction with the base is formed. Since the interface state is low and a large injection efficiency can be obtained, and the scattering of carriers is small, the resistance can be lowered. Furthermore, since the emitter structure is a multi-layer structure in which a single crystal silicon cap layer is arranged on an oxygen-doped silicon polycrystal layer, a high resistance layer formed by a natural oxide film is formed on the surface of the oxygen-doped silicon single crystal film when the emitter electrode is formed. It is not formed and the emitter series resistance can be made very low.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention, FIG. 2 is an enlarged view of the vicinity of the emitter of FIG. 1, and FIG. 3 is a second view of the present invention.
4 is an explanatory sectional view showing the embodiment of FIG. 4, and FIG. 4 is an explanatory view of the manufacturing method of the present invention. 1 ... p type substrate, 2 ... n ⁺ collector layer, 3 ... n collector layer, 4
… P ⁺ base layer, 5… p base layer, 6… n ⁺ LOXSIS
Layer, 7 ... n ⁺ silicon single crystal layer, 8 ... Emitter extraction electrode, 9 ... Base extraction electrode, 10 ... Isolation insulator.

Claims (2)

[Claims] 1. An emitter layer, which is located on a base layer made of single crystal silicon on a collector layer made of single crystal silicon, is formed by epitaxial growth with an oxygen-doped silicon single crystal layer formed by epitaxial growth as a lowermost layer. A semiconductor device having a multi-layer structure in which the formed silicon single crystal layer is the uppermost layer. 2. A method of manufacturing a semiconductor device, wherein an emitter layer is formed on a base layer made of single crystal silicon on a collector layer made of single crystal silicon, a step of epitaxially growing an oxygen-doped silicon single crystal layer, and an atmosphere. A method of manufacturing a semiconductor device, wherein an emitter layer is formed by a step of epitaxially growing single crystal silicon on the oxygen-doped silicon single crystal without taking it out.