JPH0354831A - Semiconductor device and manufacture thereof - Google Patents

Abstract

PURPOSE:To manufacture a heterojunction bipolar transistor in high performances by a method wherein, within a semiconductor device having an emitter region in wider forbidden band width than that of a region, the semiconductor layer in the base region is composed of recrystallized thin film semiconductor. CONSTITUTION:An SiO2 film 101 is formed on an n/n<+> type Si substrate 100. Next, an opening corresponding to a base region is made in the SiO2 101 to form a film of p<+> type amorphous silicon (alpha-Si) 102 and successively n<+> amorphous SiC(alpha-SiC)103 to be a wide gap emitter is formed into a film. Next, the amorphous SiC 103 is patterned after an emitter region 105 to form a p-type recrystallized Si region 104 by annealing process. This region becomes a base region whose film thickness specifies a base width. Next, another SiO2 film 106 is made on the whole surface while contact holes are made by etching process finally to form pick-up electrodes 107-109.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a semiconductor device and a method for manufacturing the same. [Prior Art] A heterojunction bibolar transistor (hereinafter referred to as HBT) has a forbidden band width in an emitter region larger than a forbidden band width in a base region, thereby preventing carrier injection from the base to the emitter and at the same time Since the base resistance can be reduced by increasing the doping degree, the amplification factor and operating speed of the transistor can be increased. For this reason, the development of HBT has become active in recent years. For example, A as shown in "Electronic Materials J January 1987 issue pp.71
I G a As / G a As system H B T
SAPlied Physics Letters v
ol. 52 (10), pp. 822 (1988)
GaAs/Si HBT as shown in IE
KE Electron Device Letters
vol. 9 (4), 165 (1988)
, Applied Physics Letters
vol. 52 (11), pp. 895 (19
8B) etc., Si/Ge Si-based HBT, IEEE Electron Dev
ice Letters vol. 9 (2), 87
(1988) as shown in β-S i C/S
Prototypes of various HBTs such as i-type HBTs are being produced. [Problems to be Solved by the Invention] In compound semiconductor HBTs such as the AI G a A S/ G a A E3 type, molecular beam vapor deposition (MBE) and organometallic chemical vapor deposition are used to fabricate wide bandgap emitters. Since emitters with high crystallinity are fabricated using phase epitaxy (MOCVD), etc., it is possible to fabricate high-performance HBTs, but on the other hand, there are problems in that it is difficult to adapt to existing Si semiconductor processes and the fabrication equipment is expensive. It had on the other hand,
19B? 1EDM Technical Dige
st pp. 186-193, 1984 IED
M Technical Digest pp. There are also attempts to fabricate wide bandgap emitters using amorphous Si, amorphous SiC, or microcrystalline Si, as shown in No. 746 and others. In this trial, amorphous Si, amorphous SiC and microcrystalline S were used.
Since the plasma CVD method is used to manufacture the HBT, it is possible to manufacture the HBT at a relatively low cost. However, the above Si-based HBT
Since the base layer is fabricated by ion implantation, it is difficult to fabricate a highly doped base layer with shallow junctions, which has been an obstacle to achieving higher performance.

The present invention solves the above problems, and its purpose is to provide a low-cost, high-performance HBT. [Means for Solving the Problems] The semiconductor device of the present invention has an emitter region, a base region, and a collector region, and the emitter region has a larger forbidden band width than the base region. The semiconductor layer is composed of a recrystallized thin film semiconductor. The method for manufacturing a semiconductor device of the present invention is characterized in that: (1) the thin film semiconductor is recrystallized by solid phase growth using annealing; (2) The thin film semiconductor is characterized in that it is a thin film and impurities are sometimes introduced. (3) The solid phase growth annealing is performed in a state where the emitter region and the base region are laminated. (4) The thin film semiconductor is characterized in that it is formed by a plasma chemical vapor deposition method or a low pressure chemical vapor deposition method. [Example] Hereinafter, based on FIG. 1, the semiconductor device of the present invention will be described. The manufacturing method will be explained. In the present invention, the manufacturing method of an npn type HBT will be explained as an example. First, the surface of a 7 Ω cm (111) n/n'' type Si substrate 100 is thermally oxidized to form a SiO2 film 101 ( Figure 1-(a)). SiO2 at the location corresponding to the base region
The film is removed by photo-etching to form an opening (Figure 1-(b)). On top of this, plasma chemical vapor deposition (P
CVD) p" type amorphous silicon (a-Si) 102 is deposited by approximately 500 to 700 people, and then the deposition gas is changed to deposit n" type amorphous SiC, which will become a wide bandgap emitter.
(a-SiC) 103 is deposited to a thickness of about 500 to IOOOA (Fig. 1-(c)). A mixed gas of SiHa and B2H6 was used as the film forming gas for p-type a-Si 102, and n″
The film forming gas for type a-SiC 103 contains SiH4, CH
A mixed gas of J and PH3 was used. The gas flow rate ratio was adjusted so that the doping degree of B and P atoms was high doping of 1 × 10111 or more, a-S.
A high frequency of 13.56 MHz was applied to both the i and a-SiC layers, and the high frequency power was 30 mW/cm2.
, the substrate temperature is 180-250°C. The board temperature is 4
If the a-Si film is formed at 50°C or higher, the hydrogen content in the film decreases, so there is no need for the briane annealing described below, but it is better to perform the briane annealing to promote film densification. desirable. In addition to a-SiC, amorphous silicon nitride (
a-SiN), microcrystalline Si (μc-Si), etc. can also be used. For a-SiN film formation, SiHa, N20
(or N2, NH3, etc.) mixed gas is used. P H 3 is used as the doping gas. To form a μc-Si film, SiH4 gas was diluted with H2 gas and the power was 300mW.
/cm' high frequency power is applied. PH3 is used as the doping gas in this case as well, and in the case of PCVD, a-
If H2 plasma or Ar plasma treatment is performed immediately before Si film formation, cleaning of the substrate surface and film formation can be performed continuously.
It is also possible to use PGVD. In the case of LPCVD, conditions are suitable where the substrate temperature is as low as possible and the film formation rate is as fast as possible. S i H 4 in the raw material gas of a-Si
When using Si2Hs, the temperature is preferably 500 to 560°C, and when using Si2Hs, the temperature is preferably 300 to 500°C. If the substrate temperature becomes higher than this, the deposited film will become polycrystalline, which will impede solid-phase growth, which is undesirable. B2H6 is used as the doping gas as in PCVD. Then, after batting the p″a-Si into the shape of the base region,
The n″a-SiC is battened into the shape of the emitter region 105 (FIG. 1-(d)). In this state, the substrate is annealed in N2 at 450° C. for 30 min.
The hydrogen in the film is removed and at the same time the film is made denser. 8-72 in N2 at 500-600℃ after Briannealing
The a-Si film is grown in solid phase by time annealing and recrystallized (Fig. 1(e)). A suitable annealing device is a furnace annealing using a quartz tube.

In addition to N2, the annealing atmosphere contains H2, Ar, H
e etc. are desirable, but 1xlO-'~lxlo Ichimoku Tor
Annealing may be performed in a high vacuum of about r. At the initial stage of solid phase growth, the Si substrate is used as a seed, and a
- Proceeds in the vertical direction of the Si film, but the recrystallized region is SiO2
Once it reaches the membrane, lateral solid-phase growth progresses. In this way, a p-type recrystallized Si region 104 is formed. This region becomes a base region, and its film thickness becomes the base width. A SiO2 film is formed on this by LPCVD, and then a contact hole is formed by etching. Finally, extraction electrodes 107 to 109 are formed and patterned to complete the process (FIG. 1-(f)). Electrode materials include A1, Al-Si
-Cu. Metals such as Au and 'ri are used. As described above, according to the method for manufacturing a semiconductor device of the present invention, since doped a-Si is grown in solid phase at a low temperature of 500 to 600°C, an extremely steep impurity concentration distribution can be achieved despite the thin base width of about 700A. It becomes possible to realize a base-collector junction with a The junction depth of the base layer is determined by the thickness of the p-type a-Si thin film, and the impurity concentration in the base is determined by the doping gas flow rate during film formation, so it is much simpler and M denser than the ion implantation method. It is possible to control the degree of soaking in the base and the depth of base bonding. The activation rate of impurity atoms is almost 100% when solid phase growth is completed. Furthermore, PCVD,L
Since both PCVD methods can uniformly form an a-Si film over a large area, the throughput can also be dramatically increased.

In addition, when using the PCVD method, a-Si and a-SiC
Since the (a-SiN, μc-Si) films can be formed continuously, a good base-emitter heterointerface can be easily achieved. Although this example has been explained using an npn transistor as an example, it goes without saying that a pnp type transistor can also be manufactured in the same way by using a p/p'' type wafer or p well structure on the Si substrate. , limited to Si-based semiconductors such as Ge.Si-Ge, GaAs, InAs
It can also be applied to compound semiconductor processes such as [Effects of the Invention] According to the present invention, it is possible to easily realize a base-collector junction that has a very steep base immersion distribution even though the base thickness is shallow. Therefore, it is possible to fabricate an HBT with an ideal thin base thickness and high base temperature, making a tremendous contribution to improving the performance and lowering the cost of HBTs. This process is similar to the conventional S
It is highly compatible with the i-semiconductor process, so it can be used not only for HBTs but also for MOS type transistors, Bi-CMOSICs,
It can be applied to general semiconductor devices such as phototransistors and thyristors.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the manufacturing process of the semiconductor device of the present invention. 10
0......n/r1'' Si substrate 101
......Thermal oxidation Sio2 film 102...
・・・・p″a-Si film O3・・・・・・・・・n”a
-SiC film 04・・・・・・・・・p゛Recrystallized SiO
5......Emitter region 0 6......LPCVD O7...Base electrode 08...Emitter electrode 09.・・・・・・Collector electrode SiO2 film or more

Claims (5)

[Claims] (1) In a semiconductor device that has an emitter region, a base region, and a collector region, and the forbidden band width of the emitter region is larger than the forbidden band width of the base region, the semiconductor layer in the base region is composed of a recrystallized thin film semiconductor. A semiconductor device characterized by: (2) The method of manufacturing a semiconductor device according to claim 1, wherein the thin film semiconductor is recrystallized by solid phase growth using annealing. (3) The method of manufacturing a semiconductor device according to claim 1, wherein impurities are introduced into the thin film semiconductor during formation of the thin film. (4) The method of manufacturing a semiconductor device according to claim 1, wherein the solid phase growth annealing is performed in a state where the emitter region and the base region are stacked. (5) The method for manufacturing a semiconductor device according to claim 1, wherein the thin film semiconductor is formed by plasma chemical vapor deposition or low pressure chemical vapor deposition.