JPH04291729A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To provide a forming method for emitter and base layers of an ultrahigh speed bipolar Tr particularly necessary for a shallow junction in the method for forming a shallow diffused layer. CONSTITUTION:This invention has a step of reacting oxide of B, P, As of n-type and P-type impurities as coating diffusion sources with organic polymer to be polymerized, dissolving it in an alcoholic organic solvent, and coating a silicon substrate therewith; a step of baking it in an oxygen atmosphere at 200 deg.C or lower diffusing temperature to form an impurity layer (e.g. B2O3), and a step of diffusing it in a low temperature region at 900 deg.C or lower for several seconds - several tens min, are provided. A distribution depth is eliminated at a diffusion starting point due to a low temperature diffusion from the diffusion source, and hence possibility of shallow junction is high as well. This method is used for forming an emitter and a base of a bipolar transistor to desire to remarkably improve performance and yield of the transistor.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming shallow diffusion layers, and more particularly to a method for forming emitter and base layers of ultrafast bipolar transistors requiring shallow junctions.

0002

2. Description of the Related Art Conventionally, thermal diffusion and ion implantation are well known methods for introducing dopants into semiconductors. However, for large diameter wafers of 5 inches or more, the thermal diffusion method has poor in-plane uniformity of the wafer, and the ion implantation method has become mainstream.

[0003] Generally speaking, in the case of boron, for example, B +
A method of implanting heavier BF2 + ions at a low acceleration voltage and a method of implanting Si+ or Ge+ ions in advance
Research has been conducted on a method in which ions are implanted to make the surface of a silicon substrate amorphous, and then implanted at a low acceleration voltage.

Furthermore, other methods include plasma doping, in which a plasma containing a dopant is created, the dopant ions generated in the plasma are drawn out using an ion sheath, etc., and implanted into a silicon substrate; is irradiated with an excimer laser, the B2 H6 adsorbed on the surface is decomposed by the laser light, and
An excimer laser doping method in which the surface of a molten silicon substrate is doped has been studied.

[0005]

[Problems to be Solved by the Invention] In the ion implantation method, which is the conventional method for forming shallow junctions, in order to activate the introduced impurity ions and recover damage during ion implantation,
A high temperature anneal after implantation is essential. This annealing makes it impossible to form an extremely shallow diffusion layer of 0.1 μm or less. Furthermore, if the high temperature annealing is insufficient and the damage is not recovered, there is a problem that characteristics may deteriorate due to the generation of leakage current. Furthermore, lowering the acceleration voltage for ion implantation causes deterioration of in-plane doping uniformity.

Furthermore, although plasma doping and excimer laser doping are capable of forming extremely shallow diffusion layers, it is difficult to independently control the doping depth (Xj) and surface concentration (Ns). At present, there are many problems such as poor in-plane doping uniformity, high surface concentration, and poor controllability.

[0007]

[Means for Solving the Problems] The shallow junction forming method of the present invention uses oxides of B, P, and As (for example, B2 O3, P
2 O5, etc.) with an organic polymer and dissolved in an alcoholic solvent, the process of applying the polymer onto a silicon substrate, followed by baking in an oxygen atmosphere at a temperature of 200°C or higher and lower than the diffusion temperature. and the impurity layer (B2O
3 etc.) and a step of performing diffusion at a low temperature of 850° C. or lower for several seconds to several tens of minutes.

[0008]

[Example] Next, as an example of the present invention, an example using a coating diffusion source containing boron as an impurity (for example, poly boron film (PBF) manufactured by Tokyo Ohka Co., Ltd.) will be described with reference to a cross-sectional view. explain.

First, an n-type silicon substrate of about 10 Ωcm is oxidized to form a silicon oxide film (SiO2) on the surface, and then the SiO2 film is patterned by photolithography (FIG. 1(A)). Next, PBF, which is a coating diffusion source, is coated onto the wafer using a spinner (
Figure 1(B)). At this time, the alcohol-based organic solvent is scattered. Next, the temperature is 200°C or higher and lower than the diffusion temperature (for example, 6°C).
All organic matter is converted to carbon dioxide (C
It decomposes into water (H2O) and water (H2O), and a boron oxide (B2O3) film is formed afterwards (FIG. 1(C)). Next, after purging the same furnace to a nitrogen atmosphere, the temperature is raised to a predetermined diffusion temperature using a temperature controller, and diffusion is performed for several minutes to several tens of minutes (FIG. 1(D)). At this time, as shown in FIG. 2, the total flow rate of nitrogen needs to be 400 l/H or more. Finally, after the temperature has dropped to around 600℃, it is removed from the furnace.
The boron glass layer is removed using a mixed solution of pure water and hydrofluoric acid (FIG. 1(E)).

By adding the above steps to the normal bipolar transistor manufacturing process, an extremely shallow base layer as shown in FIG. 3 can be formed.

As another embodiment, FIG. 1(C) of the previous embodiment
After firing, SiO is removed from the furnace and immediately deposited on the B2 O3 film by atmospheric pressure chemical vapor deposition (hereinafter referred to as atmospheric CVD).
2 Deposit the film. Next, after cleaning the wafer, diffusion is performed for a short period of several seconds to several tens of seconds using a lamp annealing device. As a result, a much shallower diffusion layer can be formed than in the previous example.

0012

As explained above, since the present invention uses substantially the same components as photoresist, it can cope with increasing the diameter of wafers in the same way as ion implantation, and has a high throughput. Moreover, since it is a 100% B2 O3 film after firing,
There is no need to consider the concentration distribution in the impurity diffusion source, the segregation coefficient, etc., and the process parameters can be simplified accordingly. In addition, the influence of non-uniformity of the coating film thickness on doping uniformity is small, and damage unlike ion implantation does not occur.

In addition, because of the low-temperature heating diffusion from the coating diffusion source, there is no depth of distribution at the time of starting the diffusion, and the possibility of forming a shallow junction is higher.

By utilizing the above-mentioned advantages in forming the emitter and base of a bipolar transistor, a dramatic improvement in transistor performance and yield can be expected.

[Brief explanation of the drawing]

FIG. 1 is a process sectional view showing an embodiment of the present invention.

FIG. 2 shows dependence on nitrogen total flow rate when the present invention is implemented.

FIG. 3 is an impurity concentration distribution obtained by SIMS analysis during implementation of the present invention.

[Explanation of symbols]

1 N-type silicon substrate (10Ωcm or more) 2
Thermal silicon oxide film (SiO2) 3 Alcohol-based organic solvent 4 Poly boron film after coating 5
Carbon dioxide during firing 6 Moisture during firing 7 Boron glass layer after diffusion (B2 O3) 8
P-type ultra-shallow diffusion layer

Claims (3)

[Claims] [Claim 1] A step of applying a coating diffusion source onto a silicon substrate, and then baking in an oxygen atmosphere of several percent to 100% at a temperature of 200° C. or higher and lower than the diffusion temperature to form an impurity layer (for example, B2 O3). 1. A method for manufacturing a semiconductor device, comprising: a step of diffusing at a low temperature of 900° C. or less for several seconds to several tens of minutes. 2. As the coating diffusion source, oxides of B, P, and As (for example, B2
2. The method of manufacturing a semiconductor device according to claim 1, characterized in that the method uses a polymer obtained by reacting O3, P2 O5, As2 O5, etc. with an organic polymer and dissolving it in an alcoholic solvent. 3. The method of manufacturing a semiconductor device according to claim 1, wherein the atmosphere during said diffusion is 100% nitrogen gas, and the total flow rate thereof is 400 l/H or more.