JP2583962B2 - Method for manufacturing semiconductor device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor device having an antimony impurity diffusion layer such as a collector buried layer for a bipolar integrated circuit.

2. Description of the Related Art As a method of forming an antimony impurity diffusion layer of a semiconductor device, a so-called application / diffusion method of applying and diffusing an antimony / glass solution onto a semiconductor substrate surface has recently been widely used.

Hereinafter, the conventional antimony application / diffusion method will be described.

In the antimony coating diffusion method, first, antimony-containing impurities, for example, antimony trichloride (SbCl ₃ ) or alkoxyne antimony (Sb (OR) ₃ ) are mixed with an organic solvent such as silicon dioxide (Sio ₂ ) and acetone. The antimony glass solution is applied to the main surface of the semiconductor substrate using a spinner or the like, and is baked in an oxidizing gas at about 350 ° C. or more for 30 minutes or more. Then, the organic solvent almost evaporates, and an antimony compound, for example, Sb ₂ O ₃ or Sb ₂
O ₅ replaces the antimony glass layer containing. Thereafter, a desired antimony diffusion layer is to be formed by performing thermal diffusion in an oxidizing gas at a high temperature of 1230 ° C. to 1270 ° C.

Problems to be Solved by the Invention When thermal diffusion of antimony (Sb) is performed by the above method, a rosette may be generated on the surface of the semiconductor substrate. And the rosette, a compound of Sb · Si · O, has a protruding, usually, for example, in the HF / H ₂ O etching solution, an etching impossible, and requires a special etching solution. Further, epitaxial growth does not work well on the rosette, causing crystal defects. Moreover, the mechanism of rosette generation has not yet been elucidated. In the prior art, the generation of a rosette was suppressed by making the film thickness of the antimony glass layer as thin as 500 to 1000 mm. However, in this method, the antimony compound, Sb ₂ O ₃ or Sb ₂
O ₅ is started to sublimate from the glass layer surface, a few minutes, and the glass layer, because the Sb element concentration of the semiconductor substrate interface is reduced, not Yuka sufficiently diffused into the semiconductor substrate. Moreover, at the interface between the semiconductor substrate and the glass layer containing the antimony compound, O ₂ in the oxidizing gas diffuses,
Since the oxide film grows rapidly due to the reaction rate before diffusion of the oxide film, the oxide film becomes an obstacle, and it takes time for Sb to diffuse through the oxide film and reach the semiconductor substrate. For this reason, the sheet resistance (Rs) of the antimony diffusion layer is unlikely to decrease. For example, to reduce Rs to about 20Ω / □, it is necessary to perform diffusion for as long as 400 to 700 minutes, which causes a problem of generating a rosette. there were.

An object of the present invention is to solve the above-mentioned conventional problems, and an object of the present invention is to provide a method for quickly reducing the sheet resistance (Rs) using a thin antimony glass layer.

Means for Solving the Problems In order to achieve this object, a method of manufacturing a semiconductor device according to the present invention is directed to a method of applying an antimony glass solution after opening a predetermined region of an insulating film on a main surface of a semiconductor substrate. A second step of evaporating the organic solvent in the coating layer of the antimony glass solution to form an antimony glass layer, and then forming a first diffusion temperature in an oxidizing gas at a first diffusion temperature. A third step of performing a heat treatment to diffuse an antimony impurity while growing an oxide film on the interface between the antimony glass layer and the semiconductor substrate at a slow rate of 10 ° / min or less;
And a fourth step of performing a heat treatment at a second diffusion temperature higher than the first diffusion temperature in the oxidizing gas.

According to this manufacturing method, first, an antimony glass layer is formed in the first and second steps, and a heat treatment is performed at the first diffusion temperature in the oxidizing gas in the third step, and the heat treatment is performed at 10 ° / min or less. The antimony impurities are diffused while growing the oxide film at a slow speed, so that the diffusion proceeds at a diffusion speed faster than the growth speed of the oxide film, diffusion through the oxide film is performed, and thereafter, the temperature is higher than the first diffusion temperature. When diffusion is performed at the second diffusion temperature,
Since the thickness of the oxide film grown up to that time is small, even if the growth rate of the oxide film is increased by the increase in the diffusion temperature, the antimony impurities diffuse without interruption. Therefore, even when a thin antimony glass layer is used, a sufficiently low sheet resistance (Rs) can be realized in a short time.

Embodiment Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

FIGS. 1, 2, and 3 show one embodiment of the present invention, and show a cross-sectional view of a semiconductor device, an example of a temperature rise / fall profile of thermal diffusion, and an interfacial oxide film growth rate, respectively.

In FIG. 1, 1 is a semiconductor substrate made of P-type silicon, 2a and 2b are field oxide films grown on the semiconductor substrate 1, and 3 is formed by a spin-on coating method or the like.
The antimony glass layer 4 having a thickness of about 1000 ° or less is an N-shaped diffusion layer formed by diffusing Sb from the glass layer 3.

In FIG. 2, 5 is the temperature rise / fall profile, and 6 and 7 are the first and second diffusion times, respectively, in which the diffusion proceeds effectively.
6T and 7T indicate first and second diffusion temperatures, respectively, and diffusion is performed in an oxidizing gas. The first diffusion temperature 6T and the oxidizing gas flow rate are set so that the supply rate is controlled for the growth rate of the oxide film growing at the interface.

In FIG. 3, reference numerals 8 and 9 denote growth curves of the oxide film at the first and second diffusion temperatures, respectively.
The oxide film grows uniformly during the diffusion of, indicating that the supply is rate-determined. Further, the average of the growth rate is lower than the Sb diffusion rate, and is about 10 ° / min or less. In addition, 10
Is an example of the growth curve of the oxide film when diffusion is performed by a conventional method, and shows a sharp rise immediately after the start of diffusion, indicating that the reaction is rate-determined.

The operation of the method of manufacturing the semiconductor device according to the present embodiment configured as described above will be described below.

First, the antimony glass layer 3 having a thickness of about 1000 ° or less in FIG. 1 is formed, and is diffused in an oxidizing gas using the temperature rise / fall profile 5 in FIG. An oxide film is formed at the interface with the oxide film, and the grown film thickness of the oxide film is determined to grow at a first diffusion temperature 6T according to the curve 8 in FIG.
Therefore, immediately after the start of diffusion, the grown film thickness is almost 0, and does not become an obstacle. Therefore, Sb easily diffuses into the semiconductor substrate 1. As the diffusion time elapses,
The thickness of the grown film uniformly increases, but has a slow speed of about 10 ° / min or less. Since the Sb diffusion speed is higher, Sb is diffused without interruption. Further, when the temperature is increased to the second diffusion temperature 7T for the purpose of accelerating the diffusion, the growth film thickness is increased according to the curve of 9, but the first diffusion temperature has already been increased.
Since there is an oxide film grown under 6T, the supply is rate-limited, and the Sb diffusion rate is set to be higher as described above, so that Sb diffuses without interruption.

As described above, according to the present embodiment, the growth rate of the oxide film generated at the interface between the antimony / glass layer 3 and the semiconductor substrate 1 is controlled to be about 10 ° / min by controlling the supply rate.
Sb can be diffused efficiently. In particular, as in the present embodiment, in the configuration of the temperature rise / fall temperature profile of thermal diffusion in which the first diffusion temperature 6T and the second diffusion temperature 7T higher than the first diffusion temperature are provided, the oxidizing gas flow rate is increased. Since the above conditions can be satisfied, the variation in the sheet resistance (Rs) is small, and since the second diffusion temperature 7T is high, the sheet resistance (Rs) can be reduced in a short time.

In addition, the present invention is not limited to the above embodiment, the combination of the temperature rise and fall profile of thermal diffusion and the oxidizing gas flow rate,
An oxide film that satisfies two conditions, that is, an oxide film formed at the interface grows under supply-controlled rate, and that an average growth rate is lower than the diffusion rate of Sb, is included.

Effect of the Invention The present invention provides a third method after forming an antimony glass layer.
In the step, heat treatment is performed at the first diffusion temperature in the oxidizing gas to diffuse the antimony impurities while growing the oxide film at a low rate of 10 ° / min or less. Even if the diffusion proceeds and diffusion is performed through the oxide film, and then diffusion is performed at a higher second diffusion temperature, the oxide film grown so far has a small thickness. However, even if the speed increases, the antimony impurity is rapidly diffused without interruption, and a method for manufacturing a semiconductor device with a small amount of rosette can be realized.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a semiconductor device according to one embodiment of the present invention, FIG. 2 is a diagram showing a temperature rise / fall profile of thermal diffusion according to one embodiment of the present invention, and FIG. It is a figure showing a speed. 1 ... P-type silicon semiconductor substrate, 2a, 2b ... field oxide film, 3 ... antimony glass layer, 4 ... N-type diffusion layer, 5 ... temperature rise / fall profile, 6,7 ... first, first Diffusion time 2, 6T, 7T: first and second diffusion temperatures, 8, 9: growth curves at first and second diffusion temperatures, 10: growth when diffusion is performed by a conventional method Curve example.

Claims (1)

(57) [Claims] A first method of applying an antimony glass solution after opening a predetermined region of an insulating film on a main surface of a semiconductor substrate.
Next, a second step of forming an antimony glass layer by volatilizing the organic solvent in the coating layer of the antimony glass solution, and then forming a first diffusion temperature in an oxidizing gas. A third step of performing a heat treatment to diffuse an antimony impurity while growing an oxide film on the interface between the antimony glass layer and the semiconductor substrate at a slow rate of 10 ° / min or less; And performing a heat treatment at a second diffusion temperature higher than the first diffusion temperature.