JPH01282822A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To inhibit the lowering of the resistivity of an n-type substrate, and to prevent the deterioration of breakdown strength characteristics by executing heat treatment in a hydrogen atmosphere at the temperature and the time of 1100 deg.C/10Hr equivalent values or more as the preprocess of a process in which an electrode is evaporated. CONSTITUTION:A semiconductor device is manufactured by using an n-type silicon substrate having resistivity rho of 10OMEGA.cm or more. A heat treatment process 8 in a hydrogen atmosphere at the temperature and the time of 1100 deg.C/10Hr equivalent values or more is provided as the preprocess of a process 6 in which an electrode is evaporated. The effect of the heat treatment process in the hydrogen atmosphere is displayed with the higher temperature of treatment and the longer time of treatment, and the relationship of the temperature and the time can be selected from the capacity of the device and an economical viewpoint. Even when heat treatment at approximately 500 deg.C is executed, the resistivity of a base body is not lowered, thus preventing the deterioration of breakdown strength characteristics. Accordingly, the lowering of the resistivity of the N-type substrate is suppressed, and the deterioration of breakdown strength characteristics is obviated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention particularly relates to a method of manufacturing a semiconductor device for obtaining breakdown voltage characteristics depending on the impurity concentration in a substrate.

[Conventional technology]

In general, semiconductor devices require two steps: introducing P-type and n-type impurity elements into an n-type Si substrate containing a certain amount of impurities by thermal diffusion at an angle of 1000'0 or more to obtain a p-n junction;
This manufacturing method is described in detail with reference to FIG. 4, which is manufactured by the electrode attachment process before and after step C. Here, the substrate is p='n
Ω''m, FZ method, n-type (P-doped) Si single crystal wafer. First, in step 1, steam oxidation is performed at 1100''O/3Hrs to form a SiO film on both sides of the substrate.

In step 2, the SiO2 film on the surface of the substrate is removed using a well-known photoresist as a mask. Step 3 is a B diffusion step to form a p-type layer, in which well-known B, 03, BN, BBr,
, B2H, etc., at 900°C, and
It consists of a subsequent drive process. In this case, 12.5
The test was carried out at 0° C. for 90 hours in an atmosphere of 25960.75% Nt.

Step 4 is a step of removing Sin on the back side, similar to step 2, and step 5 is a P diffusion step to obtain 9 layers, which consists of a deposition step using known POCI, PH3, and a drive step. 1200' to obtain a diffusion depth of 5 μm.
O/5 Hr was conducted in a 0.100% atmosphere.

Step 6 is a step of forming a layer that is directly applied to Si using an evaporation method using AI as an electrode material. Step 7 is a step of forming an electrode layer using an evaporation method using AI as an electrode material. In step 7, N! This is a process of performing sintering treatment in an atmosphere.

By the way, the specific resistance ρ of the substrate is the required reverse blocking voltage (
(hereinafter referred to as withstand voltage), and the specific resistance p of the substrate
The relationship between the specific resistance p and the withstand voltage obtained when using that substrate is widely known in the literature, and as shown in Figure 5, the specific resistance p
The withstand voltage also decreases with the decrease in . By the way, in the manufacturing process of mesa diode wafers, the fourth
In the final heat treatment step 7 at 450° C. as shown in the figure, a decrease in ρ occurs as shown in FIG. In Figure 6, the horizontal axis is 450°C
The vertical axis on the left is the rate of decrease in ρ, and the vertical axis on the right is the measured value of ρ. As the sintering time increases, e decreases. On the other hand, FIG. 7 shows changes in the breakdown voltage distribution, and as shown in the figure, as e decreases as the heat treatment time increases, the breakdown voltage distribution also decreases accordingly.

[Problem to be solved by the invention]

As mentioned above, in the conventional semiconductor device manufacturing method, p-n
After forming the bond, in the heat treatment process at around 500'0, the resistivity of the n-type substrate decreased compared to the initial stage, and there was a problem that the desired breakdown voltage characteristics could not be obtained.

Another example of the conventional method is a so-called glass passivation type structure in which after forming a p-n junction, a mesa groove is formed to expose the junction, and low melting point glass is buried in this groove. Generally, a step of annealing at around 500° C. for 60 to 120 minutes is used to remove strain at the interface between Si and glass, but in such a case, the resulting breakdown voltage distribution deteriorates significantly.

This invention was made to solve the above-mentioned problems, and provides a method for manufacturing a semiconductor device that can suppress a decrease in specific resistance of a substrate due to heat treatment at around 500°C and prevent a decrease in breakdown voltage characteristics. The purpose is to

[Means to solve the problem]

The method for manufacturing a semiconductor device according to the present invention is a method for manufacturing a semiconductor device using an FZ silicon substrate having an n-type resistivity e of 10Ω·α or more, in which the process is performed at 1100° C./ This process includes a step of performing heat treatment in a hydrogen atmosphere at a temperature and time equivalent to 10 hours or more.

[Effect]

In this invention, a heat treatment process in a hydrogen atmosphere at around 1100°C is introduced, and even if the heat treatment is performed at around 500°C, the specific resistance of the substrate does not decrease, and therefore the voltage resistance characteristics are improved. Deterioration is prevented. The higher the treatment temperature and the longer the treatment time, the more effective the heat treatment step in a hydrogen atmosphere becomes, and the relationship between temperature and time can be selected from the viewpoint of equipment capacity and economics.

〔Example〕

An embodiment of the present invention will be described below with reference to the process diagram of FIG.

In this step, heat treatment step 8 in a hydrogen atmosphere is performed after step 5.
The other steps are the same as before.

The characteristics of this process are shown in FIG. This figure is a diagram when the sintering conditions to cause a decrease in ρ are 450℃/60 minutes.The vertical axis is the rate of decrease in ρ, and the horizontal axis is the hydrogen treatment time, using the hydrogen treatment temperature as a parameter. be. As is clear from this figure, it can be seen that the longer the processing time and the higher the temperature, the lower the rate of decrease in e in the sintering process. Therefore, when compared with the conventional method as shown in FIG. 3, it can be seen that the rate of decrease in ρ is significantly suppressed.

Regarding the causes of such phenomena and effects, please refer to 1017ato
Si made by the CZ method is said to contain r/cnt of oxygen.
In crystals, 101
It is well known that an increase in the number of donors on the order of 1000 nm is recommended, and even in FZ wafers such as 10"7m, which are said to have a low oxygen concentration, the increase in the number of donors in Si during long-term oxidation atmosphere treatment at high temperatures is well known. This is thought to be due to an increase in the oxygen concentration in the hydrogen atmosphere and a change in the form of oxygen during treatment under a hydrogen atmosphere.

In this way, p≧10Ω・cm (5X 10”/ad
) when using an n-type SI with a specific resistance of 450°C.
To prevent the breakdown voltage drop caused by annealing in
It is sufficient to carry out heat treatment in a hydrogen atmosphere corresponding to 100°O/15HrC).

Moreover, the same effect can be obtained even if the step of heat treatment using hydrogen in this atmosphere is carried out in the p-type diffusion in step 3 or the n-type diffusion in step 5.

〔Effect of the invention〕

This invention provides a method for manufacturing a semiconductor device using an FZ silicon substrate having an n-type resistivity e of 100.
1100°O/1 as a pre-process to the electrode and vapor deposition process.
This process includes a process of heat treatment in a hydrogen atmosphere at a temperature and time equivalent to 0Hr or more, and suppresses the decrease in specific resistance of the n-type substrate during the heat treatment process at around 500°C after forming a p-n junction. This has the effect of preventing deterioration of voltage resistance characteristics.

[Brief explanation of the drawing]

FIG. 1 is a process diagram showing an embodiment of the present invention, and FIG. 2 is a graph showing the relationship between hydrogen treatment time and specific resistance of the present invention.
Similarly, Fig. 3 is a graph showing the relationship between sintering time and specific resistance, Fig. 4 is a process diagram showing the conventional method, Fig. 5 is a graph showing the relationship between breakdown voltage and specific resistance, and Fig. 6 is a graph showing the relationship between breakdown voltage and specific resistance. The figure is a graph showing the relationship between sintering time and resistivity in the conventional method, and FIG. 7 is a graph showing the relationship between breakdown voltage and sintering time in the conventional method. In the figure, 8 is a heat treatment step in a hydrogen atmosphere. Note that the same reference numerals in each figure indicate the same or corresponding parts.

Claims (1)

[Claims] In a method for manufacturing a semiconductor device using an FZ silicon substrate with an n-type resistivity ρ of 10 Ω・cm or more, as a pre-step to the step of vapor depositing an electrode, a hydrogen atmosphere is heated at a temperature and time equivalent to 1100°C/10 Hr or more 1. A method of manufacturing a semiconductor device, the method comprising the step of performing heat treatment at a temperature.