JPH04276627A - Semiconductor device production method - Google Patents

Abstract

PURPOSE:To improve characteristics by conducting heat treatment on silicon crystals which contain impurity carbon at a temperature by which the concentration of C-O complexes, which are the core for oxygen deposition, reach a specified value and then conducting core growth heat treatment. CONSTITUTION:Heat treatment is conducted for 1-4 hours at a heat treatment temperature of 950-1250 deg.C on silicon crystals which have an impurity carbon concentration of 0.5ppm or higher, but are below the solid solubility limit in order to form defect-free layers. Then heat treatment is conducted for 1-24 hours at a heat treatment temperature of 350-600 deg.C on these defect silicon crystals with defect-free layers so that compound defects of impurity oxygen and impurity carbon are formed. After that the temperature of these silicon crystals in which compound defects are formed is raised to 900-1,250 deg.C at a temperature speed of 0.2-3.0 deg.C/min., heat treatment is conducted, and intrinsic getterings formed.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor device, and more particularly to an intrinsic gettering heat treatment method (hereinafter referred to as an IG heat treatment method) for a silicon crystal substrate.

Silicon crystals used in semiconductor devices contain supersaturated impurity oxygen, and when this crystal is subjected to heat treatment, oxygen precipitates as silicon oxide. It is well known that defects caused by these precipitates getter metal impurities mixed into the crystal, and this effect is actively utilized in the manufacture of actual semiconductor devices. On the other hand, if precipitates are generated in the device region, they cause deterioration of device characteristics.

Therefore, it is important to establish an IG heat treatment method that accurately controls the position and speed at which impurity oxygen is deposited in a silicon crystal substrate.

0004

[Prior Art] It is known that the rate and amount of impurity oxygen precipitated in a silicon crystal is accelerated when impurity carbon exists in the crystal. This should facilitate the precipitation of impurity oxygen in the silicon crystal.

However, since the mechanism of precipitation of impurity oxygen has not been clarified until now, it has not been possible to accurately take into account the influence of impurity carbon in the IG heat treatment conditions, and the IG heat treatment method for silicon crystals containing impurity carbon has not been developed. had not been established.

FIG. 5 shows a conventional IG heat treatment process. First, at a temperature of 1000°C or higher, for example 1100°C,
．． Heat treatment was performed for 5 hours to form a defect-free layer (Denuded layer).
Next, heat treatment is performed at a temperature of 650 to 800°C, for example, 700°C for 4 hours to form oxygen precipitation nuclei, and then the temperature is raised to 1100°C again to form oxygen precipitation nuclei. It grows and precipitates.

[0007]

[Problems to be Solved by the Invention] When a silicon crystal containing impurity carbon is heat-treated, impurity oxygen (Oi) approaches impurity carbon (Cs) and forms C-O complex defects,
This becomes the oxygen precipitation nucleus, but the inventor of the present invention
When heat treatment is performed at a temperature of ~800°C, this C
It was found that the reaction proceeds in the direction of dissociation of the -O complex defect, and the concentration of the C-O complex decreases. The details of this experiment will be explained below.

FIG. 3 shows that the impurity oxygen (Oi) concentration is 15p.
pm, and the impurity carbon (Cs) concentration is 6 ppm. When a silicon crystal is heat treated at a temperature of 450 to 800°C, the relationship between the heat treatment time and the C-O complex concentration is determined using the heat treatment temperature as a parameter. This is a graph. The C--O complex concentration increases by heat treatment when the heat treatment temperature is 600°C or lower, and decreases when the heat treatment temperature is 600°C or higher, reaching an equilibrium state in a relatively short period of time. It has been confirmed that the C-O complex concentration in this equilibrium state is determined by the impurity oxygen (Oi) concentration, the impurity carbon (Cs) concentration, and the heat treatment temperature in the silicon crystal.

[0009] As described above, when heat treatment is performed at the heat treatment temperature conventionally used, C-
It became clear that the O complex concentration decreased and a sufficient amount of oxygen precipitation could not be obtained.

The purpose of the present invention is to eliminate this drawback, and to provide a method for efficiently performing intrinsic gettering by increasing the concentration of C--O complex defects that become oxygen precipitation nuclei in silicon crystals. It's about doing.

[0011]

[Means for Solving the Problems] The above object is to provide silicon crystals with an impurity carbon concentration of 0.5 ppm or more and below the solid solubility limit at a heat treatment temperature of 950 to 1250°C.
A heat treatment is performed for a period of 4 hours to form a defect-free layer, and the silicon crystal on which the defect-free layer is formed is heated to 350 to 6
A heat treatment is performed at a heat treatment temperature of 0.000C for a period of 1 to 24 hours to form composite defects of impurity oxygen and impurity carbon, and the silicon crystal with the composite defects formed has a temperature of 0.2 to 3. 90℃ with a heating rate of 0℃/min
This is achieved by a method of manufacturing a semiconductor device including a step of raising the temperature to a temperature of 0 to 1250° C. and performing heat treatment to perform intrinsic gettering. Note that the above silicon crystal is heat treated at a heat treatment temperature of 350 to 600°C for a period of 1 to 24 hours, and the silicon crystal is heated to 900°C at a heating rate of 0.2 to 3.0°C/min.
It is effective to repeat the process of increasing the temperature to ~1250° C. and performing heat treatment multiple times.

0012

[Operation] When a silicon crystal containing impurity carbon is heat-treated at a temperature of 600° C. or lower, the concentration of the C--O complex in the crystal increases, as is clear from the experimental results shown in FIG.

[0013] As the concentration of the C--O complex, which serves as oxygen precipitate nuclei, increases, the amount of oxygen precipitates increases in the subsequent heat treatment step, as shown by the experimental results below.

FIG. 4 shows the heat treatment time and the impurity oxygen (
Oi) shows the relationship with changes in concentration. Graph A shown with a broken line in the figure shows the results when pre-annealing is performed at a temperature of 450°C before heat treatment at a temperature of 700°C, and graph B shown with a solid line shows the results when pre-annealing is not performed. show. Comparing the two,
When pre-annealing is performed at a temperature of 450° C. (graph A), the impurity oxygen (Oi) concentration decreases more greatly. A large decrease in impurity oxygen concentration means that the amount of oxygen precipitated is large, and when pre-annealing at a temperature of 450°C, C-, which becomes oxygen precipitated nuclei, is
This shows that as the O complex concentration increases, the amount of oxygen precipitated increases in the oxygen precipitate nucleus growth heat treatment step performed thereafter.

Incidentally, when the impurity oxygen (Oi) concentration is 15p
pm, and hardly any oxygen precipitates are generated even if the same heat treatment as above is applied to a silicon crystal that does not contain impurity carbon. This indicates that in a silicon crystal containing impurity carbon, the C--O complex functions as an oxygen precipitation nucleus.

[0016]

Embodiment An IG heat treatment method according to an embodiment of the present invention will be described below with reference to the drawings.

A silicon crystal having an impurity oxygen (Oi) concentration of 15 ppm and an impurity carbon (Cs) concentration of 6 ppm is subjected to heat treatment using the heat treatment process shown in FIG. In other words, first, at a temperature of 1100°C, 1.5
A defect-free layer (D
Z) is formed, and then a heat treatment is performed at a temperature of 550° C. for 2 hours to increase the concentration of the C—O complex that becomes oxygen precipitation nuclei. Next, the temperature is gradually increased to 1100° C. at a rate of 1.8° C./min, and maintained at this temperature for about 1 hour to grow and precipitate oxygen precipitation nuclei to form an intrinsic gettering layer. Note that if the heating rate is too high, the C--O complex, which is the oxygen precipitation nucleus, will dissociate, so it is necessary to gradually raise the temperature.

[0018] The heat treatment process for increasing the C-O complex concentration and the heat treatment process for growing and precipitating the nuclei are repeated several times to reduce the amount of oxygen precipitated, as shown in Fig. 2. It is also possible to increase it.

[0019]

[Effects of the Invention] As explained above, in the method for manufacturing a semiconductor device according to the present invention, silicon crystal containing impurity carbon is heated to a temperature such that the concentration of C-O complexes, which become oxygen precipitation nuclei, reaches a desired value. Since the nuclear growth heat treatment is performed after the heat treatment is carried out, intrinsic gettering can be performed efficiently, and a semiconductor device with good characteristics can be manufactured using this silicon crystal.

[Brief explanation of the drawing]

FIG. 1 is an IG heat treatment process diagram according to the present invention.

FIG. 2 is an IG heat treatment process diagram according to the present invention.

FIG. 3 is a graph showing the relationship between C-O concentration and heat treatment time using heat treatment temperature as a parameter.

FIG. 4 is a graph showing the relationship between impurity oxygen concentration and heat treatment time.

FIG. 5 is an IG heat treatment process diagram according to the prior art.

Claims (2)

[Claims] Claim 1: A silicon crystal with an impurity carbon concentration of 0.5 ppm or more and below the solid solubility limit is heated at 950 to 1250°C.
A heat treatment is performed for a period of 1 to 4 hours at a heat treatment temperature of 350 to 600°C to form a defect-free layer, and the silicon crystal on which the defect-free layer is formed is heated to a heat treatment temperature of 1 to 4 hours at a heat treatment temperature of 350 to 600°C.
A heat treatment is performed for a period of 24 hours to form composite defects of impurity oxygen and impurity carbon, and the silicon crystal in which the composite defects are formed is heated at a heating rate of 0.2 to 3.0°C/min. 1. A method for manufacturing a semiconductor device, comprising a step of increasing the temperature to a temperature of 900 to 1250° C. and performing heat treatment to perform intrinsic gettering. 2. The silicon crystal is heated at 350 to 600°C.
A step of performing heat treatment for a period of 1 to 24 hours at a heat treatment temperature of 0.2 to 3.0 °C/mi
2. The method of manufacturing a semiconductor device according to claim 1, wherein the step of increasing the temperature to a temperature of 900 to 1250 DEG C. and performing heat treatment at a temperature increase rate of n is repeated a plurality of times.