JP2539296B2 - Method for manufacturing semiconductor device - Google Patents

Description

Detailed Description of the Invention

[0001]

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

A silicon crystal used in a semiconductor device contains supersaturated impurity oxygen, and when this crystal is subjected to a heat treatment, oxygen precipitates as an oxide of silicon. It is well known that the defects caused by the precipitates getter metal impurities and the like mixed in the crystal, and this action is positively utilized in the actual manufacturing of semiconductor devices. On the other hand, if a precipitate is generated in the element region, it may cause deterioration of element characteristics.

Therefore, it is important to establish an IG heat treatment method for precisely controlling the position and speed at which the impurity oxygen is precipitated in the silicon crystal substrate.

[0004]

2. Description of the Related Art It is known that the deposition rate and amount of impurity oxygen in a silicon crystal are promoted by the presence of impurity carbon in the crystal. It should facilitate the precipitation of impurity oxygen in the silicon crystal.

However, since the mechanism of the precipitation of impurity oxygen has not been clarified so far, the influence of impurity carbon cannot be accurately taken into account in the IG heat treatment conditions, and the IG heat treatment method for silicon crystals containing impurity carbon is not possible. Was not established.

FIG. 5 shows a conventional IG heat treatment process. First, heat treatment is performed at a temperature of 1000 ° C. or higher, for example, 1100 ° C. for 1.5 hours to form a defect-free layer (Denuded Zone),
Next, after heat treatment is performed at a temperature of 650 to 800 ° C., for example, 700 ° C. for 4 hours to form nuclei of oxygen precipitation,
The temperature is raised again to 1100 ° C to grow and precipitate oxygen precipitation nuclei.

[0007]

When a silicon crystal containing impurity carbon is subjected to heat treatment, impurity oxygen (Oi) approaches the impurity carbon (Cs) to form a CO complex defect,
This becomes oxygen precipitation nuclei, but the inventor of the present invention found that 650
When heat treatment is performed at a temperature of ~ 800 ° C, this C
It was found that the reaction of the —O complex defect proceeds in the direction of dissociation, and the concentration of the C—O complex decreases. The details of this experiment will be described below.

FIG. 3 shows that the impurity oxygen (Oi) concentration is 15 ppm.
And the relationship between the heat treatment time and the C—O complex concentration when heat-treating a silicon crystal having an impurity carbon (Cs) concentration of 6 ppm at a temperature of 450 to 800 ° C. was obtained using the heat treatment temperature as a parameter. It is a graph. C-
The O complex concentration increases by the heat treatment when the heat treatment temperature is 600 ° C. or lower, and conversely decreases when the heat treatment temperature is 600 ° C. or higher, and reaches 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 and the impurity carbon (Cs) concentration in the silicon crystal and the heat treatment temperature.

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

An object of the present invention is to eliminate this drawback, and to provide a method for efficiently increasing the intrinsic gettering by increasing the defect concentration of the C--O complex which becomes an oxygen precipitation nucleus in the silicon crystal. To do.

[0011]

[Means for Solving the Problems] The above object is to perform heat treatment at a heat treatment temperature of 950 to 1250 ° C. for 1 to 4 hours on a silicon crystal having an impurity carbon concentration of 0.5 ppm or more and a solid solution limit or less. A defect-free layer is formed, and the silicon crystal on which the defect-free layer is formed is subjected to heat treatment at a heat treatment temperature of 350 to 600 ° C. for a period of 1 to 24 hours to remove a complex defect of impurity oxygen and impurity carbon. The formed silicon crystal having the complex defect is formed in an amount of 0.2 to 3.0.
This is achieved by a method of manufacturing a semiconductor device including a step of performing heat treatment by increasing the temperature to 900 to 1250 ° C. at a temperature increasing rate of ° C / min to perform intrinsic gettering. In addition, a step of performing heat treatment on the silicon crystal at a heat treatment temperature of 350 to 600 ° C. for a period of 1 to 24 hours, and a temperature increase rate of the silicon crystal of 0.2 to 3.0 ° C./min to 900 to 1250 It is effective to repeatedly perform a combination of a step of raising the temperature to ℃ and performing heat treatment a plurality of times.

[0012]

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

As the concentration of the C--O complex that becomes the oxygen precipitation nuclei increases, the oxygen precipitates increase in the subsequent heat treatment step, as shown by the following experimental results.

FIG. 4 shows the relationship between the heat treatment time and the change in the impurity oxygen (Oi) concentration when the silicon crystal is heat treated at a temperature of 700.degree. The graph A shown by the broken line shows the result when pre-annealing was performed at a temperature of 450 ° C. before the heat treatment was performed at a temperature of 700 ° C., and the graph B shown by a solid line shows the result when no pre-annealing was performed. Show. Comparing both, when the pre-annealing is performed at a temperature of 450 ° C. (graph A), the decrease of the impurity oxygen (Oi) concentration is larger. A large decrease in the impurity oxygen concentration means that the amount of oxygen precipitation is large, and
It is shown that pre-annealing at a temperature of ℃ increases the concentration of the C—O complex that becomes oxygen precipitation nuclei, and increases the amount of oxygen precipitation in the subsequent heat treatment step for growing oxygen precipitation nuclei.

Incidentally, the impurity oxygen (Oi) concentration is 15 ppm.
Therefore, even if the same heat treatment as described above is applied to the silicon crystal containing no impurity carbon, almost no oxygen precipitate is generated. This means that in a silicon crystal containing impurity carbon, C
It is shown that the -O complex acts as an oxygen precipitation nucleus.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An IG heat treatment method according to an embodiment of the present invention will be described below with reference to the drawings.

The impurity oxygen (Oi) concentration is 15 ppm,
A silicon crystal having an impurity carbon (Cs) concentration of 6 ppm is subjected to heat treatment by the heat treatment process shown in FIG. That is, first, heat treatment is performed at a temperature of 1100 ° C. for 1.5 hours to form a defect-free layer (DZ) on the surface of a silicon crystal, and then heat treatment is performed at a temperature of 550 ° C. for 2 hours to form oxygen precipitation nuclei. Increase the -O complex concentration. Then 1.
The temperature is gradually raised to 1100 ° C. at a rate of 8 ° C./min, and this temperature is maintained for about 1 hour to grow and precipitate oxygen precipitation nuclei to form an intrinsic gettering layer. If the heating rate is too high, the C—O complex, which is an oxygen precipitation nucleus, dissociates in reverse, so it is necessary to gradually raise the temperature.

As shown in FIG. 2, the heat treatment step of increasing the C--O complex concentration and the heat treatment step of growing and precipitating the nuclei thereof are repeatedly performed a plurality of times to adjust the oxygen precipitation amount. It is also possible to increase.

[0019]

As described above, in the method of manufacturing a semiconductor device according to the present invention, in the silicon crystal containing impurity carbon, the temperature at which the concentration of the C--O complex which becomes the oxygen precipitation nucleus becomes a desired value is obtained. Since the nuclear growth heat treatment is performed after the heat treatment is performed, intrinsic gettering can be efficiently performed, and a semiconductor device having excellent characteristics can be manufactured using this silicon crystal.

[Brief description of drawings]

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

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

FIG. 3 is a graph showing the relationship between C—O concentration and heat treatment time with 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 a process diagram of an IG heat treatment according to a conventional technique.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A 63-227026 (JP, A) JP-A 60-94722 (JP, A) JP-A 59-94809 (JP, A) JP-A 58- 18929 (JP, A) JP 57-141931 (JP, A)

Claims (2)

(57) [Claims] 1. A silicon crystal having an impurity carbon concentration of 0.5 ppm or more and a solid solution limit or less is heat-treated at a heat treatment temperature of 950 to 1250 ° C. for a period of 1 to 4 hours to form a defect-free layer. 3 on the silicon crystal on which the defect layer is formed
Heat treatment is performed at a heat treatment temperature of 50 to 600 ° C. for a period of 1 to 24 hours to form a complex defect of impurity oxygen and impurity carbon, and the silicon crystal in which the complex defect is formed is 0.2 to 3 900-12 at a heating rate of 0.0 ℃ / min
A method of manufacturing a semiconductor device, comprising the step of performing intrinsic heat treatment by heating to 50 ° C. and performing heat treatment. 2. A step of performing heat treatment on the silicon crystal at a heat treatment temperature of 350 to 600 ° C. for a period of 1 to 24 hours, and at a temperature rising rate of 0.2 to 3.0 ° C./min for 900 to 900 ° C. 2. The method of manufacturing a semiconductor device according to claim 1, wherein a group of the step of raising the temperature to 1250 ° C. and performing the heat treatment is repeatedly performed a plurality of times.