JPH07102999B2 - Quartz crucible for pulling silicon single crystal - Google Patents

Description

The present invention relates to a quartz crucible for pulling a PN-compensated silicon single crystal, and more particularly to an inexpensive quartz crucible for pulling a high-quality silicon single crystal with high resistance.

[Conventional technology and its problems]

A p-type silicon substrate in which a silicon single crystal is doped with a Group 3 element and an n-type silicon substrate in which a silicon single crystal is doped with a Group 5 element are used for manufacturing a semiconductor element. The resistance value of a silicon single crystal is extremely lowered by doping each of these elements in a very small amount.

On the other hand, a silicon single crystal is usually pulled by a CZ method using a quartz crucible, but since the quartz of the crucible dissolves in the silicon melt, impurities in the quartz also lower the resistance value of the silicon single crystal. Therefore, particularly when manufacturing a silicon single crystal having high resistance and high quality, a silicon single crystal having predetermined characteristics cannot be obtained without considering not only the dopant but also the impurities attributed to the quartz crucible. .

Conventionally, a method of pulling a silicon single crystal while applying a magnetic field to a silicon melt, or a method of pulling a quartz crucible to a high purity and increasing its viscosity to prevent erosion of the crucible has been used as a means of minimizing impurities caused by the quartz crucible. Methods of suppressing are known. However, in the method of applying the magnetic field, the control is complicated, for example, it is necessary to change the strength of the magnetic field according to the amount of the silicon melt, and it is difficult to set the conditions for obtaining the predetermined characteristics. In addition, the device becomes complicated and the manufacturing cost becomes very high.

Moreover, although the viscosity can be increased by making the quartz highly pure, the correlation with the erosion amount is small. Even if the same amount of erosion occurs, a high-purity crucible naturally reduces the amount of impurities dissolved therein, but a high-purity crucible is very expensive because it is difficult to produce raw quartz powder (for example, JP 62-96388).

[Means for Solving the Problem: Structure of the Invention]

It is an object of the present invention to provide a quartz crucible which is less affected by impurities when pulling a silicon single crystal even if the impurities are contained to some extent.

According to the present invention, the content of boron is 0.1 to 0.2 ppm, and the total amount of phosphorus and arsenic (P + 0.4As) is 0.5 to 4 times the content of boron. A quartz crucible for use is provided.

Of the elements contained as irregular substances in the quartz crucible,
Boron (B), which is a group element, is a dopant that forms a p-type semiconductor, and phosphorus (P) and arsenic (As), which are a group 5 element, are dopants that form an n-type semiconductor, which are opposite to each other in a silicon single crystal. Carry out the action of. Therefore, coexistence of these elements is expected to cancel out the influence of the other. Therefore, in the present invention, the group 3 element and the group 5 element are contained in an amount such that their influences cancel each other out, whereby a quartz crucible in which the influences of these elements can be substantially ignored can be made.

Generally, the ratio of the impurity element in the silicon melt mixed into the silicon single crystal depends on the segregation coefficient (distribution coefficient) of each element. The segregation coefficients of the Group 3 element and the Group 5 element are as follows, respectively.

For example, since the segregation coefficient of B is 8 × 10 ^-1 , when 1 ppm of B is contained in the molten silicon, 0.8 ppm of B is incorporated in the silicon single crystal.

In the quartz crucible of the present invention, the total amount of impurities phosphorus and arsenic (P + 0.4As) is based on the above segregation coefficient, and
It is adjusted to 0.5 to 4 times. Here, the reason why the arsenic content is 0.4 times that of phosphorus is based on the relationship between the number of atoms per unit weight and the segregation coefficient. When the quartz crucible is eroded and mixed in the molten silicon, B, P and
As is incorporated into the silicon single crystal according to the segregation coefficient. Since B, P, and As have a p, n compensation relationship in a single crystal, if the numbers of atoms of both components are approximately the same, a p, n compensation effect that cancels the influence of the other is produced. If the P + 0.4As content in the quartz crucible is 0.5 times or less than the B content, this compensation effect is insufficient. If the P + 0.4As content exceeds 5 times the B content, the silicon single crystal undergoes p / n inversion, which is not preferable. The above relationship is the same regardless of the absolute values of the concentrations of these impurities. However, when the B content of the quartz crucible is 0.2 ppm or more, the addition of P + 0.4As causes a large amount of the total amount of impurities (B + P + As) to be mixed in the silicon single crystal, and other semiconductor characteristics are It is not preferable because it may be damaged.

〔The invention's effect〕

The quartz crucible of the present invention reduces the refining cost of the raw material quartz as compared with the conventional crucible, and since the influence of the crucible on the characteristics of the silicon single crystal to be pulled up can be ignored, the addition amount when the dopant is added can be easily adjusted. It is an excellent quartz crucible with which a silicon single crystal having high resistance and good characteristics can be obtained.

〔Example〕

The present invention will be specifically described below with reference to Examples and Comparative Examples.

(Examples 1 to 4 and Comparative Examples 1 to 3) Quartz powder having a relatively high B content was mixed with quartz powder having a relatively high P and As contents, and B, P and
A quartz crucible (16 inch diameter) containing As was prepared.
The main impurities other than B, P and As are in all crucibles Al about 6ppm, Fe about 0.4ppm, Na about 0.4ppm, K about 0.3p
pm and Ca are about 0.5 ppm, and the influence of these impurities on the characteristics of the silicon single crystal pulled by using each crucible is small.

40 kg of raw material silicon was put into each crucible and melted to pull up a silicon single crystal. The pulled single crystal was about 30 kg in each case, which was about 75% of the charged silicon. The crystal type and the specific resistance of the wafer obtained from the top (represented by "upper" in the table), middle (represented by "middle" in the table) and bottom (represented by "lower" in the table) of the obtained silicon single crystal were measured. The measured values are shown in the table.

As shown in the table, when the content of P and As is small with respect to B, the specific resistance of the silicon single crystal is small (Comparative Example 1),
On the other hand, when the contents of P and As are too large with respect to B, the silicon single crystal is inverted to n-type (Comparative Examples 2 and 3).

Claims (1)

[Claims] 1. The content of boron is 0.1 to 0.2 ppm, and the total amount of phosphorus and arsenic (P + 0.4As) is 0.5 to 0.5 of the content of boron.
A quartz crucible for pulling up a silicon single crystal, which is four times as large.