JPS6126591A - Crystal growing method - Google Patents

Abstract

PURPOSE:To obtain crystal having improved uniformity of specific resistance by a relative simple device, by growing crystal by crystal pulling method while dissolving crystal which contains electrically-conductive type impurities opposite to impurities contained in melt in the melt. CONSTITUTION:Si Polycrystal containing B is put in the quartz crucible 1 and dissolved to give the melt 2. Just before it is sent to a barrel part immediately after growth starting, the n type Si crystal 3 containing P is immersed in the melt 2, and gradually dissolved with growth of the Si single crystal 4. In this case, the n type Si crystal 3 containing P is preferably in a cylindrical shape in order to improve specific resistance distribution of a section perpendicular to a pulling axis. The lowering speed of the n type Si crystal 3 containing P differs depending upon raising speed of the Si single crystal 4, its diameter, the concentration of the n type Si crystal 3 containing P, and the contact area of it and the melt, and they are adjusted to give the P type Si single crystal with 10OMEGA.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for growing a crystal by a pulling (CZ) method, and more particularly, to a method for growing crystals so that the specific resistance value in the direction of the pulling axis becomes constant.

Crystals such as silicon (St) used in semiconductor device manufacturing are p
Poron (B) is used as a type impurity, and g(
P), arsenic (As), antimony (Sb), etc. are added,
A constant specific resistance value (usually selected depending on the application between 0.01 and 100 Ωcm) is used.

It is desirable for a semiconductor device to have a uniform resistivity distribution due to design requirements, but in a crystal grown by the usual CZ method, the impurity concentration distribution in the pulling axis direction changes according to the following equation due to segregation. 1) C=kCo(1jrik-'.

Here, C0 is the initial impurity concentration in the melt, β is the ratio of the amount crystallized to the initial melt amount (assimilation rate), C is the impurity concentration at the solidification rate l, and k is the segregation coefficient.

The resistivity distribution in the direction of the pulling axis is determined by the concentration distribution of impurities taken in according to the above equation.

Figure 3 shows the resistivity distribution of typical impurities, which is a calculated value when a 4-inch crystal is pulled from 20 kg of melt.

As can be seen from the figure, when the uniformity of resistivity of the crystal required as a semiconductor substrate becomes stricter, the
Only a portion can be used and the yield is reduced. This tendency is due to impurity rods with a small segregation coefficient.

Therefore, various methods are used to improve the uniformity of the specific resistance of the crystal.

(Reference) 1) W, G, Pfann, AIME 194.7
47 (1952).

[Conventional technology]

Below, a conventional example of a method for improving the uniformity of specific resistance of a crystal is shown.

i, Multiple Ingot Growth
Method 2) In this method, pulling of the single crystal is once completed at the limit of the required specific resistance width, a new polycrystal is added to the melt to adjust the impurity concentration, and the crystal is pulled again.

ii. Continuous MCharge method'' As shown in Figure 4, this is a method in which melt is continuously added during single crystal pulling. The melt 2 is moved so that the impurity concentration of the melt in the growth furnace 13 is always kept constant.

In addition, in the figure, 14 is a communication pipe for moving the melt;
15 is a heater, 16 is an argon gas inlet, 17 is an internal pressure control valve, 18 is a melt level position sensor, 1
9 indicates an automatic diameter control sensor.

iii. Double crucible method 4) As shown in FIG. 5, the quartz crucible is doubled, and the inner and outer crucibles IA and IB are connected through a thin tube 2o, and the impurity concentration C' in the inner crucible is c'-c. /, the impurity concentration incorporated into the crystal will always be 00.

However, each of the conventional methods has certain drawbacks.

i. The straight body portion of the single crystal obtained is small compared to the total amount of melt, resulting in poor yield. It is easily contaminated during recharging.

ii) The device becomes large-scale and is not economical.

iii. The device is complicated and the internal crucible is difficult to hold, rotate and adjust.

(Reference) 2) R, L, Lane and A, H, Kach
areIJ, Crys, Growth 50,437 (
1983).

3) G, Fiegl.

5solid 5tate Technology, Au
Gust, 121 (1983).

4) K., E., Ben5on, W., Lin and
B., P., Martin.

Sem1conductor 5ilicon 19
8L33 (1981).

[Problem that the invention seeks to solve]

Conventional methods for improving the uniformity of resistivity of crystals using the CZ method have poor yields and the risk of contamination, or the equipment is complicated and large-scale, making it difficult to operate, maintain, and adjust the equipment.

[Means for solving problems]

The solution to the above problem is that during crystal growth using the pulling method,
This is achieved by the crystal growth method according to the present invention, in which a crystal containing an impurity of the opposite conductivity type to the impurity contained in the melt is grown while being dissolved in the melt.

[Effect]

During crystal growth, a crystal containing impurities of the opposite conductivity type to the impurities contained in the melt is dissolved and both types of impurities are incorporated into the single crystal, and these impurities cancel each other out to form carriers corresponding to the compensated value. By keeping the concentration (this value is related to specific resistance) constant, uniformity in the specific resistance of the crystal can be obtained using a relatively simple device.

Furthermore, if the impurity of the opposite conductivity type to be added to the melt is selected to be close to the covalent bond radius of the base crystal, it will not harm the crystallinity.

[Example] FIG. 1 (al is a schematic cross-sectional view of an apparatus showing an example of the present invention.

The figure shows the case where a p-type Si crystal of about 10 Ωcm is grown. - First, Si polycrystals doped with B are placed in a quartz crucible 1 and melted to obtain a melt 2. Immediately before entering the straight body after the start of growth, the n-type Si crystal 3 containing P is immersed in the melt 2, and is gradually melted as the Si single crystal 4 grows. In this case, the n-type Si crystal 3 containing P is preferably cylindrical as shown in the figure in order to improve the resistivity distribution in the cross section perpendicular to the pulling axis.

In addition, the pulling speed of the n-type Si crystal 3 containing P varies depending on the pulling speed and diameter of the Si single crystal 4, the P concentration of the n-type Si crystal 3 containing P, and the area of contact with the melt, and is 10Ω.
Adjustment is made so that a p-type Si single crystal 4 of cm is obtained.

Note that 5 is a motor, 6 is a molybdenum (gate 0) wire, 7 is a motor, and 8 is a heater.

FIG. 1 is a perspective view of an n-type Si crystal 3 containing P.

FIG. 2 shows the distribution of crystals obtained according to the present invention in the direction of the pulling axis.

If the allowable range of specific resistance is 10±1 Ωcm, the normal CZ method shown by the dotted line can only use about 25% of the total melt as shown in 10, but according to the present invention, about 70% can be used as shown in 11. can be used.

Further, the pull-down drive section of the n-type Si crystal 3 containing P can be easily made.

Furthermore, consider the crystallinity of a crystal in which a P impurity is mixed with a B impurity. If the coexistence bond radius of Si is 1, then B is 0
．． 75, P is 0.94, and it can be seen that distortion due to the difference in bond radius is smaller with P. ') When the microdefect density of the crystal actually obtained according to the present invention was evaluated using 5ecco etching, it was about 103cm-2, which is the same as when no P is introduced, and it does not affect the crystallinity. It became clear that

(Reference) 5) Hideki Tsuya, Yoji Kondo, Masaru Kanamori, Proceedings of the 30th Applied Physics Association Lecture Proceedings (1983) p.
, 662゜ [Effects of the Invention] As explained in detail above, according to the present invention, in the CZ method, the specific resistance of the crystal can be made uniform with an apparatus that is free from contamination and is easy to operate, maintain, and adjust. This improves the properties and does not increase defect density.

[Brief explanation of drawings]

Figures 1 (a) and (bl are a schematic cross-sectional view of a device showing an embodiment of the present invention and a perspective view of an n-type Si crystal containing P;
Figure 3 shows the distribution diagram of the crystal in the direction of the pulling axis obtained by the present invention, Figure 3 shows the resistivity distribution diagram of typical impurities in the direction of the pulling axis obtained by the ordinary CZ method, and Figure 4 shows the resistivity distribution diagram in the direction of the pulling axis of the crystal obtained by the conventional continuous charge method. Equipment schematic%
Formula % FIG. 5 is a schematic cross-sectional view of an apparatus using the conventional double crucible method. In the figure, 1 is a quartz crucible, 2 is a melt, 3 is an n-type Si crystal containing P, and 4 is a p-type St single crystal. 7th Et 2 pieces

Claims (1)

[Claims] A crystal growth method characterized by growing a crystal containing an impurity of an opposite conductivity type to an impurity contained in the melt while dissolving it in the melt during crystal growth by a pulling method.