JPS59184796A - Preparation of group iii-v compound semiconductor single crystal - Google Patents

Abstract

PURPOSE:To obtain group III-V compound semiconductor single crystal contg. no defect by fixing the barrel size of the crystal by operating a temp. compensation signal from the rate of weight increase of crystal in the course of growth and superposing a adjustment signal on the temp. compensation signal when a reverse response signal is contained in said signal. CONSTITUTION:A seed crystal is allowed to contact with the melt of starting material for group III-V compound semiconductor and pulled up to grow the crystal 1. The weight of the crystal 1 is continuously measured by a sensor 3, and inputted to an operating circuit 5 where it is compared with a set value to operate a temp. compensation value. The compensation value is inputted to a control circuit 6 of a heater current source to control the temp. of the heater. When a reverse response signal is contained in the superposed signal in this control, deviation of change of diameter from set value is inputted to a reverse response compensation circuit 7 to operate a temp. compensation value. The temp. compensation signal is inputted to the heater current source control circuit 6 and an adjustment signal is superposed on the temp. compensation signal. By this method. a semiconductor single crystal having uniform crystal size is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a III-V group compound semiconductor single crystal by a liquid-sealed pulling method.

Gallium arsenide (GaA5), gallium phosphide (GaP),
Indium antimony (N5B), Indium phosphorus (
■-V group compound semiconductors, such as those in It is becoming widely used as a material for batteries and photo-TA devices.

Among III-V group compound semiconductors, GaAs single crystals have 5-6 times higher electron mobility than silicon single crystals, and are capable of high-speed and low-power operation.
Speed collector circuits are being actively developed.

In addition, engineered nP single crystals exhibit high sensitivity in the low-loss band of optical fibers used in optical communications, and are attracting attention as materials for future optical communications.

As mentioned above, in order for GaAB single crystal to be used as a crystal substrate for integrated circuits, it must have high insulating properties, and must be a local quality single crystal free of physical defects such as dislocations and lattice defects, and chemical defects. , good uniformity within the crystal, and the ability to obtain large circular wafers are required. A method for manufacturing GaAs single crystals that satisfies these requirements is a high-pressure liquid seal pulling method. This high-pressure liquid-sealed pulling method uses a low-melting glass such as boron oxide (B203) as a sealant, melts GaAs under high pressure, brings a seed crystal into contact with the formed GaAs melt, and pulls it up while rotating. Cylindrical GaAs
A single crystal forms. The temperature of the melt during crystal growth under this high pressure is very sensitive; generally, as the temperature increases, the diameter of the growing crystal becomes smaller and the weight change of the crystal also becomes smaller.

On the other hand, as the temperature of the melt decreases, the crystal diameter tends to increase and the weight change also increases.

Until now, in order to maintain the crystal diameter during growth at a constant size, a weight sensor 3 has been installed on the top of a rotating pulling shaft 2 with a seed crystal attached to the bottom end, as shown in Figure 1, using the above-mentioned phenomenon.
The weight sensor continuously measures the weight of the growing crystal and sends it to the arithmetic circuit 3, and the arithmetic circuit maintains the rate of increase in the weight of the crystal at a constant value based on the measured value. The temperature of the heater for heating the crucible was adjusted via the heater power supply control circuit 6.

However, in materials such as m-v group compounds whose crystal density is smaller than the density of the melt, if the heating temperature of the melt during crystal growth is suddenly changed, an inverse response phenomenon occurs. That is, when the heating temperature is increased, the crystal diameter actually decreases, but a signal with a large crystal weight increase rate is generated, and when the temperature is decreased, the crystal diameter increases, but a weight signal with a small increase rate is generated.

Therefore, in the above control method, the heating temperature of the melt is adjusted by the rate of increase in the weight ffl signal, so if the rate of increase in the weight signal is large even though the crystal diameter is small, the heating temperature may be further increased. Since the heater is adjusted to the desired temperature, an oscillation phenomenon occurs and the resulting crystal diameter does not remain constant, and crystal defects also increase accordingly.

An object of the present invention is to provide a method for manufacturing an ITJ-V group compound semiconductor single crystal in which the diameter of the crystal body portion during growth is maintained at a constant value and the occurrence of crystal defects is suppressed.

In order to achieve the above object, in this invention, the crystal increase rate is determined from the crystal weight signal that is continuously measured, and when the increase rate does not match the set value, a correction temperature value corresponding to the difference is determined, and the above correction temperature is When adjusting the heater heating temperature using a temperature correction signal based on the value, it is determined whether a reverse response signal is included in the weight signal, and if a reverse response signal is included, the temperature is superimposed on the temperature correction signal. Adjust the temperature by adding an adjustment signal. As mentioned above, in this invention, heavy i,
(Since the temperature is adjusted using separate signals for cases in which the signal does not contain a reverse response signal and cases in which it does contain a reverse response signal, the occurrence of oscillation phenomenon is suppressed and a single crystal with a constant diameter is formed. I will do it.

For materials such as GaAs and nP whose crystal density is lower than that of the melt, if the heating temperature of the melt during crystal growth is slightly increased as shown in Figure 2 (A) (continuous line), the crystal density will increase. The rate of increase of the weight signal decreases after a time delay (dotted line). However, when the heating temperature is sharply decreased as shown in FIG. 2 (CB) (continuous line), the rate of increase in the weight signal of the crystal sharply decreases after increasing time. It is known that the reverse response phenomenon in which the weight increase rate increases despite the decreasing crystal diameter is caused by the vertical movement of the meniscus near the interface between the seed crystal and the crystal raw material melt.
In the case of GaAs, this phenomenon occurs significantly when the heating temperature of the melt is changed to around 5C. Figure 3 shows an example in which a crystal with a diameter of 50 is grown at a pulling rate of 10/hour while heating a GaAs melt at 1260 C.
This is a graph showing the relationship between the amount of change in crystal diameter and time when C is increased, where curve α is the change value obtained by converting the weight signal from the weight sensor into diameter, and b is the change value in the diameter of the actual crystal formed. , C indicates a change value obtained by converting the inverse response signal into a diameter, and has the relationship a − h = c. As shown in the above graph, the crystal diameter started to decrease as the temperature rose and became smaller by about 7 tnrn after 15 minutes, but according to the change value C converted to the heavy duty signal, the crystal diameter became thicker by about 1 u and became smaller by about 1 tnrn.
It can be seen that the image starts to be reduced after 0 minutes have elapsed.

Therefore, as a result of further consideration of the amount of change in temperature, reverse writing, and generation of response signals, in the case of the above-mentioned example, as shown in Figure 4, when the amount of change in temperature for adjusting the heater is within ±05C, the occurrence of The reverse response signal generated by
"stable region". ), when the amount of temperature change exceeds ±0.5C or more, the weight signal contains a reverse response signal that is more than the noise component (hereinafter referred to as the unstable region), and conventional crystal diameter control methods cause oscillation. It was found that accurate control could not be performed.

In the stable region, the response of the crystal diameter to temperature changes can be sufficiently approximated as a first-order response, so the function f(t) of the response of the crystal diameter to temperature changes is expressed by equation (1), and in the unstable region, the weight change is Since the value obtained by subtracting the inverse response signal value from the signal value is the true diameter change amount, the response function f(t
) is expressed in such a way that the inverse response component is compensated for as shown in equation (2).

f(t) -K・(1-θ-(t-2)/'r)・1(
−d)・・・・・・(1) f(t) = (o, o8
x・(1-(100, 1t)θ-[!1t-D, 055
x, t -e-' 2t)) 1 (t) --(2)
In the formula, K is a gain (amount of temperature change), e is a natural logarithm, T is a time constant, t is time, τ is a time delay, and 1(t) is a unit slap function.

The above equation shows an example for GaAs, and as the furnace configuration, scale, crystal pulling conditions, type of compound to be pulled, etc. change, the constants, K, T,
τ, coefficient due to compound 008°0.035.0.1
．． It is necessary to change 0.2 etc.

In this invention, as described above, the rate of increase is determined from the crystal weight signal, the formation state of the crystal diameter is determined, and if the rate of increase does not match a predetermined value, a correction temperature value corresponding to the difference is determined (1
), and when the heating temperature of the heater is adjusted using the obtained temperature correction value signal, it is determined whether a reverse response signal is included in the weight signal, and if a reverse response signal is included, (2
) A corrected temperature value is obtained based on the equation, and the heating temperature of the heater is corrected in a superimposed manner using the obtained temperature adjustment signal.

Next, to explain this 3 FA in more detail using block 1 in Figure 5, the seed crystal is brought into contact with the melt of the Ni-V group compound raw material in the crucible and pulled up while rotating, thereby growing the crystal. , this crystal weight f7i is a weight sensor? It is continuously measured and sent to the output circuit. The arithmetic circuit 5 counts the amount of change in diameter from the continuously sent weight signals, constantly compares the rate of increase with the set value, and if it deviates, calculates the amount of change in diameter corresponding to the deviated value.
'pfi positive value is calculated based on equation (1), and the obtained temperature correction signal is sent to the heater power supply control circuit B to control the temperature of the heater. Normally, in the case of a AB in which fliII control of the flow rate is performed smoothly, the temperature correction value is in the range of ±05'c or less, and no reverse response signal is included.

If the weight signal sent to the arithmetic circuit starts to increase even though the heating temperature of the heater is controlled to be increased by the positive temperature b'j signal, the weight signal will include a reverse response signal. This means that it is an arithmetic circuit! The difference between the diameter change amount obtained from the weight signal and the set value /111f is sent to the reverse response extraction circuit l1-7+7, and in the above circuit (2)
The temperature correction value is calculated based on the formula, and the temperature adjustment signal is sent to the heater power supply control circuit 6, and the heater is controlled using the temperature correction value signal that includes the reverse response signal. Do it like this. Even if the heating signal starts to decrease even though the heater is controlled to lower the temperature, this means that a reverse response signal is included, and the same operation as above is performed. Reverse response After the time period during which the signal has been generated has elapsed, the temperature correction value is calculated again based on equation (1), and the temperature is controlled.

Practically speaking, the range of the extracted flood level value that does not include the reverse response signal can be known empirically, and by having the circuit record the temperature correction signal, the humidity correction value can be determined as above. If it is within the range, it is controlled based on formula (1), and if it exceeds the above range (
2) Control is based on the formula.

As is clear from the above description, the present invention determines whether or not a reverse response signal is included in the crystal NMk signal detected when controlling the crystal diameter using the crystal weight signal measured during crystal growth. Since the optimal control is performed separately for each case, it is possible to start! Cylindrical 11TI-V that suppresses the occurrence of the M phenomenon and has a nearly uniform diameter
Group compound semiconductor single crystals can now be produced with 100% small droplets, significantly improving product reliability.

Next, the present invention will be explained with reference to examples.

Example: Qa500ji', As
5501 people, and 150 B2O2 as a liquid sealant.
1 Place the crucible on top of that, place the crucible in the M Correct Answer Machine, pressurize argon gas to create a pressure of 2o, then heat the crucible to 1260t:'' with a heater, and add n2o3 to the top.
When a GaAs melt layer is formed at the bottom, the seed crystal is brought into contact with the aAs melt surface, and the seed crystal is
Crystal growth was carried out by pulling the seed crystal to 10 mm at a rate of 1 hour while rotating the crucible in the opposite direction at a rate of 6 times per minute and 20 times per minute.

After about 1 hour, a body with a diameter of 5 Q 1 iM was formed,
At this time, the weight increase rate was 76 P/min based on the crystal weight signal measured by the M-imaginary sensor.

Temperature correction due to the change in crystal diameter calculated from the weight increase rate is performed based on equation (1), and if the correction value exceeds ±50, it is corrected based on equation (2). As a result of setting and performing crystal pulling operation for 8 hours, the length was 95yn.
A cylindrical GaAs nest crystal with a weight of about 960 g is formed, and the diameter of the body of this crystal is 50 mm, and the fluctuation rate is ±
It was within 1.5%.

[Brief explanation of the drawing]

Figure 1 is a block diagram showing a method for controlling the crystal diameter during growth using the known liquid-sealed pulling method, Figure 2 is a graph showing the relationship between temperature change and weight signal change, and Figure 6 is a graph showing the relationship between the amount of temperature change and weight signal change.
s in crystal growth] It is a block diagram showing a method of controlling the crystal diameter during growth. /...Crystal during growth, 3... Weight sensor, G...
- Heater, S... Arithmetic circuit, t... Heater power supply control circuit, 7... Reverse response correction circuit.

Claims (1)

[Claims] Temperature correction is performed by continuously measuring the weight of growing crystals to determine the weight increase rate, comparing the weight increase rate with a predetermined increase rate setting value, and using a temperature correction value corresponding to the difference. In a method for manufacturing an ITJ-V group compound semiconductor single crystal by a liquid seal pulling method in which a crystal pulling operation is performed by adjusting the heating temperature of a heater according to a signal, a weight signal when adjusting the heater heating temperature using the temperature correction value signal is used. A method for producing a single crystal, comprising: determining the presence or absence of a reverse response signal, and adding a temperature adjustment signal in a superimposed manner to the temperature correction signal when the reverse response signal is included.