JPS6345200A - Production of single crystal of iii-v compound semiconductor - Google Patents

Abstract

PURPOSE:To produce single crystal in a desired shape automatically and in good reproducibility, by adding correction amounts to a changed amount of measured weight per unit time of crystal growth to give a control amount and regulating heater temperature by using a reference change amount of weight as a set amount. CONSTITUTION:In liquid-encapsulated Czochralski method wherein semiconductor single crystal 6 is pulled up through a liquid encapsulating agent 2 such as B2O3, etc., from raw material melt 3 of III-V compound such as GaAs, etc., in a crucible 1, weight of the single crystal 6 is continuously detected by a weight sensor 7. To the obtained changed amounts DW are added correction amounts by buoyancy of the liquid encapsulating agent 2, reverse response, surface tension or meniscus of the melt 3 at real time in a correction amount calculator 11 to give an effective weight change amount DWC per unit time. This amount is used as a control amount, a reference weight change amount Dwref per unit time corresponding to the aimed crystal shape based on practical crystal length Z is regarded as a set amount and both are compared by a divided difference device 16. A change amount Tp of heater temperature per unit time is regulated by a regulator 17, a temperature program 18, a temperature regulator 19, etc., based on the deviation amount of the divided difference device.

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a method for manufacturing an m-v group compound semiconductor single crystal by a fully automatic shape control method using a liquid-filled Czochralski method. [Prior art] At such as GaAg, InP, GaP, etc.
One of the methods for producing a -V group compound semiconductor single crystal is the liquid-contained Czochralski method (LKC method). This is B
, 03 is used as a sealant for the GaAs raw material melt, and while suppressing the decomposition of the compound under high pressure, the formed compound melt (with a seed crystal attached and pulled up while rotating) is used as a sealing agent for the GaAs raw material melt. This method allows the entire growth of a cylindrical compound single crystal. However, in this case, the crystal growth occurs in free space, and the temperature distribution is difficult to control due to the presence of a liquid sealant and thermal convection of high-pressure gas. There is a problem in that it is very difficult to control the shape of the crystal because it is made by molding. Methods for controlling the shape of the crystal include the coracle method (for example, Japanese Patent Application Laid-Open No. 57-200286), the ring method (column method), etc. : Japanese Unexamined Patent Publication No. 58-41796), as well as the weight method (
Column: JP-A-58-145692, JP-A-59-1
No. 84796, etc.), and the gravimetric method is used to play an important role in liquid-filled Czochralski crystal growth. How to grow crystal weight? The diameter of the crystal is calculated based on the amount of change per unit time, the amount of weight change is determined based on the target crystal diameter, and the temperature of the heater that heats the crystal raw material melt is adjusted according to the deviation amount. Two diameter controls are performed. [Problems to be Solved by the Invention] However, in the liquid-sealed Czochralski method, the crystal weight detected by the weight sensor is... Because it is affected by the buoyancy of the liquid sealant and the surface tension of the melt, the value becomes smaller than the actual solidified crystalline type], and furthermore, the amount of weight change per unit time with respect to the weight of the lever itself is When used as a control amount, this value is largely different from the true amount of weight change, and as a result, there is a problem in that the crystal shape is controlled to be completely different from the target crystal shape. Further, as a phenomenon unique to the ■-V group compound semiconductor, a phenomenon called reverse response occurs when the crystal diameter changes rapidly. In other words, the specific gravity of a solid is smaller than that of a liquid, so as the crystal diameter increases, the amount of weight change decreases and the diameter decreases (in contrast, the amount of weight change increases. Because of this phenomenon, 2ζ was detected. When controlling the crystal diameter using the amount of weight change, reverse control 2 should be performed for sudden diameter changes (MJK).
As a result, a phenomenon of diameter expansion occurs, and it is difficult to obtain a desired shape with a constant diameter in the straight body portion. Furthermore, if the temperature of the heater itself that heats the crystal raw material melt is controlled as in the conventional shape control method, the temperature of the raw material melt may change suddenly, causing sudden diameter fluctuations. There is a problem in that the above-mentioned reverse response phenomenon tends to occur. Is the present invention based on the above-mentioned problem? The purpose of the present invention is to provide a method for automatically producing a single crystal in a desired shape with good reproducibility. 〔problem? Means for Solving the Problem] The present invention provides a method for manufacturing an m-v group compound semiconductor single crystal using a liquid-sealed Czochralski method.

[Effect]

Hereinafter, the present invention will be explained in detail using the drawings. 1st
As shown in the figure, set up the ■-■ group compound semiconductor single crystal pulling equipment! F:1 is pulled up to a crystal raw material melt 3 such as GaAs covered with a liquid sealant 2 such as B2O3.
The crystal 6 is grown by bringing the seed crystal 5 fixed to the B4 into contact and pulling it up. The weight of this crystal 60 is continuously detected as a voltage signal by the No. 1 sensor 7 attached to the pulling shaft 4, converted to a weight signal Wt by the converter 8, and noise components are removed by the signal smoothing processing circuit 9. . The measured weight change amount Dw obtained by sampling this signal every unit time is calculated, and the correction amount calculator 11
The correction amount is added in real time to calculate the effective weight change amount Dwc' per unit time. Furthermore, the crystal shape calculator 12 calculates the crystal radius R1 and the effective growing crystal length z2 based on the measured weight change amount Dw, and displays the CRT 13.
to be displayed. On the other hand, a target value calculator 15 calculates a target effective weight change amount Dwref corresponding to the effective growth crystal length 2 from the target crystal shape generator 14 every unit time. The difference unit 16 calculates the deviation amount between the effective weight change Dwc and the target effective weight change Dwrsf, and based on this deviation signal, the controller 17 calculates the crystal original amount melt as a real-time manipulated variable using the digital P. temperature? Obtain the temperature change amount TP per unit time of the heater to be adjusted. This temperature change TP is converted into a temperature control signal by a temperature programmer 18, and the temperature TH of the heater is controlled by a temperature controller 19, thereby controlling the entire temperature of the crystal raw material melt per unit time. The correction amount calculator 11 calculates the effective weight change amount 1'wc per unit time as follows. Figure 2 is a schematic diagram of crystal growth. , crystal density is Pa, liquid sealant density is ρb, surface tension due to melt is γ8, crystal solidification volume? ■8. If the solidified volume of the crystal in the liquid sealant is "sb s cB" and the volume of the meniscus at the interface between the crystal and the melt is vm, then the general measurement type ff1Wh is Wh = /'s"s-ρ
bvBb+(ρ0-ρb)Vm+γ8...Given by ■. Here, the meniscus is a part generated by surface tension near the interface i between the crystal and the melt, as shown in Figure 3, and the shape of the interface becomes convex or concave depending on the growth conditions such as the thermal environment. . The change in the diameter of the crystal actually occurs in accordance with the change in the shape of the meniscus; as the height of the meniscus decreases, the diameter increases, and as the height of the meniscus increases, the diameter decreases (see FIG. 4). However, the meniscus body Tlv+ can be approximated to a cylinder, and it is determined as Vm=πR2: (Next, the crystal diameter is the function r of the crystal length). From Figure 2, the crystal solidification volume V, = P=x (rf:Z))”dZ=
-■B! Crystal volume in 03 vs b = fz〒” (r (Z) )”dZ
−■Meniscus volume V = πR”H...■ On the other hand, from the law of conservation of greatness among E, o, and inside, is the volume of B, o3?■
If BxOs, then VB, 0. +VBb+Vm=”Fte”L
...-■ Therefore, the formula 0 is wh=Psfz-Hπ(r(z))"az pb("
Rc”L V]32o, )+ PeπR”H+ γe
−” ”, 5i11 per unit time
Constant weight change ffiDw = P9πRg (feed -
m)-ρbπRo2i+ρ8(πR2-1+2πR-Poor H)+18...■, vP=z, DR
=H,D. =L, Dr=R and D7El =rB, so the final formula is Dw "PBπR"vp p
bxRc” −D8+ pe・2πRDrH+Cpep
a) πR”DR+ D, 8--- @Totoru. Here, the crystal radius on the melt surface is R, and the height of the meniscus?H1
Thickness of liquid sealant? L, when the surface tension is 18, the amount of change per unit time is hDr, DR, D6, respectively.
, Drs, and the effective growth rate of the crystal taking into account the decrease in the melt surface was vp. Furthermore, since the effective weight change amount 11wc corresponds to ρgfR”vp, from equation 0, Dwc ”Dw + PbπRc”De Pe2π
RDrH−(ρ0−ρ8)πR”DhDAB
””■. Here, ρbπRc2De is the buoyancy correction term (pe-ps) π
R”Dh corresponds to the reverse response correction term, Dγ8 corresponds to the surface tension correction term of the melt, and -ρe 2 r Rn rB corresponds to the correction term for the influence on the amount of weight change caused by the presence of a meniscus.Crystal shape First, the effective grown crystal length 2 is determined in the calculator 12.If the initial thickness of the liquid sealant is iLo and the elapsed time after the start of pulling is t, then 2 is given by the measured weight Wh.Also, the crystal radius R is determined by the measured weight Wh. Weight change jlDw
It is obtained from the formula
) used to calculate we. The crystal diameter memory 22 stores the crystal diameter ? generated by the crystal shape calculator 12. Remember and B! 0. Find the diameter of the upper crystal. Furthermore, the differentiator 23
And Dr? Then, from these values, the meniscus shape calculator 24 calculates the height of the meniscus etc. Calculate and use the blade surface tension calculator 25 to determine the surface tension γ8 i? calculate. Based on the above numerical values, the correction amount calculator 11 calculates the effective weight change amount DWC per unit time. In the target value calculator 15, from the target crystal shape generator 14,
Effective growth rate Vpref obtained by crystal shape calculator 12
The target effective weight change amount Dwref is calculated according to the k-th equation. Dvref = Rref on the 2nd” Vpref
” ” -'The controller 17 calculates wre from the effective weight change amount I'vc and the target effective weight change i.
Based on the deviation size from f, digital PID iI''
lI controlled speed algorithm? The amount of change 'rp per unit time in the temperature of the heater used to adjust the temperature of the melt is calculated by using the temperature programmer 18, and the data is sent to the temperature programmer 18. send. In crystal growth using the Czochralski method, the crystal is grown with a constant diameter Jt, and if the solidification heat accompanying the growth is constant; Therefore, the temperature of the heater that completely heats the melt must be gradually lowered.In other words, with a constant diameter and a constant growth rate, the temperature change of the heater will also be constant when the crystal is growing.Therefore, the unit It is more desirable to control the amount of temperature change τpt of the heater per hour.Furthermore, rather than controlling the temperature TH of the heater itself, it is better to control the temperature change per unit time jiTpk determined by the differentiator 21. Is this a sudden change in melt temperature?
It can be prevented. As a result, there is a small possibility that instantaneous fluctuations in crystal diameter will occur, which has the effect of making it difficult for reverse response phenomena to occur. [Example] A GaAs single crystal, which is one of the ■-■ group compound semiconductors, was manufactured by the method of the present invention. PBN crucible aA with inner diameter of 154m and depth of 140cm
s polycrystalline raw material at 4000F, liquid sealant E, o
, 6002, and pressurized nitrogen gas into the high-pressure container.
After about 30 hours of pressurization, the sealant and crystal system $-+ were completely melted by heating, and then the seed crystal was brought into full contact and pulling was started. Rotate the pulling shaft 5 times per minute and rotate the crucible in the opposite direction once per minute.
At a speed of 0 to 9 rotations/hour, the straight body diameter is 60
Crystals that are cod? When a crystal was pulled using the method of the present invention as a target crystal shape, it had a length of about 29 mm after about 30 hours.
A GaAs single crystal with a weight of 32001 was obtained. The target crystal shape and the actually pulled crystal shape in that case are shown in FIG. As shown in the figure, a crystal having a shape almost identical to the target crystal shape is pulled up, and when it reaches the body, the crystal diameter is 60 mm, which is very well controlled. FIG. 7 shows the shape control contents displayed on the CRT 13 in this implementation sequence ζ. In addition, under the same growth conditions as above, 6ooor of GaA3 polycrystalline raw material was introduced and the target crystal shape was pulled up. After about 18 hours, GaA3 with a length of about 22 erm and a weight of abaoy was pulled. A single crystal was obtained, and the results are shown in FIG. 6. As in the previous example, a crystal having approximately the same shape as the target crystal was pulled.
In the trunk, the crystal diameter is very well controlled to 90±1.5 cm. In the above GaAs single crystal pulling process, even if the conditions such as the pressure, the rotation speed of the pulling shaft and crucible, and the crystal pulling speed are changed, a crystal having the same shape as the target crystal shape can be obtained as in the above-mentioned example. Even when a magnetic field was applied during crystal growth to suppress the convection of the raw material melt, a crystal having the same shape as the target crystal shape was obtained, as in Example 1 above. Note that the present invention is not limited to the Doi matrix, but can be similarly applied to a single crystal production method using the liquid-filled Czochralski method, including [+1-V group compound semiconductor single crystals]. [Effects of the Invention] As explained above, when a single crystal is manufactured using the crystal shape control method according to the present invention, the ■-■ group compound semiconductor single crystal growth (/ !: A single crystal with the desired shape from the 1M section to the straight body section and the tail section can be obtained automatically and with good reproducibility.As a result, high-quality crystals can be manufactured with good yield, and further savings can be made. This has the effect of humanizing it.

[Brief explanation of drawings]

FIG. 1 is a block diagram explaining the present invention in detail, FIG. 2 is a diagram showing the vicinity of the crystal-melt interface during crystal growth, and FIG.
Figures 4 (&) and (b) are explanatory diagrams of the meniscus at the crystal-melt interface, and Figures 5 and 6 are the diameter of the target crystal shape and the actual growth in Example 1 of the present invention. FIG. 7 is a graph showing the relationship with the diameter of the Kusaku crystal, and is a diagram showing one row of control-related information displayed in real time on the CRT screen.

Claims (1)

[Claims] (1) In a method for manufacturing a III-V compound semiconductor single crystal using the liquid-sealed Czochralski method, the buoyancy due to the liquid sealant, the reverse response to the measured weight change per unit time,
The control amount is the value obtained by adding in real time a correction amount based on the surface tension due to the melt, the amount of influence on the amount of weight change due to the presence of a meniscus, or a combination thereof, and the reference weight per unit time corresponding to the target crystal shape. I characterized by adjusting the amount of change in heater temperature per unit time so that the amount of change is a set amount and the controlled amount is the set amount.
A method for producing a II-V group compound semiconductor single crystal.