JPS61205697A - Single crystal growth system for group iii-v compound semiconductor - Google Patents

Abstract

PURPOSE:In the title crystal growth system by the liquid-sealed Chokralsky method, the melt of groups III-V is weighed to calculate the dissipation loss of the volatile element from the measurement and the loss is fed to prevent the crystal lattice from being defected. CONSTITUTION:Chemically equivalent amounts of Ga and As are melted with heat in a crucible and the single crystal of GaAs 9 is allowed to grow by the liquid-sealed Chokralsky method. At this time, the dissipation loss of As in the direct synthesis of GaAs is known from the indication of the melt weight sensor 1 and the loss of As in the crystal growth is calculated with the computer 5 from the values 3, 4 from the melt weight sensor 1 and the crystal weight sensor 2. Then, As corresponding to the dissipation loss is fed by heating the As feeder 8, as the vapor pressure of As is controlled. Thus, the single crystal of 9 is allowed to grow, as the melt of GaAs 11 is controlled in its composition.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a crystal pulling apparatus for producing compound semiconductors containing volatile elements by the liquid-sealed Ralski method, and in particular, ■The stoichiometric composition of the group is 1
This relates to a device for pulling up while maintaining a ratio of 1 to 1.

[Conventional technology]

Recently, high-quality crystals of m-v group compound semiconductors have become available, and they have come to be widely used in integrated circuits, opto-electronic integrated circuits, materials for electronic devices, and the like. ■-Among V group compound semiconductors, gallium arsenide (GaAs) has high electron mobility, is easy to emit light, and can detect light.It is used in microwave transistors, high-speed integrated circuit solar cells, It is becoming widely used as an element material.

In order for a GaAs single crystal to be used as a substrate for the above-mentioned integrated circuit, it must have semi-insulating properties with a specific resistance of 107 Ωam or more, and must be a high-quality single crystal free of physical and chemical defects such as dislocations and lattice defects. It is required to be crystalline and to have good heat treatment characteristics.

In particular, dislocations and lattice defects affect the characteristics of integrated circuits and cause a reduction in yield. In recent years, Irejik! (In)? Although it has become possible to obtain dislocation-free crystals by adding and hardening the crystal, many lattice defects still exist in the crystal, and the yield of integrated circuits has not reached a practical level, so it is necessary to reduce the lattice defects. This has become a major technical problem for the commercialization of GaAs integrated circuits.

[Problem that the invention seeks to solve]

This lattice defect is caused by the fact that the stoichiometric compositions of group (I) and group V elements are different in the crystal. ■-In Group V compound semiconductors, Group V elements are more volatile than Group ■ elements.
In crystal growth using the Chirari Ralski method, the melt is pulled through a liquid sealant (boron oxide, B2O2).
However, the volatile elements of group V are scattered through this liquid sealant, and the stoichiometric composition in the crystal changes as the solidification rate increases. ■
It is normal for the group elements to shift to an excessive state, and conventional LEC technology cannot take any measures against this problem.

An object of the present invention is to provide an apparatus for growing a single crystal of a compound semiconductor of the 1-2 group with extremely few lattice defects by the LEC method.

[Means for solving problems]

The present invention uses an apparatus for growing compound semiconductors using a liquid confinement method, in which the weight of the melt is measured, the amount of scattered group V volatile elements is automatically calculated using a computer, and the amount of group V elements corresponding to the scattered amount is calculated. It is characterized by having the function of injecting into the melt.

〔Example〕

Examples will be described in detail below.

An apparatus according to one embodiment of the present invention is shown in FIG.

This device consists of two crystal weight sensors. Melt weight sensor 1.
Devices 7 and 8 for injecting group III elements into the melt using a heating method
．． In addition, receiving signals 3.4 from each weight sensor 1.2■
It consists of a computer 5 that automatically calculates the amount of the group element to be implanted. L.E.
CGaAs is often grown by direct synthesis. The scattering of As during direct synthesis can be determined by reading the indicated value of the melt weight centimeter (Ruri weight sensor) 1.

-10,000, the amount of scattering during crystal growth is 3.4, which is the value of each of melt weight sensor (crucible weight sensor) 1 and crystal weight sensor 2.
It can be obtained by inputting all four data into the machine 5 and correcting the tension at the interface between the melt and the crystal. As equivalent to the amount of scattering thus obtained is injected into the melt 9 by heating the heater part 7 of the arsenic injection device 8 and controlling the vapor pressure of As. This process is carried out automatically during crystal growth.
It is possible to grow a crystal that satisfies the stoichiometric composition over the entire pulled crystal. In addition, the nozzle of the injection device is
Since it is made of PBN, there is no contamination with impurities.

Next, we will show the effects of nine GaAs wafers manufactured using this equipment.

A 4-inch-diameter PBN roll was charged with 2Kf of Ga, 2Kf of chemical equivalents of gold, and 300g of B20st'.

The atmospheric gas used was argon, and the pressure during direct synthesis was 75
The pressure during crystal growth is 10 Kf/-.

Under these conditions, a crystal with a diameter of about 55
A GaAs monolayer with a fi length of 100 cm was fabricated.

The number of As skipped at this time detected from the weight sensor l on the F axis is the song lI in Figure 2! As shown in Fig. 16, the amount of scattering during direct synthesis was approximately 25 g, and 54 g at the end of crystal pulling.

10,000, Crystal B was grown using the same growth method as the crystal man except that arsenic was injected in an amount equivalent to the arsenic scattered by this device. Nine wafers were cut vertically from these crystals, including the center of the crystal, and the stoichiometry in the axial direction was measured.
Changes in the values were measured by the X-ray quasi-forbidden reflection method. The results are shown in FIG.

Curve 17 is the case using the conventional method, and curve 18 is the case using the present apparatus. In this way, the compositional deviation of the crystals grown while performing single-person S implantation and controlling the composition is extremely small - 0 Furthermore, FET'i was fabricated using the wafer on which each pulled crystal was subjected to X-ray evaluation and the adjacent wafer, and the device was We investigated the variation in characteristics. The FET pattern used had a gate length of 2μ, a gate width of 100#m, and a source-drain distance of 6μ. Change in threshold voltage vth'
ill! Shown in Figure 4. Curve 19 is based on the conventional example and is 1
Curve 20 is from this device. As shown in this figure, crystal B grown by controlling the composition has a vt in the direction of the pulling axis.
The variation in h is extremely small.

Using a similar pattern, cut 9 pieces into the pulling shaft (
100) The variation in Vth of wafers was also investigated. As a result, as shown by curve 21 (conventional method) and curve 22 (this device) in FIG. 5, it was revealed that crystals grown with controlled composition had extremely little variation within the vthO plane.

〔Effect of the invention〕

By using the apparatus according to the present invention as explained above, it is possible to obtain a crystal whose composition is controlled, and by fabricating an FET on a wafer obtained from this crystal, an FET with almost no variation in characteristics can be obtained, and a GaAs IC =j- has the effect of increasing integration. In addition, the present invention is applicable to
-■ group compound semiconductor GaP InP is also considered to be effective for the same reason.

[Brief explanation of drawings]

w, Figure 1 is a vertical cross-sectional view of an apparatus according to an embodiment of the present invention, and Figure 2 is a diagram showing the relationship between the amount of arsenic scattered and the crystal growth time obtained by computer processing the crucible weight sensor signal according to the present invention. Figure 3 is a diagram showing the relationship between deviation from stoichiometry due to XIW quasi-forbidden reflection and crystal length, l! Figure 4 shows the relationship between FET threshold voltage vth and crystal length.
FIG. 5 is a diagram showing how the threshold voltage vth varies within the wafer surface. 17, 19.21 are characteristic diagrams for conventional crystals, and 18, 20.22 are characteristic diagrams for crystals produced by the present device, respectively. ψ1 times 11-? -＋P11 (Mema) Sei 2nd edition

Claims (1)

[Claims] In a III-V group compound semiconductor single crystal growth apparatus using the liquid-filled Czochralski method, the weight of the III-V group melt is measured, and the amount of volatile elements scattered is calculated from that value, and the amount equivalent to the amount of scattering is calculated. 1. An apparatus for growing a single crystal of a III-V compound semiconductor, characterized by having a function of injecting a certain amount into the melt.