JPH0450280B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a -V compound crystal and a method for pulling the same.

Integrated circuits (hereinafter abbreviated as ICs) based on -V compounds are attracting attention as ICs for high-speed operation. However, GaAs, which is attracting attention as a material,
-V compound crystals such as InP are not of sufficient quality.
High densities of 10 ⁴ to 10 ⁶ cm ^-2 are commonly observed. These dislocations, which can be easily observed as etch pits, are considered to be a major cause of not only the variation in characteristics between elements required when manufacturing ICs, but also the reliability of the IC.

Undoped pulled crystals (hereinafter abbreviated as LEC crystals) have recently attracted particular attention as substrates for GaAs ICs. Various measures have been taken in various places to reduce the dislocation density in the crystal, but at present there is no prospect of improvement.

The main reason for the introduction of dislocations into LEC crystals is that the lifted crystal part is rapidly cooled and thermal strain is induced on the surface. In Si, it has been found that dislocations can be significantly reduced by providing a heater to heat the pulled-up crystal part, which is called an after-heating method, and relaxing the temperature gradient at the pulled-up crystal part. But-
The V compound undergoes severe thermal decomposition, and the after-heating method cannot be used easily.

The present invention provides a crystal structure and crystal pulling method that can significantly reduce crystal dislocations.

The first gist of the present invention is grown from a solution.
This is a crystallization method characterized by immediately attaching -V compound crystals with stronger crystal energy to the surface of V compound crystals. It is sufficient to introduce a reactive gas containing a group of 2 or a group of V or both into the exposed atmosphere of the exposed crystal. The second is the structure of a -V compound pulled crystal whose surface is covered with a -V compound having stronger binding energy than that of the grown crystal by using the first method, for example.

Now, the method for pulling a -V compound crystal and the structure of the pulled -V compound crystal of the present invention will be explained in detail based on Examples. As an example, a case where an undoped GaAs crystal is manufactured by a pulling (LEC method) method will be described.

FIG. 1 is a conceptual diagram when pulling up GaAs. Ga and As are placed in approximately equimolar amounts in a boron nitride crucible 11, and then covered with B ₂ O ₃ 12, the melting point is 1238°C.
A melt 13 of Ga and As is made by heating to a certain degree, and a seed crystal 14 is brought into contact with the melt 13, and the seed crystal 14 or the crucible 1 is
When the seed crystal 14 is pulled up away from the solution 13 while rotating 1 (or rotating both), GaAs
Crystals 15 are pulled up from the solution 13. The lifted GaAs crystal 15 emerges from the B ₂ O ₃ solution 12 and is rapidly cooled. At this time, the GaAs crystal 15 undergoes rapid thermal strain and dislocations are introduced from the surface. However, in the embodiment of the present invention _{, trimethyl} aluminum (hereinafter referred to as
It is abbreviated as TMA. ) or triethyl aluminum (hereinafter abbreviated as TEA). In Figure 1, 17 indicates the stainless steel pipe into which TMA and TEA are introduced. By doing this, the surface of the GaAs crystal 15 that has been pulled up becomes Al and
Due to Ga substitution reaction, Al _x Ga _1-x As layer 18 is formed immediately.
is formed. When a concentration of TMA or TEA of about 0.01% is added to the chamber 16 (however, the pressure in the chamber 16 is set to 5 to 30 atmospheres with argon or nitrogen gas), x of the Al _x Ga _1-x As layer 18 is
It was around 0.3 to 0.5. Of course TMA or
As the concentration of TEA increases, x increases. The thickness of the AlGaAs layer 18 on the surface of the pulled GaAs crystal 15 is 5 to 100 μm, which is a small thickness since the pulled GaAs crystal 15 has a diameter of about 5 cm. However, when the pulled GaAs crystal 15 was cut into a wafer shape and the etching pit density was counted, it was found to be less than 10 ³ cm ^-2 over the entire crystal, and the dislocation density was reduced by more than an order of magnitude. This is AlGaAs
The bonding energy of the layer 18 is greater than that of the GaAs crystal 15, so thermal decomposition is less likely to occur, and since the bonding energy is large, even if sudden thermal strain occurs, the crystal is strong and prevents the introduction of dislocations from the surface. This is thought to be due to the i.e. TMA or
By being lifted into a room containing TMA gas.
The surface of the GaAs crystal 15 exposed from the B ₂ O ₃ solution 12 is immediately covered with the AlGaAs layer 18 which has high bonding energy and strong mechanical strength, reducing the introduction of dislocations due to thermal strain and reducing the temperature to 10 ³ cm ^-2 or less. low dislocation of
It was shown that GaAs pulled crystals can be obtained.

In the above explanation, the surface layer 18 is made of AlGaAs, but of course, when the pressure of As is applied to the chamber 16, the AlGaAs 18 is formed on the surface of the GaAs crystal 15 rather than the gas phase of TEA or TMA and As in the chamber 16. It accumulates and becomes thicker. Similarly, TEM and
If NH ₃ is supplied into the chamber 16 instead of TMA, a GaN layer is formed on the surface, which also has the effect of reducing the dislocation density. However, stable gases such as N ₂ gas have no effect. Furthermore, the present invention
It is clear that the increase is not limited to InP.
When pulling up NH _{3 , NH 3} is introduced into the chamber 16, an InN layer is formed on the surface layer 18, and the dislocation density is reduced, and it is clear that this method can be applied to all -V compound crystals.

Furthermore, in the above example, a method was shown in which the surface of the pulled crystal was covered with a crystal layer in which the group or V group constituting the -V compound semiconductor was replaced.
Use borazole in room 16 for pulling up crystals, etc.
Forming a BN layer as a surface layer is also effective in reducing dislocations. As is clear from the above explanation, the pulled crystal surface layer does not necessarily need to be a pulled crystal or one with lattice matching. Furthermore, although the LEC method has been described in the above embodiments, other methods such as the HB method are also effective.

[Brief explanation of the drawing]

FIG. 1 shows a conceptual diagram when pulling a -V compound crystal. In the figure, 11 is a boron nitride crucible, 12 is B ₂ O ₃ , 13
is a melt consisting of Ga and As, 14 is a seed crystal, 15 is a pulled GaAs crystal, and 16 is a pulled GaAs crystal.
A room in which the GaAs crystal is exposed, 17 a stainless steel pipe for supplying a gas containing group or V group or both for achieving the present invention, 18 a
AlGaAs crystal layer.

Claims (1)

[Claims] 1. In a pulled crystal of a -V compound, the exposed surface has a larger binding energy than that of the crystal.
It is characterized by being covered with a V compound.
V compound pulled crystal. 2. In a crystal growth method in which a seed crystal is brought into contact with a solution containing at least an element constituting the crystal, and the crystal is precipitated on the seed crystal, the crystal is exposed to an atmosphere that is pulled up from the solution phase, and between the crystal and the crystal. 1. A method for pulling a -V compound crystal, which comprises introducing a reactive gas containing at least one of an element or V element to form a -V compound having a larger binding energy than the crystal.