JPH0234916B2 - BUNSHISENEPITAKISHARUKETSUSHOSEICHOHO - Google Patents

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to molecular beam epitaxial (hereinafter MBE)
The present invention relates to a crystal growth method (described as ), and particularly relates to a method of heating a substrate when performing molecular beam epitaxial crystal growth.

(Prior art) GaP, InP, etc., which are compound semiconductors of the - group,
When growing epitaxial crystals on a GaAs substrate by the MBE method, conventionally, as shown in Figure 2, first a Mo block 2 for the purpose of holding the substrate 1 is grown.
Heat it to about 200℃ in an _N2 atmosphere, melt In3 on Mo block 2, and place substrate 1 on top of it.
Glue Mo block 2 and substrate 1. Then the second
As shown in the figure, the substrate 1 and the Mo block 2 are introduced into an ultra-high vacuum container 4, and the substrate 1 is heated by radiation from a heater 5 made of tantalum or the like from the back side of the Mo block 2 in the ultra-high vacuum. A desired molecular beam is generated from a molecular beam source 6 placed in front of the substrate to grow epitaxial crystals on the surface of the substrate 1. this
The Mo block 2 efficiently absorbs radiant heat, thereby uniformly heating the substrate 1. After epitaxial crystal growth, the substrate 1 and the Mo block 2 are taken out of the vacuum chamber and heated again to about 200° C. in an N ₂ atmosphere to melt the In and separate the substrate 1 and the Mo block 2.

When MBE crystal growth is performed using the above method, the adhesion and separation steps between the substrate 1 and the Mo block 2 must be performed manually, which is inefficient. Also, In
3 and substrate 1 often cause an alloy reaction, so even if In3 is removed from the back side of substrate 1, several alloy layers remain.
It is formed to a depth of 10 μm. This alloy layer is very non-uniform, brittle and uneven, giving rise to many problems when processing this substrate 1 to form devices. Therefore, until now, this alloy layer has been removed by polishing.

(Object of the invention) The object of the present invention has been made to address the above-mentioned drawbacks, and it is possible to
An object of the present invention is to provide a molecular beam epitaxial crystal growth method that can efficiently and uniformly heat a substrate directly in a vacuum using radiation from a heater.

(Structure of the Invention) The molecular beam epitaxial crystal growth method of the present invention includes:
In the molecular beam epitaxial crystal growth method, in which a crystal component is incident on the surface of a substrate heated in an ultra-high vacuum and epitaxial crystal growth is performed on the surface of the substrate, a metal film is deposited on the back surface of the substrate in advance and then epitaxially grown. The present invention is characterized in that the metal film is directly heated by thermal radiation during the growth of the crystal, and the substrate is heated by heat conduction from the metal film.

In addition, the present invention can exhibit its characteristics when the substrate is GaAs, InP, or GaP.
Furthermore, the effect can be more effectively achieved by using any one of Mo, W, and Ta as the metal film.

(Function) In the present invention, a high melting point metal film is formed on the back surface of a substrate by a sputter deposition method, etc., and this metal film is heated in vacuum by radiation from a heater such as tantalum. conducts heat to the substrate to heat the substrate.

If there is no metal film on the back side of the substrate, in the case of a semiconductor substrate with a bandgap of about 1.3 eV or more at room temperature, the absorption coefficient of the substrate at the peak wavelength of the spectrum of the radiation wavelength from the heater is small and the substrate cannot be heated efficiently. Moreover, if the thermal conductivity of the substrate is low, it is difficult to uniformly heat the entire substrate.
Therefore, a temperature difference occurs within the plane of the substrate, making it impossible to achieve uniform crystal growth.

However, by forming a high melting point metal film on the back surface of the substrate, the radiation from the heater is efficiently absorbed, and since the metal film itself has high thermal conductivity, the substrate can be uniformly heated. Moreover, the alloy reaction between the substrate and the high melting point metal hardly occurs at the epitaxial crystal growth temperature of about 600°C. Therefore, extreme unevenness does not occur on the back surface of the substrate. In addition, if it is necessary to remove the high melting point metal film from the back side of the substrate after epitaxial crystal growth, CCl ₄
It can be easily removed using gas plasma etching methods such as .

(Example) Next, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a conceptual diagram for explaining one embodiment of the present invention. As shown in Figure 1, the residual gas pressure inside the ultra-high vacuum vessel 4 is maintained at about 10 ^-10 Torr.
Inside it, use the spatuta deposition method to place Mo on the back side.
A GaAs single crystal substrate 7 on which a film 8 of about 2000 Å is deposited is introduced. While As is incident on the surface of the GaAs single crystal substrate 7 from the As molecular beam source 9, the back surface of the GaAs single crystal substrate 7 is heated by radiation from the tantalum heater 5. At this time, the radiation of tantalum heater 5 is Mo
The light enters the Mo film 8 and first heats the Mo film 8. GaAs single crystal substrate 7 is then heated by thermal conduction. The power of the tantalum heater 5 is adjusted so that the surface of the GaAs single crystal substrate 7 is heated to about 600°C.

After confirming by reflection electron beam diffraction that Ga oxide and As oxide have been thermally removed from the surface of the GaAs single crystal substrate 7, the Ga molecular beam source 10 is
When Ga is incident on the surface of the GaAs single crystal substrate 7,
A GaAs epitaxial crystal is grown. At this time, As continues to be incident on the surface.

After epitaxial crystal growth, from growth chamber 4
The GaAs single crystal substrate 7 is taken out, a photoresist is spin-coated on the front surface to protect the epitaxial crystal, and the Mo film 8 on the back surface is removed by plasma etching with a mixed gas of CCl ₄ and O ₂ to polish the back surface. There is no need to flatten the surface.

Moreover, using In3 for Mo block 2, substrate 1
However, in the case of the present invention, in the case of the present invention, the process of depositing and removing the Mo film 8 on the substrate is all performed automatically for many sheets at once. is possible.

Furthermore, when transporting the substrate 1 in a vacuum container,
It is easier to transport only the substrate 1 than to use the Mo block 2.

Although this embodiment has been described using Mo as the high melting point metal and GaAs as the substrate, it is clear that similar effects can be obtained with Ta and W as the former, and with InP and GaP as the latter.

(Effect of the invention) As explained above, according to the present invention, conventional
Efficiently and uniformly in vacuum without using Mo blocks and In, which are problems with the MBE crystal growth method.
Furthermore, it is possible to easily heat the substrate, and excellent molecular beam epitaxial growth can be performed.

[Brief explanation of drawings]

FIG. 1 is a conceptual diagram for explaining one embodiment of the present invention, and FIG. 2 is a conceptual diagram for explaining a conventional molecular beam epitaxial crystal growth method. 1...Substrate, 2...In, 3...Mo block,
4... Ultra-high vacuum container, 5... Heater, 6... Molecular beam source, 7... GaAs single crystal substrate, 8... Mo film,
9...As molecular beam source, 10...Ga molecular beam source.

Claims (1)

[Claims] 1. In a molecular beam epitaxial crystal growth method in which crystal constituent elements are incident on the surface of a substrate heated in an ultra-high vacuum and epitaxial crystal growth is performed on the surface of the substrate, Molecular beam epitaxial crystal growth characterized in that a metal film is deposited on a substrate, the metal film is directly heated by thermal radiation during epitaxial crystal growth, and the substrate is heated by heat conduction from the metal film. Law. 2. The molecular beam epitaxial crystal growth method according to claim 1, wherein the substrate is GaAs, InP, or GaP. 3. The molecular beam epitaxial crystal growth method according to claim 1 or 2, wherein the metal film is made of Mo, W, or Ta.