JPH04131368A - Formation of thin germanium film - Google Patents

Abstract

PURPOSE:To laminate a thin Ge film having high crystallinity on an Si substrate by forming a thin Ge film on the surface of Si with a Te and/or Se layer in-between. CONSTITUTION:A thin Ge film is formed on the surface of Si with a Te and/or Se layer in-between. The Te and/or Se layer is not especially restricted but it is preferably formed in the thickness of a monoatomic layer or below because a thick Te and/or Se layer is liable to make the surface of the Ge film rugged. A laminate useful as an Si/Ge heteroepitaxial film can be formed.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides germanium (Ge) on a silicon (Sl) surface.
The present invention relates to a method of forming a thin film. The method of the present invention can be applied to silicon/germanium (Sf/G), which is useful as a semiconductor material, for example.
e) It can be used in the production of thin films.

[Conventional technology]

Currently, silicon (Sl) is the main semiconductor material, but
With the development of the semiconductor industry in recent years, semiconductor materials are now required to have advanced properties that were not previously available.
New materials are being actively researched. One type of such material is a St,/Ge based thin film. Si/Ge
Thin films of this type exhibit electrical and optical properties that cannot be obtained with Si alone, and are attracting attention as SL+-x Get /st sSt/Ge superlattice devices, as well as GaAs films, which are considered as next-generation semiconductor materials. It is also a promising material as a substrate material.

By the way, when a Ge thin film is formed on a St surface by a conventional method, such as molecular beam epitaxy (MBE), the layer has a smooth surface up to a certain thickness (approximately 6 atomic layers). Formed sequentially (so-called 1ayer)
by 1ayer) o However, St and Ge
Since there is a 4% lattice mismatch in G
When e-thin films are formed by stacking up to more atomic layers,
There is a problem in that the Ge thin film is formed in the form of islands that are not smooth, which is considered to be inconvenient in obtaining a good heteroepitaxial structure.

[Challenges to be solved by the invention @] An object of the present invention is to provide a method for forming a Ge thin film with a smooth surface even when a polyatomic layer of Ge thin film is formed on the S1 surface. .

[Means for Solving the Problems] As a result of intensive research in order to solve the above problems, the present inventors found that after forming a tellurium (Te) and/or selenium (Se) layer on the surface of 81, Ge By forming a thin film, the present invention was completed by discovering that a Ge thin film can have a smooth surface even if it is formed to, for example, six atomic layers or more as described above. That is, the present invention is a method for forming a Ge thin film on the surface of 81, which is characterized in that the Ge thin film is formed via a Te and/or Se layer.

Next, the present invention will be explained in more detail.

In the method of the present invention, a Te and/or Se layer is provided on the Sj surface, and a Ge thin film is formed via this Te and/or Se layer. The Te and/or Se layer at this time is not particularly limited, but if the thickness of the Te and/or Se layer is increased, the surface of the resulting Ge thin film may exhibit an uneven structure, so it is less than one atomic layer. It is preferable to form it as a layer. Further, the formation of this layer is preferably carried out at a substrate temperature at which the Te and/or Se layer does not re-evaporate and under high vacuum where other elements are not adsorbed. Furthermore, Te and/
Alternatively, the Ge thin film formed via the Se layer can be formed by a conventionally known method. For example, the Ge thin film can be formed by a method known in the art.
It can be formed by the B2 method or the like.

As described above, in the present invention, Te and/or Se
Forming a Ge thin film on the 84 surface via a layer means forming a Ge thin film in the presence of Te and/or Se at least on the 84 surface. It also includes moving Te and/or Se from the Te and/or Se layer present on the surface of the formed Ge thin film, and further laminating a Ge thin film on the surface of the Ge thin film. That is, according to the observations of the present inventor, it is clear that when a Ge thin film is formed on the 81 surface via a Te and/or Se layer, Te and/or Se always migrate to the surface of the Ge thin film. It became. It is presumed that this transferred Te and/or Se acts as a "catalyst" to form or stack the 100 thin film as a thin film with a smooth surface without an island shape, as described above.

Note that the Ge thin film obtained by the method of the present invention was confirmed to be a highly crystalline single-crystalline film by observation of low-energy electron diffraction (LEED), and is useful as a 5ilGe-based heteroepitaxial film.

[Effects of the Invention] The method of the present invention makes it possible to deposit a highly crystalline Ge thin film on a St substrate, which has not been possible in the past.

[Example] Next, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited thereto.

Examples and Comparative Examples Using the S1 substrate, Te was vapor-deposited on it by the MB2 method using a cell to form a one-atomic layer of Te, and then Ge was vapor-deposited on the Te layer to form a Ge thin film. Formed.

For comparison, we also deposited Ge directly on the Sj substrate without using the Te layer.
An example in which a Ge thin film was formed by vapor deposition is also shown. The conditions for vapor deposition are as follows.

・Ultimate vacuum level: 1. OxlO-' Pa, substrate: p-type 5i (001), substrate temperature = 2
70℃ ・Vapor deposition rate: IA/mjn(Te), 4A/
1ljn(Ge)・Film thickness measurement: Quartz crystal oscillator method Note that Ge deposition was performed until the Ge thin film had a thickness of 30 mm.

The surface structure of the Ge thin film obtained as described above was examined using a scanning electron microscope (acceleration voltage: 20 kV, 100,000 times).
When observed, the surface of the Ge thin film obtained in the example had a smooth surface as shown in the photograph of FIG. On the other hand, the surface of the Ge thin film obtained in the comparative example had irregularities as shown in the photograph of FIG.

Furthermore, Ge thin films having various thicknesses obtained by the method of the present invention were analyzed using the measurement method shown below. The measurement conditions are as follows.

Reflection high-speed electron diffraction (RHEED) Equipment used: RHG-01 manufactured by ULVACP1
・Accelerating voltage: 20kV Low-speed electron diffraction (LHHD) ・Equipment used: 15-12 manufactured by LILVACP1
0 Auger electron spectroscopy (AES) ・Equipment used 2 JAMP-30 manufactured by JEOL Ltd. ・Electron beam acceleration voltage: 3kV ・Ion gun acceleration voltage: LkV As a result of the above analysis, from the RHEED results, it was found that on the 5i (001) surface In the RHE ED pattern of the directly formed Ge thin film with a thickness of 30 nm, the diffraction lines were spot-like, and the pattern corresponded to an island-like structure. On the other hand, a thickness of 30A formed through Te
In the RHEED pattern of the Ge thin film, the diffraction lines were streaks, and this revealed that the Ge thin film was grown two-dimensionally, including atomic layer steps.

From the LEED results, it was found that the spots of the Ge thin film formed through Te were clear and the crystallinity was good.

Furthermore, as mentioned above, scanning electron microscopy images clearly show that the surface of the Ge thin film formed directly on the Si surface has an uneven structure, whereas the surface of the Ge thin film formed via Te has a rough structure. These uneven structures are not observed. This is 8
In the Ge thin film formed directly on one substrate, the crystals grow in an island shape (three dimensions), and in the Ge thin film formed via Te, the crystals grow in two dimensions, which is in good agreement with the RHEED results obtained.

Furthermore, from the results of depth direction analysis by AES of a Ge thin film formed with a thickness of 200 mm on a St substrate via Te, it was found that T
It was found that e exists not at the interface between the St substrate and the Ge thin film, but on the surface of the Ge thin film. Furthermore, similar results were obtained even when the thickness of the Ge thin film was changed, and from this it was inferred that Te moved to the surface of the Ge thin film and acted on it.

[Brief explanation of the drawing]

FIG. 1 is a scanning electron micrograph showing the grain structure of the surface of a Ge thin film formed in an example of the present invention. FIG. 2 is a scanning electron micrograph showing the grain structure of the surface of the Ge thin film formed in the comparative example.

Claims (1)

[Claims] A method for forming a germanium thin film on a silicon surface, the method comprising forming a germanium thin film through a tellurium and/or selenium layer.