JPS62196815A - Thin-film growth device - Google Patents

Abstract

PURPOSE:To increase a growth rate without elevating the temperature of a substrate by irradiating the substrate by ultraviolet rays and conducting molecular-beam epitaxy (MBE) through the irradiation of molecular beams of a thin-film growth material from a molecular-beam source 2 under the state. CONSTITUTION:MBE constitution in which the molecular-beam source 2 of a thin-film growth material and the arranging section 4 of a substrate 3, to which a thin-film must be grown, are mounted into an ultra-high vacuum tank 1 evacuated by an ultra-high vacuum pump from an exhaust port 1A is formed. An ultraviolet-ray irradiation means 5 irradiating a surface, on which the thin- film is grown, of the substrate 3 by ultraviolet rays is provided. The substrate 3 is irradiated by ultraviolet rays, and MBE is performed through the irradiation of the molecular beams of the thin-film growth material from the molecular- beam source 2 under the state. A detecting means 6 detecting the reflected beams of ultraviolet rays from the surface of the substrate or the growth surface of the thin-film and deciding or observing the states of these surfaces is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention particularly relates to thin film growth materials for growing thin films of silicone, compound semiconductors, etc. by molecular beam epitaxy.

[Summary of the invention]

The present invention irradiates a substrate with ultraviolet rays when growing a thin film by molecular beam epitaxy, thereby making it possible to form a high-quality thin film at a high growth rate at a low growth temperature, and furthermore to prevent impurity doping. When this is done, the impurity activation rate is increased.

[Conventional technology]

Thin film growth technology is an important technology for the production of electronic devices, but the technology for epitaxially growing semiconductor thin films at low temperatures is particularly important because it essentially influences the characteristics of the device. Generally, devices are formed on a wafer-shaped substrate, so one of the basic technologies is a thin film epitaxy method on the wafer surface.

In this case, the size of wafers tends to increase over the years, and wafers with a diameter of 6 inches are already being used especially for Si. As the diameter of the wafer becomes larger as described above, it becomes extremely important to suppress the warping of the wafer by lowering the temperature at which the epitaxial layer is formed. To reduce the growth temperature,
It is known that the molecular beam epixy (hereinafter referred to as MBE) method is effective, but in order to achieve this with the conventional MBE method, taking Si as an example, the film growth temperature must be set to 5.
When the temperature is 00° C., in order to grow a thin film with good crystallinity, it is necessary to limit the growth rate to several nm/a+in or less. Therefore, at present, such a small growth rate cannot provide a practical epitaxy technique. Furthermore, it is known that the electrical activation rate of impurities doped to control conductivity rapidly decreases as the growth temperature decreases.For example, when the substrate temperature is 500°C, conventional MBE The activation rate of impurities obtained by this method, for example, the activation rate of 8s and B, is less than about 10%, and it is extremely difficult to increase it beyond this level.

[Problem that the invention seeks to solve]

The present invention makes it possible to form a high-quality thin film at a low growth temperature and with a high growth rate sufficient for industrial practical use, and also to increase the activation rate of doping impurities.

[Means for solving problems]

As shown in FIG. 1, the present invention has a starting vacuum chamber (1) that is evacuated from an exhaust port (IA) by an ultra-high vacuum pump, as in an energized MBE device. The MBE configuration is provided with a molecular beam source (2) for a thin film growth material and a placement section (4) for a substrate (3) on which thin film growth is to be performed. Ultraviolet irradiation means (5) for irradiating ultraviolet light toward the growth surface
will be established. Then, ζ ultraviolet rays are irradiated toward the °ζ group (3), and in this state >:'i IIQ from the molecular beam source (2)
MBIEi' is performed by irradiating the growth material with a molecular beam.

Furthermore, a detecting means (6) is provided for detecting the reflected light of ultraviolet rays from the substrate surface or the growth surface of the thin film to judge or observe the surface condition of these curves.

[Effect]

In the present invention, MBE is performed while irradiating ultraviolet rays, and by doing so, it is possible to increase the thickness of the thin film growth material, that is, the substrate (3). Even if the temperature is selected to be as low as, for example, 500° C., it is possible to grow a thin film with excellent crystallinity, that is, with a thin 11a formation rate that is low. This can be explained by the state model of unattached valence electrons, that is, dangling bonds, on the crystal surface that becomes the thin film growth surface of the substrate (3) shown in FIGS. 2A and 2B. In Figure 2, the Neo model shows (1) of the St substrate (3).
00) Shows the electronic bonding state of the surface due to the crystal layer, and the figure A
B shows a state where ultraviolet rays are not irradiated, and B shows a state where ultraviolet rays are irradiated. If no UV irradiation is performed, β
+) i The state of the crystal layer 111 of the substrate (3) placed in the air is such that at low radix temperatures, the white circles represent the valence electrons, and the arcuate solid line a represents the bonding state. It is thought that unbonded electrons in the vicinity of each other are bonded to each other, and the occurrence of unbonded dangling bonds as shown in the figure is extremely rare. Even when transported, the substrate (
It is difficult to grow B film crystals from the crystals of 3), and the growth rate becomes low. In contrast, when ultraviolet irradiation is applied with moderate energy and intensity, the surface-bound electrons absorb the ultraviolet light and are easily dissociated, resulting in many dangling bonds, as shown in Figure 2B. produces b. As a result, it seems that the Si atoms arriving at this surface easily form bonds with the Si atoms of the substrate (3) and crystallize, thereby covering the unbalanced crystals and allowing the crystals to grow at a high growth rate.

〔Example〕

Further, an example of the apparatus of the present invention will be explained in detail with reference to FIG. The substrate (3) is, for example, a wafer cut from a single crystal of Si, and the S1 thin film is subjected to MBE on this wafer. The arrangement part (4) of the board (3) is placed on the board (3).
The heater element (71, for example, resistance heating means) is configured to hold the substrate (3) and heat the substrate (3) to a required temperature.
), such as a liquid nitrogen shroud.

Then, facing the placement part (4) of this substrate (3),
An i-molecule radiation source (2) is provided. This Si molecular beam source (2
) is equipped with, for example, an electron beam heating device, a so-called E-gun, to generate a molecular beam of Si, which is a thin film constituent material. Cooling means (9), for example a liquid nitrogen shroud, are also arranged around this molecular beam source (2).

On the other hand, ultraviolet irradiation means (5) for irradiating ultraviolet rays U and V to the substrate (3) is provided. This ultraviolet irradiation-μ stage (5) includes, for example, a first window W that transmits ultraviolet light on the wall surface of an ultra-high air chamber (11) between the substrate placement section (4) and the molecular beam source (2). A light source (10) for ultraviolet rays U and V is placed outside the tank (11) optically facing the tank (11).
, for example a high-pressure mercury lamp. Also, this light source (
A reflection ff1 (21) is provided on the back surface of the tank (10).
11 is provided with an optical system M1 such as a reflecting mirror, and the ultraviolet rays from the light source (10) are effectively introduced into the tank (1) through the window W□ by the reflecting mirror (21), and the ultraviolet rays from the light source (10) are effectively introduced into the tank (1) through the window W□. Therefore, 1 (Q) is uniformly irradiated onto the 8 film growth surfaces of the substrate (3) on which thin films are to be grown.

Then, ultraviolet rays U were irradiated toward this substrate (3),
V, is successively grown on or on the surface of the substrate (3) (by ultraviolet light reflected from the thin film surface).
3) or the surface state or crystalline state of the grown WIt film, so-called ultraviolet detection means (6) for in-situ observation.
) will be established. This means (6) is, for example, P! 1111)
Opposed to the second window w2 that transmits ultraviolet rays provided on the wall of the tank (1), a window W that transmits the reflected light of ultraviolet rays from the substrate (3) into the tank (1).
2, a monochromator (11) that receives ultraviolet rays that arrive outside the tank (1) through the window W2, a photomultiplier (12), and signals from these. For example, spectrum analysis of ultraviolet light reflected from the surface of the substrate (3) is performed. This means (6)
For example, this is for measuring the interaction between ultraviolet light incident on the surface of the substrate (3) and valence electrons on the surface of the substrate or the surface of a thin film. Comparative measurement according to (13) makes it possible to observe the surface state or crystalline state of the grown thin film in situ. By the device of the present invention
, a Si substrate (3) cut out along the (111) crystal plane.
) When performing MBE on Si, the substrate temperature should be raised to 500°C.
The temperature was set at 550°C, and the intensity of ultraviolet light incident on the surface of the substrate (3) was set at 80 to 120°C using a high-pressure mercury lamp having a peak at 31 nm and a wavelength of 360 nm as the ultraviolet light source (10).
When n+W/Cl11, the rate of formation of Si thin film is TO
~BOnm/min. Figure 3 shows that the (111') crystal of ζSi was improved using the apparatus of the present invention at a substrate temperature of 500.
℃, 100mW/ca! 75nm/ with ultraviolet irradiation
A backscattered electron diffraction image of a thin film grown with a growth rate of min, ie RHEI! D (Reflectio
n High Energy Electron Di
A photographic diagram of the ff-raction) pattern is shown. In addition, Figure 4 shows that the growth rate is 75 nm/min when the substrate temperature is 500°C and MBE is performed without UV irradiation.
A RIIEED'J4-1 diagram of a Si grown thin film obtained by a conventional apparatus is shown. As shown in Fig. 3, the Si grown thin film obtained using the apparatus of the present invention has a streak pattern compared to that obtained using the conventional apparatus shown in Fig. 4, indicating that the surface smoothness is extremely superior. .

For example, in the case of MBE of a Si film on a Si substrate in the above example, when growing this Si thin film, an impurity molecular beam source is provided close to the Si molecular beam source (not shown in the figure). It has been confirmed that thin films doped with impurities can be grown, and even when As or B is used as the impurity, the activation rate can be increased to 60-70% by UV irradiation. Ta.

In addition, in the above example, MBE of a Si thin film was performed on the St substrate (3), but by using a molecular beam source of another substance as a molecular beam source, it is possible to
It can also be applied to As, etc.

〔Effect of the invention〕

In conventional methods that do not irradiate ultraviolet rays, increasing the epitaxial growth rate requires adjusting the substrate temperature so that many dangling bonds occur, but with the device of the present invention, Since the growth rate can be increased without increasing the substrate temperature, even if the substrate (3) has a large area, MBE can be performed by low-temperature heating, thereby preventing the occurrence of "warpage" in the substrate (3). Inconveniences can be avoided, and inconveniences such as non-uniformity of characteristics in various parts and generation of defective products when various semiconductor devices are manufactured on a substrate can be avoided. therefore,
Combined with the fact that the thin film growth rate is increased, it is possible to perform MBE that can be fully put into practical use industrially.

Furthermore, when impurity doping is performed, the activation rate is greatly increased, and the degree of freedom in selecting the donor or acceptor concentration is increased without the need for special heat treatment for activation.

In addition, by utilizing the reflection of ultraviolet rays, in-situ observation of the ζ growth state becomes a FiJ function, so it is possible to control the manufacturing process.
The benefits of research and consideration are extremely large.

[Brief explanation of drawings]

Fig. 1 is a configuration diagram of an example of the present invention device, Fig. 2 is a model diagram of the bonded/unbonded state of valence electrons on the surface of 31 images, and Figs. It is a surface crystal structure photograph taken by RII EED of the grown MBE thin film. ill is an ultra-high vacuum chamber, (2) is a molecular beam source, (3) is a substrate, and (5) is an ultraviolet irradiation means.

Claims (1)

[Claims] 1. A molecular beam source for a thin film growth material and a substrate placement section are provided in an ultra-high vacuum chamber, and an ultraviolet irradiation means is provided for irradiating ultraviolet light toward the thin film growth surface of the substrate. . A thin film growth apparatus, wherein ultraviolet rays are irradiated onto the substrate, and in this state, molecular beam epitaxy is performed by molecular beam irradiation of the thin film growth material from the molecular beam source. 2. A molecular beam source for a thin film growth material and a substrate arrangement part are provided in an ultra-high vacuum chamber, and an ultraviolet irradiation means for irradiating ultraviolet light toward the thin film growth surface of the substrate is provided. irradiation, and in this state, molecular beam epitaxis is performed by molecular beam irradiation of the thin film growth material from the molecular beam source, and the reflected light of the ultraviolet rays from the substrate surface or the thin film growth surface is detected and A thin film growth apparatus equipped with ultraviolet detection means for determining or observing the surface condition of a surface.