JPH068240B2 - Thin film manufacturing method - Google Patents

Description

The present invention relates to a method for forming a thin film of GaAs or the like on a substrate.

<Prior Art> A manufacturing procedure for forming a GaAs thin film on a GaAs substrate by an ion beam evaporation method will be described below.

Place the GaAs substrate in the vacuum chamber and first place the GaAs substrate at 80
Thermally clean the substrate surface by heating at 0-900 ° C for 10 hours. This is performed to remove the oxide film formed on the substrate surface or the adsorbed contaminants in the pretreatment step, and after the cleaning is completed, the Ga and As ions are accelerated to a predetermined energy on the substrate surface. Then, irradiation is performed to grow a GaAs thin film on the surface of the substrate.

Further, in the case of epitaxially growing a GaAs thin film on a Si substrate, a two-step growth method based on the MBE method has been conventionally used. The manufacturing procedure will be described below.

First, similar to the above procedure, the Si substrate is heated at 800 to 900 ° C. for about 1 hour to perform thermal cleaning, and then,
The temperature of the substrate is set to about 400 ° C, and the surface of the substrate is irradiated with molecular beams of Ga and As in this state to deposit an amorphous or crystallized buffer layer to some extent, and then the substrate temperature is set to 500 to 700 ° C. , And in this state, the surface of the substrate is irradiated with molecular beams of Ga and As respectively,
A GaAs thin film is epitaxially grown on the buffer layer.

<Problems to be Solved by the Invention> By the way, according to the above-mentioned conventional procedure, since the temperature of the substrate is changed in the thin film manufacturing process, there is a possibility that the substrate is warped and deterioration such as dislocation growth occurs. there were.

An object of the present invention is to provide a method capable of producing a desired thin film without causing deterioration of a substrate.

<Means for Solving the Problems> In the thin film manufacturing method of the present invention, one or more kinds of vapor deposition materials are heated to evaporate in a vacuum atmosphere, and each of the vaporized particles is ionized to have a predetermined strength. In a method of forming a thin film on a substrate surface by irradiating the substrate surface by accelerating with an electric field, at least one of vapor deposition materials for forming a thin film on a substrate surface on which a thin film is to be formed in a vacuum atmosphere. The feature of the present invention is that the film formation is performed after the ions of evaporated particles of the material are accelerated and irradiated with an electric field having a strength different from that during film formation.

<Operation> It is generally known that when a substrate surface is irradiated with ions accelerated by an acceleration voltage of about several kV, the surface layer of the substrate is sputtered by the ions. Therefore, the strength of the accelerating electric field of evaporated particle ions, that is, the accelerating voltage is several k
When set to about V, the oxide film and the like on the surface of the substrate can be removed by sputter cleaning with evaporated particle ions regardless of the temperature of the substrate.

Further, it is known that, on a substrate at a certain temperature, whether or not a thin film is epitaxially grown depends on the amount of energy when vaporized particles collide with the substrate. That is, when the energy at the time of collision is small, the obtained film becomes amorphous. Therefore, if the accelerating voltage is set to a value lower than a value suitable for growing an epitaxial thin film, an amorphous or partially crystallized layer can be stacked on the substrate surface without changing the temperature of the substrate. It will be possible.

<Examples> Examples of the present invention will be described below with reference to the drawings.

The drawing is a schematic diagram of a thin film manufacturing apparatus used for carrying out the method of the present invention.

Two ion sources Ga ion source 1 and As ion source 2 are arranged in a vacuum chamber (not shown).

The ion sources 1 and 2 are steam generators 11 and 21, respectively.
And the ionization units 12 and 22,
Each of the output ions is configured to reach the same substrate S.

Above each of the ion sources 1 and 2 is an accelerating electrode 1 respectively.
3 and 23 are provided. Each acceleration electrode 13, 23
And the substrate S between the shutters 14 and 24, respectively.
Is provided, and the operation of the shutters 14 and 24 can selectively block the progress of ions from the ion sources 1 and 2 to the substrate S.

The vapor generating units 11 and 21 are provided with a crucible containing the vapor deposition material Ga or As and a heating filament surrounding the lateral periphery thereof, and vaporize the vapor deposition material inside by heating the crucible with the heating filament. It is configured to change.

The ionization units 12 and 22 include an ionization filament and a grid, and are configured to positively ionize the vapor by causing the thermoelectrons generated by the ionization filament to stop and collide with the vapor from the vapor generation units 11 and 21 by the grid. Has been done.

The substrate S and the acceleration electrodes 13 and 23 are placed at the ground potential. In addition, each acceleration electrode 13, 23 and each ion source 1, 2
Variable DC power supplies 15 and 25 are provided between the two, respectively, and an arbitrary potential difference can be applied between the ion sources 1 and 2 so that they have a positive potential. Then, by the electric field formed by this potential difference, the vapors that have been positively ionized in the ionization units 12 and 22 are accelerated and collide with the surface of the substrate S.

The substrate S is held at a predetermined position in the vacuum chamber by a holder (not shown) equipped with, for example, a heater and a thermocouple, and is maintained at a predetermined temperature, for example, about 500 to 700 ° C. .

Using the device described above, GaA is formed on a GaAs substrate.
The procedure for forming a thin film will be described.

First, the temperature of the substrate S is kept at a temperature suitable for film formation at about 500 to 700 ° C., and the Ga ion source 1 and the As ion source 2 are used.
In the state where both are driven, only the shutter 24 on the As ion source 2 side is opened, and the surface of the substrate S is irradiated with accelerated As ions. The acceleration voltage of As ions at this time is about several kV. As a result, the surface of the substrate S is sputtered with As ions, and the surface layer of the substrate S is etched by about 100Å by irradiation with As ions for several minutes. By this etching, a smooth surface at the atomic layer level appears on the surface of the substrate S, and the oxide film and the like attached to the surface of the substrate S in the previous step are sufficiently cleaned.

After the above cleaning process is completed, the acceleration voltage of each of the ion sources 1 and 2 is set to a predetermined value during normal film formation, and the shutter 14 on the Ga ion source 1 side is opened to expose the surface of the substrate S. Ga and As ions are accelerated and irradiated to form a GaAs thin film on the surface of the substrate S.

Here, the acceleration voltage of Ga and As ions during film formation is
The energy is set appropriately so that each ion migrates to the surface of the substrate or has such energy that it can sputter a part of the surface of the substrate. The energy of collision of As ions with the substrate during film formation is naturally smaller than the energy during substrate etching.
The acceleration voltage of s ions has a value lower than the acceleration voltage at the time of cleaning the substrate.

Next, a procedure for epitaxially growing a GaAs thin film on a Si substrate using the same apparatus as that of the previous embodiment will be described.

First, while keeping the substrate S at a temperature suitable for film formation at about 500 to 700 ° C. and driving both the Ga ion source 1 and the As ion source 2, the As ion source 2 is subjected to the same procedure as described above.
Only the side shutter 24 is opened, the surface of the substrate S is irradiated with As ions accelerated by an acceleration voltage of several kV, and the surface of the substrate S is cleaned.

Next, the acceleration voltages of the Ga ion source 1 and the As ion source 2 are set to 1 kV or less, respectively, and the shutter 14 on the Ga ion source 1 side is opened to irradiate the surface of the substrate S with Ga and As ions. Substrate S of each ion at this time
The collision energy is small, and the surface of the substrate S is amorphous or crystallized to some extent, that is, GaAs.
A buffer layer will be laminated.

Then, the acceleration voltage of the Ga ion source 1 and the As ion source 2 is set to a value higher than the acceleration voltage at the time of stacking the buffer layer, that is, a value suitable for epitaxially growing a GaAs thin film, In this state, the surface of the substrate S is irradiated with Ga and As ions to epitaxially grow a GaAs thin film on the buffer layer on the surface of the substrate S.

In this procedure as well, it goes without saying that the accelerating voltage of As ions when epitaxially growing the GaAs thin film is lower than the accelerating voltage at the time of cleaning the substrate.

An example in which the present invention is applied to the formation of a GaAs thin film has been described above, but the present invention can also be applied to the formation of a thin film of another material such as a Si thin film.

<Effects of the Invention> As described above, according to the present invention, evaporated particle ions of a material forming a thin film on a substrate surface in a vacuum atmosphere are accelerated by a stronger electric field or a weaker electric field than during film formation. After the irradiation, the film is formed, so that the oxide etc. adhering to the substrate surface can be removed and the buffer layer can be laminated without changing the substrate temperature, which deteriorates the quality of the substrate. It is possible to form a desired thin film without performing the above.

Further, it is not necessary to keep the substrate temperature at a high temperature, for example, 700 ° C. or higher, and the heating capacity of the substrate in the substrate holder or the like can be reduced as compared with the conventional case.

[Brief description of drawings]

The drawing is a schematic configuration diagram of an apparatus used for carrying out the method of the present invention. 1 ... Ga ion source 2 ... As ion source 11,21 ... Steam generation part 12,22 ... Ionization part 13,23 ... Accelerating electrode S ... Substrate.

Claims (1)

[Claims] 1. A method of evaporating one or a plurality of kinds of vapor deposition materials by heating in a vacuum atmosphere, ionizing each of the vaporized particles, accelerating the vaporized particles with an electric field of a predetermined strength, and irradiating the substrate surface. According to the method for forming a thin film on the surface of a substrate, ions of evaporated particles of at least one of the above vapor deposition materials are different from those at the time of film formation on the surface of the substrate on which the thin film is to be formed. A method for producing a thin film, which comprises accelerating and irradiating with a strong electric field and then performing film formation.