JPS59111322A - Manufacture of thin-film - Google Patents

Abstract

PURPOSE:To form a crystal obtained on a substrate in an excellent complete composition, and to grow the crystal of a necessary section without using a mask by irradiating laser beams of a wavelength corresponding to an absorption line of a raw material gas to the thin-film growth prearranged position of the substrate, on which the thin-film must be grown, as a heating source for decomposing the raw material gas used in the manufacture of the thin-film through a chemical vapor phase growth method. CONSTITUTION:Oscillating light-beams L1, L2 of each laser are diaphragmed up to necessary spot diameters by proper convergent optical systems 9a, 9b, and irradiated onto the substrate 1 through an optical window 10 set up to the wall of a device vessel 2. The lasers 8a, 8b are each used as several energy source for heating and decomposition exclusive for TMG and AsH3, and its each oscillating wavelength is selected according to light absorption spectra of several raw material gas. That is, when the laser 8a is used for TMG and the laser 8b for AsH3, the wavelength of the beams L1 of the laser 8a is selected in a wavelength, which is absorbed only to TMG with high efficiency and thermally converted, and that of the laser 8b in a wavelength, which is absorbed only to AsH3 with high efficiency and thermally converted, and are mutually different to each other.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in thin film manufacturing methods by chemical vapor deposition (CVD).

CVD is a thin film production method that is often employed during the manufacturing process of various semiconductor devices, but depending on the raw material gas and the type of thin film to be produced, satisfactory results may not be obtained in some cases. In order to clarify the cause, first of all, Fig. 1 shows an outline of the conventional equipment, and in particular, metal-organic substance-CVD (
As an example, a conventional example of growing and depositing a GaAs single crystal, which has been attracting attention recently, on a suitable substrate such as 1nP, Sj, GaAs, etc., will be explained.

A substrate 1 is placed in a suitable device container, and a suitable heater 3 is installed inside or outside the container (high frequency induction heating) so that the substrate can be heated to an arbitrary temperature. The container must have sufficient ventilation. Trimethylgallium Ga (CHs) 3, abbreviated as TMG, as raw material gas, arsine ASHa, and hydrogen H2 as carrier gas were injected, respectively. , B, Flow an appropriate amount from 7, and exhaust from the exhaust log on the opposite side. When the substrate is heated (700°C), TMG and AsHs that come into contact with it are thermally decomposed, generating Gα and As.
They immediately adhere and crystallize on the substrate.

These conventional methods have the following drawbacks. ■When growing GaAs on a substrate, the optimum growth temperature Tb for the substrate and the optimum decomposition temperature TTMG + for metal-organic substances.
Each of the three TAs is different. However, in the conventional method described above, the temperature of the metal-organic gas is fixed at approximately the same temperature as the substrate being heated. Therefore, if the substrate temperature is selected to be the optimum temperature Tb for crystal growth, the gas temperature will naturally deviate from the optimum temperature for thermal decomposition. Therefore, growth occurred with incomplete decomposition or, conversely, at a rate of decomposition that was too fast, and as a result, the GcLAs obtained on the substrate could not be of good quality. In particular, if the decomposition is incomplete, hydrocarbons will be mixed into the crystals, significantly impeding the integrity of the crystals. (2) Although the metal-organic gas is continuously flowed, there is inevitably a deviation (generally about 5%) in each flow rate.

Therefore, a crystal with a perfect composition (Ga:88:1:1) cannot be obtained. ■ G to be generated (LAS does not use a mask and adheres to the entire surface of the substrate. This is generally wasteful. Also, when producing different semiconductors at different locations on the same substrate, According to the conventional example above, unnecessary parts are removed by etching after the thin film is completed (
GaA3 must be grown after applying a photoresist in advance and removing the resist in the necessary areas by etching. This method requires formation of a resist and removal of unnecessary parts by etching, which greatly increases brightness and increases costs, and etching damages the substrate or the grown G (LA8).

The present invention has been made primarily to eliminate the three major drawbacks of the prior art.

To summarize the present invention, a laser beam of an appropriate wavelength is used for at least one raw material gas, preferably for each of a plurality of types of raw material scraps, and each laser beam is used as a thermal decomposition source for each raw material gas. This is especially true of dogs.

Embodiments of the present invention will be described below with reference to FIG. 2 and subsequent figures.

FIG. 2 shows an example of an apparatus for carrying out the method of the present invention, and the same reference numerals are used for components that may be the same as or correspond to the conventional apparatus shown in FIG. In addition, in order to make the effect of the present invention more apparent, the thin film to be manufactured in this example is made of Gaps and T
MG and AsHs are selected as source gases.

The equipment features are an appropriate number of lasers arranged to focus on a predetermined location on the substrate, in this case two lasers rα and rb.
, the oscillation light beams Lt, Lt of each laser are:
After narrowing down to a required spot diameter using appropriate converging optical systems α and Rb, the light is irradiated onto the substrate through an optical window /θ provided on the wall of the apparatus container.

To state in advance, the lasers Ia and Ib are TM
It is used as an energy source for thermal decomposition dedicated to G, A, and 9L, and therefore, each oscillation wavelength is selected in consideration of the optical absorption spectrum of each source gas. That is,
If the laser rα is used for TMG and the laser rb is used for A3H8, the wavelength of the laser and the beam L of α is the same as that of the TMG.
The wavelength of laser rb is selected to be absorbed with high efficiency and converted into heat only by AsHa, and the wavelength of laser rb is selected to be absorbed with high efficiency and converted into heat only by AsHa, and the wavelengths are different from each other. A specific example is as follows.

Figure 5(a) shows the infrared absorption spectrum of TMG, and Figure 3(b) shows that of AsHs.
From figure (a), TMG is 5,000c+++-', 1,
200m-”, 770cm-”.

It can be seen that absorption occurs at oscillation wave numbers such as 580 crn-'. Among these, focusing on the absorption line at 1,20[1cPn-'', the oscillation wave number of the OCS laser among existing lasers can match the absorption line at 1,200crn' of this TMG.In other words, the OCS laser , wave number 1.21
+, 8cnr" to 1,187.0crn-" approximately 3
Since there are 0 oscillation lines, it is easy to select the 1.200cn1-' oscillation line to match the absorption line of TMG.

Assume that this OCS laser Ia is used and focused on the substrate or very close to it, as shown in the second diagram.

Then, since the laser electric field is concentrated in the vicinity of this focal point, the TMG is strongly heated only in that part, the TMG existing only in this part is decomposed, and the head is released.

In exactly the same way, AsH3 has a wave number of 2,000.1. ooo, 960.900cIn-'
shows absorption.

Therefore, if we choose a carbon dioxide laser as the laser rb and match it to a wave number of 960 crn-'' (a carbon dioxide laser has an oscillation line of several tens of water at 940 to 1,040 crn), the laser light will focus on AsH. It is possible to disassemble only the parts that connect them. TMG and AsHa
The absorption lines of LLL do not overlap with each other, and the wavelengths of the laser beams LLL and LLL are different from each other. Therefore, two Luisa tra,
It is possible to independently set the temperature of each beam, TMG and AsHs of the trly, and it is possible to provide the optimum temperature for each decomposition. Furthermore, as a substrate/
I? If IP, Si, Gg or GIZAS are used, these will be the laser beam L selected in this example.
, , L, so the laser beam L
j, L! does not heat this board. Of course, if the heater 3 is installed as before, the substrate temperature can be set independently, so the temperature at which Gaps crystals are grown on the substrate can be set independently of the optimal decomposition temperature of TMG and AsHs (generally desired low temperature). ) can be selected.

Judging from the above examples, roughly speaking, if it is CvD,
It is obvious that the present invention can be widely applied regardless of the raw material gas or the substrate material, and the laser can be arbitrarily selected from various types according to each raw material gas. MO-C
As an example of raw material gas for VD, TM as a group metal
Gα, TMAl.

TEGα, TEAt, etc., AsHs, D as group ■
Ha, 5bHs.

As a dopant, DEZnp H2Ssr, etc. are used, and as an infrared laser, carbon dioxide gas (CO2),
CO, OC8゜HF,)r, N2, HCl,
DF, HBr, DCl, DBτ, No, N
tO.

Examples include H2S visible dye laser and excimer laser.

In addition, the source gas is decomposed only in a very small range near the focal point of each laser, and the laser beam can be narrowed down to the wavelength of the laser beam, so it is possible to inject only a portion of the substrate. A desired thin film can be selectively grown using a resistless process without going through a photophosphorographic process such as .

On the other hand, in order to grow a thin film on a substrate over a range of areas, the laser beam can be deflected and scanned using a normal deflector, or a known X-Y direction movable sample supporting the substrate can be used. All you have to do is scan and control the table.

Furthermore, as shown in FIG. 4, which shows one beam L+ or L2 and its essential parts, each beam is loaded with turn information corresponding to the same desired pattern /3 drawn on mask /2. By narrowing down the size to the required size and projecting it onto the substrate l, a thin film with the desired pattern can be created on the substrate using a resistless process. In this case, the mask/J may be dedicated to each beam, pattern information may be placed on each beam, and both beams may be mixed and projected onto the substrate as shown in the second figure, or both beams may be After mixing using a suitable optical system, pattern information may be placed on both beams at once through a common mask.

Through the above examples, the effects of the present invention can be summarized as follows.

1) Optimal thermal decomposition temperature and substrate temperature (
(optimum growth temperature) can be controlled and set independently.

Therefore, it is possible to eliminate the possibility that the decomposition temperature is restricted by the substrate temperature and inhibit the growth of the crystal as in the conventional example, and a high-quality crystal can be obtained.

11) It is possible to grow a thin film only on a selected part of the substrate without resisting, reducing the number of steps and avoiding the inconveniences associated with the conventional A2DGE 1. Furthermore, if crystals with different compositions or components are required on the same substrate, a large number of crystals can be grown without taking them out from the container.

111) The raw material gas is constantly flowing, and fluctuations in pressure and flow rate are unavoidable, and in conventional methods, this directly has a strong influence on the composition of the grown crystal. That is, due to variations in the flow rate, the ratio of Ga to As in the grown thin film, for example, varied in the previous example, and in this sense as well, a perfect GaAg single crystal could not be obtained. On the other hand, in the present invention, the laser output intensity can be controlled freely and quickly using existing technology, so TMG can be controlled from time to time.

It is also possible to make the generation rate of Gα and As completely constant by adjusting the laser intensity to follow the flow rate of AsHs. Of course, if necessary, it is also easy to arbitrarily change the ratio of Gα and As.

1) If necessary, a thin film with a desired pattern can be easily grown on the substrate using the same process.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a conventional MO-CVD device;
FIG. 2 is a schematic configuration diagram of an example of a device for carrying out the method of the present invention, and FIG. 5 is a diagram showing TMG and A as an example of raw material gas.
A characteristic diagram of the infrared absorption spectrum of sH3, and FIG. 4 is an explanatory diagram of the main parts of another apparatus used in the method of the present invention. In the figure, l is a substrate, c is a container, raJb is a laser, and IO is a window.

Claims (1)

[Claims] A method for producing a thin film by chemical vapor deposition, wherein the thin film is grown using a laser beam having a wavelength corresponding to the absorption line of the raw material gas as a heating source for decomposing the raw material gas used. A method for producing a thin film, which comprises irradiating a target position on a substrate where the thin film is to be grown.