JPS62167291A - Growing method for iii-v compound semiconductor thin film - Google Patents

Abstract

PURPOSE:To grow a semiconductor thin film consisting of an accurate single atomic layer by presetting both the temp. of the first region introducing organic compd. of group III elements and the temp. of the second region introducing group V elements separately and properly and transferring a base plate alternately to both regions. CONSTITUTION:The region I of the inside of a reaction vessel 1 is held at low temp. capable of adsorbing a molecule of organic compd. of group III elements and a region II is held at high temp. wherein reaction between the raw materials of group III and group V is advanced. A base plate 2 is set in the region I and organic compd. of group III element fed through a gas introduction port 5 is adsorbed on the surface of the base plate 2. The base plate 2 is transferred to the region II and a semiconductor thin film of the compds. is grown thereon by allowing V group elements (compds.) fed through a gas introduction port 6 to react with group III elements. Thereafter the base plate 2 is transferred to the region I. The thin film of GaAs of the like consisting of an accurate single atomic layer is grown in a required thickness in one reciprocation by repeating this motion. The control precision of the film thickness of a grown layer can be improved by this method.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for growing m-v group compound semiconductor thin films, and in particular to a method for precisely controlling film thickness at the atomic layer level and growing ultra-thin films.

[Conventional technology]

With the advancement of semiconductor devices, the demand for precise control over semiconductor crystal growth has become stronger, and film thickness control at the level of a single atomic layer has finally become necessary. Metal organic chemical vapor deposition method (MOCVD method), molecular beam epitaxial method (
Although the MBE method (MBE method) has been actively researched in recent years as an excellent method for controlling film thickness, its growth rate is basically determined by the rate at which raw materials are supplied to the substrate surface. Therefore, in order to control the film thickness extremely accurately, it is necessary to accurately control the amount of raw material supplied per unit time, but control at the level of a single atomic layer is difficult.

On the other hand, a method called an atomic layer epitaxial method or a molecular layer epitaxial method has been proposed as a method for accurately controlling the film thickness without depending on the amount of raw material supplied. This method is used for crystal growth using the normal MOCVD method, MBE
Instead of growing continuously as in the conventional method, growth proceeds by adsorbing the constituent elements of the crystal or their compounds one atomic layer at a time on the substrate surface and causing two reactions. Therefore, in theory, it is possible to grow the film while counting the film thickness in units of one atomic layer, eliminating the need for precise control of the raw material supply amount as in the usual MOCVD method and MBE method, and allowing it to withstand a wide range of changes in growth conditions. The film thickness is always determined only by the number of growths (the step of growing one atomic layer is counted as one).

The method will be explained below by taking as an example the atomic layer epitaxial method of gallium arsenide (GaAs), which is an m-v group compound semiconductor using an organic metal.

(i) First, trimethylgallium (Ga), which is an organometallic compound of gallium (Ga), is placed in a reaction vessel in which a substrate is installed.
TMGa) is introduced and adsorbed onto the substrate surface.

(ii) Discharge TMGa from the reaction vessel.

(iii) Arsine (As) as a raw material for arsenic (As)
H3) is introduced and reacts with the organic compound of Ga adsorbed on the substrate to further grow GaAs.

(iv) Discharge A s H3 and then repeat step (i
) to (iv) are repeated.

Throughout the above steps, the substrate temperature is always kept at a constant value.

[Problem that the invention seeks to solve]

In the conventional atomic layer epitaxial method using the above-mentioned organic metal, since the substrate temperature is always kept constant, it is difficult to accurately grow one atomic layer at a time. The above step (i
In ii), a high temperature above a certain level (500°C or higher in the case of GaAs growth using TMGa and AsH3) is required for the reaction to proceed sufficiently;
In i), it is not possible to accurately adsorb only one layer of Ga organic compound molecules. At high temperatures, thermal decomposition of TMGa occurs,
This is because once Ga is generated, the vapor pressure of Ga is extremely low, so that Ga is deposited.

After all, if the substrate temperature is low, the growth reaction will not proceed and the growth rate will be extremely low, while if it is high, the growth rate will increase and the quality of the crystal will deteriorate due to excess Ga. , there is no temperature at which ideal single atomic layer growth is possible. This is a common problem when using organic compounds of group (I) elements.

In addition, when growth is performed in a single reaction vessel, after the group ■ element material introduced - times is completely discharged from the reaction vessel,
It is necessary to introduce group element raw materials.

The same is true when switching the group III element raw material to the group III element raw material, and it takes a relatively long time to completely switch these elements, and when many switches are required, such as in atomic layer epitaxial growth, The growth time becomes long and the valve operation for switching becomes complicated.

An object of the present invention is to provide a method for growing an m-v group compound thin film that solves this problem.

[Means for solving problems]

In the method for growing an m-v group compound semiconductor thin film of the present invention, a first region of a reaction vessel having a first region and a second region is
An organic compound of a group element is introduced, a group V element or its compound is supplied to a second region, the first region is maintained at a low temperature that allows the adsorption of the group II organic compound molecules, and the second region is Maintain the temperature at a high temperature where the reaction between group ■ and group ■ element raw materials progresses,
The method is characterized in that the substrate is alternately moved between a first region and a second region to grow an m-v group compound semiconductor thin film on the substrate.

[Effect]

According to the present invention, since the raw material for the organic compound of the group (III) element and the raw material for the group (III) element are supplied to separate first and second regions of the reaction vessel, these raw materials may be continuously supplied;
There is no need for any troublesome switching work. Moreover, there is no longer a time to wait for gas switching in the reaction vessel. Furthermore, if the substrate temperature in the first region is set to be lower than the temperature at which a single group element is decomposed from an organic compound of a group II element, complete adsorption of a single atomic layer of an organic compound of a Group III element can be realized. Note that if the temperature is too low, there is a possibility that two or more layers will be adsorbed instead of just one layer, and in actual growth, the time required for temperature change when moving between two regions will be longer. Better to heat. In addition, the temperature of the second region can be set to a high temperature separately from the temperature of the first region, making it possible to sufficiently advance the reaction between the adsorbed group III element organic compound molecules and the group III element raw material. Accurate single atomic layer-by-layer growth is achieved.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a schematic cross-sectional view of an apparatus used in one embodiment of the present invention. The reaction vessel 1 is made of quartz and is separated into two regions. A gas inlet 5 is provided on the area (2) side, a gas inlet 6 is provided on the area (2), and a gas discharge lower is provided between the areas (2) and (2). Area 1. II
Windows 41 and 4 for irradiating heating light are provided respectively, and substrate heating lamps 31 and 3I are arranged outside facing these windows. The rod 1 is inserted through a seal 8 provided on the wall of the reaction vessel 1.
0 is supported to move back and forth between the two regions I and II. This rod is reciprocated by a substrate moving mechanism 9 placed outside the reaction vessel l. A substrate 2 is held at the tip of the rod.

A case will be described in which GaAs is grown using TMGa and AsH3 as raw materials in the above apparatus. During growth, the partial pressure of TMGa is 1.8 from the gas inlet 5.
X 10-4 atm, total pressure 1 atm, hydrogen flow rate 2j2/
A mixed gas of TMGa and H2 is always allowed to flow as a minimum. AsH3 is supplied from the gas inlet 6 with a partial pressure of AsH3 of 1 x 10-3 atm, a total pressure of 1 atm, and a hydrogen flow rate of 21/min.
A mixed gas of 3 and H2 is kept flowing. And area I
The substrate temperature in area 3 is 300℃, and the substrate temperature in area ■ is 520℃.
The output of each heating lamp 3I, 3I[ is controlled so that the temperature becomes ℃.

In the above state, the rod 10 is driven by the substrate moving mechanism 9, and the substrate 2 is first placed in the area I for 5 seconds, and then the gas inlet 5
The TMGa supplied from the substrate 2 was adsorbed onto the surface of the substrate 2, and then moved to the area (2). The travel time to area ■ is 1 second. The area (3) was left for 5 seconds to cause the AsH3 supplied from the gas inlet 6 to react with TMGa adsorbed on the substrate to grow GaAs. Thereafter, the substrate 2 was moved to area I again. When moving to region I, the substrate 2 was placed in a low temperature region at the intermediate point for 5 seconds to wait for the temperature of the substrate 2 to decrease. −
The total round trip time is 18 seconds.

When the above back-and-forth process was repeated 300 times, the thickness of the grown layer on the (100) plane of GaAs was 840 layers, which is almost the same as the value when one atomic layer, or 2.83 layers, was grown in a round trip. It was confirmed that the growth is accurate single atomic layer by layer.

In the embodiment shown here, a lamp heating method is used in order to change the substrate temperature in as short a time as possible, but other resistance heating methods or high frequency induction heating methods may be used as the heating method. Furthermore, since hydrogen as a carrier gas is not directly involved in the reaction, it is possible to lower the pressure inside the reaction vessel and ultimately achieve total growth (similar growth) using only TMGa and As H3 in a vacuum. It is.

〔Effect of the invention〕

As described above, according to the method of the present invention, in the atomic layer epitaxial method using an organometallic compound, there is no need for complicated interruption or switching of the supply of raw materials, and furthermore, the method of the present invention can be applied to the substrate surface of the group Accurate atomic layer growth is possible due to complete single atomic layer adsorption to and sufficient progress of reaction between Group I and Group II element raw materials, and the control accuracy of the thickness of the grown layer is dramatically improved.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view of an apparatus for explaining one embodiment of the present invention. 1...Reaction container 2...Substrate 3I, 3n...Heating lamp 41.41...Window 5.6...Gas inlet a...Gas exhaust Outlet 8...Seal 9...Substrate moving mechanism 10...Rod

Claims (1)

[Claims] (1) A group III element organic compound is introduced into the first region of a reaction vessel having a first region and a second region, a group V element or its compound is supplied to the second region, and a group V element or its compound is supplied to the second region. The area is
The substrate is held at a low temperature that allows the adsorption of group III element organic compound molecules, the second region is held at a high temperature where the reaction between the group III and group V element materials proceeds, and the substrate is placed between the first region and the second region. 1. A method for growing a III-V compound semiconductor thin film on a substrate, the method comprising growing a III-V compound semiconductor thin film on a substrate by moving the thin film alternately between substrates.