JPS6284523A - Vapor growth device - Google Patents

Abstract

PURPOSE:To manufacture a multilayer epitaxial layer having high film-thickness precision and a uniform crystalline composition with high yield by forming a device by a region, in which a gaseous element having a large diffusion coefficient is diffused, and a region, in which elements except the gaseous element where grown in an epitaxial manner, and moving a substrate into both regions by turning a control rod. CONSTITUTION:In a vapor growth device, a region in which there is a reaction gas is divided into two by a partition wall 14, and a crystal substrage 1 to which epitaxial growth is conducted can be shifted in the two regions by rotating a control rod 10. The crystal substrate 1 is held and CdTe epitaxial growth is performed. When a CdTe layer 2 in approximately 0.05mum is grown, the control rod 10 is half-turned, and the crystal substrate 1 is transferred into Hg vapor. Consequently, Hg atoms precipitate on the CdTe layer 2, and a solid-phase diffusion instantaneously progresses at the temperature of precipitation and Hg atoms change into a HgCdTe layer 3 with time. As a result, the control rod 10 is half-turned further at a step when the solid-phase diffusion progress up to half the epitaxial-grown CdTe layer 2, and said operation is repeated. Accordingly, the accuracy of film thickness is improved, and a homogeneous composition is acquired continuously.

Description

[Detailed Description of the Invention] [Summary] As a method for repeatedly growing epitaxial growth layers with different compositions on a semiconductor substrate, a region for epitaxial growth and a region for diffusing an element with a large diffusion coefficient are provided in an apparatus, and epitaxial growth is performed. A device that moves the substrate into both areas.

[Industrial application field]

The present invention relates to a vapor phase growth apparatus capable of repeatedly growing epitaxial layers having different compositions.

Epitaxial growth technology is widely used in the formation of semiconductor devices, and was initially used in the field of bipolar transistors and bipolar ICs, but is now used in the field of MOS.
It has even spread to the LSI field.

Here, the epitaxial growth method includes a vapor phase growth method and a liquid phase growth method, and each is used depending on the composition and properties of the semiconductor material to be grown.

For example, it is advantageous to use a liquid phase growth method for growing a compound semiconductor containing an element with a high vapor pressure such as indium fi (InP).

However, the vapor phase growth method is used in most applications because it is easy to operate and the thickness of the grown layer can be easily adjusted.

Here, the vapor phase growth method includes the chemical vapor deposition method (abbreviated as CVD method) in which growth is achieved by thermally decomposing a reactive gas containing the constituent elements of the semiconductor to be epitaxially grown, and the chemical vapor deposition method (abbreviated as CVD method) in which the constituent elements are evaporated in molecular form to form a certain amount on the substrate. There are two methods: molecular beam epitaxy (abbreviated as MBE), which grows a semiconductor layer having a certain composition ratio, and the present invention relates to a growth apparatus that uses the former method.

[Conventional technology]

Some semiconductor devices are made by epitaxially growing a number of semiconductor layers with different compositions, and patterning electrodes thereon.

For example, an infrared detector is this type, and as shown in FIG.
The semiconductor layer of the detection section is made by repeatedly epitaxially growing a mercury-cadmium-tellurium (IgCdTe) layer 3.

In order to make the detected infrared wavelength match the set value, the film thicknesses of the CdTe layer 2 and IgCdTe layer 3 must be controlled accurately, and the CdTe layer 2 and IgCdTe layer 3 must be
It is necessary that the two compound semiconductor layers are formed with correct component ratios.

FIG. 2 shows a conventional formation method. A reaction tube 4 made of quartz that constitutes a growth apparatus has a plurality of gas supply ports 5.6 for introducing reaction gases and an exhaust lower. There is a susceptor 8 on which a crystal substrate 1 is placed, and a heater 9 for heating the substrate (in this example, a high frequency coil) is installed around the reaction tube 4.

As shown in FIG. 3, a crystal substrate 1 made of CdTe is
When repeating crystal growth of CdTe layer 2 and IgCdTe layer 3 on top of the CdTe layer 2 and IgCdTe layer 3, after removing the air from the reaction tube 4 by exhausting from the exhaust lower, dimethyl cadmium ((CH3) saturated with hydrogen (H2) using a bubbler is used. ) 2Cd) and diethyl tellurium ((C2Hs) 2Te) are mixed in the respective composition ratios and supplied to the reaction tube 4 through the gas supply port 5.

The reaction gas supplied in this manner using H2 gas as a carrier is thermally decomposed on the crystal substrate 1 heated by the heater 9, and epitaxial growth of CdTe progresses.

Then, by adjusting the thermal decomposition time, the CdTe was heated to a predetermined thickness.
When the layer 2 is grown, the cock of the gas supply port 5 is closed, and the gas supply port 6 is opened instead to supply Hg vapor saturated with H2 gas.

Such Hg vapor is produced by heating the og to 250-300°C and then passing H2 gas through it.

In this way, Hg atoms uniformly precipitate on the CdTe layer 2 on the substrate, and since Hg atoms are a metal that easily diffuses heat, they uniformly diffuse in solid phase to form an IgCdTe layer 3 on the surface. The CdTe layer 2 becomes IgCdTe in proportion to the processing time.
It will change to layer 3.

After a certain period of time has elapsed, the cock is switched again and a mixed gas of (C2H!')2Te and (CH3)2Cd is supplied using H2 gas as a carrier and thermally decomposed to epitaxially grow the CdTe layer 2. By repeating the above steps in this way, a semiconductor layer having a multilayer structure as shown in FIG. 3 was formed.

However, in such conventional methods, gas exchange cannot be carried out rapidly, so each layer is formed thickly, and a heteroepitaxial layer with clear boundaries cannot be formed.

[Problem that the invention seeks to solve]

As mentioned above, conventional vapor phase growth equipment grows heteroepitaxial layers by exchanging reactant gases, so each layer tends to become thicker, and it is difficult to form an epitaxial layer with a uniform composition. There is.

[Means for solving problems]

The above problem arises because the equipment that epitaxially grows compound semiconductors with a uniform composition by solid-phase diffusion consists of a region in which gaseous elements with large diffusion coefficients are diffused and a region in which semiconductors excluding the elements are epitaxially grown. This problem can be solved by using a vapor phase growth apparatus that moves the substrate into both regions by rotating an operating rod on which the substrate is attached, and repeatedly grows epitaxial layers with different compositions on the substrate.

[Effect]

The vapor phase growth apparatus according to the present invention does not change the type of reaction gas supplied onto the crystal substrate by switching the cock as in the past, but instead supplies two types of reaction gas in parallel and can be operated from the outside. By changing the position of the crystal substrate, the type of reactive gas that decomposes upon contact with the crystal substrate can be changed.

In this way, the above-mentioned problem is solved because the reaction gas is rapidly exchanged.

〔Example〕

FIG. 1 is a sectional view of a vapor phase growth apparatus according to the present invention,
The region where the reaction gas exists is divided into two by the partition wall 14, and the crystal substrate 1 on which epitaxial growth is to be performed can be moved to the two regions by rotation of the operating rod 10.

A case will be described in which a CdTe layer 2 and a HgCdTe layer 3 are epitaxially grown repeatedly on a crystal substrate 1 made of CdTe, similar to the case of FIG. 3 explained above.

In this embodiment, a ttg reservoir 11 made of quartz is provided in the device.
II g 12 is put therein, heated by a heater 13 to vaporize it, and is supplied from a gas supply port 6 toward the crystal substrate using H2 as a carrier.

However, this may be done by generating Hg gas outside the reaction tube 15 and supplying it through the gas supply port 6 as in the conventional case.

On the other hand, the reaction gas for epitaxial growth of CdTe uses H2 as a carrier and passes through a bubbler (CH
3) 2Cd and (C2H5)2Te are supplied through the gas supply port 5.

In this embodiment, the heater 13 controls Hg12 from 250 to
heated to 280°C to a vapor pressure of about 76 Torr, while (C2H5) 2 Te and (C)+3 ) z Cd
A mixed gas of 10-odd Torr is passed through a bubbler at 5
A flow rate of °β/min was supplied.

Meanwhile, the crystal substrate 1 was heated to 380 to 450° C. by the heater 9.

Initially, CdTe is epitaxially grown while holding the crystal substrate in the position shown in FIG. 1, and the growth rate in this case is 2 to 4 μffl/hour.

When the CdTe layer 2 of about 0.05 μm has grown, the operating rod 10 is turned half a turn to move the crystal substrate 1 into Hg vapor.

As a result, Hg atoms precipitate on the CdTe layer 2, solid phase diffusion immediately proceeds at this temperature, and over time HgCdT
It changes to e-layer 3.

Therefore, when the solid phase diffusion has progressed to half of the epitaxially grown CdTe layer 2, the operating rod 10 is further rotated half a turn to grow the CdTe layer again. Proceed with solid-phase diffusion.

By employing such a method, it is possible to continuously grow an epitaxial layer with good film thickness accuracy and a homogeneous composition.

〔Effect of the invention〕

As described above, by carrying out the present invention, the conventional problem that a uniform growth layer cannot be formed by solid-phase diffusion has been solved, and multilayer epitaxial layers with good film thickness accuracy and uniform crystal composition can be manufactured with high yield. can do.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a vapor phase growth apparatus according to the present invention, FIG. 2 is a sectional view of a conventional vapor phase growth apparatus, and FIG. 3 is a sectional view of an epitaxial layer to which the present invention is applied. In the figure, 1 is a crystal substrate, 2 is a CdTe layer, and 3 is a Hg
CdTe layer, 4.15 is reaction tube, 9.13
is the heater, 10 is the operating rod, 11 is the h reservoir,
12 is ug, and 14 is a partition wall.

Claims (1)

[Claims] An apparatus for epitaxially growing a compound semiconductor with a uniform composition by solid-phase diffusion comprises a region for diffusing a gaseous element with a large diffusion coefficient and a region for epitaxially growing a semiconductor compound excluding the element, and a substrate on which epitaxial growth is to be performed. A vapor phase growth apparatus characterized in that the epitaxial layers are moved into both regions and epitaxial layers having different compositions are repeatedly grown on the substrate.