JPH01301585A - Apparatus for growing semiconductor crystal - Google Patents

Abstract

PURPOSE:To constantly uniformize the film thickness or impurity concentration of a crystal grown by an organic metal vapor growth process, by using an apparatus for monitoring the concentration and composition of raw material gas. CONSTITUTION:A by-pass line 7 is attached near the growth gas inlet port of a reaction tube 4 and the concentration and composition of the branched raw material gas are monitored with a quantitative analyzer 8 by infrared spectrometry or Raman spectrometry. For example, a GaAs substrate crystal 5 is placed in the reaction tube 4 and heated by passing electric current through an RF coil 6 while passing H2 gas through the tube. H2 gas is introduced via a flow-controller 3 into a bubbler 1 containing an organic metal compound to effect the bubbling of the compound. Separately, AsH3 gas is introduced from a bomb 2 in the same manner as above. These gases are introduced into the line 7, the concentration and composition of the gases are determined by the apparatus 8 and the flow rate of each gas is adjusted in such a manner as to form an epitaxial layer having prescribed film thickness and impurity concentration. The raw material gas is introduced into the reaction tube 4 to effect the growth of the crystal.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a semiconductor crystal growth apparatus used for manufacturing compound semiconductor devices, and in particular to a semiconductor crystal growth apparatus that can obtain a uniform epitaxial layer with good controllability by MOCVD method. It is related to the device.

[Conventional technology]

Conventionally, MO is used as a crystal growth method for m-v group compound semiconductors, etc.
There is a CVD method. Figure 2 is a schematic diagram of a conventional MOCVD apparatus, in which 1 is an organometallic bubbler, 2 is a source gas cylinder, 3 is a mass flow controller, 4 is a reaction tube, 5 is a substrate crystal, and 6 is an RF coil. .

Next, the operation of the conventional MOCVD apparatus will be explained using an example in which GaAs epitaxial growth is performed.

First, after setting the substrate crystal 5 in the reaction tube 4, H! While the gas is flowing, a current is passed through the RF coil 6 to heat the substrate. and organometallic (here (CHa) s G
a: Pass H! through the mass flow controller 3 through the bubbler 1 containing TM C). The gas is introduced into the reaction tube 4 through bubbling. On the other hand, AS diluted with Ht
Open the original pulp of raw material gas cylinder 2 filled with H3,
The mass flow controller 3 adjusts the flow rate, and the gas is introduced into the reaction tube as a raw material gas. These gases are
It thermally decomposes near the surface of the GaAs crystal, which is deposited on the substrate.

The thickness of the epitaxial layer is approximately proportional to the flow rate of TMG, and the impurity concentration in the crystal is proportional to the flow rate of TMG and ASH.
It is well known that the ratio of flow 1 to 1 changes depending on the ratio of flow 1:1.

[Problem to be solved by the invention]

Since the conventional semiconductor crystal growth apparatus is configured as described above, the film thickness and impurity concentration of the epitaxial layer are likely to fluctuate due to variations in vapor pressure due to temperature fluctuations of the organometallic bubbler, variations in the concentration of cylinder gas, etc. There is a problem in that even if growth is performed at a constant gas flow rate using a mass flow controller, controllability may deteriorate due to changes in gas concentration.

The present invention was made in order to eliminate the above-mentioned drawbacks, and an object of the present invention is to obtain a semiconductor crystal growth apparatus that can always grow an epitaxial layer with a constant film thickness or impurity concentration.

[Means for Solving the Problems] A semiconductor crystal growth apparatus according to the present invention includes a bypass line provided near a growth gas inlet of a reaction tube, and a raw material branched to the bypass line by infrared spectroscopy or Raman spectroscopy. It is equipped with a quantitative analysis device that monitors the concentration and composition of gas.

[Effect]

In this invention, since the structure is equipped with a quantitative analyzer for monitoring the concentration and composition of the source gas branched into a bypass line provided near the growth gas inlet of the reaction tube, the gas is Concentration etc. can be monitored,
Since the optimum flow rate can be set based on this value, it is possible to always grow an epitaxial layer with a constant film thickness and impurity concentration.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a configuration diagram showing a semiconductor crystal growth apparatus according to an embodiment of the present invention, in which 1 is an organometallic bubbler, 2 is a source gas cylinder, 3 is a mass flow controller,
4 is a reaction tube, 5 is a substrate crystal, 6 is an RF coil, 7 is a bypass line, and 8 is a quantitative analysis device.

As with conventional semiconductor crystal growth equipment, the organometallic bubbler is kept at a constant temperature by placing it in a constant temperature bath, and the raw material gas cylinder is diluted with H2 gas to a constant concentration.

Next, the operation of this embodiment will be explained using an example in which GaAs epitaxial growth is performed in the same manner as in the conventional example.

First, after setting the GaAs substrate crystal 5 in the reaction tube 4, a current is applied to the RF coil 6 without flowing H2 gas to heat the substrate. Then, Hz gas is passed through a mass flow controller 3 to a bubbler 1 containing an organic metal (TMG) to cause bubbling.

On the other hand, open the main valve of the A s Hs gas cylinder 2 and adjust the flow rate with a mass flow controller.In the conventional example, these gases are immediately flowed into the reaction tube to start growth, but in the present invention, these gases are first Once flowed into the bypass line, the concentration and composition of the raw material gas are examined using a quantitative analyzer using infrared spectroscopy (or Raman spectroscopy), and the flow rate of each gas is set to obtain an epitaxial layer with the desired film thickness and impurity concentration. After that, a raw material gas is introduced into the reaction tube to perform epitaxial growth.

Furthermore, in this example, after the start of growth, a portion of the exhaust gas is subjected to the above-mentioned analyzer to examine the relationship between the growth temperature and the thermal decomposition rate of the raw material gas, and based on this result, the optimum growth temperature can be determined. I can do it.

Note that although the above embodiments have been explained using GaAs epitaxial growth as an example, the present invention is not limited to this, and it is believed that similar effects can be obtained in crystal growth of other compound semiconductors such as AlGaAs and InGaAsP. Needless to say.

(Effects of the Invention) As described above, according to the present invention, the concentration and composition of the source gas can be monitored in the MOCVD semiconductor crystal growth apparatus, and the flow rate of the gas can be controlled based on the monitoring results. This has the effect that crystal growth can always be performed under constant conditions.

Furthermore, by examining the relationship between the growth temperature and the thermal decomposition rate of the raw material gas, it is possible to determine the optimum growth temperature.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a semiconductor crystal growth apparatus according to an embodiment of the present invention, and FIG. 2 is a schematic diagram of a conventional semiconductor crystal growth apparatus. 1 is an organometallic bubbler, 2 is a raw material gas cylinder, 3 is a mass flow controller, 4 is a reaction tube, 5 is a substrate crystal,
6 is an RF coil, 7 is a bypass line, and 8 is a quantitative analyzer. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] (1) In a semiconductor crystal growth apparatus that grows compound semiconductor crystals using the metal organic chemical vapor deposition (MOCVD) method, a bypass line installed near the growth gas inlet of the reaction tube and infrared spectroscopy or Raman spectroscopy A semiconductor crystal growth apparatus comprising: a quantitative analysis device for monitoring the concentration and composition of the source gas branched into the bypass line.