JPH10163118A - Apparatus and method for chemical vapor deposition of compd. semiconductor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the variation of the mixed crystal compsn. ratio, by mounting liq. material vessels through drain pipings on the top of a liq. material bubbler for bubbling a carrier gas by means of a gas feed piping and controlling the temps. of these vessels using heaters. SOLUTION: A liq. material vessel 2 is mounted through a gas discharge pipe 12 on the top of a liq. material bubbler 1 for bubbling a carrier gas by means of a gas feed pipe 9 in Hg 7 to be a liq. raw material fed in the bubbler 1, until the carrier gas is saturated with the vapor of Hg 7, and it is fed from the gas discharge pipe 12 while the bubbler 1 is heated at 230 deg.C by a heater 3. Liq. material vessel 2 is heated at 200 deg.C by heaters 4 to separately control their temps., whereby the feed rate of Hg 7 is always const., resulting in a few compsn. variation in the thickness direction of a grown layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus and a method for vapor growth of ternary or more compound semiconductor crystals.

[0002]

2. Description of the Related Art Mercury cadmium telluride (Hg _1-X Cd _X
Te) is a mixed crystal of cadmium tellurium and mercury tellurium, and the energy gap can be changed by changing the composition ratio X of the mixed crystal. Even if the composition of mercury cadmium tellurium is slightly shifted, the energy gap changes. For this reason, in a composite type infrared detector in which a mercury cadmium tellurium crystal is configured as a photodetector, accurate control of the composition is required because the composition shift affects the response wavelength. Therefore, in order to form mercury cadmium tellurium on a substrate by the vapor phase growth method, it is necessary to precisely control the supply amounts of the respective raw materials.

In a semiconductor vapor phase epitaxial growth apparatus in which such precise composition control is desired, it is necessary to keep the temperature of the raw material, especially the liquid raw material constant, in order to stably supply the raw material.

As an example, MOCVD (Metalor)
ganic Chemical Vapor Depo
FIG. 4 shows an apparatus and a method for supplying mercury, which is a liquid raw material, in the growth of mercury cadmium tellurium by the position method.

[0005] Mercury cadmium tellurium uses organic metal materials such as dimethyl cadmium and diisopropyl tellurium as raw materials for cadmium and tellurium, and metal mercury as a raw material for mercury.

FIG. 4 is a schematic sectional view of a conventional mercury supply device. Reference numeral 1 denotes a bubbler for a liquid raw material, which is provided with a gas introduction pipe 9 and a gas discharge pipe 12, and bubbling a carrier gas, for example, hydrogen from the gas introduction pipe 9 in the mercury 7 put in the bubbler 1, and It is saturated with steam and sent from the gas discharge pipe 12 to the next piping system. Since metallic mercury has a very low vapor pressure at room temperature, the heater 3 is heated and kept at about 200 ° C. by the heater 3. The carrier gas saturated with the mercury vapor is mixed with other raw materials in the reaction tube and thermally decomposed on the heated substrate for epitaxial growth to form mercury cadmium tellurium crystal.

[0007]

As described above, the mercury bubbler needs to be heated and kept at about 200 ° C. For this, there is a method in which the entire container is put in a heat retaining liquid such as oil to make the temperature uniform, but it is dangerous if the heat retaining liquid heated to a high temperature spills. On the other hand, when directly heating with a heater or the like, it is difficult to keep the temperature of the entire container uniform, and a temperature difference occurs inside the container. Therefore, when the mercury level decreases due to a decrease in the remaining amount of mercury and the mercury temperature fluctuates, the mercury vapor pressure fluctuates. Moreover, the thermal conductivity of mercury is low, and it is difficult to follow the fluctuation of the ambient temperature. As a result, as shown in FIG. 5, there is a problem that the composition of the epitaxially grown crystal changes every time the crystal is grown.

FIG. 5 shows the number of times of growth (times) on the horizontal axis and the mixed crystal composition ratio (X) on the vertical axis. Further, the mixed crystal composition ratio (X) may vary in the thickness direction of the growth layer.

The supply amount of mercury can be controlled by the flow rate of the carrier gas. In this case, it is assumed that the mercury temperature is constant. However, if the vessel temperature is 2
Since the temperature has risen to around 00 ° C, the mercury vapor pressure also fluctuates due to slight fluctuations in the temperature of the container and a drop in the liquid level.
Affects the composition of the mercury cadmium tellurium growth layer. The present invention has been made in consideration of the above circumstances, and when a compound semiconductor layer is vapor-phase epitaxially grown on a substrate,
It is an object of the present invention to provide a growth apparatus and a growth method in which the mixed crystal composition ratio is small.

[0010]

The present invention relates to an apparatus and a method for vapor-phase epitaxial growth of a compound semiconductor. The present invention relates to a liquid source bubbler 1 which is bubbled with a carrier gas by a gas introduction pipe 9 and a liquid source bubbler 1 via a discharge pipe 12. Containers 2 are provided, and the temperature of each container is controlled by a heater for heating.

Further, the temperature of the liquid source container 2 is set to be the lowest in the piping system from the liquid source bubbler 1 to the reaction tube.

Further, the volume of the liquid raw material container 2 is smaller than the volume of the liquid raw material bubbler 1.

Further, the liquid raw material exceeding a certain amount is caused to overflow, so that the amount of the liquid raw material in the liquid raw material container 2 is made constant.

Further, the present invention is characterized in that a liquid source vapor provided with a baffle plate in the liquid source container 2 is liquefied.

Further, a cooling pipe for controlling the temperature of the liquid material container 2 is provided.

According to the apparatus and method for vapor-phase epitaxial growth of a compound semiconductor according to the present invention, the raw material reacts irrespective of fluctuations in the ambient temperature of the liquid raw material bubbler and fluctuations in the vapor pressure caused by a decrease in the liquid level caused by the temperature difference in the container. Can be supplied without change in the pipe. Thus, it is possible to provide an epitaxial vapor-phase grown layer of a compound semiconductor having a small variation in the mixed crystal composition ratio during the growth and good reproducibility of the mixed crystal composition ratio for each growth.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described with reference to the drawings, in which mercury is used as a liquid material.

FIG. 1 is a schematic sectional view of a liquid material supply apparatus according to the present invention. Reference numeral 1 denotes a liquid source bubbler, which includes a gas introduction pipe 9 and a gas discharge pipe 12. The carrier gas, for example, hydrogen is bubbled from the gas introduction pipe 9 through the liquid source (mercury) 7 put in the bubbler 1. Is saturated with the vapor of mercury 7 and sent from the gas discharge pipe 12 to the next liquid source container 2. Reference numeral 1 denotes a cylindrical container having a diameter of about 10 cm and a height of about 10 cm, and a liquid raw material container 2 is disposed above the liquid container 2 via a gas discharge pipe 12. The liquid material container 2 has a diameter of 5
cm and a height of about 3 cm. The gas discharge pipe 12 is a vertical bubbler 1 for liquid raw material, and a liquid raw material container 2
And concatenate.

The downstream open end of the gas discharge pipe 12 is located at a height of 1 cm to 2 cm from the bottom of the liquid raw material container 2.
A liquid material (mercury) reservoir 8 is formed on the gas discharge pipe 12 including the downstream opening end and the bottom surface and the inner peripheral surface of the liquid material container 2. Mercury that has accumulated in the liquid source container 2 at a depth equal to or greater than the depth from the bottom surface to the downstream opening end overflows from the downstream opening end and returns to the bubbler 1. For this reason, the amount of the liquid material (mercury) in the liquid material container 2 is constant.

The bubbler 1 was heated to 230 ° C. by the heater 3, and the temperature of the liquid raw material container 2 was individually controlled to 200 ° C. by the heater 4. Numerals 5 and 6 are thermocouples for detecting temperature. In addition, by passing a cooling gas capable of transporting heat such as air around the liquid material container 2 through the pipes 10 and 11,
Further, the temperature controllability can be improved.

The gas discharge pipe 12 in the liquid raw material container 2
A baffle plate 13 is arranged between the downstream open end of the container and the outlet from the liquid source container 2 so that the carrier gas can sufficiently exchange the temperature with the inner wall of the liquid source container 2 and the vapor pressure of the mercury in the carrier gas decreases. The temperature is regulated by the temperature of the inner wall of the container 2.

The path between the bubbler 1 and the liquid source container 2 and the path from the liquid source container 2 to the reaction tube (not shown) were also provided with a heating means for preventing the adhesion of mercury, and were heated to 230 ° C. That is, the temperature of the liquid source container 2 was controlled to be the lowest in the path to the reaction tube, and the mercury vapor pressure was regulated by the temperature of the liquid source container 2.

FIG. 2 shows the temperature distribution in the path from the bubbler 1 to the liquid source container 2 and beyond. The left side of FIG. 2 shows a schematic cross-sectional view of the path from the bubbler 1 through the liquid raw material container 2 to the end, and the right side shows the temperature (° C.) corresponding to the position on the horizontal axis.

As can be seen from FIG. 2, when the liquid material container 2 is not provided, the temperature distribution of the bubbler 1 has a difference of about 20 ° C. between the upper and lower sides of the bubbler. Therefore, the temperature of the liquid surface changes depending on the remaining amount of mercury, that is, the height of the liquid surface, so that the vapor pressure fluctuates, and the mercury raw material cannot be supplied at a constant time. Further, when the ambient temperature fluctuates, it takes time for the bubbler 1 having a large capacity to equalize the temperature of mercury having poor thermal conductivity. On the other hand, the temperature difference in the liquid raw material container 2 is very small, the temperature control is easy, and the temperature is kept constant. Further, since the liquid level is also kept constant by the overflow mechanism, there is almost no change in the mercury vapor pressure due to fluctuations in the remaining amount and the ambient temperature.

A hydrogen carrier gas at a rate of 500 cc / min was bubbled through the mercury from the bubbler 1 through the liquid material container 2 and introduced into the reaction tube. Simultaneously, dimethyl cadmium and diisopropyl tellurium were also transported to the reaction tube with a hydrogen carrier gas, and mercury cadmium tellurium was deposited on a cadmium zinc tellurium substrate heated to about 400 ° C. to a thickness of 10 mm.
μm was grown.

Mercury cadmium telluride (Hg _{1 -X} Cd _X T
The value (X value) of the cadmium composition in e) was calculated by measuring the infrared transmission characteristics and determining the band gap thereof. The result is shown in FIG. FIG. 3 shows the number of growth times on the horizontal axis and the value (X value) of the cadmium composition on the vertical axis.
As can be seen in FIG. 3, the X value is X = 0.230 ±
The content can be kept within the range of 0.005, and the reproducibility of the composition for each growth is greatly improved.

In this embodiment, the epitaxial vapor phase growth of mercury cadmium tellurium has been described. But,
The present invention is not limited to this, but is also applicable to epitaxial vapor deposition of other compound semiconductors using a liquid source.

[0028]

According to the present invention, the supply amount of the liquid raw material can be constantly controlled.

As a result, it is possible to provide an apparatus and a method for growing a semiconductor growth layer in which the composition variation in the thickness direction of the growth layer is small and the composition reproducibility is excellent for each growth.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view illustrating the present invention.

FIG. 2 is a graph showing a temperature distribution of the device of the present invention.

FIG. 3 is a graph illustrating the present invention.

FIG. 4 is a schematic sectional view illustrating a conventional example.

FIG. 5 is a graph illustrating a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Bubbler for liquid raw materials 2 ... Liquid raw material container 3 ... Heater 4 ... Heater 5 ... Thermocouple 6 ... Thermocouple 7 ... Liquid raw material (mercury) 8 ... Liquid raw material pool 9 ... Gas introduction piping 10 ... Cooling gas introduction piping 11 ... Cooling gas discharge pipe 12 ... Gas discharge pipe 13 ... Baffle plate

Claims (12)

[Claims] In a compound semiconductor vapor phase growth apparatus for producing a ternary or more mixed crystal semiconductor crystal, a liquid raw material bubbler is provided.
A heating heater 3 for heating the liquid raw material in the liquid raw material bubbler 1, a gas introducing pipe 9 for introducing a carrier gas into the liquid raw material of the liquid raw material bubbler 1,
A liquid material container 2 connected to the upper portion of the liquid material bubbler 1 via a discharge pipe 12 from the liquid material bubbler 1
And a heating source 4 for heating the liquid source container 2. 2. The compound semiconductor gas according to claim 1, wherein the temperature of the liquid source container 2 controlled by the heater 4 is minimized in a piping system from the liquid source bubbler 1 to the reaction tube. Phase growth equipment. 3. The compound semiconductor vapor phase growth apparatus according to claim 1, wherein the volume of the liquid source container is smaller than the volume of the liquid source bubbler. 4. The apparatus for vapor-phase growth of a compound semiconductor according to claim 1, wherein a liquid source exceeding a certain amount overflows, and the amount of the liquid source in the liquid source container 2 is kept constant. 5. The compound semiconductor vapor phase growth apparatus according to claim 1, wherein a baffle plate is provided in the liquid source container 2. 6. An apparatus according to claim 2, further comprising a cooling pipe for controlling a temperature of the liquid source container. 7. In a method for producing a compound semiconductor vapor phase in which a mixed crystal of three or more elements is produced, a liquid source charged in a liquid source bubbler 1 heated by a heater 3 is supplied from a gas introduction pipe 9 to a carrier. A step of bubbling the gas, saturating the carrier gas with the vapor of the liquid raw material and sending it from the discharge pipe 12, and connecting the saturated gas sent by the discharge pipe 12 to the upper portion of the liquid raw material bubbler 1 via the discharge pipe 12. Sent to the liquid material container 2
A step of storing a liquid source and heating it with a heater 4. 8. The compound semiconductor gas according to claim 7, wherein the temperature of the liquid source container 2 controlled by the heater 4 is the lowest in the piping system from the liquid source bubbler 1 to the reaction tube. Phase growth method. 9. The method according to claim 2, wherein the volume of the liquid source container is smaller than the volume of the liquid source bubbler. 10. The method according to claim 7, wherein a liquid raw material exceeding a certain amount overflows, and the amount of the liquid raw material in the liquid raw material container 2 is kept constant. 11. A liquid source vapor is liquefied by providing a baffle plate in the liquid source container 2.
The vapor phase growth method of the compound semiconductor according to the above. 12. The method according to claim 8, wherein a cooling pipe for controlling the temperature of the liquid source container 2 is provided.