JPS6034253B2 - Liquid phase epitaxial growth method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a liquid phase epitaxial growth method.

Generally, methods for manufacturing semiconductor devices using a liquid phase include methods using a temperature drop method, methods using a temperature difference method, and the like. In the former method, a melt tank filled with a raw material semiconductor melt is slowly cooled to a supersaturated state, and crystals are grown on a substrate. In the latter case, a temperature difference is provided in the melt tank, and the raw semiconductor melt is moved from the high temperature side to the low temperature side by thermal diffusion or density diffusion, and the low temperature side is brought into a supersaturated state, and crystals are formed on the substrate placed on the low temperature side. It was designed to encourage growth. However, all of these methods have the following drawbacks.

In other words, in the case of the temperature drop method, it is necessary to raise and lower the temperature for each growth, making it impossible to grow continuously, resulting in poor workability and poor reproducibility. It is. Furthermore, the impurity distribution in the growth layer grown on the substrate tends to be non-uniform, resulting in deterioration of characteristics. In the case of the temperature difference method, workability and reproducibility can be improved, but since the melt near the substrate is kept at the crystal growth temperature in advance, crystal growth starts suddenly when the substrate is positioned. Lattice defects, lattice distortion, etc. are likely to occur, and it is difficult to control such rapid crystal growth. When manufacturing a semiconductor device by liquid phase growth, it is naturally preferable that there are no lattice defects or lattice distortions in the crystal, and especially in the case of a light emitting diode, the junction which is related to the electron injection rate into the P-type region is preferable. Unless the crystal integrity near the part is required and the probability of non-radiative recombination is reduced, it will be of poor practical use.

The present invention has been devised in consideration of the above circumstances, and provides a liquid phase epitaxial growth method that is flexible and reproducible in mass production, and can yield crystals free of lattice defects.

For this purpose, the present invention first sets the temperature difference between one end and the other end of the melt in contact with the substrate to zero or a small difference, and then monotonically and gradually creates a temperature difference in the melt to reach the crystal precipitation temperature. The gist of this method is to obtain epitaxial crystals on the substrate while maintaining this state. Therefore, according to the present invention, crystal initiation is performed extremely slowly, so that crystal growth progresses gradually without undue stress, and a liquid-phase epitaxial crystal free of lattice distortion, lattice defects, etc. can be obtained. An embodiment of the present invention will be described below with reference to the drawings.

1 is a quartz tube constituting a growth system, 2 is a melt tank placed inside the quartz tube, and 3 is a raw material semiconductor melt.

4 is a slider disposed slidably on the bottom of the melt tank 2, and 5 is a semiconductor substrate placed on the top surface of the slider.

The substrate 5 remounted on the slider 4 is located at a stop (not shown) at the bottom of the melt tank 2 when the slider 4 is moved, so that the upper surface of the substrate 5 and the melt 3 come into contact with each other. 6 is a heater for heating the melt 3 in the quartz tube 1, and 7 is a cooling device for cooling a part of the melt 3 and creating a temperature difference between the slider 4 side and the pond end.

Note that the details will be explained later. In addition, although one melt tank 2 is shown in this figure, in actual equipment, multiple melt tanks each containing melts with different impurity concentrations or with different conductivities such as N-type and P-type are used. are arranged, and by moving the slider 4, crystal growth of multiple layers can be successively obtained on the substrate 5. Next, melt temperature control will be explained.

The melt 3 in the melt tank 2 has a certain temperature difference △ between the vicinity of the substrate 5 and the other end in the same machine as when crystal growth is performed by the temperature difference method.
T is provided so that a melt saturable state always exists in the vicinity of the substrate 5.

Note that this temperature difference ΔT is a temperature suitable for obtaining epitaxial crystal growth on the substrate 5. FIG. 2 shows the temporal change in the temperature difference ΔT occurring in the melt 3 in the melt tank. That is, the temperature difference ΔT was set to be suitable for crystal growth (section A in the figure), and then the cooling device 7 was operated to gradually increase the temperature on the slider 4 side, causing melt to occur at both ends of the melt. The temperature difference ΔT is set to zero or a value close to this (section B in the figure). After this, operate the cooling device 7 again to gradually cool the four sliders so that the melt overflows the slider 4 side (section C in the figure) to the original temperature difference △T, and repeat this operation from now on. This is what I did. Next, the operation for epitaxial crystal growth on the substrate 5 will be explained with reference to FIG.

That is, the temperature difference △T that was previously passed through crystal growth by the temperature difference method
The point when the temperature of the melt controlled to be almost uniform (second
Move the slider 4 (part B) to place the substrate 5 into the melt tank 2.
(Part B' in Figure 3). At this point, the entire melt is in a uniformly saturated state, so no crystal growth occurs on the substrate 5. Next, as shown in part C of Figure 2, a temperature difference gradually occurs, and as a result, crystal growth begins little by little on the substrate (part '' in Figure 3), and when the temperature difference reaches the normal temperature difference △T, it becomes constant. Growth in speed is made.

Note that the thickness of the grown layer is determined by adjusting the time in the A' portion after the temperature difference ΔT is reached. Although not shown in the figure, when growing multiple layers with different conductivities, continuous crystallization can be achieved by simultaneously operating melt tanks containing various types of melt placed side by side while repeating the same temperature control. It is possible to grow. As explained above, in this invention, the substrate is set with almost no temperature difference between the slider side of the melt and the pond edge, and then a temperature difference is gradually generated to cause crystal growth to occur sequentially. Since it is a method, the operation can be performed continuously and a reproducible method can be provided.

In particular, according to the present invention, since the one end of the substrate side gradually progresses to the saturated state from the point where the melt is in the saturated state,
Crystal initiation becomes extremely gradual, and a crystal with an ideal lattice arrangement without lattice distortion or lattice defects can be obtained.

Therefore, for example, if layers with different conductivities are grown,
If lattice distortion, lattice defects, etc. occur at the bonding surface, the characteristics as a semiconductor will be significantly impaired, but in this invention, since the crystallization is extremely gradual, such inconveniences can be avoided. will not occur. For this reason, even when obtaining crystals such as light emitting diodes, for example, no distortion or lattice defects occur at the junctions of the conductive regions, resulting in a crystal with a significantly reduced probability of non-radiative recombination. Therefore, it is possible to achieve good luminous efficiency. Furthermore, since a part of the melt requires only slight temperature control to reach a state where there is almost no temperature difference from the crystal precipitation temperature, it is possible to grow the next substrate after completing the growth of one substrate. The production time is short and it is effective for mass production.

Further, the temperature difference can be set by increasing the temperature of the raw material supply section that changes the overall temperature distribution, by flooding the crystal growth section, etc., but it is preferable to flood the crystal growth section as described in the embodiment. good.

Changing the overall temperature distribution increases the degree of instability, and depending on how the change is made, it is likely to cause various drawbacks. Elevating the temperature of the raw material supply section does not have the drawbacks of a round furnace for one epitaxial growth, but it poses a problem when attempting to sequentially perform multiple epitaxial growths. That is, when the entire melt is brought to a uniform temperature in preparation for the next epitaxial growth, the raw material supply section overflows. Therefore, supersaturation occurs, causing undesirable crystallization, increased instability in the early stage of growth, and the like.

[Brief explanation of the drawing]

FIG. 1 is a schematic explanatory diagram showing an embodiment of the present invention, FIG. 2 shows the temperature difference of the melt over time, and FIG. 3 shows the crystal growth rate. 1...Quartz tube, 2...Melt tank, 3.
...Melt, 4...Slider, 5...
- Substrate, 6... Heater, 7... Cooling device. Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] 1. The temperature difference between one end of the melt in the melt tank and the other end in contact with the substrate is reduced in advance and controlled to the extent that crystals do not precipitate on the substrate, and then the slider is moved to remove the substrate. The substrate is placed at one end of the melt, and then a temperature difference is monotonically and gradually created in the melt to create a temperature difference suitable for crystal precipitation, and while this state is maintained, epitaxial crystal growth is obtained on the substrate, and each of the above steps is performed. A liquid phase epitaxial growth method characterized by repeatedly growing epitaxial crystals on a plurality of substrates. 2. The liquid phase epitaxial growth method according to claim 1, wherein the temperature difference between the melt near the substrate and the other end is obtained by arranging a cooling member near the substrate. 3. Claims 1 to 2, wherein a plurality of melt tanks are prepared and each step is performed in each melt tank to sequentially perform multilayer epitaxial growth on the substrate.
The liquid phase epitaxial growth method described in .