JPH0328187A - Method for liquid-phase epitaxial growth - Google Patents

Abstract

PURPOSE:To ensure nearly homogeneous growth over the whole surface of a semiconductor substrate by regulating the thickness of a raw material melt in the vertical directions of the semiconductor substrate and, as necessary, in the radial direction. CONSTITUTION:The bottom of each pan 2 having a cylindrical sidewall 5 with a cutout 6 for admitting and discharging a raw material melt 4 is slightly tilted so as to facilitate separation of the raw material melt 4. A semiconductor substrate 1 in a tilted state is superposed on the pan 2 and housed in a cassette 3, which is then dipped in the raw material melt 4 to carry out liquid-phase epitaxial growth while thinly keeping the thickness of the raw material melt 4 specified with the undersurface of the pan 2 just on the substrate 1 to the upper part of the tilted pan 2.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a semiconductor substrate "2" GaAs, A]GaAs
, InCaAsP, etc., and is particularly suitable for manufacturing light emitting diode elements and the like.

(Prior art) Conventionally, in order to perform liquid phase epitaxial growth by bringing a semiconductor substrate into contact with a melting material consisting of a solvent, a solute, and a dopant, and depositing sludge, it is necessary to move the semiconductor substrate horizontally to melt the material. A slide boat device that contacts and separates the liquid and a semiconductor lλ plate are supported by a receiving tray, a large number of the receiving books are stacked and stored in a cassette, and the cassette 1 is placed in a vertical container that accommodates the raw material melt. Vertical dipping device 1d that forms an epitaxial layer by dipping and separates it from the raw material melt
There is.

FIG. 6 is an explanatory diagram showing the operating procedure of the vertical dipping device. Figure 4 (a) shows a raw material melt 4 in a vertical container 5.
The tray 2 containing the semiconductor 7^ board 1 is stacked inside the cassette 3, and FIG.
is immersed in the raw material melt, and the raw material melt 4 is placed on the semiconductor substrate l.
FIG. 3(c) shows the state in which the cassette 3 is pulled up from the raw material melt 4 after the liquid phase epitaxial growth is completed.

In Japanese Patent Application Laid-open No. 61-261291, there is
, an apparatus is described in which a multilayer epitaxial layer is formed by sequentially introducing and discharging different raw material melts while the materials are placed in a vertical container.

(Problems to be Solved by the Invention) Conventional vertical dipping equipment can perform liquid phase epitaxial growth on a large number of semiconductor substrates at the same time, so it has excellent mass productivity. Accompanied by distribution. In this apparatus, the substrate is tilted in order to separate the raw material melt from the semiconductor substrate in a short time after epitaxial growth. That is, if the thickness of the raw material melt on a sloped semiconductor substrate is kept uniform and liquid phase growth is performed, the epitaxial layer thickness becomes thinner downward with respect to the slope. Therefore, it is conceivable to hold the semiconductor substrate horizontally during crystal growth and tilt the entire growth furnace when separating it from the raw material melt, but this would complicate the apparatus.

Therefore, the present invention eliminates the drawbacks of the conventional liquid phase epitaxial growth method, and by adjusting the thickness of the raw material melt in the vertical direction of the semiconductor substrate and in the radial direction as necessary, the thickness is almost uniform over the entire surface of the semiconductor substrate. The present invention aims to provide a liquid phase epitaxial growth method that ensures a high growth rate and forms an epitaxial layer of uniform thickness.

(Means for Solving the Problems) The present invention provides (1) placing semiconductor substrates on saucers, stacking the saucers in an inclined state and storing them in a cassette, and immersing the cassette in a raw material melt. In a method of liquid phase epitaxial growth on a substrate, crystal growth is performed while keeping the thickness of the raw material melt defined by the lower surface of the saucer directly above the substrate thinner toward the top of the inclined saucer. (2) A liquid phase epitaxial growth method characterized by: (2) thinning the thickness of the raw material melt toward one or two sides of the inclined saucer, and maintaining the center thinner than the periphery to grow crystals; The liquid phase epitaxial growth method described in item 0) above is characterized in that:

(Function) FIG. 1 is an enlarged view of the inside of a cassette of a vertical sanitary liquid phase lengthening device for carrying out the present invention, and FIG. 2 is a perspective view of a saucer used in the device of FIG. 1. The receiver 2 is a cylindrical side wall 5
The bottom surface supporting the semiconductor substrate is slightly inclined to allow separation of the raw material melt, and has a notch 6 for inflow and outflow of the raw material melt.

The side wall 5 is housed along the inner wall of the cassette 3. The height of the side wall 5 is the same, and the semiconductor substrate I mounted on the bottom surface of the receiver is held tilted at a constant interval.
Raw material melt 4 for "semiconductor substrate, which is the first feature of the present invention"
In order to make the thickness of the receptacle thinner upward, the thickness of the bottom of the receptacle is made thicker upward.

FIG. 3 is a sectional view of one specific example of the saucer.

Note that the figure is drawn with cutouts omitted for ease of understanding.

In this way, the portion of the semiconductor substrate located above the saucer originally grows faster than the portion below in liquid phase epitaxial growth, so by reducing the thickness of the raw material melt, the growth rate is suppressed. The growth rate of the part of the semiconductor substrate that is placed downward is originally slow, so by increasing the thickness of the raw material melt, the growth rate is increased and the growth rate is almost uniform over the entire surface of the semiconductor substrate. A thick epitaxial layer is formed.

FIG. 4 shows a modification of the saucer shown in FIG. 3, and is another specific example of the present invention. In this case, in the radial direction of the semiconductor substrate, the growth rate is faster at the center than at the periphery.
We discovered that the center of the epitaxial layer is thicker, so we created a convex surface with a slightly raised center on the lower surface of the saucer shown in Figure 3, and made the thickness of the raw material melt in the center thinner than in the surroundings. , the epitaxial layer thickness is made uniform by suppressing the growth rate and making the growth rate uniform in the radial direction.

(Example) Using the saucer shown in Fig. 3, Fig. 4, and Fig. 5,
Zinc dove with a thickness of 300μ, surface orientation (100) with 0 questions
A zinc-doped ^1 (iaAs epitaxial layer) was formed on a GaAs substrate. FIGS. 3 and 4 show a receiver according to the present invention, and FIG. 5 shows a conventional receiver.

The booklet shown in Figure 3 has a circular shape with a lower surface inclined 10" from the horizontal, a diameter of 51 am, and a side wall height of 4.4 mm.
■The thickness of the bottom is 1.8■ at the top and 1.0se at the bottom.
It is s. '' Prepare seven saucers, attach semiconductor substrates to the bottom six, stack these saucers, and store them in a cassette. Ta.

In the vertical container, 200g of Ga, rollmg of AI,
8g of GaAs multilayer, 2g of zinc as a dopant
QQw+g was charged and melted by heating to 900° C. in a high-purity hydrogen atmosphere. Next, the cassette described in "2" was immersed in the raw material melt, and the temperature was lowered to 600° C. at a cooling rate of 0.3° C./sin, during which epitaxial growth was performed on the semiconductor substrate. At that time, the raw material melt port size is 2. 6am and 3.4m at the bottom.

The saucer in Figure 4 has a 0.4mm center on the bottom surface of the saucer in Figure 3.
of~. A convex surface is added to increase the thickness, and the thickness of the raw material melt at the center is 0.4 mm thinner than at the surroundings. Other conditions were the same as above.

The saucer shown in Figure 5 has a bottom thickness of l. h + s, the thickness of the raw material melt is 3.0 questions and is uniform over the entire surface, and the other conditions are
It was the same as the second book.

The obtained epitaxial wafer is 21 shown in FIG.
The thickness of the epitaxial layer at certain points was measured and its distribution investigated.

First, FIG. 9 shows the thickness of the epitaxial layer formed using the conventional saucer shown in FIG.
This is a graph showing the average value of the epitaxial layer thickness at the top and bottom positions, and the maximum and minimum difference in epitaxial layer thickness at the top and bottom positions is 14 μm, whereas the epitaxial layer formed using the saucer in FIG. As described above, the maximum and minimum difference in epitaxial layer thickness could be significantly suppressed to only 4 μm.

Furthermore, Fig. 11 is a graph showing the average plot of the 1v distribution in the radial direction from the center of the epitaxial layer obtained with the saucer shown in Fig. 5, and the maximum and minimum differences between the center and the periphery are 7
In contrast, the epitaxial layer obtained using the saucer shown in FIG. 4 had a maximum and minimum difference of 3 μ, as shown in FIG. 10, and the uniformity was even better.

(Effects of the Invention) The present invention employs the configuration described in section 2 to provide a method for applying a raw material melt on a semiconductor substrate when performing liquid phase growth on an inclined semiconductor Jk plate using a vertical dipping device. By adjusting the thickness, the growth rate on the semiconductor substrate can be adjusted uniformly over the entire surface, and it has become extremely easy to form a liquid phase epitaxial layer with a uniform thickness.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the internal structure of a cassette of a liquid phase epitaxial growth apparatus for carrying out the present invention, FIG. 2 is a perspective view of the receiver used in FIG. 1, and FIGS. 3 and 4. 5 is an enlarged sectional view of a specific saucer used in the examples, FIG. 5 is an enlarged sectional view of a conventional saucer, and FIGS. 6(a) to (c) are explanatory diagrams showing the fabrication procedure of the liquid phase epitaxial growth method. FIG. 7 is an explanatory diagram showing measurement points of epitaxial layers obtained in Examples and Comparative Examples, and FIGS. 8 and 9 are epitaxial layers obtained using the saucers of FIGS. 3 and 5. Graphs showing the average thickness distribution in the vertical direction, Figures 10 and 11
The figure is a graph showing the average thickness distribution in the radial direction from the center of the epitaxial layer obtained using the saucers of FIGS. 4 and 5. Fig. 8 ■ T[ [IV

Claims (2)

[Claims] (1) In a method in which semiconductor substrates are placed on a saucer, the saucers are stacked in an inclined state and stored in a cassette, and the cassette is immersed in a raw material melt to perform liquid phase epitaxial growth on the substrate, the semiconductor substrate is directly placed on the substrate. A liquid phase epitaxial growth method characterized in that crystal growth is performed while the thickness of the raw material melt defined by the lower surface of the saucer is kept thinner toward the top of the inclined saucer. (2) The liquid according to claim (1), wherein the thickness of the raw material melt is made thinner toward the top of the inclined saucer, and crystal growth is performed while keeping the center thinner than the periphery. Phase epitaxial growth method.