JPH0784359B2 - Liquid phase epitaxial growth system - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a growth apparatus used for multi-layer liquid phase epitaxial growth, and particularly to obtain an epitaxial wafer having good in-plane uniformity of characteristics and a good epitaxial layer surface condition. It is suitable for.

[Conventional technology]

Epitaxial growth layers of III-V compound semiconductors are used for optical devices such as light emitting diodes and laser diodes,
Widely applied to high speed devices such as FETs. Furthermore, recently, in order to improve device performance, a fine structure in which semiconductor thin films of several to several tens of angstroms are stacked is required. Such a thin film laminated structure is produced by a vapor phase or liquid phase epitaxial growth method.

A slide boat as shown in FIG. 4 is generally used for liquid phase growth of a plurality of epitaxial layers on a compound semiconductor substrate. For example, when growing three epitaxial layers, the substrate 14 is placed in the substrate housing recess 13 on the bottom plate 9, and the melt slider 10 which is slidable relative to the bottom plate 9 is placed thereon. The melt accommodating portions 11, 11 ′ and 11 ″ of the melt slider 10 each have a growth melt 12 having a composition necessary for growing an intended epitaxial layer,
12 ′ and 12 ″ are housed. In this state, the slide boat is inserted into an epitaxial growth furnace (not shown), and H ₂
The temperature is raised to a predetermined temperature in an atmosphere gas such as a gas or an inert gas. After the growth melt becomes uniform, the melt slider 10 is slid in the direction of the arrow so that the substrate 14 and the first
And contact it with the growth melt 12. In this state, the temperature inside the furnace is gradually cooled to grow the first epitaxial layer on the substrate 14. After growing a certain amount of epitaxial layer,
Slide the melt slider 10 further in the direction of the arrow,
The substrate 14 and the melt 12 are separated. Next, the second epitaxial layer is grown by bringing it into contact with the melt 12 'and slowly cooling it again.
Similarly, after the growth of the third epitaxial layer is completed, the substrate 14 and the melt 12 ″ are separated and allowed to cool.

[Problems to be Solved by the Invention]

In the above method, the depth of the substrate storage recess 13 on the bottom plate 9 is
In order that the bottom plate 9 and the melt slider 10 can slide, the thickness is made deeper than the thickness of the wafer after the epitaxial layer growth.
Therefore, when separating the substrate 14 and the growth melt 12, the substrate 14
In addition, a gap is formed between the melt slider 10 and the bottom of the melt slider 10, and the growth melt 12 cannot be completely separated, and a part remains on the substrate 14. When the substrate is contacted with the next melt, this substrate 14
Since the melt 12 remaining on the top is brought into the next melt, the composition of the melt is changed, an epitaxial layer having a desired composition cannot be obtained, and the variation of the epitaxial growth layer composition within the wafer surface also becomes large. is there. In addition, when the melt is separated from the substrate after the growth of the final epitaxial layer, if a part of the melt remains on the substrate 14, the trace of the melt is attached to the surface of the epitaxial layer, and a good epitaxial layer surface cannot be obtained. There is also.

Further, when the melt slider 10 is slid, scratches may occur on the surface of the wafer due to friction with the polycrystalline crystallized substances or the like deposited in the melt 12 or in the peripheral portion of the substrate 14 or the like. Regarding mass productivity, for example, in the case of growing three layers, three growth melts are required for one substrate, and mass productivity is poor.

As a means for obtaining an epitaxial growth layer having a good surface condition, there is a vertical (dip method) liquid phase growth method. In the vertical method, the substrate is immersed in the melt contained in the melt reservoir for epitaxial growth, and after the growth is completed, the substrate is pulled up so that the growth melt does not remain on the surface of the substrate. The present applicant has also previously proposed an apparatus for multi-layer epitaxial growth (see Japanese Patent Laid-Open No. 62-83398). This apparatus has a plurality of solution baths arranged on the circumference so as to be rotatable, and the substrate holder on which the substrate is set is sequentially transferred from the first growth bath to carry out continuous epitaxial layer formation. It grows. In this method, when the number of epitaxial layers is increased, the inner diameter of the reaction tube in the growth furnace that houses the solution layer must be increased, and when the number of substrates processed at one time is increased, the diameter of the reaction tube is increased. Must. The reaction tube is usually made of high-purity quartz, but the maximum diameter is about 40 cm both in terms of strength and economy, and a reaction tube with a larger diameter is not practical. In other words, even if the number of sheets processed at one time is increased and mass production is attempted, there are restrictions on the apparatus.

On the other hand, in the method of the present invention, it is not necessary to increase the diameter of the reaction tube, and it is possible to increase the size and number of the solution tanks by increasing the length while maintaining the conventional diameter. Is also an excellent method.

[Means for Solving the Problems]

The present inventor conducted research to solve the above-mentioned drawbacks, conceived a liquid phase epitaxial growth apparatus having a new structure, and found that the above-mentioned drawbacks can be solved by an epitaxial growth method using this apparatus. In the growth method according to the present invention, by vertically moving the substrate holder holding the substrate vertically or obliquely at a fixed position, it is immersed in the growth melt in the growth melt reservoir installed below the substrate holder and melted. And the substrate are contacted and separated. The growth melt is moved by sequentially sliding the melt pool linearly with respect to the substrate holder while the substrate holder is being moved upward. A plurality of epitaxial baths are grown on the substrate by combining contact separation of the substrate and the growth melt by moving the substrate holder in the vertical direction and movement of the melt reservoir in the linear direction. According to this method, the substrate and the growth melt are separated from each other by pulling up the substrate from the growth melt, so that the growth melt drops by gravity and hardly remains on the substrate. Therefore, since the melt is not brought into the next growth melt, an epitaxial layer having a desired composition can be obtained with good reproducibility and uniformity can be improved. Since the substrate holding portion of the substrate holder does not slide with other portions of the apparatus, no scratch is generated on the wafer surface. Further, since it is possible to epitaxially grow on a plurality of substrates with one set (three in the case of three-layer epitaxial) of the melt pool, mass productivity is greatly improved as compared with the conventional slide boat method. The number of substrates to be processed can be increased without increasing the diameter of the reaction tube by increasing the length in the longitudinal direction.

The apparatus used in this method has a plurality of growth melt reservoirs that are movable in a linear direction, a substrate holder that is movable in the vertical direction, and a slider that is in contact with the side surface of the substrate holder and is movable in the linear direction. An oblique groove is formed, and a convex portion guide that fits into the groove of the slider is formed on the side surface of the substrate holder. When the slider is moved in the linear direction, the vertical component force and the horizontal force act on the convex guide of the substrate holder from the slanted groove of the slider. Here, by making the substrate holder movable in the vertical direction at a fixed position by the guide, the substrate holder moves only in the vertical direction.

When performing epitaxial growth using this equipment, if the substrate holder is held upward until the first contact between the melt for growth and the substrate, the substrate holder will be open to atmospheric gas and the substrate will become hot. When the substrate is a compound containing an easily evaporative element such as As or P, as it is exposed to the atmospheric gas flow of As, Pd or As is released from the substrate surface, and the epitaxial layer becomes heterogeneous. The electrical characteristics may change. In this case, a container for accommodating the substrate holder is installed in the apparatus, and the substrate holder is accommodated in the storage container for the time until the substrate first contacts with the growth melt. You can prevent the omission. At this time, by putting As or P element or As compound or P compound in the storage container, the As pressure or P pressure in the storage container is increased and the effect is further enhanced.

The effect can be achieved by preparing a container similar to the melt reservoir as the storage container and housing the substrate holder to shut off the atmosphere gas flow.

An embodiment of the liquid phase epitaxial growth apparatus of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a perspective view of one embodiment of the liquid phase epitaxial growth apparatus of the present invention, and FIG. 2 is a schematic sectional view taken along the line AA ′ in the state where the substrate holder 1 is moved downward in FIG. Further, FIG. 3 is a side view showing an operating state of the growth apparatus.

As shown in FIG. 2, the substrate 14 is held vertically or obliquely by the substrate holder 2 of the substrate holder 1 so that the melt does not remain on the substrate surface. The substrate holder 1 is incorporated in the central space portion 4 of the support body 3, and is provided with a guide groove provided in the support body 3.
It is possible to move only in the up-down direction with respect to the support body 3 by 3a. A slider 5 is incorporated outside the support body 3 in contact with the side surface of the substrate holder 1.
It is slidable horizontally along the. An oblique groove 6 is formed on the slider 5 on the substrate holder side.
Further, the groove 6 of the slider is formed on the outer side surface of the substrate holder 1.
A convex portion guide 7 that meshes with the groove 6 at the same angle as is formed.

When the slider 5 is moved in the horizontal direction, the convex portion guide 7 of the substrate holder 1 moves in the groove of the slider, so that the substrate holder 1 moves in the vertical direction (FIGS. 3A and 3B). .

A growth melt reservoir 8 is installed inside the support 3, and the uppermost part of the melt reservoir 8 is lower than the lowermost part of the substrate holding part 2 when the substrate holder 1 is moved to the uppermost part. There is. The melt reservoir 8 can be moved linearly inside the support 3.

In this example, the case where the growth melt reservoir is three tanks is illustrated, but
The number of melt pools is increased or decreased according to the type of epitaxial layer to be grown.

It is desirable that each part of these devices is made of high-purity graphite.

Next, an example of a liquid phase epitaxial growth method using this apparatus is shown.

The substrate 14 is set on the substrate holding part 2 of the substrate holder 1, while the raw materials necessary for growing a desired epitaxial layer are put in the growth melt reservoirs 8, 8 '. As shown in FIG. 3 (a), the substrate holder 1 is moved to the upper part and set in a quartz reaction tube (not shown) of a horizontal epitaxial furnace. After replacing the atmosphere in the reaction tube,
Melt for growth by raising the temperature to a prescribed temperature and melting the raw materials
Prepare twelve. The temperature in the furnace is set to the growth start temperature of the first epitaxial layer, and after the growth melt becomes uniform, the slider 5 is slid to lower the substrate holder 1 to bring the substrate 14 and the first growth melt 12 into contact with each other. Let (the third
Figure (b)). After that, the temperature in the furnace is cooled to a predetermined temperature at a predetermined rate to grow the first epitaxial layer on the surface of the substrate. After the growth of the first epitaxial layer is completed, the slider 5 is slid to move the substrate holder 1 upward to separate the substrate 14 from the first growth melt 12 (third embodiment).
The state of FIG. Next, the melt pool for growth 8, 8 '...
Is slid to move the second growth melt 12 'to below the substrate holder 1. After the temperature inside the furnace is set to the growth start temperature of the second epitaxial layer, the slider 5 is slid to lower the substrate holder 1 and bring the substrate 14 and the second growth melt 12 'into contact with each other (Fig. 3 (c)). ). After cooling to a predetermined temperature to grow the second epitaxial layer, the slider 5 is slid to raise the substrate holder 1 to separate the substrate 14 from the growth melt 12 '. Similarly, the movement of the growth melt reservoir, the contact between the substrate and the melt, and the separation are repeated in the same manner to sequentially grow the required number of epitaxial layers.

Example 1 A GaAlAs single hetero red LED epitaxial wafer was prepared using the liquid phase epitaxial growth apparatus shown in FIG. P-type GaAs substrate (2 in φ) is 2 at 5 mm intervals
A total of 60 sheets were set in the substrate holder 1 facing each other. The first melt pool is for the first growth melt
2400 g of Ga metal, 170 g of GaAs polycrystal, 4.5 g of Al and 5.0 g of Zn were charged. The second melt pool was charged with 2400 g of Ga metal, 60 g of GaAs polycrystal, 16 g of Al, and 70 mg of Te for the second growth melt. First, the substrate holder 1 is placed above, and the first melt reservoir 8 is set so as to be located below the substrate holder 1. Insert the equipment into the quartz reaction tube of the horizontal epitaxial furnace, replace the inside of the furnace with H ₂ gas, and then flow H ₂ gas.
Raise the temperature to 880 ℃. Hold at 880 ° C for 120 minutes to completely melt and homogenize the metal, then contact the GaAs substrate with the first growth melt and cool to 850 ° C at a cooling rate of 0.3 ° C / min. 14 was separated from the first growth melt 12. Then, the growth melt reservoir 8'is moved below the substrate holder 1 while keeping the temperature at 850 ° C, the GaAs substrate 14 is brought into contact with the second growth melt 12 ', and cooled to 750 ° C at a cooling rate of 0.5 ° C / min. Then separated from the second growth melt 12 '. After that, the temperature was allowed to cool to room temperature, the GaAs substrate 14 was taken out of the furnace, and ohmic electrodes were formed on the front and back surfaces of the epitaxial growth layer to form a 0.3 mm square LED element.

[Comparative Example 1] For comparison, the same GaAlAs was manufactured using a mass production slide boat having the same structure as the conventional horizontal slide boat shown in FIG.
Single heteroepitaxial growth was performed. In the horizontal epitaxial furnace used in the apparatus of Example 1, a slide board has one substrate with two substrates and five substrates, a total of ten 2 in φP type G.
I was able to set the aAs substrate at once. For each substrate as a growth melt, 50 g of Ga metal, 3.54 g of GaAs polycrystal, Al 93.8 mg, Zn 104 mg for the first growth melt, and 50 g of Ga metal for the second growth melt, 1.25 g of GaAs polycrystal.
g, Al 333 mg, and Te 1.46 mg were set. After inserting the slide boat with the substrate and the growth melt into the quartz reaction tube of the horizontal epitaxial furnace, and after replacing the inside of the furnace with H ₂ gas
The temperature was raised to 880 ° C. while flowing H ₂ gas. After holding at 880 ° C. for 120 minutes, the melt reservoir was slid to bring the GaAs substrate into contact with the first growth melt. After cooling to 850 ° C. at a cooling rate of 0.3 ° C./min, the melt reservoir was slid again to separate the GaAs substrate from the first growth melt. Next, the melt pool is further slid at a temperature of 850 ° C., the GaAs substrate is brought into contact with the second growth melt, cooled to 750 ° C. at a cooling rate of 0.5 ° C./minute, and then separated from the second growth melt. did. After that, the temperature was allowed to cool to room temperature, the furnace was taken out from the GaAs substrate, ohmic electrodes were formed on the front and back surfaces of the epitaxial growth layer, and a 0.3 mm square LED element was prepared.

The volatility and the wavelength distribution of the LED elements prepared in Example 1 and Comparative Example 1 are shown in FIGS. 5 and 6.

As is clear from FIG. 5 and FIG. 6, the variation in the distribution of Example 1 is much smaller than that of Comparative Example 1 in both luminance and wavelength.

Further, in comparison with the defect rate of visual inspection due to scratches, residual metal marks, and the like in Comparative Example 1, about 8% of the defects occur, but
In Example 1, the defects were remarkably reduced to about 2%.

[Embodiment 2] A GaAs infrared LE was manufactured by using the same apparatus shown in FIG.
A D epitaxial wafer was created. n-type GaAs substrate (2
inφ) were set in a substrate holder so that two sheets of them were opposed to each other at 5 mm intervals. 2400 g of Ga metal, 384 g of GaAs polycrystal, Si4.8 for the first growth melt in the first growth melt reservoir
g, G for the second growth melt in the second growth melt reservoir
a Metal 2400g, GaAs polycrystal 240g, and Si 3.6g were put.

An empty metal reservoir that is movable adjacent to the growth melt reservoir and is movable together with the growth melt reservoir is installed as a substrate holder storage container, and the substrate holder is stored until just before contacting the first growth melt with the substrate. After the contact between the substrate and the first growth melt, the epitaxial growth was performed under the following conditions.

Insert the device into the quartz reaction tube of the horizontal epitaxial furnace,
After replacing the inside of the furnace with H ₂ gas, while flowing H ₂ gas,
The temperature was raised to ° C. After holding at 930 ° C for 60 minutes, contact the GaAs substrate with the first growth melt and cool it at a cooling rate of 0.8 ° C / minute for 9 minutes.
After cooling to 00 ° C., the GaAs substrate was separated from the first growth melt. Next, after lowering the furnace temperature to 870 ° C, the substrate is
Contact with the growth melt of 700 ℃ at a cooling rate of 1.2 ℃ / min
And the substrate was separated from the second growth melt.
Then, it was cooled to room temperature and the GaAs substrate was taken out of the furnace.

In addition, GaAs polycrystal was placed in the bottom of the substrate holder storage container in such an amount that it did not come into contact with the substrate, and epitaxial growth was performed by the same method as above.

As a result, the number of pits, which is thought to be caused by As loss on the surface of the epitaxial layer, was greatly reduced compared to the case where the containment vessel was not used. Further, when the substrate holder was stored with the GaAs polycrystal in the storage container and the same epitaxial growth was performed, no pits were generated.

Ohmic electrodes are formed on the front and back surfaces of each of the above three types of epitaxial wafers.
A 0.3 mm square LED element was created.

[Comparative Example 2] The same slide boat apparatus as in Comparative Example 1 was used to obtain GaAs infrared LE.
A D epitaxial wafer was created. N in the substrate housing
A type GaAs substrate is set, and Ga metal 50 g, GaAs polycrystal 8 g, Si 100 mg for the first growth melt, and Ga metal 50 g, GaAs polycrystal 5 g, Si 75 mg for the second growth melt are set. Insert the device into a quartz reaction tube of the lateral epitaxial furnace, after the furnace was replaced with H ₂ gas, while flowing H ₂ gas, the temperature was raised to 930 ° C.. After holding at 930 ° C. for 60 minutes, the melt reservoir was slid to bring the GaAs substrate into contact with the first growth melt. After cooling to 900 ° C. at a cooling rate of 0.8 ° C./min, the melt reservoir was slid again to separate the GaAs substrate from the first growth melt. Next, after lowering the temperature in the furnace to 870 ° C, slide the melt reservoir further to bring the GaAs substrate into contact with the second growth melt, cool it to 700 ° C at a cooling rate of 1.2 ° C / min, and then perform the second growth. Separated from the work melt. After that, the temperature was allowed to cool to room temperature, the GaAs substrate was taken out of the furnace, and ohmic electrodes were formed on the front surface and the back surface of the epitaxial growth layer, to prepare a 0.3 mm square LED element.

100% inspection was carried out for each LED element of Example 2 and Comparative Example 2.

The main results are summarized in Table 1.

[Effects of the Invention] As described above, by performing epitaxial growth by the liquid phase epitaxial growth method of the present invention using the liquid phase epitaxial growth apparatus of the present invention, it is possible to obtain a multilayer having excellent uniformity of characteristics and a good epitaxial surface than ever before. Epitaxial wafers can be obtained and mass productivity is greatly improved. In addition, if the evaporation of elements such as As and P from the substrate due to epitaxial conditions occurs, a container for the substrate holder is installed and the substrate is stored in the container until the substrate and the growth melt contact each other. By doing so, it is possible to reduce the loss of easily evaporative elements. At this time, the effect is further enhanced by putting a compound containing an easily evaporating element into the storage container.

[Brief description of drawings]

FIG. 1 is a perspective view of an embodiment of the liquid phase epitaxial growth apparatus of the present invention, and FIG. 2 is a schematic sectional view taken along the line AA ′ in the state where the substrate holder of the apparatus of FIG. 1 is moved downward, FIG. Is a side view showing an operating state of one embodiment of the liquid phase epitaxial growth apparatus of the present invention, FIG. 4 is a sectional view of a conventional liquid phase epitaxial growth apparatus, FIG. 5 is a luminance distribution diagram of an LED element, and FIG. FIG. 6 is a distribution chart of emission peak wavelengths of the same LED element as in FIG. 5. 1 ... Substrate holder 2 ... Substrate holder 3 ... Support 4 ... Support center space 5 ... Slider 6 ... Slider groove 7 ... Convex guide 8 ... Growth melt pool 9 ... Bottom plate 10 …… Melt slider 11 …… Melt storage part 12 …… Growth melt 13 …… Substrate storage recess 14 …… Substrate

Claims (1)

[Claims] 1. A horizontally long box-shaped support, a plurality of continuous melt reservoirs that can move in the support in the longitudinal direction, a substrate holder that can move vertically at a fixed position in the support, It contacts the outside of the side surface of the support and the outside of the side surface of the substrate holder,
The slider is slidable in the longitudinal direction along the side surface of the support, and an oblique groove is formed on the sliding surface of the slider, and the side surface of the substrate holder is fitted in the groove of the slider. The liquid phase epitaxial growth apparatus is characterized in that the substrate holder is configured to move up and down to a position in the melt reservoir by forming a convex guide which moves and moving the slider in a linear direction.