JPH0380185A - Method and device for liquid epitaxial growth - Google Patents

Abstract

PURPOSE:To obtain multilayered epitaxial wafers having excellent uniformity of characteristics with good mass productivity by combining the contact and sepn. of a substrate and a melt for growth by the vertical movement of a substrate holder and the linear movement of melt reservoirs, thereby forming plural epitaxial layers on the substrate. CONSTITUTION:While the substrate 14 is set in a substrate holding part 2 of the substrate holder 1, necessary raw materials are put into the melt reservoirs 8, 8',... for growth. The holder 1 is moved to an upper part and is set in this state into a quartz reaction tube of a horizontal furnace. After the inside of the reaction tube is substd. with a gaseous atmosphere, the temp. is increased up to a prescribed temp. to melt the raw materials and to prepare the melt 12 for growth. The temp. in the furnace is set at the growth start temp. of the 1st epitaxial layer and after the melt 12 levels off, a slider 5 is slid to lower the substrate 14 together with the holder 1 and to bring the substrate 14 and the melt 12 into contact with each other. The inside of the furnace is thereafter cooled down to a prescribed temp. at a prescribed rate to grow the 1st epitaxial layer on the substrate surface. The same operation as the above-mentioned operation is thereafter repeated to laminate and grow the epitaxial layers of the 2nd, 3rd....

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a multilayer liquid phase epitaxial growth method and a growth apparatus used therefor, and in particular has good in-plane uniformity of properties.
This is suitable for obtaining an epitaxial wafer with a good epitaxial layer surface condition.

[Prior art] Epitaxially grown layers of m-V compound semiconductors are used in optical devices such as light emitting diodes and laser diodes,
It is widely applied to high-speed devices such as ET. More recently, Device 1! In order to improve performance, a fine structure in which semiconductor thin films of several to several tens of angstroms are stacked is required. Such thin film stack structures are produced by vapor phase or liquid phase epitaxial growth methods.

In order to liquid phase grow a plurality of epitaxial layers on a compound semiconductor substrate, a slide boat as shown in FIG. 4 is generally used. For example, when growing three epitaxial layers, the substrate 14 is placed in the substrate storage recess 13 of the bottom plate 9, and the melt slider 10, which is slidable relative to the bottom plate 9, is placed on top of the substrate 14. melt slider 10
Growth melts 12, 12° and 12'' having the composition necessary to grow the intended epitaxial layer are respectively accommodated in the melt storage portions 11.11' and 11°.In this state, the slide port is opened. 1 to 1 are inserted into an epitaxial growth furnace (not shown) and heated to a predetermined temperature in an atmosphere gas such as 11□ gas or inert gas.After the growth melt becomes uniform, move the melt slider 10 in the direction of the arrow. the substrate 14 and the first growth melt 1.
Contact with 2. In this state, the temperature inside the furnace is gradually cooled and a first epitaxial layer is grown on the substrate 14.

After a predetermined amount of epitaxial layer has grown, the melt slider 10 is further slid in the direction of the arrow to separate the substrate 14 and the melt 12. Next, it is brought into contact with the melt at 12° and slowly cooled again to grow a second epitaxial layer. After the third epitaxial layer growth is completed in the same manner,
The substrate 14 and the melt 12° are separated and allowed to cool.

[Problem to be Solved by the Invention 1] In the above method, the depth of the substrate storage recess 13 on the bottom plate 9 is set to be smaller than the thickness of the wafer after epitaxial layer growth in order to allow the bottom plate 9 and the nols 1 to 1 to sliders 10 to slide. Also make it deeper. For this reason, when separating the growth melt 12 onto the substrate 14, a gap is created between the substrate 14 and the bottom of the melt slider 1O, and the growth melt 12 cannot be completely separated, and a portion of it remains on the substrate 14. remain. When the substrate is brought into contact with the next melt, the melt 12 remaining on this substrate 14 is brought into the next melt, so the composition of the melt changes, making it impossible to obtain an epitaxial layer with the desired composition, and causing the wafer surface to deteriorate. The disadvantage is that the composition of the epitaxially grown layer varies widely within the layer. Another disadvantage is that when the substrate and the melt are separated after the growth of the final epitaxial layer, if some of the melt remains on the substrate 14, traces of the melt will be left on the epitaxial layer surface, making it impossible to obtain a good epitaxial layer surface. There is also.

Further, when sliding the sliders 1 to 10, scratches may occur on the substrate surface due to friction with polycrystalline products deposited in the melt 12 or around the substrate 14. Regarding mass productivity, for example, when growing three layers, three growth melts are required for one substrate, which is poor in mass productivity.

As a means for obtaining an epitaxially grown layer with a good surface condition, there is a vertical (dip method) liquid phase growth method. In the vertical method, a substrate is immersed in a melt placed in a melt reservoir for epitaxial growth, and after the growth is completed, the substrate is pulled up to prevent the growth melt from remaining on the surface of the substrate. The present applicant has also previously proposed an apparatus for multilayer epitaxial growth (see Japanese Patent Application Laid-Open No. 62-83398). This device has a plurality of solution tanks arranged on the circumference and is rotatable, and by sequentially transferring the substrate holder holding the substrate from the first growth solution tank, multiple epitaxial layers can be continuously grown. It is something that grows.

In this method, when increasing the number of epitaxial layers, it is necessary to increase the inner diameter of the reaction tube in the growth furnace that houses the solution bath, and when increasing the number of substrates processed at one time, the diameter of the reaction tube must be increased. Must. The reaction tube is usually made of high-purity quartz, but the diameter is 40cm for both strength and economy.
The diameter of the reaction tube is approximately 1.5 m, and it is not practical to use a reaction tube with a diameter larger than this. In other words, even if an attempt is made to mass produce by increasing the number of sheets processed at one time, there are restrictions on the equipment.

On the other hand, in the method of the present invention, there is no need to enlarge the diameter of the reaction tube, and by increasing the length while keeping the conventional diameter, it is possible to increase the size and number of solution tanks, which improves mass production. is also an excellent method.

[Means for Solving the Problems 1] The Ministry of the Invention has conducted research to solve the above-mentioned drawbacks, conceived of a liquid phase epitaxial growth device with a new structure, and found that the above-mentioned drawbacks can be solved by an epitaxial growth method using this device. I found it. In the growth method according to the present invention, a substrate holder that holds a substrate vertically or diagonally is moved vertically at a fixed position, so that a growth melt I~
The melt is immersed in the melt and the substrate is brought into contact and separated. Further, the growth melt is moved by sequentially moving the melt reservoir by sliding the melt reservoir in a linear direction relative to the substrate holder while the substrate holder is moved upward. A plurality of epitaxial layers are grown on the substrate by combining the contact separation between the substrate and the growth melt by moving the substrate holder in the vertical direction and the linear movement of the melt reservoir. According to this method, the substrate and the growth melt are separated by pulling the substrate upward from the growth melts 1 to 1, so that the growth melt falls due to gravity and hardly remains on the substrate. Therefore, the melt will not be carried over to 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 part of the substrate holder does not slide against other parts of the apparatus, no scratches will occur on the wafer surface. In addition, since epitaxial growth can be performed on multiple substrates using one set (three in the case of three-layer epitaxial) of melt reservoirs, mass productivity is greatly improved compared to the conventional slide boat method. By enlarging the melt reservoir in the longitudinal direction, it is possible to increase the number of substrates that can be processed without enlarging the diameter of the reaction tube.

The apparatus used in this method has a plurality of melt reservoirs for growth that are movable in a linear direction, a substrate holder that is movable in a vertical direction, and a slider that is in contact with the side surface of the substrate holder and that is movable in a linear direction. A diagonal groove is formed, and a convex 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 a straight line, a vertical component of force and a horizontal force are applied to the convex guide of the substrate holder from the diagonal groove of the slider. Here, by making the substrate holder movable in the vertical direction at a fixed position using a guide, the substrate holder moves only in the vertical direction.

When performing epitaxial growth using this device, if the substrate holder is held up and down until the first contact between the growth melt and the substrate, the substrate holder will be open to atmospheric gas and the substrate will be at a high temperature. If the substrate is a compound containing easily evaporable elements such as As or P, As or P may be removed from the substrate surface, and the epitaxial layer may become non-uniform. Electrical characteristics may change. In this case, a container for storing the substrate holder is installed in the device, and by storing the substrate holder in the storage container until the substrate comes into contact with the first growth melt, it is possible to eliminate so-called As or P from the substrate surface. You can prevent it from falling out. At this time, by placing As or P element, 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 increased.

This effect can be achieved by preparing a containment vessel similar to the melt reservoir, housing the substrate holder, and shutting it off from the flow of atmospheric gas.

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 an embodiment of the liquid phase epitaxial growth apparatus of the present invention, and FIG. 2 is a schematic cross-sectional view along the AA' direction in a state in which the substrate holder I is moved downward in FIG. Further, FIG. 3 is a side view showing the operating state of the growth device.

As shown in FIG. 2, the substrate 14 is held vertically or diagonally by the substrate holding portion 2 of the substrate holder 1 so that no melt remains on the surface of the substrate. The substrate holder 1 is incorporated into the central space 4 of the support 3, and is movable only in the vertical direction relative to the support 3 by means of a guide groove 3a provided in the support 3. A slider 5 is installed on the outside of the support 3 in contact with the side surface of the substrate holder 1, and the slider 5 is horizontally slidable along the support 3.

A diagonal groove 6 is formed on the substrate holder side of the slider 5. Furthermore, a convex guide 7 is formed on the outer side surface of the substrate holder 1 and engages with the groove 6 of the slider at the same angle.

When the slider 5 is moved horizontally, the convex guide 7 of the substrate holder 1 moves within the groove of the slider, causing the substrate holder 1 to move vertically (see Fig. 3).
a), (b)).

A growth melt reservoir 8 is installed inside the support body 3, and the lowest part of the melt reservoir 8 is lower than the lowest part of the substrate holding part 2 when the substrate holder 11 is moved to the lowest part. is also lower. The melt reservoir 8 can be moved inside the support 3 in a linear direction.

This side shows the case where there are 3 tanks of melt liquid for growth.
The number of nulls 1 to 1 is increased or decreased depending on the type of epitaxial layer to be grown.

It is preferable that each part of these devices be made of high-purity quartz.

Next, an example of a liquid phase epitaxial growth method using this apparatus will be described.

Set the substrate 14 on the substrate holding part 2 of the substrate holder 1,
On the other hand, raw materials necessary for growing a desired epitaxial layer are put into the growth melt reservoir 8.8°. As shown in FIG. 3(a), the substrate holder 1 is moved upward and set inside a quartz reaction tube (not shown) of a horizontal epitaxial furnace. After replacing the inside of the reaction tube with atmospheric gas, the temperature is raised to a predetermined temperature to dissolve the raw materials and prepare the melt 12 for growth. The temperature inside the furnace is set as the growth start temperature of the first epitaxial layer, and after the growth melt I becomes uniform 2, the slider 5 is slid to lower the substrate holder 1, and the substrate 14 and the first growth melt are 1
2 into contact (Fig. 3(b)).

Thereafter, the temperature inside the furnace is cooled down to a predetermined temperature at a predetermined rate, and a first epitaxial layer is grown on the substrate surface. After the growth of the first epitaxial layer is completed, the slider 5 is slid to move the substrate holder 2 to 100 degrees, and the substrate 14 and the first growth melt 12 are separated (see Fig. 3).
a) condition). Next, the melt reservoir for growth 8.8',...-
... to move the second growth melt l-12' under the substrate holder l. After the temperature in the furnace reaches the growth starting temperature of the second epitaxial layer, the slider 5 is slid to lower the substrate holder 1, and the substrate 14 and the second growth melt] 2 are brought into contact (see Fig. 3 (C). ))
. After cooling to a predetermined temperature and growing the second epitaxial layer, the slider 5 is slid to remove the substrate holder 1.
1 to separate the substrate 14 and the growth melt I2°. Thereafter, in the same manner, the movement of the growth melt reservoir, the contact and separation of the substrate and the melt are repeated once, and the required number of epitaxial layers are successively grown.

[Example 1] Using the liquid phase epitaxial growth apparatus shown in FIG. 1, a GaAlAs single hetero red LED epitaxial wafer was produced. P-type GaAs substrate (2inφ)
is 2 pieces at 5mm intervals + rr + stitching for a total of 60
The sheet was set on substrate holder 1. The first melt reservoir contains 2400 g of Ga metal for the first growth melt.
GaAs polycrystal 170g, A14.5g, Zn
5. Og was charged. The second melt reservoir was charged with 2400 g of Ga metal, 60 g of GaAs polycrystal, 16 g of Al, and 70 g of Te for the second growth melt. First, the substrate holder 1 is placed upward, and the first melt reservoir 8
is positioned below the substrate holder 1. The device was inserted into the quartz reaction tube of a horizontal epitaxial furnace, and after replacing the inside of the furnace with 11□ gas, it was heated to 88°C while flowing H2 gas.
Raise the temperature to 0°C. After holding at 880°C for 120 minutes and the metal completely melting to a uniform temperature, the GaAs substrate was brought into contact with the first growth melt and cooled to 850°C at a cooling rate of 403°C/min. , the GaAs substrate 14 was separated from the first growth melt 8 . Then temperature 8
The growth melt reservoir 8' was moved under the substrate boulder 1 while maintaining the temperature at 50°C, and the G d A s % plate 14 was brought into contact with the second growth melt 12' at a cooling rate of 5°C/min. 75 at
1 minute from the growth melt 12' in the rear tube 2 cooled to 0°C.
iiiE I did. After that, I ordered 1 attack to the item (Muro), and G +
The IAs substrate 14 is taken out of the furnace, and ohmic electrodes are formed on the front and back surfaces of the epitaxial growth layer.
．． A 3 mm square I-ED element was created.

[Comparative Example 1] For comparison, a slide boat for mass production having a structure similar to that of the conventional horizontal slide photocoat shown in FIG.
As single heteroepitaxial growth was performed. In the horizontal epitaxial furnace used in the apparatus of Example 1, in slide board 1~, 5 stages with 2 substrates per stage, a total of 10 2
Inφ type P type GaAs substrates could be set at once. For each substrate as the growth melt 1-, 50 g of Ga metal for the first growth melt, 3.54 g of GaAs polycrystal, 193.8 mg of A, 104 mg of 5 Zn, and 50 g of Ga metal for the second growth melt. , GaAs polycrystalline product], 25g, AI-33
3 mg and Te 1.46 mg were set. The slide port with the substrate and growth melt set was inserted into a quartz reaction tube of a horizontal epitaxial furnace, and after replacing the inside of the furnace with H2 gas, the temperature was raised to 880° C. while flowing 11□ 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 03° C./min, the melt reservoir was slid again to separate the GaAs substrate from the first growth melt. Next, the melt reservoir is further slid while the temperature remains at 850°C, the GaAs substrate is brought into contact with the second growth melt, and the GaAs substrate is cooled to 750°C at a cooling rate of 0.5°C/min. Separated from.

Thereafter, it was allowed to cool to room temperature, the GaAs substrate was taken out of the furnace, and ohmic electrodes were formed on the front and back surfaces of the epitaxial growth layer, respectively, to produce a 0.3 mm square LED element.

The luminance and wavelength distributions of the LED elements produced in Example 1 and Comparative Example 1 are shown in FIGS. 5 and 6.

6 As is clear from FIGS. 5 and 6, the distribution variations in both luminance and wavelength are much smaller in Example I than in Comparative Example 1.

In addition, regarding the appearance inspection defect rate due to scratches, metal residue, etc., about 8% of defects occurred in Comparative Example 1, whereas
In Example 1, the number of defects was significantly reduced to about 2%.

[Example 2] Using the same apparatus shown in FIG. 1 as in Example 1, a GaAs infrared LED epitaxial wafer was produced. n-type Ga
Two As substrates (2 in φ) were set facing each other on a substrate holder with an interval of 5 mm. 2400 g of Ga metal for the first growth melt in the first growth melt reservoir
, 384 g of GaAs polycrystal, 4.8 g of Si, 2400 g of Ga metal for the second growth melt in the second growth melt reservoir, 240 g of GaAs polycrystal, Sj
3.6g was added.

An empty metal reservoir that can be moved from growth null 1 to the reservoir is installed adjacent to the growth melt reservoir as a substrate holder storage container, and the substrate holder is held until just before contacting the first growth melt with the substrate. Store it in the substrate holder storage container,
After contact between the substrate and the first growth melt, epitaxial growth was performed under the following conditions.

Insert the device into the quartz reaction tube of a horizontal epitaxial furnace,
After replacing the inside of the furnace with H2 gas, while flowing H2 gas,
The temperature was raised to 30°C. After holding at 930℃ for 60 minutes, G
The aAs substrate and the first growth melt are brought into contact and cooled to 900°C at a cooling rate of 0.8°C/min.
isolated from the growth melt. Next, increase the temperature inside the furnace to 870℃
After cooling the substrate to a temperature of
The substrate was cooled to 700° C. at a cooling rate of 1.2° C./min and separated from the second growth melt. Thereafter, it was allowed to cool to room temperature, and the GaAs substrate was taken out from the furnace.

Further, an amount of GaAs polycrystal was placed in the inner bottom of the substrate holder storage container in an amount that did not contact the substrate, and epitaxial growth was performed in the same manner as described in -.

As a result, the number of pits thought to be caused by As missing on the surface of the epitaxial layer was significantly reduced compared to when no containment vessel was used. Furthermore, GaA in the containment vessel
When epitaxial growth was performed in the same manner with the Jl (plate holder) stored in the state where the s-polycrystal was inserted, no bits were generated.

Omitsu electrodes were formed on the epitaxial surface and back surface of each of the three types of epitaxial wafers mentioned above.
．． A 3 mm square LED element was created.

[Comparative Example 2] Using the same slide board 1 to device as Comparative Example 1, GaAs
An infrared LED epitaxial wafer was created. An n-type GaAs substrate was set in the substrate storage part, and 50 g of Ga metal, 8 g of GaAs polycrystal, and 100 mg of Si were added for the first growth melt, and 50 g of Ga metal, 5 g of GaAs polycrystal, and 5175 for the second growth melt.
Set g. The apparatus is inserted into a quartz reaction tube of a horizontal epitaxial furnace, and after replacing the inside of the furnace with H2 gas, the temperature is raised to 930° C. while flowing H2 gas. 60 at 930℃
After holding it for a few 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 1. Next, after the temperature in the furnace was lowered to 870°C, the melt reservoir was further slid to bring the GaAs substrate into contact with the second growth melt, and the second growth melt was cooled to 700°C at a cooling rate of 1.2°C/min. isolated from the growth melt. Thereafter, it was allowed to cool to room temperature, the GaAs substrate was taken out of the furnace, and ohmic electrodes were formed on the front and back surfaces of the epitaxial growth layer, respectively, to produce a 0.3 mm square LED element.

A 100% inspection was conducted for each of the LED elements of Example 2 and Comparative Example 2.

The main results are summarized in Table 1.

(Leaving space below) Table [Effects of the Invention] As described above, by performing epitaxial growth using the liquid phase epitaxial growth apparatus of the present invention and the liquid phase epitaxial growth method of the present invention, the uniformity of characteristics is superior to that of the conventional method. A multilayer epitaxial wafer with a good epitaxial surface can be obtained, and mass productivity can be greatly improved. In addition, if epitaxial conditions cause the loss of easily evaporable I elements such as As and P from the substrate, a substrate holder storage container is installed and the substrate is kept in the storage container until the substrate comes into contact with the growth melt. By storing it, it is possible to reduce the loss of easily evaporable elements. At this time, the effect is further enhanced by placing a compound containing an easily evaporable element in the containment vessel.

[Brief explanation 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 cross-sectional view of the apparatus shown in FIG.
4 is a sectional view of a conventional liquid phase epitaxial growth device, FIG. 5 is a luminance distribution diagram of an LED element, and FIG. FIG. 6 is a distribution diagram of the emission peak wavelength of the same LED element as FIG. 5. 1...Substrate holder 2...Substrate holding section 3...Support body 4...-Support central space 2 5...Slider 6. ---Slider groove 7 --- Convex guide 8 --- Melt reservoir for growth 9 --- Bottom plate O --- Melt slider ---・Melt storage part 2...Melt for growth 3...One substrate storage recess 4...Substrate

Claims (4)

[Claims] (1) In a multilayer liquid phase epitaxial growth method using a horizontal epitaxial growth furnace, a substrate holder holding a substrate vertically or diagonally is moved up and down in a fixed position, and multiple melt reservoirs are moved linearly along the longitudinal direction of the furnace. A liquid phase epitaxial growth method characterized by moving the substrate and sequentially immersing the substrate in a plurality of growth melts to cause continuous epitaxial growth. (2) A first method characterized in that a substrate holder storage container is disposed adjacent to the melt reservoir, the substrate holder is stored in the storage container before the start of epitaxial growth, and the epitaxial growth is started after the substrate is held at a high temperature. The liquid phase epitaxial growth method described in . (3) The liquid phase epitaxial growth method according to item 2, wherein easily evaporable elements or compounds thereof among the elements constituting the substrate are allowed to coexist in the substrate holder storage container. (4) A horizontally elongated box-shaped support, a plurality of continuous melt reservoirs that are movable in the longitudinal direction within the support, a substrate holder that is movable in the vertical direction at a fixed position within the support, and the support and a slider that is in contact with the outer side surface of the substrate holder and the outer side surface of the substrate holder and is slidable in the longitudinal direction along the side surface of the support, and a diagonal groove is formed on the sliding surface of the slider, A convex guide that fits into the groove of the slider is formed on the side surface of the substrate holder, and by moving the slider in a linear direction, the substrate holder is moved up and down to a position within the metal reservoir. A liquid phase epitaxial growth device featuring: