JPH07516B2 - Liquid phase epitaxial growth method and apparatus therefor - Google Patents

Description

TECHNICAL FIELD The present invention relates to a liquid phase epitaxial growth method. More specifically, it relates to a liquid phase epitaxial growth method capable of continuously growing two or more epitaxial layers with good mass productivity, and an apparatus for carrying out the method.

2. Description of the Related Art Generally, a semiconductor single crystal is used when manufacturing a semiconductor element or device. This method for producing a semiconductor single crystal is roughly classified into a vapor phase growth method and a liquid phase growth method, each of which has its own particular advantage and is used properly according to the purpose.
Recently, one of the basic techniques for producing semiconductor single crystals
As one of them, the epitaxial growth method has attracted attention and has been widely used.

One of the most important advantages of this epitaxial growth technique is that it is extremely easy to control the impurities, and the impurities are introduced during the epitaxial growth regardless of the impurities in the substrate, and various junctions are formed between the epitaxial layer and the substrate. Can be formed. Further, according to this growth method, a single crystal layer having the same plane orientation as that of the single crystal substrate can be formed on the single crystal substrate, and further, for example, the melt portion for growth contacted with the seed crystal is gradually crystallized. According to a growth method such as a sliding method, a single crystal layer can be sufficiently formed on an insulating substrate, an amorphous substrate, or the like.

In the process of manufacturing semiconductor devices and devices, it is often necessary to form multilayer thin films. For this multi-layered growth, vapor phase epitaxial growth methods such as CVD and PVD are rarely used because multiple devices are used.Liquid phase epitaxial growth methods are mainly used, especially low defect single crystal layers of compound semiconductors that are easy to separate at high temperatures. Is advantageous in forming
It is widely used for manufacturing devices and elements having a multilayer thin film structure such as light emitting diodes and semiconductor lasers.

As a conventional liquid phase epitaxial growth technique, for example, a rigid dip method is known. In this method, a solvent, a solute, and a dopant are charged into a crucible, the temperature is raised in a reaction tube, and then a substrate is put in this to cool the single crystal thin film. So with this method,
In order to grow two or more layers having different compositions of growth layers, different kinds of dopants, and different concentrations, it was necessary to once take out the crucible and the like from the reaction tube and re-feed the raw materials. Therefore, the substrate is exposed to air during the growth, which adversely affects surface oxidation.

The horizontal slide method is known as one of the useful techniques for solving this problem. In this method, two or more kinds of solutions are put in several solution tanks in advance and placed in a reaction tube, and the substrate holder is placed in this state. Is moved to bring the substrate into contact with different solutions one after another to grow crystals. However, this method requires the substrates to be laid out on a flat surface, thus taking up space and not being suitable for mass production.

Problems to be Solved by the Invention As described above, the liquid phase epitaxial growth method has various advantages such as extremely easy control of impurities and is advantageous also in multi-layer growth, and is widely used. ,
In particular, there are some problems to be improved when growing multiple layers. For example, when growing two or more epitaxial layers by the rigid dip method, which has excellent mass productivity,
After the growth of the first layer, the substrate had to be taken out once, and there was a drawback that an oxide film was formed on the surface of the first layer. On the other hand, according to the slide boat method, the drawbacks of the rigid dip method can be solved, but the number of materials that can be grown at one time is limited, and thus mass productivity is poor, which is not preferable.

Therefore, developing a new liquid phase epitaxial growth method that does not exhibit the drawbacks found in the rigid dip method suitable for mass production is to obtain high-quality multilayer thin film elements and devices, and to reduce the manufacturing cost. It is of great significance in expanding the fields of application of the liquid phase epitaxial growth method. An object of the present invention is to provide a liquid phase epitaxial growth method capable of continuously forming two or more epitaxial layers with good mass productivity. It is also one of the objects of the present invention to provide a liquid phase epitaxial device useful for carrying out such a method.

Means for Solving the Problems In view of the above-mentioned current state of the conventional liquid phase epitaxial growth method in multi-layer epitaxial growth of two or more layers, the present inventors have a problem of excellent mass productivity and surface oxidation during growth. As a result of various studies aimed at developing a new liquid phase epitaxial growth method, a large number of substrates were arrayed in the same cassette and the first layer was grown by immersing it in the first layer growth solution. The growth of the second and subsequent layers is carried out by introducing the solution in at least one liquid reservoir into a cassette or crucible containing the substrate, and repeatedly performing epitaxial growth without removing the cassette from the growth crucible. The present invention has been found to be extremely advantageous for achieving the above object, and has reached the present invention.

That is, the liquid crystal epitaxial growth method provided by the present invention uses a device equipped with a crucible supported in a furnace and a support member for supporting a substrate immersed in the growth solution contained in the crucible, and a predetermined method is used. A crucible having a cylindrical side wall and having an upper opening, and a side wall complementary to the inner surface of the side wall of the crucible, wherein the crucible has a cylindrical side wall. A cassette that has an outer surface shape and has a growth chamber inside and can move up and down in the crucible and can rotate horizontally at the same time, a substrate support member housed in the cassette, and an upper end of the cassette. A rod that is operated when moving or rotating the mounted cassette inside the crucible from the outside of the crucible, and further comprising the growth chamber formed on a side wall of the cassette. A through hole that communicates to the preparative aspect,
An apparatus having a groove formed on the outer surface of the side wall of the cassette or on the inner surface of the side wall of the crucible is used to operate the rod to vertically move or horizontally rotate the cassette so that the through hole and the groove communicated with each other. It is characterized in that it includes an operation of introducing or discharging a growth solution into the growth chamber through the growth chamber and continuously performing liquid phase epitaxial growth of the multilayer film without taking out the substrate from the growth chamber.

By the method of the present invention, it is possible to obtain a binary system epitaxial layer of various semiconductor materials, particularly III-V group or II-VI group compound semiconductors which are easily decomposed at high temperature or more.

According to the method of the present invention, among the multilayer epitaxial layers,
The first layer is implemented by a conventionally known dipping method. The principle is simply that molten metal, such as molten Ga
It is intended to deposit the raw material on the surface of the substrate such as the wafer by cooling the solution while the wafer or the like is immersed in the solution in which the raw material to be epitaxially grown is dissolved in the medium such as.

Further, the growth of the second and subsequent layers is also the same as the dipping method in principle, but the second layer can be formed without taking out, for example, a cassette as a support for a wafer or the like and exchanging a solution or a crucible. It is carried out by devising a means for introducing a growth solution capable of performing growth after the first layer and sequentially implementing this.

Such a liquid phase epitaxial growth method of the present invention is a crucible, a cassette having an outer diameter slightly smaller than the inner diameter of the crucible, the cassette including a support for storing a large number of substrates, and moving the cassette up and down, It can be carried out by using a liquid phase epitaxial growth apparatus having a rotatable shaft and at least one solution reservoir for solution storage.

In the above apparatus of the present invention, the cassette can be separated into at least two parts by a known suitable means such as a screw-in type, a slot-type fitting, etc., and a support and a substrate such as a wafer can be housed therein. It has become.

Further, at least one of the cassette and the crucible is provided with a communicating means for communicating the bottom of the crucible and the cassette and a solution introducing means for introducing the solution from the solution reservoir into at least one of these, and the shaft moves the cassette up and down. Alternatively, by rotating the solution, the solution under the crucible can be introduced into and discharged from the cassette, and the solution in the liquid reservoir can be introduced into the cassette and the crucible.

Further, the liquid reservoir for storing the growth solution after the second layer is
It is also possible to form the liquid reservoirs (chambers) separated from each other by a partition provided above the cassette, or to use the liquid reservoirs connected to the crucible by the pipe means communicating with the opening provided in the side wall of the crucible. It is possible. Separation and communication between these liquid reservoirs and the inside of the crucible or the inside of the cassette can be easily performed by the following method.

First, the cassette is rotated and / or moved up and down by the shaft so that a solution introducing means, for example, a groove or an opening provided on the cassette side wall or the inner wall of the crucible is aligned with an opening communicating with the liquid reservoir below the chamber side wall or the crucible wall. By communicating with each other, the solution can be introduced into the cassette or the crucible. Further, by moving the cassette to a position where they do not coincide with each other by rotating the shaft or the like, the cassette wall or the crucible wall serves as a stopper, and the separation between the liquid reservoir and the cassette or the crucible is guaranteed. Of course, these operations can be performed with a solenoid valve or the like, especially when the liquid reservoir is provided outside the crucible.

Further, an opening or a slit is provided on the lower side or bottom of the cassette, while a groove is provided under the inner wall of the crucible if necessary, and these are communicated with each other to lower the cassette during the growth of the first layer so that the solution is transferred to the cassette. Can be introduced into the cassette, and the growth solution of the previous layer can be excluded from the cassette, and then the growth solution of the next layer can be introduced into the cassette according to one of the embodiments described above to replace the growth solution. It can be carried out. Further, the solution can be replaced almost completely by providing a solution discharge port at the bottom of the crucible, connecting the solution discharge port to the discharge liquid reservoir, and opening and closing the solenoid valve at the connection part.

On the other hand, there is no particular need to provide a gas outlet or gas inlet, and since the crucible and the cassette are not completely in close contact with each other, the atmospheric gas flows in and out through a slight gap between them. Therefore, carbon, quartz, quartz coated with carbon, or a ceramic substance is used as the crucible and the cassette material, and a material having a small wettability with respect to the growth solution, that is, a material having a large contact angle is used to form the solution. This is preferable because it is easy to prevent discharge and leakage at the introduction port.

In the method and apparatus of the present invention, the amount of the solution is almost equal to or larger than the dead space in the cassette because it is necessary to immerse all the substrates contained in the cassette in the solution. It is desirable to do.

Hereinafter, the device of the present invention will be described in more detail with reference to the attached FIG. FIG. 1 is a schematic sectional view showing a preferred embodiment of the liquid phase epitaxial device of the present invention.
Particularly, an apparatus which is useful for growing two epitaxial layers and is advantageous for a mode in which the second layer growth solution is mixed with the first layer growth solution to grow the second layer. Is.

The apparatus shown in FIG. 1 includes a crucible 1, a cassette 2, a rod (shaft) 3 for vertically moving and rotating the cassette,
It is mainly composed of a liquid reservoir 4 for the second layer growing solution provided on the upper part of the cassette 2. A large number of substrates 5 for storing substrates are arranged in the cassette 2. The dish 5 preferably has a large number of holes such as a mesh shape, especially at the bottom thereof, in order to facilitate the intrusion and discharge of the solution into the cassette, for example, quartz, carbon or carbon-coated quartz or ceramic. It is made. Further, in order to make the contact with the substrate a point contact (the contact with the dish is reduced as much as possible to prevent the contamination of the substrate and the epitaxial layer), the protrusion may have a large number of relatively large curvatures at the tip. .

The tray 5, ie the substrate support, can be varied by the mode of said communication means between the cassette growth chamber and the crucible, for example not necessarily if longitudinal slots are provided on the side of the cassette. It does not have to have a large number of through holes. On the other hand, when the opening provided on the lower side or the bottom of the cassette is the means, it is essential that the support has a large number of through holes.

Further, on the lower side of the solution reservoir 4 provided above the cassette 2, there is provided an outflow port 7 for introducing the solution 6 for growing the second layer contained therein into the cassette. During the growth of one layer it is sealed by contact with the walls of the crucible 1.

Further, the inner wall of the crucible 1 is provided with one groove 8 in the vertical direction for introducing the solution from the liquid reservoir 4 into the cassette or the crucible. It is also possible to provide a slit on the side of the cassette so that the solution directly flows into the cassette.

Further, the rod 3 moves up and down and rotates the liquid reservoir 4, the dish 5, and the solution 6 together with the cassette 2. Further, slits and the like are provided in the vertical direction on the side wall of the cassette.
Therefore, when the cassette 2 is lowered by the rod 3, the first layer growth solution 9 stored in the bottom of the crucible enters the inside through the slit of the cassette side wall, and each of the dishes 5 arranged in the growth chamber 10 The substrate 11 therein is completely immersed in the growth solution. By cooling the system in this state (for example, according to the temperature program as shown in FIG. 3), the epitaxial growth of the first layer becomes possible. In addition, in order to introduce the second layer growth solution, the rod 3 is operated in the same manner as described above, and the outflow port 7
And the groove 8 are aligned with each other, and the rod is raised to easily perform this.

In the embodiment shown in FIG. 1 as well, it is of course possible to grow the third layer, the fourth layer, etc., and in that case, the second layer growth liquid reservoir 4 is used.
This can be achieved by providing growth liquid reservoirs such as the third and fourth layers above, and further increasing the height of the groove 8.

Furthermore, the growth solution for the first layer does not necessarily have to be stored in the crucible 1 in advance, but a liquid reservoir may be similarly provided and stored therein.

It is also possible to provide an opening in the side wall at or near the bottom of the crucible 1 and connect it to a liquid reservoir for discharge liquid via a conduit, so that the embodiment of FIG. 1 can be substitution type growth instead of growth by solution mixing. .

The apparatus shown in FIG. 1 is housed in a furnace or a reaction tube like a normal dip type liquid phase epitaxial apparatus, and its temperature is controlled by the operation of the furnace.

2 (a) and 2 (b) are schematic plan views (a) and vertical cross-sectional views (b) showing a preferred embodiment of the present invention different from FIG. According to this aspect, the growth solution can be almost completely replaced every time each layer is grown, and the same growth operation as in FIG. 1 can be naturally performed.

As shown in FIG. 2 (a), the apparatus shown in FIG. 2 has a crucible 1, a cassette 2, a rod 3, and openings 12 _{1 to} 12 ₃ provided on the outer side of the crucible 1 for opening the apparatus. It is composed mainly of with the interior liquid more growth solution which has passed through the reservoir ₄₁ to _3.

The growth chamber of the cassette 2 is the same as that shown in FIG. 1, and therefore the same reference numerals are given and the description thereof is omitted. In this embodiment, at least one opening or slit 13 is provided in the upper portion of the cassette 2, and the openings 12 ₁ through which the liquid reservoirs 4 ₁ to 4 _{3 on the} side wall of the crucible are communicated by the operation of the rod 3. 12 ₃
By making it coincide with the above, the growth solution for the second layer, the third layer, etc. can be successively introduced into the cassette growth chamber 10.

On the other hand, an opening 14 is provided on the side wall near the bottom of the cassette 2 and a groove 15 is provided on the inner wall near the bottom of the crucible 1 so that the solution in and out of the cassette can enter and exit. Further, there is an opening 16 at the bottom of the crucible 1, and a drainage reservoir (not shown) connected by a pipe provided with a valve means can be provided, which is useful when it is desired to completely replace the solution after the growth of each layer. Is.

According to yet another aspect, the outer surface of the cassette 2 is provided with at least one longitudinally extending groove and at least one longitudinal slit of similar length or bottom opening or slit. A similar multi-layer film growth operation can be carried out by utilizing it.

Further, by combining and using the liquid reservoir installation methods shown in FIGS. 1 and 2, it becomes possible to form a multilayer film composed of an extremely large number of layers by a compact apparatus. It should be understood that such an embodiment also falls within the scope of the present invention.

Operation As described above, according to the method and apparatus of the present invention, an epitaxial film having a multilayer structure can be obtained with high mass productivity and high quality.

First, in the present invention, after the formation of the first layer or any layer being grown, the growth of the second layer or the next layer can be continuously carried out without taking out the substrate. This is possible by using a liquid phase epitaxial growth apparatus having one of the configurations shown in FIG. 1 or 2.

Further, according to the present invention, a large number of products obtained with the same rod can be processed at the same time by a single operation, and a large amount of products of the same quality can be obtained.
This is also possible by using the device having the above configuration.

Briefly explaining the operation of forming an epitaxial growth film composed of two layers using the apparatus of FIG. 1, first, the first layer growth solution 9 is placed in the growth chamber of the cassette 2 in the crucible 1 supported in the furnace. A large amount of the substrates 11 accommodated in the dish 5 are accommodated in the growth chamber of the cassette 2, and the rod 3 is lowered to load the lower portion of the cassette into the crucible until a proper position is reached. After lowering the cassette, the second layer growth solution 6 is introduced into the liquid reservoir 4 and the cassette 2
Is lowered to the arrangement shown in FIG. When the inside of the crucible stabilizes at a predetermined temperature, the rod 3 is operated to lower the cassette 2, and the first layer growth solution 9 at the bottom of the crucible is passed through a slit (not shown) provided in the cassette 2.
To the growth chamber 10 of the cassette 2 and the substrate 11 in the cassette
Is completely immersed in the solution 9, the rod 3 is maintained at this position, and the first layer is grown by cooling according to the temperature program shown in FIG. 3, for example. Then, by rotating the rod 3, the outlet 7 for the second layer growth solution 6 is aligned with the groove 8 provided in the inner wall of the crucible 1, and the rod is raised by a predetermined distance at this position. The growth solution 6 is introduced into the growth chamber in the cassette or at the bottom of the crucible and the solutions are mixed. The mixing of the solutions 6 and 9 can be carried out by moving the rod 3 up and down, rotating, etc., and can be made uniform. When uniform mixing and temperature stabilization are ensured, the second layer is epitaxially grown according to a similar temperature program. Thus, it is possible to obtain a large amount of substrates in one cycle operation without continuously taking out the substrate during the growth, and thus without causing problems such as oxidation of the already grown film.

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples, and the effects achieved by the present invention will be demonstrated. However, the scope of the present invention is not limited to the following examples.

Example 1 In this example, G for an LED is formed by a liquid phase epitaxial growth method.
The aAlAsPN junction was grown. First, a Zn-doped P-type GaAs wafer was used as the substrate, Zn was used as the dopant of the P-type layer (first layer), and Te was used as the dopant of the N-type layer (second layer). A Ga melt was used as a solvent for the growth solution, and the above-mentioned dopants, Al and non-doped GaAs as an As source were dissolved therein. The amount of each component added is, for example, as shown in Table 1 below. Under such conditions, the apparatus shown in FIG. 1 was used to obtain two kinds of samples A and B. Further, for each of the samples A and B, the temperature program for crystal growth was as shown in FIGS. 3 (a) and 3 (b), respectively.

When the epitaxial layer obtained by this method is compared with the epitaxial layer which has been grown for the first time and exposed to the air as in the conventional hard dip method, the unevenness of the PN interface due to the influence of the oxide film on the first surface is observed. However, it was found to have a flat interface.

EFFECTS OF THE INVENTION According to the method and apparatus of the present invention, when two or more epitaxial layers are formed, the growth surface is not exposed to air or an oxidizing gas or other atmospheric gas that adversely affects the growth process. Therefore, there is no fear of oxidation. Further, since a uniform epitaxial growth layer can be formed on a large number of wafers by one growth operation, mass productivity is excellent.

Moreover, the device itself is compact, space-saving and the installation is simple.

Incidentally, by increasing the number of solution reservoirs on the upper part of the cassette, it is possible to perform epitaxial growth of a multilayer structure of three layers or more in one operation.

INDUSTRIAL APPLICABILITY The present invention can be applied to all fields in which a laminated epitaxial thin film having two or more layers is required, and can be used for producing various semiconductor elements such as LEDs and semiconductor lasers, devices, etc. It is expected that the product can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing a preferred embodiment of the device of the present invention, and FIGS. 2 (a) and 2 (b) similarly show the first embodiment of the device of the present invention.
3A and 3B are schematic plan views (a) and cross-sectional views (b) for explaining another preferred embodiment different from the drawings, and FIGS. 3 (a) and 3 (b) are respectively utilized in Examples of the present invention. It is a figure which shows the temperature program of epitaxial growth. (The main reference number) 1 ...... crucible, 2 ...... cassette, 3 ...... rod, 4,4 ₁
〜 4 ₃・ ・ ・ Storing solution, 5 ・ ・ ・ Dish, 6 ・ ・ ・ Second layer growth solution, 7 ・ ・ ・ Solution outlet, 8 ・ ・ ・ Groove, 9 ・ ・ ・ First layer growth solution, 10 ・ ・ ・ Growth chamber , 11 …… Board, 12 (12 _{1 to} 12 ₃ ), 1
4, 16 …… Aperture, 13 …… Slit, 15 …… Groove, 17 …… Tube

Claims (11)

[Claims] 1. A device comprising a crucible supported in a furnace and a support member supporting a substrate immersed in a growth solution contained in the crucible, and a plurality of devices are provided under a predetermined temperature history. Is a liquid phase epitaxial growth method for forming an epitaxial layer on a substrate, the crucible having a cylindrical side wall and having an opening at the top, and a side wall outer surface complementary to the inner surface of the side wall of the crucible and having an inner portion. A cassette that is provided with a growth chamber and can move up and down in the crucible and can be horizontally rotated at the same time; a substrate support member housed in the cassette; and a cassette installed at the upper end of the cassette and located inside the crucible. A rod that is operated when the cassette is moved or rotated from the outside of the crucible, and further, a through hole that connects the growth chamber formed in the side wall of the cassette to a side surface of the cassette, and a through hole of the cassette. A device having a groove formed on the outer surface of the side wall or on the inner surface of the side wall of the crucible is used, and the rod is operated to vertically move or horizontally rotate the cassette to connect the through hole and the groove. A liquid phase epitaxial growth method comprising the steps of introducing or discharging a growth solution into a growth chamber and continuously performing liquid phase epitaxial growth of a multilayer film without taking out the substrate from the growth chamber. 2. The method according to claim 1, wherein the multilayer film is a compound semiconductor thin film layer. 3. The method according to claim 1 or 2, wherein the crystal growth liquid also contains a dopant. 4. A crucible supported in a furnace, and a support member for supporting a substrate immersed in a growth solution contained in the crucible, and the crucible in the crucible under a predetermined temperature history. A liquid phase epitaxial growth apparatus for forming a plurality of epitaxial layers on a substrate, comprising: a crucible having a cylindrical side wall and an upper opening, and a side wall outer surface complementary to an inner surface of the side wall of the crucible and having an inner portion. A cassette that is provided with a growth chamber and can move up and down in the crucible and can rotate horizontally at the same time; a substrate support member housed in the cassette; and a cassette mounted on the upper end of the cassette and located inside the crucible. A rod which is operated when the cassette is moved or rotated from the outside of the crucible, the through hole for communicating the growth chamber formed in the side wall of the cassette with the side surface of the cassette, and the cassette. A groove formed on the outer surface of the side wall or on the inner surface of the side wall of the crucible, wherein the through hole and the groove communicate with each other when the cassette is at a predetermined position. Epitaxial growth equipment. 5. A solution reservoir containing a growth solution, which is arranged at a position higher than the growth chamber at least when the cassette is at the lowest position, and has an outlet communicating with the inner surface of the side wall of the crucible. Device according to claim 4, characterized in that it comprises at least one. 6. The solution reservoir is integrally provided with the cassette on the upper portion of the cassette, and is continuous from the bottom of the crucible so as to communicate with the outlet when the cassette is in a predetermined position. The apparatus according to claim 5, further comprising a groove formed on an inner surface of a side wall of the crucible. 7. The bottom of the crucible contains the growth solution, and the growth solution flows into the growth chamber through the through hole when the cassette is at the lowest position. A device according to claim 6, characterized in that 8. The apparatus according to claim 7, wherein the growth solution can be agitated by moving or rotating the cassette. 9. A cassette comprising a plurality of the solution reservoirs outside the crucible, each solution reservoir having an outlet communicating with an inner surface of a side wall of the crucible, and the cassette when the cassette is in a predetermined position. 6. The device according to claim 5, wherein the through hole is configured to selectively communicate with any one of the outlets. 10. An outlet for communicating to the outside is provided on the bottom side of the cassette, and an outlet for communicating to the outside is provided on the bottom of the crucible, and the bottom of the crucible is provided on the inner surface of the inner wall of the crucible. A groove extending upwardly from the chamber and communicating with the outlet of the cassette at a predetermined position, the growth solution in the growth chamber is provided at the outlet and the outlet when the cassette is at the predetermined position. Device according to claim 9, characterized in that it is arranged to be discharged to the outside of the crucible via a groove. 11. The device according to claim 4, wherein the support member is a dish-shaped member having a plurality of holes.