KR19990041526A - Vertical liquid epitaxial device - Google Patents

Abstract

The present invention relates to a vertical LPE apparatus, which is provided with a supply pipe (18) and an exhaust pipe (20) and sealed with a cover (12), so that heat can be applied to the quartz pipe (10). The heating rod 14, a rotating rod 22 which is rotated by a rotating means outside the quartz tube 10 and penetrates the cover 12, and is installed inside the quartz tube 10 and the rotating rod 22. In the vertical LPE apparatus which is composed of a crystal growth portion connected to the semiconductor semiconductor layer of the MQW layer to grow in the crystal growth portion, the heating furnace 14 has a side and a bottom of the quartz tube 10. The crystal growth portion can be inserted into the base plate 26, which is supported and fixed by a predetermined support means in the lower center of the inside of the quartz tube 10, and placed on the base plate 26 to place the substrate. Substrate groove is provided so that the center portion may be connected to the rotating rod (22) The groove is provided with a disk-shaped substrate holder 28, a plurality of growth solution holes placed on the substrate holder 28 to accommodate the growth solution is provided in the circumferential direction and the rotating rod 22 penetrates the center thereof. A center hole is provided to be connected to the substrate holder 28 below, and the support plate 26 is formed of a solution holder fixed with a fixing pin. The substrate holder 28 is connected to the rotating rod 22 to support the support plate 26. It is possible to rotate between the solution holder and the solution holder to form a reproducible, uniform MQW layer.

Description

Vertical liquid epitaxial device (Vertical LPE System)

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vertical liquid phase epitaxy (LPE) device. In particular, the reproducibility of growth of semiconductor crystal substrates for the fabrication of bonded lasers can be improved, and the active layer may be improved. It relates to a vertical LPE device that can be made thin and uniform.

In general, laser oscillation in semiconductors has continued to develop since semiconductor laser oscillation by GaAs pn junction has been realized at cryogenic temperatures. Today, laser oscillation is characterized by small size, high efficiency, direct modulation, long life, low driving current, and room temperature continuous oscillation. It is developed as a double-heterostructure bonded laser with the requirements of medium and large-capacity optical transmission light source and compact disk light source.It is a semiconductor with a wavelength of 1.2 ~ 1.6μm with low propagation loss due to the advance of optical fiber manufacturing technology. A mixed crystal of a group III-V compound, which is a laser, was made to enable long-distance, large-capacity optical transmission. Among the mixed crystals of the group III-V compounds, the InGaAsP system capable of continuous operation at room temperature and having a long lifetime is the most representative one, and is mainly manufactured by crystal growth on an InP crystal substrate.

Practical manufacturing methods of III-V semiconductor devices include liquid phase growth method represented by LPE method, gas phase growth method of MOVPE (Metal Organic Vapor Phase Epitaxy) method, and molecular beam growth method of MBE (Molecular Beam Epitaxy) method. Although it was developed later than the former, the reproducibility of the growth layer thickness can be easily secured, and the growth thickness of several tens of micrometers can be controlled, so the frequency of use is relatively increased.

However, since the electrons grow in the equilibrium state of the growth solution, the growth layer quality is superior to other growth methods, the growth equipment is simple and compact, and the equipment and maintenance costs are relatively low. If it is possible to grow a multi-quantum well layer (hereinafter referred to as an 'MQW layer'), it is expected to be a useful thin film crystal growth apparatus from an industrial point of view.

The LPE method epitaxially grows the liquid in a group III semiconductor melted with group III, group V and group III-V elements in contact with the surface of the substrate while lowering the temperature. That is, the LPE device can be divided into two types, vertical and horizontal. The vertical type is quartz tube in the vertical direction and the horizontal type quartz tube is installed in the horizontal direction. However, there are advantages and disadvantages depending on the purpose of use and the installation environment. It has advantages over the horizontal type in terms of.

A conventional vertical LPE apparatus is shown in FIG. 1A, and a solution holder and a top plate, which are double crystal growth portions, are shown in FIG. 1B. The device is installed in the cylindrical quartz tube 10 installed in the vertical direction, the cover 12 and the quartz tube 10 side which is coupled to surround the top outer circumference of the quartz tube 10 to seal the inside, A heating unit 14 capable of heating the side surface of the quartz tube 10 is provided, and a substrate holder 28 having a groove in which the substrate can be placed is provided in the center of the quartz tube 10. And a growth solution hole which is placed on the substrate holder 28 and rotated by a quartz rotary rod 22 which is rotated by a stepping motor installed on the top of the cover 12 and can hold several growth solutions in the circumferential direction. It consists of a solution holder (30). In addition, a supply pipe 18 capable of supplying nitrogen and hydrogen gas and an exhaust pipe 20 for discharging gas inside the quartz tube 10 are installed to penetrate through the cover 12, and the exhaust pipe 20 has a burner and a vacuum. The pump is connected.

A temperature monitor 16 is installed below the substrate holder 28 to monitor the growth temperature from the outside.

The growth solution hole of the solution holder 30 is provided with a lid 36 for each hole.

The quartz tube 10 is made of pure quartz that does not affect the reaction, and the airtightness of the quartz tube 10 by contraction and expansion of the quartz tube 10 due to temperature change at the contact point between the quartz tube 10 and the cover 12. In order to solve this fall problem, the cooler 34 is provided.

The heating unit 14 maintains the temperature around the substrate holder 28 at a desired temperature, and operates while monitoring the temperature around the substrate holder 28.

The substrate holder 28 and the solution holder 30 are usually made of ultra-high purity (more than 99.999%) graphite, which has good thermal conductivity and little friction and solution adhesion, and should have good accuracy and flatness. The post-treatment should be able to achieve the purity of the original material and should be kept clean by continuous baking.

The solution holder 30 is rotated by the rotation of the rotating rod 22 connected to the center on the fixed substrate holder 28.

At this time, the problem of maintaining the distance between the substrate holder 28 and the solution holder 30 is very important for crystal growth and residual solution separation (hereinafter referred to as "wipe off"). That is, when the distance between the substrate holder 28 and the solution holder 30 is 75 μm or more, the wipe off of the growth solution is poor, resulting in melt carry-over, which causes indium drop (In drop) to occur. In addition, the epi layer melts back, resulting in uneven growth of the composition upon contact with the next growth solution, and abnormal growth may occur. If the interval is less than 25 μm, it remains in the growth solution when the growth solution is separated. As the surface grown by the crystal grains is scratched, a trace of the growth solution remains, thereby degrading the quality of the epitaxial layer and having a non-uniform characteristic when manufacturing the device.

In order to prevent the incorporation of foreign substances such as air, which impedes the growth of crystals, it is important to make the vacuum while maintaining the airtightness in the quartz tube 10 as much as possible, and the exhaust pipe 18 for maintaining the vacuum in the quartz tube 10 is vacuum. And a burner and a vacuum pump for burning the hydrogen gas discharged to the exhaust pipe 18 before being discharged into the air are connected.

In addition, the reason why the supply pipe 18 is installed to supply nitrogen gas is to blow out hydrogen gas after crystal growth and to suppress evaporation of group V elements and to suppress the inflow of air, and to supply hydrogen gas. Is for removing oxygen generated in the quartz tube 10 by using the atmospheric gas as hydrogen.

An MQW layer is formed using a vertical LPE device having such a structure. For example, a process of repeatedly growing InGaAsP and InP will be described below.

First, the InGaAsP solute and InP solvent corresponding to the composition ratio of each layer are contained in the solution holder 30 and installed on the substrate holder 28 on which the InP substrate is mounted. Subsequently, the quartz tube 10 is made into a vacuum of about 10-3 Torr, flowed with high purity hydrogen gas, maintained at a pressure slightly higher than atmospheric pressure, and heated until the growth solution is maintained in a supersaturated state. Once the supersaturation state is reached, when the solution holder 30 is rotated while the temperature is lowered, the growth solution comes into contact with the substrate to form crystal growth on the substrate in each of InGaAsP and InP layers.

By the way, in the crystal growth process using the conventional vertical LPE device having the structure as described above, since the growth solution is rotated in the state in which the substrate is fixed, there is a deflection of the rotating rod 22 and the deviation of the central axis There is a risk that the solution holder 30 is unstable rotational movement, the rolling phenomenon caused by the growth solution is rotated, the equilibrium state of the growth solution is broken, the growth rate is irregular, it is difficult to form a thin and reproducible MQW layer There is a problem.

The present invention has been made to solve the above problems, and an object thereof is to provide a vertical LPE device capable of forming a thin and reproducible MQW layer.

The vertical LPE apparatus of the present invention for achieving the above object is a quartz tube which is provided with a supply pipe and an exhaust pipe and is closed by a cover, and a heating furnace capable of applying heat to the quartz tube, and rotating outside of the quartz tube. A vertical LPE which is rotated by means and is provided with a rotating rod installed through the cover and a crystal growth portion installed inside the quartz tube and connected to the rotating rod, thereby allowing compound semiconductor crystals of the MQW layer to be grown in the crystal growth portion. In the apparatus, the heating furnace has a groove in which the side and the bottom of the quartz tube can be inserted and is capable of dissipating heat through the side and the bottom of the groove, wherein the crystal growth portion is inside the quartz tube. The base plate is provided with a disc-shaped support plate which is supported and fixed by a predetermined support means at the lower center, and a substrate groove is placed on the support plate to place the substrate. Is a disk-shaped substrate holder provided with a bearing which can be connected to the rotating rod, and several growth solution holes placed on the substrate holder and capable of containing the growth solution are provided in the circumferential direction, and the rotating rod penetrates the center of the lower substrate. The center hole is provided to be connected to the holder and made of a solution holder fixed to the support plate and the fixing pin, the substrate holder is connected to the rotating rod to be able to slide and rotate between the support plate and the solution holder. .

In such a vertical LPE apparatus, a crucible made of a material having a small heat capacity is preferably inserted between the heating furnace and the quartz tube, and a crucible made of zirconium is more preferable. In this case, it is preferable that a kantal line connected to a power source is wound around the outer side and the bottom of the crucible.

In addition, the substrate groove preferably has a depth of 30 ~ 50μm interval between the bottom surface of the solution holder and the substrate surface placed on the substrate holder.

Figure 1a, 1b is a view illustrating a conventional vertical LPE device,

Figure 2 illustrates a vertical LPE apparatus of the present invention,

Figure 3a is a graph of the temperature distribution in the circumferential direction by the heating furnace of the present invention,

Figure 3b is a graph of the temperature distribution in the circumferential direction by a conventional vertical LPE device,

4A, 4B, and 4C are views illustrating a result of forming a growth layer using the vertical LPE device of the present invention.

* Description of the symbols for the main parts of the drawings *

10 quartz tube 12 cover

14 heating furnace 16 temperature monitor

18: supply pipe 20: exhaust pipe

22: rotating rod 24: crystal growth support

26: support plate 28: substrate holder

30: solution holder 32: ceramic

34: cooler 36: lid

Hereinafter, with reference to the accompanying drawings, the present invention will be described in detail.

Figure 2 illustrates a vertical LPE apparatus according to the present invention, a cylindrical quartz tube 10 installed in the vertical direction and the cover that is coupled to surround the top outer periphery of the quartz tube 10 can be sealed inside ( 12) and a heating furnace 14 into which the quartz tube 10 is inserted, and a supply pipe 18 capable of supplying nitrogen and hydrogen gas and an exhaust pipe 20 for discharging gas inside the quartz tube 10 are provided. It is installed to pass through the inside and outside of the quartz tube 10, the exhaust pipe 20 is connected to the burner and the vacuum pump, the rotary rod 22 is able to rotate in accordance with the rotation of the stepping motor installed on the top of the center cover 12 The penetrating is installed, and the crystal growth unit connected to the rotating rod 22 is installed in the quartz tube 10.

The crystal growth portion is a triangular shaped crystal growth portion supporter 24 having an upper end fixed to the lid 12 at the lower center of the quartz tube 10, and a disc-shaped crystal placed on the crystal growth supporter 24. Substrate plate 26, the substrate holder 28 is provided on the base plate 26, the substrate groove is provided to place the substrate, the central plate is provided with a bearing that can be connected to the rotating rod 22, the substrate holder (28) a plurality of growth solution holes are placed on the circumferential direction to accommodate the growth solution and the central hole is provided so that the rotary rod 22 can be connected to the substrate holder 28 below through the center. The support plate 26 and the solution holder 30 is fixed to the fixing pin, the substrate holder 28 is connected to the rotating rod 22, the support plate 26 fixed to the crystal growth support 24 And slide between the solution holder 30 It will be the make.

Lid 36 suitable for the growth solution hole is provided as in the conventional vertical LPE apparatus.

The heating furnace 14 may use a conventional electric furnace, but it is possible to control the reaction temperature while measuring the temperature with a temperature monitor 16 installed in the crystal growth unit, in the present invention, the growth thickness in the LPE method accurately In order to control and increase the reproducibility, the temperature of the growth solution must be maintained uniform, so that the heat supply can be supplied not only to the quartz tube 10 side but also to the lower portion. The temperature monitor 16 is to insert a thermocouple in the quartz tube to measure the temperature of the crystal growth portion from the outside.

And a large zirconium crucible 32 with a large heat capacity was inserted between the cantal line of the electric furnace and the quartz tube 10 to reduce the temperature nonuniformity in the circumferential direction.

The result of measuring the circumferential temperature characteristic of the electric furnace having such a structure is shown in FIG. 3A and the temperature deviation obtained in the conventional vertical LPE apparatus shown in FIGS. 1A and 1B is shown in FIG. 3B for comparison.

According to FIGS. 3A and 3B, the temperature deviation in the circumferential direction is stable at about ± 0.1 ° C., which is about five times better than the ± 0.5 ° C. required by the LPE method, and is better than the ± 1.0 ° C. obtained with a conventional LPE device. It shows much better performance.

Then, the cover 12 and the quartz tube 10 are brought into close contact with each other to fit the cover 12 coupling portion using an O-ring to the upper coupling portion of the quartz tube 10 in order to improve airtightness in the quartz tube 10. In order to prevent the deterioration of the O-ring, the cover 12 is manufactured in a structure in which cooling water can flow efficiently around the coupling portion to increase cooling efficiency.

In detail, the crystal growth unit is divided into three parts that allow crystal growth to occur on a substrate to form an MQW layer.

First, the support plate 26 positioned at the bottom and fixed to the crystal growth support 24 is made of high-purity graphite material, and serves to support the operation of the substrate holder 28 positioned at the top. It is to perform the function of fixing the top solution holder (30). In this case, the crystal growth unit support 24 may use various support means different from those of the present embodiment, and the support plate 26 may be fixed at the lower center of the quartz tube 10. In this embodiment, the trivet shape fixed to the lid 12 was used.

The second substrate holder 28 is placed on the supporting plate 26, and a bearing is formed at the center thereof to be connected to the rotating rod 22. The bearing can be rotated by the rotation of the rotating rod 22. The groove is formed in the upper predetermined position to place the substrate.

In the solution holder 30, a plurality of through holes are formed in the center and the circumferential direction so that the growth solution hole in the circumferential direction can contain the growth solution, and the through hole in the center is the rotary rod 22 or the substrate holder 28. ), The bearings can be penetrated, and can be connected and fixed using the support plate 26 and a conventional fixing means. However, it is preferable that the fixing means uses an inert material without receiving much temperature influence. FIG. 2B shows that the base plate 26 and the solution holder 30 are fixed with pins made of quartz as an example of such fixing.

The substrate groove has a depth of 30 to 50 μm between the bottom surface of the solution holder and the substrate placed in the substrate groove of the substrate holder 28 to facilitate the wipe-off. The impact was somewhat mitigated.

As such, the crystal growth unit including the support plate 26, the substrate holder 28, and the solution holder 30 in three stages has a substrate holder 28 connected to the rotating rod 22 while the solution holder 30 and the support plate 26 are fixed. ) Can be rotated in the center.

Accordingly, in the conventional vertical LPE apparatus, the growth solution is shaken or the thermal equilibrium state of the biphasic solution is broken while the growth solution is rotated while the substrate is fixed, and the growth solution is unstable. In the vertical LPE apparatus, the substrate holder 28 is rotated while the solution holder 30 is fixed, so that the growth solution is fixed and crystal growth occurs as the substrate moves, so that the thermal equilibrium is maintained and the growth solution is stabilized. Since the substrate holder 28 is rotated between the 26 and the solution holder 30, the unstable rotational movement can be suppressed.

The MQW layer is actually formed using the vertical LPE device. The experimental results are as follows.

The growth temperature is 630 ℃, and the cooling rate is 0.4 ℃ / min. The InGaAsP layer, which is a quantum well layer, is grown in three layers for one second to form two parts, a center and an edge of each layer. The average thickness and the standard deviation are shown in the following Table 1 by 200 repeated experiments to measure the thickness by dividing. The growth of the crystal was repeated 80 times under the same conditions using a conventional vertical LPE apparatus. The results are shown in Table 2 below.

Results using the crystal growth unit of the present invention Floor name Edge center Average Standard Deviation Average Standard Deviation First floor 189 44 180 39 Second floor 159 28 153 27 Third layer 143 27 141 27

Results Using Conventional LPE Devices Floor name Edge center Average Standard Deviation Average Standard Deviation First floor 455 155 348 110 Second floor 354 120 343 113 Third layer 284 98 282 82

In addition, the results are shown in FIGS. 4A, 4B, and 4C for each layer. This result shows that the average thickness of each layer as well as the uniformity of each layer is significantly reduced when the crystal growth unit of the present invention is used, so that the average thickness is 1/2 and the thickness deviation is reduced by 1/3 or more compared with the conventional one. You can check it.

From the above results, when forming the MQW layer with the vertical LPE device of the present invention, it is possible to improve the temperature characteristics and system stability, it is possible to grow the MQW layer reproducibly, and in particular to ensure the stability of the growth solution MQW There is an effect to improve the thickness uniformity and reproducibility during growth.

Claims (4)

A quartz tube 10 provided with a supply tube 18 and an exhaust pipe 20 and closed by a lid 12, a heating furnace 14 capable of applying heat to the quartz tube 10, and the quartz tube ( 10) a rotating rod 22 which is rotated by an external rotating means and penetrates the cover 12, and is formed of a crystal growth unit installed inside the quartz tube 10 and connected to the rotating rod 22, and includes an MQW layer. In the vertical LPE apparatus which is capable of growing a compound semiconductor crystal in the crystal growth section, the heating furnace 14 has grooves into which the side and bottom of the quartz tube 10 can be inserted, and the side of the groove. And it is able to release heat through the lower portion, the crystal growth portion is a disk-shaped support plate 26 which is supported by a predetermined support means fixed to the lower center of the inside of the quartz tube 10 and the support plate 26 The substrate groove is provided to be placed on the substrate to place the substrate and the rotation in the center Substrate substrate holder 28 is provided with a groove that can be connected to the rod 22, several growth solution holes placed on the substrate holder 28 to accommodate the growth solution is provided in the circumferential direction and the rotary rod ( The substrate holder 28 is formed of a solution holder in which a center hole is provided to be connected to the substrate holder 28 below through the center and fixed to the support plate 26 and the fixing pin. It is connected to the support plate 26 and the vertical type LPE device, characterized in that the slide between the solution holder can be rotated. The furnace (14) according to claim 1, wherein the furnace (14) comprises a crucible (32) made of a material having a small heat capacity between the furnace (14) and the quartz tube (10), and the outer side and the bottom of the crucible (32). Vertical LPE device, characterized in that the Kantal wire wound and connected to the power source. 3. The vertical LPE apparatus as claimed in claim 2, wherein the crucible is made of zirconium. 2. The vertical LPE apparatus according to claim 1, wherein the substrate groove has a depth of 30 to 50 [mu] m between a bottom surface of the solution holder and a substrate surface placed on the substrate holder (28).