WO2004024999A1 - Reactor for liquid phase epitaxy method - Google Patents

Abstract

The invention relates to a reactor for a liquid phase epitaxy on semiconductor substrates. The inventive reactor comprises a growth chamber which is provided with a temporary storage area which makes it possible to temporarily store at least one substrate. The growth chamber is embodied in such a way that it is pivotable between a reserve position in which a molten masse contained in the growth chamber is accumulated in the temporary storage area, and an epitaxy position in which the molten masse contained in the growth chamber is accumulated in the epitaxy area in order to produce the epitaxy of a crystalline layer on the substrate stored therein. The inventive epitaxy method is also disclosed.

Description

 Vishay Semiconductor GmbH

Liquid phase epitaxy reactor and method

The invention relates to a reactor and a method for the liquid-phase epitaxial growth of one or more monocrystalline layers on a semiconductor substrate, for example a substrate of a III-V semiconductor, such as GaAs.

For liquid phase epitaxy, for example, the use of a horizontal reactor with immersion technology is known, in which the substrates are arranged on a substrate holder above a crucible with different melting chambers. The substrate holder is moved horizontally over the crucible. As soon as the substrates are at the level of the desired melting chamber, they are immersed in the melt by vertical movement of the substrate holder and separated from the melt by subsequent upward movement. By moving to several melting chambers, layers with different material compositions can be deposited in succession in order to produce a multi-layer structure on the substrates. A disadvantage of this horizontal reactor, however, is that only substrates of a limited size can be processed, since the volume of the reactor is otherwise too large due to the two-dimensional substrate movement, so that heat convection prevents uniform layer growth. As a result, this technology does not allow the use of GaAs substrates larger than 2.5 "(= 63.5 mm). A vertical reactor with vertical melt flow is also known. In this case, the melt is located in a crucible above an arrangement of a plurality of horizontally aligned substrates stacked one on top of the other. The melt flows downward due to gravity, with the substrates being wetted one after the other. This reactor technology enables a high capacity, i.e. a large number of substrates, which can be processed together in a single process. However, in this vertical reactor it is difficult to separate the substrates from the melt, so that the layer thickness cannot be set as desired and additional layers cannot be deposited easily.

It is therefore an object of the invention to provide an improved reactor and an improved process for the liquid-phase epitaxial growth of one or more monocrystalline layers on a semiconductor substrate. In particular, it should also be possible to grow multilayer structures with large substrates and with a large reactor capacity.

This object is achieved by the features of independent claims 1 and 26, and in particular in that the melt is first collected within an intermediate storage area of a growth chamber, and that the melt is then in a growth area of the growth chamber, in which at least one substrate is stored, is melted in order to grow a crystal layer on the substrate, and that the melt is then collected again in the intermediate storage area of the growth chamber.

According to the invention, a growth chamber is therefore provided with a growth area in which one or more substrates are in a fixed position are arranged. The melt is first collected in an intermediate storage area of the growth chamber. In order to grow a crystal layer on the substrates, the melt is temporarily transferred from the intermediate storage area to the growth area.

It is important that the melt performs an essentially lateral movement so that a plurality of substrates and larger substrates can be wetted easily and quickly with the melt and the melt can also be easily and safely removed from the substrates again at a predeterminable later point in time can be. The required sideways movement of the melt is advantageously achieved by tilting or pivoting the growth chamber so that the melt flows into the respectively provided area of the growth chamber due to the gravity acting on the melt.

Insofar as the collection of melt in the intermediate storage area or the growth area is mentioned in connection with the invention, this preferably relates to the entire melt located within the growth chamber. However, it is sufficient if at least the major part of the melt is collected in the area in question.

An advantage of the invention is that only a small volume is sufficient for the growth chamber, since no movement of the substrates is required within the growth chamber. This avoids heat convection problems that could prevent the use of large substrate sizes. The invention thus enables the processing of very different and also very large substrate sizes, for GaAs for example up to 4 "(= 101.6 mm) or even 6 "(= 152.4 mm). This means that the yield can be increased significantly compared to conventional technologies which, for example, allow substrates up to 2.5" (= 63.5 mm).

A particular advantage of the invention is that, as already mentioned, multilayer structures can also be easily produced, for example with four or five different crystal layers on top of one another. This is important, for example, for the production of infrared LEDs for use in data transmission with high light outputs and modulation frequencies, since such layer structures have to be provided with a double heterostructure. Such multilayer structures are produced in a simple manner by repeating the growth steps mentioned for the different layers in succession with different melts.

Finally, another advantage of the invention is the high flexibility with regard to the treatment of different substrates, that is to say different materials and different substrate sizes. The reactor according to the invention is therefore very versatile.

The growth chamber is preferably tilted about a horizontal axis for the movement of the melt between the intermediate storage area and the growth area. The reactor can have a support on which the growth chamber is mounted such that it can be tilted, for example on two opposing storage devices. Furthermore, a drive device can be provided which is articulated on the growth chamber in order to be able to drive the growth chamber to the desired tilting movement. As already mentioned, the substrate or the plurality of substrates are preferably provided in a fixed arrangement within the growth area of the growth chamber, so that no mechanism is required for an additional movement of the substrates and there is no corresponding space requirement.

It is preferred if the growth chamber in the growth area has one or more holding devices for attaching the substrates or for attaching substrate carriers. This holding device can have, for example, a simple fastening groove on the wall or on the bottom of the growth chamber.

It is further preferred if the reactor used has a crucible for melting and homogenizing melt above the growth chamber, from which melt can be transferred to the growth chamber. This is then possible in a simple manner due to the gravity acting on the melt. This crucible preferably has a plurality of melting chambers for melting and homogenizing different melts, which can be filled into the growth chamber in succession in order to grow several different crystal layers on the same substrate.

Furthermore, a collecting crucible can be provided below the growth chamber, into which the melt remaining in the growth chamber after a growth process can be drained. Such a collecting crucible can also have a plurality of collecting chambers in order to be able to receive different melts separately when growing more layer structures. Further embodiments of the invention are mentioned in the subclaims. The invention is explained below by way of example with reference to the drawings; in these show:

1 is a schematic side view of a reactor,

2 and 3 parts of this reactor during the collection of

Melt in a growth area or an intermediate storage area,

Fig. 4 is a crucible in plan view, and

5a and 5b different substrate carriers.

1 shows the basic structure of a reactor for liquid phase epitaxy on semiconductor substrates. This reactor has an essentially cuboidal growth chamber 11 made of graphite, which - as shown by broken lines - has an intermediate storage area 13 and a growth area 15.

The growth chamber 11 has a filling opening 17 on the upper side of the intermediate storage area 13. The growth chamber 11 has a depression on the underside of the intermediate storage area 13, which opens into an outlet opening 19. This is closed by a graphite ball 21 prestressed downwards.

A plurality of substrate plates 23 with semiconductor substrates 25 embedded therein are fastened in a fixed arrangement within the growth region 15 of the growth chamber 11, the substrate plates 23 being aligned parallel to one another and parallel to the bottom of the growth chamber 11 are. The substrate plate 23 are held by a holding device 27, which is formed by reinforcing the end wall of the growth chamber 11 and has a plurality of fastening grooves 29, into each of which a substrate plate 21 is inserted.

The growth chamber 11 is mounted such that it can be tilted about a horizontal axis on two mutually opposite bearing devices 31.

On the underside of the growth area 15, a drive rod 33 is articulated to the growth chamber 11, which is connected to an electrical eccentric drive, not shown in the figures, and which is able to drive the growth chamber 11 in a tilting movement.

In the state of the reactor shown in FIG. 1, the growth chamber 11 is in a standby position in which it is tilted in the direction of the intermediate storage area 13. A melt 35 ^″ located in the growth chamber 11 is therefore located exclusively in the intermediate storage area 13.

The reactor shown in FIG. 1 also has a crucible 37 made of graphite for melting and homogenizing melt 35 above the growth chamber 11. The crucible 37 has a cylindrical basic shape. It is divided into six melting chambers 39. These adjoin a central hollow shaft 41 and each have a circular segment shape in the plan view according to FIG. 4. Each melting chamber 39 has a discharge opening on its underside (not shown in the figures). The crucible 37 can be driven by a drive device, not shown in the figures, to rotate about a central vertical axis or about the axis of the hollow shaft 31. A graphite turntable 43 adjoins the underside of the crucible 37 and has a passage opening 45 and a closed blocking section 47. The turntable 43 can be rotated about the same vertical axis, irrespective of a rotation of the crucible 37, in order to bring the passage opening 45 or the blocking section 47 to coincide with the discharge opening of a melting chamber 39.

Below this possible arrangement of the discharge opening of the melting chamber 39 and the passage opening 45 of the turntable 43 there is a guide tube 49 which opens into the filling opening 17 of the growth chamber 11, provided that the growth chamber 11 is in the standby position according to FIG. 1.

Below the growth chamber 11 there is a collecting crucible 51 which is provided for receiving the melt 35 discharged from the growth chamber 11. The collecting crucible 51 also has six collecting chambers 53 for receiving different melts 35. The collecting crucible 51 can be rotated about a central vertical axis, specifically in synchronization with a rotary movement of the melting crucible 37.

Furthermore, a guide tube 55 is provided which connects the outlet opening 19 of the growth chamber 11 to an associated collecting chamber 53 of the collecting crucible 51, provided that the growth chamber 11 is in the standby position shown in FIG. 1. Within the guide tube 55 there is an actuating rod 57 which can be moved vertically upwards in order to push the graphite ball 21 upwards and thus open the outlet opening 19 of the growth chamber 11.

The reactor shown in Figure 1 works as follows: Various melts 35 can be homogenized in the melting chambers 39 of the crucible 37.

By bringing the delivery opening of a desired melting chamber 39 and the passage opening 45 of the turntable 43 into alignment with the guide tube 49 by rotating the crucible 37 and rotating the turntable 43, the relevant melt can be brought into the growth chamber through the guide tube 49 and via the filler opening 17. mer 11 are transferred. By turning the blocking section 47 into the space between the discharge opening of a melting chamber 39 and the guide tube 49, the inflow of melt 35 into the growth chamber 11 is prevented. The turntable 43 thus acts as a closing device by means of which the filling of melt 35 from the crucible 37 into the growth chamber 11 can optionally be made possible or interrupted.

The growth chamber 11 is in the standby position shown in FIG. 1, so that the filled melt 35 is collected in the intermediate storage area 13.

The growth chamber 11 is then tilted into a growth position by means of the drive rod 33 about the pivot axis predetermined by the bearing devices 31, as shown in FIG. 2. This causes the melt 35 to flow predominantly into the growth area 15 of the growth chamber 11. As a result, the substrates 25 are wetted by the melt 35, so that an additional crystal layer is deposited on each substrate 25. The crystal growth can be controlled in a manner known per se by means of a temperature control device which controls a heating device, not shown in the figures, for the interim cooling of the melt 35.

After the desired crystal growth has been reached or after a predefinable time interval has elapsed, the growth chamber 11 is tilted back into the ready position by means of the drive rod 33.

3 shows the growth chamber 11, which is thus inclined again in the direction of the intermediate storage area 13. Now the graphite ball 21, which acts as a locking device, is also pushed upward out of the outlet opening 19 by means of the actuating rod 57. The melt 35 can thus flow from the growth area 15 into the intermediate storage area 13 and from there via the outlet opening 19 into the guide tube 55. In this way, the melt reaches the assigned collecting chamber 53 of the collecting crucible 51.

The steps explained for filling the melt 35 into the intermediate storage area 13, then collecting the melt 35 in the growth area 15 by tilting the growth chamber 11, and then dispensing the remaining melt 35 into the collecting crucible 51 can be repeated in succession for different melts 35, to thereby grow several different crystal layers on the substrates 25. For this purpose, the envisaged melts 35 are melted and homogenized in an associated melting chamber 39 of the crucible 37, or are taken up again in an associated collecting chamber 53 of the collecting crucible 51, the synchronized rotary drive of melting crucible 37 and collecting crucible 51 ensuring that the Assignment of the melts 35 to the melting chambers 39 and the collecting chambers 53 is correctly maintained. The reactor shown in FIGS. 1 to 3 and the method explained in connection with this reactor thus enable crystal layers to be grown on a plurality of semiconductor substrates 25 simultaneously. The reactor can be operated with a high capacity, ie a large number of substrates 25. The growth chamber 11 can namely to a large extent be equipped with the substrates 25, since no space is required for moving the substrates 25 or for a corresponding transport device, and since the further interior of the growth chamber 11 is therefore only for the intermediate storage of the melt 35 in the intermediate storage area 13 is required.

Another advantage of the invention is that a plurality of layers of different material compositions can be deposited on the substrates 25 in succession in order to produce multilayer structures. The wetting of the substrates with melt 35 and the subsequent removal of the melt 35 from the substrates 25 can be carried out quickly and in a controlled manner due to the tilting technique described, and the growth of additional crystal layers can thus be carried out without problems for different melts.

Finally, the following should be noted regarding the reactor shown and the epitaxial process explained:

The substrates 25 or the substrate plates 23 can also be arranged in a different orientation in the growth chamber 11, for example in a vertical orientation parallel to one another or in an orientation such that the substrates 25 in the growth position of the growth chamber 11 according to FIG. 2 are aligned horizontally. 5a and 5b show that the substrate plates 23 can optionally be equipped with individual large substrates 25 of, for example, 4 "(= 101.6 mm) or several smaller substrates 25 of 2" (= 50.8 mm). The reactor according to the invention can thus be used flexibly with regard to the size and type of substrates 25.

It should also be noted that the subdivision of the growth chamber 11 into the intermediate storage area 13 and the growth area 15 can take any shape, the two areas 13, 15 also being able to merge into one another. However, it is important that a predetermined location of the melt 35 is defined in the standby position and the growth position of the growth chamber 11 in order to be able to carry out a controlled wetting of the substrates 25 with the melt 35.

In addition, the growth chamber 1 1 does not necessarily have to be cuboid, of course. Instead, for example, a cylindrical shape is also conceivable, or the outline of an inverted "V". The last-mentioned embodiment can ensure that when the growth chamber 11 is tilted between the ready position and the growth position, the entire melt 35 is arranged either exclusively in the intermediate storage area 13 or in the growth area 15. LIST OF REFERENCE NUMBERS

growth chamber

Temporary storage area

growing area

fill opening

outlet

graphite ball

substrate plate

substratum

holder

mounting groove

Storage facility

drive rod

melt

melting pot

melting chamber

hollow shaft

turntable

Port

blocking portion

guide tube

catch pan

collecting chamber

guide tube

Confirmation bar

Claims

Expectations 1. A reactor for liquid phase epitaxy on semiconductor substrates (25), having a growth chamber (11), the growth chamber having an intermediate storage area (13) for the intermediate storage of melt (35) and a growth area (15) for storing at least one substrate (25), and wherein the growth chamber (11) can be tilted between a standby position in which the melt (35) located in the growth chamber is collected in the intermediate storage area (13) and a growth position in which the melt located in the growth chamber in the growth area (15) is collected in order to grow a crystal layer on the substrate (25) stored there. 2. Reactor according to claim 1, characterized in that the growth chamber (11) can be tilted about a horizontal axis. 3. Reactor according to one of the preceding claims, characterized in that the growth chamber (11) is tiltably mounted on a support (31). 4. Reactor according to one of the preceding claims, characterized in that that a drive device (33) is articulated to the growth chamber (11), through which the growth chamber can be driven to tilt. Reactor according to one of the preceding claims, characterized in that the growth chamber is inclined in the standby position in the direction of the intermediate storage area (13) and in the growth position in the direction of the growth area (15). 6. Reactor according to one of the preceding claims, characterized in that the substrate (25) is provided within the growth region (15) in a fixed arrangement with respect to the growth chamber (11). 7. Reactor according to one of the preceding claims, characterized in that the growth chamber within the growth region (15) at least one holding device (27) for fastening the substrate (25) or for fastening a substrate carrier (23). 8. Reactor according to claim 7, characterized in that the holding device (27) has a fastening groove (29) which is formed on a wall or on the bottom of the growth chamber (1 ^ ^' . 9. Reactor according to one of the preceding claims, characterized in that that the substrate (25) is provided within the growth region (15) in an orientation parallel to the bottom of the growth chamber (11). 10. Reactor according to one of the preceding claims, characterized in that the arrangement of a plurality of substrates (25) is provided within the growth region (15) of the growth chamber (11), in particular in an arrangement parallel to one another. 11. Reactor according to one of the preceding claims, characterized in that the growth chamber (11) has the shape of a hollow cuboid. 12. Reactor according to one of the preceding claims, characterized in that the growth chamber (11) is made of graphite. 13. Reactor according to one of the preceding claims, characterized in that the growth chamber (11) has a filling opening (17) for introducing melt (35) which is arranged on the intermediate storage area (13) of the growth chamber. 14. Reactor according to one of the preceding claims, characterized in that a melting crucible (37) for melting melt (35) is arranged above the growth chamber (11), from which melt can be transferred into the growth chamber. 15. Reactor according to claim 14, characterized in that a closing device (43) is provided, through which the filling of melt (35) from the crucible (37) into the Growth chamber (11) can either be enabled or interrupted. 16. Reactor according to one of the preceding claims, characterized in that the crucible (37) has a plurality of melting chambers (39) for melting different melts (35). 17. Reactor according to claim 16, characterized in that each melting chamber (39) has a discharge opening, that the crucible (37) can also be driven to rotate, around the discharge opening of a predeterminable melting chamber with a filling opening (17) of the growth chamber (11) and that a turntable (43) with at least one passage opening (45) and a closed blocking section (47) is arranged below the crucible (37), the passage opening or the blocking section optionally being rotated into the space between by rotating the turntable the filling opening of the growth chamber and the one brought into congruence with it Passage opening is insertable. 18. Reactor according to one of the preceding claims, characterized in that that the growth chamber (11) has an outlet opening (19) for dispensing melt (35), which is arranged within the intermediate storage area (13). 19. Reactor according to one of the preceding claims, characterized in that a closing device (21) is provided, through which the delivery of melt (35) from the outlet opening (19) of the growth chamber can be made possible or interrupted. 20. Reactor according to claim 19, characterized in that the closing device has a closure ball (21) which optionally in a closed position, the outlet opening (19) Covering the growth chamber or exposing the outlet opening in a release position. 21. Reactor according to claim 20, characterized in that the closing device has an actuating element (57) through which the closure ball (21) can be moved from the closure position into the release position. 22. Reactor according to one of the preceding claims, characterized in that a collecting crucible (51) for below the growth chamber Receiving the melt discharged from the growth chamber is arranged. 23. Reactor according to claim 22, characterized in that the collecting crucible has a plurality of collecting chambers (53) for receiving different melts (35). 24. Reactor according to claim 23, characterized in that the collecting crucible (51) can be driven with a melting crucible (37) arranged above the growth chamber (11) for a common rotary movement. 25. Reactor according to one of the preceding claims, characterized in that the growth chamber (11) has a heating device for heating the melt (35) located in the growth chamber, and that a control device is provided for controlling the heating device. 26. A method for liquid phase epitaxy on semiconductor substrates (25), in particular by means of a reactor according to one of the preceding claims, in which a melt (35) is collected in an intermediate storage area (13) of a growth chamber (11), in which the growth chamber is also from a standby position is tilted into a growth position in order to collect the melt (35) in a growth area (15) of the growth chamber and to grow a crystal layer on at least one substrate (25) stored there, and in which the growth chamber returns from the growth position is tilted into the standby position in order to collect the remaining melt (35) again in the intermediate storage area (13). 27. The method according to claim 26, characterized in that the melt (35) is transferred from a crucible (37) into the intermediate storage area (13) of the growth chamber. 28. The method according to claim 26 and 27, characterized in that after the growth of the crystal layer, the remaining melt (35) from the intermediate storage area (13) of the growth chamber is released into a collecting crucible (51). 29. The method according to any one of the preceding claims 26 to 28, characterized in that at least the steps of collecting the melt (35) in the intermediate storage area (13), - subsequently collecting the melt in the growth area (15) by tilting the growth chamber ( 11), and the renewed collection of the remaining melt (35) in the intermediate storage area (13) by tilting back the growth chamber in succession for several different melts (35) in order to grow a multilayer structure on the substrate (25).