JP3515858B2 - Boat for liquid phase epitaxial growth - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a boat for liquid phase epitaxial growth. More specifically, a member for holding a melt containing the raw material of the epitaxial layer and a member for accommodating the semiconductor substrate on which the epitaxial layer is to be formed are slid on each other, and the melt and the semiconductor substrate are brought into contact with each other to form a liquid phase. The present invention relates to a slide boat that performs epitaxial growth.

[0002]

2. Description of the Related Art As a conventional boat for liquid phase epitaxial growth, as shown in FIG. 6 (a), a boat body 101 made of highly purified graphite material and slidable with respect to each other is used. Some are equipped with sliders 102 (entire boat is shown at 110). A melt reservoir 106 having a concave cross section is formed on the lower surface of the boat body 101 for holding a melt containing the raw material of the epitaxial layer. On the other hand, on the upper surface of the slider 102, as shown in FIG. 5, a substrate receiving portion 105 having a concave cross section having a depth corresponding to the thickness of the semiconductor substrate 109 to be subjected to liquid phase epitaxial growth is formed.

When liquid-phase epitaxial growth of a GaAlAs layer, which is a III-V group compound, is performed on a GaAs substrate using this boat 110, for example, the melt reservoir 1 of the boat body 101 is used.
While the raw materials such as Ga, GaAs polycrystal, Al, and doubtant are put in 06, Ga is put in the substrate receiving portion 105 of the slider 102.
The As substrate 109 is housed. As shown in FIG. 6A, the melt reservoir 106 and the substrate receiving portion 105 are displaced from each other in the sliding direction, and the boat 110 is put into the furnace core tube 111 of the growth reactor to create a hydrogen atmosphere. Then, the energization amount of a heater (not shown) installed around the furnace core tube 111 is controlled to raise the set temperature of the growth furnace from room temperature and keep it at a constant temperature (about 900 ° C.) for a certain time. This makes the boat 1
The temperature of the whole 10 is made uniform and the above raw materials are melted to form a melt 108 in a saturated state. Next, as shown in FIG. 6 (b), for example, the boat body 101 is slid in the direction of arrow A with respect to the slider 102, and the melt reservoir 106 is placed on the substrate receiving portion 105 as shown in FIG. 6 (c). Face each other.
As a result, the melt 108 held in the melt reservoir 106 is brought into contact with the surface 109a of the GaAs substrate 109. In this state, the energization amount of the heater is controlled to lower the set temperature of the growth furnace, and the surface 109 of the GaAs substrate 109 is gradually cooled.
A GaAlAs layer is epitaxially grown on a.

[0004]

By the way, in the liquid phase epitaxial growth method (decooling method), in order to obtain a growth start surface having a specific crystallinity, the temperature of the growth furnace is kept constant for a certain time (the above example). Then, the melt 108
When the melt 108 has been saturated and then the melt 108 has been supersaturated, the slider 10 of the boat body 101 is
Start the slide for 2 and melt 10 in the supersaturated state
8 may be brought into contact with the semiconductor substrate 109. In this case, since the melt 108 is in a supersaturated state, the speed of epitaxial growth immediately after the melt 108 contacts the semiconductor substrate 109 becomes very high. Here, the conventional boat 1
In FIG. 10, as shown in FIG. 7 (b), the temperature of each part of the bottom of the substrate receiving portion 105, particularly the sliding direction A in FIG. 7 (a).
The temperature along the X-X line parallel to the
1, t2, t3, ...) And the temperature of each part of the substrate surface 109a also uniformly drops.
Therefore, the difference in the contact time with the melt 108 between the upper portion and the lower portion of the substrate surface 109a in the sliding direction appears as the difference in the epitaxial growth film thickness, and as a result, the difference in the epitaxial growth film thickness. The problem that (variation) becomes large arises.

Further, the conventional boat 110 has a problem that it takes a long time to bring the entire melt 108 into a uniform saturated state at the stage where the melt 108 is saturated before starting the epitaxial growth.

Therefore, an object of the present invention is to provide a boat for liquid phase epitaxial growth which can reduce the difference in the epitaxial growth film thickness on the surface of a semiconductor substrate. Another object of the present invention is to provide a boat for liquid phase epitaxial growth capable of bringing the entire melt into a uniform saturated state in a short time.

[0007]

In order to achieve the above object, a liquid phase epitaxial growth boat according to the present invention comprises a first member having a melt reservoir for holding a melt containing a raw material for an epitaxial layer. A substrate receiving portion having a slide surface capable of sliding facing the surface on which the melt reservoir on the side of the first member is opened and having a concave cross section for accommodating a semiconductor substrate in a specific region within the slide surface. and a second member but formed, is the first member during the epitaxial growth starting
In the liquid phase epitaxial growth boat that is slid relative to the second member, the bottom of the substrate receiving portion of the second member faces the melt reservoir of the first member in order at the start of epitaxial growth. , From the bottom of this bottom
It is characterized in that the lower part is formed so that the thermal conductivity gradually increases.

In the liquid phase epitaxial growth boat of the present invention , the temperature of the bottom of the substrate receiving portion is inclined and lowered from the upper hand portion to the lower hand portion of the bottom as the temperature lowering time elapses. That is, when lowering the set temperature of the growth furnace which accommodates the boat, in accordance with the thermal conductivity of the bottom of the substrate receiving portion of the second member, while the temperature of the well portion of the bottom is lowered slowly, the The temperature of the lower part of the bottom drops quickly. Along with this, the temperature of the part on the upper part of the bottom of the surface of the semiconductor substrate decreases slowly, while the temperature of the part on the lower part of the bottom decreases quickly. As a result, the portion of the upper surface of the bottom of the surface of the semiconductor substrate has a long contact time with the melt, but the temperature slows down and the epitaxial growth rate decreases. On the other hand, in the portion above the lower part of the bottom, the contact time with the melt is short, but since the temperature drops quickly, the epitaxial growth rate increases. Thus, between the bottom well portion on parts and portions of the poor portion of the semiconductor substrate surface, the difference in contact time between the melt is offset by the difference in growth rate due to the temperature gradient. As a result, compared to the conventional
The difference in the epitaxial growth film thickness on the surface of the semiconductor substrate is reduced.

[0009] In boat liquid phase epitaxial growth of an embodiment, the bottom of the substrate receiving portion is poor from the good unit
Section is divided into a plurality of segments each made of a fixed material, and the thermal conductivity of the materials that make up each of the above segments varies from the upper segment to the lower segment.
Characterized in that it is configured to sequentially grow to.

According to the boat for liquid phase epitaxial growth of this one embodiment , the function and effect of the present invention can be obtained. Moreover, in order to produce a liquid phase epitaxial growth boat, on the bottom of the substrate receiving portion of the second member, this
It is sufficient to embed a material having a constant thermal conductivity in each segment so that the thermal conductivity of each segment increases in order from the upper part to the lower part of the bottom . Therefore, this boat for liquid phase epitaxial growth is easily manufactured.

In the liquid phase epitaxial growth boat of one embodiment, the inner wall of the melt reservoir of the first member is divided into at least two segments made of a certain material, and the heat conduction of the materials forming the adjacent segments is performed. Characterized by different degrees.

In the liquid phase epitaxial growth boat of this one embodiment , at the stage where the melt before the start of epitaxial growth is saturated, the opening of the melt reservoir of the first member corresponds to the sliding surface of the second member. Of these, it is arranged so as to face an area above the substrate receiving portion. In this state,
The set temperature of the growth furnace is raised from room temperature and maintained at a constant temperature for a fixed time, whereby the raw material placed in the melt reservoir is melted and becomes a melt. At this time, in this liquid phase epitaxial growth boat, convection occurs in the melt due to the difference in thermal conductivity between the adjacent segments. Therefore, the entire melt is in a uniform saturated state in a shorter time than in the conventional case.

Further, the convection in the melt can be accelerated by periodically raising and lowering the set temperature of the growth furnace. In such a case, the entire melt can be brought into a uniform saturated state in a shorter time.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a boat for liquid phase epitaxial growth according to the present invention will be described in detail below.

FIG. 2 (a) shows a slide type boat (indicated generally by 10) of a first embodiment of the present invention in a reactor core tube 1 of a growth reactor.
The state put in 1 is shown schematically. The sliding boat 10 includes a boat body 1 as a first member and a second boat body 1.
The slider 2 as a member is provided.

The boat main body 1 is formed in a substantially rectangular parallelepiped shape using graphite having a constant thermal conductivity λ0 that has been subjected to high-purity treatment as a material. On the lower surface of the boat body 1, a melt reservoir 6 having a concave cross section for holding a melt 8 containing a raw material for the epitaxial layer is formed.

As shown in FIG. 1, the slider 2 is formed in a substantially rectangular parallelepiped shape using graphite having the same thermal conductivity λ0 as that of the boat body 1 as a base material 2B. The upper surface of the slider 2 is a slide surface 2A that can slide against the lower surface of the boat body 1. Hereinafter, the direction in which the boat body 1 slides with respect to the slider 2 at the start of epitaxial growth is referred to as the slide direction A. An embedding material 4 having a thermal conductivity λ2 smaller than the thermal conductivity λ0 of the base material 2B is embedded on the upper side in a region near the center of the slide surface 2A of the slider 2 with respect to the sliding direction A. Adjacent to the lower side of the material 4 is smaller than the thermal conductivity λ0 of the base material 2B and is embedded material 4
The embedding material 3 having a thermal conductivity λ1 larger than the thermal conductivity λ2 of (1) is embedded (that is, λ2 <λ1 <λ0). The embedding materials 3 and 4 each have a rectangular cross section,
It extends in a direction perpendicular to the sliding direction A. The dimension of the embedding material 3 in the sliding direction A is set to be smaller than the dimension of the semiconductor substrate 9 on which liquid phase epitaxial growth is to be performed in the direction A, and the dimension of the embedding material 4 in the sliding direction A is the direction of the semiconductor substrate 9 in the direction A. It is set larger than the size of. On the other hand, the dimensions (thickness dimension) of the embedded materials 3 and 4 in the depth direction are set to be equal to each other and larger than the thickness dimension of the semiconductor substrate 9, and most of the thickness dimension of the base material 2B. Occupy

On the upper surface of the slider 2, from the area of the base material 2B adjacent to the lower side of the embedding material 3 in the sliding direction A, to the area passing through the area of the embedding material 3 and halfway through the area of the embedding material 4. A substrate receiving portion 5 having a concave cross section for accommodating the semiconductor substrate 9 is formed. The shape of the substrate receiving portion 5 inside the slide surface 2A is set to be substantially the same as the shape of the semiconductor substrate 9 (rectangular in this example). Actually, the size of the substrate receiving portion 5 inside the slide surface 2A is set to be slightly larger than the size of the semiconductor substrate 9 for the convenience of housing or taking out the semiconductor substrate 9. Further, the dimension of the substrate receiving portion 5 in the depth direction is such that the accommodated semiconductor substrate 9 has the sliding surface 2
The thickness is set to be equal to or slightly larger than the thickness dimension of the semiconductor substrate 9 so as not to project above A.

As a result of forming the substrate receiving portion 5 in such an arrangement, the bottom of the substrate receiving portion 5 of the slider 2 is embedded material 4 and embedded material 3 in this order from the upper side to the lower side in the sliding direction A, respectively. , The base material 2B is divided into three segments 5a, 5b, 5c. The thermal conductivity λ2, λ1, λ0 of the material forming each of the segments 5a, 5b, 5c increases in order from the upper side to the lower side in the sliding direction (that is, λ2 <λ1 <λ0).
Is. ). In addition, the regions of the slide surface 2A, which are superior to the substrate receiving portion 5 in the slide direction, are the two segments 2 including the base material 2B and the embedded material 4, respectively.
It is divided into a and 2b. As described above, the base material 2 forming the adjacent segments 2a and 2b
B, the thermal conductivity λ2 and λ0 of the embedding material 4 are different from each other (that is, λ2 <λ0).

Specifically, the base material 2B has a thermal conductivity of 120 kcal / h · m · ° C, and the embedding material 3 has a thermal conductivity of 110 kcal / h · m · ° C. The thermal conductivity of the embedded material 4 is 100 kcal / h.
It is possible to adopt one having a characteristic of m · ° C.

The slide type boat 10 can be produced relatively easily because it can be produced by merely adding the embedding materials 3 and 4 to the slider 2 in the conventional boat.

Liquid phase epitaxial growth is performed as follows using this slide type boat 10. Here, G
A GaAlAs layer, which is a III-V group compound, is to be liquid-phase epitaxially grown on the aAs substrate 9.

I) First, raw materials such as Ga, GaAs polycrystal, Al and doubtant are put into the melt reservoir 6 of the boat body 1, while the GaAs substrate 9 is housed in the substrate receiving portion 5 of the slider 2. As shown in FIG. 2 (a), this slide boat 1
0 is placed in the furnace core tube 11 of the growth furnace to make it a hydrogen atmosphere, and the opening of the melt reservoir 6 is arranged so as to face the boundary between the segments 2a and 2b which are higher than the substrate receiving portion 5 in the sliding direction.

Ii ) Subsequently, the set temperature of the growth furnace is raised from room temperature by controlling the energization amount of a heater (not shown ) installed around the furnace core tube 11, and as shown in FIG. Hold at a constant temperature (about 900 ° C.). As a result, the raw material placed in the melt reservoir 6 shown in FIG. 1 is melted to form a melt 8. Due to the difference between the thermal conductivity of the base material 2B and the thermal conductivity of the embedding material 4 in this temperature raising and holding process (it takes some time for the entire boat to reach a uniform temperature immediately after the temperature is raised). Then, a temperature difference occurs between the segment 2a and the segment 2b that are in contact with the melt 8, and convection occurs in the melt 8 according to this temperature difference. Therefore, the entire melt 8 can be brought into a uniform saturated state in a shorter time than in the conventional case.

The convection in the melt 8 can be accelerated by periodically raising and lowering the set temperature of the growth furnace with respect to the hold temperature. That is, when the set temperature of the growth furnace is vibrated at a certain cycle (preferably determined according to the thickness of the base material 2B and the embedding material 4), the base material 2
Due to the difference in thermal conductivity between B and the embedding material 4, a phase difference occurs between the actual temperature of the segment a and the actual temperature of the segment b. Due to this phase difference, convection in the melt 8 can be accelerated. In such a case, the entire melt 8 can be brought into a uniform saturated state in a shorter time.

Iii ) Next, as shown in FIG. 3, at a time point (t1) after a certain time has elapsed since the preset temperature of the growth furnace was held, the energization amount of the heater was controlled to set the preset temperature of the growth furnace. It is lowered and the melt 8 is supersaturated by slow cooling.

Iv ) Next, at a time point (t2) after a lapse of a certain time from the start of cooling, as shown in FIG.
Slide the slider 2 in the direction of arrow A,
As shown in FIG. 2C, the melt reservoir 6 is opposed to the substrate receiving portion 5. As a result, the melt 8 held in the melt reservoir 6 is brought into contact with the surface 9a of the GaAs substrate 9. In this state, slow cooling is continued to epitaxially grow the GaAs layer on the surface 9a of the GaAs substrate 9.

In this case, as shown in FIG. 4 (b), the temperature of the bottom of the substrate receiving portion 5 is determined by the elapse of the cooling time (t
1, t2, t3, ...) Inclining with respect to the slide direction A and descending. The horizontal axis of FIG. 4 (b) indicates the position in the sliding direction on the slider surface in correspondence with FIG. 4 (a).
The vertical axis of FIG. 4 (b) represents the temperature along the line XX parallel to the sliding direction A in FIG. 4 (a). In this way, when the set temperature of the growth furnace is lowered, the sliding direction of the bottom of the substrate receiving portion 5 depends on the thermal conductivity λ2, λ1, λ0 of the embedding material 4, the embedding material 3 and the base material 2B. While the temperature of the upper hand segment 5a drops slowly, the temperature of the lower hand segment 5c in the sliding direction quickly drops. The temperature of the center segment 5b in the sliding direction drops at an intermediate speed between them. As a result, the portion 9a of the surface of the GaAs substrate 9 which is in the sliding direction is in contact with the melt 8 for a long time, but the temperature slows down and the epitaxial growth rate decreases. On the other hand, the contact portion 9c on the lower side in the sliding direction has a short contact time with the melt 8, but the temperature decreases rapidly, so that the epitaxial growth rate increases. The central portion 9b in the sliding direction has a contact time with the melt 8 and an epitaxial growth rate in between. Therefore, on the surface of the GaAs substrate 9, the difference in the contact time with the melt 8 between the slide-direction portions 9a, 9b, 9c is offset by the difference in the growth rate due to the temperature gradient. As a result, compared to the conventional
The difference in the epitaxially grown film thickness on the surface of the semiconductor substrate can be reduced.

In this embodiment, the bottom of the substrate receiving portion 5 has three segments 5a, 5 in the sliding direction A.
Although the two embedding materials 3 and 4 are embedded in the base material 2B so as to form b and 5c, the present invention is not limited to this. It is also possible to embed three or more embedding materials so that the thermal conductivity increases in order from the upper side to the lower side in the sliding direction. Also, by embedding many embedded materials,
The thermal conductivity of the bottom of the substrate receiving portion 5 may be gradually increased from the upper side to the lower side in the sliding direction, and may be changed substantially continuously. Further, the specific shape, size, and embedding position of each embedding material may be appropriately changed according to the shape and size of the base material 2B, the type of the melt 8, and the like.

Further, in this embodiment, the boat body 1 is slid with respect to the slider 2, but the slider 2 may be slid with respect to the boat body 1.

Further, by forming a plurality of segments having different thermal conductivities on the inner wall of the melt reservoir 6 of the boat body 1, convection in the melt 8 is accelerated, and the entire melt 8 is further shortened. It is also possible to achieve a uniform saturated state.

[0032]

As is clear from the above, the liquid of the present invention
According to the boat for phase epitaxial growth,
To reduce the difference in in-plane epitaxial growth film thickness
it can.

[Brief description of drawings]

FIG. 1 is a perspective view showing a main part of a slide boat according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a procedure of performing liquid phase epitaxial growth using the slide boat.

FIG. 3 is a diagram showing a set temperature program of a growth furnace for liquid phase epitaxial growth.

FIG. 4 is a diagram illustrating that a temperature gradient occurs at the bottom of the substrate receiving portion during the temperature lowering process when the slide boat is used.

FIG. 5 is a perspective view showing a substrate receiving portion of a conventional slide boat.

FIG. 6 is a diagram illustrating a procedure for performing liquid phase epitaxial growth using a conventional slide boat.

FIG. 7 is a diagram illustrating that the temperature of the bottom of the substrate receiving portion is uniformly reduced during the temperature lowering process when the conventional slide boat is used.

[Explanation of symbols]

1 boat body 2 slider 2a, 2b, 5a, 5b, 5c segment 3,4 Embedded material 5 Board receiving part 6 Melt reservoir 8 melt 9 GaAs substrate 10 sliding boats

Claims (3)

(57) [Claims] 1. A first member on which a melt reservoir for holding a melt containing a raw material for an epitaxial layer is formed, and a surface on which the melt reservoir on the side of the first member is opened is opposed to and slides. has a slide surface which can, and a second member in which the substrate receiving portion of the concave cross section for accommodating a semiconductor substrate in a specific area of the slide plane is formed, the epitaxial growth at the start
The first member is slid relative to the second member.
In the boat for liquid phase epitaxial growth, the bottom of the substrate receiving portion of the second member faces the melt reservoir of the first member in order at the start of epitaxial growth.
A boat for liquid phase epitaxial growth, characterized in that it is formed so that the thermal conductivity gradually increases from the upper part to the lower part of the bottom of the . 2. The boat for liquid phase epitaxial growth according to claim 1, wherein the bottom of the substrate receiving portion is the good one.
From Part to poor section, is divided into a plurality of segments of constant material, the thermal conductivity of the material constituting the respective segments, the poor portion from the segment of the well portion
A boat for liquid phase epitaxial growth, characterized in that the boat is set so as to grow in order up to the segment . 3. The liquid phase epitaxial growth according to claim 1.
In the long boat, the inner wall of the melt reservoir of the first member
Is divided into at least two segments made of a certain material, and the thermal conductivity of the materials forming the adjacent segments is different from each other.