JP2745819B2 - Vapor phase film growth equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vapor phase film growth apparatus for producing a growth film of a compound semiconductor crystal or the like, and more particularly to an apparatus having improved film thickness uniformity.
OCVD).

[0002]

2. Description of the Related Art In a vapor phase film growth apparatus, for example, MOCVD effective for forming a thin film, a growth furnace 20 is used as shown in FIG.
Into a vertical pancake mold, and a susceptor 25 that rotates at a low speed.
There is a type in which a source gas is blown vertically to the substrate 24 placed on the substrate to perform epitaxial growth. However, this vertical MO
In the CVD, the gas flow 22 is largely bent as shown. As a result, the gas flow boundary layer 23 on the substrate 24 does not become flat, and the distribution of the thickness of the epitaxial layer becomes concave.

Therefore, a method has been proposed in which epitaxial growth is performed while rotating a susceptor on which a substrate is mounted at a high speed (1000 to 1500 rpm) (for example, US EMC).
ORE TurboDisk (trade name)). In this method, the source gas flow blown vertically to the susceptor from the upper part is drawn to the center of the susceptor by the rotation of the susceptor, and then discharged in the outer peripheral direction, so that a uniform gas flow boundary layer is formed on the susceptor. It is stated that a uniform epitaxial layer grows on the substrate.

The reason why this uniform epitaxial layer is grown is based on the following principle. When the gas flow collides with the semi-infinite plane, the gas flow boundary layer becomes uniform. Rotating the susceptor at high speed has the same effect as if the gas flow collides with a semi-infinite plane. FIG. 3 shows the state of the gas flow 32 and the gas flow boundary layer 33 when idealized.

[0005]

However, in an actual high-speed rotation type vertical MOCVD, the exhaust port is provided below the growth furnace 20 as shown in FIG.
The raw material gas flow 42 toward the outer periphery of the susceptor 25 is bent and exhausted downward, and an "edge effect" occurs at the bent portion, and the gas flow boundary layer 43 around the susceptor 25 becomes thin. As a result, there is a problem that the epitaxial film thickness in the peripheral portion is increased and the uniformity is deteriorated, though not as much as in a normal low-speed rotation type growth furnace.

[0006] This problem is not limited to the vertical type, and is common to the horizontal type of the growth furnace as long as the source gas is blown vertically to the substrate. The same applies to a thick film as well as a thin film.

An object of the present invention is to solve the above-mentioned drawbacks of the prior art by forcibly creating a gas flow state similar to that of a semi-infinite plane, to achieve excellent uniformity of a grown film and high efficiency in raw material utilization. An object of the present invention is to provide a vapor phase film growth apparatus capable of growing a film.

[0008]

According to the present invention, as shown in FIG. 1 in the embodiment, when a raw material gas introduced into the growth furnace 10 is sucked and exhausted out of the growth furnace 10, the inside of the growth furnace 10 is removed. The present invention is applied to a vapor phase film growth apparatus for growing a film by vertically blowing a source gas onto a substrate 14 placed on the susceptor 15 while rotating the susceptor 15.

The exhaust gas rectification unit 3 guides the raw material gas blown vertically to the substrate 14 and sucked and exhausted to the outside in the radial direction of the susceptor 15 while controlling the exhaust gas flow rate to discharge the gas horizontally.
0, and the exhaust gas rectification unit 30 is provided along the peripheral wall of the growth furnace 10 on a substantially extended surface of the susceptor surface. Here, “substantially on the extension surface of the susceptor surface” means not only on the extension surface flush with the susceptor surface but also on the extension surface near the susceptor surface and parallel to the susceptor surface.

The exhaust rectification section 30 includes an orifice 16 for increasing the exhaust flow velocity, a net 17 for preventing backflow of exhaust substances such as particles, a valve 18 for adjusting an exhaust flow rate, and measuring and measuring the exhaust flow rate. It is preferable to comprise a valve control means 19 for controlling the valve according to the result.

Further, the exhaust gas rectification unit 30 may be provided on the entire circumference of the growth reactor wall. Economically desirable. In this case, the flow rate of exhaust gas flowing through each exhaust rectification unit 30 can be adjusted.

[0012]

When the gas flow bends downward in the radially outer space around the susceptor, the gas flow on the susceptor surface does not become parallel to the susceptor surface due to the influence of the gas flow. The flow has a velocity vector diagonally downward. Therefore, the gas flow boundary layer around the susceptor is thinner than the central part, and the formed film thickness is thicker than the central part. This is the so-called “edge effect”, which deteriorates the uniformity of the film thickness. The reason for this is that the gas flow is bent downward around the susceptor, and this is due to the exhaust port being below the susceptor.

Therefore, in order to solve this problem, the destination of the velocity vector is located radially outward parallel to the susceptor surface when viewed from the gas flow flowing outward from the center on the susceptor surface. do it.

That is, as shown in FIG. 1, if the exhaust rectification section 30 is provided on the growth reactor wall on the outer side of the extension of the susceptor 15, the gas flow 12 on the susceptor 15
That is, it flows outward from the center on the substrate 14 in parallel with this surface. Furthermore, if the exhaust flow rate is controlled, the uniformity of the raw material gas flow is ensured, and a uniform gas flow boundary layer 13 can be formed without being thick even in the peripheral portion.

By discharging the source gas flow on the substrate 14 to the outer periphery in parallel with the surface of the susceptor 15 as described above, the uniformity of the grown film is greatly improved without impairing the improvement of the source utilization efficiency which is a feature of the rotary type. Can be done.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 is a diagram showing the principle of the present embodiment applied to a vertical MOCVD. The vertical growth reactor 10 has a gas inlet 1
It is not a pancake type in which the shoulder 19 corresponding to the connecting portion with the connector 1 is lowered, but has a flat flat configuration in which the shoulder 19 is horizontal. In this growth furnace 10, a susceptor 15 is provided rotatable and its surface is horizontal. The raw material gas to be introduced into the growth furnace 10 and to be sucked and exhausted out of the furnace through the exhaust port 31 is first blown from the gas inlet 11 above the center of the susceptor 15 toward the center of the susceptor 15, and then High speed rotation of the susceptor 15 (for example, 1000 r
pm) to the center of the susceptor. The substrate 14 is placed on the susceptor 15 and rotates together with the susceptor 15.

An exhaust port 31 for discharging a source gas to the outside of the furnace is provided on the furnace wall of the growth furnace 10 outside the extension surface of the substrate mounting surface of the susceptor 15. In the middle of the exhaust port 3, there is provided an exhaust rectifying unit 30 that guides the raw material gas blown to the center of the susceptor to the outside in the radial direction of the susceptor 15 while controlling the exhaust flow rate and horizontally discharges the exhaust gas. The exhaust rectification unit 30 includes an orifice 16, a backflow prevention net 17, a valve 18, and a valve control unit 19 which are sequentially provided from upstream to downstream.
Consists of The orifice 16 is provided to increase the exhaust flow velocity, and the backflow prevention net 17 is provided to prevent backflow of particles and the like. The valve 18 is provided for adjusting the exhaust flow rate, and the valve control means 19 is provided for measuring the exhaust flow rate and controlling the valve 18 according to the measurement result.

The exhaust rectification unit 30 configured as described above is
In order to guide the exhaust gas flow 12 radially outward parallel to the susceptor rotation surface, the exhaust gas flow 12 is provided radially or over the entire circumference on the extension surface of the susceptor rotation surface.

The raw material gas, which hits perpendicularly to the center of the susceptor, flows horizontally on the substrate 14 toward the outside of the susceptor 15 in the radial direction, and is sucked as it is into the exhaust rectification unit 30 which is horizontal and outside in the radial direction. Exhausted to the outside.
If the exhaust flow rate discharged from the exhaust port 31 is large, the valve opening degree of the valve 18 controlled by the valve control means 19 is reduced and decreased, and conversely, if the exhaust flow rate is small, the valve control means 1 is reduced.
The valve opening of the valve 18 controlled by the valve 9 is increased and increased. In this process, the raw material decomposed on the heated substrate 14 diffuses through the gas flow boundary layer 13 and deposits on the substrate 14 to grow the epitaxial film.

Next, a specific example of the above vertical MOCVD will be described with reference to FIGS.

A heater 5 is provided on the lower surface of the disc-shaped susceptor 51.
2, the temperature of the susceptor 51 is set to 450 ° C. to 800 ° C. by the heater 52. Φ on this susceptor 51
A circular tray 58 in which three 4-inch GaAs substrates 59 are placed at rotationally symmetric positions is placed, and rotates together with the susceptor 51. Here, the susceptor 51 on which the toilet 58 was mounted was rotated at a rotation speed of 500 rpm to 2000 rpm. The substrate 59 and the tray 58 are flush (FIG. 5A).
See). The raw materials used were trimethylgallium, trimethylaluminum, trimethylindium, arsine, and disilane. Hydrogen is used as a carrier gas, and the raw material is mixed with the above raw material to obtain a raw material gas.
Introduced inside. The growth furnace 60 has a ceiling inner wall formed of a flat cylindrical body. The introduced source gas is exhausted from the plurality of exhaust pipes 55 provided in the growth furnace 60 to the outside of the furnace. The exhaust pipe 55 is provided radially at a position rotationally symmetric with respect to the rotation center axis 63 of the susceptor 51 on the growth furnace wall on the extension surface of the tray 58 surface. The illustrated example shows a case where eight are provided. The pressure inside the growth furnace was set at 20 torr to atmospheric pressure in order to suck and exhaust the source gas outside the furnace.

The location of the exhaust pipe 55 is more precisely parallel to the surface of the substrate 59 placed on the tray 58 on the susceptor 51 and slightly above the circle drawn on the furnace wall 64 intersecting the extension surface thereof. Provided. An exhaust rectifying section 61 is provided on the exhaust path of the exhaust pipe 55, and includes an orifice 53 provided from the upstream side to the downstream side, and a backflow prevention net 54.
, A needle valve 68 and a flow controller 69.

An orifice 53 is formed to guide the raw material gas blown vertically to the substrate 59 outward in the horizontal direction and discharge the gas to the exhaust pipe 55. The orifice 53 is formed by narrowing the gas flow path in order to increase the exhaust flow velocity. At the outlet side of the orifice 53, there is provided a net 54 for preventing backflow of dust and the like and uniformly exhausting the air radially. The net 54 may be provided on the inlet side of the orifice 53.

In the exhaust pipe 55, a needle valve 68 for adjusting the exhaust flow rate is provided on the upstream side, and the exhaust flow rate is monitored on the downstream side, and the valve body of the needle valve 68 is controlled in accordance with the monitoring result. Flow controller 69 for adjusting the flow rate
And are interposed. Thus, the flow rate of exhaust gas exhausted from each exhaust pipe 55 can be adjusted individually.
Due to the presence of the orifice 53 and the mesh 54, the gas flow flows parallel to the substrate 59, and the orifice 53 and the mesh 54
Is exhausted outside the growth furnace after passing through. Further, the presence of the needle valve 68 and the flow controller 69 makes it possible to equalize the exhaust flow rate exhausted to the outside of the growth furnace, and to make the gas flow boundary layer on the substrate 59 uniform. Note that the exhaust gas flow is
It is important to keep the inner wall of the ceiling of the growth furnace 60 horizontal in order to make the flow parallel to

As described above, the exhaust gas rectification section 61 allows the substrate 59
The thickness of the upper gas flow boundary layer is uniform, resulting in a uniform epitaxial film thickness. In addition, the presence of the net 54 for preventing the backflow prevents the particles from rising, and the exhaust is performed radially and uniformly on the susceptor surface from the susceptor to the outside, so that an epitaxial crystal having no surface defects can be obtained. Needle valve 68, flow controller 6
9, it is possible to adjust the uniformity of the susceptor plane exhaust flow, that is, the gas flow.
Can be controlled. Further, since the exhaust rectification section 65 is provided, convection does not occur in the space above the substrate 59, and the source gas is switched in the furnace at high speed. Therefore, a heterojunction epitaxial crystal having a steep interface can be grown. Next, a specific example will be described.
As shown in FIG. 7, an epitaxial crystal having an n-type GaAlAs / GaAs selective doping structure as shown in FIG. 7 was grown at 0.degree. Is ± 1% or less,
The variation of three simultaneously grown φ4 inch wafers is ± 2
% Or less.

The variation in carrier concentration of n-type GaAlAs was ± 2% or less, and the variation in Al mixed crystal ratio was ± 0.3% or less. The sheet carrier density is 1.2 × 10 12 cm
The mobility was 2 ± 1% and the mobility was very uniform at 6200 ± 2%.

In the growth of InGaAs, the thickness variation was equivalent to that of GaAs, and the carrier concentration and the uniformity of the mixed crystal ratio were good.

In this embodiment, the susceptor rotation speed is desirably 500 rpm or more in order to effectively increase the utilization efficiency of the raw material. However, the utilization efficiency of the raw material is not so desired, and a very uniform epitaxial film can be stably grown. If the purpose of the present invention is only to make the susceptor rotation speed 500 rpm or less, or 2000 rpm
It is basically effective even at pm or more.

Further, in the above embodiment, an example in which the growth furnace is arranged vertically has been described. However, even if the growth furnace is arranged horizontally, the present invention can be applied as long as the raw material can be sprayed vertically on the substrate. It is possible. Further, it is needless to say that the present invention can be applied not only to a thin film but also to a thick film.

In this embodiment, the exhaust pipe is provided on the substantially extended surface of the susceptor surface. However, only the exhaust rectification portion is provided on the substantially extended surface of the susceptor surface. How the exhaust gas is routed is not critical in the present invention, so if a path to the exhaust pipe is provided, the exhaust pipe is conventionally provided below the growth furnace. Is also good.

[0032]

According to the present invention, since the exhaust gas rectifying section is provided to discharge the raw material gas blown vertically to the substrate horizontally while controlling the exhaust flow rate, the gas flow state similar to that of the semi-infinite plane is obtained. Forcibly, it is possible to grow a film having excellent uniformity.

In particular, by setting the rotation speed of the susceptor to 100 rpm or more, a film having high raw material use efficiency can be grown.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a relationship between a gas flow and an exhaust method in a vertical growth furnace, and is a principle configuration diagram of the present embodiment.

FIG. 2 is an explanatory diagram showing a relationship between a gas flow and an exhaust method in a vertical growth furnace, and is a configuration diagram of a general example.

FIG. 3 is an explanatory diagram showing a relationship between a gas flow and an exhaust method in a vertical growth furnace, and is a configuration diagram of an ideal example.

FIG. 4 is an explanatory diagram showing a relationship between a gas flow and an exhaust method in a vertical growth furnace, and is a configuration diagram of a conventional example.

FIG. 5 is a configuration diagram showing an embodiment of a vapor phase film growth apparatus of the present invention.

FIG. 6 is a sectional view showing an embodiment of the vapor phase film growth apparatus of the present invention.

FIG. 7 shows GaAlAs used for evaluating the growth characteristics of the present example.
FIG. 5 is an epitaxial crystal cross-sectional view of a / GaAs selective doping structure.

[Explanation of symbols]

 Reference Signs List 9 rotation center axis of susceptor 10 growth furnace 11 gas inlet 12 gas flow 13 gas flow boundary layer 14 substrate 15 susceptor 15 orifice 17 backflow prevention network 18 valve 19 valve control means 30 exhaust rectification unit 50 gas inlet 51 susceptor 52 heater 53 Orifice 54 Backflow prevention net 55 Exhaust pipe 58 Tray 59 Substrate 60 Growth furnace 61 Exhaust rectification unit 63 Susceptor rotation center axis 68 Needle valve 69 Flow controller

Claims (3)

(57) [Claims] 1. A vapor-phase film growth apparatus for growing a film by vertically blowing a source gas onto a substrate mounted on a rotating susceptor when sucking and exhausting a source gas introduced into the growth furnace out of the growth furnace, An exhaust rectification unit that guides a source gas, which is blown vertically to a substrate and sucked and exhausted, onto a growth furnace wall on a substantially extended surface of the susceptor surface, while controlling the exhaust flow rate, to the outside in the radial direction of the susceptor to discharge horizontally. An apparatus for growing a vapor phase film, comprising: 2. An exhaust rectification unit comprising: an orifice for increasing exhaust flow velocity; a net for preventing backflow of particles; a valve for adjusting exhaust flow rate; and measuring the exhaust flow rate and controlling the valve in accordance with the measurement result. 2. The vapor phase film growing apparatus according to claim 1, further comprising: 3. The vapor phase film growth apparatus according to claim 1, wherein the exhaust rectification unit is provided radially at a position rotationally symmetric with respect to a rotation center axis of the susceptor.