JP2006318957A - Method of detecting eccentricity in susceptor of vapor phase deposition apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of detecting eccentricity in a susceptor in rotation in a vapor phase deposition apparatus having the susceptor for arranging a substrate at a prescribed position. <P>SOLUTION: The periphery of a rotating shaft 8 in the susceptor 1 is surrounded for providing a conductive eccentricity detection member 5, and it is detected whether the susceptor 1 becomes eccentric according to the presence or absence of electrical continuity caused by allowing the conductive eccentricity detection member 5 to come into contact with the rotating shaft 8 of the susceptor 1. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for detecting susceptor eccentricity in an apparatus in which a substrate is placed on a susceptor installed in a reaction furnace and a single crystal, polycrystalline, or amorphous thin film is vapor-phase grown on each substrate.

  Laminated structures of compound semiconductor epitaxial crystals such as GaAs, InGaP, AlGaAs, and AlGaInP are widely used as electronic devices such as HEMT (High Electron Mobility Transistor) and HBT (Heterojunction Bipolar Transistor), and light emitting devices such as LEDs and lasers. . In general, these compound semiconductor electron / light-emitting devices are generally obtained by sequentially depositing a compound semiconductor crystal having a desired composition and thickness on a substrate such as GaAs using a crystal growth method such as MOVPE (metal organic vapor phase epitaxy). Epitaxially grow.

  In vapor phase epitaxy, a type of epitaxial growth method that forms a thin film on a substrate, a high quality crystal with uniform film thickness distribution, specific resistance distribution, etc. is grown. There is a method of growing while rotating the susceptor on which the substrate is arranged so as to be uniform. Among them, a method of fixing a substrate in a crystal growth apparatus (reaction furnace) so that the crystal growth surface faces downward (for example, refer to Patent Document 1) is called a face-down type. The face-down type is excellent in creating a fine layered structure because extra convection is unlikely to occur when supplying the source gas to the substrate, and surface deposits also occur because deposits accumulated in the furnace rarely fall on the substrate surface. It has the advantage of being difficult.

  FIG. 3 is a longitudinal sectional view showing a part of a conventional face-down type vapor phase growth apparatus (reactor).

  A raw material gas supply port (inlet) 21 is provided on one side and a gas is provided on the opposite side in order to form a flow channel 20 serving as a gas flow path for raw material gas or the like in an intermediate portion in the vertical direction in the vapor phase growth apparatus (reactor). A horizontal reaction tube 2 having an exhaust port (outlet) 22 is disposed. In the upper wall of the flow channel 20, that is, in the upper wall of the horizontal reaction tube 2, a flow channel opening 9 is provided at the center, and a plurality of semiconductor substrates 4 are placed in the flow channel opening 9. The holding susceptor 1 is rotatably fitted.

  The susceptor 1 has a disk shape, and a plurality of circular openings 6 are equally provided on the same circle in the disk surface, and each of the openings 6 is for crystal growth that is an object of epitaxial growth. A semiconductor substrate (wafer) 4 as a substrate is accommodated and disposed with its surface (crystal growth surface) facing downward. In order to obtain a structure in which the semiconductor substrate 4 is placed and supported in the opening 6, a substrate support portion made of a metal claw 7 partially projecting in the center direction of the opening 6 is provided on the peripheral surface of the lower surface of the opening 6. The semiconductor substrate 4 is held on the lower surface of the opening 6 with the outer peripheral portion supported by the substrate support portion. In the opening 6, a soaking plate is provided on the semiconductor substrate 4 as necessary.

  In the case of epitaxial growth by the face-down type MOVPE method, the susceptor 1 that supports the semiconductor substrate 4 is rotated by a motor while rotating the rotating shaft 8 with a motor (not shown) through the susceptor 1. 4 is heated, and a source gas is allowed to flow in parallel with the susceptor 1 to grow an epitaxial film having a desired structure on the semiconductor substrate (wafer) 4.

In the above structure, the susceptor 1 is made of graphite. The reaction tube 2 forming the flow channel 20 is a rectangular tube that is formed of quartz glass and is flat in the axial direction. The source gas reaches the susceptor 1 through the flow channel 20 and is thermally decomposed under the susceptor heated to a high temperature by the heater. The decomposed gas molecules reach the semiconductor substrate 4 to form a film. . Here, in order to prevent the outflow of the source gas from the inside of the flow channel 20 and the inflow of impurities and particles to the outside of the flow channel 20, the gap 3 generated in the fitting portion of the susceptor 1 and the reaction tube 2 is as much as possible. It is better to make it narrower.
Japanese Patent Laid-Open No. 10-25191

  However, since the rotation mechanism including the susceptor is composed of a plurality of parts, it is difficult to ensure accuracy in the assembled state, and eccentricity is likely to occur during rotation at high temperatures in vapor phase growth.

  When the eccentricity exceeds the allowable range, there is a problem that the film thickness distribution and the specific resistance distribution cause a characteristic difference within the same plane of the wafer or between wafers. Further, when the eccentricity is remarkable, there is a problem that the susceptor and the flow channel are rubbed, and the graphite powder generated thereby is taken into the thin film growing on the substrate, resulting in a deterioration in quality.

  When such a situation occurs, it is necessary to replace the susceptor and the flow channel and to adjust the position of the parts constituting the rotation mechanism. However, it is difficult to quantitatively determine the eccentricity during growth, and as a result, there is a problem in that a low-quality thin film is continuously produced.

  Accordingly, an object of the present invention is to solve the above problems and provide a method for detecting the eccentricity of a susceptor during rotation in a vapor phase growth apparatus having a susceptor for placing a substrate at a predetermined position. It is to prevent the drop of the distillation.

  In order to achieve the above object, the present invention is configured as follows.

  The susceptor eccentricity detection method for a vapor phase growth apparatus according to the first aspect of the present invention is a susceptor in which an opening is provided at a predetermined position in a wall of a flow channel serving as a gas flow path for a raw material gas and the substrate is held in the opening. In a vapor phase growth apparatus for growing a semiconductor thin film on a substrate while rotating the susceptor within an opening by a rotation shaft fixed to the susceptor, a conductive eccentricity detection member surrounding the rotation shaft of the susceptor And detecting whether or not the susceptor is eccentric based on the presence or absence of electrical continuity due to contact between the conductive eccentricity detecting member and the rotating shaft of the susceptor.

  The conductive eccentricity detection member preferably comprises a conductive ring surrounding the periphery of the rotation axis of the susceptor.

  According to a second aspect of the present invention, in the susceptor eccentricity detection method of the vapor phase growth apparatus according to the first aspect, the amount of eccentricity of the rotation axis of the susceptor during rotation depends on the presence or absence of contact between the rotation axis of the susceptor and the conductive eccentricity detection member. It is characterized in that it is detected whether the range of the allowable film thickness distribution or specific resistance distribution is exceeded.

  According to a third aspect of the present invention, in the susceptor eccentricity detection method of the vapor phase growth apparatus according to the first aspect, the susceptor is positioned at the opening of the flow channel during rotation depending on whether or not the rotating shaft of the susceptor is in contact with the conductive eccentricity detection member. It is characterized by detecting whether rubbing has occurred.

<Key points of the invention>
The main point of the present invention is that an eccentricity detection member made of a conductive material such as graphite is installed in the vicinity of the rotating shaft portion of the susceptor, so that an electric circuit is configured between the eccentricity detection member and the susceptor. The continuity can be detected, thereby detecting whether the eccentricity of the susceptor exceeds an allowable range.

  FIG. 1 shows a state in which the susceptor 1 is set in the opening 9 of the flow channel. According to the present invention, an electrical circuit is configured by the susceptor 1, the reaction tube 2, and the eccentricity detection member 5 made of a conductive material such as graphite. The susceptor 1 is made of graphite including the rotating shaft 8.

  FIG. 2 is a cross-sectional view showing a state in which the susceptor 1 is eccentric. The gaps 3a and 3b between the susceptor 1 and the opening 9 of the flow channel are different. Here, if both the susceptor 1 and the eccentricity detection member 5 are connected to the power source through the current detection circuit 10 outside, the eccentricity detection member 5 is in an eccentric state in the susceptor 1 as shown in FIG. When the susceptor 1 comes into contact with the susceptor 1 and an electrical closed circuit is formed, and this is used as a detection signal, it is possible to determine whether the eccentricity of the susceptor 1 exceeds an allowable range.

  According to the present invention, the following excellent effects can be obtained.

  According to the first aspect of the present invention, it is possible to detect whether or not the susceptor is eccentric during rotation based on the presence or absence of electrical continuity due to contact between the conductive eccentricity detecting member and the rotating shaft of the susceptor.

  Further, according to the invention described in claim 2, by properly setting the interval until the rotating shaft of the susceptor and the conductive eccentricity detecting member come into contact, the amount of eccentricity of the rotating shaft of the susceptor during rotation is When the allowable film thickness distribution or specific resistance distribution range is exceeded, the detection to that effect can be notified. Therefore, measures can be taken early, avoiding the problem of continuously producing low-quality thin films, and making the film thickness distribution and specific resistance distribution uniform within the same wafer surface or between wafers. Can be achieved.

  Similarly, according to the third aspect of the present invention, the susceptor rubs against the opening of the flow channel during rotation by appropriately setting the interval until the rotating shaft of the susceptor contacts the conductive eccentricity detecting member. At that time, the detection of that fact can be notified. Therefore, compared with the conventional method of checking the presence or absence of rubbing from the viewing window, an abnormality that the susceptor is rubbing against the opening of the flow channel can be detected immediately, and measures can be taken at an early stage. Therefore, according to the present invention, the problem of continuously producing a conventional low quality thin film can be avoided.

  Hereinafter, the present invention will be described based on the illustrated embodiments.

  FIG. 1 shows a face-down type vapor phase epitaxial growth apparatus according to this embodiment. This growth apparatus has basically the same configuration as that shown in FIG. 3, and a circular opening 9 provided in the upper wall of the flow channel 20 serving as a gas flow path for the raw material gas, that is, the upper wall of the horizontal reaction tube 2. In addition, a circular susceptor 1 holding a plurality of semiconductor substrates 4 is rotatably fitted to function as a part of the upper wall of the horizontal reaction tube 2 through which the source gas flows. The susceptor 1 is made of graphite including the rotating shaft 8.

  In the plane of the circular susceptor 1, a plurality of openings 6 having substantially the same shape as that of the semiconductor substrate 4 to be subjected to vapor phase epitaxial growth are provided in the circumferential direction along one circumference concentric with the susceptor 1. In this opening 6, the semiconductor substrate 4 is accommodated with its crystal growth surface facing downward, and is supported by a substrate support portion comprising a lower claw 7.

  When epitaxial growth is performed by the MOVPE method, the susceptor 1 that supports the semiconductor substrate 4 is heated by the upper heater (not shown) through the susceptor 1 while rotating the rotating shaft 8 with a motor. In addition, a material gas is allowed to flow in parallel with the susceptor 1 so that a thin film such as a semiconductor single crystal, polycrystal, or amorphous is vapor-phase grown on the semiconductor substrate (wafer) 4.

  However, unlike the conventional growth apparatus, a conductive eccentricity detection member 5 is provided surrounding the rotating shaft 8 of the susceptor 1 made of graphite. The conductive eccentricity detection member 5 is specifically formed of a conductive graphite ring surrounding the periphery of the rotating shaft 8 of the susceptor 1. Then, when the rotating shaft 8 of the susceptor 1 is eccentric, it comes into contact with the conductive ring (eccentricity detecting member 5) so that the rotating shaft 8 of the susceptor 1 and the eccentricity detecting member 5 are electrically connected. It is configured.

  If both the eccentricity detecting member 5 and the susceptor 1 are externally connected to a power source, an electrical closed circuit is formed in the state where the eccentricity shown in FIG. 2 occurs. That is, it is possible to determine whether or not the susceptor eccentricity during the vapor phase growth exceeds the allowable range by detecting that the current is flowing as the eccentricity occurs.

  FIG. 1 is a diagram showing a state where the rotating shaft 8 of the susceptor 1 and the conductive eccentricity detecting member 5 are non-conductive (OFF), and FIG. 2 is a diagram showing a state where both are in contact and conductive (ON). The rotating shaft 8 of the susceptor 1 and the conductive eccentricity detection member 5 are each connected to an external power source via a current detection circuit 10. For this reason, when both the rotating shaft 8 and the eccentricity detection member 5 are in contact and rubbed as shown in FIG. 2, an electrical closed circuit (electric circuit) is formed. That is, the current is turned on and current flows. Therefore, the eccentricity of the rotating shaft 8 of the susceptor 1 can be detected by detecting this with the current detection circuit 10 and outputting it as a detection signal, and the amount of eccentricity when the response is made is set in advance. Thus, it is possible to indirectly detect the excess of the predetermined eccentricity or the friction between the susceptor 1 and the flow channel opening 9. For example, when the amount of eccentricity of the rotation axis of the susceptor exceeds the range of allowable film thickness distribution or specific resistance distribution (tolerance range of eccentricity), the rotation axis of the susceptor comes into contact with the conductive eccentricity detection member. By setting the (interval), it is possible to prevent inconvenience that production is stopped when the abnormality is detected, and a large number of wafers whose film thickness distribution or specific resistance distribution exceeds an allowable range are produced.

  Next, in order to confirm the effect of the present invention, the above susceptor eccentricity detection method was applied to actual vapor phase growth.

  After the substrate is set on the susceptor and the vapor phase growth is performed, one badge is used until the substrate is taken out. The vapor phase growth is repeated for several badges. When a certain badge is used, current is passed between the susceptor 1 and the eccentricity detection member 5. confirmed. When the surface state of the substrate taken out was confirmed, it was extremely worse than the previous badge. Further, when the characteristics of all the wafers (substrates) of the badge were evaluated and compared, it was confirmed that there was a characteristic difference between the wafers. For this reason, when the production was resumed by adjusting the eccentricity of the susceptor as much as possible, the surface condition was improved.

  From the above, it has been found that the eccentricity of the susceptor 1 during the vapor phase growth can be detected by energization between the rotating shaft 8 of the susceptor 1 and the eccentricity detection member 5 and is effective in preventing the yield reduction.

  In the above embodiment, the face-down type in which the source gas flows in the diameter direction of the susceptor has been described as an example, but the present invention can also be applied to the face-down type in which the source gas flows in the radial direction from the center of the susceptor 1. it can.

It is the figure which showed the non-conduction state of the rotating shaft of a susceptor and the eccentricity detection member in the susceptor eccentricity detection method of this invention. It is the figure which showed the conduction | electrical_connection state of the rotating shaft of a susceptor and the eccentricity detection member in the susceptor eccentricity detection method of this invention. It is sectional drawing which showed the vapor phase growth apparatus of the prior art.

Explanation of symbols

1 susceptor 2 reaction tube 3 gap 3a gap 3b gap 4 semiconductor substrate (wafer)
DESCRIPTION OF SYMBOLS 5 Eccentricity detection member 6 Opening 7 Claw 8 Rotating shaft 9 Opening part 10 Current detection circuit 20 Flow channel 21 Source gas supply port 22 Gas exhaust port

Claims (3)

An opening is provided at a predetermined position in the wall of the flow channel that serves as a gas flow path for source gas, etc., and a susceptor holding the substrate is fitted into this opening, and this susceptor is rotated in the opening by a fixed rotating shaft. While in a vapor phase growth apparatus for growing a semiconductor thin film on a substrate,
A conductive eccentricity detecting member is provided surrounding the rotating shaft of the susceptor, and whether or not the susceptor is eccentric is determined by the presence or absence of electrical conduction due to contact between the conductive eccentricity detecting member and the rotating shaft of the susceptor. A method of detecting a susceptor eccentricity of a vapor phase growth apparatus. In the susceptor eccentricity detection method of the vapor phase growth apparatus according to claim 1,
Detecting whether or not the amount of eccentricity of the rotating shaft of the susceptor during rotation exceeds the range of allowable film thickness distribution or specific resistance distribution based on the presence or absence of contact between the rotating shaft of the susceptor and the conductive eccentricity detecting member. A susceptor eccentricity detection method for a vapor phase growth apparatus. In the susceptor eccentricity detection method of the vapor phase growth apparatus according to claim 1,
A susceptor eccentricity detection method for a vapor phase growth apparatus, characterized by detecting whether or not the susceptor rubs against an opening of a flow channel during rotation based on the presence or absence of contact between a rotating shaft of the susceptor and a conductive eccentricity detection member.

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