A method and device for measuring the rotation speed of a satellite disk of a MOCVD planetary tray

Abstract

The present invention discloses a method and device for measuring the rotation speed of a satellite disk of a MOCVD planetary tray. A laser measuring probe on the MOCVD device emits a laser beam. The laser irradiates the planetary tray of the MOCVD device. As the planetary tray rotates, the laser also irradiates the satellite tray and the wafer on the satellite tray. The reflected laser is converted into an electrical signal after being split. The electrical signal is sampled at a fixed frequency f within the time of two trigger pulse signals to obtain the angle Δα that the planetary tray rotates each time it is sampled. According to the angle Δα, the rotation angle values ​​ф0 and ф1 when the edge of the wafer enters and is at the measuring point are calculated. The rotation speed of the satellite tray can be obtained by calculating the changes in the angles ф0 and ф1. The present invention is applicable to the case where the rotation speed of the satellite tray is greater than the rotation speed of the planetary tray and the number of wafers on the satellite tray is greater than or equal to 2.

Description

Technical Field

[0001] The invention relates to the technical field of MOCVD equipment, in particular to a method and a device for measuring the rotation speed of a satellite disk of a MOCVD planetary tray. Background Art

[0002] Metal organic chemical vapor deposition (MOCVD) equipment is the main production equipment for LED and compound semiconductors. In the equipment cavity, there is a rotating large graphite disk tray - planetary disk, on which there are multiple small graphite disks - satellite disks that can rotate on their own; the large graphite disk is driven by a motor, the speed is controllable, and a pulse signal can be given for synchronization and speed measurement; the satellite disk is blown by airflow to rotate, and the speed is adjusted by adjusting the airflow. Multiple wafer substrates can be placed on the satellite disk. The cavity heats the wafer to a certain temperature, passes organic chemical gas into it, produces a chemical reaction, and deposits on the surface of the wafer. By controlling the composition and doping of the gas, the thin film layer required for semiconductor devices is grown.

[0003] The temperature consistency of the wafer during the process is very important to the production yield, and the rotation speed of the satellite disk driven by the airflow will affect its own temperature and the temperature of the wafer. Although the rotation speed of the satellite disk can be adjusted by the airflow, before the present invention, it was impossible to accurately know the rotation speed of the satellite disk. Summary of the invention

[0004] The object of the present invention is to provide a method and device for measuring the rotation speed of a satellite disk of a MOCVD planetary tray, so as to solve the problems raised in the above background technology.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] A method for measuring the rotation speed of a satellite disk of a MOCVD planetary tray, the method comprising the following steps:

[0007] A laser beam is emitted through a laser measuring probe on the MOCVD device;

[0008] The laser irradiates the planetary tray of the MOCVD equipment, and as the planetary tray rotates, it also irradiates the satellite dish and the wafer on the satellite dish;

[0009] The reflected laser is converted into an electrical signal after being split;

[0010] The electrical signal is sampled at a fixed frequency f within the time of two trigger pulse signals, and the angle Δα rotated by the planetary tray is obtained each time the sampling is performed;

[0011] According to the angle Δα, when the edge of the wafer enters the measuring point, the rotation angle value ф0 at this moment is calculated;

[0012] According to the angle Δα, when the edge of the wafer leaves the measurement point, the rotation angle value ф1 at this moment is calculated;

[0013] The rotation speed of the satellite dish can be obtained by calculating the changes in the ф0 and ф1 angles.

[0014] Preferably, the laser measurement probe is installed on the cavity observation window of the MOCVD device. The MOCVD device can provide a signal of the rotation of the planetary tray, and one rotation is a trigger pulse signal.

[0015] Preferably, the satellite dish and the planetary tray are made of the same material and do not reflect laser light, while the wafer reflects laser light.

[0016] Preferably, the reflected laser is irradiated onto the detector through the beam splitter and converted into an electrical signal, and the electrical signal is collected by a multi-channel synchronous data acquisition card.

[0017] Preferably, sampling is performed at a fixed frequency f, and a total of L lines of data are sampled within the time of 2 trigger pulses. The angle Δα rotated by the planetary tray each time the planetary tray is sampled is 360 / L; the number of sampling times between the sampling point when the edge of the wafer enters the measurement point and the sampling point when the edge of the wafer leaves the measurement point and the sampling point at the center of the satellite tray correspond to L0 and L1 respectively, which can be counted from the sampling data.

[0018] Preferably, the rotation angle value ф0=γ0-β0, where: γ0=arcsin[(dv*sinα0) / a], ], according to the calculation formula of any triangle, a= α0)½; the rotation angle value ф1=γ1-β1, where: a= α1)½, γ1=arcsin[(dv*sinα1) / a], ] , α1=L1*Δα=360*L1 / L, b=wafer radius Rwafer, where dv, ds and dw are known quantities, representing the distance from the measuring point to the center of the planetary tray, the distance from the center of the satellite tray to the center of the planetary tray and the distance from the center of the wafer to the center of the satellite tray, respectively. The α angle is the angle between the line from the measuring point to the center of the planetary tray and the line from the center of the satellite tray to the center of the planetary tray. The β angle is the angle between the line from the center of the satellite tray to the measuring point and the line from the center of the wafer to the center of the satellite tray. The γ angle is the angle between the line from the measuring point to the center of the satellite tray and the line from the center of the satellite tray to the center of the planetary tray. A is the distance from the center of the satellite tray to the measuring point. B is the distance from the center of the wafer to the measuring point. The ф angle is the angle between the line from the center of the wafer to the center of the satellite tray and the line from the center of the satellite tray to the center of the planetary tray.

[0019] Preferably, the rotation angle of each sampling is Δф= , then the satellite dish rotation speed m, the number of revolutions per minute = the number of sampling times per minute is f×60 seconds multiplied by the angle rotated per sampling divided by 360 degrees, then m= f×60×Δф / 360=f×Δф / 6.

[0020] To achieve the above object, the present invention also provides the following technical solutions:

[0021] A device for measuring the rotation speed of a satellite disk of a MOCVD planetary tray, comprising:

[0022] Laser measurement probe, installed on the cavity observation window of MOCVD equipment, used to emit laser beam to the rotating planetary tray, satellite dish and wafer;

[0023] A beam splitter is used to split the reflected laser beam and illuminate the detector to convert the optical signal into an electrical signal;

[0024] Multi-channel synchronous data acquisition card, used to synchronously read the electrical detector and trigger pulse signal, and send it to the computer for analysis and calculation to obtain the rotation speed of the satellite dish;

[0025] The planetary tray is installed on the MOCVD equipment;

[0026] The satellite dish is mounted on a planetary tray;

[0027] The wafer is mounted on a satellite dish.

[0028] Preferably, the laser measurement probe is mainly composed of a collimated laser and a detector, and the detector is a photoelectric detector or a displacement detector.

[0029] Preferably, the collimating laser, the beam splitter and the detector are in the same optical path.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] The present invention emits a laser beam to a rotating tray through a measuring probe composed of a collimated laser and a photodetector, collects the reflected laser intensity signal, and distinguishes the edge of the satellite dish and the edge of the wafer on the satellite dish through a special algorithm, and calculates the rotation speed of the satellite dish by calculating the angle between the center of the wafer to the center of the satellite dish and the center of the satellite dish to the center of the large dish.

[0032] The method of the present invention is applicable to the situation where the rotation speed of the satellite disk is greater than the rotation speed of the planetary tray and the number of wafers on the satellite disk is greater than or equal to 2. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a schematic diagram of the device of the present invention.

[0034] Figure 2 A schematic diagram of a circle of signal data collected by the synchronous data acquisition card of the present invention.

[0035] Figure 3 This is a schematic diagram of the moment when the satellite dish of the present invention enters the measurement point.

[0036] Figure 4 This is a schematic diagram of the moment when the wafer of the present invention enters the measurement point.

[0037] Figure 5 It is a schematic diagram of the measurement point timing of the wafer of the present invention.

[0038] In the figure: 1- laser measurement probe; 2- collimated laser; 3- beam splitter; 4- photoelectric detector; 5- multi-channel synchronous acquisition card; 6- planetary tray; 7- satellite dish; 8- wafer; 9- trigger pulse signal. DETAILED DESCRIPTION

[0039] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0040] See also Figures 1 to 5 , the present invention provides a technical solution:

[0041] like Figure 1 As shown, a laser measuring probe 1 is installed on the cavity observation window of the MOCVD device, and a laser beam is emitted to irradiate the planetary tray 6 of the MOCVD device. The reflected laser is irradiated to the photoelectric detector 4 or the displacement detector through the beam splitter 3. The signal output by the detector is transmitted to the multi-channel synchronous data acquisition card 5 in the computer through the cable, and the measurement software is run in the computer.

[0042] The MOCVD device can provide a signal for the rotation of the planetary tray 6, one pulse per revolution, which is connected to a multi-channel synchronous data acquisition card 5 in a computer via a cable. The software in the computer can synchronously read the photodetector 4 and the trigger pulse signal 9.

[0043] The computer can calculate the rotation speed of the large plate (planetary tray 6) by calculating the interval of the trigger pulse signal 9.

[0044] The laser irradiates the planetary tray 6, and as the tray rotates, it also irradiates the satellite dish 7, the wafer 8 on the satellite dish 7, and the gap between the wafers 8 on the satellite dish 7;

[0045] The satellite disk 7 and the planetary tray are made of graphite material, which hardly reflects the laser, and the detected intensity signal is close to 0. The wafer 8 on the satellite disk 7 reflects the laser beam, and the reflection intensity will change with the process change; but it is much higher than the graphite disk; therefore, by analyzing the received signal intensity through the high-sensitivity photoelectric detector 4 or the displacement detector with intensity measurement, it can be distinguished whether the laser is irradiated on the wafer 8, the satellite disk 7 or the planetary tray 6.

[0046] The signal collected by the computer through the multi-channel synchronous acquisition card 5 is as follows Figure 2 The software intercepts the data between the two trigger pulse signals 9 and obtains the measurement data of one rotation of the planetary tray 6.

[0047] The number and arrangement of satellite disks 7 on the planetary tray 6 are known; the rotation of the planetary tray 6 is driven by a motor; there are two ways to obtain the trigger pulse signal 9, one is to obtain it from the motor driver, and the other is to install a photoelectric switch on the motor shaft. In either case, the phase relationship between the trigger pulse signal 9 and the satellite disk 7 is fixed. Therefore, according to the arrangement data of the satellite disk 7 and the phase relationship of the trigger pulse signal 9, the collected signals can be used to distinguish the signals of each satellite disk 7, such as Figure 2 As shown in the A, B, C, D, E, and F areas.

[0048] Based on the signal strength, the software can distinguish the edge of each wafer 8.

[0049] The algorithm is as follows:

[0050] 1. If Figure 3 As shown, the planetary tray 6 is in revolution and the satellite dish 7 is in rotation. The wafer 8 on the satellite dish 7 is fixed relative to the satellite dish 7, so the angle ф between the line from the center of the wafer 8 to the center of the satellite dish 7 and the line from the center of the satellite dish 7 to the center of the planetary tray 6 is the rotation angle that has nothing to do with the revolution. The rotation speed of the satellite dish 7 can be calculated by calculating the change of the angle ф.

[0051] like Figure 3 As shown in the figure, the observation window and the measuring probe are fixed.

[0052] 1) dv, the distance from the measuring point to the center of the planetary tray 6, a known quantity;

[0053] 2) ds, the distance from the center of the satellite dish to the center of the planetary tray 6, a known quantity;

[0054] 3) dw, the distance from the center of the wafer to the center of the satellite dish, a known quantity;

[0055] 4) Angle α, the angle between the line connecting the measuring point and the center of the planetary tray 6 and the line connecting the center of the satellite tray to the center of the planetary tray 6, is only related to the revolution;

[0056] 5) Angle β, the angle between the line from the center of the satellite disk 7 to the measuring point and the line from the center of the wafer 8 to the center of the satellite disk, is related to both revolution and rotation;

[0057] 6) γ angle, the angle between the line connecting the measuring point and the center of the satellite dish and the line connecting the center of the satellite dish to the center of the planetary tray 6, is only related to the revolution;

[0058] 7) a, the distance from the center of the satellite dish to the measurement point, is only related to the revolution and can be calculated;

[0059] 8) b. The distance from the center of the wafer to the measurement point is related to both revolution and rotation;

[0060] 9) ф angle, the angle between the line from the wafer center to the satellite disk center and the line from the satellite disk center to the planetary tray 6 center, which is only related to the satellite disk rotation;

[0061] 10)ф=γ-β. By calculating the change in the ф angle, we can get the rotation speed of the satellite dish.

[0062] 2. The data acquisition card samples at a fixed frequency f. A total of L lines of data are sampled within the time of two trigger pulses. The angle Δα rotated by the planetary tray 6 each time is sampled is 360 / L.

[0063] 3. If Figure 4 , when the edge of the wafer enters the measurement point, the number of sampling times between the sampling point at this time and the sampling point at the center of the satellite disk, L0, can be counted from the sampling data; then

[0064] α0=L0*Δα=360*L0 / L

[0065] dv, ds are known quantities, according to the calculation formula of any triangle,

[0066] a= α0)½

[0067] γ0=arcsin[(dv*sinα0) / a]

[0068] At this moment, the measurement point is exactly at the edge of the wafer, so b = the radius of the wafer Rwafer, which is a known quantity.

[0069] but ]

[0070] The rotation angle value at this moment can be calculated:

[0071] ф0=γ0-β0

[0072] 4. If Figure 5 As shown in the figure, at the same wafer measurement point, the number of sampling times between the sampling point at this time and the sampling point at the center of the satellite disk, L1, can also be counted from the sampling data; then:

[0073] α1=L1*Δα=360*L1 / L

[0074] a= α1)½

[0075] γ1=arcsin[(dv*sinα1) / a]

[0076] ]

[0077] ф1=γ1-β1

[0078] 5. The same wafer has a sampling number of L0-L1 from the edge entering the measurement point to the edge exiting the measurement point;

[0079] The rotation angle is ф1-ф0

[0080] The rotation angle of each sampling is Δф=

[0081] The satellite dish rotation speed, m, the number of revolutions per minute (RPM) = the number of samples per minute (f*60 seconds) multiplied by the angle of each sample (Δф) divided by 360 degrees

[0082] m= f*60*Δф / 360=f*Δф / 6.

[0083] The present invention uses a measuring probe composed of a collimated laser 2 and a photodetector 4 to emit a laser beam to a rotating tray, collects the reflected laser intensity signal, and can distinguish the edge of the satellite dish and the edge of the wafer on the satellite dish through a special algorithm, and calculates the rotation speed of the satellite dish by calculating the angle between the center of the wafer to the center of the satellite dish and the center of the satellite dish to the center of the large dish. This method is applicable to the case where the rotation speed of the satellite dish is greater than the rotation speed of the planetary tray 6 and the number of wafers on the satellite dish is greater than or equal to 2.

[0084] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for measuring the rotation speed of a satellite disk of a MOCVD planetary tray, characterized in that: The method comprises the following steps: A laser beam is emitted through a laser measuring probe (1) on the MOCVD device; The laser irradiates the planetary tray (6) of the MOCVD device, and as the planetary tray (6) rotates, the laser also irradiates the satellite tray (7) and the wafer (8) on the satellite tray (7); The reflected laser is converted into an electrical signal after being split; The electrical signal is sampled at a fixed frequency f within the time of two trigger pulse signals (9), and the angle Δα rotated by the planetary tray (6) is obtained each time the sampling is performed; According to the angle Δα, when the edge of the wafer (8) enters the measurement point, the rotation angle value ф0 at this moment is calculated; According to the angle Δα, when the edge of the wafer (8) leaves the measurement point, the rotation angle value ф1 at this moment is calculated; By calculating the changes in the angles ф0 and ф1, the rotation speed of the satellite dish (7) can be obtained.

2. The method for measuring the rotation speed of a satellite disk of a MOCVD planetary tray according to claim 1, characterized in that: The laser measurement probe (1) is mounted on the cavity observation window of the MOCVD device. The MOCVD device can provide a signal of the rotation of the planetary tray (6), where one rotation is a trigger pulse signal (9).

3. The method for measuring the rotation speed of a satellite disk of a MOCVD planetary tray according to claim 1, characterized in that: The satellite dish (7) and the planetary tray (6) are made of the same material and do not reflect laser light, while the wafer (8) reflects laser light.

4. The method for measuring the rotation speed of a satellite disk of a MOCVD planetary tray according to claim 1, characterized in that: The reflected laser is irradiated onto a detector through a beam splitter (3) and converted into an electrical signal, which is then collected by a multi-channel synchronous data collection card (5).

5. The method for measuring the rotation speed of a satellite disk of a MOCVD planetary tray according to claim 1, characterized in that: Sampling is performed at a fixed frequency f, and a total of L lines of data are sampled within the time of two trigger pulses. The angle Δα of the planetary disk of the planetary tray (6) rotated each time the sampling is performed is 360 / L. The number of sampling times from the sampling point at the moment when the edge of the wafer (8) enters the measurement point and the sampling point at the moment when the edge of the wafer (8) leaves the measurement point to the sampling point at the center of the satellite disk corresponds to L0 and L1, respectively, which can be counted from the sampling data.

6. The method for measuring the rotation speed of a satellite disk of a MOCVD planetary tray according to claim 5, characterized in that: The rotation angle value ф0=γ0-β0; Where: γ0=arcsin[(dv*sinα0) / a], ], according to the calculation formula of any triangle, a= α0)½ ; The rotation angle value ф1=γ1-β1; Where: a= α1)½; γ1=arcsin[(dv*sinα1) / a]; ]； α1=L1*Δα=360*L1 / L, α0=L0*Δα=360*L0 / L, Rwafer represents the radius of the wafer (8); Wherein dv, ds and dw are known quantities, representing the distance from the measuring point to the center of the planetary tray (6), the distance from the center of the satellite tray (7) to the center of the planetary tray (6) and the distance from the center of the wafer (8) to the center of the satellite tray (7), respectively; the angle α is the angle between the line connecting the measuring point and the center of the planetary tray (6) and the line connecting the center of the satellite tray (7) to the center of the planetary tray (6); the angle β is the angle between the line connecting the center of the satellite tray (7) to the measuring point and the line connecting the center of the wafer (8) to the center of the satellite tray (7); the angle γ is the angle between the line connecting the measuring point and the center of the satellite tray (7) and the line connecting the center of the satellite tray (7) to the center of the planetary tray (6); a is the distance from the center of the satellite tray (7) to the measuring point; the angle ф is the angle between the line connecting the center of the wafer (8) to the center of the satellite tray (7) and the line connecting the center of the satellite tray (7) to the center of the planetary tray (6).

7. The method for measuring the rotation speed of a satellite disk of a MOCVD planetary tray according to claim 6, characterized in that: The rotation angle of each sampling is Δф= ; Then the satellite dish (7) rotation speed m, the number of revolutions per minute = the number of sampling times per minute is f × 60 seconds multiplied by the angle rotated per sampling divided by 360 degrees; Then m= f×60×Δф / 360=f×Δф / 6.

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