Method for detecting defective or improperly placed substrates in a CVD reactor - Patent Application 20070122997

Abstract

The present invention relates to a method for detecting defective or improperly placed substrates (3) in a CVD reactor housing (1) with the aid of one or more optical sensors (3) that detect surface properties, such as layer thickness or temperature, of the substrates (3) before or during the processing of the substrates (3) in the CVD reactor housing (1). The measurement values ​​provided by the sensors (3) can be plotted in the form of measurement curves, from which patterns corresponding to each substrate (3) are obtained. The patterns can be compared with each other or with an average value (Lm) formed from the patterns.

Description

Technical Field

[0001] The present invention relates to a method for detecting a defective or inappropriately placed substrate in a CVD reactor with the assistance of one or more optical sensors, which detect the characteristics of the substrate surface before or during the processing process of the substrate in the CVD reactor housing, and a pattern is obtained based on this, and the pattern can be further compared with a comparison pattern. Furthermore, it relates to a CVD reactor having a programmable arithmetic unit.

Background Art

[0002] Patent Document 1 discloses an apparatus and method for detecting an error in the position of a substrate in a CVD reactor. Optical measurement values are obtained at a plurality of different positions. The optical measurement values are compared with each other as patterns.

[0003] Patent Document 2 discloses a method for optically observing a substrate rotating on a susceptor in order to detect the position of the substrate on the susceptor.

[0004] Patent Document 3 discloses a CVD reactor provided with a susceptor, in which substrates are circularly arranged around the rotation axis of the susceptor. In order to detect the inclination position of the susceptor with respect to the rotation plane, distance values are detected during the rotation of the susceptor using an optical sensor.

[0005] Patent Document 4 discloses a method for determining the lateral position of a substrate on a susceptor.

[0006] Patent Document 5 discloses a method for detecting an error in the position of a substrate on a susceptor in a CVD reactor.

[0007] From Patent Document 6, methods for detecting a defective or inappropriately placed substrate on a susceptor are known.

[0008] Patent Documents 7, 8, 9, and 10 disclose a CVD reactor for depositing a semiconductor layer on a substrate. There are a plurality of regularly arranged substrates on a susceptor disposed within a reactor housing, and these substrates are coated by supplying a reaction gas into a process chamber. A heating device for heating the susceptor is adjusted with the aid of signals from sensors. Some of these sensors measure the temperature of the substrate surface. The apparatus further has additional optical sensors, by means of which the layer thickness of the layer deposited during the deposition process can be determined in-situ. This is done in particular by reflectance measurement.

[0009] Furthermore, Patent Documents 11 to 16 are included as prior art.

Prior Art Documents

Patent Documents

[0010]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Patent Document 6

Patent Document 7

Patent Document 8

Patent Document 9

Patent Document 10

[0011] The problem of the present invention is to provide an improved method for detecting a defective or inappropriately placed substrate in a CVD reactor, and to easily execute such method. [Means for Solving the Problems]

[0012] This problem is solved by the invention defined in the claims. The dependent claims not only show further advantageous developments of the invention described in the subclaims, but also show independent solutions to the problems.

[0013] First and substantially, it is provided that a comparison pattern used to detect a defective substrate or an inappropriately placed substrate by comparing with a pattern obtained during a deposition process is obtained during the same deposition process. The comparison pattern is obtained from the same pattern to be compared with the comparison pattern, and is particularly calculated. The calculation of the comparison pattern is executed during the processing process.

[0014] The comparison pattern can be updated permanently. The processing process is preferably a coating process, in which case a layer, in particular a single-crystalline layer, is deposited on the substrate by supplying a reaction gas to the process chamber of a CVD reactor. The reaction gas can be a hydride of Group V and an organometallic compound of Group III. However, the reaction gas can also be a gas of Group IV, or a gas of Group II and Group VI. The layer is deposited on the substrate by the reaction gas decomposing by thermal decomposition in the gas phase in the process chamber or on the surface of the substrate. The substrates are regularly arranged on the susceptor, for example, in a circular arrangement around the center, and the susceptor is heated by a heating device.

[0015] One or more sensors for measuring the temperature of the susceptor are provided to adjust the temperature of the susceptor according to the measured values given by one or more sensors. Furthermore, additional sensors for measuring only the surface temperature of the substrate can be provided if necessary. These sensors are preferably fixedly coupled to the housing of the CVD reactor. The susceptor is rotatable about a rotation axis. During this rotation, as the substrate below the measurement point of the sensor moves, the measurement point moves on a circular line on the susceptor and on the substrate arranged on the susceptor. During this measurement, the measured values are continuously recorded, and on the one hand, they can be used to determine the temperature and / or temperature distribution on the substrate surface, or on the other hand, they can be used to continuously measure the layer thickness of the layer deposited on the substrate.

[0016] The sensor can be one or more pyrometers. The pyrometer can be sensitive to the ultraviolet region and / or the infrared region. The measurement can be reflectance measurement. During the measurement, as the measurement point moves across a plurality of substrates, the continuously recorded measurement values provide a measurement curve having a temporally sequential structure indicative of the characteristic properties of the substrate. This structure has conventionally been used to determine the lateral temperature distribution or growth uniformity. In the present invention, this structure is used to detect defective or improperly placed substrates in a CVD reactor. For this purpose, a pattern is formed from the measurement values. This can be done using existing methods such as image recognition, Fourier transform, noise analysis, etc. Those patterns are compared with each other to detect errors.

[0017] In particular, it is provided that a comparison pattern is calculated from the measurement values recorded during one full rotation of the susceptor and the measurement values formed therefrom. The comparison pattern is compared with all the individual patterns recorded during the same rotation of the susceptor. Using at least one sensor, a measurement curve can be recorded during one or more rotations of the susceptor. The measurement curve has a structure arranged sequentially in time. Each structure is obtained while the measurement point moves on one substrate. Patterns can be calculated from these structures, each of which can be related to each substrate. Those patterns can change during the processing process, especially while a layer is being deposited on the substrate. This is due to the current measurement values being updated every one rotation or every few rotations of the susceptor.

[0018] It can be provided that values comparable to each other are formed from the patterns. These values can be any of a scalar, a vector, or a matrix. From those values, characteristic values or average values can be formed. Those values can have the property of being able to specify the numerical difference between those values. It can be provided that the values of the individual patterns are compared with the characteristic values, and if the difference between the value related to the substrate and the characteristic value exceeds a threshold value, the substrate is regarded as an error. Further, a second threshold value is defined, and it can be provided that the deposition process is aborted if the difference exceeds this second threshold value.

[0019] Furthermore, it can be provided that at least one threshold value is determined by machine learning. It can also be provided that instead of comparing a pattern or a value obtained therefrom with a characteristic value, the patterns or values obtained therefrom are compared with each other. Furthermore, it can be provided that when the difference exceeds the threshold value, only a warning is given without stopping the deposition process.

[0020] In an exemplary embodiment of the present invention, it can be provided that at least one technical variable is measured, for example, the layer thickness or temperature on a substrate placed on a susceptor rotating below at least one sensor, using at least one sensor. In that exemplary embodiment, at least one sensor provides a measured value that can be plotted in the form of a measurement curve, the measurement curve having a structure related to each substrate respectively, the structure having patterns comparable to each other, values comparable to each other being obtained from those patterns, and only the comparable values obtained from the simultaneously recorded measured values being compared with each other, or being compared with an average value formed from the simultaneously recorded measured values, in order to detect defective or inappropriately placed substrates.

[0021] The method can be carried out during a processing process in which a plurality of substrates are heat-treated simultaneously, and also before the processing process, for example, during a heating process. It can be provided that the measured values recorded during a plurality of full rotations of the susceptor are used. The measurement points move over a 360° azimuth angle while orbiting around the axis of rotation when the susceptor rotates. During this orbit, measured values are recorded for each substrate located at the relevant azimuth angle. Each time it rotates, those measured values can be updated, or an average value of the measured values for each substrate can be obtained.

[0022] The present invention further relates to a CVD reactor provided with a susceptor that can be heated by a heating device. There is a storage location for the substrate on the susceptor. Process gas can be supplied into the process chamber of the CVD reactor through a gas inlet member. A sensor capable of measuring the optical properties of the substrate is provided. The CVD reactor is further provided with an arithmetic unit programmed to detect defective or inappropriately placed substrates within the CVD reactor. The method corresponds to the method described above.

Brief Description of the Drawings

[0023] Hereinafter, the present invention will be described in more detail with reference to exemplary embodiments with reference to the accompanying drawings.

Figure 1

Figure 2

Figure 3

Embodiments for Carrying Out the Invention

[0024] Figure 1 shows a CVD reactor with a hermetic reactor housing 1. Inside the reactor housing 1, there is a process chamber between the process chamber ceiling 4 and the susceptor 2, into which reaction gas is supplied through the gas inlet member 8. The susceptor 2 is heated from below by a heating device 9. A plurality of substrates 3 are placed on the susceptor 2. In an exemplary embodiment, the substrates 3 are each placed within a pocket 12. The pocket 12 is formed by a substrate holder 13 placed within a recess 14 of the susceptor 2. The substrate holder 13 can float on a gas cushion that rotates the substrate holder 13 about its axis. Through a through-hole 5 in the process chamber ceiling 4, the optical path 7 of an optical sensor 6 fixedly coupled to the housing 1 runs. The optical path 7 reaches a measurement point 10 on the substrate 3. The temperature of the substrate 3 can be measured using the sensor 6. However, using the sensor 6 or a further sensor, another optical property of the substrate 3, such as reflectivity, can be measured in order to continuously measure the layer thickness of the layer deposited on the substrate 3 during the deposition process.

[0025] During the coating process, since the susceptor 2 rotates about the rotation axis A, the measurement point 10 moves along a circular orbit 11 that extends across a plurality of substrates 3 arranged circularly around the rotation axis A. The circular orbit 11 extends through the center of the substrate 3 or the center of the pocket 10 or the substrate holder 13.

[0026] In another exemplary embodiment, not shown, the substrates 3 may be densely arranged in a hexagonal pattern or may be distributed across the entire surface of the susceptor 2. In these exemplary embodiments, the gas inlet member 8 can have the form of a showerhead. Means are provided that are suitable for the measurement point 10 of the optical sensor to move across a plurality of substrates 3. For example, the optical path can be appropriately controlled via a deflection element.

[0027] At least one of the one or more optical sensors 6 can be used to control the heating device 9 or another actuator of the CVD reactor.

[0028] During one rotation of the susceptor 2, at least one sensor 6 provides a signal that can have substantially the shape shown in FIG. 3. This signal, unlike that in FIG. 2, results from an apparatus in which five substrates 3 are uniformly arranged around the rotation axis A of the susceptor 2. While the measurement point 10 moves across the plurality of substrates 3, characteristic measurement curve segments having predetermined patterns a, b, c, d, e are formed. If all the substrates 3 have substantially the same quality and are properly arranged on the susceptor 2, for example, correctly placed in the pockets 12 formed on the upper surface of the susceptor 2 for receiving the substrates 3, the patterns a, b, c, d, e are substantially the same or similar. In FIG. 3, these are patterns a, b, c, and e.

[0029] The curve segment formed by pattern d is different from the other patterns. According to the present invention, it is determined that pattern d deviates by comparing patterns a, b, c, d, e with each other. Thus, pattern d corresponds to a defective or improperly placed substrate 3 within the pocket 12.

[0030] To detect a defective or improperly placed substrate 3, patterns a, b, c, d, e can be associated with values La, Lb, Lc, Ld, Le. These values can be determined by Fourier analysis, image recognition, noise analysis, etc. It is possible to provide for forming an average value Lm from those values. Lm=(La+Lb+Lc+Ld+Le) / 5 This average value can be compared with all the values. Aa=La-Lm Ab=Lb-Lm Ac=Lc-Lm Ad=Ld-Lm Ae=Le-Lm

[0031] If the difference Aa, Ab, Ac, Ad, Ae between one of the values La, Lb, Lc, Ld, Le and the average value Lm exceeds a threshold value Ls, a warning can be given that the substrate 3 is defective or improperly placed. However, it is also possible to abort the coating process when the threshold value is exceeded.

[0032] In the present invention, it is not possible to use only the sensor signal S obtained by a pyrometer for measuring the temperature of the substrate surface. For example, the sensor signal S obtained from another optical sensor that is a sensor for measuring the layer thickness of the layer deposited on the substrate 3 can also be used.

[0033] The threshold value can change dynamically. In particular, a machine learning method can be used to determine the threshold value. It is possible to store the measured values recorded by the sensor, such as spectra, in a database and determine the threshold value from their history data.

[0034] The method according to the present invention can be used to detect whether the substrate 3 is damaged, or whether the substrate 3 is not properly placed in the pocket 12 related thereto, or whether the substrate holder 13 that supports one or more substrates 3 on the gas cushion is not properly rotating on the gas cushion.

[0035] It should be understood that in FIG. 3, t represents the azimuth angle, and FIG. 3 represents the measurement curve of the full rotation of the susceptor. From a plurality of such measurement curves recorded sequentially, individualized and / or averaged patterns a, b, c, d, e can be determined for each substrate 3. Alternatively, characteristic values La, Lb, Lc, Ld, Le can be formed from a plurality of patterns a, b, c, d, e determined sequentially in time, and they are respectively calculated from a plurality of patterns individually associated with each substrate.

[0036] The above is for explaining the invention which is the subject of the present application as a whole, and it is also an improvement over the prior art independently by at least the following combinations of features in each case, and it is also possible to combine two, more or all of these combinations of features.

[0037] A method characterized in that the comparison pattern is formed from the patterns a, b, c, d, e obtained during the same processing process.

[0038] A method characterized in that a plurality of substrates 3 of the same type are arranged in a regular array on a susceptor 2.

[0039] A plurality of substrates 3 are 2 arranged on at least one arc around the rotation axis A of the susceptor, and at least one optical sensor 6 is provided stationary with respect to the reactor housing 1 such that as a result of the relative rotation of the susceptor 2 with respect to the reactor housing 1, the measurement point 10 moves on a circular orbit 11 across the plurality of substrates 3.

[0040] Patterns a, b, c, d, e are obtained from the measured values recorded while the measurement point 10 moves across the surface of the substrate 3, and related values La, Lb, Lc, Ld, Le are respectively formed from the patterns a, b, c, d, e obtained during at least one full rotation or multiple full rotations of the susceptor 2 and these related values are comparable to each other, and the values La, Lb, Lc, Ld, Le thus formed are compared to each other to detect an error.

[0041] A method characterized in that the patterns a, b, c, d, e are obtained from reflectance measurement values or temperature values.

[0042] A method characterized in that the patterns a, b, c, d, e are calculated by processing signals given by at least one sensor 6, and in this calculation, methods such as image recognition, Fourier transform, noise analysis, etc. are used.

[0043] A characteristic value or an average value Lm is formed from the related values La, Lb, Lc, Ld, Le, all of them are compared with the values La, Lb, Lc, Ld, Le, and an error is detected when a difference between one of the values La, Lb, Lc, Ld, Le and the characteristic value or the average value Lm exceeds a threshold value Ls.

[0044] A method characterized in that patterns a, b, c, d, e are obtained from measurement values obtained for the control of a CVD reactor and / or for the control of a heating device 9 for heating a susceptor 2.

[0045] Using at least one sensor 6, at least one technical variable is measured, for example the layer thickness or temperature of a substrate 3 placed on a susceptor 2 rotating below at least one sensor 6. At least one sensor 6 gives a measurement value that can be plotted in the form of a measurement curve, and the measurement curve has a structure with patterns that can be compared with each other and can be associated with each substrate 3. Values La, Lb, Lc, Ld, Le that can be compared with each other are obtained from these patterns, and these values are compared with the average value formed from the simultaneously recorded measurement values.

[0046] From a plurality of patterns a, b, c, d, e related individually to each substrate 3 by a plurality of movements of measurement points 10 across a plurality of substrates 3, values La, Lb, Lc, Ld, Le related to each substrate 3 are formed, and the values La, Lb, Lc, Ld, Le are compared with each other.

[0047] All the features disclosed are essential to the present invention (for themselves and in combination with each other). The disclosure of the application here includes the disclosure content of the relevant / additional priority documents (copies of previous applications) in their entirety, which is also for the purpose of incorporating the features of these documents into the claims of the present application. Dependent claims, especially for the purpose of filing a divisional application based on these claims, are characterized by further independent inventive developments of the prior art even without the features of the cited claims. The invention specified in each claim can additionally have one or more functions specified in the above description, especially those with reference signs and / or specified in the description of the signs. The present invention also relates to a design form in which the individual ones of the features described in the above description are not implemented, especially as long as they are clearly unnecessary for their respective purposes of use or can be replaced by other means having the same technical effect.

Explanation of Signs

[0048] 1 Reactor housing 2 Susceptor 3 Substrate 4 Process chamber ceiling 5 Through-hole 6 Optical sensor 7 Optical path 8 Gas inlet member 9 Gas outlet member 10 Measurement point 11 Circular orbit 12 Pocket 13 Substrate holder 14 Recess A Rotation axis S Sensor signal a, b, c, d, e patterns t Time La, Lb, Lc, Ld, Le values Lm Average value Ls Threshold value

Claims

1. A method for detecting a defective or inappropriately placed substrate (3) on a susceptor (2) that can be heated by a heating device (9) in a CVD reactor during a processing process, comprising: During the processing process, the optical properties of the surface of the substrate (3) are detected using a measurement point (10) that moves across the surfaces of a plurality of substrates (3). Based on the optical properties, a measurement curve is determined to detect the defective or inappropriately placed substrate (3). Patterns (a, b, c, d, e) are obtained from the measurement curve, and the patterns (a, b, c, d, e) are compared with a comparison pattern. The comparison pattern is obtained from patterns obtained during the same processing process. In the method, the optical properties are detected by at least one optical sensor (6). The optical sensor (6) is used to control the heating device (9) for temperature adjustment of the susceptor (2) or to measure the layer thickness of a layer deposited on the substrate (3).

2. The method according to claim 1, characterized in that a plurality of the same type of substrates (3) are arranged in a regular array on the susceptor (2).

3. The method according to claim 2, characterized in that a plurality of the substrates (3) are arranged on at least one arc around the rotation axis (A) of the susceptor (2), and at least one optical sensor (6) is provided stationary with respect to the reactor housing (1) such that as a result of the relative rotation of the susceptor (2) with respect to the reactor housing (1), the measurement point (10) moves on a circular orbit (11) across the plurality of substrates (3).

4. A measured value is obtained based on the optical properties detected by the optical sensor (6). Based on the measured value, related values (La, Lb, Lc, Ld, Le) related to the patterns (a, b, c, d, e) are determined by Fourier analysis, image recognition, or noise analysis from the patterns (a, b, c, d, e) obtained during at least one full rotation or multiple full rotations of the susceptor (2). The related values (La, Lb, Lc, Ld, Le) are comparable to each other, and In order to detect an error, the related values (La, Lb, Lc, Ld, Le) thus determined are compared with each other, or compared with an average value formed from the measured values recorded simultaneously, according to any one of claims 1 to 3.

5. The method according to any one of claims 1 to 4, characterized in that the pattern (a, b, c, d, e) is obtained from measured values of reflectance or measured values of temperature.

6. The method according to any one of claims 1 to 5, characterized in that the pattern (a, b, c, d, e) is calculated by processing a signal provided by at least one of the optical sensors (6).

7. An average value (Lm) is formed from the related values (La, Lb, Lc, Ld, Le), the average value (Lm) is compared with all the related values (La, Lb, Lc, Ld, Le), and an error is detected when a difference of one of the related values (La, Lb, Lc, Ld, Le) with respect to the average value (Lm) exceeds a threshold value (Ls), according to the method of claim 4.

8. The measurement curve has a structure having the patterns (a, b, c, d, e) that can be associated with each substrate (3) and compared with each other. Related values (La, Lb, Lc, Ld, Le) that can be compared with each other are obtained from the patterns (a, b, c, d, e), and these values are compared with an average value formed from the measured values recorded simultaneously, according to any one of claims 1 to 7.

9. Values (La, Lb, Lc, Ld, Le) related to each substrate (3) are formed from a plurality of the patterns (a, b, c, d, e) individually related to each substrate (3) by a plurality of movements of the measurement points (10) across a plurality of the substrates (3), and the related values (La, Lb, Lc, Ld, Le) are compared with each other, according to any one of claims 1 to 8.

10. A CVD reactor having a reactor housing (1), a susceptor (2) disposed within the reactor housing (1) and carrying a substrate (3) to be coated and heatable by a heating device (9), an optical sensor (6) for determining an optical property of the surface of the substrate (3), and an arithmetic unit for analyzing measured values detected by the optical sensor (6). The CVD reactor is characterized in that the arithmetic unit is programmed to detect a defective or inappropriately placed substrate in the CVD reactor by using the method according to any one of claims 1 to 9.

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