Semiconductor wafer transport method and semiconductor wafer transport device

Abstract

To provide a semiconductor wafer transport method capable of suppressing erroneous determination of whether a non-contact chuck is detached from a semiconductor wafer.SOLUTION: A semiconductor wafer transport method includes the steps of preparing a non-contact chuck having an optical sensor and a semiconductor wafer having a first main surface, positioning the non-contact chuck such that the optical sensor and the first main surface face each other with a gap between them, having the optical sensor irradiate light onto the first main surface and measure a first intensity, which is the intensity of light reflected by the first main surface, before bringing the non-contact chuck close to the first main surface, bringing the non-contact chuck close to the first main surface and having the non-contact chuck blow gas onto the first main surface, thereby holding the semiconductor wafer in a non-contact state, and detaching the non-contact chuck from the semiconductor wafer by moving the non-contact chuck away from the first main surface.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present disclosure relates to a semiconductor wafer transport method and a semiconductor wafer transport device. [Background technology]

[0002] For example, Japanese Patent Application Laid-Open No. 2023-97770 (Patent Document 1) describes a semiconductor wafer transport device. The semiconductor wafer transport device described in Patent Document 1 has a non-contact chuck. The non-contact chuck holds the semiconductor wafer in a non-contact state by blowing gas onto the main surface of the semiconductor wafer. The non-contact chuck is provided with a sensor facing the main surface of the semiconductor wafer. The sensor determines whether or not the semiconductor wafer is being held by the non-contact chuck. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2023-97770 Summary of the Invention [Problem to be solved by the invention]

[0004] A reflective sensor may be used as the sensor for the non-contact chuck. The reflective sensor measures the intensity of light reflected by the main surface of the semiconductor wafer. If an attempt is made to determine whether the non-contact chuck has been released from the semiconductor wafer by comparing this intensity with a preset threshold, an error in the determination may occur. Other problems and novel features will become apparent from the description of this specification and the accompanying drawings. [Means for solving the problem]

[0005] The semiconductor wafer transport method of the present disclosure includes the steps of: preparing a non-contact chuck having an optical sensor and a semiconductor wafer having a first main surface; positioning the non-contact chuck so that the optical sensor and the first main surface face each other with a gap between them; having the optical sensor irradiate light onto the first main surface and measure a first intensity, which is the intensity of light reflected by the first main surface, before bringing the non-contact chuck close to the first main surface; bringing the non-contact chuck close to the first main surface and having the non-contact chuck blow gas onto the first main surface, thereby holding the semiconductor wafer in a non-contact state; moving the non-contact chuck away from the first main surface, thereby detaching the non-contact chuck from the semiconductor wafer; and, during the process of moving the non-contact chuck away from the first main surface, having the optical sensor irradiate light onto the first main surface and measure a second intensity, which is the intensity of light reflected by the first main surface. In the step of detaching the non-contact chuck from the semiconductor wafer, it is determined that the non-contact chuck has been detached from the semiconductor wafer when the second intensity becomes the first intensity. [Effects of the Invention]

[0006] According to the semiconductor wafer transport method of the present disclosure, it is possible to reduce errors in determining whether or not the non-contact chuck has been detached from the semiconductor wafer. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 2 is a schematic plan view of the transport device DEV. [Figure 2] FIG. 2 is a schematic side view of the transport device DEV. [Figure 3] FIG. 2 is a functional block diagram of the transport device DEV. [Figure 4] FIG. 10 is a schematic plan view of a transport device DEV according to a modified example. [Figure 5] 10A to 10C are process diagrams of a method for transporting a semiconductor wafer SW using the transport device DEV. [Figure 6] FIG. 10 is a schematic side view illustrating a chuck placement step S2. [Figure 7] FIG. 10 is a schematic side view illustrating a reflection intensity measuring step S3. [Figure 8] FIG. 10 is a schematic side view illustrating a semiconductor wafer holding step S4. [Figure 9] FIG. 10 is a schematic side view illustrating a chucking release step S5. [Figure 10] 10 is a graph showing the intensity of reflected light measured by the light receiving portion of the optical sensor OS when the distance between the optical sensor OS and the first main surface MS1 is changed. [Figure 11] 10 is a graph showing the relationship between the color of the surface of a semiconductor wafer SW and the reflectance of red light on the surface of the semiconductor wafer SW. DETAILED DESCRIPTION OF THE INVENTION

[0008] An embodiment of the present disclosure will be described with reference to the drawings. In the following drawings, the same or corresponding parts are designated by the same reference numerals, and redundant description will not be repeated. A semiconductor wafer transport device according to the embodiment is referred to as a transport device DEV.

[0009] (Configuration of the transport device DEV) The configuration of the transport device DEV will be described below.

[0010] FIG. 1 is a schematic plan view of the transfer device DEV. FIG. 2 is a schematic side view of the transfer device DEV. As shown in FIGS. 1 and 2, the transfer device DEV has a non-contact chuck CHK. The non-contact chuck CHK holds the semiconductor wafer SW in a non-contact manner. The semiconductor wafer SW is indicated by dotted lines in FIGS. 1 and 2. The semiconductor wafer SW has a first main surface MS1 and a second main surface MS2. The second main surface MS2 is the surface opposite to the first main surface MS1. The first main surface MS1 and the second main surface MS2 are end surfaces in the thickness direction of the semiconductor wafer SW.

[0011] The semiconductor wafer SW is, for example, any one of a silicon wafer, an SOI (Silicon On Insulator) wafer, a silicon carbide wafer, a sapphire wafer, a gallium nitride wafer, a gallium phosphide wafer, and a gallium arsenide wafer. However, the semiconductor wafer SW is not limited to these. An electric circuit pattern is formed on one of the first main surface MS1 and the second main surface MS2. The electric circuit pattern is formed on, for example, the first main surface MS1.

[0012] The non-contact chuck CHK has a support member SM, a plurality of pads PD, and an optical sensor OS. The support member SM has a first surface F1 and a second surface F2. The second surface F2 is the surface opposite to the first surface F1. The first surface F1 and the second surface F2 are end surfaces in the thickness direction of the support member SM. For example, in a plan view, that is, when viewed from the first surface F1 side along the normal direction of the first surface F1, the support member SM has a first portion SM1, a second portion SM2, and a third portion SM3.

[0013] The first portion SM1 extends linearly in a plan view. The transfer device DEV has a transfer arm ARM, and the non-contact chuck CHK is attached to the transfer arm ARM at the first portion SM1. The support member SM branches into a second portion SM2 and a third portion SM3 at the tip of the first portion SM1. The second portion SM2 and the third portion SM3 have shapes that follow the outer periphery of the first main surface MS1 in a plan view. However, the tip of the second portion SM2 and the tip of the third portion SM3 are spaced apart from each other. From another perspective, the second portion SM2 and the third portion SM3 are horseshoe-shaped in a plan view.

[0014] The pad PD is attached to the second surface F2. More specifically, the pad PD is attached to the second surface F2 in the second portion SM2 and the second surface F2 in the third portion SM3. The pad PD is, for example, circular in plan view. The pad PD has a third surface F3 and a fourth surface F4. The third surface F3 faces the second surface F2. The fourth surface F4 is the surface opposite the third surface F3. The third surface F3 and the fourth surface F4 are end surfaces of the pad PD in the thickness direction. A flow path FP is formed inside the support member SM and inside the pad PD. The flow path FP is indicated by dotted lines in FIG. 2.

[0015] The gas flowing through the flow path FP is sprayed onto the first main surface MS1 from a nozzle located on the fourth surface F4 and connected to the flow path FP, and is then released from between the fourth surface F4 and the first main surface MS1. This creates a vacuum between the fourth surface F4 and the first main surface MS1, allowing the non-contact chuck CHK to hold the semiconductor wafer SW in a non-contact state. The non-contact chuck CHK may be a Bernoulli chuck or a cyclone chuck. If the non-contact chuck CHK is a Bernoulli chuck, the gas is released radially from the nozzle, and if the non-contact chuck CHK is a cyclone chuck, the gas is released as a swirling flow from the nozzle.

[0016] The optical sensor OS is, for example, a reflective sensor. The optical sensor OS has a light source and a light receiving unit. The optical sensor OS is provided on the non-contact chuck CHK so that the light source and the light receiving unit face the semiconductor wafer SW (first main surface MS1). More specifically, the optical sensor OS is provided on the second surface F2 at the tip of the first portion SM1. From another perspective, the light source and the light receiving unit of the optical sensor OS face the outer periphery of the first main surface MS1.

[0017] The light source of the optical sensor OS irradiates light L onto the first main surface MS1. The light source of the optical sensor OS is, for example, a red semiconductor laser. That is, the wavelength of the light L irradiated by the light source of the optical sensor OS is, for example, not less than 640 nm and not more than 770 nm. The light receiving unit of the optical sensor OS outputs a signal according to the intensity of the light L reflected by the first main surface MS1. Note that the light source of the optical sensor OS may be capable of irradiating light L of a plurality of different wavelengths onto the first main surface MS1.

[0018] The transfer arm ARM is moved in the horizontal direction (a direction parallel to the first surface F1 and the second surface F2) by a drive mechanism (not shown). As a result, the non-contact chuck CHK is also moved in the horizontal direction. The transfer arm ARM is also moved in the vertical direction (a direction normal to the first surface F1 and the second surface F2) by the drive mechanism. As a result, the non-contact chuck CHK is also moved in the vertical direction. Note that the drive mechanism can tilt the non-contact chuck CHK by the operation of the transfer arm ARM so that the first surface F1 and the second surface F2 are inclined with respect to the horizontal direction. Tilting the non-contact chuck CHK also tilts the semiconductor wafer SW held by the non-contact chuck CHK, making it possible to read markings and the like on the main surface of the semiconductor wafer SW.

[0019] Fig. 3 is a functional block diagram of the transport device DEV. As shown in Fig. 3, the transport device DEV has a controller CTR and a memory MEM. The light receiving unit of the optical sensor OS is connected to the controller CTR, and an output signal from the light receiving unit of the optical sensor OS is input to the controller CTR. The memory MEM is connected to the controller CTR. The controller CTR is configured, for example, by a microcontroller, and the memory MEM is configured, for example, by a DRAM (Dynamic Random Access Memory), a flash memory, etc.

[0020] <Modification> Although the above describes an example in which the support member SM has a horseshoe shape in a plan view, the planar shape of the support member SM is not limited to this. FIG. 4 is a schematic plan view of a transport device DEV according to a modified example. As shown in FIG. 4, the support member SM may have a fourth portion SM4 instead of the second portion SM2 and the third portion SM3. The fourth portion SM4 may be circular in a plan view. In this case, the optical sensor OS may be disposed, for example, so as to face the center of the first main surface MS1.

[0021] In the above, an example has been described in which the object held by the non-contact chuck CHK is a semiconductor wafer SW, but the object held by the non-contact chuck CHK is not limited to a semiconductor wafer SW. The object held by the non-contact chuck CHK may also be paper. More specifically, the object held by the non-contact chuck CHK may be, for example, an interlayer sheet that is placed between two adjacent semiconductor wafers SW when multiple semiconductor wafers SW are stacked. The color of the interlayer sheet may be different from the color of the surface of the semiconductor wafer SW.

[0022] (Transportation method using the transport device DEV) A method for transporting the semiconductor wafer SW using the transport device DEV will be described below.

[0023] 5 is a process diagram of a method for transporting a semiconductor wafer SW using the transport device DEV. As shown in FIG. 5, the method for transporting a semiconductor wafer SW using the transport device DEV includes a preparation step S1, a chuck placement step S2, a reflection intensity measurement step S3, a semiconductor wafer holding step S4, and a chucking step S5.

[0024] In the preparation step S1, a transfer device DEV and a semiconductor wafer SW are prepared. After the preparation step S1, a chuck placement step S2 is performed.

[0025] 6 is a schematic side view illustrating the chuck placement step S2. As shown in FIG. 6, in the chuck placement step S2, the non-contact chuck CHK is moved onto the semiconductor wafer SW so that the second surface F2 faces the first main surface MS1 with a gap therebetween. After the chuck placement step S2, a reflection intensity measurement step S3 is performed.

[0026] 7 is a schematic side view illustrating the reflection intensity measurement step S3. As shown in FIG. 7, in the reflection intensity measurement step S3, the light source of the optical sensor OS irradiates light L onto the first main surface MS1. The light L is reflected by the first main surface MS1 and then enters the light receiving section of the optical sensor OS. The light receiving section of the optical sensor OS outputs a signal corresponding to the intensity of the incident light L to the controller CTR. The controller CTR stores the intensity of the light L in the memory MEM. After the reflection intensity measurement step S3 is performed, the semiconductor wafer holding step S4 is performed.

[0027] 8 is a schematic side view illustrating the semiconductor wafer holding step S4. As shown in FIG. 8, in the semiconductor wafer holding step S4, the non-contact chuck CHK is brought close to the first main surface MS1. As a result, a vacuum state is created by blowing gas onto the first main surface MS1 from the nozzles on the fourth surface F4, and the semiconductor wafer SW is held in a non-contact state by the non-contact chuck CHK.

[0028] As the non-contact chuck CHK approaches the first main surface MS1, the light source of the optical sensor OS irradiates the first main surface MS1 with light L, and the light receiving portion of the optical sensor OS outputs a signal corresponding to the intensity of the light L reflected by the first main surface MS1 to the controller CTR. The controller CTR compares the intensity of the light L measured during this process with the intensity of the light L stored in the memory MEM in the reflection intensity measurement step S3, and determines that the non-contact chuck CHK is holding the semiconductor wafer SW when the former is smaller than the latter. After the semiconductor wafer holding step S4, a chucking dechucking step S5 is performed.

[0029] 9 is a schematic side view illustrating the dechucking step S5. As shown in FIG. 9, in the dechucking step S5, the non-contact chuck CHK is separated from the first main surface MS1. As a result, the attractive force from the non-contact chuck CHK no longer acts on the semiconductor wafer SW, and the non-contact chuck CHK is detached from the semiconductor wafer SW.

[0030] As the non-contact chuck CHK moves away from the first main surface MS1, the light source of the optical sensor OS irradiates the first main surface MS1 with light L, and the light receiving portion of the optical sensor OS outputs a signal corresponding to the intensity of the light L reflected by the first main surface MS1 to the controller CTR. The controller CTR compares the intensity of the light L measured during this process with the intensity of the light L stored in the memory MEM in the reflection intensity measurement step S3, and determines that the non-contact chuck CHK has detached from the semiconductor wafer SW when the former and latter match.

[0031] (Effect of the transport device DEV) The effects of the transport device DEV will be described below in comparison with a comparative example.

[0032] A contact-type chuck, more specifically, a vacuum-type chuck, is sometimes used to hold a semiconductor wafer SW. With a vacuum-type chuck, it is possible to determine whether the chuck has detached from the semiconductor wafer SW based on changes in the pressure applied to the semiconductor wafer SW. However, while a vacuum-type chuck can be used to hold a semiconductor wafer SW by sucking the second main surface MS2, it cannot be used to hold a semiconductor wafer SW by sucking the first main surface MS1 on which an electrical circuit pattern is formed.

[0033] Therefore, in order to hold the semiconductor wafer SW on the first main surface MS1, it is necessary to use a non-contact chuck such as a Bernoulli chuck or a cyclone chuck. When a reflective sensor provided on the non-contact chuck is used to determine whether the non-contact chuck is holding the semiconductor wafer SW (whether the non-contact chuck has detached from the semiconductor wafer SW), a threshold value is set in advance, and the intensity of light reflected from the first main surface MS1 is compared with the threshold value to determine whether the non-contact chuck is holding the semiconductor wafer SW (whether the non-contact chuck has detached from the semiconductor wafer SW).

[0034] However, in this case, the state of reflection of light on the first main surface MS1 changes depending on the warpage of the semiconductor wafer SW, the type of semiconductor wafer SW on the first main surface MS1, the state of formation of the electric circuit pattern, etc. As a result, with the above-described method, it is difficult to accurately determine whether the non-contact chuck is holding the semiconductor wafer SW (whether the non-contact chuck has detached from the semiconductor wafer SW).

[0035] FIG. 10 is a graph showing the intensity of reflected light measured by the light receiving portion of the optical sensor OS when the distance between the optical sensor OS and the first main surface MS1 is changed. In Samples 1 and 2 of FIG. 10, the semiconductor wafer SW is a silicon wafer. In Sample 3 of FIG. 10, the semiconductor wafer SW is a silicon carbide wafer. In Sample 1 of FIG. 10, an electrical circuit pattern is formed on the first main surface MS1, while in Samples 2 and 3 of FIG. 10, no electrical circuit pattern is formed on the first main surface MS1. The vertical axis of FIG. 10 represents the voltage of the output signal from the light receiving portion of the optical sensor OS, and the horizontal axis of FIG. 10 represents the distance between the optical sensor OS and the first main surface MS1.

[0036] 10, when comparing Sample 1 and Sample 2, i.e., when comparing the cases where an electrical circuit pattern is formed on the first main surface MS1 and where it is not, the output of the light receiving part of the optical sensor OS when the non-contact chuck CHK is holding the semiconductor wafer SW differs for each sample, and the output of the light receiving part of the optical sensor OS when the non-contact chuck CHK is detached from the semiconductor wafer SW differs for each sample. Also, when comparing Sample 2 and Sample 3, i.e., when the types of semiconductor wafer SW are different, the output of the light receiving part of the optical sensor OS when the non-contact chuck CHK is holding the semiconductor wafer SW differs for each sample, and the output of the light receiving part of the optical sensor OS when the non-contact chuck CHK is detached from the semiconductor wafer SW differs for each sample.

[0037] However, all the samples have in common the fact that the output of the light receiving part of the optical sensor OS changes depending on whether the non-contact chuck CHK is holding the semiconductor wafer SW or whether the non-contact chuck CHK is detached from the semiconductor wafer SW.

[0038] The conveying device DEV focuses on the fact that the output of the light receiving part of the optical sensor OS changes when the non-contact chuck CHK is holding the semiconductor wafer SW and when the non-contact chuck CHK is detached from the semiconductor wafer SW, and determines that the non-contact chuck CHK has detached from the semiconductor wafer SW if the intensity of the light L measured as the non-contact chuck CHK moves away from the first main surface MS1 matches the intensity of the light L stored in the memory MEM in the reflection intensity measurement process S3.

[0039] From a similar perspective, the transfer device DEV determines that the non-contact chuck CHK is holding the semiconductor wafer SW when the intensity of the light L being measured as the non-contact chuck CHK approaches the first main surface MS1 becomes smaller than the intensity of the light L stored in the memory MEM in the reflection intensity measurement step S3. Therefore, the transfer device DEV can prevent errors from occurring in determining whether the non-contact chuck is holding the semiconductor wafer SW (whether the non-contact chuck has detached from the semiconductor wafer SW) even when the type of semiconductor wafer SW or the state of formation of the electric circuit pattern is different.

[0040] 11 is a graph showing the relationship between the color of the surface of the semiconductor wafer SW and the reflectance of red light on the surface of the semiconductor wafer SW. As shown in FIG. 11, the reflectance of red light on the surface of the semiconductor wafer SW varies greatly depending on the color of the surface of the semiconductor wafer SW. Therefore, if an attempt is made to determine whether the non-contact chuck is holding the semiconductor wafer SW (whether the non-contact chuck has detached from the semiconductor wafer SW) by comparing a preset threshold value with the output from the light-receiving unit of the reflective sensor, an erroneous determination result may be obtained.

[0041] On the other hand, regardless of the color of the surface of the semiconductor wafer SW, the output of the light receiving portion of the optical sensor OS changes between a state in which the non-contact chuck CHK is holding the semiconductor wafer SW and a state in which the non-contact chuck CHK is detached from the semiconductor wafer SW. Therefore, the transport device DEV can prevent errors from occurring in determining whether the non-contact chuck CHK is holding the semiconductor wafer SW (whether the non-contact chuck CHK is detached from the semiconductor wafer SW) even when the surface of the semiconductor wafer SW has a different color.

[0042] In one case, multiple semiconductor wafers SW are stacked with interlayer paper between them, and these multiple semiconductor wafers SW and interlayer paper are sometimes transported sequentially to another case. Because the surface colors of the semiconductor wafers SW and the interlayer paper are different from each other, in this case, objects of different colors are alternately held and released by the non-contact chuck CHK. As described above, the transport device DEV is unlikely to make an error in determining whether the non-contact chuck CHK is holding the object (the non-contact chuck CHK has released from the object) even if the objects are different colors, making it possible to transport such objects without replacing the non-contact chuck CHK.

[0043] The invention made by the inventor has been specifically described above based on an embodiment, but it goes without saying that the present invention is not limited to the above embodiment and can be modified in various ways without departing from the gist of the invention. [Explanation of symbols]

[0044] ARM: transfer arm, CHK: non-contact chuck, CTR: controller, DEV: transfer device, F1: first surface, F2: second surface, F3: third surface, F4: fourth surface, FP: flow path, L: light, MEM: memory, MS1: first main surface, MS2: second main surface, OS: optical sensor, PD: pad, S1: preparation step, S2: chuck placement step, S3: reflection intensity measurement step, S4: semiconductor wafer holding step, S5: chuck de-chucking step, SM: support member, SM1: first part, SM2: second part, SM3: third part, SM4: fourth part, SW: semiconductor wafer.

Claims

1. providing a non-contact chuck having an optical sensor and a semiconductor wafer having a first main surface; disposing the non-contact chuck so that the optical sensor and the first main surface face each other with a gap therebetween; Before bringing the non-contact chuck close to the first main surface, the optical sensor irradiates the first main surface with light and measures a first intensity that is an intensity of light reflected by the first main surface; a step of bringing the non-contact chuck close to the first main surface and causing the non-contact chuck to blow gas onto the first main surface, thereby causing the non-contact chuck to hold the semiconductor wafer in a non-contact state; detaching the non-contact chuck from the semiconductor wafer by moving the non-contact chuck away from the first main surface; and a step of, during a process of moving the non-contact chuck away from the first main surface, using the optical sensor to irradiate the first main surface with light and measure a second intensity that is the intensity of the light reflected by the first main surface, In the step of detaching the non-contact chuck from the semiconductor wafer, it is determined that the non-contact chuck has been detached from the semiconductor wafer when the second strength becomes the first strength.

2. 2. The semiconductor wafer transport method according to claim 1, wherein the non-contact chuck is a Bernoulli chuck or a cyclone chuck.

3. 2. The semiconductor wafer transport method according to claim 1, wherein the non-contact chuck is disposed so that the optical sensor faces a central portion of the first main surface.

4. 2. The semiconductor wafer transport method according to claim 1, wherein the non-contact chuck is disposed so that the optical sensor faces the outer periphery of the first main surface.

5. 2. The semiconductor wafer transport method according to claim 1, wherein the optical sensor is a reflective sensor.

6. the optical sensor has a light source that irradiates the first main surface with light; 2. The semiconductor wafer transport method according to claim 1, wherein the light source has a red semiconductor laser.

7. the optical sensor has a light source that irradiates the first main surface with light; 2. The semiconductor wafer transport method according to claim 1, wherein the light source irradiates the first main surface with light having a wavelength of 640 nm or more and 770 nm or less.

8. 2. The semiconductor wafer transport method according to claim 1, wherein the semiconductor wafer is any one of a silicon wafer, an SOI wafer, a silicon carbide wafer, a sapphire wafer, a gallium nitride wafer, a gallium phosphide wafer, and a gallium arsenide wafer.

9. 2. The semiconductor wafer transport method according to claim 1, wherein an electric circuit pattern is formed on either the first main surface or a second main surface of the semiconductor wafer opposite to the first main surface.

10. 10. The semiconductor wafer transport method according to claim 9, wherein the electric circuit pattern is formed on the first main surface.

11. and a step of measuring a third intensity of the light reflected by the first main surface while the optical sensor irradiates the first main surface with light during the process of bringing the non-contact chuck closer to the first main surface, 2. The semiconductor wafer transport method according to claim 1, wherein in the step of detaching the non-contact chuck from the semiconductor wafer, it is determined that the non-contact chuck holds the semiconductor wafer when the third strength becomes smaller than the first strength.

12. a non-contact chuck provided with an optical sensor arranged to face the first main surface of the semiconductor wafer; the non-contact chuck holds the semiconductor wafer in a non-contact state by bringing the non-contact chuck close to the first main surface and blowing gas thereon, and is detached from the semiconductor wafer by moving the non-contact chuck away from the first main surface; the optical sensor irradiates the first main surface with light and measures a first intensity, which is the intensity of light reflected by the first main surface, before the non-contact chuck is brought close to the first main surface, and irradiates the first main surface with light and measures a second intensity, which is the intensity of light reflected by the first main surface, while the non-contact chuck is being moved away from the first main surface; When the second intensity becomes the first intensity, it is determined that the non-contact chuck has been detached from the semiconductor wafer.

13. 13. The semiconductor wafer transfer device according to claim 12, wherein the non-contact chuck is a Bernoulli chuck or a cyclone chuck.

14. 13. The semiconductor wafer transport device according to claim 12, wherein the non-contact chuck is disposed so that the optical sensor faces a central portion of the first main surface.

15. 13. The semiconductor wafer transport device according to claim 12, wherein the non-contact chuck is disposed so that the optical sensor faces an outer periphery of the first main surface.

16. 13. The semiconductor wafer transport device according to claim 12, wherein the optical sensor is a reflective sensor.

17. the optical sensor has a light source that irradiates the first main surface with light; 13. The semiconductor wafer transport device according to claim 12, wherein the light source comprises a red semiconductor laser.

18. the optical sensor has a light source that irradiates the first main surface with light; 13. The semiconductor wafer transport device according to claim 12, wherein the light source irradiates the first main surface with light having a wavelength of 640 nm or more and 770 nm or less.

19. the optical sensor irradiates the first main surface with light while the non-contact chuck is being brought closer to the first main surface, and measures a third intensity that is the intensity of the light reflected by the first main surface; 13. The semiconductor wafer transport device according to claim 12, wherein it is determined that the non-contact chuck holds the semiconductor wafer when the third strength is smaller than the first strength.

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