Wafer transfer device

Abstract

The present invention provides a wafer transfer device including a transfer hand using adhesive pads, the wafer transfer device being capable of preventing an excessive load from being applied when a wafer is delivered and being capable of surely preventing positional deviation at the time of wafer transfer.　Provided is a wafer transfer device including a transfer hand for mounting and transferring a wafer. The wafer transfer device is characterized in that: the transfer hand 10 is provided with a plurality of adhesive pads 2 having adhesive force and a hand body 1; these adhesive pads are arranged so as to be positioned on the circumference of a virtual circle 3 on the hand body; and a wafer mounting surface 2a of each of the adhesive pads 2 is inclined so as to be lowered toward the center O of the virtual circle 3 with respect to a wafer w to be mounted.

Description

Wafer Transfer Device

[0001] The present invention relates to a wafer transfer device equipped with a transfer hand on which a wafer is placed and transferred.

[0002] In semiconductor manufacturing, performance is improving, including through microfabrication, while at the same time there is a demand for cost reduction through efficient manufacturing.

[0003] The manufacturing of semiconductors requires semiconductor manufacturing equipment to perform various processes on wafers, such as film deposition, exposure, development, and etching, as well as wafer transport devices to transport wafers between these processes. Wafer transport devices, in particular, must be able to transfer wafers quickly and accurately.

[0004] Generally, wafer transport devices include those equipped with a vacuum grip type transport hand that uses vacuum suction to hold the wafer (see, for example, Patent Document 1), those equipped with an edge grip type transport hand that mechanically holds the edge of the wafer (see Patent Document 2), and even those equipped with an adhesive grip type transport hand that holds the wafer with an adhesive pad that has adhesive force (see Patent Document 3).

[0005] Of these, edge grip type transfer hands can securely hold wafers but have the risk of damaging the wafers they hold, while vacuum grip type transfer hands can avoid mechanical contact with the wafer, but their response time for suction (holding) and release of the wafer is slower than other methods, making them less suitable for efficient semiconductor manufacturing.

[0006] On the other hand, adhesive gripping transfer hands that hold wafers with adhesive pads are thought to have fewer of the problems associated with the edge gripping and vacuum gripping methods described above, but are inevitably inferior to these methods in terms of securely holding the wafer.

[0007] JP 2022-108953 A JP 2005-123642 A JP 2012-059749 A

[0008] One way to make semiconductor manufacturing more efficient is to increase the number of wafers processed per unit time. In this regard, a wafer transfer device that uses an adhesive grip type transfer hand, which has excellent responsiveness when transferring (picking up) wafers, is advantageous.

[0009] Here, it is important to prevent wafer misalignment during wafer transport in transport hands using adhesive pads. In particular, as the speed of the transport hand increases to improve processing efficiency, acceleration also increases, resulting in greater forces being applied when the transport hand moves or stops. Therefore, when transporting wafers horizontally between processes in semiconductor manufacturing equipment, forces acting in the transport direction (inertial force, centrifugal force) can cause the wafer to shift position, affecting the exposure and development processes in the next process. Therefore, transport hands using adhesive pads must have increased wafer holding force.

[0010] However, simply increasing the adhesive strength by using adhesive pads with strong adhesive force, increasing the number of adhesive pads, or increasing the size of the adhesive pads results in applying excessive force when removing the wafer from the transfer hand during wafer transfer, particularly when moving the transfer hand vertically, which can cause problems such as deformation of the wafer or, in some cases, damage to the wafer.

[0011] Therefore, the inventors conducted a lot of trial and error in transporting and holding wafers using adhesive pads, and discovered that by tilting the wafer-mounting surface of the adhesive pad attached to the transport hand in a predetermined direction relative to the wafer, it is possible to fully exert adhesive force in the horizontal direction of the wafer while suppressing adhesive force in the vertical direction of the wafer to a certain extent, thereby solving the above-mentioned problems and completing the present invention.

[0012] Therefore, an object of the present invention is to provide a wafer transport device using a transport hand with an adhesive pad that can prevent excessive strain when transferring (picking up) a wafer and can reliably prevent positional deviation during wafer transport.

[0013] In other words, the present invention is a wafer transport device equipped with a transport hand for placing and transporting a wafer, wherein the transport hand comprises a plurality of adhesive pads having adhesive force and a hand body, and these adhesive pads are arranged so as to be positioned on the circumference of an imaginary circle on the hand body, and the wafer placement surface of each adhesive pad is inclined downward toward the center of the imaginary circle relative to the wafer to be placed.

[0014] In the wafer transport device of the present invention, the transport hand includes a hand body and a plurality of adhesive pads. These adhesive pads are arranged on the circumference of an imaginary circle on one surface of the hand body, and the wafer mounting surface of each adhesive pad is inclined downward toward the center of the imaginary circle of the hand body relative to the wafer being placed thereon. That is, when the hand body with the adhesive pads arranged thereon is viewed in cross section, the wafer mounting surfaces of each adhesive pad are inclined downward toward the center of the imaginary circle. In this case, the wafer mounting surfaces of the adhesive pads may be inclined linearly or curvedly toward the center of the imaginary circle. In this case, the inclination should be such that the slope of the line (straight or curved) along the wafer mounting surfaces of the adhesive pads toward the center of the imaginary circle is negative.

[0015] The wafer-mounting surfaces of these adhesive pads are inclined relative to the wafer being placed as described above to adjust the contact area with the wafer. By inclining the wafer-mounting surfaces of the adhesive pads downward toward the center of the imaginary circle on the hand body, the pads can withstand the forces (inertial force, centrifugal force) acting when transporting the wafer horizontally, preventing lateral shifting of the wafer without excessively reducing the horizontal gripping force (adhesive force). Meanwhile, the adhesive force in the vertical direction of the wafer can be somewhat suppressed by adjusting the contact area as described above. This reduces the load when moving the transport hand vertically to transfer the wafer (removing the wafer from the adhesive pad).

[0016] In this case, there are no particular restrictions on the inclination angle of the wafer mounting surface of the adhesive pad, but it is preferable that the wafer mounting surface of each adhesive pad be inclined downward at an angle of 1° to 5° toward the center of the imaginary circle on the hand body relative to the wafer being mounted. This level of inclination can fully exert the effect of maintaining the adhesive force in the horizontal direction of the wafer while somewhat suppressing the adhesive force in the vertical direction of the wafer. Note that this inclination angle refers to the inclination of a line that runs along the wafer mounting surface of the adhesive pad toward the center of the imaginary circle. If this line is straight, it is the inclination of the line. If this line is curved, it refers to the inclination of the tangent to the curve.

[0017] In the present invention, unless otherwise specified, the horizontal and vertical directions are based on the wafer placed on the transport hand. In other words, they refer to horizontal and vertical movements relative to the wafer surface. This also applies when the transport hand is used as the reference, and they are synonymous with horizontal and vertical movements relative to the surface of the hand body that constitutes the transport hand.

[0018] The number of adhesive pads arranged on the hand body may be more than one, but preferably three or more. These adhesive pads may be arranged so as to be positioned on the circumference of an imaginary circle on the hand body, and can be set appropriately depending on the movement of the transport hand, the size of the wafer, etc., for example, by making the distance between adjacent adhesive pads approximately equal or by making the distance between adjacent adhesive pads different.

[0019] The adhesive pad is not particularly limited, but it is preferable to use one made of a self-adhesive adhesive holding material. Suitable examples include those made of resins such as silicone rubber, ethylene-propylene-diene rubber (EPDM), butyl rubber, fluorine-based resins, urethane-based resins, and acrylic resins. Of these, it is preferable to use one that can exhibit van der Waals forces, a type of intermolecular force, at the interface with the wafer.

[0020] To ensure that the wafer mounting surface of the adhesive pad has the above-mentioned inclination angle, the adhesive pad itself may be provided with an inclined surface, so that the wafer mounting surface of the adhesive pad placed on the hand body is inclined downward toward the center of the imaginary circle, or one side surface of the hand body may be entirely or partially provided with an inclined surface that slopes downward toward the center of the imaginary circle, so that the wafer mounting surfaces of the adhesive pads placed on the hand body are each inclined as described above. Alternatively, a tilting jig with an inclined surface may be used, and the wafer mounting surfaces of the adhesive pads placed on the hand body may be tilted via this tilting jig. In particular, by providing the hand body with an inclined surface that slopes downward toward the center of the imaginary circle or by using a tilting jig with an inclined surface, the transport hand according to the present invention can be obtained with good reproducibility.

[0021] The wafer transport device of the present invention may be any device equipped with the transport hand described above, and the configuration of the device is not particularly limited, but it is preferable to have an appropriate combination of a horizontal drive device for moving the transport hand horizontally, a vertical drive device for moving the transport hand up and down vertically, and a rotation drive device for rotating the transport hand. This allows for accurate, reliable, and efficient transfer of wafers between various processes in semiconductor manufacturing, and loading and unloading of wafers into wafer cassettes, etc.

[0022] According to the present invention, in a wafer transport device using a transport hand with an adhesive pad, it is possible to control the vertical gripping force while maintaining the horizontal gripping force, thereby preventing excessive strain when transferring (pickup) the wafer and reliably preventing the wafer from shifting position during transport.

[0023] FIG. 1 is a schematic plan view of a transfer hand in a wafer transfer device of the present invention, showing a state in which a wafer is placed on the transfer hand. FIG. 2 is a schematic cross-sectional view showing the A-A cross section in FIG. 1. FIG. 3 is a schematic plan view showing the positions of adhesive pads in Experimental Examples 1 to 4, along with an imaginary circle on the hand body. FIG. 4 is a schematic diagram showing how the gripping force of the transfer hand in Experimental Examples 1 to 4 is evaluated. FIG. 4(A) shows the case where the horizontal gripping force is evaluated, and FIG. 4(B) shows the case where the vertical gripping force is evaluated. FIG. 5 is a graph showing the relationship between the inclination angle θ of the adhesive pad and the horizontal gripping force in Experimental Examples 1 to 3. FIG. 6 is a graph showing the relationship between the inclination angle θ of the adhesive pad and the vertical gripping force in Experimental Examples 1 to 3. FIG. 7 is a graph showing the relationship between the inclination angle θ of the adhesive pad and the horizontal and vertical gripping forces in Experimental Example 4. FIG. 8 is a graph showing the relationship between the contact area and the horizontal gripping force depending on the inclination angle θ of the adhesive pad in Experimental Example 4. FIG. 9 is a graph showing the relationship between the contact area and the vertical gripping force based on different inclination angles θ of the adhesive pads in Experimental Example 4.

[0024] The present invention will be described in more detail below with reference to the drawings. Note that the following is one embodiment of the present invention, and the present invention is not limited to this embodiment.

[0025] 1 shows an example of a transfer hand in a wafer transfer device of the present invention. This transfer hand 10 includes a hand body 1 having carriers 1a and 1b for transferring wafers w to and from a cassette or process chamber, a joint 1c connecting the carriers, and three adhesive pads 2 (2-1, 2-2, 2-3). These adhesive pads 2-1, 2-2, and 2-3 are arranged on the circumference of an imaginary circle 3 on the hand body 1. These adhesive pads 2 are made of silicone rubber, ethylene-propylene-diene rubber (EPDM), butyl rubber, fluorine-based resin, urethane-based resin, acrylic resin, or the like, and are self-adhesive, exhibiting van der Waals forces, a type of intermolecular force.

[0026] 2, i.e., as shown in a cross section including the hand body 1 and the adhesive pads 2, the hand body 1 has cutout portions 4 (4-1, 4-2, 4-3) formed at positions where the adhesive pads 2 (2-1, 2-2, 2-3) are to be disposed. The cutout portions 4 have inclined surfaces 4a (4-1a, 4-2a, 4-3a) that slope downward toward the center O of the imaginary circle 3 (toward the center O of the imaginary circle 3). The adhesive pads 2 vary depending on the type and size of the wafer. For example, when transporting a Si wafer w with a diameter of approximately 12 inches, a cylindrical adhesive pad 2 having a diameter of 5 mm and a height of 1 mm can be used. These pads are then attached to the inclined surfaces 4a of the corresponding cutout portions 4 using adhesive, double-sided tape, or the like. As a result, the wafer mounting surface 2a (2-1a, 2-2a, 2-3a) of each adhesive pad 2 (2-1, 2-2, 2-3) is inclined downward at an inclination angle θ toward the center O of the imaginary circle 3 of the hand body 1 (toward a point O' in the direction of the center O of the imaginary circle 3) relative to the wafer w to be mounted. In this case, the inclination angle θ is preferably about 1° to 5°.

[0027] 2 shows adhesive pad 2-1, but the same is true for the other adhesive pads 2-2 and 2-3, and the wafer mounting surfaces 2a of the adhesive pads 2-2 and 2-3 are inclined downward at an inclination angle θ toward the center O of the imaginary circle 3 of the hand body 1. Therefore, when a wafer w is placed on the wafer mounting surface 2a of each adhesive pad 2, not the entire wafer mounting surface 2a but only the area outside the radius r of the imaginary circle 3 is crushed by the weight of the wafer w, and a wafer contact area m is formed on part of the wafer mounting surface 2a.

[0028] By adjusting this wafer contact area m, the horizontal gripping force (adhesive force) is not reduced too much, and the forces (inertial force, centrifugal force) acting when the transport hand 10 is moved horizontally to transport the wafer in the horizontal direction can be withstood, preventing lateral displacement of the wafer during horizontal transport. At the same time, the load on the wafer can be reduced when the transport hand 10 is moved vertically to transfer the wafer (removing the wafer from the adhesive pad).

[0029] 1 and 2, the notch 4 having the inclined surface 4a is provided corresponding to the position where the adhesive pad 2 of the hand body 1 is to be placed, but for example, a cone-shaped inclined surface may be formed on the hand body 1, scraped away from the center O of the imaginary circle 3 on the hand body 1, or a tilting jig with an inclined surface may be separately prepared, and the adhesive pad may be placed via this inclined jig at the position where the adhesive pad 2 of the hand body 1 is to be placed. Furthermore, the wafer mounting surfaces of the adhesive pads themselves may be tilted so that the wafer mounting surface of each adhesive pad is lowered at an inclination angle θ toward the center of the imaginary circle relative to the wafer to be placed.

[0030] The wafer transfer device of the present invention may be systemized as a wafer transfer robot by including a horizontal drive device that moves the transfer hand 10 horizontally and a vertical drive device that moves the transfer hand 10 up and down vertically, thereby enabling wafers to be transferred between various processes in semiconductor manufacturing with precision, reliability, and efficiency.

[0031] The present invention will be specifically described below based on experimental examples.

[0032] (Experimental Example 1) The present invention will be specifically described below based on an experimental example. The following experiment was conducted to investigate the adhesive force (gripping force) in the horizontal and vertical directions of the adhesive pad 2 arranged on the hand body 1 depending on the inclination angle θ formed between the wafer mounting surface 2 a and the wafer w.

[0033] First, the transport hand in the wafer transport device used in the experiment was prepared to be the same as the transport hand 10 described above in Figures 1 and 2. However, in the transport hand 10' used in this experiment, to provide the adhesive pad 2 with an inclination angle θ, instead of providing a notch 4 in the hand main body 1, a tilting jig with an inclined surface was used, and the adhesive pad 2 was placed on the hand main body 1 via this tilting jig. In other words, the entire surface on one side of the hand main body 1 was flat (the carriers 1a, 1b and the joint portion 1c connecting them were all horizontal), and the adhesive pad 2 was placed on the hand main body 1 via a tilting jig with an inclined surface with an inclination angle θ, so that the wafer mounting surface 2a of each adhesive pad 2 was tilted downward at the inclination angle θ toward the center O of the imaginary circle 3 of the hand main body 1.

[0034] The adhesive pads 2 used here were self-adhesive and 3 mm square, measuring 3 mm long, 3 mm wide, and 1 mm high before the inclination angle θ was formed. As shown in Figure 3, these adhesive pads 2 were arranged on the circumference of an imaginary circle 3 with a diameter of 133 mm on the hand body 1. The backsides of the adhesive pads 2 were adhesively bonded to the wafer with the wafer-mounting surface 2a of each pad 2 tilting downward toward the center O of the imaginary circle 3 (toward a point O' in the direction of the center O of the imaginary circle 3) at an inclination angle θ. The central angle formed between adhesive pads 2-1 and 2-3 and the arc of the imaginary circle 3 was 110°. Similarly, the central angle between adhesive pads 2-1 and 2-2 was 110°, and the central angle between adhesive pads 2-2 and 2-3 was 140°.

[0035] For the experimental transport hand 10' prepared above, when the inclination angles θ of the three adhesive pads 2-1 to 2-3 were all 0°, all 1°, and all 3°, a test wafer (weight 120 g) made of Si single crystal with a diameter of φ12 inches and a thickness of 760 μm was placed on the adhesive pad 2, and the horizontal and vertical gripping forces (adhesive forces) were evaluated.

[0036] 4A, the experimental transfer hand 10' carrying the test wafer w was fixed on the test table 20, and a load measuring device (force gauge) 30 having a measurement axis 30a at its tip was placed directly beside the experimental transfer hand 10'. The measurement axis 30a was pressed against the test wafer w in the horizontal direction (x direction) to measure the load when the test wafer w moved away from the adhesive pad 2. Similarly, the experimental transfer hand 10' was fixed on the test table 20, and the load measuring device 30 was placed below the test table 20. The measurement axis 30a of the load measuring device 30 was pressed against the backside of the test wafer w in the vertical direction (y direction) between the carriers 1a and 1b of the hand body 1 to measure the load when the test wafer w moved away from the adhesive pad 2. Each measurement was carried out seven times, and the average values ​​were taken as the horizontal gripping force and the vertical gripping force. The results are shown in Table 1, and the average values ​​are graphed in Figures 5 and 6.

[0037]

[0038] Experimental Examples 2 and 3 Experimental Example 2 was conducted in the same manner as Experimental Example 1, except that the adhesive pad 2 had a size of 5 mm square (5 mm length x 5 mm width x 1 mm height), and Experimental Example 3 was conducted in the same manner as Experimental Example 1, except that the adhesive pad 2 had a size of 7 mm square (7 mm length x 7 mm width x 1 mm height). The horizontal and vertical gripping forces were measured in the same manner as described above. The results are shown in Tables 2 and 3, and average values ​​are plotted in graphs in Figures 5 and 6.

[0039]

[0040]

[0041] As can be seen from the results of Experimental Examples 1 to 3, by tilting the wafer-mounting surface of the adhesive pad downward at an inclination angle θ = 1° toward the center of the imaginary circle on the hand body, it was possible to significantly reduce both the horizontal and vertical gripping forces (adhesive forces) of the adhesive pad.

[0042] (Experimental Example 4) An experimental transport hand 10' according to Experimental Example 4 was prepared in the same manner as in Experimental Example 1, except that the adhesive pad 2 was cylindrical with a diameter of 5 mm and a height of 1 mm. In Experimental Example 4, the inclination angle θ of the adhesive pad 2 was set to 0°, 1°, 3°, and 5°. Then, the horizontal gripping force and the vertical gripping force were measured in the same manner as in Experimental Example 1. The results are shown in Table 4, and a graph of the average values ​​is summarized in FIG. 7.

[0043]

[0044] The results of Experimental Example 4 also showed that the horizontal and vertical gripping forces (adhesive forces) of the adhesive pad could be significantly reduced by tilting the wafer-mounting surface of the adhesive pad downward at an inclination angle θ = 1° toward the center of the imaginary circle on the hand body. It can also be said that the horizontal and vertical gripping forces (adhesive forces) of the adhesive pad were almost fully reduced (the effect was saturated) at an inclination angle θ = 3°.

[0045] In Experimental Example 4, the contact area between the adhesive pad 2 and the test wafer w was evaluated for different tilt angles θ. Specifically, as shown in FIG. 2 , the wafer contact area m was calculated for each adhesive pad 2, and the sum of these was used as the contact area between the adhesive pad 2 and the test wafer w. Since it was necessary to take an image to calculate the contact area, a glass wafer (weight 115 g) with a diameter of 12 inches and a thickness of 690 μm was used as the test wafer. Planar images of the test wafer w were taken from above with the test wafer w placed on the three adhesive pads 2, and the contact area was calculated using the image processing software ImageJ. The relationship between the contact area and the gripping force (adhesive force) based on the tilt angle θ was then graphed for both the horizontal and vertical directions. The results are shown in FIGS. 8 and 9.

[0046] The results in Figures 8 and 9 show that the contact area of ​​the adhesive pad and the gripping force (adhesive force) are proportional to each other in both the horizontal and vertical directions, and in particular the correlation coefficient is close to 1.

[0047] That is, according to the present invention, the wafer placement surface of the adhesive pad is tilted downward toward the center of the imaginary circle of the hand body relative to the wafer to be placed, and the horizontal and vertical gripping forces (adhesive forces) can be adjusted by changing the tilt angle θ. This prevents the wafer from slipping sideways without excessively reducing the horizontal gripping force (adhesive force), while at the same time suppressing the adhesive force of the wafer in the vertical direction to some extent, thereby reducing the load when moving the transport hand vertically to transfer the wafer (removing the wafer from the adhesive pad).

[0048] 1: hand body, 1a, 1b: carrier, 1c: joint part, 2 (2-1, 2-2, 2-3): adhesive pad, 2a (2-1a, 2-2a, 2-3a): wafer mounting surface, 3: imaginary circle, 4 (4-1, 4-2, 4-3): notch part, 4a (4-1a, 4-2a, 4-3a): inclined surface, 10, 10': transport hand, 20: test table, 30: load measuring instrument, w: wafer.

Claims

1. A wafer transport device equipped with a transport hand for placing and transporting a wafer, wherein the transport hand comprises a plurality of adhesive pads and a hand body, the adhesive pads being arranged so as to be positioned on the circumference of an imaginary circle on the hand body, and the wafer placement surface of each adhesive pad being inclined downward toward the center of the imaginary circle relative to the wafer to be placed.

2. A wafer transport device according to claim 1, wherein the wafer mounting surface of each adhesive pad is inclined downward at an angle of 1 to 5 degrees toward the center of the imaginary circle relative to the wafer to be mounted.

3. A wafer transport device as described in claim 1, wherein the hand body has an inclined surface that slopes downward toward the center of the imaginary circle, and the wafer placement surface of each adhesive pad is inclined, or the adhesive pad has an inclined surface that slopes downward toward the center of the imaginary circle, and the wafer placement surface of each adhesive pad is inclined, or the wafer placement surface of each adhesive pad arranged on the hand body is inclined via an inclined jig that has an inclined surface that slopes downward toward the center of the imaginary circle.

4. A wafer transport device according to any one of claims 1 to 3, comprising a horizontal drive device for moving the transport hand horizontally, a vertical drive device for moving the transport hand up and down vertically, and a rotation drive device for rotating the transport hand.

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