Monitoring method and monitoring device for amount of charge on surface of silicon wafer

Abstract

To provide a monitoring method and a monitoring device for an amount of charge on a surface of a silicon wafer which are capable of monitoring the amount of charge on the surface of the silicon wafer when the silicon wafer is transferred into a container.SOLUTION: A method for monitoring an amount of charge on a surface of a silicon wafer by measuring the amount of charge on the surface of the silicon wafer when the silicon wafer is transferred into a container measures the amount of charge on a portion of the silicon wafer that is exposed from the container when the silicon wafer is transferred into the container, thereby monitoring the amount of charge on the surface of the silicon wafer. A device for monitoring the amount of charge on the surface of the silicon wafer by measuring the amount of charge on the surface of the silicon wafer when the silicon wafer is transferred into the container includes a measurement unit capable of measuring the amount of charge on the portion of the silicon wafer that is exposed from the container when the silicon wafer is transferred into the container.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method and an apparatus for monitoring the amount of charge on the surface of a silicon wafer. [Background technology]

[0002] In general, when silicon wafers are shipped, they are accommodated in a container (for example, a Front Open Shipping Box (FOSB)). A transfer machine is used to transfer the silicon wafers to the container.

[0003] At this time, if the container is charged, the amount of charge on the surface of the silicon wafer also increases. If the surface of the silicon wafer is charged, electrons may move between the pusher and the surface of the silicon wafer through the atmosphere. The sudden movement of electrons is called a spark. If a spark occurs between the silicon wafer and the pusher, metal atoms contained in the pusher may be scattered onto the surface of the silicon wafer, resulting in metal contamination of the surface of the silicon wafer.

[0004] For example, Patent Document 1 proposes a method for removing the charge on the surface of a silicon wafer. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2009-146626 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, since the method of Patent Document 1 is a static elimination method, it is difficult to monitor the amount of charge on the surface of the silicon wafer. Therefore, if static elimination is not performed sufficiently, there is a risk that silicon wafers with sparks generated thereon may be shipped.

[0007] On the other hand, the container has a multi-tiered basket structure with many shelves to accommodate many silicon wafers W, and it was difficult to measure the charge amount of each silicon wafer by moving a device capable of measuring the charge amount inside the container. In addition, since the transfer to the container is the final process, monitoring thereafter was also difficult.

[0008] SUMMARY OF THE PRESENT DISCLOSURE ... An object of the present invention is to provide a method and device for monitoring the amount of charge on the surface of a silicon wafer, which is capable of monitoring the amount of charge on the surface of a silicon wafer when it is transferred to a container. [Means for solving the problem]

[0009] The gist and configuration of the present invention are as follows. (1) A method for monitoring an amount of charge on a surface of a silicon wafer by measuring an amount of charge on the surface of the silicon wafer when the silicon wafer is transferred to a container, comprising the steps of: A method for monitoring the amount of charge on a surface of a silicon wafer, comprising: measuring the amount of charge on a portion of the silicon wafer exposed from the container using a measuring unit when the silicon wafer is transferred to the container, thereby monitoring the amount of charge on the surface of the silicon wafer.

[0010] (2) constantly or at appropriate times, measuring the amount of charge on the surface of the silicon wafer using the measuring unit; The method for monitoring the amount of charge on the surface of a silicon wafer according to (1) above, wherein an alarm is issued by an alarm when the amount of charge on the surface of the silicon wafer exceeds a set threshold value or reaches the threshold value.

[0011] (3) An apparatus for monitoring the amount of charge on a surface of a silicon wafer by measuring the amount of charge on the surface of the silicon wafer when the silicon wafer is transferred to a container, comprising: A monitoring device for the amount of charge on a surface of a silicon wafer, comprising: a measuring unit capable of measuring the amount of charge on a portion of the silicon wafer exposed from a container when the silicon wafer is transferred to the container.

[0012] (4) The measurement unit is configured to be capable of constantly or periodically measuring the amount of charge on the surface of the silicon wafer; The monitoring device for the amount of charge on the surface of a silicon wafer according to (3) above, further comprising an alarm that issues an alarm when the amount of charge on the surface of the silicon wafer exceeds a set threshold value or reaches the threshold value. Effect of the Invention

[0013] According to the present invention, it is possible to provide a method and an apparatus for monitoring the amount of charge on the surface of a silicon wafer, which are capable of monitoring the amount of charge on the surface of a silicon wafer when the silicon wafer is transferred to a container. [Brief description of the drawings]

[0014] [Figure 1] 1 is a schematic side view of a monitoring device for the amount of charge on the surface of a silicon wafer. [Diagram 2] 1 is a cross-sectional view of a monitoring device for the amount of charge on the surface of a silicon wafer. [Diagram 3] FIG. 2 is a top view of a monitor for the amount of charge on the surface of a silicon wafer. [Figure 4] FIG. 1 is a diagram showing an apparatus used in the examples. [Diagram 5] FIG. 1 shows the results of an example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0016] <Monitoring device for the amount of charge on the surface of silicon wafers> An example of a monitoring device for the amount of charge on a surface of a silicon wafer according to one embodiment of the present invention will be described below. Fig. 1 is a schematic side view of the monitoring device for the amount of charge on a surface of a silicon wafer. Fig. 2 is a cross-sectional view of the monitoring device for the amount of charge on a surface of a silicon wafer. Fig. 3 is a top view of the monitoring device for the amount of charge on a surface of a silicon wafer.

[0017] When the silicon wafers W are shipped, they are moved horizontally by a transfer machine 4 and transferred into a shipping container 3 one by one.

[0018] As shown in FIG. 1 and FIG. 2, the monitoring device 1 of this embodiment includes a measuring unit 2. The measuring unit 2 can measure the amount of charge at a portion of the silicon wafer W exposed from the shipping container 3 (a portion exposed outside the shipping container 3 when viewed from a direction perpendicular to the surface of the silicon wafer W) when the silicon wafer W is transferred to the shipping container 3 (when a part of the silicon wafer W is located inside the shipping container 3 and the remaining part is located outside the shipping container 3). The measuring unit 2 can be any known device as long as it can measure the amount of charge on the surface of the silicon wafer W. In this example, the measuring unit 2 is an electrometer. Since the electric potential increases as the amount of charge increases, the amount of charge can be grasped by measuring the electric potential of the silicon wafer W.

[0019] In this example, the measurement unit 2 is configured to be able to measure the amount of charge on the surface of the silicon wafer W constantly or at any time.

[0020] In this embodiment, the monitoring device 1 further includes an alarm 5. The alarm 5 is configured to issue an alarm when the charge amount on the surface of the silicon wafer W exceeds or reaches a set threshold. The alarm can be any known alarm, and can be issued by various methods such as light, sound, and vibration. The threshold can be set, for example, based on the charge amount (measured potential) when a spark occurs from past data or the like (the charge amount may be used as the threshold as it is, or a predetermined calculation such as multiplying it by a coefficient for safer management). In the illustrated example, the alarm 5 is connected to the measurement unit 2 by wire, but it may also be connected wirelessly.

[0021] In this example, the shipping container 3 is a FOSB. For example, a FOSB partially made of resin can be used. The resin material of the FOSB is not particularly limited, but polycarbonate can be exemplified. In place of the shipping container 3, a container such as a FOUP (Front Opening Unified Pod) can also be used. For example, a FOUP partially made of resin can be used.

[0022] The transfer machine 4 has an arm 4a extending in the horizontal direction. Pads 4b (for supporting the end faces of the silicon wafers W) are provided on both ends of the arm 4a. The transfer machine 4 also has a pusher 4c. The arm 4a can move sequentially to positions corresponding to each shelf of the multi-tiered basket in the shipping container 3, and the silicon wafers W are pushed out by the pusher 4c to accommodate the silicon wafers W one by one on each shelf. The silicon wafers W are accommodated in order from the top shelf of the shelf. The pusher 4c is provided with a pad 4b (for supporting the other end face (the side that will enter the shipping container 3 later) of the silicon wafer W). The arm 4a and the pad 4b are made of resin in this example. The pusher 4c is made of aluminum in this example. The silicon wafer W is transferred horizontally into the shipping container 3 while being supported by a pair of pads 4b as shown in the figure. Since the material of the arm 4a and the pad 4b, which are the members surrounding the silicon wafer W, is made of insulating resin, the silicon wafer W may become charged, and the above-mentioned spark may occur between the silicon wafer W and the pusher 4c, which is made of aluminum.

[0023] <Method for monitoring the amount of charge on the surface of a silicon wafer> A method for monitoring the amount of charge on the surface of a silicon wafer according to an embodiment of the present invention will be described below. Although not particularly limited, the monitoring method of the present embodiment can be implemented using the monitoring device of the above embodiment.

[0024] The method of this embodiment is a method of measuring the amount of charge on the surface of the silicon wafer W when the silicon wafer W is transferred to the shipping container 3, and monitoring the amount of charge on the surface of the silicon wafer W. In the method of this embodiment, the amount of charge on the surface of the silicon wafer W is monitored by measuring the amount of charge on a portion of the silicon wafer W exposed from the shipping container 3 using the measurement unit 2 when the silicon wafer W is transferred to the shipping container 3.

[0025] In the method of the present embodiment, it is preferable to constantly or appropriately measure the amount of charge on the surface of the silicon wafer W using the measuring unit 2, and to issue an alarm by the alarm device 5 when the amount of charge on the surface of the silicon wafer W exceeds or reaches a set threshold value.

[0026] <Action and effect> As a result of intensive research by the present inventors to solve the above problems, it was found that, as shown in the examples described later, the charge amount on the surface of the silicon wafer W when it is transferred to the shipping container 3 is almost uniform within the plane. Then, it was found that if a portion of the silicon wafer W exposed from the shipping container 3 is measured when the silicon wafer W is transferred to the shipping container 3, the charge amount (measured potential) at that portion can be regarded as the charge amount (potential) at any point within the plane of the silicon wafer W.

[0027] First, regarding the apparatus, the monitoring device 1 for the charge amount on the surface of the silicon wafer W in the above embodiment of the present invention is equipped with a measurement unit 2 that can measure the charge amount of the portion of the silicon wafer W that is exposed from the shipping container 3 when the silicon wafer W is transferred to the shipping container 3. Therefore, the measurement unit 2 measures the charge amount of that portion and regards that charge amount as the charge amount at the portion where electrons are transferred between the silicon wafer W and the pusher 4c, thereby making it possible to monitor the charge amount on the surface of the silicon wafer W when it is transferred to the shipping container 3. As in the above embodiment of the device, it is preferable to further include an alarm 5 that constantly or appropriately measures the charge amount on the surface of the silicon wafer W using the measurement unit 2 and issues an alarm when the charge amount on the surface of the silicon wafer W exceeds or reaches a set threshold value. This makes it possible to prevent silicon wafers W in which sparks may have occurred from being shipped by, for example, stopping the flow of the silicon wafer W in question when an alarm is issued.

[0028] Similarly, in the method for monitoring the amount of charge on the surface of the silicon wafer W according to the above embodiment of the present invention, the amount of charge on the surface of the silicon wafer W is monitored by using the measurement unit 2 to measure the amount of charge on the portion of the silicon wafer W that is exposed from the shipping container 3 when the silicon wafer W is transferred to the shipping container 3. By measuring the amount of charge on that portion using the measurement unit 2 and regarding the amount of charge as the amount of charge on the portion where electrons are transferred between the silicon wafer W and the pusher 4c, the amount of charge on the surface of the silicon wafer W when it is transferred to the shipping container 3 can be monitored. As in the embodiment of the method described above, it is preferable to constantly or periodically measure the charge amount on the surface of the silicon wafer W using the measuring unit 2, and to issue an alarm using the alarm device 5 when the charge amount on the surface of the silicon wafer W exceeds or reaches a set threshold value. This makes it possible to prevent silicon wafers W in which sparks may have occurred from being shipped by, for example, stopping the flow of the silicon wafers W in question when the alarm is issued.

[0029] Examples of the present invention will be described below, but the present invention is not limited to the following examples in any way. EXAMPLES

[0030] A test was conducted to measure the amount of charge on the surface of a silicon wafer when the silicon wafer was transferred to a FOSB. FIG. 4 is a diagram showing an apparatus used in the embodiment. The ionizer in the wafer transfer machine 4 was turned off, and then the FOSB was loaded onto the wafer transfer machine 4. The FOSB was then charged by the hand of an operator (wearing gloves). The potential of the FOSB was measured using a liquid crystal display voltmeter (Trek model 884, manufactured by Advanced Energy Japan). Next, the silicon wafer (p-type, diameter 300 mm) was neutralized to 0 kV. The amount of charge on the surface of the silicon wafer during transfer to the FOSB was measured at five points (positions A to E in FIG. 4) within the plane. The measurement was performed by moving the measuring unit 20 of a digital voltmeter (Trek model 347, manufactured by Advanced Energy Japan) to measuring positions A to E. In this test, a FOSB partially made of resin was used. The charge amount was measured by temporarily stopping the insertion of the silicon wafer into the FOSB at each of the following insertion distances: 0 mm, 100 mm, 150 mm, 200 mm, and 300 mm.

[0031] Fig. 5 is a diagram showing the results of the embodiment. As shown in Fig. 5, the amount of charge on the surface of the silicon wafer was the same at all measurement positions (positions A to E) on the surface of the silicon wafer. Furthermore, the amount of charge at each position in the silicon wafer surface increased with an increase in the insertion distance into the FOSB, but the amount of charge on the surface of the silicon wafer was the same at all measurement positions (positions A to E) on the surface of the silicon wafer at any insertion distance.

[0032] From the above results, it is understood that by measuring the charge amount at any position on the surface of the silicon wafer when the silicon wafer is transferred to the FOSB, the charge amount at that position can be regarded as the charge amount at another position. This makes it possible to monitor the charge amount on the surface of the silicon wafer when it is transferred to a shipping container, as explained in the above embodiment. [Explanation of symbols]

[0033] 1: A device for monitoring the amount of charge on the surface of a silicon wafer; 2: Measuring part, 3: shipping container, 4: Transfer machine, 5:Alarm, 20: Measuring part

Claims

1. A method for monitoring an amount of charge on a surface of a silicon wafer by measuring an amount of charge on the surface of the silicon wafer when the silicon wafer is transferred to a container, comprising the steps of: A method for monitoring the amount of charge on a surface of a silicon wafer, comprising: measuring the amount of charge on a portion of the silicon wafer exposed from the container using a measuring unit when the silicon wafer is transferred to the container, thereby monitoring the amount of charge on the surface of the silicon wafer.

2. The amount of charge on the surface of the silicon wafer is measured using the measurement unit at all times or at appropriate times, 2. The method for monitoring the amount of charge on the surface of a silicon wafer according to claim 1, further comprising the step of: issuing an alarm by an alarm when the amount of charge on the surface of the silicon wafer exceeds a set threshold value or reaches the threshold value.

3. An apparatus for monitoring the amount of charge on a surface of a silicon wafer by measuring the amount of charge on the surface of the silicon wafer when the silicon wafer is transferred to a container, comprising: A monitoring device for the amount of charge on a surface of a silicon wafer, comprising: a measuring unit capable of measuring the amount of charge on a portion of the silicon wafer exposed from a container when the silicon wafer is transferred to the container.

4. The measurement unit is configured to be capable of measuring the amount of charge on the surface of the silicon wafer at all times or at any time, 4. The monitoring device for the amount of charge on the surface of a silicon wafer according to claim 3, further comprising an alarm that issues an alarm when the amount of charge on the surface of the silicon wafer exceeds a set threshold value or reaches the threshold value.

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