Ion implantation apparatus

Abstract

To shorten a time required from taking out a wafer from a cassette until starting an implantation process to the wafer, in an ion implantation apparatus in which a measuring instrument of a crystal orientation is disposed inside the ion implantation apparatus.SOLUTION: An ion implantation apparatus IM measures a crystal orientation of a wafer W, adjusts an inclination of the wafer W on the basis of a crystal orientation measurement result, and thereafter performs channeling ion implantation to the wafer W. A measurement position P3 for measuring the crystal orientation of the wafer W is provided between a first position P1 and a second position P2 on a transfer path of the wafer W. The apparatus comprises transfer units T1, T2 which transfer the wafer W in the order of the first position P1, the measurement position P3, and the second position P2 during an ion implantation process for the wafer W. The transfer units T1, T2 transfer the wafer W from the measurement position P3 toward the second position P2 until the crystal orientation measurement result of the wafer W is output.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an ion implantation apparatus that implants impurities into a wafer by irradiating the wafer with an ion beam. [Background technology]

[0002] Ion implantation equipment utilizes the channeling phenomenon to implant ions deeper into the wafer surface. Specifically, the ion beam irradiation angle onto the wafer surface is adjusted to align the wafer's crystal axis with the ion beam irradiation direction, and then ion implantation into the wafer is performed. This ion implantation process is called channeling ion implantation.

[0003] During wafer manufacturing processes, such as the slicing and polishing processes, manufacturing errors occur in the wafer's thickness within the plane. These errors cause the direction of the wafer's crystal axis (crystal orientation) to tilt by several degrees from the perpendicular direction to the wafer plane. Depending on the degree of error, it may be impossible to achieve the desired ion implantation process, even if the ion beam irradiation angle to the wafer plane is correctly adjusted.

[0004] Furthermore, silicon carbide epitaxial wafers, which are made by growing an epitaxial layer on a base wafer, have an off-angle of approximately 4 degrees. The reason for setting this off-angle is to avoid the effects of defects in the epitaxial layer. Base wafers with an off-angle are manufactured by slicing an ingot at an angle during the slicing process. As a result, the wafer surface and the crystal plane do not coincide, and even if there are no manufacturing errors in the wafer, the direction of the crystal axis is not necessarily perpendicular to the wafer surface.

[0005] Therefore, when channeling ion implantation is performed, the crystal orientation of the wafer is measured as disclosed in Patent Document 1 and Patent Document 2. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent Publication No. 2021-120944 [Patent Document 2] Special Publication 2007-520885 Summary of the Invention [Problem to be solved by the invention]

[0007] Although it depends on the measuring device used, it takes anywhere from several tens of seconds to several minutes for the crystal orientation measurement results to be output. If a crystal orientation measuring device is installed inside the ion implantation device, it takes longer to remove the wafer W to be processed from the cassette and perform the implantation process on that wafer W. This reduces the productivity of the ion implantation device.

[0008] The main objective of the present invention is to shorten the time required from removing a wafer from a cassette to starting the implantation process on the wafer in an ion implantation apparatus in which a crystal orientation measuring device is installed inside the ion implantation apparatus. [Means for solving the problem]

[0009] The ion implanter 1. An ion implantation apparatus that measures a crystal orientation of a wafer, adjusts a tilt of the wafer based on a result of the crystal orientation measurement, and then performs channeling ion implantation into the wafer, a measurement position for measuring a crystal orientation of the wafer is provided between a first position and a second position on the wafer transfer path, and a transfer unit is provided for transferring the wafer from the first position to the measurement position and then to the second position during ion implantation processing of the wafer; The transport unit transports the wafer from the measurement position toward the second position until the crystal orientation measurement result of the wafer is output.

[0010] The transport unit transports the wafer from the measurement position to the second position before the crystal orientation measurement results of the wafer are output, thereby shortening the time until the implantation process into the wafer can be started.

[0011] To further reduce wafer transport time, It is desirable that the transport unit transport another wafer to be processed next toward the measurement position before the crystal orientation measurement result of the wafer is output.

[0012] To simplify the configuration of the measuring instrument, It is desirable to provide an aligner at the measurement position for adjusting the position of the wafer in the circumferential direction.

[0013] When wafers are kept waiting until the measurement results are output, the effective time required for implantation is reduced. the second position is within a processing chamber in which an ion implantation process is performed on the wafer; It is desirable that the wafer wait at the second position until the crystal orientation measurement result of the wafer is output.

[0014] When incorporating an interlock function, It is desirable that the transport unit transports the wafer to the measurement position or the first position depending on the crystal orientation measurement result of the wafer. [Effects of the Invention]

[0015] The wafer is transported from the measurement position to the second position by the transport unit before the crystal orientation measurement results are output, thereby shortening the time it takes to remove the wafer from the cassette and start the implantation process. [Brief explanation of the drawings]

[0016] [Figure 1] Schematic plan view of an ion implantation device [Figure 2]Illustration of the platen position when transferring a wafer [Figure 3] An explanatory diagram of the platen position during ion implantation processing [Figure 4] 1 is a time chart showing an embodiment of wafer transport; [Figure 5] 10 is a time chart showing another embodiment of wafer transport; [Figure 6] 10 is a time chart showing another embodiment of wafer transfer; [Figure 7] 1 is a flowchart illustrating one embodiment of wafer transport. DETAILED DESCRIPTION OF THE INVENTION

[0017] FIG. 1 is a schematic plan view showing the periphery of a processing chamber 1 of an ion implantation apparatus IM. After explaining the transport path of the wafer W and the ion implantation process, the relationship with the crystal orientation measurement will be explained.

[0018] The cassettes 7a to 7d store a plurality of wafers W. The atmospheric robots 4a and 4b take out the wafers W from the cassettes 7a to 7d and transport them to the aligner 5. After the circumferential position of the wafer W is adjusted by the aligner 5, the atmospheric robots 4a and 4b transport the wafer W to the vacuum pre-chambers 3a and 3b. The spare vacuum chambers 3a and 3b allow the wafer W to be transported between the processing chamber 1 and the room where the aligner 5 is located, which have different vacuum degrees, by switching the vacuum degrees in the chambers. The floors of the vacuum preparatory chambers 3a and 3b are moved up and down in the direction of the paper by a drive mechanism (not shown). The up and down movement of the floors is performed after the chambers are switched from atmosphere to vacuum or from vacuum to atmosphere.

[0019] The processing chamber 1 is equipped with vacuum hands V1 and V2 that can independently rotate in the directions of the arrows shown in the figure. The vacuum hands V1 and V2 are equipped with gripping portions C1 and C2 that grip the periphery of the wafer W. The vacuum hands V1 and V2 grip the wafer W in the vacuum auxiliary chambers 3a and 3b and transport it to the platen 2.

[0020] When the wafer W is transferred from the vacuum hands V1 and V2 to the platen 2, the platen 2 is in a horizontal position as shown in FIG. The platen 2 is equipped with an electrostatic chuck E for holding the wafer W. After the wafer W is fixed to the platen 2 by the electrostatic chuck E, the posture of the platen 2 is adjusted by a tilt mechanism 11 for adjusting the inclination of the wafer W and a twist mechanism (not shown). 2 and 3 is a mechanism that adjusts the tilt of the platen 2 around the X-axis as the rotation axis. A twist mechanism (not shown) is a mechanism that adjusts the position of the wafer W in the circumferential direction by rotating the platen 2. The rotation axis of the tilt mechanism 11 may be the Y-axis instead of the X-axis.

[0021] A drive shaft 12 is attached to the platen 2, which moves the platen 2 back and forth in the Y-axis direction by a drive source (not shown). The ion beam IB in FIG. 3 is an ion beam whose cross section in the XY plane is spot-shaped. It is scanned in the X-axis direction by electrostatic or magnetic fields. The scanning width is set to a dimension equal to or greater than the diameter of the wafer W. 3, after the attitude of the platen 2 is adjusted, the surface to be processed of the wafer W is moved forward across the ion beam IB by the forward movement of the drive shaft 12. In this way, ion implantation processing is performed on the wafer W. Instead of the above-described ion beam IB, a ribbon-shaped ion beam that is approximately rectangular and long in the X-axis direction and short in the Y-axis direction in a cross section on the XY plane may be used.

[0022] 1 to 3 is an example. The numbers of vacuum hands V1, V2, vacuum spare chambers 3a, 3b, atmospheric robots 4a, 4b, and cassettes 7a-7d are not limited to those shown in the drawings, and a configuration in which one of each is provided may also be used. The control device C is a device that controls each part of the ion implantation device IM, and is provided with functions necessary for controlling each part, such as a calculation unit and a memory unit.

[0023] The crystal orientation of the wafer W is measured, for example, at a position where the aligner 5 is placed. If the position of the aligner 5 is set to measurement position P3, the aligner 5 can also be used as a support base for the wafer W during measurement. In addition, the rotation mechanism of the aligner 5 can be used to adjust the circumferential position of the wafer W during measurement. In this way, it is possible to use part of the configuration and functions of the aligner 5 in the measuring device, which makes it possible to simplify the configuration of the measuring device.

[0024] The measuring device may be, for example, an X-ray diffraction device. Measurement methods include detecting reflected or transmitted light from the wafer at multiple points by changing the position of the detector, or detecting it with a two-dimensional detector at a fixed position.

[0025] The flatness of the wafer W surface to be measured is not necessarily constant. It varies slightly from wafer to wafer, and some types of wafers W may have significant warpage. If crystal orientation measurement is performed on a warped wafer W, there is a concern that the direction of the crystal axis may not be measured correctly. Furthermore, even if measurement is possible, if there is a large difference in the flatness of the wafer W between the time of measurement and the time of ion implantation processing, accurate channeling ion implantation will be difficult.

[0026] As a countermeasure, an electrostatic chuck may be provided on the measurement stage on which the wafer W is placed, and the crystal orientation may be measured in a state where the warpage of the wafer W is improved by adsorbing the wafer W to the electrostatic chuck. If the measuring instrument is equipped with an electrostatic chuck, the chucking force of the electrostatic chuck is set to the same level during measurement and ion implantation processing. This allows the warpage of the wafer W held to the electrostatic chuck to be corrected to the same level, thereby achieving more accurate alignment of the crystal orientation and the ion beam irradiation angle.

[0027] The measuring device may not use X-rays. For example, light emitted from a mercury lamp, halogen lamp, or helium-neon laser is irradiated onto the wafer W through optical elements such as a wavelength plate or polarizing plate. One example of a measuring device is one that measures the reflected light from the wafer W or the transmitted light that has passed through the wafer W, and identifies the crystal orientation from the intensity of the measured light.

[0028] On the transport path of wafers W from cassettes 7a-7d in which wafers W are stored to platen 2 in which the injection posture of wafers W is adjusted, arbitrary positions on either side of measurement position P3 are designated as first position P1 and second position P2. In the configuration example of FIGS. 1 and 2, the first position P1 is where the cassettes 7a-7d are arranged, and the second position P2 is where the platen 2 is arranged.

[0029] The transfer section is a section that transfers the wafer W from the first position P1 to the second position P2 via the measurement position P3. In the configuration example of Fig. 1, there are two transfer sections T1 and T2: transfer section T1 consisting of the atmospheric robot 4a, the vacuum reserve chamber 3a, and the vacuum hand V1, and transfer section T2 consisting of the atmospheric robot 4b, the vacuum reserve chamber 3b, and the vacuum hand V2. Which of the transfer parts T1 and T2 is to be used is selected for each of the cassettes 7a-7d from which the wafers W are to be taken out. 1 is an example. For example, when a wafer W is transferred in the order of the atmospheric robot 4a, the aligner 5, the atmospheric robot 4b, the vacuum auxiliary chamber 3b, the vacuum hand V2, and the platen 2, the atmospheric robot 4a, the atmospheric robot 4b, the vacuum auxiliary chamber 3b, and the vacuum hand V2 constitute the transfer units. The configuration of the transport unit is changed depending on the first position P1, the measurement position P3, and the second position P2 on the transport path.

[0030] When the wafer W is transported from the first position P1 to the measurement position P3, the crystal orientation is measured. After the crystal orientation is measured, the wafer W starts to be transported from the measurement position P3 to the second position P2 before the measurement result is output. The wafer W is advanced to the end of the transport path during the waiting time until the measurement results are output, thereby shortening the transport time of the wafer W compared to a configuration in which transport of the wafer W begins after the measurement results are output.

[0031] 4 and 5 are time charts showing an example of the transportation of the wafer W. Here, the first position P1 is the arrangement position of the cassettes 7a-7d, and the second position P2 is the arrangement position of the platen 2. Furthermore, the measurement position P3 is the arrangement position of the aligner 5.

[0032] 4, the time required for the crystal orientation measurement results to be output is longer than the transport time required for the wafer W to be transported from measurement position P3 to platen 2. After the wafer W reaches platen 2, it waits on platen 2 until the measurement results are output. After the measurement results are output, the tilt angle of platen 2 is adjusted by tilt mechanism 11 in accordance with the information on the measurement results, and the ion implantation process is carried out.

[0033] In order to start the implantation process as early as possible, it is desirable that the standby position of the wafer W be inside the processing chamber 1. In particular, if the standby position of the wafer W is on the platen 2, the time until the implantation process starts is minimized. The processing chamber 1 here includes the vacuum spare chambers 3a and 3b after the atmosphere inside the chamber has been changed to the same degree of vacuum as the processing chamber 1. When the transport time of the wafer W on the transport path of the wafer W after the measurement position P3 is considered, the time required for changing the pressure in the vacuum auxiliary chambers 3a and 3b from the atmospheric air to a vacuum atmosphere becomes relatively long. For this reason, it is desirable that the standby position of the wafer W be inside the processing chamber 1, which will be the location after the pressure change operation.

[0034] In a single-wafer ion implantation system, ion implantation processing is performed one by one on wafers W. As shown in the configuration example of Fig. 4, before the measurement results of the wafer W for which crystal orientation measurement has been performed are output, transportation of another wafer W (wafer 2) to be the next target of ion implantation processing is started from first position P1 (position of cassettes 7a-7d) to measurement position P3 (position of aligner 5). By transporting the next wafer W (wafer 2) to be measured to measurement position P3 in advance, crystal orientation measurement can be started early, thereby shortening the time until the implantation process into wafer W begins.

[0035] In Figure 5, the time from the end of crystal orientation measurement until the measurement results are output is shorter than the transport time until the wafer W is transported from measurement position P3 (position of aligner 5) to second position P2 (position of platen 2). The measurement results are output before the wafer W reaches platen 2. Once the wafer W reaches platen 2, the tilt angle of platen 2 is immediately adjusted based on the measurement results, and ion implantation processing is performed.

[0036] The ion implanter IM may have an interlock function based on the crystal orientation measurement results. In the time chart shown in FIG. 6, a determination is made as to whether the crystal orientation measurement results are normal. This determination is made, for example, by determining whether the angle of the crystal orientation, which is a reference, exceeds a set tolerance range. Specifically, the reference angle is set to 4°, and the tolerance range is ±0.5°. If the measurement result is output as 4.7°, the measurement is determined to be incorrect.

[0037] The measurement errors described above occur due to misalignment of the measuring device, which can be caused by misplacement of the measuring device or collision with the measuring device during maintenance of the ion implanter IM. 6, if it is determined that there is an error in the measurement, the wafer W (wafer 1) is transported from the platen 2 to one of the cassettes 7a-7d and then collected. After that, an operator of the ion implantation system IM adjusts the position of the measuring device. If another wafer W (wafer 2) is placed at measurement position P3, it is not possible to measure the crystal orientation of the wafer W (wafer 1) again after the wafer W (wafer 1) is retrieved. Therefore, when determining the measurement results, the next wafer W (wafer 2) to be ion implanted, which is placed in the aligner 5, is also retrieved into cassettes 7a-7d.

[0038] If there is any error in the measurement process, the cause of the error may be eliminated when the measurement is retaken, so the wafer W (wafer 1) may be returned from the position of the platen 2 to the position of the aligner 5 and the crystal orientation measurement may be performed again. In this case, at the same time that the wafer W is transported to the position of the aligner 5, another wafer W (wafer 2) which is to be subjected to the next ion implantation process and which is placed at the position of the aligner 5 is retrieved into one of the cassettes 7a-7d.

[0039] In order to detect such measurement errors, the measurement results may be judged each time the crystal orientation of a wafer W is measured. However, since the main cause is misalignment of the measuring device, most of the wafers W that are judged to be erroneous are wafers W that are measured immediately after the start of the ion implantation process. For this reason, the measurement results may be judged only when the crystal orientation is measured for the first time after the ion implantation device IM is stopped.

[0040] When a measurement error is detected, returning the wafer W to a predetermined location complicates the transport control of the wafer W. To avoid complicating the transport control, the wafer W may be made to wait at the measurement position P3 until the measurement result is determined. However, if the wafer W is made to wait each time crystal orientation measurement of the wafer W is performed, it is not possible to shorten the time until the start of implantation processing of the wafer W. For this reason, the wafer W may be made to wait at the measurement position P3 only when processing the first wafer W after the apparatus has been stopped.

[0041] FIG. 7 is a flow chart illustrating one embodiment of wafer transport. The transfer of the wafer W is started (S1), and the crystal orientation is measured at the measurement position P3 (S2). Next, it is determined whether the wafer W is the first wafer W to be measured after the apparatus is stopped (S3). If the wafer W is not the first wafer W, the wafer W is transported to a second position P2 (S4). Then, the measurement results are output (S5), and the tilt angle of the wafer W is adjusted based on the measurement results (S6). Finally, the tilt-adjusted wafer W is subjected to ion implantation processing (S7).

[0042] On the other hand, if the wafer W is the first wafer W to be measured after the equipment is stopped, the wafer W waits at the measurement position P3 (S8). After that, the measurement result is output (S5), and it is determined whether the crystal orientation measurement is normal or incorrect (S9). If the determination is normal, the wafer W is transferred to the platen 2 (S10), the tilt angle of the wafer W is adjusted (S6), and the ion implantation process is performed (S7). Conversely, if the crystal orientation measurement is determined to be incorrect, the orientation angle of the wafer W is measured again, or the position of the measuring device is adjusted (S11).

[0043] In the above embodiment, the positional deviation of the measuring device is indirectly detected based on the results of crystal orientation measurement, but a method of directly detecting the positional deviation of the measuring device may also be employed. For example, a light-receiving and light-emitting sensor is provided to optically detect the position of the measuring device, and if the measuring device blocks light, it is determined that there is a positional deviation.Alternatively, the displacement of the measuring device may be measured with a laser displacement meter to determine whether or not there is a positional deviation. In the above embodiment, the control of the transfer of the wafer W and the determination of the measurement results are carried out by the control device C shown in FIG.

[0044] The crystal orientation measuring device may be located in a location other than the aligner 5 as long as it is located inside the ion implantation device IM. For example, it may be located inside the processing chamber 1 or at the position of the cassettes 7a-7d. When the measuring device is located at the position of the cassettes 7a-7d, one of the cassettes is removed and the measuring device is placed in its place. The inside of the ion implanter IM refers to a position on the transport path of the wafer W from the cassettes 7a-7d to the platen 2 where the implantation posture of the wafer W is adjusted in the ion implanter IM. Even if a measuring device is externally attached to the ion implanter IM, as long as it is on the transport path of the wafer W described above, it falls under the ion implanter IM targeted by the present invention.

[0045] Furthermore, the present invention is not limited to the above-described embodiment, and it goes without saying that various modifications are possible without departing from the spirit of the present invention. [Explanation of symbols]

[0046] IM Ion Implantation Equipment W wafer 3a, 3b Vacuum preliminary chamber 5 Aligners P1 First position P2 Second position P3 measurement position T1, T2 transport section

Claims

1. 1. An ion implantation apparatus that measures a crystal orientation of a wafer, adjusts a tilt of the wafer based on a result of the crystal orientation measurement, and then performs channeling ion implantation into the wafer, a measurement position for measuring a crystal orientation of the wafer is provided between a first position and a second position on the wafer transfer path, and a transfer unit is provided for transferring the wafer from the first position to the measurement position and then to the second position during ion implantation processing of the wafer; The transport unit transports the wafer from the measurement position to the second position before a crystal orientation measurement result of the wafer is output.

2. 2. The ion implantation apparatus according to claim 1, wherein the transport unit transports another wafer to be processed next to the measurement position before the crystal orientation measurement result of the wafer is output.

3. 3. The ion implantation apparatus according to claim 1, further comprising an aligner at the measurement position for adjusting the position of the wafer in the circumferential direction.

4. the second position is within a processing chamber in which an ion implantation process is performed on the wafer; 3. The ion implantation apparatus according to claim 1, wherein the wafer waits at the second position until a crystal orientation measurement result of the wafer is output.

5. 3. The ion implantation apparatus according to claim 1, wherein the transport unit transports the wafer to the measurement position or the first position depending on a result of measurement of the crystal orientation of the wafer.

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