Ion implantation device

Abstract

To enable safe take-out of a processed wafer.SOLUTION: An ion implantation device IM is a single-wafer type ion implantation device IM in which a wafer W is taken out one by one from cassettes 3a to 3d storing multiple wafers W, transported to a processing chamber 1 through vacuum reserve chambers 6 and 7, and ion implantation processing is performed on the wafers W. A waiting portion T is provided between the processing chamber 1 and the cassettes 3a to 3d to store the wafers W on which the implantation processing has been performed.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] In ion implantation equipment that uses ion beams with MeV-level energy, the collision of the ion beam with components generates radiation such as gamma rays, X-rays, and neutron rays. Various measures are taken to prevent such radiation from leaking outside the equipment.

[0003] Patent Document 1 proposes that neutron scattering members made of materials with high contents of hydrogen and boron, which have a large neutron scattering effect, be placed primarily in locations where the neutron dose rate is relatively high.

[0004] Patent Document 2 proposes placing low-emission inserts made of amorphous carbon, diamond-like carbon, pyrolytic graphite, silicon carbide, or the like in the beamline to reduce the number of neutrons generated when an ion beam collides. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent Publication No. 2020-155256 [Patent Document 2] Special table 2022-517366 Summary of the Invention [Problem to be solved by the invention]

[0006] Both Patent Document 1 and Patent Document 2 describe reducing radiation generated by collision between the ion beam and components arranged in the transport path of the ion beam, but make no mention of radiation generated from the wafer. For example, when a wafer is irradiated with an ion beam at or above a certain energy, radiation is generated from the wafer due to a decay phenomenon caused by a combination of the wafer material and the ion species implanted therein.

[0007] For example, when a silicon wafer is irradiated with a proton ion beam with an energy of 326 KeV or more, gamma rays are generated from the wafer due to β+ decay. The generation of gamma rays cannot be avoided depending on the implantation process.

[0008] When radioactive decay occurs, an unstable atomic nucleus emits radiation (alpha, beta, gamma, etc.) and changes into another stable atomic nucleus. This is not limited to the above example of proton implantation, but can also occur with other ion species and wafer combinations. When processed wafers that emit radiation are transported outside the apparatus, the radiation can have adverse effects on the human body depending on the amount of radiation.

[0009] An object of the present invention is to provide an ion implantation apparatus that enables safe removal of a processed wafer. [Means for solving the problem]

[0010] The ion implantation device is A single-wafer ion implantation apparatus which takes out a single wafer from a cassette storing a plurality of wafers, transports the wafers one by one to a processing chamber through a vacuum reserve chamber, and performs an ion implantation process on the wafers, Between the processing chamber and the cassette, there is a waiting section for holding the wafers that have been subjected to the implantation processing.

[0011] a control device that determines whether the wafer can be removed from the waiting section; It is preferable that the control device determines whether or not the wafer can be removed depending on the time elapsed since the implantation process of the wafer or the radiation dose in the waiting area.

[0012] The standby portion is preferably the cassette. Effect of the Invention

[0013] The amount of radiation emitted by a processed wafer decays over time, so by providing a waiting area between the processing chamber and the cassette to hold the processed wafer, the amount of radiation emitted from the wafer can be sufficiently reduced, allowing the wafer to be safely removed. [Brief description of the drawings]

[0014] [Figure 1] FIG. 2 is a schematic plan view showing the configuration around a processing chamber of the ion implantation apparatus. [Diagram 2] 11 is a flowchart showing an example of discharging a processed wafer. [Diagram 3] 13 is a flowchart showing another example of discharging a processed wafer. [Figure 4] FIG. 13 is a schematic plan view showing another configuration around the processing chamber of the ion implantation apparatus. [Diagram 5] FIG. 13 is a schematic plan view showing another configuration around the processing chamber of the ion implantation apparatus. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] 1 shows the configuration around a processing chamber 1 in a single-wafer ion implantation system IM. Cassettes 3a-3d store a plurality of wafers W. An atmospheric robot 9 and an aligner 4 are provided in a substrate transfer section 5. The wafer W taken out by the atmospheric robot 9 from any one of the cassettes 3a-3d is transferred to the aligner 4, where the circumferential orientation of the wafer W is aligned, and then transferred to the first vacuum reserve chamber 6.

[0016] When the wafer W is transferred to the first vacuum reserve chamber 6, the first vacuum reserve chamber 6 is sealed and the chamber is evacuated. When the evacuation of the first vacuum reserve chamber 6 is completed, the vacuum robot 8 removes the wafer W from the chamber and transfers the wafer W onto the platen 2. The illustrated position of the platen 2 is when the circular platen 2 is in an upright position. When receiving the wafer W from the vacuum robot 8, the platen 2 rotates 90° about the X-axis from the illustrated position so that the support surface of the wafer W becomes perpendicular to the Y-axis.

[0017] Into the processing chamber 1, an ion beam IB scanned in a direction parallel to the X-axis or a non-scanned ribbon-shaped ion beam IB is transported. After receiving the wafer W, the platen 2 is transported back and forth in a direction parallel to the Y axis by a driving source (not shown), whereby ion implantation processing is performed on the entire surface of the wafer W.

[0018] After the ion implantation process is completed, the vacuum robot 8 transports the processed wafer W on the platen 2 to the second vacuum reserve chamber 7. At this time, the second vacuum reserve chamber 7 is in the same vacuum atmosphere as the processing chamber 1. A standby section T is provided in the second vacuum reserve chamber 7. The waiting section T is configured, for example, with a shelf capable of transporting the wafer W in the ZX plane. This shelf may be a single level, or may be stacked in multiple levels in the Y-axis direction.

[0019] Once the processed wafer W has been transported to the waiting section T, an unprocessed wafer W is transported to the vacant platen 2. When the processed wafer W in the waiting section T satisfies a predetermined condition, the second vacuum reserve chamber 7 is purged with an inert gas such as nitrogen gas or argon gas. This changes the pressure inside the second vacuum reserve chamber 7 to the same pressure as that of the substrate transport section 5. After the pressure in the second vacuum reserve chamber 7 is changed, the atmospheric robot 9 transports the processed wafers W from the waiting area T to the cassettes 3a-3d.

[0020] The specified conditions for the wafer W in the waiting section T are conditions for ensuring safety when removing the wafer W, such as whether a specified time has elapsed since the implantation process and whether the amount of radiation emitted from the wafer W in the waiting section T is below a standard value.

[0021] Since the amount of radiation emitted by a processed wafer decays over time, the time required for the radiation to decay sufficiently is determined in advance by experiment, and this time is set as the predetermined time. Alternatively, the radiation emitted from the wafer W is measured with a dosimeter, and the actual measured value is compared with a standard value that ensures safety. When actually measuring the amount of radiation, a dosimeter is provided in the waiting section T or the second vacuum reserve chamber 7.

[0022] It is also possible to determine whether each processed wafer W satisfies a predetermined condition, and each time the condition is satisfied, the vacuum atmosphere of the second vacuum reserve chamber 7 is switched and the processed wafer W is returned to the cassette 3a-3d. However, if the time required for the ion implantation process on the wafer W is very short compared to the time required for the wafer W to satisfy the specified conditions in the waiting section T, this may cause problems in transporting the wafer W from the platen 2 to the waiting section T.

[0023] For example, if the standby section T has only one shelf, it will be physically impossible to place the next processed wafer W. Even if the standby section T has multiple shelves, if the timing of switching the vacuum atmosphere in the second vacuum reserve chamber 7 and the timing of transporting the next processed wafer W coincide, it will be impossible to transport the next processed wafer W to the standby section T. If this occurs, a long waiting time will occur before the next processed wafer W can be transported to the waiting section T, and the productivity of the ion implantation apparatus IM will decrease significantly.

[0024] Therefore, a shelf capable of storing all of one lot of wafers W (e.g., 25 wafers) to be subjected to ion implantation processing is provided in the waiting section T. Then, the time elapsed since the implantation processing of the last processed wafer W transported to the waiting section T is counted, and a determination is made as to whether the conditions are met for the last processed wafer W. In this way, a significant deterioration in the productivity of the ion implantation device IM can be avoided. Furthermore, if a determination of whether the conditions are met is made only for the last wafer W, rather than for each wafer W, the process of determining whether the conditions are met can be simplified.

[0025] The above determination is performed by the control device C of the ion implantation device IM. The control device C has a memory unit and a calculation unit. The memory unit stores time and radiation dose that serve as a comparison standard. As a specific example, when performing discrimination based on time, the control device C receives, as an input signal Si, information on the time when the ion implantation process for the last wafer was performed from the ion implantation device IM. The control device C counts the time using the reception of the input signal Si as a trigger, compares it with a reference time recorded in the memory unit, and discriminates whether or not the wafer W can be removed from the waiting section T. If it is determined that the wafer W can be removed, the control device C transmits an output signal So to the ion implantation device IM to transport the wafer W from the waiting section T.

[0026] When performing the determination based on the dose, the control device C receives the measurement result of the radiation dose measured by the ion implantation device IM and determines whether or not the wafer W can be removed by comparing it with a reference value recorded in the memory unit. If it is determined that the wafer W can be removed, the control device C transmits an output signal So to the ion implantation device IM to transport the wafer W from the waiting section T.

[0027] The input signal Si may include, for example, time information when the implantation process for each wafer W is completed and information indicating which wafer W is being implanted. The output signal So may be a control signal for controlling each part of the ion implanter IM. However, the present invention is not limited to this, and may be, for example, a signal for notifying an operator of the ion implanter IM of the discrimination result. In this case, the output signal So may be a signal for notifying an operator of the ion implanter IM on an operation display or by sound. Upon receiving such a notification, the operator of the ion implanter IM removes the wafer W.

[0028] 2 and 3 are flow charts assuming a case in which the time for ion implantation processing for the wafer W is very short compared to the time required for the wafer W to satisfy the predetermined conditions in the waiting section T. For example, it is assumed that the time for ion implantation processing is 30 to 40 seconds, and the time required for the wafer W to satisfy the predetermined conditions in the waiting section T is about 10 minutes.

[0029] The flowcharts of each figure will be briefly explained. In Fig. 2, wafers W are transported one by one to the platen 2 to undergo ion implantation processing, and the processed wafers W are transported sequentially to the waiting section T (process S1). Next, ion implantation is performed on the last wafer W stored in the target cassette 3a-3d, and the wafer W is transported to the waiting section T together with the wafers W processed up to that point (process S2).

[0030] In process S2, the time elapsed since the implantation process was performed on the last wafer W is measured (process S3). It is determined whether the time elapsed in process S3 is equal to or greater than a reference time (process S4). The reference time is the time required for the radiation emitted from the processed wafer W to fall below a predetermined dose.

[0031] In process S4, when the time elapsed since the end of the implantation process for the last wafer W becomes equal to or exceeds a reference time, the processed wafers W are sequentially unloaded from the waiting section T (process S5). When all the wafers W have been transferred to the standby section T at the time of carrying out the processes S3 and S4, the vacuum atmosphere in the second vacuum reserve chamber 7 may be switched.

[0032] In the flowchart of Fig. 3, the processes using the same reference numerals as in Fig. 2 are the same processes as in Fig. 2, and therefore the explanation of each process will be omitted. The difference from Fig. 2 is that in process S2, ion implantation processing is performed on the last wafer W in a given cassette 3a-3d, and after the last wafer W is transported to the waiting section T, the dose is measured in the waiting section T (process S11).

[0033] In process S12, it is determined whether the radiation measured in process S11 is equal to or less than a reference value. If the radiation amount in process S12 is equal to or less than the reference value, the processed wafer W is removed from the waiting section T (process S5).

[0034] 1, the standby unit T is provided in the second vacuum reserve chamber 7, but the location of the standby unit T is not limited to this location. For example, as shown in FIG. 4, the standby unit T may be provided in the processing chamber 1, and the processed wafer W may be transported thereto and kept on standby until a predetermined condition is satisfied.

[0035] 4, a waiting section T may be provided within the processing chamber 1, but when performing measurements with a dosimeter, there is a concern that the measurement may be erroneous due to radiation emitted from the wafer W being processed. For this reason, it is desirable to provide a partition to block radiation generated within the processing chamber and spatially separate the waiting section T. Further, the standby section T may be placed outside the processing chamber 1, and a room adjacent to the processing chamber 1 may be prepared separately from the second vacuum reserve chamber 7, and the standby section T may be provided in that room.

[0036] Furthermore, as shown in Fig. 5, the waiting section T may also serve as a cassette 3d. In Fig. 5, the cassette 3d is used as the shared object, but it may be any cassette that stores wafers W to be implanted, and is not limited to the cassette 3d. When any of the cassettes 3a-3d is used as the waiting section T, the cassette is already provided with a shelf for storing the wafers W, which is advantageous in that a special shelf for storing the processed wafers W in the waiting section T is not required.

[0037] When providing the standby section T in the second vacuum standby chamber 7, it is necessary to increase the volume of the second vacuum standby chamber 7. If the volume of the second vacuum standby chamber 7 is increased, there are concerns that it will take a longer time to switch the vacuum atmosphere in the standby chamber and that a large amount of purge gas will be required. However, when the cassettes 3a-3d are used both as the standby section T, the volume of the standby chamber can be small, so such concerns do not arise.

[0038] In the ion implantation device IM, the device housing is made of metal plates, so that leakage of radiation generated inside the housing to the outside of the housing is suppressed to a certain extent. However, if necessary, radiation shielding such as lead or iron may be partially provided on the housing wall. The apparatus housing accommodates substrate transport section 5 on which cassettes 3a-3d are attached and the area on the processing chamber 1 side thereof.

[0039] Since the cassettes 3a-3d are located outside the apparatus housing, if this area is also used as the waiting area T, there is a concern that radiation emitted from the wafers W may leak from the cassettes. Regarding this point, for example, the cassettes 3a-3d are covered with a shield made of acrylic resin, iron, etc. to prevent radiation leakage. Also, because the cassettes 3a-3d are placed in a sealed container when transported between devices due to particle issues, the above-mentioned shield may also serve as the housing of the wafer transport container.

[0040] 1, the configuration in which the standby section T is provided in the second vacuum reserve chamber 7 has been described, but the standby section T may be provided in the first vacuum reserve chamber 6. In addition, the ion implantation apparatus IM may be configured to include only one of the two vacuum reserve chambers 6, 7.

[0041] The location of the waiting section T is not limited to the locations described in Figures 1, 4, and 5. The waiting section T may be provided at any location on the transport path of the wafers W from the implantation process to storage in the cassettes 3a-3d, that is, from the process chamber 1 to the cassettes 3a-3d, depending on the configuration of the ion implantation apparatus IM.

[0042] It is not necessary that all of the cassettes 3a-3d store unprocessed wafers W. For example, one of the four cassettes 3a-3d may be left empty and used exclusively as a waiting section T.

[0043] Since radioactive decay occurs depending on the energy of the ion beam during ion implantation, the ion species, and the wafer material, it is not necessary to perform the discrimination process in the above embodiment depending on the implantation process. The discrimination process described in the above embodiment is performed on the assumption that radioactive decay occurs. If the process for determining whether or not radioactive decay has occurred is combined with the discrimination process described in the above embodiment, a determination is made as to whether or not to perform the discrimination process according to the contents of the injection process before the discrimination process described in the above embodiment. Specifically, in the flow charts of Figures 2 and 3, this determination is made before process S1.

[0044] For this judgment, a list consisting of ion beam energy, ion species, and wafer material is pre-recorded in the storage unit of the control device C, and the implantation process to be performed is compared with the list. If there is a match on the list, the discrimination process described in the above embodiment is performed. This judgment may be performed by the control device C, but the operator of the ion implantation device IM may make the judgment by referring to the list.

[0045] In the above embodiment, a configuration has been described in which the radiation dose is measured in the waiting section T and compared with a reference value recorded in the memory section of the control device C. However, the radiation dose in the external environment of the ion implantation device IM may be actually measured using a dosimeter, and this actual measurement value may be used as a reference value to be compared with the actual measurement value in the waiting section T.

[0046] 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]

[0047] 1 Processing Room 3a-3d cassette 6. First vacuum chamber 7 Second Vacuum Reserve Chamber IM Ion Implantation Equipment W wafer T Standby section C Control device

Claims

1. A single-wafer ion implantation apparatus which takes out a single wafer from a cassette storing a plurality of wafers, transports the wafers one by one to a processing chamber through a vacuum reserve chamber, and performs an ion implantation process on the wafers, the ion implantation apparatus further comprising a waiting section for holding the wafers that have been implanted between the vacuum reserve chamber and the cassette.

2. a control device that determines whether the wafer can be removed from the waiting section; 2. The ion implantation apparatus according to claim 1, wherein the control device determines whether or not the wafer can be removed depending on the time elapsed after the implantation process of the wafer or the amount of radiation in the waiting area.

3. 3. The ion implantation apparatus according to claim 1, wherein the standby unit is the cassette.

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