ion implantation equipment

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 this radiation from leaking outside the equipment.

[0003] Patent Document 1 proposes that neutron scattering members made of materials with a high content of hydrogen or boron, which have a large neutron scattering effect, be placed in areas 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 beam line 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 of the ion beam with 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 beta decay. The generation of gamma rays cannot be avoided depending on the implantation process.

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

[0009] SUMMARY OF THE INVENTION An object of the present invention is to provide an ion implantation apparatus that allows the safe removal of processed wafers. [Means for solving the problem]

[0010] The ion implanter A single-wafer ion implantation apparatus in which a plurality of wafers are taken out one by one from a cassette storing the wafers, the wafers are transported to a processing chamber through a vacuum pre-chamber, and an ion implantation process is performed on the wafers, Between the processing chamber and the cassette, there is a waiting section for storing the wafers that have been subjected to the implantation process.

[0011] a control device that determines whether the wafer can be removed from the waiting section; It is desirable 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 section.

[0012] The standby section is preferably the cassette. [Effects of the Invention]

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

[0014] [Figure 1] FIG. 2 is a schematic plan view showing the configuration of the processing chamber and its surroundings of the ion implantation apparatus. [Figure 2] 10 is a flowchart showing an example of discharging a processed wafer. [Figure 3] 10 is a flowchart illustrating another example of discharging a processed wafer. [Figure 4] FIG. 10 is a schematic plan view showing another configuration around the processing chamber of the ion implantation apparatus. [Figure 5] FIG. 10 is a schematic plan view showing another configuration around the processing chamber of the ion implantation apparatus. DETAILED DESCRIPTION OF THE INVENTION

[0015] 1 shows the configuration of a processing chamber 1 and its surroundings in a single-wafer ion implantation system IM. Cassettes 3a-3d store multiple 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 one of the cassettes 3 a - 3 d is transferred to the aligner 4 , where the orientation of the wafer W in the circumferential direction is aligned, and then transferred to the first vacuum auxiliary chamber 6 .

[0016] When the wafer W is transferred to the first vacuum auxiliary chamber 6, the first vacuum auxiliary chamber 6 is sealed and the chamber is evacuated. When the evacuation of the first vacuum auxiliary 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 upright. 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 for the wafer W is perpendicular to the Y axis.

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

[0018] After the ion implantation process is completed, the vacuum robot 8 transfers the processed wafer W on the platen 2 to the second vacuum auxiliary chamber 7. At this time, the second vacuum auxiliary chamber 7 is in the same vacuum atmosphere as the processing chamber 1. A waiting section T is provided in the second vacuum auxiliary chamber 7. The waiting section T is configured, for example, with a shelf capable of transporting wafers 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 is 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 meets predetermined conditions, 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 in the substrate transport section 5. After the pressure in the second vacuum pre-chamber 7 is changed, the atmospheric robot 9 transfers 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 passed since the implantation process, or whether the amount of radiation emitted from the wafer W in the waiting section T is below a standard value.

[0021] Since the radiation dose emitted by processed wafers decays over time, the time required for the radiation to decay sufficiently is determined in advance through experiments, and this time is set as the predetermined time. Alternatively, the radiation emitted from the wafers W is measured with a dosimeter, and the actual measured value is compared with a standard value that ensures safety. When actually measuring the radiation dose, a dosimeter is installed 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 in 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. In this case, a long waiting time occurs before the next processed wafer W can be transported to the waiting section T, which significantly reduces the productivity of the ion implantation system IM.

[0024] Therefore, shelves capable of storing all of the wafers W (e.g., 25 wafers) in one lot to be subjected to ion implantation processing are 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 apparatus IM can be avoided. Furthermore, if a determination of whether the conditions are met is not made for each wafer W, but is made only for the last 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 the time and dose that serve as the reference for comparison. To give a specific example, when making a determination based on time, the control device C receives, as an input signal Si, information about 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 determines whether or not the wafer W can be removed from the waiting section T. If it determines 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 determination based on 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 the 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 undergoing the implantation process. The output signal So may also be a control signal for controlling each part of the ion implanter IM. However, without being limited thereto, for example, the output signal So may be a signal for notifying the operator of the ion implanter IM of the determination result. In this case, the output signal So may be a signal for notifying the 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 flowcharts assuming that the time required for the ion implantation process on the wafer W is much shorter than 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 required for the ion implantation process is 30 to 40 seconds, and that 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 along 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 step S4, when the time elapsed since the implantation process for the last wafer W is completed reaches or exceeds a reference time, the processed wafers W are sequentially unloaded from the waiting section T (step 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 Figure 3, the processes that use the same reference numerals as in Figure 2 are the same processes as in Figure 2, and therefore the explanation of each process will be omitted. The difference from Figure 2 is that in process S2, ion implantation processing is performed on the last wafer W in a predetermined cassette 3a-3d, and after the last wafer W is transported to the waiting section T, measurement of the dose is performed 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 dose 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 section T is provided in the second vacuum auxiliary chamber 7, but the location of the standby section T is not limited to this. For example, as shown in FIG. 4, the standby section T may be provided in the processing chamber 1, and the processed wafer W may be transported thereto and kept waiting until predetermined conditions are met.

[0035] As shown in Figure 4, a waiting section T may be provided within the processing chamber 1, but when performing measurements using a dosimeter, there is a concern that radiation emitted from the wafer W during processing may cause erroneous measurements. For this reason, it is desirable to provide a partition to shield against radiation generated within the processing chamber and to spatially separate the waiting section T. Alternatively, 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 pre-chamber 7, and the standby section T may be provided in that room.

[0036] Furthermore, as shown in Fig. 5, the standby 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 shelves for storing wafers W, which is advantageous in that a special shelf for storing processed wafers W on standby is not required in the waiting section T.

[0037] If the standby section T is provided 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 long time to switch the vacuum atmosphere in the standby chamber and that a large amount of purge gas will be required. However, if cassettes 3a-3d are used as the standby section T, the volume of the standby chamber can be small, so these concerns do not arise.

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

[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. In this regard, the cassettes 3a-3d are covered with a shield made of, for example, acrylic resin or iron to prevent radiation leakage. In addition, because the cassettes 3a-3d are placed in a sealed container when transported between devices due to particle contamination, the shield may also serve as the housing of the wafer transport container.

[0040] 1, the standby section T is provided in the second vacuum auxiliary chamber 7, but the standby section T may be provided in the first vacuum auxiliary chamber 6. Furthermore, the ion implantation apparatus IM may be configured to include only one of the two vacuum auxiliary 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 along the transport path of the wafers W from the implantation process to storage in the cassettes 3a-3d, that is, between the processing chamber 1 and the cassettes 3a-3d, depending on the configuration of the ion implantation system IM.

[0042] It is not necessary that all of the cassettes 3a to 3d store unprocessed wafers W. For example, one of the four cassettes 3a to 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, the ion species, and the wafer material during the ion implantation process, it may not be necessary to perform the discrimination process in the above embodiment depending on the implantation process content. The discrimination process described in the above embodiment is performed on the assumption that radioactive decay occurs. If the process for determining whether 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 depending on the contents of the injection process before the discrimination process described in the above embodiment. Specifically, in the flowcharts of Figures 2 and 3, this determination is made before process S1.

[0044] For this determination, 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 determination process described in the above embodiment is performed. This determination may be performed by the control device C, or the operator of the ion implantation device IM may make the determination after 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 measured value may be used as a reference value to be compared with the measured 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 chamber 3a-3d cassette 6. First vacuum chamber 7 Second Vacuum Prep Chamber IM Ion Implantation Equipment W wafer T Standby section C Control device

Claims

1. A single-wafer ion implantation apparatus in which a plurality of wafers are taken out one by one from a cassette storing the wafers, the wafers are transported to a processing chamber through a vacuum pre-chamber, and an ion implantation process is performed on the wafers, a waiting section for storing the wafers that have been subjected to implantation processing between the vacuum preparatory chamber and the cassette; a control device that determines whether the wafer can be removed from the waiting section; 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 section.

2. An ion implantation apparatus as described in claim 1, wherein the control device compares the radiation dose in the waiting section with a reference value to determine whether or not the wafer can be removed.

3. An ion implantation device as described in claim 2, wherein the reference value is the radiation dose in the external environment of the ion implantation device.

Images