Semiconductor processing device

Abstract

To achieve accurate specimen transfer by correcting a transfer error attributable to a transfer robot that transfers specimens to be processed by a semiconductor processing device.SOLUTION: Before a transfer mechanism mounts a specimen on a specimen stage, a semiconductor processing device uses an angle or a position of the transfer mechanism measured by a sensor to calculate an amount of positional displacement from an ideal position for the specimen and actuates the specimen stage by the amount of positional displacement.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a sample transport method in a semiconductor processing apparatus. [Background technology]

[0002] In semiconductor processing equipment such as charged particle beam devices, wafer transfer robots are used to transfer samples such as semiconductor wafers into the equipment. For example, a vacuum transfer robot is used to transfer a wafer from a load lock chamber (LC), which connects the equipment to the atmospheric pressure environment outside the equipment, onto a sample stage in a sample chamber (SC), which is in a vacuum environment. In this case, the wafer transfer robot is required to transfer the wafer onto the sample stage with high precision each time it performs a repetitive operation.

[0003] Patent Document 1 discloses a method for transporting wafers with high precision, which achieves high-precision wafer transport by measuring the amount of wafer eccentricity within the LC and correcting the position of the sample stage based on the measured amount of eccentricity. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-114117 Summary of the Invention [Problem to be solved by the invention]

[0005] According to the technology disclosed in Patent Document 1, even if the wafer position in the LC is misaligned, it is possible to achieve highly accurate wafer transport without changing the operation of the transport robot. However, with the technology in this document, if a positioning error occurs in the wafer transport robot that transports the wafer from the preliminary exhaust chamber onto the sample stage, the error cannot be corrected, resulting in a problem of deterioration in the transport accuracy onto the sample stage.

[0006] The present invention has been made in consideration of the above-mentioned problems, and aims to correct transport errors that occur due to a transport robot that transports samples to be processed by a semiconductor processing device, thereby achieving high-precision sample transport. [Means for solving the problem]

[0007] The semiconductor processing apparatus according to the present disclosure calculates the amount of deviation of the sample from its ideal position using the angle or position of the transport mechanism measured by a sensor before the transport mechanism places the sample on the sample stage, and moves the sample stage by the amount of deviation. [Effects of the Invention]

[0008] The semiconductor processing apparatus according to the present disclosure can correct transport errors caused by the transport robot and achieve highly accurate sample transport. Other problems, configurations, effects, and the like of the present disclosure will become clear from the description of the following embodiments. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a configuration diagram of a semiconductor processing apparatus according to a first embodiment. [Figure 2] FIG. 1 is a schematic side view of an in-vacuum wafer transfer robot 11. [Figure 3A] FIG. 1 is a plan view of an in-vacuum wafer transfer robot 11 with its arms extended. [Figure 3B] FIG. 1 is a plan view of the in-vacuum wafer transfer robot 11 with its arms retracted. [Figure 4] The state in which a wafer W is placed in LC2 is shown. [Figure 5] The figure shows the state in which evacuation of the interior of LC2 is completed and the in-vacuum wafer transfer robot 11 extends its arm to pick up the wafer W. [Figure 6] 5, the in-vacuum wafer transfer robot 11 lifts the wafer W and retracts the arm, and then rotates the entire robot so that the in-vacuum wafer transfer robot 11 faces the sample stage 12. [Figure 7] 6. The motor 114 for extending and retracting the arm is rotated to extend the arm from the state shown in FIG. [Figure 8] 10A and 10B are top views illustrating the relationship between a motor positioning error and a wafer deviation amount. [Figure 9] 10 is a flowchart illustrating a method for correcting a wafer misalignment amount when the wafer W is transferred onto the sample stage 12 and a method for transferring the wafer. DETAILED DESCRIPTION OF THE INVENTION

[0010] <First Embodiment> 1 is a configuration diagram of a semiconductor processing apparatus according to a first embodiment of the present disclosure. The semiconductor processing apparatus in FIG. 1 is configured as a charged particle beam apparatus that irradiates a sample (a semiconductor wafer in the following example) with a charged particle beam. The semiconductor processing apparatus includes an SC1, an LC2, a mini-environment (mini-en) 3, and a computer 5.

[0011] The inside of SC1 is in a vacuum state in order to irradiate the charged particle beam, and is equipped with an in-vacuum wafer transport robot 11 (transport mechanism), a sample stage 12, an electron gun 13 that irradiates the wafer with the charged particle beam, and an optical microscope 14 for performing observation and alignment at low magnification.

[0012] LC2 is a preliminary exhaust chamber for connecting SC1, which is a vacuum environment, and mini-environment 3, which is an atmospheric environment. LC2 becomes a vacuum environment when connected to the inside of SC1, and becomes an atmospheric environment when connected to mini-environment 3. LC2 is equipped with a pre-aligner 21 that measures the eccentricity of the wafer W placed in LC2.

[0013] The minienvironment 3 includes a transfer robot 31 for transferring wafers W stored in a front-opening unified pod (FOUP) 4 to the LC 2.

[0014] The computer 5 includes a sample stage control unit 51 that controls the sample stage 12, a transport mechanism control unit 52 that controls the in-vacuum wafer transport robot 11, and a transport error prediction unit 53 that predicts wafer transport errors that may occur due to the in-vacuum wafer transport robot 11.

[0015] 2 is a schematic side view of the in-vacuum wafer transfer robot 11. The in-vacuum wafer transfer robot 11 includes: a hand 111 for placing a wafer W thereon; multiple links 112a and 112b for transmitting motor power; joints 113a and 113b that are constrained to rotate freely between link 112a and link 112b and between link 112b and the hand 111; a motor 114 for extending and retracting the arm; an angle sensor 115 for measuring the output angle of the motor 114 for extending and retracting the arm; a motor 116 for rotating the entire assembly; and an angle sensor 117 for measuring the output angle of the motor 116 for rotating the entire assembly.

[0016] Pulleys and steel belts (not shown) for transmitting motor power are provided inside the links 112a and 112b. When the arm extension / retraction motor 114 is rotated, the power is transmitted by the steel belt, causing the joints 113a and 113b to rotate and the hand 111 to move in the Y direction.

[0017] Fig. 3A is a plan view of the in-vacuum wafer transfer robot 11 with its arm extended. Fig. 3B is a plan view of the in-vacuum wafer transfer robot 11 with its arm retracted. The state of Fig. 3A and the state of Fig. 3B can be switched by rotating the arm extension / retraction motor 114, which makes it possible to transfer the wafer W on the hand 111 in the Y direction. In addition, by rotating the whole rotation motor 116, it is possible to change the direction in which the hand 111 is facing.

[0018] The arm extension / retraction motor 114 and the whole rotation motor 116 may be a stepping motor that allows for easy positioning, or a servo motor such as a direct drive motor that allows for highly accurate positioning.

[0019] It is effective to use, for example, a rotary encoder as the angle sensors 115 and 117. It is necessary to use a rotary encoder with a resolution appropriate to the desired transfer accuracy. When a reducer or belt is used in the arm extension / retraction motor 114 or the whole rotation motor 116, it is effective to install these sensors closer to the wafer than the reducer or belt. By doing so, even if the in-vacuum wafer transfer robot 11 is subjected to external disturbances such as friction during operation, it becomes possible to measure the positioning error caused by the disturbance. The entire intra-vacuum wafer transfer robot 11 can move up and down to lift and place wafers, and is driven by, for example, a ball screw (not shown).

[0020] Next, the operation of transferring the wafer W from the LC2 onto the sample stage 12 by the in-vacuum wafer transfer robot 11 will be described with reference to FIGS.

[0021] 4 shows a state in which a wafer W is placed in LC2. At this time, the inside of LC2 becomes a vacuum environment in order to connect to SC1, and the in-vacuum wafer transfer robot 11 faces the direction of LC2 with its arm retracted and waits.

[0022] FIG. 5 shows the state in which the vacuum evacuation in the LC2 is completed and the in-vacuum wafer transfer robot 11 extends its arm to go and retrieve the wafer W.

[0023] Figure 6 shows the state in which the vacuum wafer transport robot 11 lifts the wafer W from the state shown in Figure 5, retracts its arm, and then rotates the entire robot so that the vacuum wafer transport robot 11 is facing the sample stage 12.

[0024] 7 shows a state in which the arm is extended from the state in FIG. 6 by rotating the arm extension / retraction motor 114, and the wafer W is transferred onto the sample stage 12. By lowering the entire robot from this state, the wafer W is placed on the sample stage 12.

[0025] In the conventional method, when lifting the wafer as shown in Fig. 5, there is a positioning error in the arm extension / retraction motor 114 and the whole rotation motor 116, and this error causes the position where the wafer W is placed on the hand 111 to deviate from the predetermined position. Similarly, when placing the wafer on the sample stage as shown in Fig. 7, there is a positioning error in the arm extension / retraction motor 114 and the whole rotation motor 116, causing the wafer W to deviate from the predetermined position on the sample stage 12, deteriorating the accuracy of wafer transfer onto the sample stage 12.

[0026] Therefore, in this embodiment, the amount of wafer deviation is predicted from these motor positioning errors, and the sample stage 12 is moved by the amount of deviation to correct the error, thereby achieving highly accurate wafer transport.

[0027] Fig. 8 is a top view illustrating the relationship between motor positioning error and wafer misalignment. Fig. 8 is a diagram showing the definitions of the lengths and angles of each part of the in-vacuum wafer transfer robot 11, showing the length 119 (la) of links 112a and 112b, the hand length 120 (lh), the angle 121 (θa) of the arm extension / retraction motor 114, and the angle 122 (θr) of the whole rotation motor. The positions x and y of the center of the wafer (hereinafter referred to as the hand center position) when the wafer is correctly loaded on the hand 111, based on the origin 118 in Fig. 8, can be expressed using these lengths and angles as in Equation 1 and Equation 2, respectively.

[0028]

number

[0029]

number

[0030] Equations 1 and 2 are relational expressions that assume that there is no angular transmission error at the joints 113a and 113b. If angular transmission error occurs at the joints in the in-vacuum wafer transfer robot 11 to which this embodiment is applied, it is preferable to use equations that take this into account. It is also effective to measure this transmission error by providing additional angle sensors at the joints 113a and 113b.

[0031] By using the relational expressions in Equation 1 and Equation 2, the deviations Δx and Δy of the hand center position from the ideal position that occur when the arm is extended as shown in Figure 3A can be expressed as Equation 3 and Equation 4. The superscript cmd represents the command value from computer 5, and the superscript res represents the output value (the actual value detected by the sensor).

[0032]

number

[0033]

number

[0034] If there is no motor positioning error, that is, if the command value and output value are the same, Δx and Δy will be zero. The command value is determined from the desired wafer transport position in the equipment design, and the output value is measured by angle sensors 115 and 117 attached to the in-vacuum wafer transport robot 11.

[0035] Although Equations 3 and 4 express the deviation of the center of the hand 111 focusing only on the motor positioning error, for example, when there is a large temperature change, it is also effective to incorporate into the prediction equation fluctuations in the link length 119 (la) according to the temperature. Also, instead of prediction using mathematical formulas like Equations 3 and 4, it is also possible to model the prediction equation for the hand position from the motor angle by repeatedly performing wafer transport operations using the in-vacuum wafer transport robot 11 during adjustment of the device, for example, and acquiring data on the motor angle and wafer position.

[0036] 9 is a flowchart for explaining a method for correcting the amount of wafer misalignment and a method for transporting the wafer W onto the sample stage 12. This flowchart is executed by the computer 5. The processing flow based on FIG. 9 is as follows.

[0037] Step 200: The transfer robot 31 in the minienvironment 3 transfers the wafer W into the LC2.

[0038] Step 201: While LC2 is being evacuated, the eccentricity (Δxp, Δyp) of the wafer W is measured using the pre-aligner 21. At this time, the in-vacuum wafer transfer robot 11 waits in the state shown in FIG.

[0039] Step 202: As shown in FIG. 5, the arm extension / retraction motor 114 of the in-vacuum wafer transfer robot 11 is driven to extend the arm into the LC2, and the wafer W is lifted up.

[0040] Step 203: When the wafer W is lifted in step 202, the output angle of the arm extension / retraction motor 114 and the output angle of the whole rotation motor 116 are measured by angle sensors 115 and 117, respectively. The transport error prediction unit 53 calculates the deviation (Δxu, Δyu) of the center position of the hand 111 when the wafer is lifted using equations 3 and 4. By combining this with the amount of eccentricity in step 201, it can be calculated that the wafer W lifted in step 202 and placed on the hand 111 is deviated from the center by (Δxp+Δxu, Δyp+Δyu).

[0041] Step 204: The arm extension / retraction motor 114 of the in-vacuum wafer transfer robot 11 is operated to retract the arm.

[0042] Step 205: The whole-unit rotation motor 116 is used to rotate the in-vacuum wafer transfer robot 11 toward the sample stage 12, to bring it into the state shown in FIG.

[0043] Step 206: The arm extension / retraction motor 114 of the in-vacuum wafer transfer robot 11 is operated to extend the arm, and the wafer W is transferred onto the sample stage 12, resulting in the state shown in FIG.

[0044] Step 207: When the arm is extended in step 206, the output angle of the arm extension / retraction motor 114 and the output angle of the whole rotation motor 116 are measured using angle sensors 115 and 117, respectively. The transport error prediction unit 53 calculates the deviation (Δxd, Δyd) of the center position of the hand 111 at this time using equations 3 and 4. By combining this with the amount of wafer position deviation on the hand 111 in step 203, it can be calculated that the wafer W is deviated from the center of the sample stage 12 by (Δxp+Δxu+Δxd, Δyp+Δyu+Δyd).

[0045] Step 208: The transport mechanism control unit 52 provides the wafer deviation amount (Δxp+Δxu+Δxd, Δyp+Δyu+Δyd) calculated in step 207 as a position command in the X and Y directions to the sample stage control unit 51, thereby performing a correction operation for the sample stage 12. This correction operation cancels out the errors calculated up to that point.

[0046] Step 209: After the correction operation in step 208 is completed, the in-vacuum wafer transfer robot 11 is lowered and the wafer W is placed on the sample stage 12. Thereafter, the arm extension / retraction motor 114 is operated to retract the arm, thereby completing a series of wafer transfer operations.

[0047] <First embodiment: Summary> In the semiconductor processing apparatus according to the first embodiment, before the intra-vacuum wafer transfer robot 11 places the wafer W on the sample stage 12, the amount of positional deviation of the wafer W from its ideal position is calculated using the angles measured by the angle sensors 115 and 117 according to Equations 3 and 4. The calculator 5 moves the sample stage 12 by the calculated amount of positional deviation. This makes it possible to reduce positioning errors when the intra-vacuum wafer transfer robot 11 places the wafer W on the sample stage 12.

[0048] The semiconductor processing apparatus according to the first embodiment uses the pre-aligner 21 to measure the eccentricity (Δxp, Δyp) of the wafer W. Furthermore, the pre-aligner 21 calculates the deviation (Δxu, Δyu) of the center position of the hand 111 when lifting the wafer W and the deviation (Δxd, Δyd) of the center position of the hand 111 when placing the wafer W on the sample stage 12. The calculator 5 adds these values ​​together to calculate the amount of deviation of the wafer W from the center of the sample stage 12. This allows the in-vacuum wafer transfer robot 11 to correct the deviation when it receives and delivers the wafer W.

[0049] <Embodiment 2> In a second embodiment of the present disclosure, a description will be given of a configuration example that can be implemented in addition to the configuration described in the first embodiment. Configurations other than those described below are the same as those described in the first embodiment.

[0050] After step 209, an alignment operation is performed to measure the actual position of the wafer W using the optical microscope 14. At this time, if the operation of the intra-vacuum wafer transfer robot 11 while holding the wafer W causes the wafer W to slip on the hand 111, or if a mechanical abnormality such as loosening of the steel belt of the intra-vacuum wafer transfer robot 11 occurs, it is possible that the wafer position will shift despite the correction of the wafer position shift in step 207. In such cases, it is preferable to set a tolerance for the amount of shift in advance, and if the wafer shift exceeds the tolerance, issue an alert to notify the equipment user.

[0051] It is also effective to predict an abnormality occurring in the equipment and change its operation based on the actual wafer misalignment amount measured by the optical microscope 14. For example, if the wafer is significantly misaligned only in the Y direction on the coordinate axes shown in FIG. 1, it is assumed that the wafer has slipped on the hand 111, and by slowing down the arm extension operation in step 206, it is possible to suppress the slippage and continue operating the equipment without stopping. In this case, since the throughput of the equipment decreases, it is necessary to notify the equipment user that the equipment is operating at a slow speed. Furthermore, if there is a large misalignment in both the X and Y directions, it is effective to assume that an abnormality has occurred in the mechanism of the in-vacuum wafer transfer robot 11 and issue an alert to notify the equipment user that maintenance is required.

[0052] After the wafer W is transferred onto the stage in step 206, the motor angle may be measured in real time by the angle sensor 115 of the arm extension / retraction motor. At this time, if the measured angle is oscillatory, for example, the calculation of the wafer deviation amount in step 207 and the wafer placement operation in step 209 are not performed until the vibration has attenuated, thereby ensuring transfer accuracy. In this case, it is effective to wait until the vibration has attenuated to a predetermined amplitude or less. This is because when the base of the arm is vibrating, the vibration is likely to propagate to the tip of the arm, reducing positional accuracy, so it is desirable to wait until the vibration has stopped.

[0053] After the wafer is transferred onto the stage in step 206, it is possible that the angle measured by the angle sensor 115 may gradually deviate even though there is no vibration. In this case, the wafer position may be predicted using equations 3 and 4 according to the amount of drift, and the sample stage 12 may be moved at the same speed based on the predicted wafer position, before steps 207 and onward are carried out. This makes it possible to improve the transfer accuracy while maintaining the transfer speed.

[0054] <Modifications of the present disclosure> The present disclosure is not limited to the above-described embodiments and includes various modifications. For example, the above-described embodiments have been described in detail to clearly explain the present disclosure, and are not necessarily limited to those including all of the described configurations. Furthermore, it is possible to replace part of the configuration of one embodiment with the configuration of another embodiment, or to add the configuration of another embodiment to the configuration of one embodiment. Furthermore, it is possible to add, delete, or replace part of the configuration of each embodiment with other configurations.

[0055] In the above embodiment, an example has been described in which the semiconductor processing apparatus is configured as a charged particle beam apparatus, but it should be noted that the present disclosure is also applicable to other semiconductor processing apparatuses in which a transport mechanism transfers semiconductor samples between the sample stage.

[0056] In the above embodiment, angle sensors 115 and 117 are used to detect the posture (rotation angle of the arm) of intra-vacuum wafer transfer robot 11. However, other sensors may be used as long as they can calculate the position of the sample held by intra-vacuum wafer transfer robot 11. For example, in a configuration example in which the arm of intra-vacuum wafer transfer robot 11 is driven by a linear motor, a sensor may be provided to measure at least either the planar position of the hand or the planar position of the arm, and the position of the sample may be calculated based on the detection results. In this case, the calculation formula, instead of Formulas 3 and 4, will be a formula describing the relationship between the planar position detected by the sensor and the sample position.

[0057] In the above embodiments, each part of the calculator 5 can be configured by hardware such as a circuit device that implements these functions, or by a computing device such as a CPU (Central Processing Unit) executing software that implements these functions.

[0058] The structure of the in-vacuum wafer transfer robot 11 described in the above embodiment is just one example, and it is preferable to use an optimal structure depending on the device to which the present disclosure is applied. For example, instead of transmitting power using a steel belt, a motor may be embedded in the joint portion 113 of the link to drive it. [Explanation of symbols]

[0059] 1. Sample chamber 11 Vacuum wafer transport robot 12 Sample stage 13 Electron gun 14 Optical microscope 2 Load lock chamber 21 Pre-Aligner 3 Minien 31 Transport robot 4 FOUP 5 Calculator 51 Sample stage control unit 52 Transport mechanism control unit 53 Transport error prediction unit W wafer

Claims

1. A semiconductor processing apparatus for processing semiconductor samples, a sample stage on which the sample is placed; a transport mechanism for transferring the sample between the sample stage and the transport mechanism; a sensor for detecting the angle or position of the transport mechanism; a computer that controls the transport mechanism; Equipped with the computer calculates a positional deviation amount of the sample from an ideal position using the angle or the position measured by the sensor before the transport mechanism places the sample on the sample stage; The computer operates the sample stage by the amount of the positional deviation, thereby reducing a positioning error when the transport mechanism places the sample on the sample stage. A semiconductor processing apparatus characterized by:

2. the transport mechanism includes an arm that rotates around a rotation axis; the sensor measures a rotation angle of the arm around the rotation axis as the angle; The computer calculates the amount of positional deviation according to a relational expression between the angle, the length of the arm, and the position of the sample.

2. The semiconductor processing apparatus according to claim 1.

3. the transport mechanism includes an arm that can move within a plane and a hand on which the sample is placed; the sensor measures a planar position of the arm or a planar position of the hand as the position; The computer calculates the amount of positional deviation according to a relational expression between the position and the position of the sample.

2. The semiconductor processing apparatus according to claim 1.

4. the semiconductor processing apparatus includes a pre-aligner that measures an eccentricity of the sample when the sample is stationary before the sample is transported to a sample chamber that accommodates the sample stage; the computer calculates, using the angle or the position, a positional deviation of the sample that occurs when the transport mechanism receives the sample as a receiving deviation; The computer calculates the amount of misalignment by adding the amount of eccentricity measured by the pre-aligner and the misalignment at the time of receiving.

2. The semiconductor processing apparatus according to claim 1.

5. the semiconductor processing apparatus includes a pre-aligner that measures an eccentricity of the sample when the sample is stationary before the sample is transported to a sample chamber that accommodates the sample stage; the computer calculates, using the angle or the position, a positional deviation of the sample that occurs when the transport mechanism places the sample on the sample stage, as a transfer-time deviation; The computer calculates the amount of misalignment by adding the amount of eccentricity measured by the pre-aligner and the misalignment at the time of delivery.

2. The semiconductor processing apparatus according to claim 1.

6. the computer acquires a result of actually measuring a deviation of the sample from the ideal position as an actual measured deviation amount; When the difference between the positional deviation amount calculated using the angle or the position and the actually measured deviation amount is equal to or greater than a threshold value, the computer issues an alert to that effect.

2. The semiconductor processing apparatus according to claim 1.

7. the computer acquires a result of actually measuring a deviation of the sample from the ideal position as an actual measured deviation amount; When the measured deviation amount is equal to or greater than a threshold value, the computer slows down the speed at which the transport mechanism transports the sample compared to when the measured deviation amount is less than the threshold value.

2. The semiconductor processing apparatus according to claim 1.

8. When the angle measured by the sensor before placing the sample on the sample stage is vibrating with an amplitude equal to or greater than a threshold value, the transport mechanism does not perform an operation of placing the sample on the sample stage until the amplitude attenuates to less than the threshold value.

2. The semiconductor processing apparatus according to claim 1.

9. When the angle measured by the sensor before the transport mechanism places the sample on the sample stage gradually deviates at a rate of change equal to or greater than a threshold, the computer moves the sample stage to follow the rate of change.

2. The semiconductor processing apparatus according to claim 1.

10. The semiconductor processing device is configured as a charged particle beam device that irradiates the sample with a charged particle beam.

2. The semiconductor processing apparatus according to claim 1.

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