Prober and probe inspection method

Abstract

A prober 100 for executing an electric test on a wafer includes: a wafer chuck 20 having a holding surface for holding a wafer W; a probe card 25 having a plurality of probes 26 on a surface facing the holding surface; an alignment device for positioning the wafer chuck with respect to the probe card; and a control device. The control device includes a memory, a processor, and a program stored in the memory and configured to be executable by the processor. The program includes a command for switching position control for the alignment device from full-closed control to semi-closed control at a first timing related to the start of the electric test. This prober makes it possible to perform alignment with high accuracy even when performing high-voltage measurement.

Description

Prober and probe inspection method

[0001] The present disclosure relates to a prober for performing electrical tests on wafers and a probe inspection method.

[0002] A prober is known as a device used to check the operation of semiconductor chips formed on a wafer. This check is an electrical test called wafer-level inspection. Specifically, the electrode pads of the semiconductor chip are connected to a test head via probes, and the test head supplies power and test signals, and the test head measures the signals output by the semiconductor chip.

[0003] Wafer-level inspection requires highly accurate contact of multiple probes with the electrode pads of a semiconductor chip, i.e., highly accurate alignment (positioning) between the probes (probe card) and the electrode pads of the semiconductor chip.

[0004] As such a technique, Patent Document 1 discloses a prober and a probe alignment method that are capable of performing alignment with high accuracy.

[0005] Japanese Patent Application Laid-Open No. 2022-175805

[0006] In recent years, the applications of power semiconductors have expanded. Power semiconductors are used in power converters such as inverters and converters, and can be used at higher voltages, larger currents, and higher frequencies. Demand for power semiconductors is particularly expanding with the spread of electric vehicles such as EVs (electric vehicles) and PHEVs (plug-in hybrid vehicles). To conduct electrical tests on these semiconductor chips, there is a growing demand for probers that can perform stable tests at higher voltages.

[0007] The inventors have found that when a prober measures high voltage, sparks occur inside the device, particularly inside the wafer, and this affects the operation of the wafer alignment device. Specifically, they have found that the sparks appear as noise (contaminate) in the output signal of the position detection means (e.g., a linear scale) of the alignment device. This noise can sometimes exceed the alarm threshold of the position detection means. Noise that exceeds the alarm threshold often stops the operation of the alignment device and the prober itself.

[0008] FIG. 7 is a diagram showing an example of an output signal of a linear scale (position detection means) in a conventional prober. The horizontal axis 50 represents time, and the vertical axis 51 represents the magnitude of the output signal. FIG. 7 shows the effect of a spark on an output signal 52 of the linear scale. That is, when a spark occurs inside the device, a large amplitude noise 53 is generated in the output signal 52. When this exceeds an upper limit 54 and / or a lower limit 55 alarm threshold (represented by reference numeral 56), the operation of the prober is generally stopped. If the operation of the prober is stopped, the inspection efficiency of the wafer W will be significantly reduced.

[0009] The present disclosure aims to solve at least some of the problems associated with the prior art, such as those described above. Specifically, one of the objectives of the present disclosure is to provide a prober and a probe inspection method that are capable of performing high-precision alignment even when performing high-voltage measurements.

[0010] One embodiment of the prober of the present disclosure is a prober that performs electrical testing on a wafer, and includes a wafer chuck having a holding surface that holds the wafer, a probe card having a plurality of probes on a surface opposite the holding surface, an alignment device that positions the wafer chuck relative to the probe card, and a control device, wherein the control device includes a memory, a processor, and a program stored in the memory and configured to be executable by the processor, the program including an instruction to switch the position control of the alignment device from full-closed control to semi-closed control at a first timing related to the start of the electrical test.

[0011] One embodiment of the probe inspection method of the present disclosure is a probe inspection method including: using an alignment device to position a wafer chuck, with a wafer held on its holding surface, relative to a probe card having a plurality of probes on a surface opposite the holding surface; performing an electrical test on the wafer using the probes that have been brought into contact with the wafer; and switching the position control of the alignment device from full-closed control to semi-closed control at a first timing related to the start of the electrical test.

[0012] According to the present disclosure, at least one of the problems of the conventional techniques can be solved. One of the specific effects is that a prober and a probe inspection method that can perform alignment with high accuracy even when performing high-voltage measurement can be provided.

[0013] 1 is a block diagram showing a system configuration of a prober according to an embodiment; FIG. 2 is an explanatory diagram of the function of a control switching unit during full-closed control; FIG. 3 is an explanatory diagram of the function of a control switching unit during semi-closed control; FIG. 4 is a flow chart showing the procedure of an electrical test (wafer-level inspection) using a prober; FIG. 5 is a flow chart of another example of the procedure of an electrical test (wafer-level inspection) using a prober; FIG. 6 is a flow chart of another example of the procedure of an electrical test (wafer-level inspection) using a prober; and FIG. 7 is a diagram showing an example of an output signal of a linear scale (position detection means) in a conventional prober.

[0014] A first embodiment of the prober of the present disclosure is a prober that performs electrical testing on a wafer, and includes a wafer chuck having a holding surface that holds the wafer, a probe card having a plurality of probes on a surface opposite the holding surface, an alignment device that positions the wafer chuck relative to the probe card, and a control device, wherein the control device includes a memory, a processor, and a program stored in the memory and configured to be executable by the processor, and the program includes an instruction to switch the position control of the alignment device from full-closed control to semi-closed control at a first timing related to the start of the electrical test.

[0015] According to the above-described prober, the alignment device is switched from full-closed control to semi-closed control at a first timing related to the start of an electrical test. When a wafer-level inspection (electrical test) is performed, the alignment device is controlled by semi-closed control, which does not use the output signal of the position detection means. Therefore, even in a test that applies a high voltage, the alignment device and the prober are prevented from stopping due to noise mixed in the output signal of the position detection means. Furthermore, because the control is switched from full-closed control at the first timing related to the start of an electrical test, in other words, positioning is performed using full-closed control until the first timing, positioning accuracy is also improved.

[0016] Generally, semi-closed loop control is said to have lower positioning accuracy than full-closed loop control. However, the above-mentioned prober switches to semi-closed loop control only at the first timing, and therefore maintains high positioning accuracy up to that point. Furthermore, wafer-level inspection (electrical testing) is generally performed with the electrode pads of the semiconductor chip on the wafer in contact with the probes of the probe card. That is, once the electrical testing begins, the alignment device is primarily required to stop the wafer at a predetermined position. Therefore, the positioning accuracy required during the electrical testing is not as high as that required for positioning before the electrical testing begins. In other words, although the above-mentioned prober may partially employ semi-closed loop control, when viewed from the perspective of the entire wafer-level inspection process, it can perform electrical testing requiring the application of high voltages more stably than conventional techniques. Furthermore, the positioning accuracy is also higher.

[0017] A second embodiment of the prober of the present disclosure is a prober in which, in the first embodiment, the alignment device is equipped with a position detection means for detecting the position of the wafer chuck, a driving means for driving the wafer chuck, and a feedback sensor provided on the driving means.

[0018] The alignment device includes a position detection means and a feedback sensor. Therefore, around the first timing, the position control of the wafer chuck is switched from full-closed control based on the output signal of the position detection means to semi-closed control based on the output signal of the feedback sensor. The output signal of the feedback sensor is less likely to generate large noise even when a high voltage is applied, resulting in more stable operation of the prober.

[0019] A third embodiment of the prober of the present disclosure is the prober of the first or second embodiment, wherein the first timing is before application of a measurement voltage for the electrical test.

[0020] Setting the first timing to be before (specifically, immediately before) the application of the measurement voltage for the electrical test means that positioning is performed under full-closed control until the application of the measurement voltage. With the above prober, the positioning accuracy is further improved and the operation of the prober is more stable.

[0021] A fourth embodiment of the prober of the present disclosure is a prober in which, in the first or second embodiment, a test head is provided that supplies test signals to the wafer via the plurality of probes, and the first timing is immediately after the control device receives a signal to start measurement by the test head.

[0022] Setting the first timing to immediately after receiving the measurement start signal means that positioning is performed under full-closed control until immediately before the application of a high voltage that would cause noise in the output signal of the position detection device. With this prober, the positioning accuracy is further improved and the operation of the prober is more stable.

[0023] A fifth embodiment of the prober of the present disclosure is the prober of the first or second embodiment, wherein the first timing is after the wafer chuck is positioned at a predetermined position for starting the electrical test.

[0024] By setting the first timing to be after positioning (typically immediately after), the timing to switch to semi-closed loop control can be determined using only the control sequence of the alignment device, without waiting for a signal related to the start of an electrical test. This makes it easier to control the prober. Of course, switching to semi-closed loop control may also be performed based on a test start signal provided by the test head.

[0025] A sixth embodiment of the prober of the present disclosure is a prober in which, in the first or second embodiment, the alignment device is configured to be able to move the wafer chuck in the Z-axis direction facing the probe card and in the XY-axis directions approximately parallel to the probe card, and the first timing is before the wafer chuck is moved upward in the Z-axis direction toward the probe card.

[0026] A wafer held on a wafer chuck has multiple semiconductor chips formed on it. Electrical testing is performed by contacting probes with the electrode pads of each of the semiconductor chips. For this purpose, multiple probes are arranged on a probe card. Therefore, precise positioning of the wafer and probes is essential for accurate wafer-level testing. In particular, high positioning accuracy is required in the X and Y axes to align the positions of the multiple probes and electrode pads.

[0027] On the other hand, position control in the Z-axis direction is typically performed to bring the probe, which is an elastic body, into contact with the electrode pad. This requires a slightly lower level of accuracy than control in the X- and Y-axes. Therefore, even if the control is switched to semi-closed loop control before (typically immediately before) the Z-axis position control, the effect on measurement accuracy of the prober as a whole is kept to a minimum.

[0028] A seventh embodiment of the prober of the present disclosure is a prober in the sixth embodiment, wherein the program further includes an instruction to position the alignment device in the XY axis direction before starting the electrical test and before switching to the semi-closed control.

[0029] In the above prober, positioning in the X and Y axes directions is performed under full-closed control, thereby achieving even greater positioning accuracy.

[0030] An eighth embodiment of the prober of the present disclosure is a prober in which, in the first or second embodiment, the program includes an instruction to switch the position control of the alignment device from semi-closed control to fully closed control at a second timing related to the end of the electrical test.

[0031] During the electrical test, there is a risk of noise being generated in the position detection means due to the application of high voltage. However, after the electrical test is completed, there is almost no risk of this happening, so by switching to full-closed control at the second timing, the positioning accuracy is further improved.

[0032] A ninth embodiment of the prober of the present disclosure is the prober of the eighth embodiment, wherein the second timing is after the electrical test is completed and before the movement of the wafer chuck starts.

[0033] As described above, the positioning of the alignment device relative to the wafer chuck during electrical testing is stopped in place (at a predetermined position). Therefore, the influence of semi-closed control on the positioning accuracy is minimized. In the above prober, before (typically immediately before) the wafer chuck starts moving (from a stopped state), the control is switched to full-closed control, which has higher positioning accuracy. Therefore, the positioning accuracy and stability of the prober as a whole are improved.

[0034] A first embodiment of the probe inspection method of the present disclosure is a probe inspection method that includes using an alignment device to position a wafer chuck, with a wafer held on its holding surface, relative to a probe card having a plurality of probes on a surface opposite the holding surface; performing an electrical test on the wafer using the probes that have been brought into contact with the wafer; and switching the position control of the alignment device from full-closed control to semi-closed control at a first timing related to the start of the electrical test.

[0035] According to the above probe inspection method, the position control of the alignment device is switched from full-closed control to semi-closed control at a first timing related to the start of an electrical test. When a wafer-level inspection (electrical test) is performed, the alignment device is controlled by semi-closed control, which does not use an output signal from a position detection means. Therefore, even in tests that apply high voltages, the alignment device and prober are prevented from stopping due to noise generated by the position detection means. Furthermore, because the control is switched from full-closed control at the first timing related to the start of an electrical test, in other words, positioning is performed using full-closed control until the first timing, positioning accuracy is also improved.

[0036] 1 is a block diagram showing the system configuration of a prober 100 according to an embodiment of the present invention. The prober 100 includes a prober control unit 10, an XY stage 22, a Zθ stage 21, a wafer chuck 20, probes 26, a probe card 25, a servo amplifier 30, and the like.

[0037] The prober control unit 10 includes a memory and a processor. The prober control unit 10 is typically a computer and is a control device for the prober 10. The prober control unit 10 executes a program stored in the memory using the processor, issues commands to the servo amplifier 30, etc., and controls the operation (operation sequence) of the prober 10. The prober control unit 10 includes a communication unit 10-1 and a drive control unit 10-2. These are functions realized by instructions included in a program stored in the memory provided in the prober control unit 10, related hardware, and related software.

[0038] The communication unit 10-1 is a function realized by hardware such as a communication interface and software such as related drivers. The communication unit 10-1 establishes a connection between the prober control unit 10 and the test head 29, and performs signal transmission and reception, data conversion, etc., based on instructions contained in the program of the prober control unit 10. The drive control unit 10-2 controls the alignment device (XY stage 22 and Zθ stage 21) based on instructions contained in the program of the prober control unit 10, and adjusts the position of the wafer W. The alignment device is directly controlled by a servo amplifier 30. The servo amplifier 30 operates based on commands from the drive control unit 10-2. In other words, the servo amplifier 30 constitutes part of the control device.

[0039] The servo amplifier 30 includes a position information acquisition unit 30-1, a control switching unit 30-2, and a motor control unit 30-3. These are all functions of the servo amplifier 30, and will be described in detail later.

[0040] The wafer chuck 20 has a holding surface for holding the wafer W. The relative position of the wafer W held on the holding surface and the probe card 25 is adjusted by the XY stage 22 and the Zθ stage 21. In other words, the XY stage 22 and the Zθ stage 21 constitute an alignment device that positions the wafer chuck 20 relative to the probe card 25. The XY stage 22 is responsible for adjusting the position in directions along the surface of the wafer W (XY axis directions). The XY axis directions are also directions approximately parallel to the probe card 25. The Zθ stage 21 is responsible for adjusting the position in the direction in which the surface of the wafer W faces (Z axis direction) and in the θ axis direction. The θ axis is a rotation axis centered on the Z axis.

[0041] The XY stage 22 includes a servo motor 27 as a driving means, a linear scale 24 as a position detection means, and a rotary encoder 28 as a feedback sensor. However, the driving means, position detection means, and feedback sensor of the alignment apparatus are not limited to those described above. For example, the driving means is not particularly limited as long as it can drive the XY stage 22. For example, it may be a stepping motor, a brushless motor, or a vector-controlled inverter motor with a sensor. Furthermore, the position detection means is not particularly limited as long as it detects the position of the wafer chuck 20 (or the position of the XY stage 22) and the output signal can be used for feedback control of the driving means. For example, the linear scale may be optical, magnetic, capacitive, or a combination of these. Other position detection means include a laser interferometer. Furthermore, the feedback sensor is not particularly limited as long as it can measure the rotation angle of the motor, which is the driving means. A magnetostrictive displacement sensor or the like may be used instead of a rotary encoder.

[0042] If the driving means is a pulse motor, the feedback sensor can be omitted. In this case, semi-closed control can be replaced by position control using only pulse commands from the servo amplifier 30. Furthermore, full-closed control can be position control that uses linear scale information from the linear scale 24 and feeds it back to the servo amplifier 30. Furthermore, although not shown in the figure, it is preferable that the Zθ stage 21 also be equipped with a driving means, a position detection device, and a feedback sensor, similar to the XY stage 22. The above-mentioned hardware included in the Zθ stage 21 may be the same as the hardware included in the XY stage 22.

[0043] The probe card 25 has a plurality of probes 26. These probes 26 are each connected to a terminal of a test head 29. During wafer-level inspection, the probes 26 come into contact with electrode pads of semiconductor chips formed on the wafer W. The contact positions are adjusted by an alignment device. As a result, the terminals of the test head 29 are electrically connected to the electrode pads via the probes 26. The test head 29 supplies power and test signals to the electrode pads. The test head 29 also detects outputs from the electrode pads. As a result of the above, wafer-level inspection (electrical testing) is performed.

[0044] Next, one embodiment of the procedure for performing an electrical test will be described. Figure 4 is a flow diagram showing the procedure for an electrical test (wafer-level inspection) using the prober 100. First, in step S1, the servo amplifier 30 controls the servo motor 27 to position the XY stage 22. The servo amplifier 30 performs this positioning in response to a command from the drive control unit 10-2. The drive control unit 10-2 transmits the command when the communication unit 10-1 of the prober control unit 10 receives a signal from the test head 29 to start the electrical test. Specifically, the XY stage 22, which holds the wafer W on the wafer chuck 20, is positioned by driving the ball screw 23 with the servo motor 27.

[0045] When the ball screw 23 is rotated by the servo motor 27, the XY stage 22 is moved to a predetermined position. Whether the amount of movement is as instructed, that is, the position of the XY stage 22 (that is, the position of the wafer chuck 20) ​​is detected by the linear scale 24. Also, whether the amount of rotation of the servo motor 27 is as instructed is detected by the rotary encoder 28 of the servo motor 27. The detected linear scale information 62 and encoder information 61 are input to the position information acquisition unit 30-1 of the servo amplifier 30.

[0046] The position information acquisition unit 30-1 transmits the acquired position information to the motor control unit 30-3 via the control switching unit 30-2. The motor control unit 30-3 transmits motor command information 64 to the servo motor 27 based on the position information, and drives the XY stage 22 to a predetermined position corresponding to the probe card 25. At this time, the position control of the XY stage 22 is performed by full-closed control using linear scale information 62 detected by the linear scale 24. In other words, the positioning of the alignment device in the X and Y axes is performed by full-closed control. As will be described in detail later, the position information acquisition unit 30-1 transmits linear scale information 62 and encoder information 61 as position information to the control switching unit 30-2. The control switching unit 30-2 transmits only the linear scale information 62 to the motor control unit 30-3 as the selected position information 63.

[0047] Next, in step S2, the control switching unit 30-2 of the servo amplifier 30 switches the positioning of the alignment device to semi-closed control based on the control switching command 60 from the drive control unit 10-2. In other words, the drive control unit 10-2 transmits the control switching command 60 to the control switching unit 30-2 at the timing (an example of the first timing) when the positioning of the alignment device in the X and Y axes directions associated with the start of the electrical test is completed. The timing when the positioning in the X and Y axes directions is completed may be immediately before the wafer chuck 20 is moved upward in the Z axis direction or immediately after the servo amplifier 30 receives a command to lift the Zθ stage 21. The command to lift the Zθ stage 21 may be received from the drive control unit 10-2 based on the driving status of the alignment device, or may be received from the drive control unit 10-2 based on a higher-level command received from the test head 29. When the control is switched to semi-closed control, the control switching unit 30-2 transmits only the encoder information 61 to the motor control unit 30-3 as the selected position information 63.

[0048] An example of a method for switching between full-closed control and semi-closed control will be described in detail. FIG. 2 is an explanatory diagram of the function of the control switching unit 30-2 during full-closed control. The control switching unit 30-2 passes one of the position information acquired by the position information acquisition unit 30-1 to the motor control unit 30-3 as selected position information 63 for feedback control. The position information acquisition unit 30-1 acquires encoder information 61 from the rotary encoder 28 and linear scale information 62 from the linear scale 24. The full-closed control state is achieved when the control switching unit 30-2 transmits the linear scale information 62 to the motor control unit 30-3 as the selected position information 63. On the other hand, FIG. 3 is an explanatory diagram of the function of the control switching unit 30-2 during semi-closed control. In this case, the control switching unit 30-2 transmits the encoder information 61 to the motor control unit 30-3 as the selected position information 63. In this manner, switching between semi-closed control and full-closed control is easy.

[0049] Next, in step S3, the servo amplifier 30, upon receiving a command from the drive control unit 10-2, controls the servo motor 27 to raise and position the Zθ stage 21. Specifically, the wafer W held by the wafer chuck 20 is raised in the Z-axis direction by the Zθ stage 21, and the probes 26 are brought into contact with the wafer W (electrode pads). At this time, the Zθ stage 21 is rotated as necessary to position the electrode pads and the probes. In this state, the electrode pads of the wafer W are electrically connected to the terminals of the test head 29 via the probes 26, completing preparations for the electrical test.

[0050] Next, in step S4, the communication unit 10-1 transmits to the test head 29 that preparations for the electrical test (wafer-level inspection) are complete (contact state has been reached). The test head 29, having confirmed the contact state based on the contact completion signal from the prober control unit 10, starts the electrical test. Specifically, a voltage is applied to the electrode pads formed on the wafer W. In the contact state, the electrode pads and the terminals of the test head 29 are connected via the probes 26. In semiconductors for power devices, the applied voltage is likely to be higher. The test head 29 receives and analyzes signals output from the semiconductor chips to test whether the semiconductor chips operate normally.

[0051] Note that even during testing, the position control of the alignment device continues under semi-closed control. Position control of the alignment device is required not only to move the wafer chuck 20 to a predetermined position, but also to prevent positional deviation of the Zθ stage 21 and the XY stage 22 due to vibration caused by the upward movement of the Zθ stage 21, impact at the time of contact, disturbance during contact (high voltage measurement), and the like. In other words, position control is performed even when a (high) voltage for measurement is applied. In the prober of this embodiment, semi-closed control is used at this time, which ensures resistance to noise and higher stability.

[0052] Next, in step S5, the electrical test is completed. The application of voltage from the test head 29 to the electrode pads is completed. Wafer-level inspection is typically performed on each wafer W. When inspection of one wafer W is completed, the alignment device returns the inspected wafer W to a transport unit (not shown) and receives a new wafer W from the transport unit. Therefore, when inspection of one wafer W is completed, the alignment device is controlled to move the wafer W away from the probe card 25. Therefore, the following steps are for removing and replacing the wafer W.

[0053] Next, in step S6, the control switching unit 30-2 of the servo amplifier 30 switches the positioning of the alignment device to fully closed control. This switching is performed based on a control switching command 60 from the drive control unit 10-2. This control switching command 60 is typically generated when the communication unit 10-1 of the prober control unit 10 receives a signal indicating the end of the electrical test from the test head 29. In other words, the drive control unit 10-2 sends a command to the control switching unit 30-2 at the timing when the prober control unit 10 receives a signal indicating the end of the electrical test from the test head 29 (which is an example of the second timing). Note that the method of switching from semi-closed control to fully closed control is the reverse of the above.

[0054] In addition to the above, the second timing in this example can be defined as follows: Immediately before the Zθ stage 21 descends after the electrical test is completed Immediately after the servo amplifier 30 receives a command to descend the Zθ stage 21

[0055] The command to lower the Zθ stage 21 can typically be received from the drive control unit 10 - 2 based on a higher-level command received from the test head 29 .

[0056] Next, in step S7, the servo amplifier 30 controls the servo motor 27 to lower the Zθ stage 21. This is performed based on a command from the drive control unit 10-2. The drive control unit 10-2 transmits the command when the communication unit 10-1 receives a signal from the test head 29 to start the electrical test. Then, the XY stage 22 is controlled (step S8). The wafer chuck 20 is moved to a position where the wafer W is transferred to and from the transport unit.

[0057] According to the above-described prober, the position control of the alignment device is switched from full-closed control to semi-closed control at a first timing related to the start of an electrical test. When a wafer-level inspection (electrical test) is performed, the alignment device is controlled by semi-closed control, which does not use an output signal from the position detection means. Therefore, even when an inspection is performed in which a high voltage is applied, the alignment device and the prober are prevented from stopping due to noise generated by the position detection means. Furthermore, because the control is switched from full-closed control at the first timing related to the start of an electrical test (in other words, because positioning is performed using full-closed control until the first timing), positioning accuracy is also improved.

[0058] Furthermore, during the electrical test, the application of high voltage may cause noise to be mixed into the output signal of the position detection means. However, after the electrical test is completed, this risk is almost eliminated. Therefore, by switching to full-closed control at the second timing, positioning accuracy is further improved.

[0059] In the above example, the first timing is the timing when positioning of the alignment device in the X and Y axes is completed in response to the start of an electrical test, and the second timing is the timing when the prober control unit 10 receives a signal indicating the end of the electrical test from the test head 29. However, the first timing, i.e., the timing when the positioning of the wafer chuck 20 is switched from full-closed control to semi-closed control, is not limited to the above. Furthermore, the second timing, i.e., the timing when the positioning of the wafer chuck 20 is switched from semi-closed control to full-closed control, is not limited to the above. Below, other examples of the first timing and the second timing will be described.

[0060] 5 and 6 are flow diagrams of another example of the procedure for electrical testing (wafer-level inspection) using a prober. The flow in FIG. 5 shows the procedure up to the start of electrical testing. In the flow in FIG. 5, after positioning the XY stage 22 in step S1, the Zθ stage 21 is raised and positioned in step S3. Step S1 is the same as the corresponding step in the flow in FIG. 4. Step S3 is also the same as the corresponding step in the flow in FIG. 4, except that it is performed under fully closed loop control.

[0061] After the Zθ stage 21 is raised and positioned, the control is switched to semi-closed loop control in step S2. Then, in step S4, an electrical test is started. That is, the first timing in this example is immediately before the electrical test. Note that "immediately before the electrical test" can be defined as follows, for example: Immediately after the communication unit 10-1 receives a measurement start signal from the test head 29. Immediately after the contact completion signal is sent from the prober control unit 10 to the test head 29. Immediately after the wafer chuck 20 is aligned to a predetermined position for starting the electrical test.

[0062] In the above example, the terms "immediately before" and "immediately after" are used, but this does not imply a time limitation. For example, an operation sequence in which A, B, and C are processed in this order will be described. When we say "D is performed immediately after A," it means that the operations are performed in the order A, D, B, and C. In other words, when we say "immediately after A," it means that D is inserted between A and B, which was processed immediately after A. The same applies to "D is performed immediately before B." The above interpretation applies to other parts of this specification as well.

[0063] 6 is a flow diagram of another example of the procedure for electrical testing (wafer-level inspection) using a prober, showing the procedure from the end of the electrical test. In the flow of FIG. 6, after the electrical test is completed in step S5, the Zθ stage 21 is lowered in step S7. This flow differs from the flow of FIG. 4 in that the lowering of the Zθ stage 21 in step S7 is performed under semi-closed loop control.

[0064] Next, the control is switched to the fully closed control in step S6, and then the XY stage 22 is moved in step S8.

[0065] In this example, the timing (second timing) of switching from semi-closed control to fully closed control is after the Zθ stage 21 has descended. "After the Zθ stage 21 has descended" can be defined as follows, for example: Immediately before the XY stage 22 starts operating Immediately after the wafer chuck 20 has completed descending

[0066] As described above, according to this embodiment, even in a prober that performs high-voltage measurements, there is no need to use an expensive, highly noise-resistant linear scale 24, and positional deviation of the XY stage 22, etc., due to impacts at the time of contact or disturbances during contact (high-voltage measurement) can be prevented. Furthermore, the prober of this embodiment performs semi-closed loop control at a timing when noise is likely to be mixed into the output signal of the linear scale 24, thereby suppressing operation stoppages due to errors. This improves wafer W testing efficiency, achieves high throughput, and improves positioning accuracy. Furthermore, switching between full-closed loop control and semi-closed loop control can be achieved by updating the program in the control device. In other words, even a prober already installed in a factory, etc., can be used as a prober of the present disclosure by updating the program.

[0067] It should be noted that the first timing and the second timing described in the flow of Fig. 4 and the flows of Fig. 5 and 6 can be combined. That is, the flow of Fig. 4 up to the start of the electrical test may be replaced with the flow of Fig. 5. Also, the flow of Fig. 4 after the end of the electrical test may be replaced with the flow of Fig. 6.

[0068] REFERENCE SIGNS LIST 10... Prober control unit 10-1... Communication unit 10-2... Drive control unit 20... Wafer chuck 21... Zθ stage 22... XY stage 23... Ball screw 24... Linear scale 25... Probe card 26... Probe 27... Servo motor 28... Rotary encoder 29... Test head 30... Servo amplifier 30-1... Position information acquisition unit 30-2... Control switching unit 30-3... Motor control unit W... Wafer

Claims

1. A prober for performing electrical testing on a wafer, comprising: a wafer chuck having a holding surface for holding the wafer; a probe card having a plurality of probes on a surface opposite to the holding surface; an alignment device for positioning the wafer chuck relative to the probe card; and a control device, wherein the control device includes a memory, a processor, and a program stored in the memory and configured to be executable by the processor, the program including an instruction to switch the position control of the alignment device from full-closed control to semi-closed control at a first timing related to the start of the electrical test.

2. The prober according to claim 1, wherein said alignment device comprises a position detection means for detecting the position of said wafer chuck, a driving means for driving said wafer chuck, and a feedback sensor provided in said driving means.

3. The prober according to claim 1 or 2, wherein the first timing is before application of a measurement voltage for the electrical test.

4. The prober according to claim 1 or 2, further comprising a test head that supplies test signals to the wafer via the plurality of probes, and wherein the first timing is immediately after the control device receives a signal to start measurement by the test head.

5. The prober according to claim 1 or 2, wherein the first timing is after the wafer chuck is positioned at a predetermined position for the start of the electrical test.

6. A prober according to claim 1 or 2, wherein the alignment device is configured to be able to move the wafer chuck in a Z-axis direction facing the probe card and in X- and Y-axis directions substantially parallel to the probe card, and the first timing is before the wafer chuck is moved upward in the Z-axis direction toward the probe card.

7. The prober according to claim 6, wherein the program further includes an instruction to position the alignment device in the X and Y axes before starting the electrical test and before switching to semi-closed loop control.

8. A prober according to claim 1 or 2, wherein the program includes a command to switch the position control of the alignment device from semi-closed control to fully closed control at a second timing related to the end of the electrical test.

9. The prober according to claim 8, wherein the second timing is after the electrical test is completed and before the wafer chuck starts moving.

10. A probe inspection method comprising: using an alignment device to position a wafer chuck, with a wafer held on its holding surface, relative to a probe card having a plurality of probes on a surface opposite the holding surface; performing an electrical test on the wafer using the probes that have been brought into contact with the wafer; and switching the position control of the alignment device from full-closed control to semi-closed control at a first timing related to the start of the electrical test.

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