prober

Abstract

A prober according to the present invention is characterized by comprising an XY stage 22 on which is provided a Zθ stage 21 on which is provided a wafer chuck 20, guides 41 that guide drive shafts for the X-axis, Y-axis, Z-axis, and θ-axis directions of the wafer chuck, a prober control unit 10 that drives motors, drives the XY stage in the XY-axis directions to a prescribed position that corresponds to a device measurement instrument 29, and raises the Zθ stage in the Z-axis direction to bring an electrode pad into electrical contact with a probe needle 26, and a brake that is affixed to at least one of the guides and holds the drive shaft at which the brake is affixed to fix the drive shaft to the guide. The prober is also characterized in that the motors have a motor excitation brake function, and after the electrode pad has been brought into contact with the probe needle, the prober control unit turns on the brake and turns off the motor excitation brake of the motor that corresponds to the drive shaft at which the brake is affixed. The prober thereby makes it possible to greatly reduce power consumption, improve positioning precision, and achieve high-precision contact, high-speed needle track inspection function, and high speed / low vibration.

Description

prober

[0001] The present invention relates to a prober for testing the electrical characteristics of semiconductor chips formed on a semiconductor wafer.

[0002] In recent years, for example, in memory wafer testing, the number of probes on a probe card has increased, increasing the load on the prober drive shaft during wafer contact. Furthermore, parametric wafer testing, which assumes a specific distribution, requires an environment that minimizes noise around the wafer, while wafer testing using an optical system requires an environment that minimizes prober stage vibration during wafer testing.

[0003] In particular, power semiconductor technology requires parametric testing to maximize measurement performance, accommodate a wide range of product combinations, and minimize test costs.In addition, probers are required to have high-precision contact, high-speed wafer handling, ease of operation, and the ability to withstand loads and perform high-precision testing in order to adapt to various test environments, high-speed probe mark inspection, high speed and low vibration, and the ability to support a variety of network environments.

[0004] The prober has drive axes such as the X, Y, Z, and θ axes, holds the wafer on a wafer chuck on an XY stage, and drives the XY stage in the X and Y directions (X and Y axis directions) to position it. The XY stage is driven by rotating a ball screw with a motor or by using a linear motor. The wafer then moves in the Z and θ axis directions, making electrical contact with the probe needles. Typically, the XY stage is moved by rotating a ball screw with a motor.

[0005] In tests that measure electrical characteristics by bringing probe needles into contact with a semiconductor wafer, the semiconductor wafer is always elevated to a predetermined position to ensure optimal contact. The optimal elevation amount is achieved by controlling the motor current and torque of the motor that drives the wafer chuck.

[0006] In other words, the prober maintains the wafer contact state by exciting the motors of each drive axis. In particular, the motors that maintain the height during contact (device test time) while withstanding the load have the motor excitation brake turned on, and are excited more strongly than when the wafer chuck is moving, consuming more power during the holding time.

[0007] Patent Document 1 describes a prober in which, in order to reduce power consumption and increase load capacity, the wafer chuck is raised by overtravel using a motor, and then lowered a predetermined amount and held in a predetermined position.

[0008] Japanese Patent Application Laid-Open No. 2022-82170

[0009] In the above-mentioned prior art, the one described in Patent Document 1 does not fully consider the following: a high load is applied to each drive shaft during wafer contact, causing the shaft to shift in position, resulting in a tracking error; heat generated by the motor causes expansion of prober parts near the motor, resulting in a deterioration in contact accuracy; hunting (vibration) causes unstable wafer contact; and so on.

[0010] SUMMARY OF THE INVENTION An object of the present invention is to provide a prober which solves the above-mentioned problems of the prior art, greatly reduces power consumption, improves positioning accuracy, and realizes high-precision, low-vibration contact.

[0011] In order to achieve the above object, the present invention provides a prober that holds a wafer having electrode pads of semiconductor chips on a wafer chuck and moves upward to electrically contact the electrode pads with probe needles of a device measuring instrument, the prober comprising: an XY stage on which a Zθ stage having the wafer chuck mounted; guides that guide drive axes of the wafer chuck in the X-, Y-, θ-, and Z-axis directions; a prober control unit that drives a motor to drive the XY stage in the X and Y-axis directions to a predetermined position corresponding to the device measuring instrument and moves the Zθ stage upward in the Z-axis direction to electrically contact the electrode pads with the probe needles; and a brake that is attached to at least one of the guides and holds the attached drive axis and fixes it to the guide, the motor having a motor excitation brake function, and after the contact is made, the prober control unit turns on the brake and turns off the motor excitation brake of the motor corresponding to the drive axis to which the brake is attached.

[0012] Furthermore, in the above prober, it is preferable that the brake is an air brake that uses compressed air as a pressure source.

[0013] Furthermore, in the above prober, it is preferable that the air brake is attached to the guide that guides the drive shaft in the Z-axis direction.

[0014] Furthermore, in the above prober, it is preferable that the supply and cutoff of the compressed air of the air brake is controlled by the prober control unit using an electromagnetic valve.

[0015] Furthermore, in the above prober, it is preferable that the compressed air is supplied from the pressure source, the pressure of which is reduced and adjusted via a regulator, and the compressed air passes through a check valve and reaches the electromagnetic valve.

[0016] Furthermore, in the above prober, it is preferable that the compressed air be branched between the regulator and the check valve so that it can be used by other mechanisms.

[0017] Furthermore, in the above-described prober, it is preferable that the prober control unit turns on the motor excitation brake of the motor that moves the Zθ stage upward in the Z-axis direction when the Zθ stage is decelerated, and after the Zθ stage moves upward in the Z-axis direction and stops, turns on and maintains the air brake, and excites the motor excitation brake until the air brake is turned on.

[0018] According to the present invention, power consumption can be significantly reduced, positioning accuracy can be improved, and high throughput can be achieved by preventing misalignment and operation stoppage of the stage 22 due to high-precision contact, impact during contact, disturbance during contact (high-voltage measurement), etc.

[0019] 1 is a block diagram showing the configuration of a brake mechanism of a prober according to one embodiment of the present invention; 2 is a block diagram showing the system configuration of a prober according to one embodiment; 3 is a block diagram explaining the relationship between the motors of each drive axis and the objects they drive in a prober according to one embodiment; 4 is a cross-sectional view and a perspective view showing the details of a wafer test unit; 5 is a graph showing the relationship between the movement speed of a Zθ stage, the excitation timing of a Z-axis motor, and power consumption according to a conventional technology; 6 is a graph showing the relationship between the movement speed of a Zθ stage, the excitation timing of a Z-axis motor, and power consumption according to one embodiment;

[0020] FIG. 1 is a block diagram showing the configuration of a brake mechanism of a prober according to an embodiment of the present invention, and FIG. 2A is a block diagram showing the system configuration of the prober. FIG. 2B is a block diagram explaining the relationship between the motors of each drive axis and the objects they drive in FIG. 2A. FIG. 3 is a cross-sectional view and a perspective view showing details of a wafer test unit. High throughput is required in semiconductor manufacturing equipment such as probers, and wafer test systems improve test throughput by simultaneously testing multiple chips with a single contact between a probe needle 26 and an electrode pad (not shown).

[0021] In recent years, the number of chips to be tested simultaneously has tended to increase, and the number of probe needles 26 is at least several hundred, so the end position of movement must be set to a predetermined value so that reliable electrical contact is achieved between all probe needles 26 and the electrode pads.

[0022] Therefore, when there are many probe needles 26, a high load is applied to each of the X, Y, Z, and θ drive axes during wafer contact. In this case, during wafer testing (operation), the drive axis motors are constantly excited to maintain the axis positions, and this power consumption accounts for a large proportion of the prober's power consumption.

[0023] In this embodiment, a brake mechanism is added to hold and fix at least one of the drive axes in the X, Y, θ, and Z axes, and after the wafer W is brought into contact with the probe needles 26 (during wafer testing), the motor excitation brake of the drive axis to which the brake mechanism is added is turned off, and the prober controls the brake mechanism. Note that the drive axes in the X (Y, θ, Z) axes are sometimes referred to as X (Y, θ, Z) drive axes.

[0024] 2A and 3, the wafer test section is configured to include an XY stage 22, a Zθ stage 21, a wafer chuck 20, probe needles 26, a probe card 25, etc. The XY stage 22, which holds the wafer W on the wafer chuck 20, is driven and positioned by an X motor and a Y motor. Similarly, the Zθ stage 21 is driven by a Z motor and a θ motor.

[0025] 2B , movement of the XY stage 22 and the Zθ stage 21 in the X-, Y-, and Z-axis directions is achieved by rotating a ball screw 23a with a motor 27 and feeding a stage 23b to which a ball nut is fixed. While the X-, Y-, and Z-axes are linear axes, the θ-axis is a rotational axis, so the ball screw 23a is not required. There are no particular limitations on the method for driving the θ-axis. For example, the rotational axis of the θ motor and the stage may be coupled together with a coupling to directly transmit rotation. Alternatively, a reducer (not shown) may be provided between the rotational axis of the θ motor and the stage, if necessary, to improve the angular resolution of the stage. Alternatively, a built-in motor may be used, integrating the rotor of the θ motor with the rotational axis of the stage.

[0026] When full-closed control is performed using the motor 27 as a servo motor, the stage is moved by rotating the ball screw 23a using the motor 27, and whether the movement has been performed accurately as commanded, that is, the position of the stage 23b, is detected by a position detector 24 (e.g., a linear scale). The detected stage position information and motor angle information obtained by an angle detector 28 (e.g., a rotary encoder) provided on the motor 27 are input to a position information acquisition unit 30-1 of the driver 30. The motor control unit 30-2 calculates and supplies a drive current to the motor 27 based on the stage position information and motor angle information, thereby driving the stage 22 to a predetermined position. Note that the position detector 24 may be omitted when controlling the angle of the θ axis, which is the rotation axis.

[0027] The motor 27 in this embodiment is not limited to a servo motor, and a stepping motor may also be used. When using a stepping motor as the motor 27 for open-loop control, a position detector 24 capable of acquiring position information over the entire movable range of the stage, such as a linear scale, is not required. However, a position detector 24 is required to detect one or more specific positions (specific angles for the θ axis) of the stage, i.e., the origin position of the stage. Examples of position detectors for detecting specific positions (angles) include contact-type (mechanical) limit switches and non-contact-type proximity sensors (eddy current, capacitance, magnetic, etc.). An appropriate detector can be selected depending on the positioning accuracy and the usage environment. In open-loop control using a stepping motor, the motor angle when the stage is at the origin position (angle) is input to the position information acquisition unit 30-1 of the driver 30. Using this as a reference angle, the motor control unit 30-2 calculates the rotation angle relative to the reference angle required to position the stage at a predetermined position (angle), and rotates the stage by a fixed angle by sequentially switching the phases to be excited in the motor.

[0028] In the manner described above, the prober control unit 10 drives the XY stage 22 to a predetermined position corresponding to the device measuring instrument 29. After positioning the XY stage 22 at the predetermined position, the prober control unit 10 receives a command from the device measuring instrument 29 via the tester communication unit 10-1 and moves the wafer W held by the wafer chuck 20 upward in the Z-axis direction by the Zθ stage 21.

[0029] Then, the drive control unit 10-2 electrically contacts the electrode pads (not shown) formed on the wafer W with the probe needles 26, completes the contact, and transmits a signal indicating the contact state to the device measuring instrument 29. The operation of contacting the electrode pads with the probe needles 26 is performed by detecting the positions of the probe needles 26 and the wafer W, and then rotating the Zθ stage 21 as necessary so that the arrangement direction of the electrode pads of the semiconductor chip coincides with the arrangement direction of the probe needles 26.

[0030] After the prober control unit 10 moves the wafer W held by the wafer chuck 20 to a predetermined position so that the electrode pads are positioned below the probe needles 26, the prober control unit 10 raises the wafer W held by the wafer chuck 20 by the Zθ stage 21 to bring the electrode pads into contact with the probe needles 26. The end position of the lift is set so that reliable electrical contact is achieved between all of the probe needles 26 and the electrode pads.

[0031] The device measuring instrument 29, which has confirmed the contact state based on the contact completion signal from the prober control unit 10, applies and supplies various test signals as measurement voltages from electrode pads formed on the wafer W via terminals connected to the probe needles 26. The device measuring instrument 29 then receives and analyzes signals output from the semiconductor chip to perform a device test to determine whether the semiconductor chip operates normally.

[0032] 1 and 3, prober axis 40 refers to the X, Y, and Z drive axes of wafer chuck 20, and guides 41 refer to a linear guide (not shown) that guides XY stage 22 in the horizontal direction and a rod (not shown) that guides Zθ stage 21 in the vertical direction. XY stage 22 is driven along the linear guide by motor 27 (FIG. 2), and Zθ stage 21 is similarly driven along the rod by a Z-axis motor (not shown).

[0033] Wafer contact can be unstable due to misalignment of the X, Y, and Z drive axes caused by high loads, heat generation, and hunting (vibration) from the motors driving each drive axis. Furthermore, noise generated by each motor can adversely affect wafer testing. Therefore, this embodiment provides a brake mechanism that fixes at least one of the X, Y, and Z drive axes to the guide 41, thereby eliminating the need to energize each motor during contact (device test time). It is particularly preferable to provide a brake mechanism on at least the Z drive axis.

[0034] 1, the air brake 50 is provided on the guide 41 and may be any mechanism that holds the prober shaft 40, which is each drive shaft, to fix or release its position, and fixes the linear guide and / or rod. For example, the air brake 50 may be a brake that uses compressed air to operate a brake cylinder (not shown), or an electromagnetic brake that applies the brake using electromagnetic force generated by energizing a coil.

[0035] In the case of an electromagnetic brake, a non-excitation actuated brake that applies the brake when the current is cut off is preferable from the viewpoint of energy saving. Furthermore, the brake that fixes the X and Y drive axes does not have to fix the guide 41 (linear guide), but an electromagnetic brake or clutch that stops the rotation of the ball screw 23a and motor 27 and fixes the XY stage 22 may be provided.

[0036] Figure 1 shows an air brake 50, which can provide a strong braking force. Figure 1 also shows a double type that applies braking by clamping the guide 41 from both sides. The air brake 50 has a solenoid valve 62 that controls the supply and cut-off of compressed air by the prober control unit 10. The solenoid valve 62 may be a double type with two lines of compressed air as shown in Figure 1, or a single type with one line.

[0037] Compressed air is supplied from a pressure source 65 stored in an air tank or the like by a compressor, and the pressure is reduced and adjusted via a regulator 64. The compressed air then passes through a check valve 63 and reaches the solenoid valve 62. If other mechanisms 70 also need to use the same pressure source 65, the air pressure circuit is branched between the regulator 64 and the check valve 63 so that the air can be used by the other mechanisms 70. By providing the check valve 63, even if there is a branch downstream of the regulator 64 to a mechanism 70 other than the brake mechanism, a drop in pressure to the brakes can be prevented when the other mechanism 70 operates. The check valve 63 also has the function of maintaining the state of the air brake 50 if the supply of compressed air from the pressure source 65 is cut off due to a problem or other reason.

[0038] The other mechanism 70 is, for example, a loader that performs wafer transport operations, etc., and the check valve 63 allows the air pressure to the air brake 50 to be maintained at all times during wafer contact, even when the loader is performing wafer transport operations, etc., and stable contact accuracy can be maintained.

[0039] The compressed air that has passed through the check valve 63 passes through the A and / or B ports of the solenoid valve 62. The pressure at each port is monitored by the prober control unit 10 via pressure sensors 61-1 and 61-2. The air brake 50 is turned on and the brake function is activated when compressed air is supplied from each port via speed controllers 60-1 and 60-2. The speed controllers 60-1 and 60-2 are flow control valves that are attached to the solenoid valve 62 and regulate the operating speed of the air brake 50 by restricting the amount of compressed air flowing.

[0040] FIG. 4 is a time graph showing the relationship between the movement speed of the Zθ stage 21, the timing of excitation of the motor excitation brake of the Z-axis motor, and power consumption when maintaining wafer contact by exciting the motors of each drive axis in the prior art. (The explanation assumes that the prober axis 40 is the Z-axis.) The position of the prober axis 40 (the Z-axis in FIG. 5 ) is determined by turning on the motor excitation brake of the Z-axis motor when the movement speed of the Zθ stage 21 approaches a predetermined position and decelerates. When the prober axis 40 (the Z-axis) approaches a predetermined position, the position is maintained by the motor excitation brake. In other words, the Z-axis motor performs position maintenance control (servo lock) after positioning is completed. In other words, the Z-axis motor realizes the motor excitation brake through the servo lock function. The motor excitation brake of the Z-axis motor is maintained even after the Zθ stage 21 stops. The Z-axis motor, which maintains the height during contact (device test time) with the motor excitation brake, is excited more strongly than when the wafer chuck 20 is moving, and power consumption during the maintenance period is greater. Although the above example uses a servo motor as the Z-axis motor, even if a stepping motor is used as the Z-axis motor, a specific phase of the motor must continue to be excited in order to maintain the position. As with the case of a servo motor, current must continue to flow through the motor even after positioning is complete.

[0041] The power consumption temporarily increases during the time from when the Zθ stage 21 decelerates to when it stops, due to the amount of power consumed when the motor excitation brake of the Z-axis motor is turned ON, in addition to the amount consumed when the Zθ stage 21 moves. After the Zθ stage 21 stops, a certain amount of power is required even if there is no change in the load required for contact due to external forces such as misalignment of the axis, hunting (vibration), impact, or motor heat generation.

[0042] 5 is a time graph showing the relationship between the movement speed of the Zθ stage 21, the excitation timing of the Z-axis motor, and power consumption when using the air brake 50 in one embodiment. (The explanation assumes that the prober axis 40 is the Z-axis.) The motor excitation brake of the Z-axis motor is turned ON when the position of the prober axis 40 (the Z-axis in FIG. 5) approaches a predetermined position in the Z-axis direction and the movement speed of the Zθ stage 21 decelerates. However, after the Zθ stage 21 stops, the air brake 50 is turned ON and the excitation of the Z-axis motor is turned OFF.

[0043] To ensure reliable operation, the Z-axis motor is energized until the air brake 50 is turned on. The position of the prober axis 40 (Z-axis in FIG. 5) is maintained only by the air brake 50. After that, the Z-axis motor is turned off, so power consumption is approximately 0 W.

[0044] Below, an example based on the results of an experiment will be described. Figure 6 is a graph showing a comparison of power consumption between a conventional technique for energizing the motors of each drive shaft during contact and a case where the air brake 50 according to the example is used. Figure 6 shows the case where wafer contact was performed on a chip with an index size of approximately 10 x 10 mm. As shown in Figure 6, during the movement of the index size, which is a short period of time, the power consumption is the same when using the conventional technique for energizing the motors and when using the air brake 50. However, during measurement, which is a long period of time, the power consumption can be significantly reduced by using the air brake 50.

[0045] Specifically, the power reduction when using the air brake 50 is 889.14 kWh per year, which is ２ This is equivalent to a reduction of 293.416 kg, and is also effective in reducing greenhouse gas emissions as part of efforts to address environmental issues (measures against global warming).

[0046] The prober of this embodiment not only significantly reduces power consumption, but also, as shown in FIG. 6, after the Zθ stage 21 is raised in the Z-axis direction and stopped, the air brake 50 is turned on and maintained, and thereafter the Z-axis motor is excited until the air brake 50 is turned on.

[0047] Therefore, the prober can prevent a high load from being applied to each drive axis during wafer contact, which can cause the axis to shift position, resulting in tracking errors, a deterioration in contact accuracy, and unstable wafer contact due to hunting (vibration).

[0048] Furthermore, the prober of this embodiment can prevent the expansion of prober parts near the motor due to heat generated by the motor, noise to the device measuring instrument 29, and conversely, noise from the device measuring instrument 29 being mixed into the signal of the position detector 24, thereby preventing operation stoppages and achieving high testing efficiency, high throughput, and high precision for the wafer W.

[0049] 10... Prober control unit 10-1... Tester communication unit 10-2... Drive control unit 20... Wafer chuck 21... Zθ stage 22... XY stage 23a... Ball screw 23b... Stage 24... Position detector 25... Probe card 26... Probe needle 27... Motor 28... Angle detector 29... Device measuring instrument 30... Driver 30-1... Position information acquisition unit 30-2... Motor control unit 40... Prober axis 41... Guide 50... Air brake 60-1... Speed ​​controller 60-2... Speed ​​controller 61-1... Pressure sensor 61-2... Pressure sensor 62... Solenoid valve 63... Check valve 64... Regulator 65... Pressure source 70... Other mechanism W... Wafer

Claims

1. A prober that holds a wafer having electrode pads of a semiconductor chip on a wafer chuck and moves upward to electrically contact the electrode pads with probe needles of a device measuring instrument, comprising: an XY stage on which a Zθ stage having the wafer chuck mounted; guides that guide the drive axes of the wafer chuck in the X, Y, θ, and Z directions; a prober control unit that drives a motor to drive the XY stage in the X and Y directions to a predetermined position corresponding to the device measuring instrument and moves the Zθ stage upward in the Z direction to electrically contact the electrode pads with the probe needles; and a brake that is attached to at least one of the guides and holds and fixes the attached drive axis to the guide, wherein the motor has a motor excitation brake function, and after the contact is made, the prober control unit turns on the brake and turns off the motor excitation brake of the motor corresponding to the drive axis to which the brake is attached.

2. The prober according to claim 1, wherein said brake is an air brake that uses compressed air as a pressure source.

3. The prober according to claim 2, wherein the air brake is attached to the guide that guides the drive shaft in the Z-axis direction.

4. The prober according to claim 2, wherein the supply and cutoff of the compressed air to the air brake is controlled by the prober control unit using an electromagnetic valve.

5. The prober according to claim 4, wherein the compressed air is supplied from the pressure source, the pressure of which is reduced and adjusted via a regulator, passes through a check valve, and reaches the solenoid valve.

6. The prober according to claim 5, wherein the compressed air is branched between the regulator and the check valve for use by other mechanisms.

7. A prober according to any one of claims 3 to 6, characterized in that the prober control unit turns on the motor excitation brake of the motor that moves the Zθ stage upward in the Z-axis direction when the Zθ stage is decelerated, and after the Zθ stage moves upward in the Z-axis direction and stops, turns on and maintains the air brake, and excites the motor excitation brake until the air brake is turned on.

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