JPH08250558A - Wafer prober - Google Patents

Abstract

PURPOSE: To obtain the wafer prober, which has the excellent positioning controllability at a high speed in high accuracy and is suitable for setting in a clean room. CONSTITUTION: A wafer, which is to become the object for inspection, is sucked and held on the upper surface of an inspecting table 16. The inspecting table 16 is horizontally moved in the X-Y directions by linear synchronous motors 52 and 60. Thus, the inspecting position of the wafer is changed and adjusted. The linear synchronous motors 52 and 60 can generate and transmit the driving power in the straight-line direction direcly. Therefore, this device has the higher rigidity in comparison with a driving transmission mechanism comprising conventional rotary motors and ball screws, and the high-speed response control can be performed. Furthermore, the linear synchronous motor can be constituted in the thin type in comparison with the case of the rotary motor. The center of variable mass and the driving center can be brought close, the attitude change caused by the couple of force is decreased and the positioning accuracy and the high-speed follow-up property are improved. Furthermore, the linear synchronous motor has no consumption such as ball screws and has no requirement for oil feeding Therefore, the motor has the excellent maintenability and is suitable for use in a clean environment.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wafer prober, and more particularly to a wafer prober for inspecting electric characteristics of a large number of electric element circuits formed on the surface of a semiconductor wafer.

[0002]

2. Description of the Related Art A large number of identical electric element circuits are formed on the surface of a semiconductor wafer. Before cutting the electric element circuits into chips, a wafer prober is used to inspect the formation quality of each electric element circuit. The good or bad of the wafer is judged by a so-called wafer inspection device.

The wafer prober is composed of a cassette stock section, a wafer transfer section, an inspection table, a wafer inspection section, and the like. Is carried to the inspection table for inspection. The inspection table is composed of a wafer suction stage for sucking and holding a wafer and an XYZ moving mechanism.
The horizontal movement in the direction and the vertical movement in the Z direction are performed. In general, X
The moving mechanism in the Y direction is composed of a rotary motor and a ball screw or the like that converts the rotary motion into a straight line.

In addition to the structure of the inspection table, an inspection table using a two-axis simultaneous linear pulse motor is also known. This 2-axis simultaneous linear pulse motor has an X-axis forcer and a Y-axis forcer, which are composed of one permanent magnet and two electromagnets, arranged orthogonally to each other, and is formed on a base plate in which uneven teeth are formed on a soft magnetic iron plate having high magnetic permeability. X-
It is designed to run freely in the two Y-axis directions, and the suction stage provided on the X-axis forcer and the Y-axis forcer is attached to the X-axis forcer.
It can be moved horizontally in the Y plane. A gap is maintained between the forcer and the base plate by an air bearing.

[0005]

However, a conventional wafer prober using a rotary motor, a ball screw, etc., has a maximum speed limit due to problems such as dangerous rotation speed and vibration of the ball screw. Since various components such as couplings and nuts are present in the
The rigidity of the mechanism is low, which makes it difficult to perform high-speed response control. Moreover, since the configuration including the rotary motor and the ball screw is large in size, the center of gravity (center of movable mass) of the table to be moved and the point (driving center) to which the driving force is applied are relatively distant from each other. There is a problem in that the posture of the table changes due to a couple of forces at the time of starting and stopping the driving, resulting in poor positioning accuracy. This leads to a long positioning establishment time and a long time required to inspect the electric element circuit.

Further, the ball screw which is driven at a high frequency has a problem in terms of service life and also has a problem from the viewpoint of maintainability because it must be constantly lubricated.
Further, there is a problem that a conventional wafer prober composed of a drive system requiring lubrication is not suitable for a clean room installation in terms of dust generation and is large as a device installed in a limited space such as a clean room. .

On the other hand, the conventional inspection table using the two-axis simultaneous linear pulse motor has a structure in which the attraction force of the magnetic force and the buoyancy of the air of the air bearing maintain a balance in the height direction. When a strong force is applied from above,
There is a problem that the balance is lost and tilts, or it falls in the Z direction. Therefore, this problem becomes remarkable because the number of probe needles is increasing and the force applied to the probe needles is increasing in response to the recent increase in the number of pins and the simultaneous measurement of a large number of pins. Is not suitable for use.

In addition, since the conventional 2-axis simultaneous linear pulse motor is open loop control, there is a problem that the positioning accuracy is poor. The present invention has been made in view of such circumstances, and an object thereof is to provide a wafer prober which is excellent in high-speed and high-accuracy positioning controllability and which is suitable for installation in a clean room.

[0009]

In order to achieve the above-mentioned object, the present invention is a wafer prober for inspecting the quality of an electric element circuit formed on a semiconductor wafer, and an inspection table for adsorbing and holding a wafer to be inspected. And a first linear synchronous motor that horizontally moves the inspection table in the X-axis direction, and a second linear synchronous motor that horizontally moves the inspection table in the Y-axis direction. .

[0010]

According to the present invention, the semiconductor wafer to be inspected is suction-held on the upper surface of the inspection table of the wafer prober, and the inspection table is moved by the linear synchronous motor.
The inspection position of the wafer is changed and adjusted by horizontally moving in the X-axis and Y-axis directions. Since the linear synchronous motor can directly generate and transmit the propulsive power in the linear direction, it has higher rigidity than the drive transmission mechanism including the conventional rotary type motor and the ball screw, and high-speed response control becomes possible. Moreover, there is no limit on the maximum speed due to the dangerous speed as in the case of the rotating body, and the maximum speed can be dramatically improved according to the frequency of the control circuit.

Since the linear synchronous motor can be made thinner than the rotary type motor, the inspection table can be made thinner. As a result, the center of the movable mass and the center of the drive can be brought close to each other, the posture change due to the couple force at the time of starting and stopping the drive is reduced, the positioning accuracy and the high-speed followability are improved, and the size of the entire wafer prober apparatus is reduced. Can be realized.

Furthermore, since the linear synchronous motor does not wear like a ball screw and does not require lubrication, it has excellent maintainability and is suitable for use in a clean environment. Further, according to the present invention, the position of the inspection table moved by the linear synchronous motor is detected by the position detection means, and the control means performs feedback or feedforward control. Therefore, high-speed and high-precision positioning is possible. Become.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of a wafer prober according to the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 is an external perspective view showing an embodiment of a wafer prober according to the present invention. The wafer prober 10 shown in the figure mainly includes a cassette stock unit 12, a wafer transfer belt 14, and a wafer transfer belt 1.
4, an inspection table 16, an inspection unit 18, and the like.

The cassette stock unit 12 has an elevator mechanism (not shown), and a cassette 22 is placed on a plate 20 which moves up and down by the operation of this elevator mechanism. The cassette 22 stores a plurality of wafers 24. Has been done. Wafers 2 stored in the cassette 22
4 is a conveyor belt 14 by the load pusher 26,
It is pushed toward 14, and is carried forward by the conveyor belts 14, 14. Then, the wafer 24 is transferred to the transfer arm 2
8 is suction-held by a suction collet 29 provided at the tip portion of 8, and is moved onto the inspection table 16 by the transfer arm 28.

The inspection table 16 is provided on an XYZ moving mechanism, and the XYZ moving mechanism allows the XY table to be moved.
It is moved horizontally in the same direction and is moved up and down in the Z direction. FIG. 2 is a perspective view for explaining the structure of the inspection table 16 applied to the wafer prober of FIG. The inspection table 16 shown in the figure includes a Y-axis surface plate 50, a Y-axis linear synchronous motor 52, Y-axis linear guides 55 and 55,
Y-axis scale unit 56, X-axis surface plate 58, X-axis linear synchronous motor 60, X-axis linear guides 62, 62,
It is composed of an X-axis scale unit 64, a wafer suction stage 66, and the like.

The Y-axis linear synchronous motor 52 is inserted into a gap between a stator (stator) 53 having a plurality of permanent magnets 53a, 53a ... And a mover 54 composed of an electromagnet coil. Since the linear synchronous motor 52 having the double-sided excitation structure can cancel the magnetic attraction force from both upper and lower sides, it does not burden the support structure.
The thrust ripple (thrust distribution generated by the movement of the mover) is also smooth.

The Y-axis linear synchronous motor 52 is fixed on the Y-axis surface plate 50. The Y-axis linear synchronous motor 52 is sandwiched between the Y-axis linear synchronous motor 52 and the Y-axis linear synchronous motor 52. 55 are arranged. A mover 54 of the Y-axis linear synchronous motor 52 and a Y-axis linear guide 55,
An X-axis surface plate 58 is mounted on the bearing guides 55a, 55a of the 55, and a Y-axis linear synchronous motor 52 is mounted.
Driving the linear rails 55b, 55b
The position in the Y-axis direction can be freely moved along. And
The Y-axis scale unit 56 detects the position in the Y-axis direction and outputs the position detection signal to a prober control unit (not shown) described later.

On the X-axis base plate 58, an X-axis linear synchronous motor 60 and X-axis linear guides 62, 62 are provided.
A wafer which is arranged in the same manner as in the case of the Y-axis and which holds the wafer 24 by suction on the mover 61 of the X-axis linear synchronous motor 60 and the bearing guides 62a, 62a, 62a of the X-axis linear guide. A suction stage 66 is mounted. The configuration of the X-axis linear synchronous motor 60 is the same as the configuration of the Y-axis linear synchronous motor 52 described above.

The X-axis scale unit 64 is X
The position in the axial direction is detected and the position detection signal is output to the prober control unit described later. The prober control unit,
A drive circuit that applies an exciting current to the X-axis linear synchronous motor 52 and the Y-axis linear synchronous motor 60, and a mover 54 based on position detection signals from the Y-axis scale unit 56 and the X-axis scale unit 64. It includes a linear scale circuit that detects the position of 61 with high resolution, and a feedback circuit that applies an error signal to the drive circuit by taking the difference between the position information of the linear scale and the commanded position input. In this way, the inspection table 16 can be arbitrarily moved in the XY directions with high accuracy. Note that feedforward control may be performed for high-speed and high-accuracy positioning control.

Further, as shown in FIG. 2, the inspection table 1
6, suction holes 67, 67, 67 for vacuum suction of the wafer 24 are formed in the central portion of the chuck top 66a, and the vacuum suctioned wafer 24 is placed in the suction ports 67, 67, 67. A rod (not shown) for pushing up from 16 is provided so as to be able to move up and down. FIG.
Returning to, the wafer inspection unit 18 has a microscope 30, and a probe stage 32 is formed below the microscope 30. A probe card (not shown) corresponding to the wafer 24 to be inspected can be selected and attached to the probe stage 32.

After the inspection, the wafer 24 is moved from the inspection table 16 onto the conveyor belts 14, 14 by the unload arm 36, and stored in the original shelf of the cassette 22 by the unload pusher 38. . The loading, transporting, and unloading of the wafer 24 are not limited to the methods and means described above, and other methods and means may be used.

Wafer prober 1 constructed as described above
The operation of 0 will be described. First, the wafer 24 is taken out from the cassette 22, and the wafer 24 is moved by the transfer belts 14 and 14 and the transfer arm 28.
6, and the wafer is sucked onto the suction stage 66. After that, the inspection table 16 is moved in the direction of the probe card based on the image data picked up by a CCD camera (not shown) to perform fine alignment adjustment. Then, the probe needle of the probe card can be brought into contact with the electrode pad of the wafer 24 to sequentially inspect each element circuit.

FIG. 3 is a graph showing the positioning accuracy of the inspection table by the drive system using the conventional rotary type motor and the ball screw and the positioning accuracy of the inspection table by the linear synchronous motor of FIG. The horizontal axis of the figure shows the time required for positioning, and the vertical axis shows the position. A curve (a) is a graph when the drive system using a conventional rotary motor and a ball screw is moved from the initial position P0 to the command position P1. Since the positioning accuracy is poor due to the decrease in rigidity due to the power transmission mechanism and the posture change due to the couple at the start of driving, it is necessary to complete accurate positioning at the command position P1.
It takes time τ _a .

Curve (b) is a linear synchronous motor
It is a graph when moving from the initial position P0 to the command position P1. The linear synchronous motor has high rigidity because it does not need a linear motion converting means, and has a thin structure, and since the center of the movable mass is close to the center of the drive, the posture change due to a couple at the start of driving is small. Therefore, the positioning accuracy is improved and the command position P1
The time τ _b for completing accurate positioning is extremely shorter than the time τ _a . As a result, the wafer inspection time can be significantly shortened and high throughput can be achieved.

As described above, by directly incorporating the linear synchronous motors 52 and 60 in the drive system of the inspection table 16, a mechanism portion (ball screw or the like) for converting a rotational force into a thrust like a conventional rotary type motor. Can be omitted, there is no loss required for it, high-speed response control is possible, the number of parts is reduced, and reliability is improved. Also, there is no limit on the maximum speed that is limited by the dangerous speed like in the case of a rotating body,
The maximum speed of the linear synchronous motor depends on the frequency of the control circuit and the like. Therefore, with a suitable control circuit, a maximum speed of several times to 10 times that of the conventional one can be achieved.

Moreover, since the linear synchronous motor can be made thin, the entire moving table can be designed thin.
As a result, a driving force can be applied to a position close to the center of gravity (center of movable mass) of the wafer suction stage 66, and posture changes due to couples at the time of starting and stopping driving are reduced,
Positioning accuracy and high-speed followability are improved.

[0027]

As explained above, according to the wafer prober of the present invention, the inspection table is horizontally moved in the XY directions by the linear synchronous motor.
Positioning accuracy and high-speed followability are improved, and high-speed response control is possible. Moreover, the maximum speed can be dramatically improved according to the frequency of the control circuit. This allows
High accuracy and high throughput can be realized.

Further, since the linear synchronous motor does not wear or wear like a ball screw and does not require lubrication, it has excellent maintainability and can be applied to use in a clean environment.
Further, since the linear synchronous motor can be made thinner than the conventional rotary type motor, it contributes to downsizing of the entire wafer prober apparatus. As a result, it is possible to effectively utilize the clean room with high equipment cost.

[Brief description of drawings]

FIG. 1 is an external perspective view showing an embodiment of a wafer prober according to the present invention.

FIG. 2 is an inspection table 16 of the wafer prober of FIG.
Perspective view for explaining the configuration of

FIG. 3 Positioning accuracy of an inspection table by a drive system using a conventional rotary motor and a ball screw (curve (a))
And a graph for comparing the positioning accuracy (curve (b)) of the inspection table by the linear synchronous motor

[Explanation of symbols]

 10 ... Wafer prober 12 ... Cassette stock unit 14 ... Conveyor belt 16 ... Inspection table 18 ... Inspection unit 24 ... Wafer 52 ... Y-axis linear synchronous motor 56 ... Y-axis linear scale 60 ... X-axis linear synchronous motor 64 ... Linear scale for X axis

Claims (2)

[Claims] 1. A wafer prober for inspecting the quality of an electric element circuit formed on a semiconductor wafer, comprising: an inspection table for sucking and holding a wafer to be inspected; and a horizontal movement of the inspection table in the X-axis direction. 1. A wafer prober comprising: a first linear synchronous motor; and a second linear synchronous motor that horizontally moves the inspection table in the Y-axis direction. 2. A first position detecting means for detecting a position in the X-axis direction of the inspection table moved by the first linear synchronous motor, and the inspection moved by the second linear synchronous motor. Second position detecting means for detecting the position of the work table in the Y-axis direction, and the first and second position detecting means are connected to the first position detecting means.
2. The wafer prober according to claim 1, further comprising: a control unit configured to perform feedback or feedforward control of driving of the second linear synchronous motor.