JP2979277B2 - Probe method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

FIELD OF THE INVENTION The present invention relates to a probe method .

[0002]

2. Description of the Related Art In a semiconductor device manufacturing process,
After the wafer manufacturing process is completed and IC chips are completed in the wafer, short-circuiting and opening of the electrode pattern and IC
An electrical measurement called a probe test is performed by a probe device to examine the input / output characteristics of the chip and the like, and the quality of the IC chip is determined in the state of the wafer. Thereafter, the wafer is divided into IC chips, and the non-defective IC chips are packaged, and, for example, a predetermined probe test is performed to determine the quality of the final product.

As shown in FIG. 6, a conventional probe device is arranged above a wafer holder 1 movable in the X, Y, Z, and θ directions in accordance with an electrode pad arrangement of IC chips in a wafer W. A probe card 12 having the arranged probe needles 11 is arranged. Then, an electrode pad of an IC chip in the wafer W is brought into contact with the probe needle 11, and an electrical measurement is performed by the test head 14 through the contact ring 13.

In order to perform accurate electrical measurement, the probe needle 11 must be reliably brought into contact with the electrode pad. Therefore, the wafer holder 1 is controlled with high accuracy, and the probe needle 11 is controlled before measurement. It is necessary to accurately align the electrode pads with respect to the eleventh electrode pad. On the other hand, since a large number of circuit components and wirings are incorporated in the test head 14, it is difficult to provide a TV camera or the like in the test head 14. Therefore, the optical system unit 15 is located at a position a away from the test head 14. This optical system unit 15
7 is set as an alignment (alignment) area as shown in FIG. 7, and the alignment of the wafer W is performed as follows, for example.

That is, first, a wafer to be aligned is placed on the wafer holding table 1, and a specific point or reference mark formed on the wafer W is moved directly below the optical system unit 15 by moving the wafer holding table 1. The specific point or fiducial mark is recognized by accurately positioning. At this time, the number of pulses from an encoder attached to each of the X-axis and Y-axis motors composed of ball screws is counted, and based on the length between each mark and the number of pulses required to move the length. To determine the travel distance. In FIG. 6, motors and encoders are indicated by reference numerals 18 and 19 only for the X axis.

When measuring the wafer W, the optical system unit 15 recognizes the specific point or the reference mark, for example, a plurality of predetermined positions on the periphery of the wafer W, for example, four positions, and moves the wafer W with respect to the alignment target wafer. Alignment is performed by calculating the difference between. By performing this alignment, the relative position between the probing area and the alignment area, the driving amount of the ball screw, and the like are set so that the positioning of the probe needle 11 and the electrode pad of the IC chip in the probing area is automatically performed. Is set. If the relative positions of the electrode pads and the probe needles 11 are matched, the movement distance has already been grasped in the alignment area. Therefore, by moving the holding table 1 based on the data, all the electrode pads can be moved. Comes into contact with the probe needle 11 accurately.

[0007]

In the above-described apparatus, the data of the wafer holder 1 in the alignment area below the optical system unit 15 is transferred to the probing area below the probe card 12 and used. become. Therefore, if the state of the three-dimensional coordinates in both areas is the same, the wafer moves in the probing area in the same manner as in the alignment area. However, since the state is different as follows, the wafer moves (IC chip movement). An error occurs.

[0008] The above two areas are, for example, about 700 mm.
The position and position of the wafer in the three-dimensional direction are determined by the ball screw processing accuracy and the guide yawing (X
-Y-plane deflection), pitching (front-back tilt)
And low link (tilt around the axis of movement).
The wafer changed its original posture when it moved from the alignment area to the probing area due to the expansion and contraction of the screw and the effect of thermal expansion due to the frictional heat of the ball screw when moving from the alignment area to the probing area. The posture, for example, swinging to the left or right, or leaning back and forth.

The positional accuracy of the wafer holder 1 is as follows.
When the temperature is constant, ± 1 axis (X direction or Y direction)
Although it is about 3 to 5 μm, the accuracy is further deteriorated in consideration of the influence of the environmental temperature change. For example, wafer holder 1
When the set temperature is heated to about 150 ° C., since the thermal expansion coefficient of silicon and the thermal expansion coefficient of the ball screw greatly differ, this must be corrected. This correction is realized under the condition of the constant environmental temperature. For example, when the environmental temperature changes, the change of the thermal expansion of the ball screw according to the temperature change, or the yawing, pitching, and rolling according to the temperature change. The change is an error.

Therefore, even if the wafer holding table 1 is placed at a predetermined position in the probing area, the attitude of the wafer and the I
The position of the C chip is different from the position expected in the alignment area. Further, since the state of the ball screw is different between the probing area and the alignment area due to the influence of machining accuracy, yawing, and the like as described above, the actual amount of movement of the encoder per one pulse is different. Although the above error is not so large, DRA
As devices are becoming more and more highly integrated as M is shifting to 32M and 64M, the size and number of electrode pads are reduced, and the size of such wafers is also increasing. Position error (IC
When the position error of the chip occurs, it is difficult to accurately contact all the electrode pads on the wafer with the electrode pads, and there is a problem that it is not possible to perform highly accurate electrical measurement.

The present invention has been made under such circumstances, and an object of the present invention is to make it possible to always accurately and accurately contact a probe needle with an electrode pad of an object to be inspected, and to perform electrical measurement with high accuracy. It is to provide a probe method capable of performing the above.

[0012]

Means for Solving the Problems of claims 1 invention, numerous
The test object in which the chips to be inspected are arranged vertically and horizontally is held on a holding table driven along a X axis and a Y axis by a motor to which an encoder is connected, and the holding table is intermittently held. Pro performed by moving, electrical measurements of the device under test by sequentially contacting the probe with the electrode pads of the inspection chip
In the probe method , the probe needle and the electrode pad are sequentially
Measurement area that is the range of movement of the test object when making the next contact
The holding table is moved along the X axis in the
Multiple locations separated along the vertical (horizontal) row of the
Image of the device, and an encoder associated with the movement of the holding table at this time.
1 pal based on the number of pulses from
Determining the amount of movement of the holding table in the X-axis direction per scan;
When the probe needle and the electrode pad are sequentially contacted
Move the holding table within the measurement area, which is the range of movement of the test object.
Move along the Y-axis to align the horizontal (vertical)
Images of multiple specific locations that are separated along
The number of pulses from the encoder and the characteristics
Y-axis direction per pulse based on distance between fixed positions
Obtaining the moving amount of the holding table, and within the measurement area
While imaging a specific position on the surface of the test object,
The tip of the probe needle is imaged, and based on the imaging result at this time,
A step of aligning the electrode pad with the probe needle;
After positioning in this process, 1 pal
The amount of movement of the holding table in the X-axis direction per pulse and one pulse
The motor is controlled based on the amount of movement of the holding table in the Y-axis direction
This allows the probe needle to be connected to the electrode pad of the chip under test.
A step of making electrical measurement of the test object by sequentially contacting
It is characterized by including .

[0013]

The recognition means recognizes, for example, a specific position of the surface of the test object placed in the measurement area (probing area) by the recognition means, and moves the holding table to, for example, X on the test object from the previous specific position.
The other specific position separated in the direction is recognized by the recognition means.
At this time, the arithmetic processing unit obtains the number of encoder pulses, and performs this operation in, for example, the Y direction, thereby obtaining the relationship between the length in the X and Y directions on the test object and the number of encoder pulses.

By controlling the motor using this relationship, the test system can be inspected at the time of measurement without being affected by errors included in the absolute coordinates of the control system based on the driving system of the holding table, for example, the processing accuracy and distortion of the ball screw. You can move your body accurately. In addition, by performing relative positioning between the probe needle and the electrode pad in the measurement area, compared with the case of performing alignment in another alignment area, there is no error in the drive system between the areas, which is extremely high. The probe needle and the electrode pad can be accurately contacted.

[0015]

FIG. 1 is an explanatory view schematically showing an entire embodiment of the present invention, and FIG. 2 is a vertical sectional side view showing an upper portion of the embodiment. It is. In this embodiment, the wafer holding table 2 is provided on the X-axis table 3 so as to be movable in the θ direction by a θ moving mechanism (not shown), for example, a heater (not shown).
Built-in. The X-axis table 3 is configured to be able to move in the X-direction while being guided on the Y-axis table 4 by the guide portion 3 a by the X-axis 31 composed of a ball screw. Can be moved in the Y direction while being guided by the guide portion 4a by the Y axis 41 composed of a ball screw.

The X axis 31 is connected to a motor 32 for driving the X axis 31. An encoder 33 is attached to the motor 32. The motor 42 and the encoder 43 are also attached to the Y axis 41.

A probe card 22 attached to an insert ring 21 is disposed above the wafer holder 2, and the insert ring 21 is fixed to the apparatus main body 20. On the upper surface side of the probe card 22, as shown in the upper sectional view of FIG.
Are arranged on the lower surface side of the probe card 22,
Probe needles 25 which are electrically connected to the electrodes 22a and serve as contact means corresponding to the arrangement of the electrode pads on the wafer to be inspected are arranged.

In the gap between the wafer holder 2 and the probe needle 25, openings 51, 5
2 is provided so as to be able to advance and retreat, and both ends of the holding member 5 are guided by two guide rails 53, 53 laid on the inside of the upper surface of the apparatus main body 20.
It is configured to be able to move between the lower side of the probe needle 25 and the corner of the apparatus main body 20 which is out of the elevating area of the wafer holding table 2. The guide rails 53 are provided in combination with an elevating mechanism using, for example, a ball screw (not shown). Therefore, the holding base member 5 can move in the Y and Z directions in this example. However, holding member 5
May be configured to be movable also in the X direction.

At the side end portion of the holding member 5, for example, an alignment capable of switching between low magnification display and high magnification display is formed so that an optical axis is formed in the holding member 5 in the longitudinal direction. CCD camera 61 is mounted, and a half mirror M1 is provided at the center of the holding member 5 so as to reflect the image of the probe needle 25 taken in through the opening 51 and transmit the image to the CCD camera 61. Is provided.

Further, in the holding member 5, a total reflection mirror M2 is disposed at a position opposite to the CCD camera 61 with respect to the half mirror M1 and on the optical axis of the CCD camera 61. The mirror M2 is mounted on the wafer holder 2
After the image on the surface of the upper wafer W is reflected by the half mirror M1 toward the total reflection mirror M2 through the opening 52, the image is totally reflected toward the half mirror M1. In this example, an optical system member is configured by the half mirror M1 and the total reflection mirror M2.

The CCD camera 61 has an image processing unit 62
Is connected, and the image processing section 62 controls the CCD camera 6
1 has a function of binarizing an image taken by 1, and comparing this image with, for example, image data stored in advance to determine whether they match or not. As the image data, for example, low-magnification mode data and high-magnification mode data on a chip or an electrode pad located at an end of an array of IC chips on a wafer as described later correspond to the image data.

An arithmetic processing unit 7 is provided on the output side of the image processing unit 62. The arithmetic processing unit 7 receives pulses from the encoders 33 and 43 and, for example, specifies a pulse on the wafer W. The recognition signal output from the image processing unit 62 is input when the part reaches a predetermined position on the screen, and based on these signals, an encoder for moving the wafer holder 2 between specific positions on the wafer W A function of calculating the number of pulses of 33 or 43, thereby obtaining the relationship between the moving distance of the wafer W and the number of pulses, for example, obtaining the moving distance of the wafer W per pulse in each of the X and Y directions. ing. In this example, recognition means for recognizing the position of the wafer is constituted by the optical system member held by the holding member 5, the CCD camera, and the image processing unit.

The control system of the wafer holding table 1 includes a storage unit 71 for storing the calculation results of the calculation processing unit 7,
At the time of measurement, the motors 32 and 42 are drive-controlled with reference to the data in the storage unit 71, and further, image data from the image processing unit 62, such as an electrode pad, for setting an initial position of the wafer W before measurement. A motor control unit 72 for controlling the motors 32 and 42 and the motor for driving the wafer holder 1 in the θ direction based on the information on the positional deviation from the probe needle 25 to perform the alignment of the wafer W is provided. I have. Although not shown, the motor control unit 72 also has a function of controlling a motor for driving the wafer holder 2 in the Z direction.

The portion other than the probing area (measurement area) in this embodiment will be briefly described. A wafer carrier C for loading and unloading, and a wafer taken out of the carrier C are provided at a position distant from the probing area. A pre-alignment stage 81 for pre-aligning the wafer and a transfer arm 82 for transferring the wafer between the carrier C, the pre-alignment stage 81 and the wafer holding table 2 are provided.

Next, the operation of the above embodiment will be described.
For example, when electrical measurement is performed on an existing wafer of the same type, first, one of the wafer groups is used to determine the amount of movement of the wafer in the probing area and the encoders 33 and 4.
The relationship with the number of pulses of No. 3 is obtained, and the XY coordinate system is checked. Specifically, the transfer arm 82 transfers the wafer W in the carrier C to the pre-alignment stage 81, where the wafer W is aligned with the orientation flat (orientation flat) and then transferred to the wafer holding table 2.

Subsequently, in order to examine the coordinate system of the wafer W in the X direction, the arrangement direction of the IC chips on the wafer W is made to coincide with the X direction (the direction of the X axis 41). This match operation is CC
The rotation is performed by rotating the wafer holder 2 by θ so that the image in the low magnification mode captured by the D camera 61 matches the image data stored in the image processing unit 62.
A specific position on the wafer W that is located away from the wafer W in the X direction, for example, as shown in FIG.
The motors 32 and 42 are driven so that the centers x1 and x2 of the electrode pads located at both ends in the X direction of the C chip 100 are sequentially positioned on the optical axis of the CCD camera 61. When the specific positions x1 and x2 are located on the optical axis of the CCD camera 61, a recognition signal is output from the image processing unit 62 based on the image from the CCD camera 61 as described above. The number of pulses of the encoder 33 for the X-axis 31 required to move the wafer holding table 2 between the specific positions x1 and x2 is counted by the unit 7. And x1,
Since the length between x2 is known in advance, the relationship between the amount of movement of the wafer W in the X direction and the number of pulses in the probing region is determined, and the length in the X direction per pulse is known.

Here, an example of image recognition will be described.
First, by selecting the low magnification mode of the CCD camera 61, the IC chip images located at both ends in the X direction, which are captured by the CCD camera 61, are displayed as shown in FIG. When the predetermined electrode pad P comes to the center of the screen by scanning with respect to the optical axis, the mode is switched to the high magnification mode. Thereby, the enlarged image of the electrode pad P is displayed as shown in FIG. 5, and the recognition signal is output from the image processing unit 62 when the center x1 of the electrode pad P comes to the center of the screen.

In the Y direction, the Y
Similarly, by using the centers of the electrode pads at both ends as specific positions located apart from each other in the same direction and performing the same operation, the relationship between the amount of movement of the wafer W and the number of pulses of the encoder 43 is obtained, and The length in the Y direction is known. The length data per pulse in the X and Y directions is stored in the storage unit 71.

Obtaining such data of the XY coordinate system of the wafer W is performed under the same conditions when actually measuring the wafer W. For example, the wafer W is provided by a heater (not shown) built in the wafer holder 2. This is performed in a state where W is heated to about 150 ° C.

Next, the probe W
Is aligned with respect to. This alignment is performed by the camera 61 in the low-magnification mode, and the wafer holder 2 is moved so that the tips of the probe needles 25 are located within all the electrode pads of the specific IC chip, and the coarse adjustment is performed. Next, the mode is switched to the high magnification mode to perform imaging, and fine adjustment is performed by moving the wafer holder 2 so that the needle tip is located at the center of the specific electrode pad. These adjustments are made in the X, Y, and θ directions. After that, the holding member 5 of the optical system member is retracted along the guide rail 53 to a region outside the probing region by a driving mechanism (not shown), and then the wafer holding table 2 is raised to bring the probe needle 25 into contact with the electrode pad. An electric signal is transmitted and received between the test head 26 and the IC chip to perform an electric measurement.

According to such an embodiment, the I
Using the array pattern of the C chips as a reference scale, how much the wafer W moves and how many encoder pulses are counted is determined by the probing area (the wafer W moves when the wafer W is measured) which is the measurement area of the wafer W. In this case, the wafer holding table 2 is moved when the wafer W is measured based on the data. Accordingly, the processing accuracy of the ball screws 31 and 41 and the silicon and the ball screws 31 and 41 when the wafer W is heated.
Even if errors due to thermal expansion of the wafer W are included in the absolute coordinates of the control system, since the probing area and the alignment area are the same, these errors are included in the movement control of the wafer W during measurement. Not. As a result, the probe needles 25 can be accurately brought into contact with any of the electrode pads on the wafer W, and electrical measurement can be performed with high accuracy.

In the probing area, the probe needle 25
Since the alignment between the probe and the electrode pad is performed, errors in the processing accuracy and distortion of the ball screw between the regions are not included as compared with the case where alignment is performed in another alignment region. 25 can be brought into contact with the electrode pads.

In recognizing the specific position on the wafer W, three or more chips arranged in the X direction (or the Y direction) on the wafer W are set as the specific position and the wafer W
The region may be divided and the relationship between the number of pulses and the length may be examined for each divided region, or a number of marks forming a specific position may be added on a dedicated wafer W not used as a product.

Then, the angle of each chip and each mark on the wafer is also recognized by the image processing unit 62, and when the wafer is at which position, how much the wafer holder 2 should be moved (rotated) in the θ direction. The information in the θ direction may be stored in the storage unit 71, and the θ driving motor may be controlled based on this information when measuring the wafer.
In this way, errors such as distortion of the ball screw can be corrected.

Further, the alignment of the probe tip of the probe needle 25 with the electrode pad is not performed for each measurement of each wafer W, but is performed for the first wafer, and the position is stored. The optical system member may be moved up and down to perform focusing on each of the needle tip and the electrode pad at the time of the alignment, and the needle may be adjusted based on the amount of elevation of the optical system member at this time. Z with previous wafer
The distance in the direction may be stored.

The image of the probe needle and the electrode pad may be captured by separate optical members, or both images may be captured from above the probe needle. Alternatively, a mark whose relative position is fixed may be used instead of the needle point.

The relationship between the number of pulses and the length on the wafer W described above may be appropriately determined in accordance with a change in environmental temperature or the like. For example, the relationship may be determined for each wafer W. As the recognition means, it is preferable to use a CCD camera because the resolution is high, but the present invention is not limited to this. For example, the position of the wafer W may be recognized using a laser interferometer.

[0038]

According to the first aspect of the present invention, the position of the holding table is controlled by controlling the motor so that the two-dimensional position between the tip of the probe needle and the electrode pad is matched in the measurement area. In addition, positioning can be performed with higher accuracy than when positioning is performed in another alignment region. Then, the relationship between the amount of movement of the object to be inspected and the number of pulses of the encoder connected to the motor for driving the wafer holder is grasped, and the holder is moved based on this relationship. Even if an error due to mechanical accuracy or the like is included, the object to be inspected moves so that the position of the object to be inspected and the probe needle are accurately aligned, so that highly accurate measurement can be performed.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention.

FIG. 2 is a longitudinal sectional side view showing a part of the embodiment of the present invention.

FIG. 3 is an explanatory diagram showing an example of a specific position of a semiconductor wafer.

FIG. 4 is an explanatory diagram showing an image in a low magnification mode by a CCD camera.

FIG. 5 is an explanatory diagram showing an image in a high magnification mode by a CCD camera.

FIG. 6 is a vertical sectional side view showing a part of a conventional probe device.

FIG. 7 is an explanatory view showing an alignment area of a conventional probe device.

[Explanation of symbols]

 2 Wafer Holder 22 Probe Card 25 Probe Needle 31, 41 Ball Screw 32, 42 Motor 33, 43 Encoder 6 Holding Member of Optical System Member 61 CCD Camera 62 Image Processing Unit 7 Arithmetic Processing Unit 71 Storage Unit 72 Motor Control Unit

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H01L 21/66 G12B 5/00

Claims (1)

(57) [Claims] 1. A test object in which a large number of chips to be inspected are arranged vertically and horizontally by an X-axis by a motor to which an encoder is connected.
And a holding table driven along the Y-axis and intermittently moving the holding table to cover the probe needle.
In a probe method for performing electrical measurement of a device under test by sequentially contacting electrode pads of a test chip, the probe needle and the electrode pad may be sequentially contacted.
Move the holding table within the measurement area, which is the range of movement of the test object.
Move along the X-axis to align the chip vertically (horizontally)
Images of multiple specific locations that are separated along
The number of pulses from the encoder and the characteristics
X-axis direction per pulse based on distance between fixed positions
The step of determining the amount of movement of the holding table, and the step of sequentially contacting the probe needle and the electrode pad.
Move the holding table within the measurement area, which is the range of movement of the test object.
Move along the Y-axis to align the horizontal (vertical)
Images of multiple specific locations that are separated along
The number of pulses from the encoder and the characteristics
Y-axis direction per pulse based on distance between fixed positions
Calculating the moving amount of the holding table, and imaging a specific position on the surface of the test object in the measurement area.
And image the tip of the probe needle.
Position of the electrode pad and probe needle based on the imaging result
And performing Align, after alignment in this step, 1 pulse already determined
The amount of movement of the holding table in the X-axis direction per pulse and one pulse
The motor is controlled based on the amount of movement of the holding table in the Y-axis direction
This allows the probe needle to be
A step of making electrical measurement of the test object by sequentially contacting
A probe method, comprising: