JP3902749B2 - A prober and tray for automatic impedance calibration - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a prober for connecting a tester and an electrode of each chip for an electrical test of a chip (die) on a wafer, and more particularly to a prober touching an impedance calibration board (ISS) for measuring high frequency characteristics. The present invention relates to a prober having a function of contacting a needle.
[0002]
[Prior art]
After a large number of semiconductor chips (dies) are formed on the wafer, the electrical characteristics of each chip on the wafer are tested. In order to perform this test, a test signal generated by a power source and a tester is applied to the electrode pad of each chip, and a signal generated at the electrode pad is detected to check whether the chip is operating normally. A device that connects the tester and the electrodes of each chip is a prober.
[0003]
The prober includes a stage for fixing and moving the wafer, a stylus that contacts the electrode pad of the chip, and an alignment unit that detects the arrangement of a plurality of dies and the positional relationship between the electrode and the stylus. After the stylus is brought into contact with the electrode, the stylus and the test head terminal are electrically connected, and a test is performed by detecting a signal output by applying a power source and a signal from the test head. The alignment means includes an alignment camera that detects the die arrangement and electrodes, and a needle alignment camera that detects the positional relationship of the stylus, and calculates the positional relationship. The control unit rotates and moves the stage based on the detected positional relationship to bring the stylus into contact with the electrode pad of each die, and when the test is completed, the stylus is brought into contact with the electrode pad of the next die. The same operation is repeated until the test is completed.
[0004]
Since the prober is widely known, further explanation is omitted here.
[0005]
Each die must perform a predetermined test corresponding to the operating conditions. Some semiconductor chips (dies) formed on a wafer operate at a very high frequency, and the test must be performed under high-frequency operating conditions. In such a case, a tester including a stylus and The impedance of the test wiring path between the electrode pads affects the operation. Therefore, when testing a die that operates at a high frequency, it is necessary to calibrate the impedance of the test wiring path.
[0006]
Therefore, a chip called an impedance calibration substrate (Impedance Standard Substrate: ISS) is prepared, and impedance calibration can be performed by performing a predetermined calibration operation after bringing the stylus into contact with a predetermined portion of the ISS.
[0007]
[Problems to be solved by the invention]
The ISS is in the shape of a chip. When impedance calibration is performed, the ISS is attached to the prober stage, and the operator manually touches the stylus to a predetermined part of the ISS to perform impedance calibration. I was going.
[0008]
However, such an operation is complicated, and there is a problem that the stylus is damaged when an incorrect operation is performed.
[0009]
An object of the present invention is to make it possible to easily perform complicated impedance calibration work.
[0010]
[Means for Solving the Problems]
To achieve the above objectives, just like when testing dies on a regular wafer, using a dedicated tray that has a shape similar to the wafer and can hold the ISS in place Enable impedance calibration.
[0011]
That is, the prober of the present invention is connected to a wafer transfer mechanism for fixing and transferring a wafer on which a plurality of dies are formed, and a terminal of the test head, and contacts the electrode of the die to contact the electrode of the test head The wafer transport mechanism and the alignment means so that the stylus is in contact with the electrode electrodes of each die in sequence, and the alignment means for detecting the positional relationship between the electrodes of the dies and the stylus. And a control means for transferring a tray having a shape similar to that of a wafer on which an impedance calibration substrate (ISS) is placed at a predetermined position, and the control means includes a stylus and an impedance calibration substrate. Function to control the wafer transfer mechanism so that the alignment means is controlled so as to detect the positional relationship of the electrodes, and the stylus contacts the electrodes of the impedance calibration substrate. Characterized in that it has.
[0012]
According to the present invention, since the ISS is fixed in place by a dedicated tray having a shape similar to that of the wafer, the stylus is brought into contact with the electrode of the ISS in the same manner as the electrode of the die on the wafer. Can be made. Therefore, impedance calibration using ISS can be performed automatically in the same way as die testing.
[0013]
The wafer transfer mechanism has a vacuum suction mechanism for fixing the wafer to the stage, but the tray is fixed on the tray by operating the vacuum suction mechanism with the tray placed on the stage. It is desirable that the tray is fixed to the stage.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a diagram showing an overall configuration of a wafer test system according to an embodiment of the present invention, and has the same configuration as a general wafer test system currently used. As shown in the figure, the prober 1 includes a stage 11 for fixing and transferring the wafer 5, a probe card 12 having a stylus 13, a control unit 14 for controlling each part, and a needle for detecting the position of the stylus 13. The alignment camera 15 includes an alignment camera 16 that detects the arrangement of the dies and the positions of the electrode pads of the dies. The performance card of the test head 2 is connected to the probe card 12 by a connection mechanism called a pogo pin biased by a spring. As a result, the terminal of the test head 2 and the stylus 13 are connected. The test head 2 is rotatably held around the rotation shaft 4. The tester 3 is electrically connected to the test head 2, and a test signal generated by the tester 3 is sent to the test head 2, and the test head 2 generates a signal to be applied to the die accordingly. These signals are applied to the electrode pads of the die via the probe card 12 and the stylus 13. A power supply voltage or the like is also applied from the test head 2 to the electrode pad of the die via the probe card 12 and the stylus 13. The signal output to the electrode pad of the die is sent to the test head 2 via the stylus 13 and the probe card 12, and is sent to the tester 3 after some processing and analyzed to check whether a predetermined signal is obtained. Is done.
[0015]
When the die operates at a high frequency, the test head 2 is provided with an RF module 21 that handles a high frequency signal and a DC module 22 that handles a power supply voltage and a low frequency signal. The terminals of the RF module 21 and the DC module 22 are connected to different styluses 13, respectively. Only the signal path to the RF module 21 is subjected to impedance calibration by ISS.
[0016]
The stage 11 is configured to fix the wafer 5 by a vacuum chuck. The stage 11 moves to the upper surface of the prober along the path shown in the figure, and the wafer 5 is transferred (loaded / unloaded) there. Further, there is a tray holder that can be pulled out to the side surface of the prober, and when a tray to be described later is placed on the tray holder, the tray is transported to the upper surface of the stage 11, and conversely, the tray on the upper surface of the stage 11 is transferred to the tray holder. It is supposed to be returned to the top.
[0017]
FIG. 2 is a diagram showing the pattern of the ISS 31 and the shape of the tray 40 on which the impedance calibration board (ISS) 31 is provided. FIG. 3 is a diagram showing the cross-sectional shape of the tray. As shown in the figure, the ISS 31 is in the form of a small rectangular flat plate, and on the surface, target marks 33 provided at four corners, a plurality of alignment marks 34 and 35, and a plurality of patterns 36 for calibration. , 37 are provided. The ISS 31 is fitted in a hole 41 provided at a predetermined position of the tray 40 having a shape similar to a wafer. As shown in FIG. 3A, the tray 40 is an aluminum or ceramic substrate and is provided with a hole 41 into which the ISS 31 is fitted. A hole 45 is further provided below the hole 41. When the tray 40 is placed on the stage 11 and vacuum-sucked, the tray 40 is sucked and fixed to the stage 11 and the hole 45 is decompressed. Therefore, the ISS 31 is fixed to the tray 40.
[0018]
FIG. 3B shows a modification in which an aluminum or ceramic tray 40 and a substrate 43 are bonded and reinforced. A hole is provided at the center of the upper surface of the substrate 43, and when the tray 40 is placed on the substrate 43, a space connected to the hole 45 is formed. This space is connected to the back surface of the substrate 3 through a hole 46 in the substrate 43. When the substrate 43 on which the tray 40 is placed is placed on the stage 11 and is vacuum-sucked, the substrate 43 is sucked and fixed to the stage 11 and the space between the tray 40 and the substrate 43 is decompressed. 40 is fixed to the substrate 43, and the ISS 31 is fixed to the tray 40.
[0019]
With the above configuration, the ISS 31 is fixed at a predetermined position of a tray having a shape approximate to the shape of the wafer, and the position of the ISS 31 can be designated in the same manner as a die on the wafer. .
[0020]
The prober of the embodiment has a function of automatically performing impedance calibration using the ISS 31 and the tray 40 described above. FIG. 4 is a flowchart showing the impedance calibration process.
[0021]
In step 101, the ISS 31 is placed on the tray 40, and the tray 40 is set in the tray holder described in FIG. In step 102, the tray is conveyed from the tray holder onto the stage 11 and vacuum-sucked. At this time, the orientation flat of the tray is detected by a device (not shown) and the orientation of the tray is adjusted. As a result, the position of the ISS 31 on the stage is within a certain error range with respect to the predetermined position. As a result, the ISS 31 can be automatically positioned within the range of the image captured by the alignment camera.
[0022]
In step 103, the stage is moved so that the ISS 31 is positioned below the alignment camera 16. In step 104, the alignment camera 16 recognizes the alignment marks 34 and 35 of the ISS 31. The position of the alignment camera 16 on the image is measured in advance with respect to the stage movement coordinates, and the positions of the alignment marks 34 and 35 of the ISS 31 in the stage movement coordinates are determined.
[0023]
In step 105, the needle alignment camera 15 moves so as to be positioned below the stylus 13, and the stylus 13 is recognized by the needle alignment camera 15. FIG. 5 shows an example of an image captured by the needle alignment camera 15 in that case, where the six styluses 13 are captured in the image 50 and a portion that contacts the tip 61-66 of the stylus 13, that is, the pattern of the ISS 31. Relative position to the image center 51 is recognized. The position on the image of the needle alignment camera 15 is measured in advance with respect to the moving coordinates of the stage, and the position of the tip 61-66 of the stylus 13 in the moving coordinates is determined.
[0024]
In step 106, the movement amount for bringing the stylus 13 into contact with the desired pattern of the ISS 31 is calculated from the recognized positions of the alignment marks 34 and 35 of the ISS 31 and the positions of the tips 61 to 66 of the stylus 13. Note that the rotation amount of the stage necessary to match the direction of the ISS 31 pattern and the direction of the arrangement of the stylus 13 is also calculated. The desired pattern to be contacted is instructed from the tester 3 to the control unit 14 through the GP-IB interface. In step 107, the stage 11 is moved and rotated based on the movement amount and the rotation amount calculated in step 106, and the stylus 13 is brought into contact with a desired pattern of the ISS 31. In step 108, the control unit 14 notifies the tester 3 that the contact of the stylus 13 has been completed, and a signal is output from the tester 3 through the test head 2 to perform calibration for impedance calibration.
[0025]
In step 109, it is determined whether all calibrations are completed. If not completed, the process returns to step 106 and the above processing is repeated. When all the calibrations are completed, the stage is moved to the tray delivery position in step 110, the tray is moved to the tray holder, the tray is collected, and the process is terminated.
[0026]
The arrangement of the stylus 13 is determined corresponding to the electrode of the die. The ISS 31 is used for general purposes, and the arrangement of the stylus 13 does not always match the pattern arrangement of the ISS 31. FIG. 6 is a diagram for explaining a calibration method in such a case. First. As shown in FIG. 6A, the left three styluses 67 of the six are brought into contact with the pattern 37 on the ISS 31. Then, calibration is performed on the three left styluses. Next, as shown in FIG. 6B, the right three styluses 68 are brought into contact with the pattern 38 on the ISS 31 and the right three styluses are calibrated. The above operation is automatically performed by calculating the amount of movement based on the positions of the patterns 37 and 38 from the alignment marks 34 and 35 and the positions of the left and right styluses.
[0027]
When both the left and right styluses 67 and 68 are simultaneously brought into contact with the pattern 39 on the ISS 31, it is performed as shown in FIG.
[0028]
Although the embodiments of the present invention have been described above, various modifications are possible. For example, in the above-described embodiments, an example is described in which all are performed automatically. However, a part of the operations can be performed manually by an operator. For example, when the stylus is brought into contact with the pattern on the ISS, the relative position from the alignment marks 34 and 35 is designated from the tester 3 via the GP-IB interface. However, in the ISS display image captured by the alignment camera 16, the relative position from the alignment marks 34 and 35 is indicated using a joystick or the like, and the control unit 14 is instructed by the positions of the alignment marks 34 and 35. Alternatively, control may be performed so as to contact a position obtained by adding the relative position.
[0029]
Further, even if control is performed based on the positional relationship recognized by the alignment camera and the needle alignment camera, a slight contact position error may occur. Therefore, it is also possible to correct the contact mark of the stylus by visually determining on the image by moving the ISS under the alignment camera after the stylus is once brought into contact with the ISS based on the calculated value.
[0030]
【The invention's effect】
As described above, according to the present invention, complicated impedance calibration work can be easily performed.
[Brief description of the drawings]
FIG. 1 is a diagram showing an overall configuration of a wafer test system according to an embodiment of the present invention.
FIG. 2 is a diagram showing the shape of a tray 40 on which an ISS 31 pattern and an impedance calibration board (ISS) are provided.
FIG. 3 is a diagram showing a cross-sectional shape of a tray.
FIG. 4 is a flowchart showing an impedance calibration operation in the embodiment.
FIG. 5 is a diagram illustrating an example of an image of a needle alignment camera.
FIG. 6 is a diagram for explaining a contact state in a case where the arrangement of the stylus does not coincide with the arrangement of the ISS pattern.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Prober 2 ... Test head 3 ... Tester 5 ... Wafer 11 ... Stage 13 ... Stylus 31 ... Impedance calibration board (ISS)
40 ... Tray

Claims (3)

A wafer transfer mechanism for fixing and transferring a wafer on which a plurality of dies are formed;
A stylus connected to a terminal of the test head and contacting the electrode of the die to connect the terminal of the test head and the electrode of the die;
Alignment means for detecting a positional relationship between the electrodes of the plurality of dies and the stylus;
A prober comprising the wafer transfer mechanism and a control means for controlling the alignment means so that the stylus contacts the electrodes of each die sequentially,
The wafer transfer mechanism transfers a tray having a shape similar to the wafer on which an impedance calibration substrate (ISS) is placed at a predetermined position,
The control unit controls the alignment unit to detect a positional relationship between the stylus and the electrode of the impedance calibration substrate, and controls the wafer transfer mechanism so that the stylus contacts the electrode of the impedance calibration substrate. A prober characterized by having a control function. The wafer transfer mechanism has a vacuum suction mechanism for fixing the wafer to a stage,
The prober according to claim 1, wherein the impedance calibration substrate is fixed to the tray and the tray is fixed to the stage by operating the vacuum suction mechanism in a state where the tray is placed on the stage. An impedance calibration board carrying tray for holding and carrying an impedance calibration board (ISS) used for calibration of measuring instruments such as testers and analyzers,
The tray
It has a shape similar to a wafer,
A hole for fitting the impedance calibration board in a predetermined position;
Under the hole, having a vacuum path connected to the back surface of the tray,
Impedance calibration substrate transport, wherein the impedance calibration substrate is fixed to the tray by vacuum-sucking the back surface of the tray with the tray placed on the stage, and the tray is fixed to the stage. tray.

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