JPH01227448A - Prober for wafer - Google Patents

Abstract

PURPOSE:To inspect a wafer with high accuracy at proper stylus pressure regardless of the height and deformation of the wafer by installing a height sensor detecting the height of each chip on the wafer held by a wafer chuck and a monitor detecting the positions of respective chip. CONSTITUTION:A height sensor 2 detecting the height of each chip 13 on a wafer 12 held by a wafer chuck 11 and a monitor 4 detecting the positions of separate chip 13 are mounted. The height of all chips 13 in the wafer 12 is detected by the height sensor 2 by passing the wafer 12 sucked to the wafer chuck 11 at the position of the height sensor 2 set up at a predetermined location, and the movement of the wafer chuck 11 is adjusted in response to the result of the detection. The TV monitor 4 by outputs from a microscope and a image pick-up camera 3 brings a probing needle 21 into contact at the position of a probe to electrode pads fitted to the chips 13 in the wafer 12, and is used for confirming the position and size of. the needle trace of the probing needle.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a wafer blobber for performing probe tests on semiconductor wafers, and provides a wafer blobber suitable for measuring semiconductor wafers with high precision.

[Conventional technology]

In the manufacturing process of semiconductor devices, when a wafer chip is completed on a wafer, the electrical characteristics of the wafer chip are tested by bringing a probe needle into contact with an electrode pad, which is called a probe test. In such an inspection, inspection accuracy is largely influenced by whether or not the probe needle is in contact with the electrode pad of the wafer chip with a constant needle pressure at the probe position. Conventionally, the needle pressure when the probe needle contacts the electrode pad of the wafer is affected by the thickness of the wafer and the inclination of the wafer surface, so the amount of movement of the wafer chuck in the Z-axis direction relative to the probe needle is controlled. It was adjusted by

[Problems to be solved by the invention]

However, the present inventors have determined that the factors influencing stylus pressure are:
They discovered that the non-uniformity of the wafer thickness, the tilt of the wafer surface, the amount of deflection of the wafer chuck when subjected to stylus pressure, etc. have a very large influence. With the recent increase in wafer density, as shown in Figure 9,
The probe needle 21 is now installed vertically on the probe card 22. In such a case, an excessive load is applied to the probe needle 21 due to a slight difference in needle pressure, resulting in deformation, and even after the load is removed, the deformation remains, making the probe needle 21 unusable. . SUMMARY OF THE INVENTION An object of the present invention is to provide a wafer blobber that can inspect a wafer with appropriate stylus pressure with high accuracy regardless of the height or deformation of the wafer.

[Means to solve the problem]

That is, the wafer blobber of the present invention is characterized by having a height sensor that detects the height of each chip on the wafer held by the wafer chuck, and a monitor that detects the position of each chip.

【Example】

An embodiment of the present invention will be described below with reference to the drawings. 1 to 4 show an embodiment of the wafer prober of the present invention, FIG. 1 is a schematic plan view thereof, FIG. 2 is a side view thereof,
FIG. 3 is a schematic plan view showing how to use the dummy wafer, and FIG. 4 is a perspective view showing the driving direction of the wafer chuck. Each chip 13 is inspected by relative movement of the wafer 12 and a probe means 1 consisting of a probe card, etc., placed at a probe position. For example, if the wafer 12 is
The inspection is performed by moving in the axis-Y axis direction. In the above-mentioned vertical movement, the wafer 12 attracted to the wafer chuck 11 passes through the height sensor 2 provided at a predetermined position, so that the height of all the chips 13 in the wafer 12 increases. Detected by sensor 2. That is, as shown in FIG. 2, when the edge of the wafer 12 crosses the height sensor 2 vertically and horizontally, the two points X+, Xa and Yl, Y2 are +-Xi Yl-Y.
z Center, □ Extend a perpendicular line from □, and use the intersection as the center O of the wafer 12 from now on. Then, the wafer 12 is moved in a thinly wound or meandering manner starting from the center O, and each chip 13 on the wafer 12 is detected by the height sensor 2 . This detection result is stored in memory. 4 is a TV monitor using the output from the microscope and the imaging camera 3, in order to contact the probe needle 21 at the probe position with the electrode pad provided on the chip 13 of the wafer 12, and to confirm the position and size of the needle mark. used. That is, as shown in FIG. 4, the wafer chuck 11 holding the wafer 12 is driven in the X-axis, Y-axis, Z-axis direction, and θ direction, and the wafer 1 is
It controls the posture of 2. Note that before the height sensor 2 detects the height of each chip 13, the wafer 12 is observed on the TV monitor 4 to determine which position within the chip 13 is to be detected. Thereafter, the wafer 12 is moved to the viewing position of the height sensor 2, the center O of the wafer 12 is determined by the above procedure, and the height of each chip 13 is detected. The obtained height data for each chip 13 is stored in a memory. The wafer 12 is then transferred to a probe position and each chip 13 is electrically measured. At this time, the wafer chuck 11 operates to bring each chip 13 into contact with the probe needle 21 as shown in FIG. 5, but the amount of movement in the Z-axis direction is adjusted depending on the height of each chip 13. This adjustment is performed by controlling the drive system of the wafer chuck 11 in accordance with the height data for each chip 13 stored in the memory. Note that since the inclination of the wafer 12 in the X-axis or Y-axis direction is corrected at the position of the TV monitor 4, there is no need to adjust it at the probe position. In this embodiment, when the wafer 12 to be inspected is transferred to the probe position and each chip 13 on the wafer 12 is electrically measured, the following preparation steps are performed. That is, first, the amount of deflection of each part of the chuck top of the wafer chuck 11 is measured in relation to the needle pressure by the probe needle 21. For measurement, as shown in FIG. 6, a magnet scale 34 is used which is supported by a head plate 33 at the probe position and is movable up and down. That is, the weight 32 is placed on the chuck top 31 of the wafer chuck 11, and in this state, the wafer chuck 11 is raised in the Z-axis direction and brought into contact with the tip of the magnescale 34. Then, the amount of deflection of each portion of the chuck top 31 of the wafer chuck 11 is detected. Generally, the amount of deflection is small at the center of the wafer chuck and large at the periphery due to the relationship with the pillars of the wafer chuck. However, there is considerable variation due to factors such as the material of the wafer chuck 11. The amount of deflection of the chuck top 31 of the wafer chuck 11 measured in this manner is stored in a memory and used to control the drive of the wafer chuck 11 in the Z-axis direction in a later probe process. By reducing deviations in stylus pressure in this manner, wafers can be inspected with even higher precision. At the same time, when the deviation of the stop position of the wafer chuck 11 during movement in the Z-axis direction was detected using the means shown below, it was found that vibrations as shown in A in Fig. 8 were generated depending on the movement speed. There was found. To detect the deviation, as shown in FIG. 7, an oscilloscope 35 supported by a head plate 33 at the probe position is used. That is, a weight 32 is placed on the chuck top 31 of the wafer chuck 11, and in this state, the wafer chuck 11 is raised in two axial directions, and its position is detected with an oscilloscope 35. Then, the amount of vibration of each part of the chuck top 31 is detected. Since the vibration of the wafer chuck 11 measured in this way is greatly influenced by the speed in the Z-axis direction, the inventors of the present invention have conducted various studies and decided to control the drive of the wafer chuck 11 in the Z-axis direction in two steps. I found that it can be resolved by doing this. By reducing the amount of vibration in this manner, the wafer can be inspected with even higher precision. Next, the operation of the wafer blobber of the present invention will be explained. Transfer the dummy wafer 14 to the probe position using normal loading and unloading means. Next, place a mark 15 made of a needle trace with the probe needle 21 at an arbitrary position on the dummy wafer 14.
is attached and sent to the position of the TV monitor 4. Then, the mark 15 on the dummy wafer 14 is confirmed on the TV monitor 4, and the distance between it and the probe position is detected. The obtained data is stored in a memory such as a RAM. Next, the wafer 12 to be inspected is transferred to the probe position, and the probe needle 21 is inserted into the electrode pad provided on the chip 13 of the wafer 12 at the probe position. Make contact. The wafer 12 to be inspected, which has a mark 23 such as a needle trace of the probe needle 21, is checked by the TV monitor 4.
The position and size of the image are confirmed. At the same time, wafer 1
The wafer chuck 11 that has attracted the wafer 2 is driven in the X-axis, Y-axis, Z-axis directions, and θ direction, and the marks 2 such as needle marks are confirmed.
3 controls the attitude of the wafer 12. Thereafter, the wafer 12 is transported to a probe location and each chip 13 undergoes normal testing. In each of the above steps, control is performed in two axial directions according to the amount of deflection of the wafer chuck 11. Also, the 8th
As shown in B of the figure, when driving the wafer chuck 11 in the Z-axis direction, the wafer chuck 11 is operated in two stages, in which the wafer chuck 11 is moved at a high speed for most of the upward movement, and the speed is reduced when the wafer chuck 11 approaches the stop position. In this way, the vibrations mentioned above can be eliminated and tests etc. can be carried out very accurately and without reducing the speed. Note that the height sensor 2 determines the height of any position within the chip 13.
Whether the measurement is to be performed is instructed by aligning the image on the TV monitor 4, which is output from the microscope and the imaging camera 3, with the cross mark 5 located at the center of the TV monitor 4. The point located below the cross mark 5 is X, Y
If it is known how far the point in the chip 13 indicated on the TV monitor 4 can be moved to be directly below the height sensor 2, it becomes possible to accurately move the point in the chip 13 to be below the height sensor 2. This amount of movement can be achieved, for example, by using the following method. First, the wafer chuck 11 crosses vertically and horizontally directly below the height sensor 2 at two points,
Xz and Y, , Y2 (7) center, the center of l is 0,
This is the coordinate at which the wafer chuck 11 moves directly below the height sensor 2. Next, when the wafer chuck 11 crosses vertically and horizontally just below the cross mark 5 on the TV monitor 4, the two centers move below the cross mark 5 on the TV monitor 4. The sensor 2 and the cross mark 5 on the TV monitor 4 This is the distance between the two, that is, the amount of movement. Therefore, each chip 13 is
wafer 12 on this TV monitor 4 before detecting the height of the wafer 12.
The position within the chip 13 to be detected is determined by observing. Thereafter, the wafer 12 is moved to the position of the height sensor 2, the center 0 of the wafer 12 is determined by the above procedure, and the height of each chip 13 is detected. The sizes of the chip 13 in the X and Y directions are entered in advance using a keyboard or the like and stored inside the blower. Therefore, after the specific point indicated on the TV monitor 4 is moved directly below the height sensor 2, the specific point on each chip 13 on the wafer 12 is moved by the pre-stored size of the chip 13. height measurement becomes possible. The obtained height data for each chip 13 is stored in a memory. The wafer 12 is then transported to the probe position and each chip 13 is electrically measured as described above. In addition, in this probe process, the probe position, height sensor 2
The distances Ll and L2 between the wafer 1 and the TV monitor 4 are
The entire probe process can be performed automatically by measuring with reference to the center 0 of 2, etc., and controlling the amount of movement of the wafer chuck 11 according to the data. In the above embodiment, the height of all chips formed on a wafer is detected, and the stylus pressure of each chip is corrected to a predetermined stylus pressure using this detection signal. It may be divided and the stylus force may be adjusted in blocks. The blocks are, for example, divided into five parts including a central part and a peripheral part. Furthermore, the height of only chips or dummy chips at predetermined positions may be detected.

【Effect of the invention】

The wafer prober of the present invention can automatically detect the height of each wafer, and by correcting the relative movement amount between the probe needle and the electrode pad according to this detected value,
Highly accurate measurements are possible because the test can always be performed with a predetermined stylus force.

[Brief explanation of the drawing]

FIG. 1 is a schematic plan view showing one embodiment of the wafer blowbar of the present invention, FIG. 2 is a side view thereof, FIG. 3 is a schematic plan view showing how to use a dummy wafer, and FIG. 4 is a schematic plan view showing the driving direction of the wafer chuck. FIG. 5 is a schematic side view showing the movement of the wafer in two axes in the probe process, FIG. 6 is a schematic side view showing means for detecting the amount of deflection of the wafer chuck, and FIG. 8 is a graph showing the vibration of the wafer chuck when the wafer chuck is stopped; FIG. 9 is a schematic side view showing the deformation of the probe needle in the conventional case; FIG. FIG. 10 is a schematic side view showing the deflection of the wafer chuck when subjected to needle pressure. 1... Probe means 2... Height sensor 3.
...Microscope and imaging camera 4...Monitor
11... Wafer chuck 12... Wafer
13...Chip 14...Dummy wafer
15... Mark 21... Probe needle 22...
・Probe card 23...Mark 31...
・Chuck top 32... Weight 33...
・Head plate 34... Magnescale 35...
・Oscilloscope patent application Tokyo Electron Ltd. Representative Patent Attorney Hiroshi Tsuchihashi [-11
1°＼ 5, Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7

Claims (1)

[Claims] 1. A wafer prober characterized by having a height sensor that detects the height of each chip on a wafer held by a wafer chuck, and a monitor that detects the position of each chip.