JPS61206238A - Automatic semiconductor wafer prober - Google Patents

Abstract

PURPOSE:To contrive to automize the setting of the probe pressure using an automatic semiconductor wafer prober in a simple constitution by a method wherein switching means are provided between a prober and a tester, a chuck top, which is formed of a conductive metal fixes through suction a semiconductor wafer to be measured is set up, voltage is fed to the chuck top and the existence and non-existence of current to run through the chuck top is detected by a current detecting circuit. CONSTITUTION:The other end of each probe of a probe board DC is connected to a tester TST through the wiring of the printed substrate and a wiring L. A chuck top CT and the probes are selectively connected to the tester TST or the next current detecting circuit by switches SW1 and SW2 and the current detecting circuit detects electrically the contact of the chuck top CT and the tips of the probes. Voltage V is fed to the chuck top CT through the contact point (b) of the switch SW2 and the earth potential of the current detecting circuit is fed to the probes through the contact point (b) of the switch SW1 and a resistor R. According to the existence and the non-existence of the contact of the chuck top CT and the tips of the probes, high-level voltage like the voltage V or low-level voltage like the earth potential of the detecting circuit is obtained in the resistor R and these voltages are discriminated by a voltage comparison circuit VC.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to an automatic semiconductor wafer prober, and, for example, to a technique that is effective when used in a fully automatic semiconductor wafer prober.

[Background technology]

In semiconductor wafer probers, which are responsible for the final checking process of semiconductor wafers, as the diameter of semiconductor wafers becomes larger, manual work using Vincent or other tools becomes difficult, so there is a shift to so-called vinsetless probers, in other words, Automatic loading and unloading of semiconductor wafers was published in "Electronic Materials" magazine, November 1978 issue, pages 139-14.
3. That is, a plurality of sheets (for example, 25
One by one, a round belt conveyor transports semiconductor wafers one by one from a storage container (cassette) containing semiconductor wafers to the loading position (
Transfer to course alignment stage). This semiconductor wafer is then placed on the suction table (chuck top) of a blobbing machine using a Bernoulli chuck or the like.
Next, the semiconductor wafer that has been measured is transported from the suction table to the unloading position by blowing air pressure, etc., and placed in a storage container by a round belt conveyor. Semiconductor wafers are loaded into and unloaded from the blobbing machine without contact.

By the way, for fixed probe boards, the distance between the bottom surface of the printed circuit board (reference surface) and the tip of the probe needle is 2500±50μ.
It is formed with a high precision of m. However, when testing the above semiconductor wafer, the semiconductor wafer is further pushed up (Z-up) by about 70 IIm from the state where the tip of the probe needle is in contact with the surface by the Z stage, so that the error range ± Not only can 50μm not be ignored,
The position of the tip of the probe needle in the Z-axis direction fluctuates due to residual strain in the probe needle due to repeated pressure bonding.

Therefore, in order to obtain the desired electrical connection and to set the needle pressure at a level that does not penetrate the bonding pad formed by the thin aluminum layer, when testing semiconductor wafers, the tip of the probe needle is placed on the surface of the semiconductor wafer. It is necessary to accurately detect that contact has occurred. Edge sensors are used for such position detection. This edge sensor consists of a pair of probe needles, one of which is aligned on the scribe line of the semiconductor wafer, and the other is placed in contact with the underside of the one probe needle. When the tip of one of the probe needles comes into contact with the surface of the semiconductor wafer, contact with the other probe needle is broken. In a fixed probe equipped with such an edge sensor, after detecting the open state of the edge sensor, the two stages are controlled by the amount of penetration of the probe needle. However, the error is large due to variations and fluctuations in the tip position with respect to other probes, and the scribe line width has become extremely fine due to the advancement of semiconductor technology, so fixed probe boards without the edge sensor are The number is increasing. For such fixed probe boards, a method is used to determine the Z-up amount of the semiconductor wafer by examining the contact state between the tip of the probe needle and the surface of the semiconductor wafer using a microscope before testing the semiconductor wafer. be. That is, a probe needle is pressed against a bonding pad, and the scratches generated on the surface of the pad are judged while viewing them under a microscope. For this reason,
Not only is the efficiency inefficient, but there are also individual differences in the determination, resulting in problems such as the inability to obtain accurate stylus pressure.
(See Publication No. 529).

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide an automatic semiconductor wafer prober that has a simple configuration and can automate the setting of probe needle pressure.

The above and other objects and novel features of this invention include:
It will become clear from the description of this specification and the accompanying drawings.

[Summary of the invention]

A brief overview of typical inventions disclosed in this application is as follows.

That is, a switch means is provided between the prober and the tester to raise the chuck top made of conductive metal that suction-fixes the semiconductor wafer to be measured, and
The Z position of the tip of the probe is determined by 4 m by selectively connecting a detection circuit that supplies a voltage between the tip and the probe or between a pair of probes and detects the presence or absence of current flowing there. be.

〔Example〕

FIG. 1 shows an external view of an embodiment of a fully automatic semiconductor wafer prober to which the present invention is applied.

The fully automatic semiconductor wafer prober shown in the figure can be roughly divided into a blowing machine section and a semiconductor wafer transfer section. The semiconductor wafer transfer section includes cassettes CAL and CA that store a plurality of semiconductor wafers in a multi-stage configuration in the vertical direction.
2, and a round belt conveyor BC for transferring the semiconductor wafers between the elevator mechanism and the loading stage and unloading stage for the blowing machine section.

This round belt conveyor BC consists of a combination of a plurality of round belt conveyors, and each round belt comparer is provided with a driving pulley and a free pulley at both ends, and the driving pulley is connected to a similar round belt. A conveyor consisting of a pair of round belts is driven by a motor through the belt, and the semiconductor wafers placed thereon are transported. Guides are provided on both sides of these pair of round belts. This prevents the semiconductor wafer from falling off the pair of round belts. Further, a sensor is provided at the transfer point (connection point) of the semiconductor wafer between each round belt conveyor. Although not particularly limited, this sensor is configured with an optical sensor and detects a semiconductor wafer that has been transferred to the upper part of the sensor. Detected by a sensor provided. In response to this detection signal, the transfer operation of the round belt conveyor is stopped, and the round belt conveyor on the receiving side starts its operation. This allows the semiconductor wafer to be transferred in a vertical direction. The above-mentioned elevator mechanism is, for example, JP-A-54
Since it is publicly known from Publication No. -48482, etc., detailed explanation thereof will be omitted.

The load stage is provided with means for rotating the semiconductor wafer transferred thereto and detecting its orientation flat, and performs a preliminary operation of positioning the semiconductor wafer in the θ direction. Thereafter, the semiconductor wafer is carried onto the surface of the chuck top by a transfer arm configured using a Bernoulli chuck that attracts the semiconductor wafer below the surface without contact.

On the other hand, although the blobbing machine part is not visible from the outside,
It is composed of an X-Y table X-YTB. This X-
A chuck top (suction table) is attached to the Y table X-YTB, which is driven by a pulse motor to perform highly accurate position control. The chuck top is provided with a suction hole for vacuum suctioning the semiconductor wafer and a blowing hole (which may also be used in common with the suction hole) for transporting the semiconductor wafer after measurement to the unloading stage. There is. Also, the chimbutotsubu mentioned above is Z
The stage pushes up the semiconductor wafer against the probe needles of the fixed probe board PC attached to the opening at the top of the X-Y table Make electrical contact.

The microscope MS is used to confirm the alignment (needle alignment) between the contact end of the probe needle and the surface of the semiconductor wafer through the above-mentioned aperture, or to confirm the alignment (needle alignment) between the contact end of the probe needle and the surface of the semiconductor wafer, or as a preliminary inspection in case of failure of automatic alignment as described later. It is used for checking manual needle alignment.

Note that the semiconductor wafer whose orientation flat has been detected on the load stage is moved to the load position by the transfer arm and carried into the chuck top as described above. Above this load position, in order to realize automatic needle alignment,
An imaging device ITV configured with a television camera or the like is provided. The digitized circuit pattern signal of the semiconductor wafer formed by this imaging device ITV is subjected to pattern recognition by an image processing device (not shown).
Identification of the location of the pounding pad is performed. Although not particularly limited, alignment is performed by rotating the semiconductor wafer in the θ direction at the load position, that is, aligning the X-axis of the chip arrangement on the semiconductor wafer with the x-y table X-Y.
``1'' Align the BOX axis.Also, the positioning of the bonding pad is performed.Based on this position detection data, the semiconductor integrated circuit (nap) that first measures the chuck top is placed on the fixed probe board PC. The position of the bonding pad when it is moved to the position of the probe needle above is calculated and automatic needle alignment is performed.As a result, the bonding pad of the first wafer chip to be measured and the probe needle are aligned. Automatic alignment with the tip is performed.Then, by successively moving one chip at a time in the X or Y direction, the probe is automatically aligned with the other wafer tip's pounding pads. The movement of these X-Y tables X-YTB is controlled with high precision using a pulse motor.The wafer chuck top CT is moved in the Z direction (up) using an air or pulse motor.

down). That is, the positioning operation using the X-Y table X-YTB is performed with the wafer chuck top CT in a lowered state, and during measurement, the wafer chuck top CT is pushed up and the probe needle and the wafer chip's bonding pad are connected. Electrical connection is obtained by making contact with the required contact pressure. Since such a stage mechanism is well known, a more detailed explanation will be omitted.A capacitor sensor C8 is provided near the load body for measuring the thickness of the semiconductor wafer. This capacitor sensor measures the stray capacitance with the surface of a semiconductor wafer, and uses the results to measure the thickness.

This thickness measurement result is obtained as the position (up amount) of the Z stage with respect to the reference plane that constitutes one electrode of the capacitor. The thickness is measured at the locations where the semiconductor wafer is divided into a plurality of blocks and each block is measured. The thickness of a semiconductor wafer has variations that cannot be ignored considering the amount of penetration of the probe needle (approximately 70 μm) as described above. The above measurement results are used to correct the amount of penetration of the probe needle into the electrode of the semiconductor chip formed in each block.

The display device CRT mainly displays its monitor screen.

The operation panel PNL is used to input various manual control signals such as starting and stopping the above operations.

In the fully automatic semiconductor wafer prober having the above configuration, in order to automate the setting of the needle pressure of the probe needle, the following probe tip detection means is provided.

FIG. 2 shows a circuit diagram showing one embodiment of the probe tip position detecting means. Chuck top CT is
It is made of conductive metal and has wiring for applying a desired potential to the substrate of the semiconductor wafer from the tester TST side. In addition, the other end of each probe needle of the probe board PC is connected to the terminal TST via the wiring of the printed circuit board and the wiring L4.
connected to. Switch SW to connect these wires
1, SW2 is provided. These switches SW1, S
W2 selectively connects the chuck top CT and probe needle to the tester TST or the next current detection circuit. The current detection circuit electrically detects the contact between the chuck top CT and the tip of the probe, and voltage V is applied to the chuck top CT through the contact of the switch SW2, and the probe needle is applied with the switch SW1. The ground potential of the circuit is applied through the resistor R through the contact point S.

As a result, the tip of the probe and the chuck top CT
When contact occurs, a current of V/R flows if the contact resistance is ignored. Depending on the presence or absence of this current, in other words, the presence or absence of the above-mentioned contact, a high level like the voltage V or a low level like the ground potential of the circuit can be obtained in the resistor R. These binary voltages are determined by a voltage comparison circuit VC. A reference voltage of V/2 is supplied to the non-inverting input (+) of this voltage comparison circuit VC, and the above-mentioned resistor R is supplied to the inverting input (-).
A voltage formed by the voltage is supplied. As a result, when the tip of the probe and the chuck top are not in contact, a high level (H) output signal is obtained from the voltage comparator circuit VC. On the other hand, when the tip of the probe and the chuck top come into contact, a low level (L) output signal is obtained from the voltage comparison circuit VC.

The stylus force setting operation of this embodiment will be explained next.

In other words, prior to measuring a semiconductor wafer, a fixed probe board P corresponding to the semiconductor wafer to be measured is
With C loaded and no semiconductor wafer placed on the chuck top CT, move the chuck top CT to the position of the fixed probe board PC, and move it up one step at a time from the reference point (Z-axis zero point). let At this time, the switches SWI and SW2 are connected to the contact side. This up operation is continued if the output of the voltage ratio soft circuit VC is at a high level.

Then, the operation is stopped when the output of the voltage detection circuit VC changes to low level, in other words, when the tip of the probe contacts the chuck top CT. The positions of the two axes at this time (for example, Zl) are held in a predetermined memory circuit.

Next, the chuck top CT is moved to a load position, and a semiconductor wafer is loaded by the automatic semiconductor wafer transfer means. After preliminary operations of automatic alignment and needle alignment are performed by pattern recognition, the thickness is measured by the capacitor sensor C3, and this result is defined as, for example, z2. By subtracting the thickness z2 from Z2 held in the memory circuit, it is possible to know the Z-up amount at which the surface of the semiconductor chip and the tip of the probe start contact for each block. Thereby, in order to obtain the desired contact pressure (the amount of penetration of the probe needle), the Z-up amount is determined to be approximately 70 μm, for example, as described above.

〔effect〕

(1) By detecting the two-stage position where an electrical connection can be made between the probe tip and the surface of the chuck top, and then subtracting the thickness of the semiconductor wafer, the probe tip and the surface of the semiconductor wafer are The Z-up amount to start contact can be indirectly known. As a result, it is possible to accurately set the amount of probe needle penetration in order to obtain a desired needle pressure.

(2) Since the probe stylus pressure can be automatically set using (1) above, it is possible to save time, and it is also possible to set the stylus pressure with higher precision than when setting the stylus pressure visually. Since it is possible to prevent damage to the semiconductor chip due to poor contact due to insufficient stylus pressure or excessive stylus pressure, it is possible to obtain the effect that high reliability in semiconductor chip testing can be obtained.

(3) The above (1) provides the effect that a fully automated semiconductor wafer prober can be obtained by combining the automatic transfer of the semiconductor wafer and the needle alignment based on pattern recognition of the semiconductor wafer.

(4) By dividing the semiconductor wafer into multiple blocks and measuring the thickness at each location, and setting the stylus force according to (1) above for each block, it is possible to set the stylus force with higher accuracy. You can get the effect that you can.

Although the invention made by the present inventor has been specifically explained above based on examples, it goes without saying that this invention is not limited to the above-mentioned examples, and can be modified in various ways without advancing the gist of the invention. Nor. For example, the presence or absence of contact between a plurality of representative probe needles and the chuck top may be determined in the same manner as described above, and the average value of each Z position may be calculated. The circuit that detects whether or not two probes are in contact with the chuck top may be determined based on whether or not a current flows between a pair of probes. It is something that can take any form.

In addition, the thickness of a semiconductor wafer may be measured by an optical means other than a capacitor sensor.There is no need to mount this thickness measuring device on a semiconductor wafer prober, and for example, it is not necessary to mount this thickness measuring device on a semiconductor wafer prober. The thickness measured in step 1 may be preset in a semiconductor wafer prober as data.

Furthermore, the alignment of the probe to the semiconductor wafer is
The measurement may be carried out manually by visual inspection using a microscope; that is, the measurement is first carried out by visual inspection after the semiconductor wafers are automatically sent sequentially from the transfer section and placed on the wafer chuck top. It may also be a device that aligns the contact end of the bonding pad of the semiconductor integrated circuit and the probe needle (needle alignment).Furthermore, the means for transporting the semiconductor wafer may be an air bearing, etc., in addition to the nine-belt conveyor described above. However, it is desirable that the operation control of the above-mentioned blowing machine section and the operation control of semiconductor wafer transfer be performed by program control using a microcomputer, etc. in order to increase the versatility of the system. The present invention is not limited to this, and may be performed using a so-called hard logic circuit.

[Application field]

This invention can be widely used in automatic semiconductor wafer probers.

[Brief explanation of the drawing]

FIG. F is an external view of the automatic semiconductor wafer prober according to the present invention, and FIG. 2 is a circuit diagram showing an embodiment of the probe tip position detection means. X-YTB...x-y table, MS...microscope, CR
T...display device, ITV...imaging device, CAL
, CA2...cassette, PNL...operation panel, CT...
・Chuck top, C3... Capacitor sensor, PC
・・Probe board, SWl, SW2・・Switch, V
C...Voltage comparison circuit

Claims (1)

[Claims] 1. A switch means is provided between the prober and the tester,
The chuck top, which is made of conductive metal and which holds the semiconductor wafer to be measured under suction, is moved up in the Z direction, and a voltage is supplied between the chuck top and the probe or between a pair of probes to check whether or not there is a current flowing there. An automatic semiconductor wafer prober characterized in that it has a function of connecting a detection circuit to identify the Z position of the probe. 2. The automatic semiconductor wafer prober is equipped with an automatic loading/unloading function for the semiconductor wafer to be measured and a thickness measurement function for measuring the thickness of the semiconductor wafer to be measured that is suctioned and fixed onto the chuck top. An automatic semiconductor wafer prober according to claim 1.