JPH11145211A - Velocity controlling method for wafer prober - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a velocity controlling method for a wafer prober which can improve contact reliability between a probe needle tip and a pad, without generating substances which become the major reason for intermittent contact failure during overdrive. SOLUTION: In this velocity controlling method for a wave probe, a probe needle is made to transfer at a high speed immediately prior to making contact with a pad surface on a semiconductor wafer, to proceed at a low speed, when a probe needle is made to overdrive on a pad surface by a constant needle pressure and made to draw back at a low speed after the overdrive operation is finished.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling the operation of a wafer prober used at the time of a wafer test of a semiconductor integrated circuit (IC), and more particularly to a method for controlling the vertical, horizontal and height positions (referred to as alignment). The present invention relates to an improvement in a speed control method at the time of contact (contact) and overdrive (pressurization at a constant pressure after contact).

[0002]

2. Description of the Related Art Generally, a process of manufacturing an integrated circuit (IC), a high-density integrated circuit (LSI) and the like includes a wafer test process for testing whether individual chips on a semiconductor wafer are good or defective. Exists. This wafer test is usually
Attach a probe card to a device called a prober,
This is performed by bringing a probe needle of a probe card into contact with a predetermined pad on a chip of a semiconductor wafer. Specifically, as an electrical connection, after this contact, a certain pressure (referred to as a stylus pressure) between the probe needle and the pad is further applied (referred to as overdrive), and the probe needle removes aluminum oxide or the like on the pad surface. This is accomplished by removing and contacting the underlying aluminum with low contact resistance.

The outline of the probe needle and the probe card is disclosed in Japanese Utility Model Laid-Open No. 57-146340.

FIG. 3 is a flowchart for explaining the outline of the operation of a conventional wafer prober. In the figure, step 1 is a process of mounting a probe card on a wafer prober, and step 2 is a vertical and horizontal direction (XY directions) for the tip of a probe needle of the probe card to accurately contact a corresponding pad of a chip on a semiconductor wafer. Step 3) is a height (Z direction) in preparation for the next operation (Step 4) for the tip of the probe needle of the probe card to accurately contact the corresponding pad of the chip on the wafer. Positioning process, step 4
Is a descending / contact / overdrive process in which the probe needle of the probe card moves by a distance of {(height) + (overdrive amount)} with respect to the pad of the chip. Step 5 shows a test start process after the contact. .
Then, the wafer prober performs the above-described series of operations on a single wafer several times by changing the location and contacting all the chips to determine whether or not the wafer is good.

A CCD camera or the like is used for the positioning and the distance measurement in the above-described steps, and is controlled and operated at high speed with an accuracy of several μm. Then, as described above, after the positional relationship between the probe needle and the pad is grasped by the alignment process of Step 2 and Step 3, the probe needle contacts the pad at a constant speed in Step 4 and is overdriven. Probe scars are generated on the pads, and ultimately electrical continuity is obtained.

FIGS. 4 and 5 are views for explaining the details of the step 4 in the operation of the conventional wafer prober of FIG. 3, and FIG. (XYZ
FIG. 4B shows a state in which the alignment of
FIG. 4 (c) shows a state where the tip 6 of the probe needle contacts the pad 7, that is, pushes through the oxide film (thickness of several tens of angstroms) 8 and enters the pure aluminum pad 7 thereunder. FIG. 5 shows an overdrive operation in which the probe needle tip 6 slides deeply into the pad (thousands of Angstroms) 7 in depth.
(A) shows a probe scar (generally, 10 to 20 μm width × 30 to 40 μm length × 1 μm or less depth) generated on the pad 7 as viewed from above, and FIG. 6 shows a state in which the pad 6 is separated from the pad 7.
In the figure, 6 is the tip of the probe needle, 7 is a cross-sectional view of the pad portion mainly composed of aluminum, 8 is an oxide film (component is α-Al ₂ O ₃ ) on the pad surface, and 9 is the cutting while the probe needle slides. The bottom of the groove (the component of the surface film is alumina Al ₂ O ₃
10) Aluminum oxide (estimated as α-Al ₂ O ₃ ), in which the scraped aluminum protruded from both sides of the groove while sliding the probe needle oxidized and deposited, and 11 adhered to the probe needle tip 6. Aluminum oxide (alumina Al ₂ O ₃ , α-A
l ₂ O ₃ etc.).

[0007]

The movement speed of the probe needle during the contact and overdrive operations of the conventional wafer prober is constant, and is a high speed in consideration of shortening the processing time.

Therefore, the aluminum oxide adhering to the tip of the probe needle is a hard and insulating aluminum oxide called α-Al ₂ O ₃ , which is a major cause of an increase in contact resistance and contact failure.

In the following, during operation of the conventional high speed control of the wafer prober, α-produced only under extremely high heat is used.
The reason why hard and insulating aluminum oxide called Al ₂ O ₃ is present at the tip of the probe needle or at the bank of the probe scar will be described.

In general, the surface of the pad 7 is not perfectly flat but has projections when observed microscopically, even though the surface of the pad 7 is intended to be considerably smooth. Although it appears that the probe needle tip 6 is in contact with the probe needle 6 in a wide area, it actually comes into contact with only some isolated protrusions. When a frictional force due to overdrive is applied to such a contact interface, the force is intensively applied to the protrusion, and the deformation of the protrusion is elastic at first, but causes plastic deformation when further force is applied, Eventually, destruction will begin. At that moment, the temperature of the above portion rises rapidly, so that welding or oxidation occurs at the interface. This occurrence is highly dependent on interface forces and velocities. In this way, the aluminum has the above-mentioned characteristic α-Al
It is considered to be aluminum oxide called ₂ O ₃ .

According to the present invention, α-A is presumed to be a main cause of contact failure during the above-mentioned overdrive.
It is an object of the present invention to provide a method for controlling the speed of a wafer prober which does not generate aluminum oxide called l ₂ O ₃ at an aluminum interface.

[0012]

According to the first aspect of the present invention,
In a speed control method of a wafer prober provided with a probe needle for contacting a pad on a semiconductor wafer, a first step until immediately before the probe needle is brought into contact with a pad surface on the semiconductor wafer, and the probe needle is placed in the pad. The method is characterized in that the speed of the probe needle is controlled in each of the two steps, that is, a second step of overdriving with a constant stylus pressure and a third step of retreating after the overdrive operation is completed.

According to a second aspect of the present invention, in the first descending step, the probe needle approaches the pad surface on the semiconductor wafer at a high speed, and in the second overdrive step, the probe needle advances at a low speed in the pad, In the third step, the speed was controlled so that the probe needle retreated at a low speed in the pad.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 FIG. 1 is a flowchart for explaining an outline of a wafer prober speed control method according to Embodiment 1 of the present invention. In FIG. 1, step 1 is a step of mounting the probe card on the wafer prober, step 2 is a step of positioning (aligning) the tip of the probe needle of the probe card in the vertical and horizontal directions (XY directions), and step 3 is a step of mounting the probe card. Step 5 indicates a test start step after contact, and the operation of the conventional descent, contact, and overdrive of Step 4 will be described in Steps 41, 42, and 43 in Steps 41, 42, and 43. The feature is that it is divided into steps.

That is, step 41 is a step 6
Is a descending operation just before contacting with the surface of the pad 7, and step 42 is an operation of contacting the probe needle with the pad surface 8 thereafter, and penetrating deep into the pad 7 by overdrive at a constant needle pressure. Step 43 is an operation for slightly retracting the probe needle after the overdrive operation.

The differences between the steps 41, 42 and 43 are the relative positional relationship between the semiconductor wafer and the probe needles and the moving speed. Step 41 has a "fast" speed for bringing the probe needle closer to the pad before contact, step 42 has a "slow" speed for slowly approaching overdrive after contact, and step 43. It has a "slow" speed that slowly moves away from overdrive to stop.

First, in step 41, the probe needle is brought close to the pad with the same high moving speed as in the prior art, and the process is speeded up.

Next, in step 42, an overdrive operation after the contact is performed at a speed lower than the conventional speed. That is, even when the probe needle 6 moves in the aluminum of the pad 7 at a low speed and makes contact with only some of the isolated projections, the temperature of that portion does not rise even if force is applied intensively to the projections. So that no welding or oxidation occurs at the interface.

Here, the aluminum oxide formed by the above-mentioned speed control is an aluminum oxide having an oxide film which is very thin naturally formed on the aluminum surface and does not become a main cause of contact failure.

FIG. 2 is a view for explaining aluminum oxide generated by the low-speed overdrive operation of the wafer prober (step 42).
2A shows a probe scar formed on the pad 7 due to the overdrive operation, and FIG. 2B shows a state where the probe needle 6 is separated from the pad 7. In the figure, 91
Is the bottom of the groove cut while the probe needle is slipping, 101
Is the aluminum oxide deposited and oxidized on the both sides of the groove cut by the probe needle sliding, and 111 is the aluminum oxide adhering to the tip of the probe needle. It is an aluminum oxide with an oxide film that does not cause a major problem.

As described above, if the overdrive operation after the contact of the wafer prober is performed at a low speed, hard and insulating aluminum oxide called α-Al ₂ O ₃ , which is the main cause of the contact failure, is removed from the tip of the probe needle or the probe. Since it is not formed on the scar, there is no merit that a contact failure or the like frequently occurs, and further, there is an advantage that the probe needle can be used for a long life.

As a result, the maintenance cost of the probe card can be reduced and the wafer test yield can be improved.

Next, in step 43, after the above-mentioned overdrive, the tip of the probe needle is slightly retracted at a low speed and stopped. This backward movement
This is useful for further improving the contact reliability between the probe needle tip and the pad.

In other words, on the toe side (left side in the figure) at the head of the probe scar shown in FIG. 2A, a bank 101c of aluminum oxide pressed by the probe needle tip 6 during overdrive is deposited. In the final state up to the overdrive operation in steps 41 to 42, the probe needle tip 6 is likely to ride on a part of the aluminum oxide bank 101c, and the contact reliability may be reduced.

In order to separate the probe needle from the leading end of the probe scar in step 43, the overdrive amount is reduced and retreated, for example, the overdrive amount = 1.
The probe needle tip is retracted at a “slow speed” from 00 μm to 70 μm so that the oxidation and melting phenomena do not occur. The probe needle does not ride on the aluminum oxide and reliably contacts pure aluminum to ensure high contact reliability.

In the above embodiment, a tungsten probe needle and a cantilever type probe needle have been described. However, a test is performed using a probe card including other vertical, cobra, L-type probe needles. In this case, the same effect can be obtained by adopting the same wafer prober speed control.

In the above description, the case where aluminum is used as the pad material has been described. However, even if this is changed to another metal such as copper, oxidation and the like are promoted by the generated intense heat, and the same phenomenon occurs. The same effect can be obtained by the same wafer prober speed control of the present invention.

[0028]

According to the speed control method of the wafer prober of the present invention, since the probe needle is advanced at a low speed during overdrive, α-Al ₂ O ₃ , which is presumed to be the main cause of contact failure, can be obtained. The probe needle can be used for a long life without generating so-called aluminum oxide or the like at the interface, without causing contact failure or the like.

Since the probe needle is slightly retracted at a low speed after overdrive, the contact reliability between the probe needle tip and the pad can be further improved.

[Brief description of the drawings]

FIG. 1 is a flowchart illustrating an outline of a wafer prober speed control method according to Embodiment 1 of the present invention;

FIGS. 2A and 2B are diagrams for explaining aluminum oxide generated by a low-speed overdrive 42 of the wafer prober in FIG. 1, wherein FIG. 2A shows a probe scar, and FIG. 2B shows a state where a probe needle is separated from a pad. It is a thing.

FIG. 3 is a flowchart illustrating an outline of an operation of a conventional wafer prober.

4A and 4B are views for explaining the operation of a conventional wafer prober, in which FIG. 4A shows a state in which vertical, horizontal, and height alignments have been completed, and FIG. State (c) is a state of entering the pad.

5A and 5B are views for explaining the operation of a conventional wafer prober, in which FIG. 5A shows a probe scar formed on a pad, and FIG. 5B shows a state where a probe needle is separated from the pad.

[Explanation of symbols]

Step 1 Probe card setting process, Step 2
Vertical / horizontal positioning process, Step 3 Height positioning process, Step 41 Operation immediately before the probe needle tip abuts, Step 42 Overdrive operation to enter deep into the pad, Step 43 Retreat operation after overdrive, Step 5 test Start, 6 Tip of probe needle, bottom of 91 groove, 101 deposited aluminum oxide, 111 aluminum oxide attached to probe tip.

Claims (2)

[Claims] 1. A method for controlling the speed of a wafer prober provided with a probe needle for contacting a pad on a semiconductor wafer, comprising: a first step until immediately before the probe needle contacts a pad surface on the semiconductor wafer; A second step of overdriving the needle to the pad surface with a constant needle pressure;
A speed control method for a wafer prober, wherein the speed control of the probe needle is performed in each of the third steps from the end of the overdrive operation to the retreat. 2. In the first lowering step, the probe needle approaches the pad surface on the semiconductor wafer at a high speed, and in the second overdrive step, the probe needle advances at a low speed in the pad, and 2. The speed control method for a wafer prober according to claim 1, wherein in the step, the speed of the probe needle is controlled so as to retreat at a low speed in the pad.