Wafer holder, heater unit having the wafer holder, and wafer prober having the heater unit

Abstract

A wafer holder hardly deformable under high load and capable of effectively preventing a contact failure with a wafer and further capable of preventing temperature increase of a driving system of a wafer prober is provided. In a wafer holder having a chuck top and a supporter, variation in thickness of the chuck top from a wafer-mounting surface to a contact surface with the supporter, and variation in thickness of the supporter from a bottom surface to a contact surface with the chuck top are both set to at most 50 μm. When the supporter is of a structure having a circular tube portion and a base portion separate from each other, variation in thickness of the circular tube portion from a contact surface with the chuck top to a contact surface with the base portion, and variation in thickness of the base portion from a bottom surface to a contact surface with the circular tube portion are preferably both set to at most 25 μm.

Description

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to a wafer holder used for a wafer prober for inspecting electric characteristics of a semiconductor wafer by mounting and fixing the wafer on a wafer-mounting surface and pressing a probe card on the wafer, as well as to a heater unit including the wafer holder and a wafer prober including the heater unit. [0003] 2. Description of the Background Art [0004] Conventionally, in a process for inspecting a semiconductor wafer, a semiconductor wafer (wafer) as an object of processing has been subjected to heat treatment (that is, burn-in). Specifically, by heating the wafer to a temperature higher than the normal temperature of use, degradation of a possibly defective semiconductor chip is accelerated and the defective chip is removed, in order to prevent defects after shipment. In the burn-in process, after semiconductor circuits are formed on the semiconductor wafer and before the wafer is...

AI Technical Summary

Benefits of technology

[0015] In view of the situations of the conventional art as described above, an object of the present invention is to provide a wafer holder capable of effectively preventing contact failure with a wafer, with deformation of a chuck top being small even under high load. A further object is to provide a wafer holder capable of preventing temperature increase in a driving system of the wafer holder, when a semiconductor wafer having minute circuitry requiring particularly high accuracy is mounted on a chuck top and heated. A still further object is to provide a heater unit including the wafer holder described above and a wafer prober including the heater unit.

[0035] According to the present invention, in a wafer holder having a chuck top mounting and fixing a wafer and a supporter supporting the chuck top, variation in thickness of the chuck top from the wafer-mounting surface to the contact surface with the supporter, and variation in thickness of the supporter from the bottom surface to the contact surface with the chuck top are both set to at most 50 μm, and therefore, when electric characteristics of a wafer are measured in the burn-in process, the chuck top deformation is small even when high load is applied, and contact failure with the wafer can effectively be prevented. Further, at the measurement of a semiconductor wafer having minute circuitry that requires particularly high accuracy, temperature increase in the driving system of the wafer holder is prevented when the wafer is mounted on the chuck top and heated, and therefore, positional accuracy between the wafer and the probe card can be improved.

[0036] Further, in the present invention, when the ratio of the maximum diameter to the maximum thickness of the chuck top is set to at least 5 and at most 100, deformation (deflection) of the chuck top can be reduced, and therefore, a wafer prober capable of accurately measuring electric characteristics of the wafer without damaging the wafer can be provided.

[0037] In the present invention, when the supporter is formed of a circular tube portion in contact with the chuck top and a base portion supporting the circular tube portion, the thickness of the circular tube portion is at least 0.1 and at most 5.0 with the thickness of the chuck top being 1.0, and the thickness of the base portion is at least 0.5 and at most 10.0 with the thickness of the chuck top being 1.0, a wafer holder having high rigidity and superior heat insulating effect can be provided. In this case, the chuck top deformation is small even when a high load is applied, and contact failure with the wafer can effectively be prevented. Further, at the measurement of a semiconductor wafer having minute circuitry that requires particularly high accuracy, temperature increase in the driving system of the wafer holder is prevented when the wafer is mounted on the chuck top and heated, and therefore, positional accuracy between the wafer and the probe card can be improved.

Problems solved by technology

As described above, the wafer mounted on the chuck top is pressed to the probe card with a strong force of several tens to several hundreds kgf, and therefore, when the heater is thin, the heater would possibly be deformed, resulting in contact failure between the wafer and the ground electrode.

As a result, it takes long time to increase and decrease the temperature of the heater contained in the chuck top, which is a significant drawback in improving the throughput.

As recent chips come to have higher outputs, it is possible that a chip generates considerable heat during measurement of electric characteristics, and in some situations, the chip might be broken by self-heating.

There is a problem, however, that when the wafer is heated to a prescribed temperature, that is, to about 100 to 200° C., the heat is transferred to the driving system, and metal components forming the driving system thermally expand, degrading positional accuracy.

This is a cause of a contact failure made more likely during an inspection of a semiconductor chip having a particularly minute circuitry.

Further, along with the increase in load at the time of probing, rigidity of the prober itself mounting the wafer has come to be required.

Specifically, when the wafer prober itself deforms because of the load at the time of probing, uniform contact of the pins of probe card with the wafer would fail and inspection becomes impossible, or in the worst case, the wafer would be broken.

In order to suppress deformation of the prober, the prober has been made larger and its weight has been increased, posing a problem that the increased weight adversely influences the accuracy of the driving system.

Further, as the prober is made larger, the time for heating and cooling the prober becomes extremely long, posing another problem of lower throughput.

The former approach has a problem that cooling rate is slow, as it is air-cooling.

The latter approach also has a problem that, as the cooling plate is metal and the pressure of the probe card directly acts on the cooling plate at the time of probing, it is susceptible to deformation.

Further, in the prober, stress generated at the time of probing results in a load on the chuck top, causing deformation.

When the deformation involves large deflection, state of contact between the large number of probe pins attached to the probe card and the wafer may vary and errors may possibly occur at the time of measurement, posing a problem that accurate evaluation becomes impossible.

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