JP2002299397A - System and method for evaluating semiconductor wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a system and method for evaluating the state of a semiconductor wafer with high reliability regardless of the environmental variation. SOLUTION: The system for evaluating the state of a semiconductor wafer comprises a means for removing a surface oxide film from a specified region of the semiconductor wafer, and a means for measuring the capacitance by applying a DC bias voltage to the specified region from which the surface oxide film is removed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for evaluating a semiconductor wafer, and more particularly to a method for measuring a capacitance-voltage characteristic of a semiconductor wafer.

[0002]

2. Description of the Related Art In the process of manufacturing a semiconductor device, in recent years, in particular, as the pattern becomes finer, it is required to more strictly control the concentration and distribution of impurities implanted into a wafer.

For this purpose, it is necessary to accurately evaluate the state of the wafer. Until now, the evaluation has been performed by measuring the capacitance-voltage using an evaluation apparatus as shown in FIG. That is, first, the semiconductor wafer 1 is placed on the stage 2. A capacitance measuring probe 4 is arranged on the wafer 1, and the height and position are controlled by a measuring position adjusting motor 3. After the distance between the wafer and the probe is set to a predetermined value by the distance measuring sensors 5 and 6 and the adjusting motor 7, a DC bias voltage is applied to both ends of the capacitance measuring probe 4 and the capacitance is measured at the same time. The capacity-
Voltage characteristics, that is, a CV curve can be obtained. By analyzing the CV curve, the impurity concentration, the profile in the depth direction, the lifetime, the damage due to ion implantation, and the like can be obtained.

However, in such a conventional semiconductor wafer evaluation apparatus, the characteristics are required assuming that the equivalent circuit shown in FIG. 5 is established. C oxide changes depending on the thickness of the natural oxide film, and the total capacitance C obtained as a measured value changes. For example, when determining the n-type or p-type impurity concentration of the epitaxial layer, the temperature and environment of the semiconductor wafer taken out of the epitaxial growth furnace change, the thickness of the natural oxide film changes, and the C oxide also changes. C oxide
There is a problem that an equivalent circuit with a fixed value is not established, and the impurity concentration cannot be obtained accurately.

[0005]

As described above, in the prior art, since the measurement value changes depending on the environment even in the same sample, the accuracy of the capacitance-voltage measurement is reduced, and the evaluation of the wafer state such as the impurity concentration distribution is performed. There was a problem that can not be accurately.

Accordingly, the present invention eliminates the drawbacks of the conventional semiconductor wafer evaluation apparatus and the conventional evaluation method, and makes it possible to evaluate a semiconductor wafer with high reliability regardless of environmental changes. It is an object of the present invention to provide an apparatus and an evaluation method.

[0007]

According to the present invention, there is provided an apparatus for evaluating a semiconductor wafer, comprising: means for removing a surface oxide film in a predetermined area of the semiconductor wafer; and a DC bias voltage applied to the predetermined area from which the surface oxide film has been removed. And a capacitance measuring probe for measuring the capacitance.

In the apparatus for evaluating a semiconductor wafer according to the present invention, the means for removing the surface oxide film includes a means for supplying a chemical solution to a predetermined region of the semiconductor wafer and etching the surface oxide film with the chemical solution, Discharging means.

Further, in the method for evaluating a semiconductor wafer according to the present invention, after removing a surface oxide film in a predetermined region of the semiconductor wafer, the method may further include:
Apply a DC bias voltage with the capacitance measurement probe,
It is characterized in that its capacity is measured.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below.
This will be described with reference to FIGS.

As shown in FIG. 1, a stage 2 for mounting a semiconductor wafer 1 to be measured is provided in a measurement chamber. The height and position of the stage 2 can be controlled by a measuring position adjusting motor 3. Semiconductor wafer 1
A capacitance measuring probe 4 is arranged so as to face the surface,
The capacitance measuring probe 4 includes distance measuring sensors 5 and 6 for measuring the distance between the semiconductor wafer 1 and the capacitance measuring probe 4 together with the electrodes, a distance adjusting motor 7 for adjusting the distance, and the semiconductor wafer 1. A supply port 9 for supplying a chemical 8 for removing an oxide film on the surface and an outlet 10 for discharging the chemical after removing the oxide film are provided.

In such an apparatus, first, a measurement chamber in which dust is controlled is set to a nitrogen atmosphere, and nitrogen is supplied at a replacement rate of several liters / minute. Then, the silicon wafer 1 on which the surface oxide film 11 is formed is placed on the stage 2, and the position is adjusted by the measuring position adjusting motor 3. Then, the distance between the wafer 1 and the capacity measuring probe 4 is measured by the distance measuring sensors 5 and 6, the distance is adjusted to a predetermined value by the distance adjusting motor 7, and the chemical solution 8 (for example, HF 20 wt.
% Solution), the surface oxide film 11 in the region of 5 mmφ is etched, removed using the surface tension of silicon, and the waste liquid is discharged by suction through the discharge port 10. Then, a DC bias voltage is applied from an electrode in the capacitance measurement probe 4 provided above the region 12 from which the oxide film has been removed, and the capacitance is measured.

From the capacitance measured in this way, it is possible to obtain an accurate capacitance-voltage characteristic, that is, a CV curve, of only a sample that does not contain an oxide film and fluctuates due to the environment. By analyzing this C-V curve, the impurity concentration profile in the depth direction, lifetime,
The state of the semiconductor wafer, such as damage due to ion implantation, can be accurately evaluated.

In this embodiment, a 20 wt% HF solution is used as the chemical solution 8 for removing the oxide film. However, the present invention is not limited to this. For example, a 0.5 to 50 wt% HF solution,
A 50 wt% NH4F solution or the like can be used. Also,
The material is not limited to a liquid, and may be any material that can remove only an oxide film. For example, it is possible to use a gas such as spraying a raw gas such as F2, ClF3, or hydrofluoric acid in the chamber.

The region 12 from which the oxide film is removed by supplying (applying) the chemical solution is not particularly limited as long as the region can be measured. Usually, it is about 1 to 10 mmφ and may have any shape.

Although the supply port 9 and the discharge port 10 for the chemical solution are provided separately, as shown in FIG.
May be used. Further, as shown in FIG. 3, it is not always necessary to provide the probe in the capacitance measuring probe, and it may be provided in another system.

[0017]

According to the present invention, it is possible to provide a semiconductor wafer evaluation apparatus and an evaluation method capable of performing a highly reliable evaluation of a wafer state irrespective of environmental changes.

[Brief description of the drawings]

FIG. 1 is a view showing an apparatus for evaluating a semiconductor wafer according to the present invention.

FIG. 2 is a view showing an apparatus for evaluating a semiconductor wafer according to the present invention.

FIG. 3 is a view showing an apparatus for evaluating a semiconductor wafer according to the present invention.

FIG. 4 is a diagram showing a conventional semiconductor wafer evaluation apparatus.

FIG. 5 is a diagram showing an equivalent circuit at the time of evaluation of a conventional semiconductor wafer.

[Explanation of symbols]

 Reference Signs List 1 wafer 2 stage 3 measuring position adjusting motor 4 capacity measuring probe 5, 6 distance measuring sensor 7 distance adjusting motor 8 chemical solution 9 supply port 10 discharge port 11 surface oxide film 12 area where oxide film is removed 13 supply / discharge port

Claims (3)

[Claims] 1. A means for removing a surface oxide film in a predetermined region of a semiconductor wafer, and a capacitance measuring probe for applying a DC bias voltage to the predetermined region where the surface oxide film has been removed and measuring a capacitance thereof. An apparatus for evaluating a semiconductor wafer, comprising: 2. The method according to claim 1, wherein the means for removing the surface oxide film includes a means for supplying a chemical solution to a predetermined region of the semiconductor wafer, etching the surface oxide film with the chemical solution, and a means for discharging the waste liquid. 2. The apparatus for evaluating a semiconductor wafer according to claim 1, wherein: 3. After removing a surface oxide film in a predetermined region of the semiconductor wafer, a DC bias voltage is applied to the predetermined region from which the surface oxide film has been removed by a capacitance measuring probe to measure the capacitance. A method for evaluating a semiconductor wafer, comprising: