JPH05232165A - Method for measuring in-plane distribution of resistivity of semiconductor wafer - Google Patents

Abstract

(57) [Summary] [Object] To provide a measuring method capable of obtaining a specific resistance distribution of a semiconductor wafer with higher resolution. [Structure] A plurality of strip-shaped electrodes are formed substantially parallel to one surface of a semiconductor wafer, and a plurality of strip-shaped electrodes arranged substantially parallel to each other are arranged on the other surface so as to be substantially orthogonal to the strip-shaped electrodes arranged on the one surface of the wafer. Form. From these strip-shaped electrodes, a voltage is applied only between electrodes selected one by one on each surface of the wafer, and the flowing current is measured to obtain the specific resistance at each intersection of both strip-shaped electrodes. This measurement is sequentially performed at the intersections of the electrodes to obtain the specific resistance distribution on the entire surface of the wafer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for measuring in-plane distribution of resistivity of a semiconductor wafer.

[0002]

2. Description of the Related Art With the miniaturization of semiconductor chips, microscopic in-plane uniformity of a semiconductor wafer is becoming more and more important.
A conventional method for measuring a minute distribution of specific resistance in a semiconductor wafer will be described with reference to FIG. In this, a large number of circular electrode patterns (patterns in which circular electrodes are punched on the entire surface electrode) are formed on the front surface, and the substrate 6 provided with the entire surface electrode 5 on the rear surface is set on an autoprober and the probe is used as an electrode. Make contact.

That is, a bias voltage V is applied between a specific circular electrode 4 to be measured and the electrode on the back surface, the flowing current is measured, and the other circular electrodes are also measured in the same manner.
The specific resistance distribution on the entire surface of the wafer is obtained. At this time, circular electrodes other than the circular electrode for measurement are opened, and the other electrodes are grounded. Assuming that the flowing current is I, the area of the circular electrode is S, and the thickness of the wafer is t, the specific resistance is ρ = VS / It (Ω ·
cm) is obtained (actually, S is corrected, but this point will be described in detail later).

[0004]

However, in this method, the size of the circular electrodes and the distance between the electrodes are the minimum size of the probe tip (the minimum size of the probe tip diameter is about 40 μm) because the probe needs to contact the circular electrodes. In some cases, it was not possible to measure the resistivity microdistribution with sufficient resolution. Therefore, an object of the present invention is to provide a measuring method capable of obtaining a minute distribution of specific resistance with higher resolution.

[0005]

A feature of the measuring method of the present invention is that a plurality of strip electrodes are formed substantially parallel to one surface of a semiconductor wafer and a plurality of strip electrodes arranged substantially parallel to each other are formed on the other surface of the semiconductor wafer. , Is formed so as to be substantially orthogonal to the strip electrodes arranged on the one surface of the wafer, and a voltage is applied only between the electrodes selected one by one from each of the strip electrodes on each surface of the wafer,
The purpose is to determine the specific resistance by measuring the flowing current.

Further, the wafer used for the measurement has a plurality of strip-shaped electrodes formed on one surface substantially in parallel, and a plurality of strip-shaped electrodes arranged substantially in parallel on the other surface, substantially orthogonal to the strip-shaped electrodes arranged on the one surface. It is characterized in that it is formed to.

A specific example of the present invention will be described below with reference to FIGS. FIG. 1A is an explanatory view of the measuring method of the present invention, in which a plurality of strip-shaped electrodes are arranged substantially parallel to each other on the surface of the substrate. On the other hand, strip-shaped electrodes are also arranged substantially parallel to each other on the back surface of the substrate, but the direction thereof is formed to be substantially orthogonal to the strip-shaped electrodes on the front surface.

A partially transparent plan perspective view of this electrode is shown in FIG. 2B. The solid line shows the electrode on the front surface of the substrate, and the broken line shows the electrode on the back surface of the substrate. Thus, the electrodes 1 on the front surface and the back surface are formed in a grid shape when seen in a perspective view. A substantially rectangular probe contact pad 2 is provided integrally with the electrode at one end of each strip electrode 1. In order to prevent the pads of the adjacent electrodes from overlapping with each other, the positions where the pads 2 are provided may be alternately changed as in this example.

A voltage can be applied between the front and back electrodes of the substrate as shown in (A), and the flowing current can be measured with an ammeter. Next, actual measurement will be described with reference to FIG. This figure is a perspective view of the substrate on which the electrodes described above are formed. First, one strip electrode is selected from each surface of the substrate. For example, A ₁ is selected as the front surface side electrode and B ₁ is selected as the back surface side electrode, probes u and o are brought into contact with each pad, and a voltage is applied between both electrodes. Then, when viewed as a perspective view, at a position where the electrode A ₁ and the electrode B ₁ intersect, a vertical electric field in the substrate B ₁ to A ₁
Current flows through. If this current is measured with an ammeter connected to the probe o and the area of the intersecting electrode portions is S,
The specific resistance can be obtained from the above equation.

Further, with the probe u fixed to B ₁ , the probe o is sequentially moved to A ₂ , A ₃ ... And the same measurement is performed to obtain the specific resistance distribution along B ₁ . Then, when the measurement along B ₁ is completed, the probe u is moved to B ₂ this time, and the similar measurement is repeated, whereby the specific resistance distribution on the entire surface of the substrate can be measured.

The area S of the intersecting electrode portions is corrected in consideration of so-called shape effect. If full-scale electrodes are formed on both surfaces of the substrate, the current density is isotropic as shown in FIG. However, in the case of the electrode used in the present invention, the current density is not isotropic in the interval between the electrodes as shown in FIG. Therefore, when the width of the strip electrode is l, the area of the intersection of the electrodes is l ² because it is a square with one side l, but the actual current is slightly wider than the electrode width l.
It may be corrected to S = (l + u) ^{2 as} shown in FIG. Therefore, if the voltage is V, the current is I, and the thickness of the substrate is t, the specific resistance ρ = V · (l + u) ² / It can be obtained. This correction method is a calculation method used even when a conventional circular electrode is used.

[0012]

As described above, the strip electrodes are arranged so as to intersect on the front and back of the substrate, and the current flowing at each intersection is measured, so that the resolution of the resistivity distribution depends on the probe tip diameter and the like as in the conventional case. It is possible to measure a finer specific resistance distribution.

[0013]

EXAMPLE An electrode as shown in FIG. 2 was formed on a substrate and the specific resistance distribution was actually measured. The electrodes are configured such that the width of the strip-shaped electrode is 15 μm, the distance between adjacent electrodes is 15 μm, and the probe pad is rectangular with a side of 30 μm. First, the probe u is brought into contact with the electrode A ₁ and the probe o is brought into contact with the electrode B ₂ , and a bias of 10 is applied to the probe u.
V was applied and the current was measured. Then, as described above, the probe o was sequentially moved from A2 to A1500 and the same measurement was performed to measure the specific resistance distribution along B ₁ . Furthermore, when finished to A1500, moving the probe u in B _2, was measured current by repeating the same measurement below. As a result, the resistivity distribution on the entire surface of the wafer is 30.
It was confirmed that measurement can be performed at μm intervals.

[0013]

As described above, according to the method of the present invention, the resistivity distribution can be measured with a resolution that cannot be measured conventionally. Further, the wafer of the present invention can effectively carry out the method of the present invention. Therefore, it is effective when used for evaluation and inspection of a semiconductor wafer that requires high in-plane uniformity of resistivity.

[Brief description of drawings]

FIG. 1 is an explanatory view of a method of the present invention, (A) is a configuration diagram of a measurement system, and (B) is a plan perspective view of electrodes.

FIG. 2 is an explanatory view of the arrangement of electrodes used in the method of the present invention.

3A and 3B are explanatory views regarding a shape effect, where FIG. 3A is a case where full-face electrodes are provided on both surfaces of a substrate, FIG. 3B is an electrode used in the method of the present invention, and FIG. It is explanatory drawing which shows the correction method of a partial area.

FIG. 4 is an explanatory diagram of conventional resistivity distribution measurement.

[Explanation of symbols]

 1 band electrode 2 probe contact pad 3, 6 substrate 4 circular electrode 5 full surface electrode

Claims (2)

[Claims] 1. A semiconductor wafer having a plurality of strip electrodes formed substantially parallel to one surface thereof, and having a plurality of strip electrodes arranged substantially parallel to each other on the other surface thereof and being substantially orthogonal to the strip electrodes arranged on the entire surface of the wafer. Of the semiconductor wafer, the voltage is applied only between the electrodes selected one by one on each surface of the wafer from these strip electrodes, and the specific resistance is obtained by measuring the flowing current. Method for measuring in-plane distribution of resistivity. 2. A plurality of strip-shaped electrodes formed on one surface substantially parallel to each other, and a plurality of strip-shaped electrodes arranged substantially parallel on the other surface,
A semiconductor wafer for measuring in-plane distribution of resistivity, which is formed so as to be substantially orthogonal to the strip electrodes arranged on the one surface.