JPH03252151A - Evaluation of semiconductor wafer - Google Patents

Abstract

PURPOSE:To obtain a method which allows sure and simple detection of cracks of waters by mounting a wafer on a support member having a cavity opening in top with the inspection face downward and by applying a preset fixed load at the center of the wafer to judge whether microcracks are present from fractures. CONSTITUTION:For evaluation of a semiconductor wafer to judge whether microcracks are present in its inspection face, a semiconductor water 5 is mounted on a support member 2 having a cavity opening in top with its inspection face downward, and the center of the semiconductor wafer 5 is applied with a preset fixed load to judge it from fractures whether microcracks are present. For example, used is a device 1 consisting of a ring-shaped support member 2 grooved 4 for mounting the wafer's peripheral edge and an indenter 3 with a 5-40mm diameter R in the tip. A critical value of the breakdown strength of a crack-free normal standard article is predetermined, and it is applied with a loading at a value of about 95% of the critical value to judge whether microcracks are present from fractures.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for evaluating semiconductor wafers, particularly for inspecting the presence or absence of minute cracks that are difficult to detect by visual inspection or X-ray diffraction. It is effective in doing so.

[Prior Art] Semiconductor wafers (hereinafter abbreviated as wafers) are subjected to strong stress and the like due to heat treatment, film deposition, etc. in the manufacturing process of semiconductor elements. If there are cracks in the wafer at this time, part of the wafer may be chipped. Also, part of this chipped wafer becomes a particle,
It may also become a hindrance in the semiconductor device manufacturing process.

Therefore, when wafers are shipped, visual inspection or evaluation by X-ray diffraction is performed to check for the presence of cracks, and wafers with cracks are removed.

[Problems to be Solved by the Invention] However, depending on such conventional wafer inspection methods, there is a problem that cracks that are too small cannot be discovered when visual inspection is performed. Furthermore, in the case of inspection by X-ray diffraction, there is a problem that it is difficult to distinguish between processing strain (plastic strain and elastic strain) and cracks. Furthermore, with any of the above inspection methods, inspecting the entire wafer surface requires a considerable amount of time and effort, making it a difficult task in practice.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a semiconductor wafer evaluation method that can reliably and easily detect cracks in a wafer.

[Means for Solving the Problems] The invention of the first claim is such that a semiconductor wafer is placed on a supporting member having a hollow portion opening on the upper surface with the surface to be inspected facing downward, and a central portion of the semiconductor wafer is placed in advance. A predetermined constant load is applied, and the presence or absence of a microcrank is determined based on the presence or absence of breakage. The semiconductor wafer is placed with its inspection surface facing downward, and a predetermined amount of deformation is applied to the semiconductor wafer, and the presence or absence of microcracks is determined based on the presence or absence of breakage.

"Function" Hereinafter, the method for evaluating the semiconductor wafer I\ of the present invention will be explained in detail.

When a silicon single crystal is exposed to an external force at temperatures below 650°C,
Unlike metals, it does not undergo elastic or plastic deformation, but has the property of suddenly undergoing brittle fracture during elastic deformation. It is known that this brittle fracture strength changes very sensitively depending on the presence or absence of cracks, and is rapidly reduced by the presence of cracks.

The method of the invention of claim 1 uses the brittle fracture strength sensitive to the crank as an index, and indicates that the crack exists when the fracture strength is lower than the lower limit of the critical value of the strength leading to the fracture of a wafer without cracks. It takes advantage of what can be considered a wafer. To this end, first, the critical value of the breaking strength of a normal standard product with no cracks is determined, and then the range of statistical variation thereof is also determined.

After determining the critical value of the breaking strength of a normal wafer with no cracks in this way, the semiconductor wafer is placed with the surface to be inspected downward on a support member having a cavity opening on the top surface. A load of approximately 95% of this critical value is applied from above to the center of the wafer, and the presence or absence of microcracks is determined based on the presence or absence of breakage.

In this way, when evaluating the presence or absence of cracks in a wafer, the above-mentioned breaking strength is evaluated based on the relative value of the breaking strength compared to a normal standard product with no cracks, rather than evaluating the absolute value each time. It is easier to do so.

Further, the invention of claim 2 utilizes the fact that the amount of deformation of silicon can be sensitive to cracks. For this purpose, the limit of the amount of deformation of a normal standard product with no cracks under a certain load is determined, and the range of statistical variation thereof is also determined. Then, a semiconductor wafer is placed on a support member having a cavity opening on the top surface with the surface to be inspected facing downward, and a constant load is applied to the center of the semiconductor wafer until the amount of deformation reaches the above limit value. The presence or absence of microcracks is determined by whether or not they are present.

[Example] Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows an example of an apparatus for evaluating the presence or absence of cracks in a semiconductor wafer according to the present invention.

The device 1 consists of a ring-shaped support member 2 having a cavity opening on the top surface and an indenter 3. A groove 4 is formed in the support member 2 for placing the peripheral edge of the wafer.

In order to evaluate the presence or absence of cracks in a wafer using this apparatus 1, first the wafer 5 is placed on the support member 2 by placing its peripheral edge 5a on the groove 4. At this time, the wafer 5 should be placed on the back side of the surface to be inspected or on the indenter 3 side.

The dimensions of this support member 2 are 3-o3 to 10-. It is 3 inches, which corresponds to the size of the wafer placed on it. In addition, the dimensions of the groove portion 4 are 0.3 to 1 in width,
It is about 0 mm. By doing this, when the center portion 6 of the wafer 5 is pressed by the indenter 3, force is applied to the entire wafer 5.

Further, the indenter 3 has a diameter R of 5 to 4 C) nm and a weight of 1 to 500 g. In order to obtain data with good reproducibility, the speed at which the indenter 3 is brought into contact with the wafer 15 is preferably set within a range of 0.1 to 500117 minutes.

450 μm thick from a silicon single crystal ingot made by Czochralski pulling method.

A 4-inch Ueno\ with surface orientation (100) was created.

The above wafer creation process involves slicing a silicon single crystal ingot and then using HF and HNO3 to remove distortion.
After chemical etching was performed using an etching solution containing CH, COOH mixed in a volume ratio of 1:3:1, lapping and surface polishing were performed. Sample A was obtained by chemical etching for 100 seconds, and sample B was obtained by chemical etching for 10 seconds.

The breaking strength of the sample A and sample B wafers prepared through the above steps was determined using the apparatus and tensile tester shown in FIG. 1, respectively. The results are shown in FIG.

From Figure 2, there is a clear difference in the distribution of fracture strength between Sample A (12 sheets), whose chemical etching time was 100 seconds, and Sample B (20 sheets), whose chemical etching time was 10 seconds. I understand. From this, it can be seen that the wafer (sample B) for which the chemical etching time was 10 seconds had a slight rack. Therefore, in this case, the lower limit (I (20 kg weight) of the breaking strength of the wafer of sample A, which is a normal wafer (wafer without cracks), is the critical strength.

Therefore, the upper limit of the fracture strength due to the presence of cracks in the wafer created by the above processing process is 20
Set the value to approximately 95% of the kg weight.

The amount of deformation of the wafer when a force of 20 kg was applied to the wafer by the indenter 3 of the apparatus 1 was 2.degree. 10 mm as measured by a displacement meter in a tensile tester. Therefore, in the method of the present invention, this deformation amount is 2.1O
If the indenter 3 is set to stop at about 95% of n+m and tested, the presence or absence of cracks in the wafer can be determined very easily and reliably.

[Effects of the Invention] As described in detail above, according to the semiconductor wafer evaluation method of the present invention, the invention of the first claim is such that the semiconductor wafer to be inspected is placed on the support member having the hollow portion opening on the upper surface. The semiconductor wafer is placed with its surface facing downward, a predetermined constant load is applied to the central part of the semiconductor wafer, and the presence or absence of microcracks is determined based on the presence or absence of breakage.
A semiconductor wafer is placed with the surface to be inspected facing downward on a support member having a cavity opening on the top surface, a predetermined amount of deformation is applied to the semiconductor wafer, and the presence or absence of microcracks is determined based on the presence or absence of breakage. Therefore, the presence or absence of microcracks on the entire wafer can be evaluated reliably and easily.

Therefore, if the wafer 1 is managed using this method, it is possible to reliably eliminate wafers and the processing process itself in which cracks and defects, which have been overlooked in the past, are present, and this greatly contributes to improving productivity and reliability.

[Brief explanation of drawings]

Figure 1 shows an example of an apparatus for evaluating the presence or absence of cracks in semiconductor wafers according to the present invention, and Figure 2 shows an example of the apparatus and tensile testing machine shown in Figure 1 for semiconductor wafers processed in different processing steps. This is a graph showing the results of determining the fracture strength using frequency. 2... Supporting member, 5... Semiconductor wafer 5a... Peripheral end, 6... Center of semiconductor wafer.

Claims (2)

[Claims] (1) In a semiconductor wafer evaluation method that determines the presence or absence of microcracks on the surface to be inspected of a semiconductor wafer, a semiconductor wafer is placed with the surface to be inspected downward on a support member having a hollow portion opening on the top surface. A semiconductor wafer evaluation method characterized by applying a preset constant load from above to the center of the semiconductor wafer, and determining the presence or absence of microcracks based on the presence or absence of breakage. (2) In a semiconductor wafer evaluation method for determining the presence or absence of microcracks on the surface to be inspected of a semiconductor wafer, a semiconductor wafer is placed with the surface to be inspected downward on a support member having a cavity portion opening on the upper surface; A method for evaluating a semiconductor wafer, which comprises applying a predetermined amount of deformation to the semiconductor wafer, and determining the presence or absence of microcracks based on the presence or absence of breakage.