JPH0476936A - Defect inspection device - Google Patents

Abstract

PURPOSE:To improve the accuracy in detection of defects and dust by judging the scattered lights, which deviate greatly from the intensity distribution of the scattered lights which occur in a fixed cycle, to be the scattered lights from detects or dust. CONSTITUTION:By near wafer scanning 1 with a laser beam, the coordinate position distribution 2 of scattered light intensity is sought. Next, it is judged whether the scattered lights have periodity or not, if NO, the defects or dust is the cause, and if YES, in the next place, the scattered light intensity distribution at the severally corresponding specified position in each pattern is sought. And it is judged whether the objective peak is deviating greatly from the intensity distribution, and if YES, it is judged that the defects or dust is the cause, and if NO, it is judged that the pattern is the casue. If one judges and removes the scattered lights caused by patters in such an order, the defects or dust can be detected accurately.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a defect inspection device for detecting minute defects and dust on a substrate used in a semiconductor device.

(Prior Art) In the manufacturing process of semiconductor devices, it is important to detect defects and dust on the surface of a semiconductor wafer and to know the surface condition of the semiconductor wafer in order to ensure the quality of the product.

Diffuse reflection of light is usually used to detect defects and dust on the wafer surface. For example, a laser beam is applied at a low angle of about 10 degrees to the wafer surface, and the scattered light reflected by defects and dust is received by a photomultiplier tube, etc., and then processed by a computer to detect its intensity, position, etc. It is something to do. To use a defect inspection device that utilizes this diffused reflection of light, first, a wafer on which the same pattern is formed for each IC chip is placed on the XY coordinates (see Figure 1). A laser beam is projected diagonally and scanned at a certain position on the Y-axis in the X-axis direction along arrow A. The scattered light is detected by a photomultiplier tube and processed by a computer to identify defects and dust. Record the intensity of scattered light. By performing this operation at any position on the Y axis, the state of the entire wafer surface can be known. FIG. 2(a) shows the coordinate position distribution of the scattered light intensity for one chip (for example, region B) in one cycle at the Y coordinate of the wafer. The white peaks indicate scattered light from the pattern. Black peaks indicate scattered light from defects and dust. In this way, the coordinate position distribution of scattered light intensity includes scattered light from defects and dust and scattered light from patterns. Therefore, defects etc. cannot be accurately detected unless the scattered light from the pattern is removed. In this distribution, scattered light from the pattern occurs at a constant period corresponding to the chip size. On the other hand, scattered light from defects and the like occurs irregularly. In order to detect only the scattered light from defects etc. from among the scattered light from such mixed sources, the intensity of scattered light from defects and dust is comparatively higher than the intensity of scattered light from bumps. There is a method to take advantage of the large size, but in this case, the scattered light detection level 3 must be set quite high in order to completely eliminate the influence of scattered light from the pattern.

In this case, scattered light from defects and the like having an intensity of scattered light detection level 3 or lower is removed together with scattered light from the pattern, resulting in a decrease in detection sensitivity (see FIG. 2). Therefore, currently, the scattered light detected at a constant period corresponding to the chip size is removed by signal processing as scattered light from the pattern, and the sensitivity is increased by setting the scattered light detection level 3' low. (See Figure 2(b)). FIG. 3(a) shows a conventional defect/dust detection procedure. [Wafer scanning with laser light] 1 is performed to obtain [coordinate position distribution of scattered light intensity] 2, and by removing periodic light from the scattered light, defects and dust are detected. However, in this method, for example, if there is a defect or dust near the pattern edge, the scattered light overlaps with the scattered light from the pattern edge, so that Even though there are defects and dust, the signal is processed as scattered light from the pattern. This method focuses only on the positional periodicity and does not take into account its strength, so it cannot detect defects or dust that overlap pattern edges. Highly integrated I
In a C chip, the area occupied by the pattern edge portion in the area thereof tends to increase more and more, and it is no longer possible to ignore the existence of defects and dust hidden in the pattern edge.

(Problem to be Solved by the Invention) As mentioned above, conventional defect inspection equipment cannot accurately detect defects and dust on the surface of a semiconductor wafer because the light scattered by the pattern is mixed with the light scattered by the defects and dust. The problem was that I couldn't do it. The present invention was made under these circumstances, and provides a defect inspection device that is capable of detecting defects and dust that overlap pattern edges so that defects and dust on a wafer can be detected more accurately and with high sensitivity. is intended to provide.

[Structure of the invention]

(Means for Solving the Problems) The present invention detects scattered light generated by scanning light or laser light over a substrate on which the same pattern is repeatedly formed at a constant period. It relates to a defect inspection device characterized by detecting defects and dust, and includes means for detecting scattered light that occurs at regular intervals, and means for determining the intensity distribution of scattered light at the same corresponding position in each pattern. It is characterized in that among the detected scattered light, the scattered light that deviates from the intensity distribution within a certain range is separated from the scattered light from the pattern as scattered light from defects and dust.

(Function) Defects and dust can be detected accurately by determining that scattered light that deviates significantly from the intensity distribution of scattered light that occurs at regular intervals is scattered light from defects and dust.

(Example) An example of the present invention will be described below with reference to the drawings. 1st
The figure shows a circular semiconductor wafer to which the defect inspection device is applied, and chips of the same pattern are continuously formed in the X%Y direction.

Although the present invention uses light such as a laser, this embodiment will be explained using Ar laser light. All chips on the wafer are scanned to detect defects on the surface.
Scan in the X-axis direction like this.

The laser beam scans the surface of the wafer at an angle of approximately 10 degrees, and the scattered light is detected by a photomultiplier tube and processed by a computer to measure the intensity of the scattered light. The results are shown in Figure 4 (a
). The scanning area shown in this figure is area B within arrow A, and the surface condition of this area can be seen. In this device, peaks indicating the intensity of scattered light appear due to patterns and defects or dust. The white lines 11 indicate scattered light from the pattern,
Occurs at regular intervals corresponding to the chip size.

This is because all chips have the same pattern. Black peak] 2.12'12' is scattered light from defects and dust, and since it does not have periodicity and occurs irregularly, it often occurs at pattern edges. If the influence of scattered light from the pattern is removed from the scattered light intensity distribution in this figure, surface defects and dust are expressed as they are. When a high detection level 13 is set, only the peak 12.12' with a large scattered light intensity is detected, resulting in a decrease in detection sensitivity.On the other hand, when a low detection level 13' is set, scattered light from the pattern is picked up. This occurs as described above.

In order to compensate for the above drawbacks, the present invention takes advantage of the fact that scattered light from a pattern repeatedly occurs at a constant period corresponding to the chip size on a wafer, and in particular, separates the scattered light from the pattern into two types. It is characterized by being excluded from. FIG. 3(b) illustrates the procedure for implementing the present invention.

[Wafer scanning by laser light] [Coordinate position distribution of scattered light intensity] 2 is determined by 1. Next, determine whether there is periodicity in the scattered light in step 3. If NO, it is due to a defect or dust, and if YES, next, determine the scattered light intensity distribution at the corresponding specific position within each pattern. seek. Then, it is determined whether the target peak deviates significantly from the intensity distribution. If YES, it is determined that the cause is a defect or dust, and if No, it is determined that the pattern is the cause. If scattered light caused by the pattern is determined and removed in this order, defects and dust can be detected accurately.

Specifically, the intensity distribution of scattered light at corresponding specific positions within each pattern is determined as follows. first,
The specific position is the position where the peak 12' shown in FIG. 4(a) is located. Then, the distribution of the scattered light intensity of the peak corresponding to this position is investigated, and a diagram is created. In this figure, the Y-axis represents the scattered light intensity, and the X-axis represents the frequency at which each intensity appears. Those within a particular distribution are represented by white circles, and those that deviate significantly are represented by black circles. In a certain distribution range, the intensity “
White circles are concentrated at the 4″ level.

This is considered to form a constant intensity distribution because the patterns are made of the same material and shape. Therefore, such scattered light within a certain intensity distribution is determined to be from the pattern and is removed by signal processing. Also, strength 1
There are black peaks, such as 1.12, that are far outside the specific distribution range.

There is a high possibility that this is not scattered light from the pattern, but scattered light from defects and dust that overlap with the batten edges, so scattered light that deviates significantly from a specific distribution range is removed as scattered light from defects and dust. (See Figure 4(b)). As shown in this figure, in the conventional defect inspection apparatus, peak 12', which is removed as scattered light from the pattern, remains as scattered light from defects and dust. Through the above processing, only the scattered light from the battens can be removed without removing the scattered light from defects and dust at the pattern edges, making it possible to detect defects and dust accurately and with high sensitivity. .

In the embodiment, light was used for scanning, but the present invention
The method is not limited to this, and for example, ultrasonic waves may be used, although there are problems with sensitivity.

The substrate is not limited to semiconductors, and any substrate having a repeated pattern on its surface can be used.

〔Effect of the invention〕

According to the present invention, with the above-described configuration, defects and dust can be detected accurately and with high sensitivity.

[Brief explanation of drawings]

FIG. 1 is a plan view of a wafer used in the present invention, and FIG.
) is a coordinate position distribution map of the scattered light intensity detected by a conventional defect inspection device, FIG. 2(b) is a coordinate position distribution map of the scattered light intensity excluding the scattered light peak from the previous pattern, and FIG.
41N(a) is a coordinate position distribution diagram of scattered light intensity by the defect inspection apparatus of the present invention; FIG. (b
) is a coordinate position distribution diagram of the scattered light intensity excluding the scattered light peak from the pattern, and FIG. 5 is a diagram showing the frequency of the scattered light intensity of the present invention. 1.11...Scattered light from pattern, 2.2', 2
'...Scattered light from defects/dust, 12.12',
12'...Scattered light from defects/dust, 3.13...High detection level, 3', 13'...Low detection level. (8733) Representative Patent Attorney Yoshiaki Inomata (1 other person)
(b) Figure 1 NO Es Figure 3 ANO AYES AYES N0 (b) Figure 3 (f)) Figure

Claims (1)

[Claims] Defect inspection characterized by detecting defects and dust on the surface of a substrate by detecting scattered light generated by scanning light or laser light over a substrate on which the same pattern is repeatedly formed at a fixed period. The apparatus includes means for detecting scattered light generated at a constant period, and means for determining the intensity distribution of the scattered light at the same corresponding position in each of the patterns, and detecting the intensity of the detected scattered light within a certain range. A defect inspection device characterized in that scattered light that deviates from the distribution is excluded from scattered light from a pattern as scattered light from defects or dust.