JP2001153635A - Method of evaluating quality of semiconductor wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of evaluating the quality of a semiconductor wafer capable of detecting as mach as possible particles attached to the surface of the semiconductor wafer and crystal originated particles(COPs) present in the vicinity of the surface of the semiconductor wafer, and detecting the attaches particles and the COPs by exactly separating them. SOLUTION: A laser surface inspecting device having a plurality of incident systems and a plurality of light receiving systems is used, all light point defect(LPD) data detected by combining the plurality of incident systems and the plurality of light receiving systems are classified on the basis of being detected by which optical system (combination of the incident system and light receiving system) or being not detected, the LPD which is detected in a system having high detecting sensitivity to recessed defects of COPs and not detected in a system having low detecting sensitivity to the recessed defects of the COPs is decided as the recessed defect of the COP to evaluate the semiconductor 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 evaluating the quality of a semiconductor wafer, and more particularly, to a method for evaluating the quality of a semiconductor wafer, such as an oxide film breakdown voltage, which is present in the vicinity of the surface of the semiconductor wafer which affects the electrical characteristics of the semiconductor wafer. The present invention relates to a method for detecting defects and attached particles and evaluating the quality of a semiconductor wafer.

[0002]

2. Description of the Related Art Conventionally, as a bright point (Light Point Defect (LPD)) detected by a laser surface inspection apparatus, a convex foreign substance such as an adhered particle on a semiconductor wafer or a convex defect (hereinafter referred to as an adhered particle). And a plurality of concave defects [COP (Crystal Originat) due to the crystal quality of the semiconductor wafer.
ed Particles), dislocations and the like] (hereinafter simply referred to as COP including COPs and dislocations) are known. this house,
The adhering particles are observed in a convex shape on the surface of the semiconductor wafer, and the COP is observed in a concave shape such as a square [(100) mirror surface wafer] or a hexagonal [(111) mirror surface wafer] on the semiconductor wafer surface.

[0003] From the viewpoint of the quality evaluation of semiconductor wafers,
It is desirable that these adhering particles and COP can be detected separately. Conventionally, the adhering particles and C
A method for detecting the separation from the OP has been proposed using a two-incident one-light-receiving system or a one-incident two-light-receiving laser surface inspection apparatus. However, this kind 2 incidence 1
In the method using the laser surface inspection apparatus of the light receiving system or the one-incident two-light-receiving system, the discrimination ability between the COP and the adhered particles is not sufficient, and therefore, a plurality (usually two) of the incident systems and a plurality (2) A laser surface inspection device equipped with two or three light receiving systems has been developed. In the separation and detection method using a two-incident two-light-receiving laser surface inspection device, detection is performed by combining each incident system and each light receiving system. By comparing the ratios of the sizes of the LPDs obtained, the adhered particles and CO
Trying to identify P. This is based on the fact that the angle dependency of scattered light is different between a convex adhered particle and a concave COP depending on the laser incident angle on the semiconductor wafer surface. Usually, the scattering intensity in the low angle direction from the COP by the low angle incident laser is weak, and this fact can be used to classify concave defects such as COPs and others.

For example, conventionally, (a) when scattered light when a laser beam is incident at a low angle is detected by a high-angle light-receiving system with respect to the intensity or standard particle-converted size detected by the low-angle light-receiving system; (B) Detection of scattered light when laser light is incident at a high angle with a low-angle light-receiving system, and detection with a high-angle light-receiving system relative to the intensity or standard particle-converted size of laser light incident at a high angle Strength or standard particle equivalent size ratio,
The ratio of the standard particle size calculated in (a) is 1.3 or more and less than 1.9, and the ratio of the standard particle size calculated in (b) is 0.7 or more and less than 1.3. , It was determined that the LPD corresponding to this was a COP existing near the wafer surface.

[0005]

Normally, when it is intended to classify LPDs detected by a laser surface inspection apparatus of a two-incident two-light-receiving system into COPs and adhered particles according to the size ratio, as described above, It was premised that the same point was detected and that an accurate size value was obtained in all four optical systems relating to the two incident light receiving systems.

[0006] Recent laser surface inspection apparatuses have become highly sensitive in order to detect minute foreign matter and defects. For this reason, while it is possible to detect minute foreign substances and defects of 0.08 μm and 0.06 μm (standard particle size),
The dynamic range (the range in which a correct size value can be output in one measurement) is becoming narrower. In addition, since the detection sensitivity to COP varies depending on each optical system composed of a combination of each incident system and each light receiving system, the area which is larger than the detection size range of each optical system and whose accurate size cannot be measured is regarded as an area. Excluded, conversely, in an optical system with low sensitivity, the size of the COP is too small, and it is considered that there are many undetectable ones. Therefore, it is considered that the LPDs detected by the laser surface inspection apparatus that are to be subjected to COP / adhered particle identification are limited to a part of the LPDs.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and detects as many particles as possible adhering to the surface of a semiconductor wafer and COP existing near the surface of the semiconductor wafer as much as possible. C
It is an object of the present invention to provide a method for evaluating the quality of a semiconductor wafer, which can accurately separate and detect an OP.

[0008]

In order to achieve the above object, a semiconductor wafer quality evaluation method (1) according to the present invention comprises a plurality of incident systems and a plurality of light receiving systems. Using a laser surface inspection device, all LPD (Light Point Defect) data detected by combining the plurality of incident systems and the plurality of light receiving systems can be combined with any optical system (the incident system and the light receiving system). Combination)
Classification based on which optical system was not detected, CO
LPs detected by a system with high detection sensitivity for concave defects such as P (Crystal Originated Particles) and not detected by a system with low detection sensitivity for concave defects such as COP
D is determined to be a concave defect such as COP and the semiconductor wafer
It is characterized by evaluating c.

In the case of the method (1) for evaluating the quality of a semiconductor wafer, the LPD detected by a two-incident two-light-receiving laser surface inspection apparatus is attached to the COP according to the size ratio, as in the conventional method. It is not intended to be classified as particles, and therefore 4
It is not assumed that the same point is detected in all three optical systems and that accurate size values are obtained. Therefore, even if the laser surface inspection system is highly sensitive to detect minute foreign matter and defects, and the dynamic range is narrow, the combination of each incident system and each light receiving system Are not excluded as areas where the size cannot be measured accurately because they are larger than the detection size range of each optical system consisting of. Accordingly, the LPDs detected by the laser surface inspection apparatus, which are to be subjected to COP / adhered particle identification, are not limited to a part of the LPDs, thereby greatly increasing the probability of COP detection. Can be.

In the method (1) for evaluating the quality of a semiconductor wafer, all of the LPD data detected by combining a plurality of incident systems and a plurality of light receiving systems can be combined with any optical system. Classified based on which optical system was not detected by the system, and determined LPDs detected by the system with high detection sensitivity to COP and not detected by the system with low detection sensitivity to COP as COP Therefore, it is possible to detect a large number of particles adhering to the surface of the semiconductor wafer and COPs present near the surface of the semiconductor wafer.
Can be accurately separated and detected.

The method for evaluating the quality of a semiconductor wafer (2) according to the present invention is the same as the method for evaluating the quality of a semiconductor wafer (1), wherein the laser surface inspection apparatus has a two-incident two-light-receiving laser surface. It is characterized by using an inspection device. Normally, COP by low angle incidence laser
The scattering intensity in the low angle direction from the surface is low, and if the laser surface inspection device has a two-incident two-light-receiving system, the particles attached to the surface of the semiconductor wafer depend on the incident angle of the laser on the surface of the semiconductor wafer. The fact that the angular dependence of the scattered light is different between the and the concave COP makes full use of the fact that the concave defect such as the COP can be almost certainly classified.

Further, a semiconductor wafer quality evaluation method (3) according to the present invention is characterized in that, in the semiconductor wafer quality evaluation method (1), the classification is 15 classes. When the laser surface inspection apparatus is a two-incident two-light-receiving system, the LPD data is detected by which optical system and which optical system is not detected by combining the incident system and the light-receiving system. According to the semiconductor wafer quality evaluation method (3), the angle dependency of the scattered light is different between the convex adhered particles and the concave COP. Utilizing the differences sufficiently well, concave defects such as COPs and others can be detected and classified almost reliably.

The method (4) for evaluating the quality of a semiconductor wafer according to the present invention is the method for evaluating the quality of a semiconductor wafer according to any one of the methods (1) to (3) described above. An optical system consisting of a combination of 1, high-angle incidence,
When the optical system composed of a combination of high-angle light reception is 2, the optical system composed of a combination of low-angle incidence and low-angle light reception is 3, and the optical system composed of a combination of low-angle incidence and high-angle light reception is 4, L detected by all optical systems
Of the PDs, those determined as concave defects such as COP from the detection size ratio, and the LPDs detected by the 123 optical system, the 12 optical system, and the 1 optical system are COP
It is characterized in that the defect is determined and added.

According to the semiconductor wafer quality evaluation method (4), concave defects such as COP can be detected and classified almost completely without omission, and the quality evaluation of the semiconductor wafer can be performed. Can be accurately performed.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a semiconductor wafer according to the present invention will be described.
An embodiment of the quality evaluation method of C will be described with reference to the drawings. In the semiconductor wafer quality evaluation method according to the embodiment, an LPD detected by a laser surface inspection apparatus having a two-incident two-light-receiving system is first converted by each of the following four optical systems related to the two-incident two-light-receiving system. Classification is based on whether or not it is detected. The maximum number of classifications is 1 as shown in Table 1 below.
It becomes 5.

[0016]

[Table 1] In the conventional method, the LPD to be determined as a COP or an adhering particle is one of the LPDs detected by the laser surface inspection apparatus having the two incident and two light receiving systems as shown in Table 1 above.
Of the mode 1234 out of the 15 categories in the above. The other 14 classifications were not detected by any one or more optical systems, were excluded from the judgment, and meant that the scattering intensity of the undetected optical system was weak. ing.

An optical system composed of a combination of high-angle incidence and low-angle light reception is designated by 1, an optical system composed of a combination of high-angle incidence and high-angle light reception is designated by 2, and an optical system constituted by a combination of low-angle incidence and low-angle reception is designated by 3. If the optical system composed of the combination of low-angle incidence and high-angle light reception is 4, the detection sensitivity to COP is 2>1>4> 3.

In the method for evaluating the quality of a semiconductor wafer according to the embodiment, the coordinates and size data of all LPDs obtained by the above-described optical systems are completely processed. Regarding the data processing, first, for each optical system, two sets of coordinate data of all LPDs are compared. For example, for each LPD detected in the optical system 1, for each LPD detected in the optical system 2,
D is calculated, and the closest optical system 2 is calculated.
The LPD detected in is extracted. If the distance is smaller than a certain value (depending on the detection coordinate accuracy of the laser surface inspection device), it is determined that the two LPDs are the same. Then, the LPD coordinates are compared for all combinations of the optical systems, and all the detected LPDs are compared.
Is detected by which optical system and not detected by which optical system. For each LPD, one set of XY coordinate data and the detected size data of all the detected optical sequences are arranged.

According to this method, all the LPDs detected by the two-incident two-light-receiving laser surface inspection apparatus are reduced to 15
Can be divided into categories. The detection sensitivity to COP for each optical system described above is detected by a system with high detection sensitivity to COP and detected by a system with low detection sensitivity to COP among 15 classifications based on 2>1>4> 3. Among those classified as LPDs that were not
Among the 15 classifications, among the 15 classifications, those classified as LPDs that were detected in a system with low detection sensitivity to COP and were not detected in a system with high detection sensitivity to COP include COP. The LPD that is a COP is extracted by assuming that there is no probability that it has been lost. By organizing all LPDs extracted according to this idea, C
OP can be detected almost without omission, and can be detected while being distinguished from attached particles and the like.

In the conventional method, since the size of the LPD detected by all the optical systems is compared using the laser surface inspection apparatus, the accurate LPD size is obtained by each optical system,
Only D was the target for distinguishing between COP and adhered particles. For this reason, L which should be determined to be a COP
Many LPDs leaked from the PDs. According to the semiconductor wafer quality evaluation method according to the embodiment, all the LPDs detected by the laser surface inspection apparatus are finely classified, so that the conventional LPDs which have been excluded from the subject.
Since the COP and the adhered particles including the PD can be identified, the COP can be detected with almost no omission, and the quality of the semiconductor wafer can be more accurately evaluated.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the method for evaluating the quality of a semiconductor wafer according to the present invention will be described below. Laser surface inspection equipment used: SP-1 / TBI (KL
A-Tencor Co.) 2 incident 2 light receiving system Sample used: 200 mm Cz-Si wafer Wafer crystal plane (100) After cleaning the sample Cz-Si wafer, use the laser surface inspection apparatus described above. LPD was detected.

The coordinates and size data of all LPDs obtained by the four optical systems are processed without omission. Regarding the data processing, first, for each optical system, two LP
The coordinate data of D is compared, and the distance between all LPD coordinate data is calculated. Next, for each LPD detected by a certain optical system, the LPD at the closest distance among the LPDs detected by another optical system is extracted. If the shortest distance is within a predetermined value, it is determined that the LPDs are the same. This predetermined value also depends on the accuracy of the laser surface inspection device used, and considers the error between the coordinate value detected at a high angle incidence and the coordinate value detected at a low angle incidence. In this embodiment, the predetermined value is 300 μm. In each optical system, those determined as the same LPD are removed so as not to overlap.

Next, the data of all the LPDs detected by using the laser surface inspection apparatus are arranged. Table 2 below
A part of the data arranged is shown in FIG.

[0024]

[Table 2] In Table 2, the column of mode shows the optical system detected as LPD. For example, in the case where the optical system 1, the optical system 3, and the optical system 4 detect LPD, mod
The column of e is 134, and the optical system 1 and the optical system 4 are LPD.
In the case of the one detected as, the column of mode is 14. The numbers in the mode column are S1, S
In the columns 2, S3 and S4, and in the columns N1, N2, N3 and N4, it also corresponds to the non-blank portions, and also corresponds to the mode column in Table 1 above.

The X and Y columns show the XY coordinates with reference to the center of the detected LPD wafer.
The columns of S2, S3, and S4 indicate the LPD sizes detected in the respective optical systems. Here, 0 is detected as LPD, but in view of the sensitivity of the detected optical system, L is L.
This indicates that the size of the PD was too large to be measured because the size of the PD was too large.

The columns of N1, N2, N3, and N4 indicate the serial numbers of LPDs detected by the respective optical systems, and the columns of S2 / S1, S4 / S3, and S3 / S1 indicate the respective optical systems. The ratio of the LPD size detected in the system is shown, and the column of No indicates the serial number after eliminating the overlapping LPD of the detected LPD.

Next, the obtained LPD data was classified by each optical system and each detection mode, and a histogram based on the LPD size classification was created. The result is shown in FIG. According to FIG. 1, an optical system 1 composed of a combination of high-angle incidence and low-angle light reception, an optical system 2 composed of a combination of high-angle incidence and high-angle light reception, and an optical system composed of a combination of low-angle incidence and high-angle light reception 4 are 0.08 μm
In contrast to the LPD size detection mode described above, it can be seen that only the optical system of the optical system 3 composed of a combination of low-angle incidence and low-angle light reception is the LPD size detection mode of 0.06 μm or more. .

Among them, the area of the region of mode “1234” detected by all the optical systems 1234 is almost the same among the four optical systems. The difference between the optical systems was detected as Area (LPD having a size larger than the set LPD size range of each optical system) in each optical system, and as a result, the difference was output as size 0 and excluded as no size appeared. The number of minutes.

According to FIG. 1, in the optical system 3 for low-angle incidence and low-angle light reception, an L system having a size of 0.06 μm or more is used.
Most of those detected as PD are high angle incidence,
It can be seen that two optical systems, the low-angle light receiving optical system 1 and the high-angle incident and high-angle light receiving optical system 2, are detected as LPDs having a size of 0.08 μm or more.

Table 3 below shows the number of LPDs detected in each optical system, and Table 4 shows the number of LPDs detected in each mode in 15 classifications.

[0031]

[Table 3]

[0032]

[Table 4] According to Tables 3 and 4, in the case of the COP existing on the Cz-Si wafer, the scattering intensity in the optical system 3 for simply low-angle incidence and low-angle light reception is weaker than the scattering intensity in the other optical systems. It is thought to mean that.

A map in 15 classification modes was reproduced based on the measurement results shown in Table 2 above, and shown in FIG.
As described above, the detection sensitivity to COP is higher than the optical system 2>
Optical system 1> optical system 4> optical system 3, and among 15 classifications, L was detected by a system with high detection sensitivity to COP and not detected by a system with low detection sensitivity to COP.
Among those classified as PD, a large amount of COP was contained, and among 15 classifications, LPD was detected in a system with low detection sensitivity to COP and not detected in a system with high detection sensitivity to COP. In the thing, C
There is almost no probability that an OP is included. From this point of view, the LPD detected in modes 1234, 123, 12, and 1 has a very high probability of being a COP, and is detected in other modes, such as mode 124 and mode 13. LPDs have a very low probability of being COPs.

The total number of LPDs to be distinguished between the COP and the adhering particles detected by the conventional method is Mode 1
234 out of 136, and among them, 131 were determined to be COP based on the detection size ratio.

The number of LPDs detected in the modes 123, 12, and 1 that can be determined to be COP by the method according to the embodiment is 85 + 74 + 48, that is, a total of 207 LPDs. 33 in total
There were eight.

Since the total number of LPDs detected by the four optical systems was 512, the LPDs determined as COPs
Increased from 25.6% in the conventional method to 66% in the method according to the example, and the detection rate of COP was improved to 2.6 times. Further, the size of the COP detected in the embodiment is the same as the COP detected by the conventional method.
Since the size is smaller than the size of P, it can be said that the determination method according to the embodiment is a more sensitive determination method.

Further, a mode 123 which can be determined as COP,
The map was reproduced by adding the data in mode 12 and mode 1 and compared with the map in mode 1234. These reproduction maps are shown in FIG. This figure 3
From the COP distribution area by the mode 1234 and the mode 1
23, mode 12, and mode 1, the comparison between the COP distribution regions by mode 123, mode 12, and mode
It can be seen that the area according to C1 has a wider area. It has been found that the in-plane size distribution of the COP is generally large at the central portion of the wafer and smaller at the outer peripheral portion.

The LPD data shown in Table 2 and the semiconductor wafer in which the COP generation area on the wafer surface is smaller than the wafer shown in Table 2 were prepared, and LPD was similarly detected. The concentric area is divided into 10 and the L
The average value of the PD size was calculated and shown in FIG. The LPD size in mode 1234 is larger than the LPD size in mode 123, mode 12, and mode 1, which implies that only the
If the OP is detected and identified, a relatively large CO
It became clear that there was a high possibility that only P was detected.

Next, the first semiconductor wafers having different COP generation regions on the wafer surface are in the mode 1 mode.
Based on the LPD data detected by the H.234, an optical system 1 for high-angle incidence and low-angle reception, an optical system 2 for high-angle incidence and high-angle reception, and an optical system 3 for low-angle incidence and low-angle reception
And low-angle incident, high-angle light receiving optical system 4
The size ratio (narrow / wide) of D was obtained, and this was shown as a histogram in FIG. It can be seen that the LPD size ratio of most of the LPDs detected by the optical system 1 for high-angle incidence and low-angle reception and the optical system 2 for high-angle incidence and high-angle reception is 1. On the other hand, most of the LPDs detected by the optical system 3 for low-angle incidence and low-angle reception and the optical system 4 for low-angle incidence and high-angle reception were concentrated around the LPD size ratio of 1.5.

In the case of adhered particles, the angle dependence of laser light scattering is not expected to be much different from the standard particles, and the optical system 1 for high-angle incidence and low-angle light reception, the optical system 2 for high-angle incidence and high-angle light reception 2, The LPD size ratio should be close to 1 in any of the optical system 3 for low-angle incidence and low-angle light reception and the optical system 4 for low-angle incidence and high-angle light reception. Of the LPDs detected this time,
That is, a large amount of particles that are adhered were not included. It is considered that this is because the number of attached particles was actually small, and moreover, many of the attached particles exceeded the measurable LPD size.

[Brief description of the drawings]

FIG. 1 is a graph in which LPD data obtained in an embodiment according to the present invention is classified by each optical system and each detection mode, and is represented by a histogram according to LPD size classification.

FIG. 2 is a graph showing a map of 15 classifications reproduced based on LPD data obtained in an example.

FIGS. 3 (a) and 3 (b) show a mode 123 and a mode 1 capable of determining a COP based on LPD data obtained in the embodiment.
2 is a graph showing a reproduction map obtained by adding data in mode 1 and a reproduction map in mode 1234.

FIG. 4 shows LPD data obtained in the embodiment divided into 10 parts by concentric regions of the wafer, and LPDs existing in each region.
It is the graph which calculated and showed the average value of the size.

FIG. 5 shows an optical system 1 for high-angle incidence and low-angle light reception and an optical system 2 for high-angle incidence and high-angle light reception based on LPD data detected by a mode 1234 according to the embodiment; The size ratio (narr) of the LPD is divided into an optical system 3 for low-angle incidence and low-angle reception and an optical system 4 for low-angle incidence and high-angle reception.
ow / wide), and this is shown as a histogram.

Claims (4)

[Claims] 1. A laser surface inspection apparatus having a plurality of incident systems and a plurality of light receiving systems, and all LPDs (Lights) detected by combining the plurality of incident systems and the plurality of light receiving systems. Point Defect) Data is detected by any optical system (combination of incident system and light receiving system)
Classification based on which optical system was not detected, CO
LPs detected by a system with high detection sensitivity for concave defects such as P (Crystal Originated Particles) and not detected by a system with low detection sensitivity for concave defects such as COP
D is determined to be a concave defect such as COP and the semiconductor wafer
A method for evaluating the quality of a semiconductor wafer, comprising: evaluating the quality of a semiconductor wafer. 2. The method for evaluating the quality of a semiconductor wafer according to claim 1, wherein a laser surface inspection device of a two-incident two-light-receiving system is used as said laser surface inspection device. 3. The semiconductor wafer quality evaluation method according to claim 1, wherein said classification is 15 classifications. 4. An optical system comprising a combination of high-angle incidence and low-angle reception, an optical system comprising a combination of high-angle incidence and high-angle reception, and an optical system comprising a combination of low-angle incidence and low-angle reception When the optical system composed of a combination of low-angle incidence and high-angle light reception is defined as 4,
Among the LPDs detected by all the optical systems of No. 4, those determined as concave defects such as COP from the detection size ratio, and those detected by the 123 optical systems, the 12 optical systems, and the 1 optical system 4. The quality evaluation method for a semiconductor wafer according to claim 1, wherein the determined LPD is determined as a concave defect such as a COP and added.