JP2002014055A - Foreign object inspection apparatus and method - Google Patents

Abstract

(57) [Problem] To provide a foreign substance inspection apparatus and method capable of determining the size and shape of a foreign substance in the foreign substance inspection on the surface of an inspection object. SOLUTION: A foreign matter judging means 7 judges foreign matter on the surface of a test object based on detection data composed of a plurality of pixels of a detecting means 6 for detecting a state of the surface 1 of the test object, and outputs foreign matter extraction data. The computing means 8b divides the foreign substance extraction data into groups each having a predetermined number of pixels and counts the number of pixels regarded as foreign substances in the group for each group. The judging means 10 performs a judging process for estimating the size of the foreign matter in the unit area corresponding to the group based on the number of foreign matter pixels for each group obtained by the calculating means 8b.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a foreign matter inspection apparatus and method, and more particularly to a foreign matter inspection apparatus and method for detecting a minute foreign matter on a surface to be inspected, a defect such as an uneven scratch or a scratch with high sensitivity, and for example, a semiconductor device. Detects foreign matter and defects such as uneven scratches and scratches attached to the surface of a wafer (hereinafter, referred to as a wafer), mask, reticle, glass substrate, etc., and inspects the size (particle size) and shape of the foreign matter and defect. The present invention relates to a foreign matter inspection device and method.

[0002]

2. Description of the Related Art In the process of manufacturing a semiconductor integrated circuit (eg, IC), if foreign matter adheres to the surface of a wafer or various patterns for forming a semiconductor region, an insulating region, an electrode, a wiring, etc., the performance of the IC deteriorates. Therefore, after the pattern is formed, an inspection for the presence or absence of foreign matter on the wafer surface is performed by a foreign matter inspection device.

In order to manufacture an IC with a high yield, foreign substances adhering to the wafer surface are detected, the size (particle size) and shape of the foreign substances are inspected, and various semiconductor manufacturing apparatuses and processes are cleaned. It is necessary to grasp the degree quantitatively and manage the manufacturing process appropriately. 2. Description of the Related Art Conventionally, as a foreign substance inspection apparatus for inspecting the size and shape of a foreign substance, for example,
There is an apparatus disclosed in Japanese Patent Application Publication No. 1-51622.

The above-described conventionally known foreign matter inspection apparatus irradiates a laser beam obliquely to the wafer surface, detects scattered light due to unevenness of the foreign matter attached to the wafer surface, and detects the scattered light on the wafer based on the detected data of the scattered light. Is determined, and a pattern other than the pattern is detected as a foreign substance. Next, a portion where the foreign matter is detected is imaged by an imaging device, a foreign image is extracted from image data by the imaging device, and the size and shape of the foreign material are measured based on the extracted foreign image. However, in the above foreign substance inspection apparatus, after the foreign substance inspection, the foreign substance portion is imaged by the imaging apparatus, and the size and shape of the foreign substance are measured based on the extracted foreign substance image extracted from the image data of the imaging apparatus. Since the inspection for the presence or absence of foreign matter on the wafer cannot be performed for the operation time, the throughput is reduced.

[0005]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above points, and provides a foreign substance inspection apparatus and a foreign substance inspection apparatus capable of judging or estimating the size (particle size) of a foreign substance when inspecting a foreign substance on the surface of an inspection object. The aim is to provide a method. It is another object of the present invention to provide a foreign matter inspection apparatus and method capable of determining or estimating the shape of a foreign matter in inspecting foreign matter on the surface of an inspection object.

[0006]

A foreign matter inspection apparatus according to the present invention optically detects the state of the surface of an object to be inspected, and outputs detection data composed of a plurality of pixels, based on the detection data. Foreign matter determination means for determining foreign matter on the surface of the inspection object and outputting foreign matter extraction data, and grouping the foreign matter extraction data into unit regions each having a predetermined number of pixels,
Calculating means for counting the number of pixels regarded as foreign in the group for each group, and estimating the size of foreign matter in a unit area corresponding to the group based on the number of foreign pixels for each group obtained by the calculating means Determination means for performing a determination process of performing the determination. According to this,
Since the size of foreign matter existing in one unit area can be estimated by regarding it as one foreign matter, the size (particle size) of the foreign matter can be estimated with a very simple configuration without performing complicated processing such as pattern recognition. Can be determined or estimated.

The present invention can be constituted not only as the invention of the apparatus as described above, but also as the invention of the method. That is, the foreign matter inspection method according to the present invention optically detects the state of the surface of the object to be inspected and outputs detection data including a plurality of pixels, and determines the foreign matter on the surface of the object to be inspected based on the detection data. Outputting foreign matter extraction data, dividing the foreign matter extraction data into unit regions each having a predetermined number of pixels, and counting the number of pixels regarded as foreign matter in the group for each group; Performing a determination process of estimating the size of a foreign substance in a unit area corresponding to the group based on the number of foreign substance pixels for each group.
Also in the foreign matter inspection method having such a configuration, since the foreign matter existing in one unit area can be regarded as one foreign matter and its size can be estimated, the foreign matter can be estimated without performing complicated processing such as pattern recognition. Can be determined or estimated.

Further, the foreign matter inspection apparatus according to the present invention optically detects the state of the surface of the object to be inspected, and outputs detection data composed of a plurality of pixels, and the surface of the object to be inspected based on the detected data. Foreign matter determining means for determining foreign matter and outputting foreign matter extraction data, and grouping the foreign matter extraction data into unit regions each having a predetermined number of pixels, and for each group, determining the number of pixels regarded as foreign matter within the group. Calculating means for counting; means for calculating the sum of the foreign substance detection levels for each pixel in the unit area of the foreign substance extracted data for each group; correlation between the sum of the foreign substance detection level data and the number of foreign pixel And determining means for estimating the shape of the foreign matter in the unit area corresponding to the group based on the property. According to this, the foreign matter existing in one unit area can be regarded as one foreign matter and its shape can be estimated, and therefore, the foreign matter can be estimated with an extremely simple configuration without performing complicated processing such as pattern recognition. The shape can be determined or estimated.

The present invention can be constituted not only as an invention of the apparatus as described above, but also as an invention of a method. That is, the foreign matter inspection method according to the present invention optically detects the state of the surface of the object to be inspected and outputs detection data including a plurality of pixels, and determines the foreign matter on the surface of the object to be inspected based on the detection data. Outputting foreign matter extraction data, dividing the foreign matter extraction data into unit regions each having a predetermined number of pixels, and counting the number of pixels regarded as foreign matter in the group for each group; Calculating the sum of the foreign substance detection levels for each pixel in each unit area of the foreign substance extraction data for each group, based on the correlation between the sum of the foreign substance detection level data and the number of foreign pixels, Estimating the shape of the foreign matter in the corresponding unit area. Also in the foreign matter inspection method having such a configuration, since the foreign matter present in one unit area can be regarded as one foreign matter and its shape can be estimated, the foreign matter can be estimated without performing complicated processing such as pattern recognition. Can be determined or estimated.

[0010]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view showing a foreign matter inspection apparatus and method according to the present invention. In FIG. 1, a foreign matter inspection apparatus A includes an XY moving mechanism 2 on which a wafer 1 is placed, a light beam irradiation means 3, a drive control means 4, a light receiving optical system 5, a scattered light detection sensor 6, a foreign matter determination sensor, Part 7
, Grouping processing unit 8, memory 9, CPU 10
And As shown in FIG. 1A, the wafer 1 is a patterned wafer having a large number of IC chips 1a on which a circuit pattern is formed, and is fixed on an XY table 2a of an XY moving mechanism 2. The surface of the wafer 1 is obliquely irradiated with a spot-shaped laser beam L from the light beam irradiation unit 3 (for example, a laser beam irradiation unit) at a predetermined low angle. X
The Y moving mechanism 2 causes the laser beam L to scan the entire area of the IC chip 1a by moving the XY table 2a in the X direction and the Y direction by the drive control means 4.
When the surface of the wafer 1 is obliquely irradiated with the laser beam L, scattered light in a dark field is generated from a not-shown attached foreign matter and a circuit pattern on the surface of the wafer 1. More specifically, if there is an attached foreign matter or a circuit pattern on the smooth surface of the wafer 1, the laser light L is irregularly reflected and scattered by the attached foreign matter or the unevenness of the circuit pattern. The scattered light irregularly reflected by the attached foreign matter or the circuit pattern is collected on the scattered light detection sensor 6 by a not-shown condenser lens of the light receiving optical system 5.

The scattered light detection sensor 6 has a large number of pixels (solid-state imaging photoelectric conversion elements) arranged in a line in the scanning direction (Y direction in the illustrated example) of the laser light L. The scattered light is received via the optical system 5, and digital detection data D 1 including a plurality of predetermined pixels (for example, eight pixels) is output to the foreign substance determination unit 7. The foreign matter determination unit 7 determines foreign matter on the wafer 1 based on the detection data D1 from the scattered light detection sensor 6, and outputs foreign matter extraction data D2 to the grouping processing unit 8 for each pixel. That is, the detection data D1 from each pixel of the scattered light detection sensor 6 is compared with the chip data at the same position of the adjacent IC chip 1a previously taken in, and if they do not match, the detection data is replaced with the foreign substance extraction data D
As 2 is output to the grouping processing unit 8 for each pixel. That is, since the circuit pattern is the same for the adjacent chips, the mismatched portion of the detection data D1 corresponds to the foreign matter, and foreign matter extraction data D2 indicating only the foreign matter excluding the circuit pattern is obtained. For example, in the foreign substance extraction data, the level of a pixel not regarded as a foreign substance is “0”, and a pixel regarded as a foreign substance obtains a level corresponding to the detection level of the scattered light. In the grouping processing unit 8, the detected pixel counting unit 8b divides the foreign substance extraction data D2 from the foreign substance determining unit 7 into unit regions each having a predetermined number of pixels (for example, 8 × 8 pixels) (see FIG. 1C). For each group, the number N of detected pixels in the group (six pixels in the example shown in the drawing) is counted as the area of one foreign matter P. The level maximum value detection unit 8a compares the foreign substance detection level (luminance level) of each pixel of the foreign substance extraction data D2 of each group, detects the maximum value M of the foreign substance detection level, and determines the maximum value M. It is regarded as luminance information of one foreign substance P. Figure 1
In the example of (c), the level of each of the six pixels regarded as the foreign matter P is 3,1,5,8,4,2, and the coordinates (4,4)
Is the maximum value M. The grouping processing section 8 is composed of required hardware circuits configured to execute the above-described maximum value detection processing and detection pixel counting processing, executes these processings in real time, and obtains the maximum value M (see FIG. In the example of 1 (c), “8”) and the number N of detected pixels (“6” in the example of FIG. 1C) are stored in the memory 9. The CPU 10 performs a determination process for estimating the size of the foreign matter P in a unit area corresponding to the group based on the number N of detected pixels for each group obtained by the grouping processing unit 8. That is, the CPU 10 fetches the number N of detected pixels from the memory 9, obtains the area S of the foreign matter P by the following equation (1), regards the foreign matter P as one circle as shown in the equation (2), Find r. Note that u is an area corresponding to one pixel. u (area of one pixel) × N (the number of detected pixels) = S (1) S = u × N ≒ πr ² (2) ∴r = √ [(u × N) / π] is calculated. For example, assuming that u = 4 square microns, N = 6 in the case of FIG. 1C, so that r = 2.8 microns is calculated from the above equation (2). Thus, the CPU 1
The result of the determination process estimated based on 0 can be displayed on a display unit (not shown) (for example, a display unit or a printer) by a display method such as a foreign matter map or a histogram. Further, if necessary, the calculation results and inspection conditions (power of laser light L, ND (Neutral Density)
)) The actual particle size of the foreign matter P present on the wafer 1 is obtained using the results of the PLS standard particles (calibration standard particles) whose particle size is known in advance, and a filter and a polarizing plate). Specifically, for various types of PLS standard particles having different particle diameters, data obtained by measuring the reflection intensity by changing the conditions of the power of the laser beam L, the ND filter, the polarizing plate, and the like are stored, and the actual foreign substance inspection is performed. The actual particle size of the foreign matter P is determined by comparing with the calculation result obtained in (1). ND
The filter and the polarizing plate are provided in, for example, the light receiving optical system 5. The ND filter appropriately adjusts the transmittance of the scattered light to appropriately attenuate the scattered light received by the scattered light detection sensor 6, thereby preventing the scattered light detection sensor 6 from being saturated.
The polarizing plate has a predetermined deflection component (for example, S
The scattered light detection sensor 6 is used to cut off a deflection component) and receive another deflection component (for example, a P deflection component).

FIG. 2 shows another embodiment of the foreign matter inspection apparatus and method according to the present invention. Note that the same reference numerals are given to portions common to the above-described foreign substance inspection device, and description thereof will be omitted. As shown in FIG. 2A, the foreign substance inspection apparatus A of this embodiment is provided with a foreign substance level calculation unit 8c in the grouping processing unit 8 instead of the maximum level detection unit 8a. The foreign substance level calculation unit 8c calculates the sum ΣQ of the foreign substance detection levels for each pixel of the foreign substance extraction data D2 for each group. In the example shown in FIG. 1C, the foreign object detection levels of the six pixels regarded as foreign objects P are 3, 1, 5, 8, 4, 2, and the sum "23" of the foreign object detection levels is the total sum. ΣQ
It is. The grouping processing unit 8 is composed of required hardware circuits configured to execute the above-described foreign matter level calculation processing and detection pixel counting processing, and executes these processings in real time, and sums the sum ΣQ (FIG. 1).
(C) In the example, “23”) and the number N of detected pixels (“6” in the example of FIG. 1C) are stored in the memory 9. The CPU 10 performs a determination process for estimating the shape of the foreign matter P in the unit area corresponding to the group based on the correlation between the sum ΣQ of the foreign matter detection levels for each group obtained by the grouping processing unit 8 and the number N of detected pixels. . In the case of the scattered light measurement method, the detection level is higher as the unevenness of the foreign matter in pixel units is larger, and the detection level is lower as the foreign matter is flatter. It is possible to infer to some extent the overall shape of the foreign matter (whether it is lump or flat) from such a tendency of the foreign matter detection level in pixel units. Also, the total level of the foreign object detection levels in the unit area according to the degree of gathering and dispersion of the foreign matter in the pixel unit in the unit area composed of a plurality of pixels or the unevenness or flatness of the foreign objects in the adjacent pixel units. Has a correlation with the number of foreign matter pixels. The CPU 10 uses the foreign matter shape determination table 10a (see FIG. 2B) in which the shape of the foreign matter is set based on the correlation between the total level of the foreign matter detection levels and the number of foreign matter pixels in the scattered light measurement method. Is determined. That is, the CPU 10 fetches the sum ΣQ of the foreign substance detection level data and the number N of detected pixels from the memory 9 and sets the sum ΣQ of the foreign substance detection levels corresponding to the predetermined number N of detected pixels in the foreign substance shape determination table 10a to a predetermined threshold value. If it is smaller than R, it is determined to be a flat foreign substance, and if the sum ΣQ of the foreign substance detection levels is larger than the threshold value R, it is determined to be a blocky foreign substance. The result of the determination process estimated by the CPU 10 can be displayed on a display unit (not shown) (for example, a display unit or a printer) by a display method such as a foreign matter map or a histogram. Note that the characteristics of the foreign matter shape determination table 10a are not limited to this. In addition, the foreign substance level calculation unit 8c calculates the total sum of the foreign substance detection levels. However, the present invention is not limited thereto, and an average value of the foreign substance detection levels may be obtained. In this case, it is possible to estimate or determine the shape of the foreign matter by simply comparing the average value of the foreign matter detection level and the foreign matter detection level obtained from the memory without providing a foreign matter shape determination table.

The foreign substance inspection apparatus A shown in each of the above embodiments
May use IC chip design pattern data or standard pattern data in place of the chip data compared with the detection data D1 of the scattered light detection sensor 6 in the foreign matter determination unit 7. As the scattered light detection sensor 6, an area sensor or an image pickup tube may be used instead of the line sensor. In the above-described embodiment, a wafer with a pattern has been described.

[0014]

As described above, according to the present invention, a foreign substance present in one unit area can be regarded as one foreign substance and its size can be estimated, so that complicated processing such as pattern recognition is performed. Without this, there is an excellent effect that the size (particle size) of the foreign matter can be determined or estimated with a very simple configuration. In addition, since the foreign matter existing in one unit area can be regarded as one foreign matter and its shape can be estimated, the foreign matter shape can be determined with a very simple configuration without performing complicated processing such as pattern recognition. Alternatively, it has an excellent effect of being able to estimate.

[Brief description of the drawings]

FIG. 1 shows an embodiment of a foreign substance inspection apparatus according to the present invention, (a) is a schematic diagram showing a schematic configuration of the foreign substance inspection apparatus of the present example, (b) is a block diagram of a data processing unit of the apparatus,
FIG. 3C is a diagram illustrating an example of foreign matter determination data in a data processing unit.

FIGS. 2A and 2B show another embodiment of the foreign matter inspection apparatus according to the present invention, wherein FIG. 2A is a block diagram of a data processing unit of the foreign matter inspection apparatus of the present embodiment, and FIG. .

[Explanation of symbols]

 Reference Signs List A Foreign matter inspection device 1 Wafer 3 Light beam irradiation means 6 Scattered light detection sensor 7 Foreign matter determination unit 8 Grouping processing unit 8a Level maximum value detection unit 8b Detection pixel counting unit 8c Foreign matter level calculation unit 9 Memory 10 CPU 10a Foreign matter shape determination table

Continued on the front page F term (reference) 2F065 AA54 BB03 CC17 DD06 FF42 GG04 JJ25 LL21 LL31 MM03 MM14 QQ23 QQ42 QQ43 RR08 SS13 2G051 AA51 AA56 AB01 AB02 BA10 BA11 BB05 CA03 CA04 CB01 CB05 DA07 EB05 EB05 BA02 CA02 CA08 CA12 CA16 CB02 CB08 CB12 CB16 CE09 DA03 DA08 DB02 DB05 DB09 DC04 DC09 DC22

Claims (6)

[Claims] 1. The method according to claim 1, wherein the state of the surface of the inspection object is optically detected.
Detecting means for outputting detection data composed of a plurality of pixels; foreign matter determining means for determining foreign matter on the surface of the inspection object based on the detection data and outputting foreign matter extraction data; A calculating unit that divides each unit area into groups and counts, for each group, the number of pixels considered to be foreign in the group; and, based on the number of foreign pixels in each group obtained by the calculating unit, corresponds to the group. A foreign matter inspection device comprising: determination means for performing determination processing for estimating the size of a foreign matter in a unit area. 2. The foreign matter according to claim 1, further comprising means for generating representative foreign matter detection level data in each of the unit areas based on the foreign matter detection level of each pixel of the foreign matter extraction data of each of the groups. Inspection equipment. 3. Optically detecting the state of the surface of the inspection object,
Detecting means for outputting detection data composed of a plurality of pixels; foreign matter determining means for determining foreign matter on the surface of the inspection object based on the detection data and outputting foreign matter extraction data; Calculating means for grouping each unit area and counting the number of pixels regarded as foreign matter in each group for each group; foreign matter detection for each pixel in each unit area of the foreign matter extraction data for each group A foreign matter inspection apparatus comprising: means for calculating a sum of levels; and determination means for estimating a shape of a foreign matter in a unit area corresponding to the group based on a correlation between the sum of the foreign matter detection level data and the number of foreign matter pixels. . 4. A method for optically detecting a state of a surface of an inspection object,
A step of outputting detection data composed of a plurality of pixels; a step of judging a foreign substance on the surface of the inspection object based on the detection data, and a step of outputting foreign substance extraction data; Counting the number of pixels regarded as foreign matter in each group, and estimating the size of foreign matter in a unit area corresponding to the group based on the number of foreign matter pixels in each group. Performing a determination process. 5. The foreign matter inspection according to claim 4, further comprising the step of generating representative foreign matter detection level data in each unit area based on the foreign matter detection level for each pixel of the foreign matter extraction data for each group. Method. 6. Optically detecting the state of the surface of the inspection object,
A step of outputting detection data composed of a plurality of pixels; a step of judging a foreign substance on the surface of the inspection object based on the detection data, and a step of outputting foreign substance extraction data; Counting the number of pixels regarded as foreign matter in the group for each group; and summing up the foreign matter detection level for each pixel in each unit area of the foreign matter extraction data for each group. A foreign matter inspection method, comprising: a calculating step; and a step of estimating a foreign matter shape in a unit area corresponding to the group based on a correlation between the sum of the foreign matter detection level data and the foreign matter pixel number.