JP2002267416A - Surface defect inspecting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect a defect part on the surface of a body to be inspected and to measure the film thickness of the defect part efficiently at the same time. SOLUTION: The defect part G on the surface of the body 1 to be inspected is extracted according to image data on the body 1 to be inspected which are obtained through the image pickup operation of a line sensor camera 6 and previously stored reference image data; and an interference fringe arithmetic part 24 finds pieces Da and Db of theoretical film thickness data on interference fringes formed on a thin film formed on the body 1 to be inspected from information regarding the thin film and a film thickness measurement part 29 measures the film thickness value of the thin film according to the image data of the body 1 to be inspected which are obtained through the image pickup operation of the line sensor camera 6, the pieces Da and Db of theoretical film thickness data on the interference fringes, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface defect inspection apparatus for inspecting defects on a surface of an object having a thin film formed on a surface such as a semiconductor wafer or a liquid crystal glass substrate in a semiconductor manufacturing process.

[0002]

2. Description of the Related Art In a photolithography process for a semiconductor wafer or a liquid crystal glass substrate, for example, if a resist applied to the surface of a semiconductor wafer has a defect such as unevenness in film thickness or adhesion of dust, the portion is etched and patterned. And a defect such as a pin hole in the pattern. Generally, a semiconductor wafer or a liquid crystal glass substrate before etching is subjected to a 100% inspection for the presence or absence of a defective portion.

As such a defect inspection, a method of irradiating a semiconductor wafer or a liquid crystal glass substrate with light by a light projecting device and searching for a defect on the semiconductor wafer or the liquid crystal glass substrate by an operator's eyes is employed. However, recently, there is a surface defect inspection apparatus that performs a defect inspection by performing image processing while imaging a surface of a subject as disclosed in, for example, Japanese Patent Application Laid-Open No. 9-61365.

FIG. 7 is a schematic configuration diagram of an optical system of such a surface defect inspection apparatus. A subject 1 such as a semiconductor wafer or a liquid crystal glass substrate is moved by a uniaxial stage 2
Is placed on top. Above this one-axis stage 2,
The lighting unit 3 is arranged. The illumination unit 3 has a light source for illumination and an optical system thereof. Among them, a lamp house having a halogen lamp, a heat absorption filter and a condenser lens therein is used as the light source, and the optical system is a lamp house. A condensing lens and a fiber bundle for converging a light beam from the light source are used. Illumination light output from the illumination unit 3 is adapted to be applied to the subject 1 at an incident angle theta ₀ through the cylindrical lens 4.

[0005] The interference filter 5 is located at a position facing the illumination unit 3 via the normal line s, that is, at an angle θ ₀ ′ with respect to the normal line s.
And a line sensor camera 6 as an imaging device. An output terminal of the line sensor camera 6 is connected to an image capturing unit 7 that captures an image signal output from the line sensor camera 6 and constructs two-dimensional image data.

[0006] The host computer 8 receives the two-dimensional image data sent from the image capturing unit 7, performs image processing on the two-dimensional image data, and performs processing on the surface of the subject 1 for defects such as film thickness unevenness and dust. And has a function of judging the quality of the subject 1 by comparing the results with a passing criterion included in the test conditions.

[0007] With such a configuration, the illumination light output from the illumination unit 3 is irradiated onto the subject 1 at an incident angle theta ₀ through the cylindrical lens 4. At this time, the subject 1
Is moved in the direction of arrow a, and the line sensor camera 6 captures an image of the illuminated linear region of the subject 1 and outputs an image signal thereof. The image capturing unit 7 captures an image signal output from the line sensor camera 6 in synchronization with the movement of the one-axis stage 2 to construct two-dimensional image data, and sends the two-dimensional image data to the host computer 8. . This host computer 8
Receives the two-dimensional image data sent from the image capturing unit 7, performs image processing on the two-dimensional image data, and
Defective portions such as film thickness unevenness and dust on the surface of the sample 1 are extracted, and from these results, the quality of the subject 1 is determined by comparing it with a passing criterion included in the inspection conditions. In addition, extraction of a defective part
The film thickness unevenness is captured as a luminance value on the image data, and a region exceeding a predetermined threshold is detected as a defect due to the film thickness unevenness.

[0008]

However, in the inspection process, it may be necessary to measure the thickness unevenness. For example, even if a defect portion is detected in a surface defect inspection, if the film thickness unevenness is within a predetermined reference range, it is determined to be a non-defective product and then flown to the next step, or reworked and reproduced. A method may be employed.

Therefore, a method of measuring the film thickness of the subject 1 determined to have a defective portion in the surface defect inspection by using a separate film thickness measuring device is adopted. In this measurement method, a separately prepared film thickness measurement device is expensive and requires a long measurement time, and is not suitable for 100% inspection. For this reason, 100% inspection is performed by a surface defect inspection device, and there is a defective portion. A method is adopted in which only the subject 1 determined to be is extracted and the film thickness is measured by a separately prepared film thickness measuring device.

However, since the surface defect inspection device and the film thickness measuring device are separately disposed, the defect position information of the subject 1 in the surface defect inspection device can be accurately determined with respect to the film thickness measuring device. , A positioning mechanism and a position correcting mechanism are required, and the configuration of each device becomes complicated and expensive.

Further, since the surface defect inspection device and the film thickness measuring device are separate components, a cassette for accommodating the subject 1 for each device or each device, or a device for inspecting the subject 1 with the surface defect inspection device and the film thickness measuring device An installation space for a transfer robot or the like for transferring between the apparatus is required. For this reason, these surface defect inspection device and film thickness measurement device are installed in a clean room,
The demand for space saving cannot be satisfied for a clean room in which facility cost is high and space saving is important.

Further, since the test object 1 needs to be transported between the surface defect inspection apparatus and the film thickness measurement apparatus, not only does the entire defect inspection require a great amount of time, but also the movement of the operator between the apparatuses. Is required. For this reason, the fatigue of the worker is caused, and the efficiency of the inspection work is reduced.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a surface defect inspection apparatus capable of detecting a defective portion on the surface of an object and simultaneously efficiently measuring the thickness of the defective portion.

[0014]

The present invention according to claim 1 captures an image of the surface of a subject having a thin film formed on the surface when the subject is irradiated with illumination light. In a surface defect inspection apparatus that performs image processing on image data of a predetermined wavelength band to perform a defect inspection on the surface of an object, interference fringes that obtain theoretical data of interference fringes generated by the thin film based on information about the thin film Calculation means, and defect extraction means for extracting a defect portion on the surface of the subject based on the image data and the reference image data,
A surface defect inspection apparatus, comprising: a film thickness measuring unit that measures a film thickness value of the thin film based on the image data obtained by the imaging and the theoretical data of the interference fringes. .

According to a second aspect of the present invention, in the surface defect inspection apparatus according to the first aspect, the interference fringe calculating means, when the wavelength band is selectively changed, adjusts the interference fringe according to the wavelength band. It is characterized by having a function of obtaining the theoretical data.

According to a third aspect of the present invention, in the surface defect inspection apparatus according to the first aspect, the interference fringe calculating means includes at least a material, a refractive index, a film thickness, a reflectance, and a wavelength of the illumination light of the thin film. A function of calculating a repetition pattern of a bright line and a dark line of the interference fringes based on the above formula, and obtaining film thickness data with respect to a luminance value of an image.

According to a fourth aspect of the present invention, in the surface defect inspection apparatus according to the first aspect, the defect extracting means comprises:
An image of the surface of the object including the defect portion is displayed on a display device, and the film thickness measuring means has a function of outputting the film thickness value of a portion designated on a screen of the display device. Features.

According to a fifth aspect of the present invention, in the surface defect inspection apparatus according to the third aspect, the film thickness measuring means comprises:
It has a function of outputting a profile of the film thickness value of the defective portion specified in a line on the screen of the display device.

According to a sixth aspect of the present invention, in the surface defect inspection apparatus according to the third aspect, the film thickness measuring means comprises:
It has a function of outputting a film thickness difference between two points designated in a line on the screen of the display device.

According to a seventh aspect of the present invention, in the surface defect inspection apparatus according to the third aspect, the film thickness measuring means comprises:
It has a function of outputting the film thickness value in a region designated on the screen of the display device.

The present invention according to claim 8 is a surface defect inspection apparatus according to claim 3, wherein the film thickness measuring means comprises:
It has a function of outputting at least a maximum value, a minimum value, or an average value of the film thickness values in a region specified on a screen of the display device.

According to a ninth aspect of the present invention, in the surface defect inspection apparatus according to the first aspect, the film thickness measuring means includes:
It has a function of obtaining a frequency distribution of the film thickness value on the surface of the subject.

The present invention according to claim 10 provides the present invention according to claim 1.
In the surface defect inspection device according to the above, the image data,
First image data obtained by imaging a light beam having a wide wavelength width and a short coherence length with respect to the thickness of the thin film formed on the surface of the subject and a wavelength width with respect to the thickness of the thin film The image processing apparatus is characterized in that arithmetic processing is performed between the image data and a second image data obtained by imaging a light beam having a narrow coherence length and the coherence length is long, and the light flux is generated as a result of removing the influence of the background of the subject.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (1) Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. The same parts as those in FIG. 7 are denoted by the same reference numerals, and detailed description thereof will be omitted.

FIG. 1 is a block diagram of a surface defect inspection apparatus.
A cylindrical lens 4 and a slit 10 are arranged between the illumination unit 3 and the subject 1 on the uniaxial stage 2. In addition, the one-axis stage 2 is configured to move by one axis in a direction indicated by an arrow A by driving of the stage driving unit 11.

At a position facing the lighting unit 3 via the normal line s,
The filter unit 12 and the line sensor camera 6 are arranged. The filter unit 12 includes a plurality of narrow band filters for obtaining an interference image by limiting a wavelength band of the illumination light. The filter unit 12 is disposed in front of the line sensor camera 6 and controls the plurality of narrow band filters to a filter driving unit. 13 is inserted into and removed from the optical path by driving, and a narrow band filter having a wavelength band necessary for thin film measurement is arranged on the optical path.

The one-axis stage 2, the illuminating unit 3, the cylindrical lens 4, the slit 10, the line sensor camera 6, the filter unit 12 (hereinafter referred to as an image pickup unit) are not affected by disturbance light. Is accommodated in a dark box-shaped housing (not shown), and a downflow flows from above through an air cleaning filter in order to prevent particles from adhering to the subject 1.

On the other hand, the main controller 20 is provided with an image capturing section 7. The image capturing unit 7 captures image signals output from the line sensor camera 6 in synchronization with the movement of the one-axis stage 2, connects the image data of each line, and converts the two-dimensional image data of the subject 1. It has a function of constructing and transmitting this two-dimensional image data to the image storage unit 21.

The image storage section 21 has a storage capacity for storing a plurality of image data, and can read and write arbitrary image data. The image storage unit 21 also stores reference image data (reference image data) previously captured as non-defective products of the subject 1.

The thin film parameter input section 22 is used for inputting information on the subject 1 by a key operation of a keyboard 23 connected to the main controller 20, for example, a process name,
It has a function of sending, for example, a material, a refractive index, a film thickness, a reflectivity, and the like to the interference fringe calculation unit 24 as information on a product type, external dimensions, and a thin film formed on the surface of the subject 1.

The interference fringe calculation unit 24 generates an interference fringe generated by the thin film based on information about the thin film (eg, material, refractive index, film thickness, reflectance, etc.), that is, light reflected on the surface of the thin film on the subject 1. The theoretical data of interference fringes generated by the light reflected on the main body surface of the subject 1 is obtained.
Specifically, based on the material of the thin film, the refractive index, the film thickness, the reflectance, and the wavelength of the illuminating light, a repetitive pattern of bright lines and dark lines of interference fringes appearing when illuminating with the illuminating light is calculated.
Has a function of obtaining theoretical film thickness data Da with respect to the luminance value of the image as shown in FIG.

That is, the interference fringe calculation unit 24 calculates, for example, the refractive index n, the film thickness h, and the wavelength of the illumination light λ ₀ , among the information on the thin film input from the thin film parameter input unit 22.
Assuming that the refractive index of the light beam inside the thin film is θ ′ and the phase change at the time of reflection on the lower surface of the thin film is φ (0 ≦ φ ≦ 2π), the condition that the interference fringes by the thin film become clear (strengthen by interference) is as follows. 2nh · cos θ ′ + (φ / 2π) · λ ₀ = m · λ ₀ (m = 0, ± 1, ± 2,...) (1)

Accordingly, FIG. 2 shows the correspondence between the change in film thickness and the luminance value of image data based on the equation (1). As shown in FIG.
It changes periodically with the film thickness.

The interference fringe calculating section 24 selectively changes a narrow band filter of a wavelength band necessary for thin film measurement among a plurality of narrow band filters of the filter section 12 and inserts the narrow band filter into an optical path. It has a function of obtaining theoretical film thickness data Db of interference fringes according to the band. That is, as shown in FIG. 2, the brightness value such as the film thickness data Da changes periodically with respect to the film thickness, so that the range applicable to the film thickness measurement is limited. To measure the thickness, a straight line portion in the theoretical film thickness data Da or the like can be used to accurately determine the film thickness value. For example, in order to measure the film thickness t, the use of the film thickness data Da implies a curved portion and cannot be measured with high accuracy. However, if the film thickness data Db is used, highly accurate measurement can be performed using the linear portion of the film thickness data Db. Becomes possible.

The film thickness data Da and Db obtained by the interference fringe calculation section 24 are stored in an interference data storage section 26.

Information on the thin film (eg, material, refractive index, film thickness, reflectance, etc.) is also sent to the drive control unit 25 at the same time to set the wavelength band of the filter unit 12 and the angle of the illumination unit 3. ing.

The image processing section 27 reads out the image data of the subject 1 and the reference image data stored in the image storage section 21, compares the image data of the subject 1 with the reference image data, and Is detected and sent to the defect extraction unit 28.

The image processing section 27 reads out the image data of the subject 1 stored in the image storage section 21 and, among the plurality of thickness data Da, Db, etc. stored in the interference data storage section 26. For example, Db necessary for the film thickness measurement is read out, the brightness value of the image data of the subject 1 is correlated with the film thickness data Db, and image data whose brightness value indicates the film thickness is generated. Has the function of sending to

The defect extracting unit 28 receives the difference between the image data of the subject 1 detected by the image processing unit 27 and the reference image data, and extracts the subject 1 from the difference image data.
A function of extracting a defective portion on the surface of the object 1, acquiring defect information (for example, position, defect type) such as film unevenness on the surface of the subject 1, storing the information in the storage unit 30, and displaying the information on the display 31. Have.

The film thickness measuring section 29 receives the image data whose luminance value indicates the film thickness generated by the image processing section 27,
It has a function of measuring the film thickness from the image data, storing the result in the storage unit 30, and displaying the result on the display unit 31.

The actual display on the display 31 is performed by the following functions, for example, as shown in FIG.

The defect extracting section 28 reads out image data including a defective portion G specified by an operator, for example, from among the defective portions on the surface of the subject 1 extracted from the difference image data, and converts the image to a first image. It has a function of displaying in _one display area H1.

The thickness measuring unit 29, the image including the defective portion G which is displayed in the first display area H _1, when it is specified in a line shape by the operator at the screen, is the line designated the profile of film thickness values including the defective portion G has has a function of displaying on the second display region H _2.

Further, the film thickness measurement unit 29 is
Two points, for example, point a
When point b is specified by the operator, the coordinates of these two points
Point a (X₁, Y₁) And point b (X₂, Y₂) And based on
Each film thickness value D₁And D ₂Between these two points
(Point a−point b) film thickness difference ΔD = D₂-D₁Display in search of
It has a function of displaying on the display 31.

Further, the film thickness measuring section 29 is provided in the first display area H.
_{When an} operator designates one point on the image including the defective portion G displayed on the screen 1, the thickness value of the point is determined based on the coordinates of the point, and the storage unit 30 determines the film thickness value. And has a function of displaying the information on the display 31.

Further, the film thickness measuring section 29 is provided in the first display area H.
The image including the defective portion G displayed on the _1, when a desired region by workers at the screen is designated, and stores the film thickness value in the area in the storage unit 30, and indicator 31
Has the function of displaying the information.

Further, the film thickness measuring section 29 is provided in the first display area H
_{When an} operator designates a desired area on the screen including the defective portion G displayed in ₁ , at least the maximum value, the minimum value, or the average value of the film thickness values in the area is obtained. , The maximum value, the minimum value, or the average value,
And has a function of displaying the information on the display 31.

Further, the film thickness measuring section 29 is provided in the first display area H.
The image including the defective portion G displayed on the _1, the desired area is designated by the operator at the screen, function to determine the frequency distribution of the film thickness value of the subject 1 on the surface in that region have.

The drive control unit 25 sets the angle of the illumination unit 3 to operate the image pickup unit while transmitting information to and from the image processing unit 27, and sets the filter drive unit 13, the stage drive unit 11, the sample It has a function of controlling the operation of the orientation unit 33 and the sample transport unit 34.

The filter driving section 13 controls the filter section 12 based on the information on the thin film of the subject 1, and
It has a function of selecting and changing a narrow band filter of a wavelength band necessary for thin film measurement from the plurality of narrow band filters and inserting the narrow band filter into the optical path.

The stage driving section 11 has a function of driving the one-axis stage 2 in the direction of arrow A in order to capture an image of the subject 1.

The sample transport section 34 drives and controls a sample transport robot and the like, takes out the subject 1 from the cassette, and aligns the orientation of the orientation flat or notch of the subject 1 in a fixed direction by the sample direction aligning section 33. Axis stage 2
The robot has a function of controlling the drive of a sample transport robot or the like to take out the subject 1 whose inspection has been completed, remove it from the one-axis stage 2, and transport it to a cassette.

Next, the operation of the device configured as described above will be described.

By the operation of the keyboard 23 by the operator, information on the subject 1 from the keyboard 23, such as a process name, a kind name, an outer dimension, and information on a thin film formed on the surface of the subject 1, such as a material, A refractive index, a film thickness, a reflectance, and the like are input. Of these, the process name,
Information such as the product name and external dimensions are sent to the interference fringe calculation unit 24 through the thin film parameter input unit 22 or used as the drive conditions by the drive control unit 25 in order to be used when the test results are stored as test conditions. Sent.

Information on the thin film includes, for example, material,
Information such as the refractive index, the film thickness, and the reflectance is obtained from the interference fringe calculation unit 24.
Is used to calculate and determine the interference fringes of the thin film, and is sent to the drive control unit 25 to set the wavelength band of the filter unit 12 and the angle of the illumination unit 3.

When the input of the information on the subject 1 is completed, the cassette in which the subject 1 is stored is set in the sample transport section 34 by an operator or a production line (not shown). When the operator operates the operation input unit 32 to instruct the start of the test, or when the start of the test is instructed from the production line via a communication system (not shown), the sample transport unit 34 1 is taken out one by one and transported to the uniaxial stage 2. Thereby, the subject 1
Is started.

Subject 1 transported by sample transport section 34
Are positioned in a fixed direction by the sample direction aligning unit 33 and mounted on the uniaxial stage 2.

Next, the drive control unit 25 includes an image processing unit 27
The angle of the illumination unit 3 is set in order to operate the imaging unit while transmitting information between the imaging unit 1 and the filter driving unit 13 and the stage driving unit 11, and the imaging of the subject 1 is started. At this time, the filter driving unit 13 controls the filter unit 12 based on information on the thin film of the subject 1 and selectively changes a narrow band filter having a wavelength band optimal for thin film measurement among a plurality of narrow band filters of the filter unit 12. And insert it on the optical path. The stage driving unit 11 drives the one-axis stage 2 in the direction of arrow A to capture an image of the subject 1.

However, the illuminating light output from the illuminating unit 3 is applied to the subject 1 at an incident angle θ ₀ through the cylindrical lens 4 and the slit 10. At this time, an interference fringe is generated by the light reflected on the thin film surface on the subject 1 and the light reflected on the main body surface of the subject 1, and the line sensor camera 6 repeats the bright line and the dark line of the interference fringe. Image the pattern.

Then, the one-axis stage 2 on which the subject 1 is mounted moves in the direction of arrow A, so that the line sensor camera 6
Filters the illuminated linear region of the subject 1 with the filter unit 1
2, the imaging light of the interference fringes is imaged, the imaging light is converted into an image signal which is an electric signal, and is transferred to the image capturing unit 7 of the main controller 20 line by line. As a result, the line sensor camera 6 finally outputs an image signal of interference fringes obtained by imaging the entire region of the subject 1.

The image capturing section 7 captures the image signal output from the line sensor camera 6 in synchronization with the movement of the one-axis stage 2 to construct two-dimensional image data, and stores the two-dimensional image data in the image storage section. 21.

The image processing unit 27 reads out the image data of the subject 1 stored in the image storage unit 21 and the reference image data stored in advance, and compares the image data of the subject 1 with the reference image data. Then, the difference image data is detected and sent to the defect extraction unit 28.

The defect extracting section 28 receives difference image data between the image data of the subject 1 detected by the image processing section 27 and the reference image data, and obtains a defect portion on the surface of the subject 1 from the difference image data. Is extracted and the subject 1
Defect information (eg, position, defect type) such as film unevenness on the surface of the device is acquired and stored in the storage unit 30.

At the same time, the defect extracting unit 28
Defects on the surface of the subject 1 extracted from the data
Includes a defective portion G specified by an operator, for example.
The image data is read out and the image is displayed as shown in FIG.
First display area H of indicator 31 ₁To be displayed.

On the other hand, the interference fringe calculation unit 24 receives information (for example, material,
(Refractive index, film thickness, reflectivity, etc.), and the light and dark lines of the interference fringes that appear when illuminating with illumination light based on the material, refractive index, film thickness, reflectance, and wavelength of the illumination light. The repetition pattern is calculated, and theoretical film thickness data Da for the brightness value of the image whose brightness value periodically changes with the film thickness is obtained as shown in FIG.

The interference fringe calculation unit 24 selects a plurality of narrow band filters of a wavelength band necessary for thin film measurement from among a plurality of narrow band filters of the filter unit 12 and inserts them on the optical path. A plurality of theoretical film thickness data of interference fringes corresponding to the wavelength band, for example, film thickness data Db is obtained. The film thickness data Da, Db, and the like are stored in the interference data storage unit 26.

The image processing section 27 reads out the image data of the subject 1 stored in the image storage section 21 and stores a plurality of film thickness data D stored in the interference data storage section 26.
a, Db and the like, for example, read out the film thickness data Db,
The luminance value of the image data of the subject 1 and the film thickness data Db
And generates image data whose luminance value indicates the film thickness, and sends it to the film thickness measuring section 29.

The film thickness measuring section 29 receives the image data whose luminance value indicates the film thickness generated by the image processing section 27, measures the film thickness from this image data, and stores the result in the storage section 30. And a function of displaying on the display 31. The actual display on the display 31 is performed in various ways, for example, as shown in FIG. 3 (to FIG. 6).

As a first display function, a first display area H
_{When a} line is designated by an operator on the image including the defective portion G displayed in ₁ , the film thickness measuring section 29 reads the coordinates of the line and reads the line-designated defective portion G. displaying the profile of film thickness value in the second display area H ₂ containing. The profile of this film thickness value is
The luminance value corresponding to the defective portion G is at a high level.

Further, the profile of the film thickness value designated by the line is
Two points, e.g., point a and point b, are
Is specified, the film thickness measuring section 29 calculates the coordinates of these two points.
Point a (X₁, Y₁) And point b (X₂, Y₂) And based on
Each film thickness value D₁And D ₂Between these two points
(Point a−point b) film thickness difference ΔD = D₂-D₁Display in search of
Is displayed on the display 31. At this time, the right side on the screen of the display 31
Contains, for example, the coordinates of point a (X₁= 1024, Y₁= 512) and
The film thickness 50, the coordinates of point b (X₁= 1200, Y ₁= 30
0) and its film thickness value 89, film thickness difference ΔD = D₂-D₁= 29
Is displayed.

As a second display function, as shown in FIG. 4, for an image including a defective portion G displayed in the _first display area H1, one point Q is designated by an operator on the screen. Then, the film thickness measuring section 29 calculates the coordinates (X _Q ,
Based on Y _Q ), a film thickness value D _Q at that point Q is obtained, stored in the storage unit 30, and displayed on the display 31.

As a third display function, as shown in FIG. 5, for an image including a defective portion G displayed in the _first display area H1, a desired area W measured by an operator on the screen is displayed. Is instructed, the film thickness measuring section 29
At least the maximum value Dmax, the minimum value Dmin and the average value Dav of the film thickness values are obtained, and the maximum value Dmax, the minimum value Dmin and the average value Dav are stored in the storage unit 30 and displayed on the display 31.

Here, the area W designated by the worker is
Although FIG. 5 shows a quadrilateral, the shape is not limited to the quadrilateral but may be specified by a circle, an ellipse, or an arbitrary closed curve.

As a fourth display function, as shown in FIG. 6, an operator specifies a desired area W on an image including a defective portion G displayed in the _first display area H1 on the screen. Then, the film thickness measuring unit 29 obtains a frequency distribution of the film thickness value on the surface of the subject 1 in the region W, stores the frequency distribution in the storage unit 30, and displays the frequency distribution on the display unit 31.

As described above, in the first embodiment, based on the image data of the subject 1 obtained by the imaging by the line sensor camera 6 and the reference image data stored in advance, the surface of the subject 1 And a plurality of theoretical data Da and Db of interference fringes generated by the thin film are obtained by the interference fringe calculation unit 24 based on information on the thin film formed on the subject 1 by the interference fringe calculation unit 24. Since the thickness of the thin film is measured by the thickness measuring unit 29 based on the image data of the subject 1 obtained by the imaging of the line sensor camera 6 and the theoretical thickness data Da and Db of the interference fringes, the subject is measured. In addition to detecting the defective portion G on the surface of No. 1, the thickness value of the defective portion G can be simply and simultaneously efficiently measured.

In particular, as a method of displaying the film thickness value, for example, a film thickness difference ΔD = D ₂ −D ₁ between two points (point a−point b) specified by an operator on the screen of the display 31, or The film thickness value D _{Q at} one point Q specified by the worker, the maximum value Dmax, the minimum value Dmin, and the average value Dav of the film thickness values in the region W specified by the worker, and the region W specified by the worker. The frequency distribution of the film thickness values inside can be displayed.

As another example of the display method of the film thickness value, an image in which the luminance value generated by the image processing unit 27 indicates the film thickness may be displayed on the display 31 as it is. In this case, since the brightness value of the image directly indicates the film thickness value, a line profile or the like can be displayed by general-purpose image analysis software, and together with the various display methods described above, the thin film formed on the surface of the subject 1 can be displayed. The width of the film thickness analysis can be expanded.

Therefore, according to the apparatus of the first embodiment, it is possible to measure the film thickness unevenness by adding a small-scale configuration to the configuration of the conventional apparatus, and it is possible to efficiently perform the defect inspection. .

(2) Next, a second embodiment of the present invention will be described. Note that the second embodiment has almost the same configuration as the first embodiment, and therefore, different points will be described with reference to FIG.

The first image data of the subject 1 is irradiated by irradiating the subject 1 with illumination light of a light beam having a wide wavelength width and a short coherence length with respect to the thickness of the thin film formed on the surface of the subject 1. Ia is obtained, and then the illumination light of a light flux having a narrow wavelength width and a long coherence length with respect to the thickness of the thin film formed on the surface of the subject 1 2 image data Ib, and these image data Ia, Ib
Between

(Equation 1)

It is known that by calculating the above, it is possible to generate image data Ic in which the influence of the pattern formed on the base of the subject 1, for example, the surface of the semiconductor wafer is eliminated.

Therefore, in the configuration of the apparatus shown in FIG. 1, the configuration of the filter unit 12 is changed,
2 to image a light beam having a wide wavelength width and a short coherence length with respect to the thickness of the thin film formed on the surface of the subject 1 and
A first interference filter for acquiring the image data Ia of the first and second images by imaging a light beam having a narrow wavelength width and a long coherence length with respect to the thickness of the thin film formed on the surface of the subject 1.
Are provided with a plurality of pairs with a second interference filter for acquiring the image data Ib.

In such a configuration, when the illumination light is output from the illumination unit 3, the illumination light passes through the cylindrical lens 4 and the slit 10 at an incident angle θ ₀ ,
Irradiation. At this time, the one-axis stage 2 on which the subject 1 is mounted moves in the direction of arrow A, so that the line sensor camera 6 uses the illuminated linear region of the subject 1 as the first interference filter of the filter unit 12. Through which the imaging light is imaged, and the imaging light is converted into an image signal, which is an electric signal.
The data is transferred to the image capturing unit 7 of the main controller 20 line by line. Thus, the first image data Ia is acquired by the image capturing unit 7 and stored in the image storage unit 21.

Next, the filter section 12 is replaced with a second interference filter. At this time, similarly to the above, the line sensor camera 6 converts the illuminated linear region of the subject 1 into the second section of the filter section 12. The imaging light is imaged through the interference filter, and the imaging light is converted into an image signal, which is an electric signal, and transferred to the image capturing unit 7 of the main controller 20 line by line. Thereby, the second image data Ib is obtained by the image capturing unit 7.

Next, the image capturing unit 27 calculates the above equation (2) between the first and second image data Ia and Ib, thereby forming the image on the base of the subject 1, for example, on the surface of a semiconductor wafer. The image data Ic in which the influence of the formed pattern is eliminated is generated. Then, the image capturing unit 27 outputs the image data Ic
And difference image data between the reference image data.

Hereinafter, as in the first embodiment, the defect extracting unit 28 extracts a defective portion on the surface of the subject 1 from the difference image data between the image data Ic and the reference image data, and Defect information (for example, position, defect type) such as film unevenness on the surface of the first device 1 is obtained, and an image including a defective portion G specified by, for example, an operator is displayed on the first display 31 as shown in FIG. It is displayed on the display area _{H 1.}

The image processing section 27 reads out the image data of the subject 1 stored in the image storage section 21 and includes a plurality of pieces of film thickness data Da, Db and the like stored in the interference data storage section 26. For example, the film thickness data Db is read out, the brightness value of the image data of the subject 1 is correlated with the film thickness data Db, and image data whose brightness value indicates the film thickness is generated and transmitted to the film thickness measuring unit 29. .

The film thickness measuring section 29 measures the film thickness from the image data, stores the result in the storage section 30 and displays the result on the display 31. For example, an operator gives an instruction on the screen of the display 31. Thickness difference ΔD = D ₂ −D ₁ between the two points (point a−b), or the film thickness value D _{Q at} one point Q specified by the worker, within the area W specified by the worker. , The maximum value Dmax, the minimum value Dmin, and the average value Dav of the film thickness values, and the frequency distribution of the film thickness values in the region W specified by the operator.

As described above, in the second embodiment, the illumination light of a light beam having a wide wavelength width and a short coherence length with respect to the thickness of the thin film formed on the surface of the subject 1 is applied to the subject 1. Irradiation obtains the first image data Ia of the subject 1, and then irradiates illumination light of a light beam having a narrow wavelength width and a long coherence length with respect to the thickness of the thin film formed on the surface of the subject 1. By irradiating the subject 1 to obtain second image data Ib of the subject 1 and calculating the above equation (2) between the image data Ia and Ib, a base of the subject 1 such as a semiconductor Since the image data Ic in which the influence of the pattern formed on the wafer surface is eliminated is generated, it is possible to separate the reflectance distribution of the underlying pattern from the image of the subject 1 and to detect not only the film thickness unevenness but also , For example, a semiconductor Effect of the pattern formed on the wafer surface can be erased, it is possible to further efficiently perform defect inspection as compared with the first embodiment.

The present invention is not limited to the above-described first and second embodiments, and can be variously modified in the implementation stage without departing from the gist of the invention.

Further, the above embodiments include inventions at various stages, and various inventions can be extracted by appropriately combining a plurality of disclosed constituent features. For example, even if some components are deleted from all the components shown in the embodiment, the problem described in the column of the problem to be solved by the invention can be solved, and the problem described in the column of the effect of the invention can be solved. In the case where the effect is obtained, a configuration from which this configuration requirement is deleted can be extracted as an invention.

For example, in the first and second embodiments, the filter unit 12 is disposed in front of the line sensor camera 6, but this filter unit 12 is disposed behind the illumination unit 3. You may.

[0093]

As described above in detail, according to the present invention, it is possible to provide a surface defect inspection apparatus capable of detecting a defective portion on the surface of an object and measuring the thickness of the defective portion simultaneously and efficiently.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a first embodiment of a surface defect inspection apparatus according to the present invention.

FIG. 2 is a view showing theoretical film thickness data with respect to a luminance value of an image in the first embodiment of the surface defect inspection apparatus according to the present invention.

FIG. 3 is a diagram showing a display of an actual defect portion and a film thickness on a display in the first embodiment of the surface defect inspection apparatus according to the present invention.

FIG. 4 is a diagram showing a display of a film thickness value at one point in the first embodiment of the surface defect inspection apparatus according to the present invention.

FIG. 5 is a diagram showing a display of a maximum value, a minimum value, and an average value of film thickness values in a region in the first embodiment of the surface defect inspection apparatus according to the present invention.

FIG. 6 is a diagram showing a display of a frequency distribution of film thickness values in a region in the first embodiment of the surface defect inspection apparatus according to the present invention.

FIG. 7 is a schematic configuration diagram of an optical system of a conventional surface defect inspection device.

[Explanation of symbols]

 1: Subject 2: 1-axis stage 3: Illumination unit 4: Cylindrical lens 6: Line sensor camera 7: Image capture unit 10: Slit 11: Stage drive unit 12: Filter unit 13: Filter drive unit 20: Main controller 21 : Image storage unit 22: Thin film parameter input unit 23: Keyboard 24: Interference fringe calculation unit 25: Drive control unit 26: Interference data storage unit 27: Image processing unit 28: Defect extraction unit 29: Film thickness measurement unit 30: Storage unit 31: Display 32: Operation input unit 33: Sample direction adjusting unit 34: Sample transport unit

Of the front page Continued (51) Int.Cl. ⁷ identification mark FI theme Court Bu (Reference) H01L 21/66 H01L 21/30 502V F-term (reference) 2F065 AA30 BB01 BB17 CC19 FF04 FF51 GG02 HH04 HH12 JJ02 JJ08 JJ25 LL08 LL21 MM03 QQ31 QQ42 QQ43 RR06 RR08 UU05 2G051 AA51 AB07 BA08 CA03 CB01 CC07 DA06 EB01 ED03 ED08 2H088 FA11 FA30 HA01 MA20 4M106 AA01 CA38 CA48 DB04 DH03 DH31 DJ11 DJ23 5B057 AA03 BA02 DC15 DC23 DC02

Claims (10)

[Claims] 1. An image of the surface of a subject when a subject having a thin film formed thereon is irradiated with illumination light, and image processing is performed on image data of a predetermined wavelength band obtained by the imaging. In a surface defect inspection apparatus for performing a defect inspection on a surface of an object, an interference fringe calculation unit that obtains theoretical data of an interference fringe generated by the thin film based on the information about the thin film; and the image data and the reference image data. A defect extracting means for extracting a defective portion on the surface of the subject based on the image data; and a film for measuring a film thickness value of the thin film based on the image data obtained by the imaging and the theoretical data of the interference fringes. A surface defect inspection device comprising: a thickness measuring unit. 2. The apparatus according to claim 1, wherein said interference fringe calculating means has a function of obtaining theoretical data of said interference fringes according to said wavelength bands when said wavelength bands are selectively changed. The surface defect inspection device according to the above. 3. The interference fringe calculating means calculates a repetitive pattern of bright lines and dark lines of the interference fringes based on at least a material, a refractive index, a film thickness, a reflectance, and a wavelength of the illumination light of the thin film. 2. The surface defect inspection apparatus according to claim 1, further comprising a function of obtaining film thickness data with respect to an image brightness value. 4. The apparatus according to claim 1, wherein the defect extracting unit displays an image of the surface of the object including the defective portion on a display device, and the film thickness measuring unit displays the image of a portion designated on a screen of the display device. 2. The surface defect inspection apparatus according to claim 1, further comprising a function of outputting a film thickness value. 5. The apparatus according to claim 3, wherein the film thickness measuring means has a function of outputting a profile of the film thickness value of the defective portion specified in a line on the screen of the display device. Surface defect inspection equipment. 6. The surface defect according to claim 3, wherein said film thickness measuring means has a function of outputting a film thickness difference between two points designated in a line on the screen of said display device. Inspection equipment. 7. The surface defect inspection apparatus according to claim 3, wherein the film thickness measuring means has a function of outputting the film thickness value in a region designated on a screen of the display device. 8. The film thickness measuring means has a function of outputting at least a maximum value, a minimum value, or an average value of the film thickness values in an area designated on a screen of the display device. The surface defect inspection apparatus according to claim 3. 9. The surface defect inspection apparatus according to claim 1, wherein the film thickness measuring means has a function of obtaining a frequency distribution of the film thickness value on the surface of the object. 10. The image data includes first image data obtained by imaging a light beam having a wide wavelength width and a short coherence length with respect to the thickness of the thin film formed on the surface of the subject. Assuming that the influence of the background of the subject has been removed by performing arithmetic processing between the thin film and the second image data obtained by imaging a light beam having a narrow wavelength width and a long coherence length with respect to the thickness of the thin film. The surface defect inspection apparatus according to claim 1, wherein the inspection apparatus generates the defect.