JPH01191046A - Foreign matter inspecting device - Google Patents

Abstract

PURPOSE:To determine foreign matter contents and to perform foreign matter reduction control by providing an exciting light irradiating means for foreign matter, switching it with a light beam for abnormal foreign matter inspection and using one of them, and selecting the separation wavelength characteristic of a dichroic mirror. CONSTITUTION:A detection system for the position, shape, etc., of the foreign matter and a top lighting type fluorescent microscope system are switched by a switching mechanism 19, which consists of a linear moving table moving an exciting light generation light source 11, an excitation filter 13, and the dichroic mirror 14 forth and back horizontally in one body while mounting them; and exciting light obtained from the light source 11 is excluded from the path R of reflected light in its backward movement state and put in the path R in the forward movement state. Thus, the exciting light irradiating means for the foreign matter is provided and used while switched with the light beam for normal foreign matter inspection, and the separation wavelength characteristics of the dichroic mirror are selected to determine the foreign matter contents.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] This invention relates to a foreign matter inspection device that detects foreign matter on the surface of a semiconductor wafer or the like. The present invention relates to a foreign matter inspection device that can detect the amount, size, position, etc. of foreign matter, and can also inspect the white base of foreign matter using a fluorescence microscope.

[Prior Art] A foreign object inspection device for LSI wafers is a device that irradiates a light beam onto the wafer surface, receives reflected light from the wafer surface with a light receiving element, converts it into an electrical signal, and detects the wafer surface based on this electrical signal. There is a method that determines the presence or absence of foreign objects in the air.

In this case, a photodiode array, image sensor, photomultiplier, etc. is used as the light receiving element, and the signal level of the reflected light is detected, and the particle size of the foreign object, the location of the foreign object, etc. are determined from the output signal level. ing.

On the other hand, in the fields of biology and medicine, fluorescence microscopes are used to observe the surfaces of minute specimens.

[Problem to be Solved] A surface inspection device for a wafer or the like can detect the size of a foreign object, the position of the foreign object on a wafer, etc., but only estimates the content of the foreign object.

However, foreign substances generated during the semiconductor manufacturing process include resist remaining on wafers and organic flakes generated during the semiconductor manufacturing process. , fiber dust from clothes that accompany people, and organic dust such as fine particles from cosmetics are also often seen.

On the other hand, among the causes of LSI defects, many appearance defects are caused by adhesion of foreign particles, and this is a cause of lower yield. Therefore, among various foreign substances, if it is possible to distinguish between organic dust generated from the human body or accompanying the human body, and foreign substances generated from the semiconductor manufacturing process itself,
The source of contamination can be found, dust can be reduced, and wafers can be processed accordingly after inspecting for foreign substances.

Therefore, the yield can be improved and it is also useful for setting cleaner semiconductor manufacturing conditions.

However, at present, it is not possible to adequately distinguish between the former and the latter.

The present invention was made in view of the problems of the prior art, and it is an object of the present invention to provide a foreign matter inspection device that can efficiently determine the content of foreign matter.

[Means for Solving the Problems] In order to achieve such an object, a foreign matter inspection apparatus according to the present invention includes a light beam irradiation means for irradiating a light beam onto the surface of an object to be inspected, and a light emitting means for generating excitation light. a dichroic mirror that receives excitation light and irradiates a beam of excitation light onto the surface of the object to be inspected, receives fluorescence emitted from a foreign substance on the surface and separates the fluorescence in a direction different from the excitation light; A means for receiving reflected light or fluorescence from the surface of an object with a photoelectric converter and converting it into an electrical signal to detect a foreign substance on the surface of the object to be inspected; and a means for cutting excitation light from the fluorescence and transmitting the fluorescence to the photoelectric converter. It is equipped with a cut filter for inputting the input, and a switching means for switching the light beam of either the light irradiation means or the dichroic mirror so that the surface of the object to be inspected is irradiated, and the switching means switches the light beam irradiation means to the dichroic mirror. When the light beam is switched to irradiate the surface of the object to be inspected, the surface of the object to be inspected is scanned, the foreign object detection position on the surface of the object to be inspected is memorized, and the state is switched to a dichroic mirror. Sometimes, a cut filter is inserted into the path of the reflected light, excitation light is irradiated onto the foreign object at the foreign object detection position, and the electrical signal obtained by the photoelectric converter detects the foreign object determined in accordance with the fluorescence, and the dichroic mirror is activated. This method analyzes foreign substances detected by switching to a device that separates fluorescence of different wavelengths.

[Operation] The fluorescence wavelength characteristics of various resists have a peak at a specific wavelength, and the fluorescence level decreases above or below a specific wavelength. On the other hand, organic dust generated from the human body or related to humans has gentle peak characteristics and a peak that differs from the wavelength of the resist. For example, some resists have a decreased relative fluorescence intensity above 550 nm;
It has a peak at about 30 nm, and its intensity decreases around 550 r++s.

On the other hand, for cosmetic particles, there is a relatively gentle mountain between 500nm and 60nm, and the peak is also at 550nm.
It's at a certain level.

Therefore, by providing an excitation light irradiation means for foreign matter as described above, using this in conjunction with the light beam for normal foreign matter inspection, and selecting the separation wavelength characteristics of the dichroic mirror, it is possible to The foreign material content can be determined by detecting the fluorescent wavelength of the foreign material.

For example, by receiving or observing light near a fluorescence wavelength characteristic of 550 nm, it is possible to detect a foreign substance corresponding to this wavelength characteristic, ie, cosmetics, etc., and by changing the wavelength, the content of the foreign substance can be analyzed. As a result, it is possible to grasp the distribution of foreign matter generated from the semiconductor manufacturing process and foreign matter generated from the surrounding environment, and it is possible to appropriately manage the reduction of foreign matter.

[Embodiment] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a schematic diagram of a semiconductor wafer foreign matter inspection apparatus according to the present invention, FIG. 2 is a schematic flowchart for explaining the processing and control of the processing control section, and FIG. 3 is a graph of the spectral characteristics of various foreign matter. It is.

In FIG. 1, reference numeral 10 denotes an observation section for optically observing the surface of a semiconductor wafer. The observation unit 10 includes a moving stage 12 for moving the semiconductor wafer 14, an S-polarized laser beam LEA for low-angle irradiation and high-angle irradiation,
S-polarized semiconductor laser oscillation rA 16, 18 for diagonally irradiating the surface of the semiconductor wafer 14 with 18a, photodiode arrays 23, 24, and S-polarized light cut filters 21a, 21b placed in front of these photodiode arrays 23, 24, respectively. Foreign body location with and.

A detection system such as a shape, an excitation light generation light source 11 such as a mercury lamp that generates wavelength light in the UV region or B, BV region, its excitation filter 13, a dichroic mirror 15, a photodiode array 23, 24, and these photodiodes. Absorption filters 17a are placed in front of the arrays 23 and 24, respectively.

17b and an epi-fluorescence microscope system.

Note that the wavelength of the S-polarized semiconductor laser oscillator 16 for low-angle irradiation is, for example, about 830 nm, and the wavelength of the S-polarized semiconductor laser oscillator 18 for high-angle irradiation is, for example, about 780 nm, and these wavelengths are different. .

What is the detection system for foreign object position, shape, etc. and the epi-fluorescence microscope system?
The switching mechanism 19 is configured to mount the excitation light generating light source 11, the excitation filter 13, and the dichroic mirror 15, and to integrate them horizontally back and forth (Y of the moving stage 12). It is composed of a linear movable table that moves in the direction (direction), and in its backward state removes the excitation light obtained from the excitation light generation light source 11 from the reflected light path R, and in its forward state it removes the excitation light obtained from the excitation light generation light source 11 from the reflected light path R as shown in the figure. It is inserted into passage R.

Here, the dichroic mirror 15 is replaceable when the switching mechanism 19 is in the retracted state, and is used to detect foreign objects by a drive control circuit that operates according to a control signal from a processing control section 30, which will be described later. A dichroic ink mirror corresponding to the type is selected. Therefore, the wavelength at which the dichroic mirror 15 transmits the fluorescence (reflected light) generated from the foreign object to the photodiode array side is selected from various wavelength values corresponding to the foreign object to be detected.

This switching mechanism 19, like the moving stage 12, is controlled by a control signal from the drive control circuit 28, and thereby reciprocates in the Y direction. When the switching mechanism 19 is in the retracted position, absorption filters 17 a, 17 shown by dotted lines
b simultaneously retreats from in front of the photodiode arrays 23 and 24 to the back side of the drawing, and in their place are S polarization cut filters 21a and 21b shown by solid lines on the front side of the drawing.
are inserted in front of the photodiode arrays 23 and 24, respectively.

Here, when the switching mechanism 19 is in the retracted state and the excitation light is not irradiated onto the surface of the semiconductor wafer 14, the S-polarized laser beam is irradiated. At this time, the moving stage 12 moves the semiconductor wafer 14 in the X direction and
By moving the semiconductor wafer 14 in this direction, the surface of the semiconductor wafer 14 is constantly scanned in the XY direction by the S-polarized laser beam. The moving stage 12 has a built-in position encoder for detecting its scanning position, and its position information is output to the outside.

On the other hand, when the switching mechanism 19 is in the forward state and the excitation light is irradiated onto the surface of the semiconductor wafer 14, both the S-polarized semiconductor laser oscillator 16 for low-angle irradiation and the S-polarized semiconductor laser oscillator 18 for high-angle irradiation are activated. Otherwise, the polarized laser beam is cut and the surface of the semiconductor wafer 14 is not irradiated with the beam.

20 is an objective lens, 22 is a relay lens, 23° 24 is
Photodiode arrays 25 are provided to receive light of respective wavelengths from the S-polarized semiconductor laser oscillator 16 for low-angle irradiation and the S-polarized semiconductor laser oscillator 18 for high-angle irradiation, and 25 emits light in the respective directions. This is a beam splitter for separation. In addition, the beam splitter 25
Instead, a dichroic mirror for wavelength separation may be used.

Scattered light from the semiconductor wafer surface in a substantially vertical direction is transmitted by a beam splitter 25 via an objective lens 20 to
S-polarized light cut filter 21a separated in two directions of Y,
21b, only the P-polarized light component thereof is extracted, enters each photodiode array 23, 24, and is converted into an electrical signal.

When a foreign object is present at the scanning point, the surface of the foreign object has minute irregularities, so the P-polarized light component of the scattered light increases; however, when there is no foreign object, the P-polarized light component of the scattered light is sufficiently small. Incidentally, the scattered light in the vertical direction also increases at the edge portions of the pattern, but since the edge portions are smooth when viewed microscopically, the P-polarized light component of the scattered light is sufficiently small.

As a result, the ratio of the output signal levels of the photodiode arrays 23 and 24 (in some cases, the output signal level of one side), etc.
From this, it is possible to distinguish the pattern on the semiconductor wafer surface from the foreign object and determine whether or not there is a foreign object.

Further, since the output signal level of the photodiode arrays 23, 24 is proportional to the average level of the P light component of the scattered light within the field of view, the size of the foreign object can also be determined from the output level of the photodiode arrays 23, 24.

26 is a level comparison circuit for making such a determination. This level comparison circuit 28 compares the levels of the output signals of the photodiode arrays 23 and 24 with a plurality of threshold values corresponding to the foreign object size, and outputs foreign object data corresponding to the size.

28 is a drive control circuit that controls the driving motors of the moving stage 12 and the switching mechanism 19, and 30 is a processing control section. This processing control section 30 includes a microprocessor 32, a memory 34, and an interface circuit 3.
8 are interconnected by a bus 4θ.

The foreign substance data output from the level comparison circuit 2B is input to the processing control section 30 through the interface circuit 38.

Control commands for the drive control circuit 28 for controlling the replacement of the moving stage 12, the switching device (19), and the dichroic ink mirror 15 are output from the processing control unit 30 via the interface circuit 38. Position information from the moving stage 12 and the switching mechanism 19 is input via the circuit 38, and the switching mechanism 19
It is determined whether the moving stage 12 is in the backward position or the forward position, and the current position of the moving stage 12 is detected.

Reference numeral 48 denotes a keyboard, from which information can be input to the processing control section 30 via the interface circuit 38.

Reference numeral 50 denotes a display unit for displaying foreign matter content graphs, foreign matter maps, and the like. 52 is its controller, which is connected to the bus 46. This controller 52 has a built-in image memory 54 for storing display data on a display screen in the form of a bitmap. This image memory 54 is accessible by the microprocessor 32, and the controller 52 converts the data stored in the image memory 54 into a video signal and sends it to the display unit 50 for display on its display screen.

As shown in FIG. 3, the fluorescence spectrum characteristics of the resist (indicated by thick lines) and other organic foreign substances are different. Therefore,
The separation wavelength characteristics for separating the fluorescence of the dichroic mirror 15 are, for example, 500nL, 530nm, 550nL.
If you easily detect foreign substances using five types of wavelengths: nm, Boons, and 610nm, and use comparative level values that match the respective peak levels, you can detect scalp and fiber dust around 50Onm, resist at around 530nm, and 55OnIII.
It is possible to analyze the content of foreign substances, such as cosmetics near 600 nm, rubber dust (positive resist) near 600 nm, and resist near 610 nm.

FIG. 2 is a schematic flowchart showing the flow of processing by the processing control unit 30. As shown in FIG. Hereinafter, the operation of this foreign matter inspection apparatus will be explained with reference to this flowchart.

When a specific key on the keyboard 48 is pressed while the semiconductor wafer 14 is positioned and fixed on the moving stage 12, the microprocessor 32 of the processing control unit 30 executes a processing and control program (as shown in FIG. 2). (stored in memory 34) begins execution.

Note that size information of the semiconductor wafer 14 to be inspected, information on the presence or absence of fluorescence observation, designation information on the content of detected foreign substances, etc. are input in advance to the processing control unit 30 from the keyboard 48, the input information is stored, and one of these input information is input. The scanning end coordinates are calculated by the unit and stored in the coordinate table 34b on the memory 34.
is stored in

First, initialization is performed such as clearing the foreign object table 34a on the memory 34 and clearing the image memory 52 (step 100).

In step 102, a control command is sent to the drive control circuit 28 to move the moving stage 12 to the scanning start position, and the switching mechanism 19 is set to the retreat position.

When this positioning to the scan start position is completed, a scan start command is sent to the drive control circuit 28 in step 104. As a result, the moving stage 12 moves in the X direction and the X direction, and constant XY scanning of the semiconductor wafer surface by the S-polarized laser beam begins.

After starting this scanning, the determination data by the level comparison circuit 26 and the scanning position information sent from the moving stage 12 are sampled at regular intervals and held in the internal register of the microprocessor 32 (step 106).

The microprocessor 32 determines whether the sampled determination data is a code indicating a foreign object of any size (step 108).

If it is a code for a foreign object, in step 110, the determination data (a code indicating the size of the foreign object) and the scanning position information are paired and written in the foreign object code storage column and the position storage column of the foreign object table 34a, respectively.
Return to 6.

If it is determined in step 108 that the code is not a foreign object code, the process proceeds to step 112. In this step, the scan position information and the scan end coordinates stored in the coordinate table 34b are compared, and it is determined whether the scan has ended. If the process is not finished, the process returns to step 106, but if it is - finished, the process proceeds to step 114.

In this way, only the foreign matter is extracted, and its position information and size information corresponding to the detection level are stored in the foreign matter table 34a.
will be written to.

When it is determined in step 112 that the scanning has ended, a scanning stop command is sent to the drive control circuit 28, and the moving stage 12 is stopped.

In the next stage 114, it is determined from the input information whether or not there is a fluorescence observation designation, and if there is a fluorescence observation designation, in the next step 118, the microprocessor 3
2 selects the corresponding dichroic mirror 15 by referring to the first content of the designation information of the detected foreign object content. Then, the switching mechanism 19 is positioned in the forward position, and the excitation light generation light source 11, the excitation filter 13, and the selected dichroic mirror 15 are inserted into the optical path of the objective lens 20, and the S polarization cut filters 21a and 21b are inserted into the light path. The absorption filters 17a and 17b are replaced with a photodiode array 23.2.
Insert before 4.

Then, in step 118, the level comparison circuit 26
Dichroic mirror 15 is used with a comparison level value of
Set the fluorescence microscope observation level corresponding to the selected fluorescence wavelength.

Next, in step 120, the moving stage 12 is positioned so that the objective lens 20 is positioned at the coordinate position of the first foreign object according to the coordinate information stored in the foreign object table 34a, and in step 122, fluorescence microscopy observation is performed. Collecting data and determining whether or not a foreign object is detected based on the signal from the level comparison circuit 26;
When a foreign object is detected, flag information is stored in the foreign object content storage column of the foreign object table 34a.

Note that the foreign substance content column is provided corresponding to the foreign substance content detected after the foreign substance code storage column and the position position storage column of the foreign substance table 34a.

Then, in step 124, it is determined whether or not the process has ended, and if the process has not ended, the process returns to stage 120,
The coordinate position of the next foreign object is read from the foreign object table 34a.

In this way, data obtained by fluorescence microscopy observation for each position of the foreign object is stored. Once such foreign material data is collected through fluorescence microscopy, Step 1 is performed.
In step 26, it is determined with reference to the specified information whether or not there is next specified information regarding the content of the detected foreign object, and if there is next specified information, the switching mechanism 19 is set to the retracted position, and step 1 is performed.
Returning to step 16, the dichroic mirror 15 is replaced in step 116 with a dichroic mirror 15 according to the specified information, and the same process is performed again. In this case, when a foreign object is detected in step 122, flag information is stored in the next foreign object storage column after the first foreign object storage column of the foreign object table 34a, and when the dichroic mirror 15 is replaced, the flag information is stored. ,
The foreign matter content storage column is updated to correspond to the type of dichroic mirror 15. Therefore, the foreign matter detected at this time is determined by the wavelength characteristics of the dichroic mirror 15.

When the fluorescence observation data regarding the designation information of the detected foreign matter content is collected in this way, in the next step 128, each of these data is extracted from the designation information of the detected foreign matter content and the flag information about the foreign matter collected at step 122. The numerical values of the flag information are totaled, image processed by the controller 52, and the amount is displayed in a graph according to the specified foreign substance content, and displayed on the screen of the display unit 50.

One embodiment has been described above. In this embodiment, a dichroic mirror with a selected wavelength is used to scan each coordinate where a foreign object is detected, and then the dichroic mirror is replaced. Alternatively, the dichroic mirror may be replaced each time at a position where a foreign object is detected, and the foreign object may be detected according to the wavelength of the dichroic mirror, and then the foreign object may be positioned at the next foreign object detection coordinate position.

In the example, an S-polarized semiconductor laser oscillator for low-angle irradiation and an S-polarized semiconductor laser oscillator for high-angle irradiation are provided to detect foreign objects at two wavelengths, so two photodiode arrays are provided. It is not necessary to have two, and only one is sufficient even in the case of foreign matter content detection using fluorescence observation. In this case, the beam splitter 25 becomes unnecessary.

Note that when the beam splitter 25 is a dichroic mirror, it must be replaced with a beam splitter for fluorescence observation, or it must be removed when detection is performed using a single photodiode array.

Further, although a photodiode array is used in the embodiment, other light receiving elements or photomultipliers may be used, and so-called photoelectric converters in general may be used.

In addition, when the excitation light from the excitation light generation light source 11 for fluorescence observation and the dichroic mirror 15 are inserted by the switching means, and the state is switched to the state where the surface of the object to be inspected is irradiated, the power and filter are used to generate the reflected light. If it is possible to insert a 1" visual observation optical system into the passageway in place of the photoelectric converter, it is also possible to visually observe and confirm the contents of a person.

In the embodiment, a polarized laser is used, but it goes without saying that a general light beam may be used.

Further, although such a state is displayed on the display screen as a foreign object map, it may also be printed out.

In the embodiment described above, the surface of the semiconductor wafer was scanned in the XY direction, but a spiral scan may also be performed.

Further, the present invention can be similarly applied to an apparatus for inspecting the surface of an object to be inspected for foreign matter other than a semiconductor wafer.

[Effects of the Invention] As can be understood from the above explanation, in this invention, excitation light irradiation means for foreign matter is provided, and this is used in place of the light beam used in normal foreign matter inspection. By selecting the separation wavelength characteristics of the dichroic mirror, it is possible to detect the fluorescence wavelength generated from a foreign substance and determine the content of the foreign substance.

As a result, it is possible to detect foreign objects that correspond to the separation wavelength characteristics.
By changing the wavelength, the content of foreign substances can be analyzed. Therefore, it is possible to grasp the distribution of foreign matter generated from the semiconductor manufacturing process and foreign matter generated from the surrounding environment, and it is possible to appropriately manage the reduction of foreign matter.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a foreign matter inspection device according to the present invention, and FIG.
The figure is a schematic flowchart for explaining the processing and control of the processing control section, and FIG. 3 is a graph of spectral characteristics of various types of waste. DESCRIPTION OF SYMBOLS 10... Observation part, 11... Excitation light generation light source, 12.
...Moving stage, 13...Excitation filter, 14...
・Semiconductor wafer, 15... Dichroic mirror, 1
8.18...S polarization semiconductor laser oscillator, 17a, 1
7b...Absorption filter, 19...Switching mechanism, 20...Objective lens, 21a,
21b...S polarization cut filter, 23.24...
Photodiode array, 26...Level comparison circuit, 3
0... Processing control unit, 32... Microprocessor,
34...Memory, 34a...Foreign object table, 50.
...Display unit, 52...Controller,
54... Image memory.

Claims (3)

[Claims] (1) a light beam irradiation means for irradiating a light beam onto the surface of the object to be inspected; a light emitting means for generating excitation light; , a dichroic mirror that receives fluorescence emitted from a foreign substance on the surface and separates the fluorescence in a direction different from the excitation light; and a photoelectric converter that receives the reflected light from the surface of the object to be inspected or the fluorescence. means for converting the excitation light into an electrical signal to detect foreign matter on the surface of the object to be inspected; a cut filter for cutting the excitation light from the fluorescence and inputting the fluorescence to the photoelectric converter; the light irradiation means; a dichroic mirror and switching means for switching so that either one of the light beams is irradiated onto the surface of the object to be inspected, and the switching means causes the light beam irradiation means to irradiate the surface of the object to be inspected. When the state is switched to the dichroic mirror, the surface of the object to be inspected is scanned by the light beam and the foreign object detection position on the surface of the object to be inspected is memorized, and when the state is switched to the dichroic mirror, the cut filter is scanned. The excitation light is inserted into the path of the reflected light, the foreign object at the foreign object detection position is irradiated with excitation light, the foreign object determined in accordance with the fluorescence is detected by the electric signal obtained by the photoelectric converter, and the dichroic mirror is activated. A foreign matter inspection device that analyzes foreign matter detected by switching to one that separates fluorescence of different wavelengths. (2) The first light beam irradiation means irradiates the surface of the object to be inspected with a laser beam through a polarizing plate, and the switching means causes the light beam from the dichroic mirror to irradiate the surface of the object to be inspected. 2. The foreign matter inspection apparatus according to claim 1, wherein a cut filter is inserted into the path of the reflected light in place of the polarizing plate when the polarizing plate is switched. (3) The foreign matter inspection device according to claim 2, wherein the photoelectric converter is a photodiode array, and the light emitting means includes a light emitting source and an excitation filter that selects excitation light from the light from the light emitting source.