Method and apparatus for analyzing the state of generation of foreign particles in semiconductor fabrication process

We claim:

1. A defect detecting apparatus including:

an illumination system for radiating a light of a plane wave linearly to a substrate having repetitive patterns of different pitches;

a focusing optical system for focusing a light image reflected from the substrate thus illuminated by said illumination system radiating linear light;

a spatial filter disposed intermediate said focusing optical system so as to shield a diffraction light from repetitive patterns of a small pitch on the substrate;

a linear detection detector for detecting the light image obtained through said spatial filter and focused by said focusing optical system;

an erasing means for comparing and erasing signals which are generated on the basis of repetitive patterns of a large pitch and obtained through said spatial filter, out of signals detected by said detector; and

a defect detecting means for detecting defects on the substrate in accordance with a signal detected by said detector.

2. A defect detecting apparatus according to claim 1, wherein said focusing optical system is constituted by a lens array of a refractive index varying type.

3. A defect detecting apparatus according to claim 1, wherein said focusing optical system is constituted by a plurality of Fourier transform lenses, and at least the image side is telecentric.

4. A defect detecting apparatus according to claim 1, wherein said erasing means has a processing means which, in judging whether a signal of one picture element on said detector is defective or not, compares the level of the one picture element signal on the detector with a signal level of a picture element present in a corresponding position of an adjacent repetitive pattern taken in by the detector and signal levels of plural picture elements adjacent to said corresponding position, and judges that the detected signal from the one picture element on the detector is a signal from the repetitive pattern in the case where a picture element of a signal level equal to that of the one picture element is present among the signal levels in said corresponding or adjacent positions.

5. A defect detecting apparatus according to claim 1, wherein said spatial filter has linear patterns and the pitch of linear patterns of said spatial filter is set in such a manner that the pitch of repetitive patterns shielded by the spatial filter is larger than a value several times as large as the width of a combined area of said corresponding and adjacent picture elements.

6. A defect detecting apparatus according to claim 5, further including:

a Fourier transform means for Fourier transforming the signals detected by said detector;

a pitch calculating means for calculating a pitch of Fourier transform images based on repetitive patterns formed on a sample, in accordance with the result of operation performed by said Fourier transform means, and a pitch changing means for changing the spatial filter pitch on the basis of the result obtained by said pitch calculating means.

7. A defect detecting apparatus according to claim 6, further including a pitch calculating means for calculating a spatial filter pitch corresponding to a very small signal provided from said detector, and a pitch changing means for changing the spatial filter pitch into a pitch equal to the pitch calculated by said pitch calculating means.

8. A defect detecting apparatus according to claim 1, wherein the detector includes a telecentric type detection lens, and the spatial filter is in a one-dimensionally compressed state.

9. A defect detecting apparatus according to claim 1, wherein the spatial filter is a linear spatial filter, and the illumination system has an incidence surface parallel to said linear spatial filter, and further comprising means for matching the incidence surface of the illumination system, a longitudinal direction of the linear spatial filter and a repetitive direction of patterns present on a substrate.

10. A defect detecting apparatus according to claim 1, wherein zero-order diffraction light rays from various points on an object pass through the center of a pupil plane (a spatial filter mounted plane) of a detecting optical system of the detector.

11. A defect detecting apparatus including:

a conveyance means for conveying a substrate having repetitive patterns;

an illuminating system for radiating a light of a plane wave linearly to the substrate being conveyed by said conveyance means;

a focusing optical system for focusing a light image reflected from the substrate thus illuminated by said illumination system radiating linear light;

a spatial filter disposed in a focusing position intermediate said focusing optical system so as to shield a diffraction light from repetitive patterns on the substrate, said spatial filter comprising a plurality of linear shields capable of having their mutual spacing changed in relation to the repetitive patterns of the substrate;

a linear detection detector for detecting a light image obtained through said spatial filter and focused by said focusing optical system; and

a defect detecting means for detecting defects on the substrate in accordance with a signal detected by said detector.

12. A defect detecting apparatus according to claim 11, wherein said focusing optical system comprises a plurality of Fourier transform lenses, and at least the image side is telecentric.

13. A defect detecting apparatus according to claim 12, wherein said plural Fourier transform lenses are composed of lens groups of different numerical apertures so that one said Fourier transform lens group can be replaced with a lens group of a different numerical aperture.

14. A defect detecting apparatus according to claim 11, further including a measuring means for measuring the direction of repetitive patterns on the substrate, and a control means for controlling the direction of said linear shields of said spatial filter in accordance with the direction of the repetitive patterns on the substrate measured by said measuring means.

15. A defect detecting apparatus according to claim 11, wherein said detector is constituted by a linear detector.

16. A detect detecting method comprising:

radiating a light of a plane wave linearly to a substrate having repetitive patterns of different pitches, by means of an illumination system;

focusing a light image reflected from the substrate thus illuminated by radiated linear light, by means of a focusing optical system, and at the same time shielding a diffraction light from repetitive patterns of a small pitch present on the substrate, by means of a spatial filter disposed intermediate said focusing optical system;

detecting the light image obtained through said spatial filter and focused by said focusing optical system, by means of a linear detection detector;

comparing and erasing signals which are generated on the basis of repetitive patterns of a large pitch present on the substrate and obtained through said spatial filter, out of the detected signals, by means of an erasing means; and

detecting a defect on the substrate on the basis of a signal obtained by said erasing means.

17. A defect detecting method comprising:

conveying a substrate having repetitive patterns;

radiating a light of a plane wave linearly to the substrate being conveyed;

focusing a light image reflected from the substrate thus illuminated by radiated linear light, by means of a focusing optical system and at the same time shielding a diffraction light from repetitive patterns on the substrate by means of a spatial filter disposed intermediate said focusing optical system and constituted by a plurality of linear shields capable of having their mutual spacing changed in relation to the repetitive patterns of the substrate;

linearly detecting the light image obtained through said spatial filter and focused by said focusing optical system; and

detecting a defect on the substrate on the basis of the detected signal.

18. A method of inspecting foreign particles on a product substrate in a mass production line of a semiconductor fabrication process, comprising the steps of:

transferring the product substrate along a path of transferring means provided at at least one predetermined position in the mass production line of the semiconductor fabrication process;

detecting a rotation direction of repetitive patterns of a circuit pattern being formed on the transferred product substrate;

illuminating light of a substantially slit shape on the surface of the product substrate transferred along the path of the transferring means;

detecting with a detecting means information of a surface of the product substrate including detecting scattered light from foreign particles existing on the surface of the product substrate transferred along the path of the transferring means and illuminated by the light of substantially slit shape through a detecting lens,

a spatial filter comprising linear repetitive patterns and provided on a Fourier transform plane of the surface of the product substrate;

aligning relatively the detected direction of the repetitive patterns of the product substrate and a direction of the detecting means,

aligning relatively the detected direction of the respective patterns of the product substrate and a direction of the spatial filter, the spatial filer enabling shielding of diffraction light from the small repetitive patterns of the circuit pattern imaged on the Fourier transform plane through the detecting lens; and

determining a state of foreign particles on the product substrate transferred along the path of the transferring means in accordance with the detection of the scattered light.

19. A method according to claim 18, wherein an illumination means serves for illuminating light of the substantially slit shape on the surface of the product substrate and the detecting means includes a photo-detector array detecting the scattered light from the foreign particles and providing an output signal indicative thereof, the step of determining the state of foreign particles includes effecting determination in accordance with the output signal from the photodetector array.

20. A method according to claim 19, wherein the step of detecting the rotation direction of repetitive patterns of the circuit pattern includes detecting a rotation direction of an orientation flat of the product substrate, the product substrate being a product wafer.

21. A method according to claim 20, wherein the step of aligning relatively includes controlling the rotation of the product wafer to effect the relative alignment.

22. A method according to claim 19, wherein the step of illuminating includes illuminating light of substantially slit shape in a zig-zag arrangement so as to effect overlapping of adjacent illumination without interference with the detecting lens.

23. A method according to claim 19, wherein the detecting lens is a detecting lens array and a length of the detecting lens array and a length of the substantially slit shape light corresponds substantially to a diameter of the product wafer so as to enable detection of foreign particles on the product wafer during transfer along the path of the transferring means.

24. A method according to claim 19, wherein the step of determining the state of foreign particles on the product wafer includes effecting display on a monitor.

25. A method according to claim 19, wherein the step of detecting the state of foreign particles on the product wafer includes effecting calibration in accordance with a measured refractive index of the product wafer.

26. A method according to claim 19, wherein the detecting lens for enabling detection of the scattered light has a focal depth of 0.1 to 0.5 mm.

27. A method according to claim 22, wherein the step of illuminating in a zig-zag pattern includes effecting illumination from opposite sides.

28. A method according to claim 18, wherein the step of illuminating includes utilizing white light and illuminating the surface of the product substrate at an oblique angle with respect to a perpendicular direction thereto.

29. A method according to claim 18, further comprising the step of determining characteristics of a production apparatus of the mass production line based upon the detected rotational direction of the product substrate and the determined state of foreign particles with respect to the detected rotational position.

30. A method according to claim 18, wherein the step of illuminating includes illuminating the surface of the product wafer at an oblique angle with respect to a perpendicular direction thereof.

31. A method according to claim 18, wherein the step of determining includes determining a distribution of foreign particles in accordance with the detection of the scattered light and a two-dimensional coordinate determined for the product substrate based upon the detected rotation direction.

32. A method according to claim 19, wherein the step of illuminating includes utilizing coherent light.

33. A method according to claim 19, further comprising the step of enabling change of a filtering pattern of the spatial filter.

34. An apparatus for inspecting foreign particles on a product substrate in a mass production line in a semiconductor fabrication process, comprising:

transferring means provided at least one predetermined position in the mass production line of the semiconductor fabrication process for transferring the product substrate along a path thereof;

means for detecting a rotation direction of repetitive patterns of a circuit pattern being formed on the transferred product substrate;

illuminating substantially slit shape light on the surface of a product substrate transferred along the path of the transferring means;

detecting means for detecting information of a surface of the product substrate through a detecting lens including detecting scattered light from foreign particles existing on the surface of the product substrate transferred along the path of the transferring means and illuminated by the substantially slit shape light through the detecting lens,

a spatial filter comprising linear repetitive patterns and provided on a Fourier transform plane of the surface of the product substrate;

means for enabling relative alignment of the detected direction of the repetitive patterns of the product substrate and a direction of the detecting means,

means for relatively aligning the detected direction of the respective patterns of the product substrate and a direction of the spatial filter, the spatial filter enabling shielding of diffraction light from the repetitive patterns of the circuit pattern imaged on the Fourier transform plane through the detecting lens; and

means for determining a state of foreign particles on the product substrate transferred along the path of the transferring means in accordance with the detection of the scattered light, wherein said means includes determining a distribution of foreign particles in accordance with an output of the detection means and in accordance with the means for enabling alignment.

35. A foreign particle detecting apparatus according to claim 34, further including an erasing means for comparing and erasing signals which are generated on the basis of repetitive patterns of a large pitch on the substrate and obtained through said spatial filter, out of signals detected by said detecting means.

36. A defect detecting apparatus including:

an illumination system for radiating light to a substrate having repetitive patterns of different pitches;

a focusing optical system for focusing a light image reflected from the substrate thus illuminating by said illumination system;

a spatial filter disposed intermediate said focusing optical system so as to shield a diffraction light from repetitive patterns of a small pitch on the substrate;

a detector for detecting the light image obtained through said spatial filter and focused by said focusing optical system;

an erasing means for comparing and erasing signals which are generated on the basis of repetitive patterns of a large pitch and obtained through said spatial filter, out of signals detected by said detector; and

a defect detecting means for detecting defects on the substrate in accordance with a signal detected by said detector.

37. A defect detecting apparatus including:

a conveyance means for conveying a substrate having repetitive patterns;

an illuminating system for radiating light to the substrate being conveyed by said conveyance means;

a focusing optical system for focusing a light image reflected from the substrate thus illuminated by said illumination system;

a spatial filter disposed in a focusing position intermediate said focusing optical system so as to shield a diffraction light from repetitive patterns on the substrate, said spatial filter comprising a plurality of linear shields capable of having their mutual spacing changed in relation to the repetitive pattern of the substrate;

a detector for detecting a light image obtained through said spatial filter and focused by said focusing optical system; and

a defect detecting means for detecting defects on the substrate in accordance with a signal detected by said detector.

38. A detect detecting method comprising:

radiating light to a substrate having repetitive patterns of different pitches, by means of an illumination system;

focusing a light image reflected from the substrate thus illuminated, by means of a focusing optical system, and at the same time shielding a diffraction light from repetitive patterns of a small pitch present on the substrate, by means of a spatial filter disposed intermediate said focusing optical system;

detecting the light image obtained through said spatial filter and focused by said focusing optical system, by means of a detector;

comparing and erasing signals which are generated on the basis of repetitive patterns of a large pitch present on the substrate and obtained through said spatial filter, out of the detected signals, by means of an erasing means; and

detecting a defect on the substrate on the basis of a signal obtained by said erasing means.

39. A defect detecting method comprising:

conveying a substrate having repetitive patterns;

radiating light to the substrate being conveyed;

focusing a light image reflected from the substrate thus illuminated, by means of a focusing optical system and at the same time shielding a diffraction light from repetitive patterns on the substrate by means of a spatial filter disposed intermediate said focusing optical system and constituted by a plurality of linear shields capable of being having their mutual spacing changed in relation to the repetitive patterns of the substrate;

detecting the light image obtained through said spatial filter and focused by said focusing optical system; and

detecting a defect on the substrate on the basis of the detected signal.

Description Submit all comments and votes

BACKGROUND OF THE INVENTION

The present invention relates to a method and apparatus for analyzing the state of generation of foreign particles in a semiconductor fabrication process, more particularly, detecting and analyzing foreign particles generated in a mass production starting line and a mass production line of the said process and taking an appropriate countermeasure, or a foreign particle inspecting apparatus for inspecting foreign particles on a semiconductor substrate.

In the conventional semiconductor fabrication process, if foreign particles are present on a semiconductor substrate (wafer), they will cause defects such as defective insulation of wiring and short-circuit. Further, in the case where a fine foreign particle is present in a semiconductor substrate provided with very fine semiconductor elements, such foreign particle will cause breakdown of an insulating film of a capacitor or a gate oxide film. Foreign particles are generated by various causes and in various conditions; for example, they are generated from an operating portion of a conveyance system, generated from the human body, or result from reaction in a processing apparatus using a process gas, or are already incorporated in chemicals, materials, etc.

A conventional method for detecting such foreign particles on a semiconductor substrate is disclosed in Japanese Patent Laid Open No. 89336/87, which method comprises radiating a laser beam onto the semiconductor substrate, detecting a scattered light from foreign particles if deposited on the substrate, then comparing the result with the result of inspection of the same type of a semiconductor substrate conducted just before, thereby eliminating a false information based on pattern and permitting a foreign particle inspection of high sensitivity and high reliability. Also in Japanese Patent Laid Open No. 135848/88 there is disclosed a method which comprises radiating a laser beam onto a semiconductor substrate, detecting a scattered light from foreign particles if deposited on the substrate, and then analyzing the detected foreign particles using an analyzing technique such as laser photoluminescence or secondary X-ray analysis (XMR).

In the above conventional methods, distinction is made between a mass production starting line and a mass production line in a semiconductor fabrication process, and an inspection apparatus used in the mass production starting operation is applied as it is to the mass production line, so it is necessary in the mass production line to detect the generation of foreign particles and take a countermeasure as soon as possible. However, the conventional inspection apparatus is a stand-alone type and the semiconductor substrate which has been processed in the fabrication line is carried to the installed place of the inspection apparatus and inspected there for foreign particles. Thus, it takes time for conveyance of the semiconductor substrate and for the inspection of foreign particles, so that it is difficult to increase the inspection frequency up to a sufficient value.

In the prior art, in addition to the large scale of equipment, a long time is required for the inspection, so for realizing a real-time monitor using such conventional apparatus, it is necessary to arrange a large number of large-sized apparatus, but actually this has been difficult. Actually it has been possible to inspect at most one or several lots or one sheet of a semiconductor substrate a day. In such a frequency of foreign particle inspection, it cannot be said that the generation of foreign particles is detected sufficiently rapidity. Such inspection in the prior art has been remote from the ideal real-time sampling in the mass production line. Further, for decreasing the number of steps in the mass production line and for diminishing equipment, it has been necessary to provide a required and sufficient number of monitors in a required and sufficient number of places. This has also been a subject to be attained.

One of main mass production starting operations for LSI is an operation of clearing up the cause of generation of such foreign particles and taking a countermeasure. In this connection, detecting foreign particles and analyzing the kind of element, etc. is an important clue to clear up the cause of their generation. On the other hand, in the mass production line, it is necessary to detect the generation of foreign particles and take a countermeasure as soon as possible. As time elapses from the generation of foreign particles up to the detection thereof, the number of defects generated increases and hence the yield lowers. Therefore, in order to maintain a high yield, it is absolutely necessary to shorten the time elapsed from the generation of foreign particles until the detection thereof. In other words, in order to maximize the effect of the foreign particle inspection, it is necessary to shorten the sampling time in a monitor, and ideally it is desirable to perform a real-time sampling for the mass production line.

SUMMARY OF THE INVENTION

It is the object of the present invention to provide a method and apparatus for analyzing the state of generation of foreign particles in a semiconductor fabrication process of a mass production line, which apparatus is installed at an inlet or outlet of a processing apparatus or in a conveyance system between plural processing apparatus so as to permit detecting the state of generation of foreign particles on a semiconductor substrate in real time.

In one aspect of the present invention, a real-time sampling is realized, and a foreign particle monitoring unit used therein is small-sized so that it can be installed at an inlet or outlet of a processing apparatus in a semiconductor fabrication line or in a conveyance system between processing apparatus. More specifically, according to one aspect of the present invention there is provided an apparatus for analyzing the state of generation of foreign particles in a semiconductor fabrication process, characterized in that, in a semiconductor mass production line provided with plural processing apparatus, a foreign particle monitoring unit for detecting the state of generation of foreign particles on a semiconductor substrate is installed at an inlet or outlet of a predetermined processing apparatus or in a conveyance system between plural processing apparatus to detect the state of generation of foreign particles on the semiconductor substrate in the processing apparatus, the foreign particle monitoring unit including an oblique lighting system constituted by an illumination array, a focusing optical system constituted by a lens array or a group of microlenses, a spatial filter disposed on a Fourier transform plane of the focusing optical system, a detector disposed in a focused position of the focusing optical system, and an erasing means for erasing pattern signals which are produced repeatedly on the substrate, and also provided is a method for such analysis.

In another aspect of the present invention there is provided a foreign particle inspecting apparatus for inspecting foreign particles on a semiconductor substrate, the foreign particle inspecting apparatus including a lighting system for illuminating the semiconductor substrate in a substantially linear shape with plane wave of a short wavelength, a focusing optical system for focusing a reflected light image from the semiconductor substrate thus illuminated by the lighting system, a spatial filter mounted halfway in the focusing optical system so as to intercept a diffracted light from repetitive patterns on the substrate, a detector for detecting the focused light image, an erasing means for erasing a signal which is produced repeatedly on the substrate out of signals detected by the detector, and a foreign particle detecting means for detecting foreign particles on the substrate on the basis of a signal which had not been erased by the erasing means. In this foreign particle inspecting apparatus, moreover, the present invention is characterized in that the focusing optical system is constituted by a lens array of a refractive index changing type.

In a further aspect of the present invention there is provided a defect detecting apparatus including a lighting system for illuminating a substrate having repetitive patterns of different pitches, linearly using a plane wave light, a focusing optical system for focusing a reflected light image from the substrate thus illuminated by the lighting system, a spatial filter installed halfway in the focusing optical system so as to intercept a diffracted light from repetitive patterns of a small pitch, a detector for detecting a light image obtained through the spatial filter and focused by the focusing optical system, an erasing means which compares signals with each other obtained through the spatial filter and on the basis of repetitive patterns of a large pitch and erases a signal, and a defect detecting means for detecting a defect on the substrate on the basis of a signal provided from the erasing means, and also provided is a defect detecting method associated therewith.

In a still further aspect of the present invention there are provided an apparatus and a method according to the above defect detecting apparatus and method in which the erasing means has a processing means which, in judging whether a signal of one picture element on the detector is defective or not, compares the signal level of one picture element on the detector with the signal level of a picture element present in a corresponding position of adjacent repetitive pattern which has been taken in by the detector and those of plural picture elements present in close proximity to the said corresponding position, and in the case where a picture element of an equal value to the signal level of the said one picture element is present among the signal levels in the said corresponding position or proximate position, judges that the detected signal of one picture element on the detector is a signal from repetitive pattern.

In a still further aspect of the present invention there is provided a defect detecting apparatus including a conveying means for the conveyance of a substrate having repetitive patterns, a lighting system for radiating light of a plane wave linearly to the substrate being conveyed by the conveying means, a focusing optical system for focusing a reflected light image from the substrate thus illuminated by the lighting system, a spatial filter disposed in a focused position halfway of the focusing optical system so as to intercept a diffracted light from repetitive patterns on the substrate, the spatial filter comprising a plurality of linear shields disposed so as to be variable in their spacing, a detector for detecting a light image obtained through the spatial filter and focused by the focusing optical system, and a defect detecting means for detecting a defect on the substrate on the basis of a signal detected by the detector.

The present invention is an improvement over U.S. Ser. No. 07/778363.

At the time of starting of mass production in a semiconductor fabrication process, each process and equipment are evaluated by means of an evaluation equipment of high performance which is expensive, for making evaluation and debug of material, process, apparatus and design, and at the time of mass production, the number of processes and equipment in the production line are minimized, particularly the number of inspection and evaluation items is decreased to reduce the equipment cost and shorten the time required for inspection and evaluation. To this end, various considerations are given to permit a smooth and quick evaluation at the time of starting of mass production. For example, sampling is made along this line or a semiconductor substrate is inspected using an improved foreign particle detecting and analyzing system to clear up the cause of generation of foreign particles, then the specification of inspection in the acquisition of materials is changed or a certain measure is taken against a dust generation source on the basis of the result obtained, which result is fed back to each material, process and apparatus to, for example, change the specification of a dust-prone process into a design of elements which strong against the generation of dust. At the same time, such result is utilized in preparing specifications for inspection and evaluation in the mass production line, and where required, a monitor for foreign particles on a semiconductor substrate is mounted in a place where foreign particles are apt to occur, or a specification is prepared to monitor only increase and decrease of specific foreign particles present in a specific place.

By thus separating the mass production starting line and the mass production line from each other, it is made possible to effect an efficient operation of the apparatus for detecting, analyzing and evaluation foreign particles at the time of starting of mass production and hence it is possible to perform the mass production starting work rapidly. Besides, the reduction in weight of the mass production line can be attained by using a minimum required number of monitoring apparatus of a simple structure as the foreign particle inspecting and evaluating apparatus used in the mass production line.

In connection with the above monitoring apparatus used in the mass production line according to the present invention, we have paid attention to the following method in order to realize, using the existing technique, a small-sized, high-speed inspection apparatus having an equal function to that of the conventional large-sized apparatus. First, the repeatability of memory was noted. Heretofore, a method of removing repetitive patterns and detecting defects has been known. This conventional method ensures a detection performance. However, no convenient point has been referred to about such method in realizing the said monitoring apparatus. Further, it is not necessary to monitor all of points on a semiconductor substrate, but it suffices to monitor the upper surface of the substrate at a certain specific ratio. In the manufacture of a memory having lots of repetitive patterns, even a mere monitor of only the repetitive portion of the memory is very effective.

In repetitive patterns, the radiation of a coherent light causes exit of light only in a certain specific direction. More particularly, in the case of memory, light emerging in a specific direction from a repetitive portion can be intercepted using a spatial filter and it is possible to detect, in high sensitivity, foreign particles which are not apt to occur repeatedly. In this case, if liquid crystal is used as the spatial filter, the shape of the spatial filter can be changed as desired by turning on-off of the liquid crystal and therefore it is possible to inspect any repetitive pattern automatically.

The reason why the yield in semiconductor fabrication is improved by the above means is as follows. As a result of a strict experiment for detecting the number of foreign particles on a semiconductor substrate, it turned out that the number of foreign particles increased or decreased suddenly, not gradually. Heretofore, since the number of foreign particles has been considered to increase or decrease gradually, the inspection of foreign particles has been conducted at a frequency of one lot or one sheet a day as noted previously. In such a low inspection frequency, however, a sudden increase in the number of foreign particles will be overlooked, or detection may be made in a little while after the increase, thus resulting in occurrence of a considerable number of defects. That is, in the mass production line, it is necessary to detect the generation of foreign particles and take a countermeasure as soon as possible. With the lapse of time from the generation of foreign particles until detection thereof, the number of defects generated increases and the yield lowers. In other words, a high yield can be ensured by shortening the time elapsed from the time when foreign particles are generated until when the generation is detected. That is, the effect of the foreign particle inspection can be exhibited to the maximum extent by shortening the sampling time in monitor or ideally by sampling in real time.

In the conventional apparatus, moreover, a semiconductor substrate is pulled out for inspection and in this case foreign particles will newly be deposited on the semiconductor substrate, thus also resulting in lowering of the yield. On the other hand, the foreign particle inspection apparatus according to the present invention permits the inspection without the need of pulling out a semiconductor substrate, so that there will be no lowering of the yield caused by the deposition of foreign particles on the substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1(a)-1(c) are diagrams showing a relation between detected picture element size and noise level according to the present invention;

FIG. 2 is a construction diagram of a foreign particle detecting optical system using a spatial filter according to the present invention;

FIG. 3 is a diagram showing a light intensity distribution on a spatial filter surface according to the present invention;

FIG. 4 is a diagram showing a discrimination ratio in the foreign particle detecting optical system according to the present invention;

FIG. 5 is a diagram showing a relation between detected picture element size and discrimination ratio according to the present invention;

FIG. 6 is a diagram showing an illumination area and a detection area according to the present invention;

FIGS. 7(a)-7(c) are performance diagrams for deciding apparatus specifications according to the present invention;

FIG. 8 is a diagram showing an apparatus construction of a foreign particle detecting optical system according to the present invention;

FIGS. 9(a) and 9(b) are diagrams showing an example of influence of a wafer rotational angle upon a pattern noise light according to the present invention;

FIGS. 10(a)and 10(b) are diagrams showing an example of changes in a foreign particle detection output caused by changes in a wafer stage height according to the present invention;

FIGS. 11(a) and 11(b) are sides views of a lighting unit according to the present invention;

FIGS. 12(a) and 12(b) are plan view of a diffraction pattern on a spatial filter surface according to the present invention;

FIGS. 13(a) and 13(b) are side views of a lighting unit according to the present invention;

FIG. 14 is a plan view of a diffraction pattern on a spatial filter surface according to the present invention;

FIG. 15 is a construction diagram of a foreign particle detecting optical system using polarized light for detection according to the present invention;

FIG. 16 is a diagram showing an apparatus construction of a foreign particle detecting optical system using polarized light for detection according to the present invention;

FIGS. 17(a)-17(c) are diagrams showing in what position the present invention lies and also showing functions;

FIG. 18 is a block diagram showing an example of a signal processing system according to the present invention;

FIG. 19 is a construction diagram showing an embodiment of the present invention using a variable spatial filter;

FIG. 20 is a concrete construction diagram of the variable spatial filter shown in FIG. 19;

FIG. 21 is another concrete construction diagram of the variable spatial filter shown in FIG. 19;

FIG. 22 is a construction diagram showing another embodiment of the present invention using a variable spatial filter;

FIG. 23 is a concrete construction diagram of the variable spatial filter shown in FIG. 22;

FIG. 24 is a block diagram of an apparatus embodying the present invention;

FIGS. 25(a)-25(c) are construction diagrams showing an example of a detection head illustrated in FIG. 24;

FIG. 26 is a perspective view of a spatial filter mechanism illustrated in FIG. 24;

FIG. 27 is a construction diagram showing an operator processing section illustrated in FIG. 24;

FIG. 28 is a block diagram showing a parameter detecting system illustrated in FIG. 24;

FIGS. 29(a)-29(c) are construction diagrams showing a conventional method;

FIGS. 30(a)-30(d) are construction diagrams showing a basic concept of the present invention;

FIGS. 31(a) and 31(b)(1)-31(b)(3) are construction diagrams showing a pattern removing method according to the present invention;

FIG. 32 is a block diagram showing another example of a parameter detecting system according to the present invention;

FIGS. 33(a) and 33(b) are construction diagrams of detection lenses according to the present invention;

FIGS. 34(a) and 34(b) are construction diagrams showing a rotational deviation detecting system according to the present invention;

FIG. 35 is a schematic diagram showing the effect of a comparative