JPH03189545A - Defect inspecting device - Google Patents

Abstract

PURPOSE:To detect the presence or absence of a foreign matter adhering to the thin film such as a pellicle and to easily discriminate a surface to which the foreign matter adheres by receiving scattered light from a defect such as the foreign matter by two light receiving systems arranged at different angles with respect to the surface of a flat object. CONSTITUTION:Illuminating light from a light source 21 is made incident on a condens ing lens 22. The optical axis of the lens 22 is set to be vertical to the surface of the pellicle 2 of a reticle 1 and the illuminating light is condensed on the local area of the pellicle 1. Between scattered light receiving systems, the 1st light receiving system includes the condensing lens 25 having an optical axis inclined by an angle thetaa with respect to the normal of the pellicle 2 and the 2nd light receiving system includes the condensing lens 26 having an optical axis inclined by an angle thetab with respect to the normal of the pellicle 2, then they respectively allow for the illuminated area of the pellicle 2. Dichroic morrors 27A, 27B, 27D and 27E having wavelength selectivity are provided in the two light receiving systems and photoelectric conversion devices 28A-28F for individually detecting the scattered light of every specified wave length area which is spectrally splitted are provided. By comparing the photoelectric signals therefrom, whether the defect exists on the surface or the back surface of the pellicle 2 is discriminated.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is directed to detecting the presence and size of fine particles attached to a light-transmitting flat object, such as glass or a thin polymer film such as nitrocellulose. The present invention relates to an inspection device, and particularly to a defect inspection device that can identify foreign matter defects on the front and back surfaces of a flat support.

[Conventional technology]

Conventionally, this type of device has been considered to have a structure as shown in FIG. 4, for example.

In FIG. 4, pellicles (polymer thin films) 2 are stretched across a frame 3 at regular intervals on the surface of a reticle (or mask) 1 for manufacturing semiconductor devices. This pellicle 2 is used to prevent foreign matter from directly adhering to the surface of the reticle 1, and the thickness of the pellicle 2 is 1 μm.
Illumination light for exposure (wavelength 436 nm, 3650-, etc.)
It has a transmittance of 90% or more. Further, the thickness (standoff) of the frame 3 is approximately a few inches thick, and this is determined in consideration of the depth of focus on the reticle side of the projection optical system of the exposure device. When projecting and exposing an IC pattern onto a wafer using such a reticle with a pellicle,
The foreign object image on the reticle surface can be reduced in size and transferred onto the wafer according to the reduction magnification of the projection optical system, but the image of the same size foreign object attached to the pellicle 2 is largely defocused on the wafer. It will not be resolved. However, if the foreign object on the pellicle 2 is too large (several tens of micrometers or more), it will appear as a defocused shadow.

Therefore, as shown in FIG. 4, it is necessary to also inspect foreign matter attached to the pellicle 2. Illumination light (coherent light, quasi-monochromatic light, etc.) LB emitted from the light source 4 is perpendicularly irradiated onto the pellicle 2 via the condenser lens 5 .

If a foreign object exists within the irradiation area (spot irradiation area) of the pellicle 2, the foreign object generates scattered light with relatively weak directivity.

A part of the scattered light DL of this scattered light is focused by a condensing lens 6 onto a light receiving surface of a photoelectric converter (photomultiplier, etc.) 7. Here, the optical axis of the condensing lens 6 is made oblique to the surface of the pellicle 2 so that scattered light from the pellicle 2 itself is not received by the photoelectric converter 7.

At the same time, it is arranged so as to spatially avoid scattered light generated from the reticle 1.

Then, it is determined whether or not it is a foreign object based on the level of the photoelectric signal.

At this time, it is necessary to inspect the entire surface of the pellicle 2, so a mechanism is provided to scan the illumination light LB in one dimension (or two dimensions) and move the pellicle 2 (reticle 1) in a negative dimension. There is.

In addition, other pellicle inspection devices include, for example, as disclosed in Japanese Patent Application Laid-open No. 176129/1983.
A laser beam is irradiated onto the surface to be inspected (pellicle) at a grazing angle to form a band-shaped irradiation area on the object to be inspected, and a primary laser beam is placed at the position where side scattered light of the scattered light from the irradiation area is received. It is also known that an original array sensor (CCD) is arranged to perform foreign object inspection.

[Problem to be solved by the invention]

However, in the conventional technique shown in FIG.
It was not possible to determine whether the particles were attached to the back side (hereinafter referred to as the back side) or the light source side (hereinafter referred to as the front side). Furthermore, the method disclosed in Japanese Patent Application Laid-open No. 61176129 can only detect foreign matter only on the front surface of a flat object; however, it is difficult to determine whether foreign matter is attached to the front or back surface of a glass substrate (reticle, mask, etc.). As a method, JP-A-58-
The technique disclosed in Publication No. 62544 is also known,
In this case, a pair of photoelectric elements is required, one for receiving the scattered light generated in the space on the front side of the substrate, and the other for detecting the scattered light generated in the space on the back side of the substrate.

For this reason, for a single pellicle, it may be possible to distinguish between the front and back sides of attached foreign matter using the same principle, but when the pellicle is attached to a reticle, the scattered light is blocked by the reticle pattern (chrome layer). , inspection is not possible.

Knowing whether the foreign matter attached to the pellicle exists on the front side or the back side has extremely important meaning in the photolithography process. If foreign matter adheres to the back side of the pellicle, in the worst case, the foreign matter may separate from the pellicle and re-attach to the reticle, resulting in defects in shots of exposed wafers using the reticle. Therefore, for such a reticle, it is necessary to remove the pellicle together with the frame, remove foreign matter from the reticle, and replace it with a new pellicle.

Therefore, it is important to reliably know whether or not a new pellicle needs to be replaced before exposure work is performed on an actual device.

The present invention aims to provide a defect inspection device that can detect the presence or absence of foreign matter adhering to a thin film such as a pellicle or a thin glass plate, and can easily and reliably perform front and back surface discrimination (adhered surface discrimination). purpose.

[Means to solve problems]

In order to achieve the above object, the present invention uses polychromatic light with a predetermined wavelength band or white light (broadband light) as the light that illuminates a flat object as an object to be inspected, so that defects such as foreign matter can be avoided. The scattered light is received by at least two light receiving systems arranged at different angles with respect to the surface of the flat object. These two light-receiving systems are each equipped with an optical element with wavelength selectivity (such as a guichroic mirror or a cold mirror prism), and are equipped with a photoelectric converter that individually photoelectrically detects the scattered light in each specific wavelength range. .

By comparing the magnitudes of these photoelectric signals, it is determined whether the defect exists on the front or back surface of the flat carrier object.

[For production]

FIG. 2 is a diagram illustrating the present invention in detail, in which a foreign substance 12 is attached to the back side of the pellicle 2, and polychromatic light (or white light) is emitted vertically or nearly vertically from the front side of the pellicle 2. The case of irradiation with SI is shown.

In conclusion, when the scattered light from the foreign object 12 is photoelectrically detected via the becryl 2 as shown in Fig. 2, the wavelength distribution of the scattered light toward the photoelectric detector is different from the wavelength distribution of the polychromatic light S1. becomes.

On the other hand, if a foreign object is attached to the surface side of the pellicle 2 (the side of incidence of the illumination light SI), the scattered light from the foreign object is the polychromatic light SI.
It heads toward the photoelectric detector while maintaining almost the same wavelength distribution as .

Therefore, by detecting the difference in the wavelength distribution of the scattered light incident on the light receiving system, it is possible to determine the surface on which foreign matter has adhered.

The above will be further explained in detail with reference to FIG.

In the state shown in FIG. 2, among the scattered light generated from the foreign object 12,
Scattered light S that returns to the surface side at an angle θ1 with respect to the polychromatic light S1!
Focus on.

The scattered light St is further divided into light S that is emitted from the surface of the pellicle 2 and goes toward the light receiving system, and light S that travels toward the back surface by internal reflection. The exit angle θ2 of the light S is expressed by the following equation, where n is the refractive index of the pellicle 2.

θz = sin -' (n -5inθ1)...
・・・・・・・・・・・・・・・(1) On the other hand, the light S4 is divided into the light S which is refracted and emitted from the back surface of the bezel 2, and the light S6 which is reflected internally again, and is reflected internally. Light S, ha...
It is refracted and reflected again on the surface of the pellicle 2. Of the light Sb,
The light S7 refracted on the surface of the pellicle 2 and emitted is the light S,
It heads almost parallel to the light receiving system. Therefore, the exit angle of the light S is also θ2.

Here, the phase difference δ between the lights S and S is expressed by the following equation, where d is the thickness of the pellicle 2.

4z−nd−cosθ1 δ= ・・・・・・・・・
・・・・・・(2)λ Then, the condition that the phase difference δ is exactly 360°, that is, the wavelength λm where δ = 2mπ (where m is an arbitrary integer)
is as follows.

2 ・ n −d −CO3θ λm− ・・・・・・・・・・・・・・・・・・・・・・・・・・・(3) Also, from equation (1), the angle θ is 3), the specific wavelength λm becomes: (4)

Therefore, if the angle between the optical axis of the scattered light receiving system and the normal to the pellicle 11 is set to 02, the light S incident on the scattered light receiving system
3. The spectral characteristics of St have a peak at wavelength λm, and are attenuated in wavelength ranges on both sides of the peak.

In the present invention, the surface on which foreign matter is attached is determined by examining the spectral characteristics of the scattered light from the foreign matter attached to the pellicle at a different angle θ2. That is, as is clear from the above principle, the angle between the optical axis of the scattered light receiving system and the pellicle surface (9
0°-02), it can be seen that even under the same illumination conditions, the specific wavelength λm that is the peak in the spectral characteristics of the scattered light changes.

Similarly, by tilting the irradiation optical axis of the polychromatic light S1 from perpendicular to the pellicle, the specific wavelength λm changes, but as the inclination of the irradiation optical axis increases, the foreign matter on the pellicle surface is irradiated. There is a difference between the beam intensity and the beam intensity that irradiates the foreign matter on the back surface of the pellicle due to the dependence of the pellicle transmittance on the angle of light incidence, and the spectral characteristics of the irradiation beam that penetrates the back surface may change. For this purpose, it is preferable that the irradiation axis of the polychromatic light (white light) Sl be close to perpendicular to the surface to be inspected.

Here, to give an example, the thickness d of the pellicle is 1 μm.
, when the refractive index n is 1.5, the scattered light reception angle θ2 is 80
°, the specific wavelength λ that becomes the peak from the above equation (4)
m is λm! :i 2.267 m (where m is an integer)・
Old... (5). Assuming that the peak wavelength λm appears in the near-infrared region from the visible region to the wavelength of 1100 On or less,
λ as m-5, = 452 nm, λ4-5 as m=4
65 nm, and m=3, λz=753 nm.

Similarly, if the scattered light reception angle θ2 is 506, the peak wavelength λm is λm#2.58/m (where m is an integer)...
6). Within a similar wavelength range, λ with m=6.

=430nm, m=5, λs=516nm, m=
4 as λ4 = 645 nm, m = 3 as λ, = 860
It becomes rv.

Now, change the wavelength range from 400nm to 900nm every 100ns by 40 (1-500rv+, 500-600nm, 6
00~700nm, 700~800ne, 800~9
When dividing into 0Qnm, θ2 for 400-500nm
-80a, λs"452nm, θ,=50', λ-
=430nm appears and at 500~600n+1 θ, =
λ4 = 565ns at 80', λ5 at θ2 = 50°
=516rv+ appears. However, in a light receiving system with 600~b θ2=80°, an integer m that satisfies equation (5)
does not exist, that is, in the wavelength range of 600 to 700 ns+, the back surface foreign matter scattered light is not received.On the other hand, in the light receiving system with θ2=50°, in this same wavelength range, λn=645rv. The same goes for 700-800nm, 800-900nm
This also occurs for the wavelength range of ne. 700-800n11
In the wavelength range of , λt=753n appears when θz=so@, and does not appear when θ2=50°. 800~900ns
It does not appear for θ2=80° in the wavelength range of θ,=
For 50'', there are λ5=860n seagulls.

As mentioned above, different scattered light reception angles (in the above example, θ2=8
0° and θ2=50°), a phenomenon occurs where one light receiving system can receive the light but the other light receiving system cannot, depending on the wavelength range.

On the other hand, the surface of pellicle 2 (the side irradiated with polychromatic light)
When a foreign object adheres to a surface, the foreign object scattered light enters the receiving system directly without passing through the beam, so the two receiving systems with different acceptance angles do not depend on the wavelength range, and the surface foreign object scattered light is at the wavelength of the polychromatic light. Light can be received with the same distribution characteristics.

Therefore, when receiving scattered light from a foreign object attached to the front and back surfaces of a pellicle at two different acceptance angles, and dividing the light into appropriate wavelength ranges, we can compare the amount of light received in the same wavelength range. It becomes possible to determine whether the foreign matter is attached to the front surface or the back surface of the pellicle.

Note that the system for detecting scattered light at two different acceptance angles is used here as an example of two angles θ2 - 80° and 50°, but the point is that based on equation (4) above, The angle can be set at an angle that provides good performance, and it is preferable to adjust the angle to the optimum angle depending on the wavelength characteristics of the illumination light used, the thickness of the pellicle, etc.

〔Example〕

FIG. 1 shows the configuration of an inspection apparatus according to a first embodiment of the present invention, in which the light source 21 is a white light source such as a tungsten lamp or a halogen lamp. It is assumed that illumination light extending to an infrared region of about 11,000 nm is used.

Illumination light from the light source 21 enters the condenser lens 22 . The optical axis of the condensing lens 22 is connected to the pellicle 2 stretched over the reticle 1.
It is set perpendicular (or almost perpendicular) to the zero plane, and focuses the illumination light within a local area (for example, 1 m square) of the pellicle 1.

At this time, it is preferable to provide an illumination field stop (aperture) at a position conjugate with the pellicle 2 in the illumination optical system so that the local illumination area on the pellicle is shaped into a clean rectangle, a minute slit, or a circle.

On the other hand, the first light receiving system among the scattered light receiving systems includes a condenser lens 25 having an optical axis inclined at an angle θa with respect to the normal to the pellicle 2, and looks into the illumination area of the pellicle 2.

Here, the angle θa is, for example, θa=Bo''.

Now, a part of the scattered light from the foreign object passes through the lens 25 and is split into light in two wavelength ranges by the dichroic mirror 27A, and the scattered light in the wavelength range reflected by the dichroic mirror 27A is received by the photoelectric converter 28A. Ru. The scattered light in the wavelength range that has passed through the dichroic mirror 27A is further divided into two wavelength ranges by the dichroic mirror 27B.

The scattered light in the wavelength range reflected by the dichroic mirror 27B is received by the photoelectric converter 28B, and the scattered light in the wavelength range transmitted through the dichroic mirror 27B is received by the photoelectric converter 28C.

The second light receiving system among the scattered light receiving systems includes a condenser lens 26 having an optical axis inclined by an angle θb (θb × θa) with respect to the normal line of the pellicle 2, and anticipates the illumination area of the pellicle 2. . Here, the angle θb is, for example, 50°. Scattered light from a foreign object is received with the same configuration as the first light receiving system.

That is, part of the scattered light from the foreign object is divided into two wavelength ranges by the dichroic mirror 270 via the lens 26, and the scattered light in the wavelength range reflected by the dichroic ink mirror 27D is received by the photoelectric converter 28D. The scattered light in the wavelength range that has passed through the dichroic mirror 27D is further divided into two wavelength ranges by the dichroic mirror 27E.

The scattered light in the wavelength range reflected by the dichroic mirror 27B is received by the photoelectric converter 28E, and the scattered light in the wavelength range transmitted through the dichroic mirror 27E is received by the photoelectric converter 28F.

In this embodiment, the dichroic mirror 27 of the first light receiving system
A, 27B and the dichroic mirror 21 of the second light receiving system
0 and 21E have the same wavelength selectivity. For example, the dichroic mirrors 27A and 27D are cold mirrors with a boundary wavelength of 700 nm (reflecting the short wavelength side and transmitting the long wavelength side), and the dichroic mirrors 27B and 27E are cold mirrors with a boundary wavelength of 700 nm. A cold mirror with a boundary wavelength of 800n+m is used.

Although not shown, the wavelength band of the illumination light S1 is limited in advance to 600 to 900 nm by an appropriate filter.

At this time, photoelectric conversion? The magnitudes VA and V* of the output signals 528A and 28D correspond to the total amount of scattered light whose wavelengths are distributed between 600 and 700 n- among the scattered light from the foreign object (pellicle irradiation area).

Furthermore, the magnitude V of the output signals of the photoelectric converters 28B and 27E
The IVE depends on the total amount distributed in the wavelength range of 700 to 800n-, and the magnitudes of the output signals Vc and Vr of the photoelectric converters 28C and 28F are 800 to 900nm.
It depends on the total amount of scattered light distributed in the wavelength range of .

Therefore, in this example, two types of guikuro ink mirrors,
In other words, 27A, 27D, 27B, and 27E divide the wavelength distribution of scattered light into three wavelength ranges (600 to 700 nII+, 7
00 to 800nI++, 800 to 900nm), as well as functioning as a spectroscopic means for dividing the wavelength into wavelengths of 00 to 800nI++, 800 to 900nm), as well as gicroic mirrors 27A, 27B, photoelectric converters 28A, 28B, 28
C constitutes a first photoelectric detection means, and photoelectric converters 27D, 27F, and photoelectric converters 28D, 28E
, 28F constitute a second detection means.

Now, FIG. 3 shows photoelectric converters 2OA, 28B, 28C128D, 28B, which individually receive scattered light for each specific wavelength range.
An example of a processing circuit that evaluates each signal output of 28F is shown.

In this embodiment, in order to simplify the explanation, it is assumed that the reticle 1 with a percle is placed on a two-dimensional scanning stage 40 and moves in the X and X directions with respect to the irradiation beam. In addition, the movement of the scanning stage 40 is performed using coordinate position measurement (encoder, etc.) 4.
2, it is measured with a resolution finer than the size of the local illumination area.

In FIG. 3, the processor 44 outputs a movement 1 command to the stage controller 46. The stage controller 46 uses the position information from the encoder 42 as a feedback input to control the motor 48 to move the stage 40 two-dimensionally. The position information of the encoder 42 is input to a map coordinate creation circuit 50 that converts the position of the foreign object so that it can be displayed on a 11 square or 5 m square map.

Each photoelectric converter 28A, 28B, 28C, 28D28E,
Each output signal level of 28F is determined by the amplifiers 60A, 60B,
After being amplified by 60C, 60D, 60E, and 60F, the signals are input to dividers 1i61a, 61b, and 61c. Although division is performed in an analog manner here, division may also be performed using a processor program.

The dividers 61a, 61b, and 61c perform division processing between the output values of the photoelectric converters that receive light in the same wavelength range in the first light receiving system and the second light receiving system.

That is, for scattered light with a wavelength of 600 to 700 nm, a signal vA output from the photoelectric converter 28A and amplified by the amplifier 60A, and a signal VD output from the photoelectric converter 28D and amplified by the amplifier 60D. It is input to the divider 61a, and the divider 61a calculates the ratio 5a=VA/V. Output the value of .

Similarly, for scattered light in the wavelength range of 700 to 800 nm,
The signal VB from the photoelectric converter 28B and the amplifier 60B and the signal ■ from the photoelectric converter 28E and the amplifier 60E are divided by the divider 60b into a ratio 5b=v.

/ VE calculation is performed, wavelength range 800-900n
For scattered light of m, photoelectric converter 28C, up 60
Signal VC from C, photoelectric converter 28F, amplifier 60F
The signal V from
/Vy is calculated.

The respective division outputs Sa, Sb, and Sc are directly converted into digital rays by analog-to-digital converters (A/D) 62a, 62b, and 62C, and stored in the memory 52 via the processor 44.

The display 54 displays the inspection results using a color cathode ray tube. Based on the information from the map coordinate creation circuit 50, the display 54 displays the entire surface of the pellicle 2 as a grid map of 1 layer square or 5 meters square, and shows the detected foreign matter on the surface. If it is on the side, the area of 1 square or 5 ms corresponding to the location is filled in green, for example, and if it is on the back side, it is filled in red. Further, the size of the detected foreign object is classified into about three ranks, and characters of, for example, A rank, B rank, and C rank are displayed at the same time. The rank display may be expressed by the gradation (luminance) when filling in green or red, or may be expressed by slightly changing the tone. Alternatively, a character may be displayed superimposed on the filled-in area.

Now, in actual inspection, as shown in detail in steps 100 to 136 in FIGS. 5(A) and 5(B), after moving the stage 40 one-dimensionally in the X direction, the illumination local area is moved in the X direction. Stepping by the size of , and moving in the X direction again are repeated (steps 100~
1o4).

The processor 44 responds to a sampling command output from the map coordinate generation circuit 50 each time the stage 40 moves by, for example, 1ffI11, and controls the A/D 62a,
Each output value of 62b and 62c is stored in the memory 52 (steps 106 to 110).

After the scanning of the stage 40 is completed (steps 112 and 114), the processor 44 reads the inspection data (Sa, Sb, Sc) for each scanning position (sampling position) from the memory 52 (steps 116 and 118). Also, the memory 52
for each wavelength range (600~700n+a, 700~800n+a,
(nm, 800 to 900 ns) ratio constants α, β, and T are determined in advance through a predetermined experiment or the like and are stored.

In this example, the scattered light from the back surface foreign matter is in the wavelength range 600~
At 700n-, only the photoelectric converter 28D of the second light receiving system detects it, and the photoelectric converter 28A of the first light receiving system does not detect it, so that the ratio 5a=Vs/Vn satisfies Sa<α with respect to the constant α.

Similarly, the wavelength range 700 to 80 of the light scattered by foreign objects on the back surface is
The scattered light of 0 nm is detected by the photoelectric converter 28B of the first light receiving system, but is hardly detected by the photoelectric converter 28E of the second light receiving system. Scattered light in the wavelength range of 800 to 900 nm is detected by the photoelectric converter 28F of the second light receiving system, but not detected by the photoelectric converter 28C of the first light receiving system, so 5c=
Vc/V becomes <7.

Therefore, when Sa<α, sb>β, and Sc<7 (algorithm A) are satisfied, it is determined that the foreign substance is on the back side of the belter, and when this logical formula is not satisfied, it is determined that it is attached to the surface (step 120.112.126)
.

Or, by comparing the three values of Sa, Sb, and Sc, Sa<
It is also effective to create a logical formula such that if Sb>Sc (algorithm B), it is determined that there is a foreign object on the back side, and if not, it is determined that it is a foreign object on the front side (steps 120, 124, and 126).

This determination process is sequentially performed by the processor 44 based on the information for each map position read from the memory 52 (steps 128, 130, 132, and 134), and the results are displayed on the display 54 (step 136).

Furthermore, the processor 44 ranks the size of foreign objects based on the magnitude of the photoelectric signal level, and displays the results on the display 54. Photoelectric signal level V4, V1
+, Vc, VD, VE, and Vr are respectively connected to lamps 60A, 60B, 60C, and 60D by routes not shown.
, 60E, and 60F to the processor 44, and the pro-sensor 44 ranks the foreign particles according to their sizes based on, for example, the maximum value of the photoelectric signal level.

Further, when determining the foreign object size based on the photoelectric signal level, since six photoelectric converters 28A to 28F are provided in this embodiment, it may be defined by the algebraic sum of these six signal levels. Alternatively, the light i! of the receiving system having a larger angle with respect to the plane of speckle 2! converter (here 28
D, 28E, 28E) may be defined by an algebraic sum of signal levels. This is due to the phenomenon that in a light receiving system that has a large angle with respect to the pellicle surface, at least one of the three photoelectric converters always receives the scattered light from the foreign object on the back surface of the pellicle. It is something.

In the above explanation, the constant α used in algorithm A,
β and T are determined as follows, for example.

First, an inspection tool is prepared, in which the upper surface of the pellicle 2 is sprinkled with standard microparticles (such as true spherical beads) in place of foreign particles. Then, using this inspection tool, foreign matter inspection is performed using the apparatus shown in FIG. At this time, each photoelectric converter 28 is irradiated with the beam S1 to a standard particle whose particle size is known.
The levels of the amplified signals ①, ~V, of A, 28B, 28C, 228D, 28E, and 28F are measured. From the measured values, α-(VA/Vo)・Kα, β-(V.

/Vt)・Kβ,α−(Vc/■F)・KT
, β, and γ. Here, α, Kβ, KT, are
Considering margins related to the orientation of the inequality sign to the algorithm, the constants are set to Kα>1, Kβ<1, and K7>l.

Although the first embodiment of the present invention has been described above, several other modifications are possible, and these modifications will be described below.

First, in the embodiment shown in Fig. 1, the illumination light is used as a spot light, and the entire surface of the pellicle is inspected by moving in the X direction and the If the pellicle is moved in only one direction and a -dimensional linear sensor or the like is used as the photoelectric converter of the first light receiving system and the second light receiving system, the inspection time can be significantly shortened. An example of such a configuration is shown in FIG. 6 as a second embodiment.

The polychromatic light S+ (here, it is assumed to be a parallel light beam) is expanded in the X direction by a cylindrical lens (concave) GL, and then expanded in the -dimensional direction by a cylindrical lens (convex) GLt having a generatrix extending in the X direction. The light is focused on the strip-shaped illumination section BA. The reticle 1 with a pellicle is scanned one-dimensionally in the X direction as indicated by an arrow 32. The illumination part BA has a length that almost covers the width of the entire surface of the pellicle 2 in the X direction,
The width in the X direction is set to be variable depending on the required thinness (for example, IM) on the map.

The optical axis AXo of the irradiation optical system of the polychromatic illumination light S is substantially perpendicular to the surface of the pellicle 2. In addition, cylindrical lens G
L may be a normal spherical lens system.

In this case, it is preferable that the front focal point of the spherical lens system coincides with the virtual beam divergence point of the cylindrical lens G I-+, and the pellicle 2 coincides with the rear focal plane. Now, a line l extending in the X direction on the surface of the pellicle 2 passes through the center of the illumination part BA and is almost perpendicular to the illumination part BA, and the optical axis AXa of the first light receiving system is folded back by the mirror MR. Then, the angle θα (θα=906−
It is tilted by θa). Also, the optical axis AXb of the second light receiving system
is the angle θβ (θβ=90°θb
) is only tilted. The imaging optical system (condensing lens) 25 of the first light receiving system collects the dark field image of the irradiation unit BA through dichroic mirrors 27A and 27B, respectively, using three one-dimensional linear sensors (CCD, photodiode array, etc.). )
Images are formed on 30A, 30B, and 30C.

Similarly, for the second light-receiving system, the imaging optical system (condensing lens) 26 collects the dark-field image of the irradiation unit BA through dichroic mirrors 270 and 27E similar to those shown in FIG. Dimensional linear sensor (not shown in Figure 6)
image on top.

The pellicle 2 that is currently in wide use has dimensions that are circumferentially smaller than a reticle (5 inches or 6 inches) for reduction projection exposure.

Therefore, even if the length of the illumination part BA in the X direction (the effective width of the pellicle 2) is assumed to be about 15 cm at most, when detecting with a resolution of 1 mm square, the number of arrays (number of pixels) of the one-dimensional linear sensor is: 200 is enough.

In the case of such a configuration, one-dimensional image signals are simultaneously read out from each one-dimensional linear sensor each time the reticle 1 (pellicle 2) is moved in the X direction at a substantially constant speed, for example, every 1 m, as shown in Fig. 3. The ratio of the amount of received light may be determined for each pixel using a circuit similar to that shown in FIG.

Now, FIG. 7 shows the configuration of an inspection apparatus according to a third embodiment of the present invention, and parts having the same effect as those in FIG. 1 or FIG. 6 are given the same reference numerals.

Here, the first light receiving system (mirror MR, condensing lens 25
, dichroic ink mirrors 21A, 21B, and photoelectric converters 28A, 28B, 28C), the beam irradiation part is viewed from the right side in the figure at an angle θa, and the second light receiving system (
Condensing lens 26, dichroic mirrors 27D, 27E
, and the optical axis AX of the photoelectric converters 28D, 28E, 28F)
b is arranged at an angle θb so that the beam irradiation part is viewed from the left side in the figure. In this way, if the arrangement of the first light receiving system and the second light receiving system is made to be different from each other when viewed from the plane of the pellicle 2, the arrangement of the two light receiving systems will be extremely easy. , it is possible to distinguish between the front and back sides of a foreign object with the same accuracy.

In addition, in FIG. 7, the polychromatic illumination light S1 is
Aperture) AP is illuminated with −-like intensity. The illumination light S passing through the aperture AP is transmitted through the lens system GL) and the beam splitter NBS to the condensing lens 22 for irradiation.
is incident on the pellicle 2, and the image of the aperture AP (rectangular,
The image is formed as a circular or slit-like shape. A part of the illumination light St' transmitted through the beam splinter NBS enters a reference light receiving system for monitoring intensity fluctuations of the light source and fluctuations in wavelength distribution. The reference light-receiving system has the same spectral characteristics as the first and second light-receiving systems, and has the same wavelength characteristics as the first and second light-receiving systems.
Illumination light S,
It is configured to constantly measure the light intensity of 1.

FIG. 8 shows the configuration of an inspection apparatus according to a fourth embodiment. Unlike each of the embodiments described so far, by devising the method of sending the illumination light of the pellicle 2, the first light receiving system and the second This configuration eliminates the need to provide a spectroscopic element (dichroic mirror, etc.) in each of the light receiving systems, and requires only one photoelectric converter (photomultiple, one-dimensional linear sensor, etc.) for each light receiving system. In FIG. 8, light sources 21A, 21B,
Both of the 2 ICs are composed of light emitting diodes, anticonductor lasers, etc., and the wavelength ranges of the respective emitted lights are made to differ according to the spectral characteristics (same as those shown in FIG. 1) of the dichroic mirrors 27A and 27B. Three light sources 21A, 21
The illumination lights from each of B and 21G are reflected by the beam splinter NBS along the same optical axis AXo, and are focused on the pellicle 2 by the condensing lens 22. The first and second light receiving systems are fast response type photoelectric converters (Photomaru etc.) 32A,
32B, and the photoelectric signals V ia and V bb are input to the inspection processing circuit 72 . The processing circuit 72 has a ratio (V, ,
/V-b), an A/D converter with sample and hold for digitally converting the ratio, a processor, memory, etc. are incorporated.

Now, are the three light sources 21A, 21B, and 21C controlled by the timing control circuit 70 to emit pulsed light at high speed and selectively? 'n, and the signal of each light emission timing is sent to the processing circuit 72.

In such a configuration, for example, when the optical axis AXo comes to one map coordinate position on the pellicle 2, the light sources 21A,
21B and 21C sequentially emit pulse light. Each pulse emission is performed so that they do not overlap with each other in time, but rather with a slight lag time. The processing circuit 72 activates the sample/halt function every time one pulse is emitted, and sequentially stores the output value of the A/D converter at a designated address in the memory. In other words, the ratio (Van/Vbb) obtained when one area (for example, 1M square) on the map is illuminated with pulsed light from the light source 21A.
The value Sa, the ratio value sb obtained when the same area is illuminated with the pulsed light of light g21B, and the ratio value sb obtained when the same area is illuminated with the light source 2
The ratio value Sc when illuminated with 1C pulsed light is stored at a designated address on the memory. Then, when the illumination area moves to the adjacent area, the three light sources 21A are connected in the same manner again.
, 21B, and 21C sequentially emit pulse light. Once the measurements have been completed for everything within the designated area on the pellicle 2, the inspection (evaluation) is then carried out in exactly the same manner as shown in FIG. 5(B).

In this embodiment, since it is necessary to sequentially emit light from three light sources that emit light in different wavelength ranges, the inspection operation time may be longer than in the previous embodiments. , the configuration of the light receiving system is extremely simple,
This has the advantage that the scale of the processing circuit can be small.

The embodiments of the present invention have been described above, but as illumination light, light with multiple bright line spectra such as a mercury discharge lamp may be used, or light emitting diodes (or semiconductor lasers) with different center wavelengths may be used. Light from multiple pieces or SH
It is also possible to use light obtained by coaxially combining harmonic light that has passed through an O-crystal through a beam splinter. The guichroic mirror may be replaced by another color filter prism as a wavelength selection element used in the scattered light receiving system.

By the way, as described in detail of the present invention, the specific wavelength λm of the scattered light from the foreign matter on the back side of the pellicle exists at the thickness d and the refractive index n of the pellicle according to equation (4). Therefore, for pellicles of various thicknesses and refractive indexes, two (2)
By determining the specific wavelength based on 4), and optimizing the selected wavelength by changing the angles θa and θb of the two light receiving systems as appropriate each time, or by replacing the micro ink filter, various pellicles can be used. It is also possible to determine whether the front or back sides are the same.

[Effects of the Invention] As described above, the present invention not only detects the presence or absence of defects such as foreign matter attached to a thin transparent object such as a pellicle, but also
It is also possible to determine whether the defect is attached to the front or back surface of the transparent body, and the occurrence of defects in the lithography process can be prevented.

Furthermore, if this inspection device is used in conjunction with an automatic pellicle pasting device, it is possible to check for foreign matter on the back side of the pellicle while the pellicle is temporarily attached to a mask or reticle, and if there is no foreign matter on the back side, the final pasting can be carried out. It is also possible to completely automate a series of operations such as removing the temporary pellicle and replacing it with another pellicle if there is a problem.

In addition, the present invention can be applied not only to the inspection of relatively thin glass substrates and phosphorography materials such as membrane masks for X-ray exposure, but also to the defect inspection of thin films for medical and physical chemistry applications where contamination with foreign matter is avoided.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the configuration of a defect inspection apparatus according to a first embodiment of the present invention, FIG. 2 is a diagram illustrating details of the present invention, and FIG. 3 is a diagram showing a signal processing system in the first embodiment. Block diagram showing the configuration - Figure 4 is a diagram explaining the conventional technology, Figure 5 (A) and Figure 5 (B) are flowchart diagrams explaining the operation of the first embodiment, and Figure 6 is a diagram explaining the FIG. 7 is a perspective view showing the configuration of a defect inspection device according to the third embodiment; FIG. 8 is a perspective view showing the configuration of the defect inspection device according to the fourth embodiment. It is a diagram. (Explanation of symbols of main parts) 1...Reticle 2...Pellicle 12...Foreign object 21.21A, 21B, 2IC...Light source 22.
......Irradiation condensing lens 25.26... Light receiving condensing lens 27A, 27B, 27D, 27E... Gicroic mirror 28A, 28B, 28C128D, 28E, 28F ,3
2A, 32B...Photoelectric converter 30A, 30B, 30C
... One-dimensional linear sensor 44 ... Processor 54 ... Display 61a, 61b, 61 c - Divider S1 ... Multicolor illumination light S, , S, ... ...scattered light

Claims (4)

[Claims] (1) In an apparatus for inspecting defects such as foreign matter existing on the front and back surfaces of the flat support object by illuminating a light-transmitting flat support object and photoelectrically detecting optical information generated from the illumination part, a predetermined irradiation means for irradiating the planarized object with polychromatic light having an intensity distribution over a wavelength band; scattering light generated from defects in the irradiation part of the polychromatic light to a predetermined surface of the planarized object; a first light-receiving system that receives light from an angular direction; a second light-receiving system that receives the scattered light from an angular direction different from that of the first light-receiving means with respect to the surface of the flat object; a first photoelectric detection means for separating the scattered light with predetermined spectral characteristics and individually photoelectrically detecting the amount of light for each specific wavelength range; a second photoelectric detection means that performs spectroscopy with substantially the same characteristics as the photoelectric detection means and photoelectrically detects the amount of light in each specific wavelength range; an output signal from each of the first photoelectric detection means and the second photoelectric detection means; Determine the size ratio for each specific wavelength range, and determine which side of the front and back surfaces of the planarized object the defect is present based on the magnitude relationship of the ratio between mutually different specific wavelength ranges. What is claimed is: 1. A defect inspection device comprising: determination means for determining. (2) The irradiation means has a continuous broad wavelength band;
The device according to claim 1, further comprising a single light source that emits light in a plurality of discrete emission line spectra. (3) The irradiation means has a plurality of light sources that emit light at different center wavelengths, and the lights from the plurality of light sources are coaxially combined and directed toward the flat object. The device described in (2). (4) Each of the first photoelectric detection means and the second photoelectric detection means includes a wavelength selection element that separates the scattered light into each of the specific wavelength ranges, and an amount of light in each wavelength range separated by the wavelength selection element. 3. The device according to claim 1, further comprising a plurality of photoelectric conversion elements that individually receive light.