JPH01201143A - Method and device for detecting foreign matter - Google Patents

Abstract

PURPOSE:To detect extremely small foreign matter on a rugged protection film by projecting light with specific wavelength on a sample which has the protection film on a circuit pattern and detecting the foreign matter on the protection film with diffracted light from on the protection film. CONSTITUTION:When the circuit pattern 103 which is applied with the organic protection film 104 is irradiated downward with the light 203b of <=380nm in wavelength from a laser oscillator 14, light 203b which strikes the organic protection film 104 is absorbed by the organic protection film 104 and no scattered light is generated, but light 203b which strikes on the foreign matter 5b generates scattered light 205b, which is converged by a scattered light detection system 3 and detected by a photoelectric converting element 302b to detect the extremely small foreign matter 5b. Further, regularly reflected light 206 and diffracted light 207 which causes misdetection are interrupted by a light shielding plate 441 and do not enter an integrating sphere 301b, so that only foreign matter scattered light 205b is detected without being affected by the ruggedness of the surface of the organic protection film 104.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to the inspection of foreign matter on a mask used for exposure of cattle bodies, etc., and is sometimes suitable for detecting minute foreign matter on a mask for X-ray exposure. The present invention relates to a foreign object detection method and device.

[Conventional techniques]

What is the first rice promotion technique used for detecting minute foreign objects using spun ball gold? Devices for performing this are known. This is a wavelength of 488 nm or 7
An 80-nm laser is used to scan a spot on the surface of the particle, and it is detected by the total integration of the scattered light generated from the foreign object.

Ma'! 'C The second prior art is JP-A-59-1863.
No. 24 is known.

In this prior art, a method of obliquely irradiating a laser is used to detect only foreign matter without being affected by the circuit pattern on the mask.

[Problem to be solved by the invention]

In the first conventional technique, the wavelength of the illumination light is shortened to reduce the spot diameter that scans the entire wafer.
Although it is possible to detect minute foreign matter of 1 to 0.2 μm, it is not applicable when there is an uneven circuit pattern on the wafer surface.

However, even using the second conventional technique, the minimum detectable foreign matter is 2 μm, and foreign matter smaller than this cannot be detected. Furthermore, no consideration is given to surface irregularities.

The purpose of the present invention is to solve the above-mentioned problems by providing a method and apparatus for detecting extremely small foreign objects, which are capable of detecting minute foreign objects even if unevenness occurs in the protective film of the circuit pattern or the film that prevents the adhesion of foreign objects on the surface. be.

Another object of the present invention is to protect the circuit pattern with its unevenness by forming a protective film on the circuit pattern like an X-ray mask! An object of the present invention is to provide a foreign matter detection method for an X-machine mask that can detect foreign matter existing on a protective surface, and its VC direct method.

[Ninth means to solve the problem]

The present invention is to irradiate a sample having a protective film on a circuit pattern with light of a constant wavelength and detect foreign matter on the protective film using diffracted light from the protective film.

Another object of the present invention is to detect foreign matter using a detection system using only an integrating sphere when there is no unevenness on the surface of the protective film.

Furthermore, in the case where the surface of the a-retaining film has irregularities, a light-shielding plate is inserted into the integrating sphere to separate the low-order diffracted light generated by the surface undulations that causes the detection from the scattered jYS from the foreign object, and the light shielding plate is inserted into the integrating sphere to separate the scattered jYS from the foreign matter. The purpose of this system is to detect foreign substances.

[Effect]

The source of the irradiated wavelength in a specific frequency range is absorbed or reflected by the N-type protection film and does not reach the circuit pattern. Therefore, light scattered by the circuit pattern is not detected.

On the other hand, if there is a foreign object on the organic protective film, the irradiated light will be strongly scattered by the foreign object, so it is possible to detect the foreign object by constantly detecting the scattered light from the surface of the protective film.

Here, if the surface of the organic protective film has irregularities, regular reflection light and diffracted light from the irregularities are detected together with light scattered by foreign objects. As a result, it is impossible to distinguish between foreign objects and irregularities, leading to public prosecutors' investigations. Therefore, if you detect it within the Brewster angle or use an integrating sphere with a light shielding plate that blocks specularly reflected light and lower-order diffracted light from the unevenness, which may cause false detection, only the light scattered by the foreign object can be detected. It becomes possible to detect.

[Example of plagiarism]

Examples of the present invention will be described below. FIG. 1 shows the structure of the X-ray mask 1, illumination, and integrating sphere detection thread after coating with a protective surface film. X Gan mask 1 is as shown in the 4th episode < , S
- a support material 101 formed in a frame shape from materials such as -, a base material 102 made of boron glide (BN), silicon nitride (S's N4), etc., a circuit pattern 103 made of Au, and a modest suppurative membrane. (For example, polyimide)
-indroquinazolinedione))1
It consists of 04.

Here, in the supporting material 1011Qll, the thickness of the base material 102 is determined to be sufficiently thick, and there are no surface irregularities on the base material. Therefore, on the base material side, the element 5α scattered from the foreign object is collected by the detection system 2 consisting only of the integrating sphere 301Z, and is received by the element 1c variable element 502α.
A detection signal 303α is output to perform foreign object detection.

104 is an organic film coated on the circuit pattern 103; 12 is a holder portion 11 held by the mask 1; 203α and 205b are nine stages; 203α and 205b are laser beam oscillators 14;
15α, 15b are beam expanders, 16Q, 1
6b is a condensing lens, 17α, 17b is a motor 20α,
The culver mirror is passively moved by 20M, 2.3 is the scattered light detection system, 20 is the condensing point, 13 is the movement direction of the stage 12, 111.21 is the original scanning direction, 2054.205bU
Different! It shows the daring death from vI5. 19 is 380n
It is a half mirror that branches out 18 laser sources of less than m.

A polyimide film was used as the organic protective film 104.

The spectral transmittance of a polyimide film is clearly shown in Figure 3, where the growth (nm) and transmittance are shown on the vertical axis and the transmittance, respectively. have. On the other hand, the transmittance of the polyimide film is close to 100% for even shorter wavelengths (1 to 20 nm) such as X-rays.

Therefore, if a polyimide film is applied as a patterned film 104 on the Xi mask as shown in FIG. 2, the foreign matter 5 in 9 will adhere to the polyimide film. When inspecting foreign substances, we use 203b
When irradiated from above, the multiplication element that hits the polyimide film is absorbed by the polyimide odor and does not produce scattered light, but the t element that hits the foreign substance 5 on the polyimide film produces scattered light 205b, so the scattered light 205b'i It is possible to detect foreign matter by simply detecting it with the scattering source detection system 5.

There is mFJ like this! Mask 1 coated with %104 is 4
As shown in FIG. 4, it is set on a stage 12 that moves in the -axis direction, and is moved in the direction of the arrow of the moving direction 13. - Laser light 18 with a wavelength of 380 nm or less from the laser generator 14
The diameter of the beam expander 15α, 15b't' is expanded, and the beam is further focused as a laser spot by the base lenses 16α, 16b. And Calbamirror 17α, 17
b, the laser spot is dug in the scanning direction 21. As a result, the laser spot scans the entire surface of the circuit pattern area on the substrate side and the organic protective film side of the mask 1, so that the scattered light 205d and 205b are focused by the scattered light detection system 2.6, and the photoelectric conversion element 302α, By detecting with 302b, minute foreign matter 5 can be detected.

Next, the thickness of the organic protective film 104 of the X-ray exposure mask will be explained. That is, let the light reflected and scattered from the circuit pattern 103 of the mask without and with the organic protective film be I, , I, respectively, and the incident light be I. In this invention, the film thickness of the organic protective film is defined as the difference between the transmittance T of the organic protective film at the wavelength of 525 nm and the thickness of the organic protective film. Since there is a relationship of T = 1 g 3.0', an organic protective film is required for the circuit pattern 103, but since the incident light travels back and forth within the organic protective film, the required thickness of the organic protective film is This means that the thickness may be 0.5 μm. Therefore, in order to reduce the scattered light i to 10-'' or less, the minimum thickness of the organic protective film must be at least μs μm.However, in order to protect the circuit pattern 103, this film thickness is Figure 5 is an explanatory diagram of an X-ray exposure mask. In this X-ray exposure mask, the mask 1 is made of, for example, boron nitride (BN).
, a substrate 102 made of silicon (S), and a frame 101b made of, for example, silicon (SQ). For example, a circuit pattern 103 made of gold (Au) having a thickness of approximately 1 μm is formed on the organic protective film 104α through which the wire is passed, and an organic protective film 104b through which the X-metal metal is passed is further formed on the circuit pattern 106. A layer of about 5 μm is applied.

The XdJI source mask configured in this way is irradiated with inspection light 203α, 203b'ji of 3130 nm or less from both the substrate 102 side and the opposite side to remove foreign particles 5 on the mask 1 in the same manner as in the above embodiment. An inspection will be carried out.

In the above example, an example using an XM exposure mask coated with an organic protective film that absorbs light is explained.
The mask is not limited to the Xi exposure mask as long as it acts on the mask. It is clear that the same effect can be obtained in a conductive element or the like having a circuit pattern and an organic protective film thereon.

As described above, it is possible to detect minute foreign objects of 0.15 Am or less, which was previously impossible, without being affected by the circuit pattern. Removal of foreign matter by cleaning or the like becomes an effective method, and as a result, it is possible to process the product without foreign matter being layered, which greatly contributes to the yield of LSI.

By the way, since there are four organic protective films 104 on the circuit pattern side, unevenness occurs on the surface of the organic protective film due to the step difference in the circuit pattern 1030. As shown in FIG. 6, the foreign matter scattered light 205b from the foreign matter 5b, the surface unevenness specular reflection light concave 6 and the diffraction jt,
207 all mixed into the integrating sphere 301b, and the detector 302b
It is impossible to distinguish between irregularities and foreign objects.

Next, the pre-aster angle F4@bright detection method will be explained.

FIG. 7 shows the X-ray mask 1 with an organic protective film 104 formed thereon, illumination, and detection method. As shown in the figure, the X-ray mask 1 is composed of a support material 101, a base material 102, a circuit pattern 105, and an organic protection material 111104.

Here, on the supporting material 101 side, since the thickness of the reference material 102 is sufficiently thick, there is no surface unevenness of the base material. Therefore, it is possible to perform all foreign matter detection using epi-illumination S2 gold on the base material side.

On the other hand, on the organic protective film side, since the organic protective film is wide, unevenness occurs on the organic film surface due to steps in the circuit pattern.

However, by performing illumination detection at the Brewster angle at the P boundary according to the present invention, the specularly reflected light due to surface irregularities can be reduced to almost zero, and only the scattered light of foreign matter can be extracted. The principles behind VC will be explained below.

As shown in Fig. 8, there is a hole in the shed with different refractive index.
C, when the original is incident, the intensity of the reflected light 8 is the angle of incidence s'
('t) depends. Placement E of incident light 6 of P1M light
,, assuming that the refraction angle 7 R2, the refractive weight n of section member 4, and the refractive index k n' of section member 5, the ratio of Ep and R1 is derived from Fres's formula, where n (n').For details, see Yogengaku' P146-P149
It is described in

Therefore, when P-polarized illumination is performed, the refractive index n' of the organic protective film 109 is 18, so using equation (1), E
When the ratio of p and R1 is calculated, Figure 9 can be seen. From the figure, when -=si°, the ratio of the angle becomes zero. 61° again
Within the range of ±5°, the ratio tO of Ep and Rp can be suppressed to 5% or less.

Therefore, if we use a refractive index of n' == 1.8, then
When the irradiation angle of the P-polarized illumination is kept at 61°, foreign object scattered light can be detected without being affected by the unevenness of the organic protective film 104.

An embodiment of the present invention is shown in FIGS. 7 and 10.

The mask 1 having an organic protective film formed thereon is supported by a holder part 11 and scanned in the direction of an arrow 13 by a uniaxial stage 12 capable of double-sided inspection. On the other hand, the illumination light uses an element 18 with a wavelength of 380 nm or less from the Leb oscillator 14, and the beam diameter is expanded by the beam expander 15b, and the beam diameter is expanded by the condensing lens 16.
b, Pm original laser source 203Ck point 2 at Brewster angle 304 or less via Pleaster angle illumination mirror 22
The light is focused to 0. A galvanometer mirror 17b is provided between them, and the point 20 is directed in a direction Km perpendicular to the arrow 13. As a result, the point 20 is scanned over the entire surface of the mask, so if the scattered light 306 is detected by the condenser 301C and the detector 602C in synchronization with the scanning, the device can detect minute foreign particles without being affected by the unevenness of the surface of the organic protective film. All can be achieved. In short, an organic protective film 1 with unevenness 9 due to Prusster angle illumination detection source school thread 6α
04 can be detected.

On the other hand, if the Brewster's angle illumination detection method shown in FIG. 7 is used, if the P-polarized illumination on the surface of the organic protective Ps coat is not resolved, it is possible to detect only the foreign object scattered light 606 with this technique. As shown in FIG.
When the P polarized light of 3C is disturbed, specularly reflected light 206 and diffracted light 2
07, which also makes it impossible to distinguish between foreign matter and irregularities.

However, as shown in FIGS. 1 and 4, if a five-metal integrating sphere detection system is used in which a cylindrical base plate 441 is inserted to separate specularly reflected light, the light shielding plate 441 causes specularly reflected light 206 and false detection. Since the diffracted light 207 is blocked, these elements do not enter the integrating sphere at all, and the foreign object scattered light 5 can be emphasized and detected. The principle is shown below.

When light enters a small inclined surface 221 as shown in FIG. 12, specular reflection light is generated due to the angle α of the surface. (9) Diffracted light 207 is generated by interference with reflected light from the adjacent small inclined surface 222. here,
The angle θ1 of the specularly reflected light is geometrically determined as θ=2α. On the other hand, the angle d of the m-th order diffracted light is determined by the following equation from the distance between the rigid surfaces 221 and 222, that is, the distance L between the patterns in the impulsatory membrane, and the wavelength λ of the illumination light. For details, see Physical Optics (Kyoritsu Shuppan) PP, 1
Please refer to o1-113.

Here, the problems are the intensity Ip, r of the foreign object scattered light, the intensity 1ref of the specularly reflected light, and the intensity Id of the m-th order diffracted light.
This is the relationship between the magnitudes of ef and m. If the component absorbed by the total intensity of the incident light is IT, the following relationship holds true between them. Regarding Iref, as mentioned above, it is twice the oblique angle α of the unevenness, so it is easy to set up a light shielding plate to block this, so by inserting a light shielding plate, Iref mixed into the integrating sphere can be reduced. .

can be called 蓓. On the other hand, regarding Idef,m, according to equation (2), the angle of occurrence takes a dispersion value, and most of the energy of the diffracted light is concentrated in the ±1st to ±2nd order diffracted light (see physical optics). ) If the K-th layer is used, it can be ensured by blocking some fourth-order or lower diffracted light and setting Iref, = 0. If 15' on the right side of the above equation is at this level of ratio, then after detection, the entire binarization process cannot be performed electrically, α4. This is a guideline that it is possible to judge only the

Therefore, as shown in FIG. 13, if the shielding angle θ2 of the original plate 441 is set so that the fourth-order diffracted light 267 generation angle α'4 and the specularly reflected light angle 2α can be shielded, the unevenness of the surface of the organic protective film and the foreign matter can be blocked. It becomes possible to discriminate and detect.

In the world, the currently used X-Iwao mask has uneven #
The maximum value of discomfort for 4M+ is α = 7°, so 2α = 14°, and when L>4 μm (it has been experimentally revealed that no unevenness occurs on the surface of the organic retentive membrane when L < 4 μm), When the wavelength of the illumination light is λ = 0.525 μm, m that satisfies equation (3) is m = 6. Maku,
At that time, α' is α'=26°, so the light shielding plate 44
If the shading angle θ of 1 is set to θ>26° and detected,
Target detection specification α15μ. It is possible to detect foreign substances with .

An embodiment of the present invention is shown in FIGS. 1 and 4. FIG.

The X-ray mask 1 coated with the organic preservation film 104 described above for the integrating sphere only detection method is supported by the holder portion 11 and scanned in the direction of the arrow 13 by a uniaxial stage 12 capable of double-sided inspection. On the other hand, the illumination source 203b uses a source 18 with a wavelength of 380 nm or less from a laser beam W614, and after the beam diameter is expanded by a beam expander 15b, the beam is focused on a point 20 via a condensing lens 16b. In between, galvano mirror 17b k is installed, point 20t'' arrow 1
Have them stroke in a direction perpendicular to 3. From this K, point 20 is mask 1
Since the entire circuit pattern area is scanned, the scattered light may be detected by the integrating sphere 301b and the detector 302b in synchronization with the scanning.

Here, the diffracted light up to the mth order from the surface unevenness is not mixed into the integrating sphere 601b by the cylindrical light shielding plate 441 having a shielding angle θ.

As described above, it is possible to realize a device that can detect minute foreign objects on a mask without being affected by surface irregularities.

Note that the cylindrical light shielding plate 441 has an outer surface with good reflectance.
It is desirable to have it in a flat state.

〔Effect of the invention〕

As explained above, according to the present invention, the influence of the circuit pattern and the unevenness of the surface organic protective film can be reduced to 0.
It becomes possible to detect minute foreign matter of 15 μm or less. Therefore,
When the sample is a mask, it is possible to significantly reduce the occurrence of pattern defects due to transfer of foreign matter on the mask at the edge, which has a great effect on the yield of LSI Lu products.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing two conventional configurations of two embodiments of the present invention, FIG. 2 is a diagram showing a case in which the organic protective film side of an X-ray mask is irradiated with laser light, and FIG. A line diagram showing the spectral transmittance of an organic protective film in the case of a line mask, Figure 4 is a perspective view showing two embodiments of the device based on the principle shown in the first factor, and Figure 5 is a diagram showing the spectral transmittance of an organic protective film in the case of a line mask. 9 shows another example of a line mask, FIG. 6 is a diagram for explaining the problems of the embodiment, FIG. 7 is a sectional view showing the basic structure M of another embodiment of the present invention, and FIG. 8 is a diagram showing the reflection characteristics when illuminated with P-polarized Brewster angle,
Figure 9 is a diagram showing the relationship between the angle of incidence and ) LP/fuP;
Figure 10 shows 111g based on the principle shown in Figure 7.
Figure 11 is a diagram for explaining the problems of the example, and Figure 12 shows the reflection characteristics when a laser beam is irradiated perpendicularly to the organic protective film. FIG. 13 is a conceptual diagram showing the best embodiment of the present invention. 101...Supporting material, 102...Base material, 103...
Circuit pattern, 104-...Organic preservation lf! m, 502a
, 302b, 302cm@outer, 205(L, 2
i, 13b, -, illumination light, 205 (1,205b -
...Foreign object scattered light, 301 (Z, 301b, 301c
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Claims (1)

[Scope of Claims] 1. A method for detecting foreign matter, which comprises irradiating light onto a sample having a protective film on a circuit pattern, and detecting foreign matter on the protective film using diffracted light from the protective film. 2. The foreign matter detection method according to claim 1, wherein the sample is an exposure light mask. 3. The foreign matter detection method according to claim 2, wherein the exposure mask is an X-ray exposure mask. 4. Light is irradiated onto the sample that has a protective film on the circuit pattern, the low-order diffracted light and the high-order diffracted light generated from the surface of the protective film are separated by a light shielding member, and one of the diffracted lights is focused by an integrating sphere. . A method for detecting foreign matter, comprising detecting a foreign matter on a protective film of the sample by detecting focused diffracted light using a photoelectric conversion means. 5. The foreign object detection method according to claim 1 or 4, wherein the light has a wavelength of 380 nm or less. 6. An irradiation means for irradiating light onto a sample having a protective film on a circuit pattern, a light shielding member for separating low-order diffracted light and high-order diffracted light generated from the surface of the protective film of the sample, and the light shielding plate. A condensing optical system that condenses one of the separated diffracted lights, and a photoelectric conversion element that converts the light condensed by the condensing optical system into a video signal, and a video signal obtained from the photoelectric conversion element. A foreign object detection device characterized in that it is configured to detect a foreign object. 7. The irradiation means is configured to irradiate the sample with light from a direction perpendicular to the sample, and the light shielding member is formed in a cylindrical shape with an axis perpendicular to the sample and a mirror-like outer surface. The foreign object detection device according to claim 6, characterized in that: 8. The foreign object detection device according to claim 7, wherein the condensing optical system is formed of an integrating sphere.