JPH0435025B2 - - Google Patents

Description

[Detailed description of the invention]

[Field of Application of the Invention] The present invention is particularly applicable to semiconductor LSI wafers or masks.
The present invention relates to a detection method and apparatus suitable for foreign particle inspection that detects microscopic foreign particles on patterned wafers, etc., at high speed and with high sensitivity during LSI manufacturing intermediate steps. [Background of the Invention] Conventional foreign particle detection devices on wafers detect linear particles by () a combination of one-dimensional high-speed scanning of a laser beam and low-speed translational movement of a sample, and () a combination of high-speed rotation and low-speed translational movement of a sample. Scanning was used to scan and detect the entire surface of the sample. Also, JP-A-57-
80546 (known example 1) combines electrical scanning of a self-scanning one-dimensional photoelectric conversion element array and low-speed sample movement to achieve scanning equivalent to the above (). Furthermore, ADGara: Automatic Microcircuit and
Wafer Inspection, Electronics Test, Vol.4,
No. 5, May 1981, pp. 60-70 (known example 2), a self-scanning one-dimensional photoelectric conversion element array is placed at the radial position of the sample wafer, and this is combined with rotational movement of the sample to achieve the above (). Achieves equivalent scanning. However, in the methods of Known Examples 1 and 2, it is impossible to avoid "missing" a foreign object when the dead zone existing in the adjacent portion of each photoelectric conversion element picture element scans the foreign object. In order to strictly avoid this, it is necessary to install a plurality of photoelectric element arrays in an overlapping manner so as to cover the dead zone. This causes an unnecessarily large amount of signal processing circuitry and a decrease in reliability. However, even if the photoelectric element arrays are not overlapped, the size of the foreign object to be detected is sufficiently large compared to the above dead zone width, or the total dead zone width is small enough to be ignored compared to the total photoelectric conversion element pixel width. In that case, the above-mentioned "missing" will not be a big problem. From this point of view, the methods of Known Examples 1 and 2 ignore "missing" due to the dead zone. [Detection of foreign objects on patterned wafers] Inspection of foreign objects on patterned wafers during the intermediate process of LSI manufacturing is essential for improving product yield and reliability. The automation of this work was published in Japanese Patent Publication No. 55
-149829, JP-A-54-101390, JP-A-55-94145,
This is realized by a detection method using polarized light, as shown in a series of patents such as Japanese Patent Application Laid-Open No. 56-30630. This principle will be explained using FIGS. 43 to 50. As shown in FIG. 43, if only the illumination light 4 is irradiated onto the surface of the wafer 1 at an inclination angle φ, reflected light and scattered lights 5 and 6 will be generated from the pattern 2 and the foreign matter 3 at the same time. It is not possible to distinguish and detect only 3. Therefore, a device was devised to detect the foreign matter 3 by using polarized laser light as the illumination light 4. As shown in FIG. 44a, a pattern 2 existing on a wafer 1 is irradiated with S-polarized laser light 4. (Here, when the electric vector 10 of the laser beam 4 is parallel to the wafer surface, it is called S-polarized laser illumination.) In general, the surface irregularities of the pattern 2 are microscopically small enough compared to the wavelength of the illumination light, and the optical Since the reflected light 5 is smooth, the S-polarized light component 11 is maintained in the reflected light 5 as well. Therefore, the reflected light 5
If installed in the optical path, the reflected light 5 is blocked and does not reach the photoelectric conversion element 7. On the other hand, as shown in FIG. 44b, the scattered light 6 from the foreign object 3 includes a P-polarized light component 12 in addition to the S-polarized light component 11. This is because the surface of the foreign object 3 is rough and the polarization is canceled.
This is because the P-polarized light component 12 is generated. Therefore,
If the P-polarized light component 14 passing through the analyzer 13 is detected by the photoelectric conversion element 7, the foreign object 3 can be detected. Here, as shown in FIG. 43, when the angle between the longitudinal direction of the pattern 2 and the laser beam 4 is at right angles, the reflected light 5 is completely blocked by the analyzer 13, but as shown in FIG. If this angle is different from the right angle, light will not be completely blocked. This discussion is published in Proceedings of the Society of Instrument and Control Engineers, Vol.17, No.2, p232.
It is stated on p242, 1981. According to this, only the reflected light from the pattern whose angle is within ±30° from the right angle enters the objective lens installed above the wafer, so the pattern reflected light within this range 5
Although the light is not completely blocked by the analyzer 13, its intensity is small enough to be distinguished from the 2-3 μm foreign object scattered light, so it does not pose a practical problem. Here, the inclination angle φ of the polarized laser 4 is set to about 1° to 3°. This is for the reason shown below.
In the experiment shown in FIG.
The intensity Vs of the pattern reflected light 5 and the intensity Vp of the component passing through the analyzer of the pattern reflected light 5 are calculated using the objective lens 9 (magnification 40×, NA=0.55).
Measured using The experimental results are shown in FIG.
This plotted the laser inclination angle φ on the horizontal axis and plotted the foreign matter/pattern discrimination ratio Vs/Vp. As shown in the figure, when the inclination angle φ is 5° or less, Vs can be easily distinguished from Vp, so stable foreign object detection is possible.
Moreover, considering design matters, φ=1° to 3° is optimal. (Refer to Japanese Patent Application Laid-Open No. 56-30630.) The reason why two laser light sources 15 are used from the left and right is to enable stable detection of foreign objects that generate anisotropic scattered light. Next, a foreign substance inspection method using this detection principle will be explained with reference to FIGS. 47 to 50. As shown in FIG. 47a, a slit 8 is provided on the sample imaging surface to limit the detection range. As a result, only the scattered light within the projected area 8a of the opening of the slit 8 onto the sample is detected at a time, so that the integrated intensity of the pattern reflected light P component within this area is 1
If the foreign matter scattered light P component 14d is sufficiently large compared to 4p, the foreign matter 3 can be stably detected. Therefore, this area 8a is the size of the foreign object to be detected (2 to 3 μm)
If the size is about the same as , the detection sensitivity will be optimal, but the number of scans will be increased as shown in FIG. 50b, and the inspection time will be long. On the other hand, the opening area is 8
If a is increased, inspection can be performed in a short time, but the detection sensitivity will deteriorate. Considering this,
Currently, the area 8a is 10 x 200μm2, and ^it is 2 to 3μm.
It takes about 2 minutes to detect foreign particles (for 150cm wafers). This situation will be explained using FIG. 48 and FIG. 49. First, FIG. 48 shows a plan view a and a cross-sectional view b of the wafer surface. The pattern 2 includes () slight depressions in the pattern and () portions having angles other than perpendicular to the irradiation direction of the laser beam 4, and a small amount of scattered light P component 14p is generated from each of these portions. On the other hand, a small foreign particle 3a with a size of about 0.5 to 2 μm
And from the large foreign matter 3b of 2 μm or more, the above (),
A P component 14d having a larger intensity than each of the locations in parentheses is generated. FIG. 49 shows the signal output of the photoelectric conversion element 7 when the aperture 8a scans over the sample. Figure a shows the distribution of P components 14p (circuit pattern) and 14d (foreign matter) on the sample. Opening 8 on this distribution
When a is scanned, a video signal output V _P shown in b of the same figure is obtained, and when this is binarized, a defect signal shown in c of the same figure is obtained. In this example, since the output from the small foreign object 3a and the edge of pattern 2 are the same, the threshold shown by the broken line must be set at a higher position than this output, and as a result, the detection is limited to only large foreign objects. Ru. However, in the manufacturing of highly integrated LSIs such as 256Kbit memory LSIs, the presence of foreign matter as small as 1μm greatly affects product yield, so 1μm
m Foreign object detection sensitivity is required. This means that if the aperture 8a is limited to 5×5 μm ² or ^less in the device shown in FIG. As a result, it becomes possible to detect 1 μm foreign matter. However, in this case, the inspection time increases by about 40 times, making it impossible to synchronize with the manufacturing throughput, which poses a problem in practical application. [Object of the Invention] An object of the present invention is to provide a method and apparatus for detecting foreign matter that can distinguish minute foreign matter from circuit patterns and inspect them at high speed. [Summary of the Invention] That is, the present invention provides a method for detecting minute foreign matter on a sample having a circuit pattern, which includes: irradiating at least one laser beam toward the sample surface and detecting scattered light from the sample surface. By using the polarization of the laser beam, a first signal in which the foreign matter is emphasized and a second signal in which the circuit pattern is emphasized are obtained. A foreign matter detection method is characterized in that a minute foreign matter is detected by comparison in such a way that the irradiate with at least one laser beam, detect the scattered light from the surface of the sample, and generate a first signal in which foreign matter is emphasized using the polarization of the laser beam, and a second signal in which the circuit pattern is emphasized. the first signal and the second signal obtained by the optical means, and a comparing means for detecting minute foreign matter by comparing the first signal and the second signal obtained by the optical means so that the foreign matter is further emphasized. This is a foreign object detection device characterized by the following. Further, the present invention performs two types of illumination, including polarized laser illumination that has a large scattering effect on foreign objects and illumination that has a small scattering effect. Focusing on the fact that scattered light from the former illumination is likely to be generated by foreign objects, and scattered light from the latter illumination is likely to be generated by patterns, by detecting the ratio of the two scattered light signals,
The aim is to enable even more stable and highly sensitive detection of minute foreign matter. Furthermore, in the present invention, a plurality of photoelectric conversion solid-state image sensors each having a light-receiving area size of about 5 x 5 μm ² (converted to the sample surface) or less are used, and the output signals from each element are simultaneously transmitted. By performing parallel comparison processing, foreign matter inspection can be performed with high sensitivity without deteriorating high speed performance. [Embodiments of the Invention] Examples of the present invention will be described in detail using FIGS. 1 to 13. FIG. 1 shows how a solid-state image sensor array 20 is used in place of the slit 8 in the conventional example shown in FIG. FIG. 2 explains an example of the solid-state image sensor array 20. The light receiving part 20a is a silicon photodiode or
GaAsP photodiodes, and among these, PIN junction type photodiodes have characteristics such as high-speed response and high sensitivity, and are most suitable for the use of the present invention. The width of each light receiving portion 20a (pixel) is 500 μm, and there is a dead zone of 50 μm width between adjacent pixels. When the number of pixels is 40, for example, the total magnification of the detection system is 100x (when the magnification of the objective lens 9 is 40x and the magnification of the relay lens (not shown) is 2.5x).
Then, the size of one pixel is 5×5μ on the sample surface.
m ² , which means that an area of 5×220 μm ² is being scanned while being detected, and the inspection speed is about the same as that of the conventional method. The effects of this solid-state image sensor array 20 will be explained with reference to FIG. For comparison, the conventional example shown in FIG. 50 is shown at d, e, and f on the right side of the figure. For simplicity, the number of pixels in a, b, and c on the left side of the figure is 5 (i, j, k, l, m). In the figure, a shows the scanning state with the solid-state image sensor array 20, b shows the video signals (Si ₁ , Sj ₁ , Sk ₁ , Sl ₁ , Sm ₁ ) obtained thereby, and c
is the _signal (Si ₂ , Sj ₂ , Sk ₂ ,
Sl ₂ , Sm ₂ ). The output signal Sk ₁ of pixel k is the threshold
If you binarize with V _TH , the binarized signal Sk ₂ will be small foreign matter 3.
Also, a is "1", and sensitivity is improved compared to the conventional method. FIG. 4 shows a signal processing method for each pixel of the solid-state image sensor array 20. The outputs of each of the pixels i to n are simultaneously binarized in parallel in a binarization circuit 21, and the binarized signals (“1”) are led to an OR circuit 22 to detect foreign objects in at least one picture. When detected, the output of the OR circuit becomes “1” and is input to the foreign object memory 23. With this method, the outputs of 40 pixels are processed simultaneously in parallel, and inspection speed and detection sensitivity can be significantly improved compared to when a self-scanning image sensor is used. However, the dead zone 20b of the solid-state image sensor array 20 causes a drawback as described below. This solution is shown in FIGS. 5-9. As shown in FIGS. 5 and 7, when the arrangement direction of the solid-state image sensor array 20 and the scanning direction are perpendicular, a dead zone 20b and a small foreign object 3c between pixels i and j
If the relationship is as shown in the figure, the small foreign object 3c will be overlooked. (In the case of FIG. 5, scanning is performed from a to b.) Therefore, as shown in FIGS. 6 and 8, the arrangement direction of the solid-state image sensor array 20 and the scanning direction are set at an appropriate angle (for example, 45 degrees) By having this, the above-mentioned oversight can be avoided. (In the case of FIG. 6, scanning is performed from a to b and from b to c.) This angle does not necessarily need to be 45° if the shape of the picture 20a is rectangular. In FIG. 8, the small foreign object 3c is detected redundantly by pixels j and k, resulting in double counting. However, as a way to avoid this double counting, there are ways to avoid this double counting.
You can use the method described in 118647. FIG. 9 shows an example of application of the invention in the case of spiral scanning. FIG. 10 shows the overall configuration of the embodiment. Wafer 1
is attracted to the wafer chuck 40 by the vacuum tube 41, while the X stage 46 and Y stage 49
to move in the XY direction. Foreign object information detected by the solid-state image sensor array 20 is transmitted to a binarization circuit 21,
The signal passes through the OR circuit 22 to a control circuit 32 including a foreign object memory 23, and is displayed on a display device 33. In the present invention, the pixel size is set to be approximately 5×5 μm ² or less, so if defocusing due to wafer surface undulation occurs during inspection, the foreign object detection sensitivity will be significantly reduced. Therefore, it is essential to use a configuration in which the automatic focus detection section 30 detects the amount of defocus during inspection and provides feedback to the driver 31 of the focus mechanism motor 43. The principle of this autofocus function was announced on pages 223 to 224 of the preprint collection of the 22nd SICE Academic Conference, and
70540, this principle will be explained using FIGS. 11 to 13. This method is ideal for the present invention because it is characterized by stable automatic focusing without being affected by the pattern on the sample. FIG. 11 shows the main parts of the automatic focus detection section 30. Striped pattern 60a on the striped pattern glass plate,
60b are each projected onto the sample by the objective lens 9, but each focal point position is determined by the imaging element array 20.
The focus point is set slightly too high and low relative to the focal point. Each stripe pattern 60a, 6
The image 0b on the sample is magnified by the objective lens 9, reflected by the semi-transmissive mirrors 34 and 62, and formed on the image sensor 61. FIG. 12a shows the projected fringe pattern imaged on the image sensor 61 when the wafer is too low (Z<0), and FIG. 12d shows the projected fringe pattern detected by the image sensor 61 in the case shown in FIG. 12a. This shows the video signal waveform. Fig. 12b shows the case of the focal point position (Z=0),
A projection pattern formed on the image sensor 61 is shown, and FIG. 12c shows a video signal waveform detected by the image sensor 61 in the case shown in FIG. 12b.
Figure 12e shows when the wafer is too high (Z>0),
The projection fringe pattern imaged on the image sensor 61 is shown, and FIG. 12f shows the video signal waveform detected by the image sensor 61 in the case shown in FIG. 12c. Therefore, when the image sensor array 20 is in focus, the detection signal of the image sensor 61 corresponds to the striped pattern 60a.
and 60b, so the difference signal between the two becomes zero. On the other hand, in the case of too much rise (or too much fall), the deviation from the in-focus point of the image sensor 61 corresponds to the magnitude of the output of the difference signal, so that the servo signal shown in FIG. 13 is obtained. The figure shows an example of actual measurement of the difference signal when the sample surface is an aluminum surface and when the sample surface has a complicated pattern (memory cell surface). This results in ±0.5μ
Since focusing within m is possible, stable foreign object detection is possible when the objective lens 9 has a magnification of 40x. As an automatic focusing mechanism, a motor 43, a slope 45, a ball 44, as shown in FIG.
The configuration using the plate spring 42 is simple. Next, the explanation corresponding to the claims of the present invention will be explained in the fourteenth section.
This will be explained using FIGS. First, the basic principle will be described using FIGS. 14 and 15. In the method shown in FIG.
14 is obtained by removing 3 and installing a polarizing beam splitter 150. Here, slit 8
H and 8L detect the same point on the sample. Since the polarizing beam splitter 150 has a characteristic of reflecting the P-polarized light component and passing the S-polarized light component,
The output Vp of the photoelectric conversion element 7L is shown in Fig. 47 (Fig. 49).
(Figure). This is shown in Figures 15a and b. On the other hand, the output Vs from the photoelectric conversion element 7H after being scanned as shown in FIG. 15c becomes as shown in FIG. 15d. Comparing a, b and c, d, a, b
Then, the foreign object has a higher output than the pattern,
For patterns c and d, the output is higher in the pattern. Therefore, the output ratio Vp/Vs of both is calculated by the analog comparison circuit 1.
00 (shown in Fig. 15 e) and binarized with a threshold value m in the binarization circuit 101 (shown in Fig. 15 f). ) It can be seen that it is possible to detect small foreign objects 3a. Moreover, the solid-state image sensor array 20 described above
If the photoelectric conversion elements 7H and 20L are used in place of the photoelectric conversion elements 7H and 7L, the detection sensitivity can be improved. In this case,
It is necessary to use a plurality of analog comparison circuits 100 and binarization circuits 101 to simultaneously perform analog comparison in parallel (see FIG. 16). The above illumination/detection method is called ()-type illumination. Next, the ()-type illumination will be explained using FIGS. 17 and 18. For example, as shown in FIG _. 17, by using the output characteristics of the foreign matter and the pattern due to the inclination angle φ shown in FIG. In this method, the same sample point is illuminated with (wavelength λ ₂ ) 15H, and only the P component is detected and compared using arrays 20H and 20L using a color separation branching prism and analyzers 151H and 151L. The outputs of the arrays 20H and 20L and the binarization method are shown in FIG. FIG. 18a shows a case where a laser beam is irradiated diagonally from below onto, for example, Si where foreign substances 3a and 3b are present. Figure b shows the output signal V _L in that case,
Figure c shows the binary signal. FIG. 18d shows a case in which, for example, a laser beam is irradiated onto Si from an obliquely upper side. Figure e shows the output signal _VH in that case.
FIG. 18f shows the signal waveform of V _L /V _H , and FIG. 18g shows its binary signal. The above illumination and analysis conditions are modeled and shown in FIG. 30a. ( ) type illumination is not limited to the use of the above-mentioned S-polarized illumination lights 15L and 15H, but also various illumination light and analysis conditions shown in FIGS. 30b to 30b and 31a to d. You can also do it. Among these, lighting/analysis condition L that emphasizes foreign matter is (a)
Either condition is used: analysis of P-polarized light component using S-polarized illumination, or (b) analysis of P-polarized light component using P-polarized light illumination. The reason for this will be explained in detail later. On the other hand, the illumination/analysis condition H that emphasizes the pattern may be any case other than the above (a) and (b), so it is not necessarily necessary to use polarized light. (In other words, incoherent light such as a normal halogen lamp may be used, and this is shown by the symbols S+P in FIGS. 30a-h and 31a-d.) 1977-
Providing a dichroic prism (or mirror) as described in 149829 and JP-A-56-43539,
A light branching prism (semi-transmissive mirror) and a color filter or an interference filter may be used in combination. In addition, the illumination lights 15H and 15L are generated by a He-Ne laser (λ=6.328Å) or a GaAlAs laser diode (λ
= 7.800 to 8.300 Å), InGaAsP laser diode (λ = 13.000 Å), and Ar laser (e.g. 4580 Å), the lens system 15
Since the bL focuses the illuminance at the sample surface, high illuminance can be obtained, making detection even more stable. As mentioned above, in type () illumination, the foreign object emphasizing illumination (L) satisfies the conditions (a) or (b), and the pattern emphasizing illumination (H) and the foreign object emphasizing illumination (L) have different wavelengths (λ ₁ , λ ₂ ) is an essential condition. Here, instead of color separation, JP-A-57-66345
As shown in FIG. 2, if a method is used in which time-division detection is performed and the detection outputs at (L) and (H) are compared, the components for illumination and light analysis can be simplified. In this case, one type of illumination and one array 20 are sufficient, but the analyzer must include an optical element such as a Pockel cell that has a high-speed analysis characteristic switching function. Next, an embodiment of the present invention will be described using FIGS. 19 to 28. FIG. 19 shows details of the signal processing circuit shown in FIG. 16. This is a method similar to that shown in FIG. 20 to 22 are similar to FIGS. 10 and 20, but the differences are illumination light 15H, lens system 15bH, light branching prism 150, color filters 151H, 151L, array 20H, and analog comparison circuit. This is the point where 100 is added. The analog comparison method will be explained in further detail using FIGS. 23 to 28. 23 and 24 show the results of an experiment using the conditions shown in FIG. 17. In the experiment, regarding the output 14p of pattern 2, pattern 2 was
The pattern outputs V L , V _H are rotated by an angle η from a right angle to the projection direction of H, 4L onto the wafer surface _.
was measured. On the other hand, as for foreign matter, V _L and V _H were measured using standard particles of 0.7, 1, and 2 μm (in this case, rotation was not necessary). The measured values are shown in FIG. From this, it can be seen that at any angle of the pattern, the output ratio (white circle) V _L /V _H from the pattern is smaller than m (the reciprocal of the slope of the broken line in the figure). On the other hand, the output ratio V _L /V _H of foreign matter indicated by a black circle is larger than m. A method of discriminating between the foreign matter and the pattern using an electric circuit in consideration of the output characteristics of the foreign matter and the pattern shown in FIG. 24 will be explained with reference to FIGS. 25 to 28. FIGS. 25 and 26 show an example using an analog division circuit. The output ratio V _L /V _H is calculated by the analog divider circuit 100, and when V _L /V _H >m, the binarization circuit 101 outputs "1 ^* ". It should be noted here that in the output ratio calculation, if V _H is small, the calculation error will be large and the calculation result will be unstable (for example, if V _H is zero, V _L /V _H =
∞). As a way to avoid this, the binarization circuit 104 only applies the signal when V _L > V _TH (V _TH is the value of V _L corresponding to a foreign object of about 0.5 μm) (“1 ^** ”).
The calculation result of V _L /V _H may be set as valid "1".
This is realized by the binarization circuit 104 and the AND circuit 103. 27 and 28 show the analog subtraction circuit 105
An example using . In this case, the intensity of the H or L illumination light and the gain of the output amplifier (not shown) of the array 20H or 20L are adjusted, and m=1
It is important that the angle is 45 degrees. The result V _L −V _H of the analog subtraction circuit 105 is the result of the binarization circuit 10
Similarly, it is valid only when the output of No. 4 is "1 ^** " (V _L > V _TH ). Instead of the analog division/subtraction described above, the output may be A/D converted and the calculation may be performed using digital values. FIG. 29 shows ( ) type illumination. In this case, the illumination lights 15H and 15L have wavelengths λ ₁ and λ ₂ , respectively,
For example, a light branching prism 15 is used as a color separation optical system.
0, color filters 151H and 151L are used. Here, the semi-transparent mirror 15C of the illumination system is 15
It is used to combine H and 15L illumination lights. As mentioned above, in the (), (), () types of illumination/analysis conditions, the condition (L) that emphasizes foreign objects is as described above.
It is essential to use conditions (a) and (b). on the other hand,
Conditions for emphasizing patterns (H) Figure 30 a~h~
Various methods can be considered as shown in FIGS. 31a to 31d. Table 1 shown below shows whether or not a to h' in FIG. 30 and a to d in FIG. 31 are applicable under ()()() type conditions.

【table】

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to detect minute foreign objects present on a target object with high sensitivity and stability while maintaining high speed of foreign object detection.

[Brief explanation of drawings]

Fig. 1 is a configuration diagram showing an embodiment of the foreign object detection device of the present invention, Fig. 2 is a perspective view showing details of the solid-state image sensor shown in Fig. 1, and Fig. 3 is a comparison between the present invention and a conventional example. FIG. 4 is a diagram showing the signal processing circuit of the solid-state image sensor shown in FIG. 1, FIG. 5 is a diagram showing the positional relationship between the dead zone and a foreign object, and FIG. 7 is a diagram showing the relative scanning direction of the solid-state imaging device with respect to the wafer in FIG. 5, and FIG. 8 is a diagram showing the relative scanning direction of the solid-state imaging device with respect to the wafer in FIG. 6. 9 is a diagram showing the relative spiral scanning of the solid-state image sensor with respect to the wafer. FIG. 10 is a block diagram showing the embodiment shown in FIG. 1 in more detail. The figure is a perspective view showing the automatic focus detection section shown in FIG. 10, FIG. 12 is a diagram for explaining automatic focus detection,
Figure 3 is a diagram showing the relationship between the difference output obtained from the automatic focus detection section shown in Figure 11 and the focus shift, and Figure 14.
15 is a perspective view showing the basic principle of the present invention, FIG. 15 is a diagram showing a state in which the wafer is scanned in FIG. 14 and an output signal obtained by the apparatus shown in FIG. 14, and FIG. A perspective view showing the case of ( )-type illumination using a solid-state image sensor array as a photoelectric conversion element, Fig. 17 is a perspective view showing the case of ( )-type illumination, and Fig. 18 shows the output obtained by the device shown in Fig. 17. Figure 19 is a diagram showing the analog comparison circuit in detail, Figure 20 is a diagram showing the signals etc.
7 is a perspective view showing the embodiment shown in more detail, FIG. 21 is a front view of FIG. 20, FIG. 22 is a diagram showing the signal processing circuit not shown in FIG. Figure 23 is a diagram showing the state of the circuit pattern and reflected light from a foreign object, Figure 24 is a diagram showing experimental relationship data between the outputs V _H and V _L obtained based on this, and Figure 25 is a diagram showing the relationship between V _H /V _L Figure showing the results of
Figure 26 shows an analog divider circuit for realizing V _H /V _L shown in Figure 25, and Figure 27 shows V _L
Figure 28 is a diagram showing the analog subtraction circuit for realizing V _L -V _H shown in Figure 27. Figure 41 is a perspective view of the experimental equipment.
Figure 2 is a graph of experimental data showing the S/N ratio.
FIG. 3 is a cross-sectional view of a wafer, FIG. 44 is a diagram showing a circuit pattern on the wafer and the state of reflection from a foreign object in response to irradiated laser light, and FIG. 45 is a schematic diagram showing a first example of a conventional foreign object detection method. A perspective view, FIG. 46 is a graph showing measurement data of the output ratio V _s /V _p when the inclination angle φ is changed in FIG. 45, and FIG. 47 is a schematic diagram showing a second example of the conventional foreign object detection method. A perspective view, FIG. 48 is a diagram showing the circuit pattern on the wafer and the state of reflection from a foreign object, and FIG. 49 is a diagram showing the relationship between video signals obtained by scanning the wafer relatively with the static as shown in FIG. 47. FIG. 50 is a schematic perspective view showing a conventional foreign object detection method similar to the second example shown in FIG. 47. Figure 29 is a perspective view showing () type illumination, Figures 30 and 31 are diagrams showing various combinations of illumination and analysis, and Figure 32 is a perspective view showing incident light and reflected light of the pattern. Figure, No. 33
The figure is a perspective view showing the polarization of incident light and reflected light.
The figure is a graph showing an example of calculating the coefficients s(φ) and p(φ),
Figure 35 is a perspective view showing the profile of the pattern, and Figure 36 is the direction and line segments of the pattern reflected light.
A perspective view showing the trajectory of RQ, Fig. 37 is a perspective view showing the relationship between the reflected light and the objective lens, and Fig. 38 is a perspective view showing the trajectory of RQ.
In the case of polarized illumination (incident light A [0, -1, 0], E
FIGS. 39 and 40 are plan views showing the polarization component intensity distribution (n=1.45 and n=4.2). Explanation of symbols, 1...Wafer, 2...Pattern,
3... Foreign matter, 4... Illumination light, 5... Reflected light, 6...
...Scattered light, 7...Photoelectric conversion element, 9...Objective lens, 10...S polarized light, 11...S polarized light component, 1
2, 14... P polarized light component, 13... Analyzer, 15
... Polarized laser light source, 20 ... Solid-state image sensor array for photoelectric conversion, 20a ... Light receiving section, 20b ... Dead zone, 21 ... Binarization circuit, 22 ... OR circuit,
23... Foreign object memory, 30... Automatic focus detection section,
150...Polarizing beam splitter (or color separation prism or dichroic mirror or light branching prism), 100...analog comparison circuit, 101,
104, 105...Binarization circuit, 103...
AND circuit, 151H, 151L...color filter (or interference filter, or analyzer).

Claims (1)

[Claims] 1. A method for detecting minute foreign matter on a sample having a circuit pattern, in which at least one laser beam is irradiated toward the sample surface, scattered light from the sample surface is detected, and the laser beam is detected. A first signal in which the foreign matter is emphasized using polarization of light and a second signal in which the circuit pattern is emphasized are obtained, and the first signal and the second signal are further combined to further emphasize the foreign matter. A method for detecting foreign objects characterized by detecting minute foreign objects by comparing 2 Using a linearly polarized laser beam as the laser beam, irradiate the sample surface at an inclined angle, polarize the scattered light from the sample surface, and obtain a first signal from the first photoelectric conversion element. 2. The foreign object detection method according to claim 1, wherein the second signal is obtained from the second photoelectric conversion element at the same time. 3 Using a plurality of laser beams as the laser beams, the sample surface is irradiated with different wavelengths at different inclination angles, and the scattered light from the sample surface is color-separated to produce a first signal from the first photoelectric conversion element. 2. The foreign object detection method according to claim 1, wherein the second signal is obtained from the second photoelectric conversion element. 4. In an apparatus for detecting minute foreign matter on a sample having a circuit pattern, at least one laser beam is irradiated toward the sample surface, scattered light from the sample surface is detected, and the polarization of the laser beam is used. an optical means for obtaining a first signal in which foreign matter is emphasized and a second signal in which a circuit pattern is emphasized; What is claimed is: 1. A foreign object detection device comprising: comparison means for detecting minute foreign objects by comparing such that the foreign objects are emphasized. 5. The optical means includes an irradiation optical system that irradiates the sample surface with a plurality of laser beams at different wavelengths at different inclination angles, and a first and second laser beam that color-separates the scattered light from the sample surface. 5. The foreign object detection device according to claim 4, comprising a color separation/branching optical element branching into a photoelectric conversion element. 6. The foreign object detection device according to claim 5, wherein the color separation/branching optical element is composed of a light branching prism or a semi-transparent mirror and a color filter. 7. The foreign object detection device according to claim 6, wherein the color separation/branching optical element is composed of a dichroic prism or a dichroic mirror. 8. The foreign object detection device according to claim 6 or 7, wherein the color separation/branching optical element further includes an analyzer. 9 The optical means includes a linearly polarized light irradiation optical system that converts the laser light into a linearly polarized laser light and irradiates the sample surface at an inclination angle, and a linearly polarized light irradiation optical system that converts the laser light into a linearly polarized laser light and irradiates the sample surface with a tilt angle, and polarization decomposition of the scattered light from the sample surface. 5. The foreign object detection device according to claim 4, further comprising a polarization splitting/branching optical element branching to a second photoelectric conversion element. 10. The foreign object detection device according to claim 9, wherein the polarization splitting/branching optical element is constituted by a polarization beam splitter. 11. The foreign object detection device according to claim 9, wherein the polarization splitting/branching optical element is composed of a light branching prism or a semi-transparent mirror and an analyzer. 12 The optical means includes an irradiation optical system that irradiates the sample surface with a plurality of laser beams at different wavelengths at the same inclination angle, and a first and second laser beam that color-separates the scattered light from the sample surface. 5. The foreign object detection device according to claim 4, comprising a color separation/branching optical element branching into a photoelectric conversion element. 13. The foreign object detection device according to claim 12, wherein the color separation/branching optical element is composed of a light branching prism or a semi-transparent mirror and a color filter. 14. The foreign object detection device according to claim 13, wherein the color separation/branching optical element is composed of a dichroic prism or a dichroic mirror. 15 Claim 13, wherein the color separation/branching optical element further includes an analyzer.
15. The foreign object detection device according to item 1 or 14. 16. The foreign object detection device according to claim 4, wherein the comparing means is constituted by a dividing means. 17. The foreign object detection device according to claim 16, wherein the comparing means is configured to ignore the output of the dividing means when the second signal is near zero. 18. The foreign object detection device according to claim 4, wherein the comparison means is comprised of a subtraction means. 19. The foreign object detection device according to claim 18, wherein the comparison means is configured to ignore the output of the subtraction means when the second signal is near zero.