JPH0610656B2 - Surface defect detector - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an apparatus for optically detecting defects such as minute irregularities existing on the surface of an object to be inspected such as a semiconductor wafer.

(Prior art and its problems) In semiconductor wafers, video discs, etc., defects such as irregularities and scratches on the surface greatly affect product quality. Quality control is required. Various devices have been proposed as such a surface defect detecting device, but a typical nondestructive inspection is an optical detecting device, which is a conventional example (Japanese Patent Laid-Open No. 57-131039).
Is shown in FIG.

In the figure, a linearly polarized laser beam L from a laser light source 51 is reflected by a mirror 52, a beam diameter is expanded by a beam expander 53, and then reaches a polarizing beam splitter 54. Then, the light passes through the polarization beam splitter 54, passes through the quarter-wave plate 55, and is focused on the surface of the inspection object 57 by the focusing lens 56.

Reflected light R obtained by reflecting the laser beam L on the surface of the inspection object 57 is specular reflection light that is reflected on the flat portion of the surface of the inspection object 57 and returns along the same optical path as the incident light flux of the laser beam L. It includes (0th-order diffracted light) R ₀ and scattered light R _d that is scattered by surface defects and reflected in a direction different from the incident optical path of the laser beam L. Then, the reflected light R including both of them reaches the polarization beam splitter 54 again through the route opposite to the above. Since the reflected light R at this stage has passed through the quarter-wave plate 55 twice, its polarization direction is 9 times that of the original polarization direction of the laser beam L.
It has been rotated by 0 °. Therefore, the reflected light R is reflected to the right in the figure.

Of these, the regular reflection light R ₀ is reflected by the mirror 58, passes through the lens 59 and the cylindrical lens 60, and
Is incident on the photoelectric conversion element 61. Further, the scattered light R _d is
The light enters the second photoelectric conversion element 63 through the lens 62. The first photoelectric conversion element 61 has an area α shown in FIG.
_It has a light-receiving surface divided into _{1 to} α ₄ and the sum of the photoelectric conversion outputs of the regions adjacent to each other in the diagonal direction; (α ₁ + α ₄ ) − (α ₂ + α ₃ ) ... ( 1) is obtained and becomes the focusing error signal of FIG.

On the other hand, when there is a defect on the surface of the inspection object 57, the specular reflection light R ₀ decreases and the scattered light R _d increases. Therefore, the sum of all the regions forming the light receiving surface of the first photoelectric conversion element 61; α ₁ + α ₂ + α ₃ + α ₄ (2) is obtained and processed by the first defect detection circuit 64. The defect detection is performed by reducing the specular reflection light R ₀ . The output of the second photoelectric conversion element 63 is processed by the second defect detection circuit 65 to detect a defect due to an increase in the scattered light R _d . These two types of defect signals are sometimes used independently, and the difference between them is used to obtain S
The / N ratio may be improved.

However, such a device can only detect a scattering defect, that is, a defect that scatters incident light in each direction. Therefore, when a deflectable defect, that is, a defect that causes reflection by deflecting incident light in a specific direction (for example, a bite-like defect) is present on the surface of the object to be inspected, this is detected by the above-mentioned device. Is impossible.
For this reason, in order to detect the scattering defect and the deflecting defect together, it is necessary to separately provide a detection device for each of them, which leads to an increase in cost and complicated alignment adjustment of the optical system. There is a problem of becoming.

Further, although the above device can detect the presence or absence of a surface defect, it cannot judge the type of the defect.

OBJECT OF THE INVENTION The present invention is intended to overcome the above-mentioned problems in the prior art, is capable of detecting both scattering defects and deflecting defects in a low cost and compact configuration, and is capable of detecting surface defects. An object of the present invention is to provide a surface defect detection device capable of accurately determining the type.

(Means for Achieving the Object) In order to achieve the above object, the surface defect detecting apparatus according to the present invention first irradiates the surface of the inspected object with a light beam substantially perpendicularly. Then, a light separating means is provided for separating the light reflected on the surface of the object to be inspected into first reflected light containing deflective reflected light and second reflected light containing diffuse reflected light.

Then, of the reflected lights thus separated, the first
The reflected light of is received by the light receiving surface of the light receiving position detecting means.
The light receiving position detecting means is a means for outputting a light receiving position detection signal corresponding to the light receiving position of the deflected reflected light on the light receiving surface, and the deflectable defect is detected based on this signal.

On the other hand, the second reflected light is received by the scattered reflected light detecting means for detecting the scattered reflected light, and the scattering defect is detected based on the detection output. Further, this scattered reflected light detection means has a light receiving area of a substantially circular diameter, the arc-shaped unit element is arranged concentrically in a partial area thereof, and the fan-shaped unit element in the remaining area. Radially arranged. Therefore, the arc-shaped unit element simultaneously detects the radial intensity distribution of the diffraction pattern and the radial unit element simultaneously detects the circumferential intensity distribution, thereby determining the type of surface defect.

(Example) A. Overall Optical Configuration and Operation of Embodiment FIG. 1 is a schematic diagram of a surface defect inspection apparatus which is an embodiment of the present invention. In the figure, the laser beam L from the laser light source 1 is linearly polarized by the polarization beam splitter 2 and enters the light transmittance distribution filter 4. The light transmittance distribution filter 4 is obtained, for example, by vacuum-depositing a metal on a glass substrate, and the vapor deposition thickness thereof changes stepwise such that the central portion is thick and the peripheral portion is thin. I am allowed. Therefore, as shown in FIG. 2A, the light transmittance of the light transmittance distribution filter 4 becomes a small value T ₀ near the center position (r ₀ ) A of the light transmittance distribution filter 4. Further, the position coordinate r in the radial direction has a large value T ₁ at a portion B separated from r ₀ by a predetermined distance (described later) or more. Then, the light transmittance distribution filter 4 is arranged so that the central portion A is the incident position of the laser beam L.

Therefore, most of the laser beam L in FIG. 1 is reflected by the central portion A of the light transmittance distribution filter 4 having a small transmittance (in other words, the portion having a large reflectance), and the quarter wavelength plate After passing through the lens 5, the surface of the object to be inspected 7 at the position of the focal length f of the lens 6 is irradiated through the lens 6. The laser beam L is reflected by the surface 7 of the object to be inspected to become the reflected light R, which is formed by the deflected reflected light R _t and the scattered reflected light R _d .

Of these, the deflectable reflected light R _t corresponds to the specularly reflected light R ₀ when there is no deflectable defect on the surface 7 to be inspected, and in such a case (that is, R _t
= R ₀ ) is shown. The case where the deflectable reflected light R _t is deflected from the direction of R ₀ due to the presence of the deflectable defect will be described later in detail.

The reflected light R thus obtained re-enters the light transmittance distribution filter 4 via the lens 6 and the quarter-wave plate 5. As described above, the light transmittance distribution filter 4 has a step-like transmittance distribution, and the deflectable reflected light R _t
Enters the low transmittance portion A of them. Therefore,
Of the deflectable reflected light R _t , this light transmittance distribution filter 4
The ratio of the light passing through to reach the light receiving surface of the photoelectric conversion means 8 is low.

As described above, the laser beam L emitted from the laser light source 1 enters the central portion A of the light transmittance distribution filter 4. Needless to say, the specularly reflected light R ₀ from the surface 7 to be inspected is again incident on the central portion A, on the premise that the laser beam L is incident on the surface 7 to be inspected substantially vertically. I am trying. That is, the optical system such as the laser light source 1, the polarization beam splitter 2, the light transmittance distribution filter 4, the 1/4 wavelength plate 5, and the lens 6 has the laser beam L
Are arranged in a geometrical positional relationship that guides to the surface 7 to be inspected substantially vertically. These are as illustrated in FIG.

Since the scattered reflected light R _d is incident on the portion B having a large transmittance in the light transmittance distribution filter 4, all or most of the light is transmitted through the light transmittance distribution filter 4 and photoelectric conversion means. 8 is incident on the light receiving surface. Therefore, the transmittances T ₀ and T ₁ are, for example, T ₀ = 2% and T ₁ = 10.
If it is 0%, only 2% of the deflectable reflected light R _{t and} all of the scattered reflective light R _d are incident on the photoelectric conversion means 8.

On the other hand, the deflective reflected light R incident on the portion A having a small transmittance
Of _t , the component that has not passed through the transmittance distribution filter 4 (98% of the deflectable reflected light R _{t in} the above example) is reflected by this filter 4 and reaches the polarization beam splitter 2.
Since this light passes through the quarter-wave plate 5 twice, its polarization direction is rotated by 90 ° with respect to the incident laser beam L. Therefore, this light passes through the polarization beam splitter 2. Then, the bright spot position detector 9 is reached.

Therefore, the reflected light R from the surface 7 to be inspected is, in the transmittance distribution filter 4, the first reflected light R ₁ including the deflective reflected light R _t and the second reflected light R ₁ including the scattered reflective light R _d. It is separated into light R ₂ .

Therefore, the transmittance distribution filter 4 functions as a light separating unit that separates the reflected light R into the first and second reflected lights R ₁ and R ₂ .

By the way, as described above, the second reflected light R ₂ in this embodiment includes the deflectable reflected light R ₂ in addition to the scattered reflected light R _d.
It also contains part of _t . The presence of the scattering defect not only increases the scattered reflection light R _d, but also decreases the intensity of the deflective reflection light R _t (regular reflection light R ₀ ), so that processing based on both of these data can be performed. For example, because the detection accuracy of scattering defects is improved. However, since the intensity of the deflected reflected light R _t is significantly higher than the intensity of the scattered reflected light R _d (for example, 100: 1), the deflectable reflected light R _{t is}
If a considerable part of the above is included in the second reflected light, the difference in light intensity is too large, and it becomes difficult to detect with high precision in the dynamic range of a single photoelectric conversion means. Therefore,
When the deflectable reflected light R _t is thus included in the second reflected light, it is desirable to include only a few% of the deflectable reflected light R _t .

On the other hand, in the first reflected light, since only the deflective reflected light R _t is originally necessary information, the deflective reflected light R _t should be included as much as possible, and the diffuse reflected light R _d should not be included. Is desirable. The transmittance distribution filter 4 is a light separating means that simultaneously satisfies these two requirements.
These two conditions can be satisfied by using the above values as the light transmittances T ₀ and T ₁ of the A and B portions.

Such a situation is shown in FIG. 3 as a distribution curve of the light intensity I in the radial direction of the light transmittance distribution filter 4. In this figure, the reflected light before passing through the light transmittance distribution filter 4 (the same figure (a)) and the second reflected light obtained by passing through this filter 4 (the same figure (b)) are compared. Then, in the former case, the specular reflection light R ₀ (deflecting reflection light R _t ) forms a sharp peak, whereas in the latter, the specular reflection light R ₀ and the scattering reflection light R _d have the same light intensity. It can be seen that the dynamic range of a single light receiving / detecting system can be used. Also, according to this, the scattered reflected light R _d
Since all of them are included in the second reflected light, the first reflected light R ₁ is formed only by the deflectable reflected light R _t originally necessary for detecting the deflectable defect. Therefore, the detection of the deflectable defect described later becomes highly accurate.

B. Configuration and Operation of Deflective Defect Detection System Next, the deflectable defect detection based on the first reflected light R ₁ will be described. FIG. 4 is a partial view corresponding to a part of FIG. 1 which is taken out only for explaining the deflective defect detection. Therefore, the scattered reflected light R _d is not drawn in this figure, and the incident laser beam L and the deflectable reflected light R _t are drawn as straight lines having no width for convenience. Further, it is assumed that the surface 7 to be inspected has a bite-like defect 20, which is one mode of the deflectable defect, as shown in FIG. However, the reference plane 7a is a plane perpendicular to the incident laser beam L.

Then, when the laser beam L is reflected by the inclined surface 21 of the bite-shaped defect 20, if the inclination angle of the inclined surface 21 with the reference surface 7a is θ, then the deflectable reflected light R
The deflection angle of _t is 2θ. Then, the deflectable reflected light R _t after passing through the lens 6 is parallel to the incident laser beam L, where Δx = f · tan (2θ) ((θ) with respect to the incident laser beam L. 3) Only the deviation occurs. So in this case,
From the reference position x ₀ on the light receiving surface 10 of the bright spot position detector 9
The deflectable reflected light R _t is incident on the position displaced by x. However, the reference position x ₀ is the light receiving position of the deflectable reflected light R _t (that is, the specularly reflected light R ₀ ) when the surface 7 to be inspected matches the reference surface 7 a and there is no defect.
Therefore, by detecting this Δx, the inclination angle θ can be obtained from the equation (3). In addition, since the inclination angle θ is small in the case of a slight biting or undulation on the precision machined surface, Δx≈f · tan (2θ) (4) can be used as an approximate expression of the above expression (3). .

Thus, the deviation amount Δx is the inclination angle θ of the bite defect 20 or the like.
Therefore, when the deviation amount Δx exceeds a predetermined value, it is possible to determine that a deflectable defect exists.

Therefore, in the light transmittance distribution filter 4, the size of the portion A having a small transmittance is determined by how much the deviation amount Δx is detected. It is part A
This is because if the size is too small, the deviation Δx is slightly increased and the light enters the portion B, and the deflective reflected light cannot be captured as the first reflected light.

In order to make the above determination specifically, first, the deviation amount Δx of the bright spot received by the bright spot position detector 9 is converted into an electric signal level V _D proportional to this Δx. At this time, the light-receiving surface of the bright spot position detector 9 is a light-receiving surface having a continuous spread so that minute changes in the deviation amount Δx can be captured as accurately as possible. Is preferred. Therefore, in this embodiment, a semiconductor position detector (hereinafter, PS) is used as the bright spot position detector 9.
Say D. ) Is used. FIG. 6 (a) shows a one-dimensional PS among such PSDs.
Light-receiving surface 10 of bright spot position detector 9 configured using D
And the bright point S received is obtained by taking the ratio of the photocurrent values extracted from each of the electrodes X _a and X _b.
The signal corresponding to the deviation amount Δx of P is the signal level V in FIG.
Output as _D. In this operation, since the light receiving surface 10 is not a set of discrete elements but has a continuous spread, the light receiving position is detected with high accuracy.

This signal level V _D is the deflectable defect detection circuit 10 of FIG.
It is amplified by the amplifier 101 provided inside 0, and becomes the light receiving position (deviation) detection signal V via the band pass filter 102 provided for the reason described later. This signal V is compared with a predetermined reference value (threshold value) in the comparator 103 at the next stage, and discrimination processing is performed by this threshold value.
Then, the light receiving position detection signal V (hence the inclination angle θ)
When the value exceeds the reference value, a defect detection signal indicating that there is a defect is output.

Therefore, in the following, the operation of this device will be described in more detail with a focus on this comparison / discrimination operation. First, while irradiating the surface 7 to be inspected with the laser beam L from the laser light source 1, a laser beam scanning mechanism (not shown in FIG. 1).
Is used to sequentially scan the surface 7 to be inspected. As such a scanning method, the following method can be appropriately adopted.

A method of scanning a laser beam from the laser light source 1 on the surface 7 to be inspected by using a rotating mirror or a vibrating mirror.

As shown in FIG. 7, when the test subject P is a disk-shaped, while rotating the inspection object P in an arrow A ₁ direction, the inspection object surface 5 by translating the arrow B ₁ direction How to scan.

As shown in FIG. 8, when the inspection object Q is drum-shaped, while rotating the inspection object Q to arrow A ₂ direction, the inspection object surface 7 by translating the arrow B ₂ direction How to scan.

However, since the method of (1) needs to provide a large light receiving lens capable of covering the entire scanning width of the laser beam, when detecting a slight inclination on the surface 7 to be inspected, the scanning method of (2) is used. Is preferred. Further, in the scanning method of, the optical system may be translated instead of the translational motion of the inspection objects P and Q.

While performing such a scan, the deflectable reflected light R _t
When the incident position of is detected by the bright spot position detector 9, the light receiving position detection signal V changes as shown in FIG. In FIG. 9, (a) shows the case where the surface 7 of the object to be inspected is flat, and (b) shows the case where a deflectable defect exists. However, in this embodiment, the signal level is V = 0 when the light receiving position of the deflectable reflected light R _t is the reference position x ₀ in FIG. As you can see from Figure 9,
When the surface 9 to be inspected has a deflectable defect, the light receiving position detection signal V changes with an amplitude according to the inclination angle θ of this defect.

FIG. 10 is a diagram showing variations in the light receiving position detection signal V caused by such a deflective defect, modeled for a single bite-like defect. As shown in this figure, if there is a defect on the surface of the object to be inspected, the light receiving position detection signal V once fluctuates in the (+) or (-) direction and then fluctuates in the opposite sign direction to the reference level (V). = 0). As shown in FIG. 5, if there is an inclined surface 21 inclined in one direction in the defect 20, an inclined surface 22 inclined in the opposite direction is also present, so that the bright spot position This is because the position of the bright spot on the light receiving surface 10 of the detector 9 sequentially returns to x ₀ after sequentially changing in both directions (+) and (−).

Therefore, in this embodiment, as the threshold value set in the comparator 103 in FIG. 1, two values V _H and V _L as shown in FIG. 10 are used. However, these threshold values V _H , V
_L is V _H > 0, V _L <0, and is a value determined according to the limit value of the allowable defect. And V is V _H
When it becomes the above or becomes _VL or less, it is judged that "there is a defect", and the judgment output is output as a defect detection signal.

Next, as shown in FIG. 11, a process when the surface 7 to be inspected is tilted by an angle φ from the reference plane 7a as a whole will be described. At this time, even if there is no defect,
The laser beam L is reflected at a reflection angle corresponding to this angle φ, and the light receiving position of the deflective reflected light R _t on the light receiving surface is displaced from x ₀ . Therefore, the position detection signal V is
It becomes one having an offset level V _B as shown in FIG. (A), when the offset level V _B is increased, the threshold value V _H, the determination of the presence of defects due to V _L becomes difficult.

Therefore, in such a case, a differentiator (not shown) is provided in front of the comparator 103 in FIG. 1 to determine the time derivative ΔV / Δt of the position detection signal V. Considering that this apparatus captures the detection signal while scanning the surface 7 to be inspected, this is the difference ΔV / V for the minute scanning section Δs shown in FIG. It is equivalent to taking Δs.

The signal thus obtained is shown in FIG. 12 (b). As can be seen from this figure, at the position on the surface 7 to be inspected where no defect exists, ΔV is obtained regardless of the presence or absence of the inclination φ. Since / Δs = 0, the signal level ΔV / Δs fluctuates to (+) (−) only at the position where the defect exists. Therefore, it is possible to detect defects by discriminating the threshold values V _H ′ and V _L ′. That is, the detection of the deflectable defect in the present invention can be generally realized not only by the deviation itself of the light receiving position but also by obtaining the amount according to the deviation like the difference in this example.

Further, as shown in FIG. 13, when the object P to be inspected is rotated for scanning, the surface 5 of the object to be inspected causes a surface contact as indicated by an arrow E in the figure, which causes the deflection property. The reflection direction of the reflected light fluctuates within the range of R _{t to} R _t ′ in the figure. In this case, if the output V _D of the bright spot position detector 9 of FIG.
As shown in FIG. 4 (a), a fluctuation V _C having a cycle corresponding to the rotation cycle of the inspection object P is generated. For this reason, it is still difficult to detect defects by the threshold values V _H and V _L.

In order to deal with this, the deflectable defect detection circuit 1 of FIG.
00 is provided with a bandpass filter 102,
The bandpass filter 102 removes the frequency component corresponding to the rotation cycle of the inspection object P. By doing so, an appropriate light receiving position detection signal V as shown in FIG. 14 (b) can be obtained.

Thus, by providing the bandpass filter 102, unnecessary low frequency components are cut off.
As a result, high-frequency components above the defect detection band are also cut, so that signals due to extremely small irregularities and dust that do not affect the quality of the product and various noises can be prevented. The bandpass filter 102 also has an effect of removing the offset level V _B (DC component) of FIG. 12 (a).

As described above, by providing the fluctuation correction means for the light receiving position detection signal V, the device can cope with various situations.

FIG. 15 is a partial schematic diagram showing another configuration example of the deflectable defect detection system. In this example, as the bright spot position detector 9 ',
2 where the light receiving position of the polarized reflected light R _t can be two-dimensionally detected
Use the dimension PSD. Light receiving surface 1 of this two-dimensional PSD
0'is shown in FIG. 6 (b), and the set Y _a , Y _b is further provided on the second electrode in the direction orthogonal to the set X _a , X _b of the electrodes in the one-dimensional PSD, and is incident. The two-dimensional deviation amounts Δx and Δy of the bright spot SP are obtained. Then, the output levels V _x and V _y corresponding to the deviation amounts in both the x and y directions are set to the square amplifier 101 in FIG.
Square amplification is carried out at a and 101b, and the result is added at the adder 104.

The signal (V _x ² + V _y ² ) thus obtained becomes the position detection signal V ² through the bandpass filter 105, and this and the reference values (threshold values) V _H ² and V _L ² are compared. The comparison is made at 106. Then, as in the first embodiment, when V ² > V _H ² or V ² <V _L ² , it is determined that there is a defect. By doing so, it becomes possible to detect bite defects with high accuracy regardless of the direction of the slope of the undulations.

If you also want to detect the direction of defects or undulations, the ratio:
V _y / V _x may be obtained and tan ⁻¹ (V _y / V _x ) may be calculated.

As described above, the defect detection can be performed with high accuracy and easily using either one-dimensional PSD or two-dimensional PSD.
By using D, there is also an effect that it is possible to prevent the influence of extremely small dust existing on the undulating surface or the inclined surface of the defect. The intensity distribution of the bright spots incident on the light receiving surface of the PSD generally has a distribution form as shown in FIG. 16 (a), but the output of the PSD (for example, V
_D ) is due to the fact that the barycentric position X _SM of this distribution is output as the deviation amount Δx. That is, even if the intensity distribution is disturbed as shown in FIG. 16 (b) due to the presence of fine dust, etc.
_SM (hence the detection value Δx) hardly changes, and it is possible to prevent erroneous detection due to minute dust or the like that has little influence on the product quality.

C. Configuration and Operation of Scattering Defect Detection System Next, the scattering defect detection based on the second reflected light R ₂ will be described. Although this scattering defect detection can be configured by using a modified conventional device, this embodiment uses a novel device that can easily identify not only the presence of a defect but also its type. Here, _first , as the photoelectric conversion means 8 in FIG. 1, as shown in FIG. 17, unit photoelectric conversion elements D ₁ , D ₂ , D ₃ , ... (Hereinafter, referred to as “unit element”) are predetermined. The photoelectric conversion element array 80 spatially arranged according to the above rule is used to detect the form of the spatial intensity distribution of the diffraction pattern of the second reflected light R ₂ . Then, the type of scattering defect is also discriminated based on the data on the form of the intensity distribution.

Of the various photoelectric conversion element arrays 80 shown in FIG. 17,
FIG. 1A shows unit photoelectric conversion elements D ₁ , D ₂ , ... Arranged in a matrix. Then, in this method, the photoelectric conversion output pattern obtained from each unit element is compared with the form of the diffraction pattern distribution obtained in advance for the type of defect assumed in advance, and the type of defect is determined by the degree of coincidence. To do.

However, surface defects are roughly classified into linear (streak) defects (first
8 (a)) and point-like (pit-like) defects (Fig. 19 (a)). The diffraction patterns of them are linear diffraction patterns (Fig. 18 (b)) in the former case. In the latter case, the specular diffraction pattern (FIG. 19 (b)) is obtained. And the diffraction pattern (scattering pattern) from such a surface defect is
Although it often has symmetry and periodicity in a polar coordinate system centered on the position of specularly reflected light,
The matrix arrangement of the unit elements as shown in FIG. 3A has symmetry in the Cartesian coordinate system. Therefore, due to the difference in these symmetries, the processing of photoelectric conversion output must be complicated to some extent in the matrix array.

Therefore, by using the symmetry and the periodicity of the diffraction pattern due to the surface defect in the polar coordinate system, a photoelectric conversion element array that can more accurately determine the defect type with a smaller number of unit elements is used. Is desirable.

FIGS. 17 (b) to 17 (d) are views showing such an arrangement example, in which FIG. 17 (b) shows an annular unit element 81 arranged concentrically. FIG. 7C shows fan-shaped unit elements 82 arranged radially. Also, the same figure
(d) is a combination of (b) and (c) above. Of these, the concentric array is suitable for knowing the intensity distribution in the radial direction of the diffraction pattern, and the radial array is suitable for knowing the intensity distribution in the circumferential direction. FIG. 17 (d), which is a combination of both, has these advantages. That is, in the photoelectric conversion element array 80, as shown in the figure, arc-shaped unit elements are arranged concentrically in a partial area of a substantially circular light receiving area, and fan-shaped unit elements are radially arranged in the remaining area. It is arranged. Therefore, the intensity distribution in the radial direction of the diffraction pattern can be simultaneously detected by the arc-shaped unit element, and the intensity distribution in the circumferential direction can be simultaneously detected by the radial unit element, and the type of the surface defect can be more accurately determined with a small number of elements. be able to.

In these arrangements, the arrangement is such that the position where the specularly reflected light enters is the center of the concentric arrangement or radial arrangement.

Returning to FIG. 1, the photoelectric conversion output obtained when the reflected light R enters such a photoelectric conversion element array 80 is processed by the photoelectric conversion signal processing circuit 201 in the scattering defect detection circuit 200, The output level of each unit element is detected and amplified in series or in parallel. The unit element output intensity distribution obtained as a result is illustrated in FIG. This FIG. 20 uses the photoelectric conversion element array 80 having the concentric array as shown in FIG. 17 (b), and FIG.
This is a case where the surface 7 to be inspected in which linear defects are regularly arranged as in (a) is detected. However, the number of unit elements in the photoelectric conversion element array 80 is 32.

As can be seen from FIG. 20, the output obtained by using the transmittance distribution filter 4 is the specular reflection light R
₀ (unit elements D _{1 to} D ₈ ) and scattered reflected light R _d (the same D ₉
.About.D ₃₂ ) have almost the same level, and it is understood that these can be processed simultaneously by a single light receiving / signal processing system. Further, the type of defect can be determined from the form of the diffraction pattern distribution of the scattered reflected light R _d . This may be judged by displaying the distribution etc. of FIG. 20 as it is on a display device or the like and comparing this with the diffraction pattern obtained by the operator in advance for various defects. In order to make it more efficient, the characteristic values such as the height (maximum value) I _p0 , I _p1 , ... Of each peak of the diffraction pattern, its position, and the spread of the peak are extracted as the characteristic value of FIG. The circuit 202 may quantitatively extract, and the comparator 203 may compare the diffraction pattern determination reference (various threshold values) determined in advance for each defect type with the comparator 203 for automatic determination. As the spread of the peak, it is possible to use the detected value of the unit element n (n is an integer) away from the unit element giving the peak, the peak half value width, the standard deviation, and the like.

For example, in the example of FIG. 20, it is determined that there is a defect when the peak of the scattered reflected light exceeds the threshold value I _TH, and when there are a plurality of broad scattered reflected light peaks, FIG. ) Spec-like scattering pattern,
It is judged that there is a point defect. Further, by comparing the intensity ratio or the intensity difference between the specularly reflected light and the scattered reflected light with a predetermined threshold value, the degree of the scattering defect can be known.

D. Modifications The embodiments of the present invention have been described above, but the present invention is not limited to the above embodiments, and the following modifications are possible, for example.

In the above embodiment, the transmittance distribution filter 4 is used as the light separating means, but it is also possible to perform the separation by the small mirror 31 shown in FIG. 21 (a) or the small prism 32 shown in FIG. 21 (b). Is. In this case, since the second reflected light R ₂ is containing only scattered reflection light R _d, as the scattered reflection light detecting means, using a detection system for performing only the defect detection scattering reflected light R _d .

Also, when using the transmittance distribution filter,
Instead of the transmittance distribution filter having the stepwise transmittance distribution as shown in FIG. 2A, a filter having a continuous transmittance distribution as shown in FIG. 2B can be used. In this case, there is also an effect that it is possible to prevent the diffraction of light due to the abrupt change of the transmittance, and to prevent the detected diffraction pattern from including such unnecessary diffraction portion.

INDUSTRIAL APPLICABILITY The present invention can be applied not only to semiconductor wafers and video discs, but also to defect detection of various inspected objects that cause light reflection.

(Effects of the Invention) As described above, according to the present invention, the reflected light from the surface of the object to be inspected is the first reflected light including the deflective reflected light and the second reflected light including the scattered reflected light. By providing a light separating means for separating into, and detecting a deflecting defect and a scattering defect based on each of these reflected lights, without complicating the alignment of the optical system, with a low cost and compact configuration, It is possible to obtain a surface defect detection device capable of detecting both a deflectable defect and a scattering defect. Moreover, in this scattered reflected light detection means, arc-shaped unit elements are arranged concentrically in a partial area of the substantially circular light-receiving area, and
Since the fan-shaped unit elements are radially arranged in the remaining area, the intensity distributions in the radial direction and the circumferential direction of the diffraction pattern can be simultaneously detected, and the type of surface defect can be accurately determined.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an embodiment of the present invention, FIG. 2 is a diagram showing a transmittance distribution of a transmittance distribution filter, and FIG. 3 is a reflected light intensity before and after passing through the transmittance distribution filter. 4 and FIG. 4 are explanatory views for detecting a deflectable defect, FIG. 5 is an enlarged view of a portion G of FIG. 4, FIG. 6 is a view showing a light receiving surface of a PSD, FIG. 7 and FIG. FIG. 9 is a diagram for explaining the scanning method. FIGS. 9 to 14 are diagrams for explaining the principle of the deflectable defect detection. FIG. 15 is a diagram showing a modified example of the deflectable defect detection system. FIG. 17 is a diagram for explaining PSD characteristics, FIG. 17 is a diagram showing an example of a photoelectric conversion element array, FIGS. 18 and 19 are diagrams for explaining scattering patterns for linear defects and point defects, respectively. The figure is an explanatory view of the signal level obtained in the scattering defect detection system, and FIGS. 21 and 22 show this. FIG. 23 and FIG. 24 showing a modification of the invention are explanatory views of a conventional surface defect inspection apparatus. 1 ... Laser light source, 4 ... Transmittance distribution filter, 7 ... Inspected object surface, 8 ... Photoelectric conversion means, 9 ... Bright spot position detector, 100 ... Deflective defect detection circuit, 200 ... Scattering defect detection circuit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shuji Miki 2-3-1 Nonomachi, Shinohara, Nada-ku, Kobe-shi, Hyogo Prefecture (56) References JP-A-60-13247 (JP, A) JP-A-60- 122358 (JP, A) JP-A-51-122464 (JP, A) Actually developed 59-35048 (JP, U)

Claims (1)

[Claims] 1. An object to be inspected is irradiated with a light beam from a light source,
A device for detecting a defect existing on the surface of the object to be inspected by detecting reflected light from the surface of the object to be inspected, wherein the light beam from the light source is irradiated substantially perpendicularly to the surface of the object to be inspected. Means for converting the reflected light into first reflected light including deflectable reflected light,
Light separating means for separating into second reflected light containing scattered reflected light, and a light receiving surface for receiving the first reflected light, and light reception of the deflectable reflected light on the light receiving surface. The light receiving position detecting means for outputting a light receiving position detection signal corresponding to the position, and the arc-shaped unit elements are concentrically arranged in a part of the substantially circular light receiving area, and the fan-shaped unit elements are arranged in the remaining area. A diffused defect among the defects present on the surface of the object to be inspected, which is arranged in a radial pattern, and which comprises a scattered reflected light detecting means for receiving the second reflected light and detecting the scattered reflected light. Is detected based on the light receiving position detection signal, and the scattering defect is detected based on the detection output of the scattering reflected light detecting means.