JPH07140082A - Method for setting discrimination threshold between foreign matter and pattern - Google Patents

Abstract

PURPOSE:To make possible the setting of threshold value that properly discriminates foreign matters from a pattern by, with a clear test sample, generating 2-D distribution figure for both photo-detection voltages of P.S polarized light of a pattern wiring and multiple standard particles of different diameters corresponding to the foreign matter. CONSTITUTION:Against the test sample with no sticking foreign matters, both photo-detection voltages Vp and Vs are measured for P and S polarized components of a wiring pattern. They are digitized with an A/D convertors 51a.51b and stored in the memory area of a RAM 53. Then standard particles of 1mum and 2mum in diameter are stuck to a glass plate in plural pieces, and both voltages Vp and Vs against them are measured and stored in the RAM 53. Then, the data in RAM 53 are read by the micro processor MPU 52, and 2-D distribution figure is outputted to an output device 54. In the distribution figure, the boarder line separating the standard particles from the distributed area of pattern wiring is set, and that is used as the threshold value which discriminates foreign matters from a wiring pattern.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of setting a threshold value for discriminating between a foreign substance attached to an object to be inspected and a pattern wiring formed on the foreign substance.

[0002]

2. Description of the Related Art For a semiconductor IC chip or a TFT (thin film transistor) substrate used for a liquid crystal panel, a resist agent is applied to a silicon oxide film deposited on the surface of a silicon wafer or a glass substrate, and a mask is applied to this. It is manufactured by transferring the pattern of the board. Since the performance deteriorates when foreign matter adheres to the IC chip or the TFT substrate, the presence or absence of foreign matter is inspected by the foreign matter inspection device. However, when optically inspecting the adhered foreign matter, the pattern wiring is detected together with the foreign matter, so it is necessary to distinguish between them. As an optical foreign matter inspection method for a wafer with a pattern wiring, for example, "Japanese Patent Laid-Open No. 61-104243, foreign matter detection method and its apparatus" has been disclosed, and this method can be applied to a TFT substrate. The inspection is being conducted. The outline of the foreign matter inspection apparatus will be described below.

FIG. 3 shows the basic structure of the foreign substance inspection apparatus according to the above-mentioned patent publication. For convenience, the wafer and the TFT substrate are collectively referred to as the inspection object 1. The pattern wiring (PAT) formed on the surface of the inspection object 1 is set in the XY directions, and the inspection object 1
Moves in the X or Y direction by a moving mechanism (not shown). On the other hand, an inspection optical system including a light projecting system 2 and a light receiving system 3 and a signal processing unit 4 are provided. In the light projecting system 2, a P-polarized laser beam L _T (P) is projected from the light source 21 in the X direction at a low angle θ _P with respect to the surface of the inspection object 1.
Further, the S-polarized laser beam L _T (S) from the light source 22 has a high angle θ.
_The two beams L _T (P) and L _T (S) are projected by _S in the Y direction, respectively, are focused by a focusing lens (not shown), and a spot S _P is irradiated on the surface of the inspection object 1. The light receiving system 3 is provided vertically above the inspected object 1, and the pattern wiring formed on the surface of the inspected object 1 and the reflected light L of the foreign matter attached thereto
_{The R} is condensed by the condenser lens 31 of the light receiving system 3 and is divided into two by the beam splitter 32. The one that was divided is
The P-polarized light is detected by the P-polarized light analyzer plate 33.
The light is received by 34, and the received light voltage v _P is output. On the other side, the S-polarized light is detected by the S-polarized light analyzing plate 35, and the light-receiving voltage v _S is output from the light receiver 36. The two received light voltages v _P and v _S are input to the divider 41 of the signal processing unit 4 to calculate the ratio (v _P / v _S ) = k of both, and the ratio k is set to an appropriate threshold value m by the comparator 42. After the comparison, the pattern wiring is removed, only the foreign matter is detected, and the detection pulse p _a is output.

The principle of the above foreign matter detection will be described with reference to FIG. In FIGS. (A) and (b), (a) is a pattern wiring of the inspection object 1, (b) is a relatively small foreign material, and (c) is a relatively large foreign material. Figure (a) shows
When the inspection object 1 is irradiated with P-polarized waves, the surface of the pattern wiring (a) is smooth, so that the P-polarized waves are specularly reflected in the direction of the low angle θ _P , and thus the vertically upward collection is performed. The light is hardly incident on the optical lens 31, and the light receiving voltage v _P of the light receiver 36 is small as shown in the figure. On the other hand, the foreign matters (b) and (c) scatter P-polarized waves, and the scattered light Q changes its polarization plane in a random direction. Therefore, the P-polarized component is received by the photodetector 34 and the S-polarized component is received by the photodetector 36. to be respectively received, the scattered light Q both receiving the voltage so small v _P of small foreign matter (b), v _S is small, a large foreign object
Since the scattered light Q in (c) is large, large received light voltages v _P and v _S are output. Next, Fig. (B) shows the case where the S-polarized wave is irradiated. The S-polarized wave has a high angle θ _S due to the pattern wiring (a).
Since the light is specularly reflected in the direction of, the light is largely collected by the condenser lens 31, and the light receiving voltage v _S of the light receiver 36 is large as shown in the figure. On the other hand, the S-polarized wave also scatters the scattered light Q due to the foreign matter (b) and (c), and is smaller and larger than the small foreign matter (b).
The received light voltages v _P and v _S, which are large with respect to the above, are output. The divider 41 calculates the ratio of the received light voltages v _P and v _S (v _P /
When v _S ) = k is obtained, the waveform shown in (c) is obtained. Since the pattern wiring (a) has v _P <v _S , the ratio k is considerably smaller than 1, but the foreign matters (b) and (c) have a value close to 1 because v _P ≈v _S. An appropriate constant threshold value m is set for each of these waveforms in the comparator 52, and foreign matter values (b) and (c) exceeding this are detected except for the pattern wiring (a) whose peak value does not reach the threshold value m. Then, the detection pulse p _a is output. It should be noted that the above is the basic configuration and the foreign matter detection method based thereon.
Both beams L _T (P), L with different wavelengths
_Although the foreign matter detection performance has been improved by using _T (S), etc., in any case, it is not possible to distinguish between foreign matter and pattern wiring by using the S polarized wave and the P polarized wave and the above principle. There is no change.

[0005]

The above is an explanation in which the detection principle is modeled, and the actual situation is not so simple. That is, since the shape and size of the pattern wiring differ depending on the type of the inspection object 1, the magnitude of the reflected light L _R also varies depending on the type, and the edge thereof is weak,
Since the scattered light Q of the randomly polarized plane is scattered, these influence the both light receiving voltages v _P and v _S , and the above-mentioned ratio k changes.
On the other hand, the size of the foreign matter is as large or small as the model illustrated.
The size of the scattered light Q is not limited to any kind, and the magnitude of the scattered light Q is also different, and the magnitude relationship between the received light voltages v _P and v _S is not simple as in the model. Therefore, when the threshold value m is set to a uniform value or a constant value, the foreign matter and the pattern wiring are not accurately discriminated from each other. On the other hand, it is necessary to determine an appropriate threshold value that can accurately discriminate the two and set the threshold value in the inspection device. The present invention has been made in view of the above, and an object of the present invention is to provide a method of setting a threshold value that accurately distinguishes a foreign substance from a pattern wiring for a foreign substance inspection device.

[0006]

SUMMARY OF THE INVENTION The present invention is a method for setting a threshold value for discriminating between a foreign matter and a pattern, which achieves the above object, wherein the foreign matter inspecting apparatus cleanly inspects the foreign matter. Attach a test sample of the object, measure both light receiving voltages v _S , v _P of the pattern wiring, and measure both light receiving voltage v
Create a two-dimensional distribution map of _S , v _P. Also, for a plurality of standard particles each having at least two kinds of diameters corresponding to the size of the foreign matter, the respective two received light voltages v _S and v _P are measured and plotted in a two-dimensional distribution chart. A boundary line that divides the distribution areas of both the standard particle group and the pattern wiring is set, and this boundary line is used as a threshold value for discriminating between the foreign matter of the inspection object and the pattern wiring. In the above, the respective data of both the light receiving voltages v _S , v _P for the test sample of the object to be inspected and the standard particle group are converted into the two light receiving voltages v _S ,
Store v _P as an address in the two-dimensional memory. Each stored data is output to an output device to create a two-dimensional distribution map, and a boundary line that separates the standard particle group and the pattern wiring is set. Based on this boundary line, valid data "1" and invalid data "0" are set respectively for the standard particle group of the two-dimensional memory and both distribution areas of the pattern wiring. When the data read from the two-dimensional memory is "0", it is ignored as a pattern wiring by the address designation of both the light receiving voltages v _S and v _P obtained by the inspection of the object to be inspected, and when it is "1", it is detected as a foreign matter. The determination is made and the foreign matter pulse is output.

[0007]

In the discrimination threshold setting method described above, the test sample of the clean inspection object to which no foreign matter is attached measures both the light receiving voltages v _S and v _{P of the} pattern wiring, and the two-dimensional distribution chart thereof is obtained. Created. In addition, with respect to a plurality of standard particles each having at least two kinds of diameters corresponding to the size of the foreign matter, the two received light voltages v for each kind
_S , v _P are measured and plotted on a two-dimensional distribution map. A boundary line that divides the distribution areas of both the standard particle group and the pattern wiring is set, and this serves as a threshold value for discriminating between the foreign matter of the inspection object and the pattern wiring. This threshold value is not a constant value as in the conventional case, but both the light receiving voltage v _S of the foreign matter and the pattern wiring,
Since they change depending on the value of v _P and actually match each other, it is possible to accurately discriminate the both. However, in order to realize such a changing threshold value, although it can be performed only by a hard circuit, in the present invention, a soft method is used together, and this is disclosed in claim 2. That is, the respective data of the two light receiving voltages v _S , v _P for the test sample of the object to be inspected and the standard particle group are the two light receiving voltages v _S ,
The data is stored in a two-dimensional memory with v _P as an address, each data is output to an output device, and a two-dimensional distribution map is created. By visually observing this, a boundary line that separates the standard particle group and the pattern wiring is set. . Based on this boundary line, for the standard particle group of the two-dimensional memory and both distribution areas of the pattern wiring,
Valid data "1" and invalid data "0" are set respectively. In the inspection of the object to be inspected, the address of the two-dimensional memory is designated by the measured light receiving voltages v _S and v _P , and when the read data is "0", it is ignored as the pattern wiring, and this is "1". When it is ", it is judged as a foreign matter and a foreign matter pulse is output.

[0008]

1 and 2 show an embodiment of the present invention. FIG. 1 is a block diagram of a threshold value setting section 5, and FIG. 2 is a memory area diagram of a two-dimensional memory (RAM) 53. In FIG. 1, the threshold setting unit 5 includes two A / D converters 51a and 51b, a microprocessor (MPU) 52, and a two-dimensional memory (RAM) 5
3 and an output device 54, each A / D converter 51a, 51b
Are respectively connected to the two light receivers 34 and 35 of the light receiving system 3 of the foreign substance inspection apparatus shown in FIG.

In setting the threshold value, first, a test sample of the object to be inspected 1 such as a patterned wafer or a TFT substrate in which no foreign matter is attached is attached to the inspection device, and the P-polarized component and the S-polarized component of the pattern wiring are set. Both light receiving voltages v _P and v _S are measured. The measured light receiving voltages v _P and V _S are converted into digital voltages V _P and V _S of, for example, 256 gradations by the A / D converters 51a and 51b, and the addresses for the voltages V _P and V _S of the memory area of the RAM 53 are set. Memorized in. In FIG. 2A, the address of the memory area of the RAM 53 has a horizontal axis of voltage V _S and a vertical axis of voltage V _P, and both voltages are normalized in the range of 0 to 1.0. Both voltages V _P and V _{S with} respect to the pattern wiring of the test sample are distributed as shown by, for example, X marks. However, this distribution region is divided into three regions, I, II and III. The region I is v _P <v described in FIG. 4 above.
_This corresponds to the case of _S and is within the straight line of a constant ratio number k ₁ ( _VP / VS). The same applies to the region II, which is within a straight line with a constant ratio k ₂ , but in the region II, the projection angles of the P-polarized wave and the S-polarized wave are interchanged, and the P-polarized wave has a high angle and the S-polarized wave has a low angle. When projected at different angles, V _P <V _S in this case. Further, in the region III, both voltages V _P and V _S are dispersed as shown in the figure due to the difference in the shape and size of the pattern wiring and the scattered light Q due to the edge thereof. Next, a plurality of standard particles each having a diameter of 1 μm and 2 μm are attached to an appropriate glass plate, and both voltages V _P and V _S for these are measured and stored in the RAM 53.
Standard particles of μm are distributed like Δ, 2 μm are distributed like ○,
The range sandwiched by this distribution range and the straight line k _{1 is referred} to as a foreign matter region IV. Read the data of RAM53 by MPU52,
The two-dimensional distribution map is output to the output device 54. Area of this distribution map
A boundary line C is drawn between IV and each of the regions I, II, and III to divide into a foreign substance region and a pattern wiring region, as shown in FIG. Next, in the RAM 53, invalid data "0" is stored in the entire area of the pattern wiring area with the boundary C as the boundary, and valid data "1" is stored in the entire area of the foreign material area IV.

In the inspection of the inspection object 1, both light receiving voltages V _S and V _P are measured, the data of the RAM 53 is read out by the MPU 52 by using these as addresses, and the read out data is "
When it is 0 ", it is ignored because it is a pattern wiring, and it is" 1 ".
In the case of, it is determined that the particle is a particle, and the particle pulse p _a is output to the output device 54.

[0011]

As described above, the threshold value set by the setting method according to the present invention changes depending on the values of the light-receiving voltages v _S and v _P of the foreign matter and the pattern wiring, and actually matches.
The two are accurately discriminated, and an easy-to-execute means using a soft method in combination with a hard circuit for realizing this threshold value is disclosed, and there is a great effect in contributing to the foreign substance inspection technology.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a threshold value setting unit 5 according to an embodiment of the present invention.

2A is a memory region diagram of a two-dimensional memory (RAM) 53, and FIG. 2B is an explanatory diagram of a method of setting a boundary line C that separates a foreign substance region and a pattern wiring region.

FIG. 3 is a basic configuration diagram of a foreign matter inspection apparatus.

FIG. 4 is an explanatory diagram of a foreign matter detection principle in the foreign matter inspection apparatus.

[Explanation of symbols]

1 ... Inspected object of patterned wafer or TFT substrate,
2 ... Projector system, 21, 22 ... Light source, 3 ... Light receiving system, 31 ... Condensing lens, 32 ... Beam splitter, 33, 35 ... Analyzer plate, 34, 36 ...
Light receiver, 4 ... Signal processing unit, 41 ... Divider, 42 ... Comparator, 5 ... Threshold setting unit, 51a, 51b ... A / D converter, 52 ...
Microprocessor (MPU), 53 ... Two-dimensional memory (R
AM), 54 ... Output device, L _T (P) ... P-polarized laser beam,
L _T (S) ... S-polarized laser beam, θ _P ... Low angle, θ _S ...
High angle, PAT ... pattern wiring, L _R ... reflected light, v _P ...
Received voltage of P-polarized component, v _S ... Received voltage of S-polarized component,
k ... specific number, Q ... scattered light, m ... a certain threshold, p _a ... foreign substance pulse, V _P, V _S ... receiving voltage v _P, v digital value of _S, k _1,
k ₂ ... Straight line, I, II, III ... Pattern wiring area, IV ... Standard particle or foreign material area, C ... Boundary line.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location H01L 21/66 J 7630-4M

Claims (2)

[Claims] 1. A laser spot of S-polarized waves and P-polarized waves is applied to the surface of the object to be inspected on which the pattern wiring is formed, and the laser spot is formed by the pattern wiring and foreign matter attached to the surface. Of the reflected light of the S-polarized component and the P-polarized component are received by two light receivers, and the light-receiving voltage v _S of the S-polarized component and the light-receiving voltage v of the P-polarized component output by both the light receivers. _In a foreign matter inspection device that compares the _P and detects the foreign matter by removing the pattern wiring with an appropriate threshold value, mount a clean test sample of the inspected matter in which the foreign matter does not adhere to the foreign matter inspection device. the two light receiving voltage v _S of the pattern wiring of the test sample, a v _P measured, both received voltage is the measured v _S, v _P, to create a two-dimensional distribution diagram of, and the size of the foreign substance Equivalent to, at least two types of straight For each plurality of standard particles having, each of the the seed classification both receiving the voltage v _S,
v _P is measured and plotted on the two-dimensional distribution chart, a boundary line for dividing the distribution area of both the standard particle group and the pattern wiring is set, and the boundary line is set to the foreign matter of the inspection object and the pattern wiring. And a threshold value for discriminating between foreign matter and a pattern, which is used as a threshold value. For wherein said standard particle group and test sample of the object to be inspected, each of the two light receiving voltage v _S, each data v _P, the both light receiving voltage v _S, a v _P as an address 2
The two-dimensional distribution map is created by storing the stored data in a three-dimensional memory, outputting each stored data to an output device, and setting a boundary line that separates the standard particle group and the pattern wiring from the two-dimensional distribution map. Then, based on the boundary line, valid data "1" and invalid data "0" are set respectively for both the standard particle group and the pattern wiring distribution area of the two-dimensional memory, and the inspection of the inspected object is performed. When the data read from the two-dimensional memory is "0", it is ignored as the pattern wiring by the addressing of the two received light voltages v _S and v _P obtained by
The foreign matter and pattern discrimination threshold setting method according to claim 1, wherein the foreign matter pulse is output when it is 1 ".