JP2012117898A - Defect inspection device, defect information acquisition device and defect inspection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a defect inspection device, a defect information acquisition device and a defect inspection method, capable of optimizing further an acquisition amount of a scattered light signal regarding the defect by improving a detection accuracy of the defect to be as the detection object.SOLUTION: The defect inspection device comprises: an inspection light irradiation device 20 for obliquely irradiating a wafer 100 on a specimen support 11 by the inspection light 21; scattered light detectors 30a-30b for detecting scattered light beams 1a-1c from the wafer 100; a defect determination section 45 for logically computing scattered light signals 2a-2b obtained by the scattered light detectors 30a-30b as to the scattered light beams 1a-1c simultaneously generated from a same coordinate on the wafer 100 to determine whether the scattered light signal is a defect signal scattered by the defect or not, and for outputting the scattered light signal only determined as defect signal; a storage section 56 for storing the scattered light signal output from a defect determination section 45; and an operation section 52 for setting a logical arithmetic formula to be used as a criterion of the defect in the defect determination section 45 by combining one selected from a plurality of logical operations or the plural number.

Description

  The present invention inspects foreign matter, scratches, defects, dirt, etc. (hereinafter collectively referred to as “defects”) on the surface of a sample such as a semiconductor wafer (hereinafter simply referred to as “wafer”). The present invention relates to a defect inspection apparatus, a defect information acquisition apparatus, and a defect inspection method.

  In recent years, semiconductor integrated circuit devices (ICs) have been highly integrated and circuit patterns have been miniaturized, and today, circuit patterns having a line width of 1 μm or less have been manufactured. In order to manufacture such miniaturized ICs with a high yield, defects on the wafer surface are detected, the size and shape of the defects are inspected, and the cleanliness of various semiconductor manufacturing equipment and processes is quantitatively grasped. It is important to accurately manage the manufacturing process. Therefore, wafer defect inspection is widely performed in wafer manufacturers, IC manufacturing factories, and the like in order to accurately manage the manufacturing process.

  One technique for this type of defect inspection is to use a dark field image (see Patent Document 1). This is because the inspection light is obliquely irradiated to the wafer to detect the scattered light scattered on the wafer surface, and the position information and size of the defect are estimated from the coordinates on the wafer where the scattered light is estimated to be generated and the intensity of the scattered light. This is a method of recognizing

JP 2008-241570 A

  Here, in the defect inspection apparatus using the dark field image, in order to suppress the noise of the scattered light signal, each scattered light signal of the plurality of scattered light detectors is subjected to an arithmetic process such as an averaging process or an integration process. It has been generally performed to determine whether the scattered light source is a defect by collecting the scattered light signals into one scattered light signal and comparing the calculated scattered light signal with a threshold value.

  However, in such a determination method, only the scattered light signal and the coordinate information after the calculation regarding the detected defect are acquired as the inspection result (in this application, it is stored in the memory), and the data is effective for the shape classification of the defect. Individual scattered light signals of the plurality of possible scattered light detectors are not acquired. On the other hand, even if individual scattered light signals are acquired, the amount of acquired scattered light signals is enlarged, and in order to suppress this, an appropriate threshold must be individually set for each scattered light detector. It is not easy to individually optimize the threshold for many scattered light detectors, and it is easy to optimize the threshold for each scattered light signal to reduce the amount of scattered light signal acquisition. is not.

  On the other hand, in Patent Document 1, at least one scattered light detector related to defect detection is selected according to the characteristics of the scattered light pattern of the defect to be detected, and the scattered light generated at a certain coordinate on the wafer is selected. When the scattered light signals of these detectors (referred to as selection signals) all exceed the corresponding threshold value, it is determined that the defect to be detected exists at the coordinates, and individual defects related to the defect are detected. Scattered light signal is acquired. As described above, in this document, since it is not necessary to appropriately set a threshold value for a scattered light signal not related to defect detection, the threshold value can be easily set in detecting a defect to be detected. On the other hand, the acquisition amount of the scattered light signal can be suppressed by making the determination condition that the scattered light signal selected as the point of defect determination is a certain level or more.

  However, in the method of the same document that determines that a defect is a detection target defect when all of the selection signals exceed the threshold, the amount of acquisition of unnecessary scattered light signals other than the detection target defect signal can be sufficiently suppressed. Not necessarily. For example, if the scattered light pattern is similar and the scattered light detector (in other words, the selection signal) that should output a scattered light signal that exceeds the threshold value overlaps, but there are different types of defects that you want to distinguish as a classification In the determination method of this document, if all the selection signals exceed the threshold value, the scattered light signals of these different types of defects are acquired without distinction.

  The present invention has been made in view of the above. A defect inspection apparatus, a defect information acquisition apparatus, and a defect that can improve the detection accuracy of a defect to be detected and can further optimize the amount of acquisition of a scattered light signal related to the defect. The purpose is to provide an inspection method.

  A logical operation expression constructed using a plurality of logical operations prepared as options is set as a defect determination condition so that a scattered light signal that does not satisfy this determination condition is not acquired.

  Since defect determination conditions can be arbitrarily set using a plurality of prepared logical operations as options, it is possible to improve the detection accuracy of a defect to be detected and further optimize the amount of acquisition of scattered light signals related to the defect. it can.

It is a schematic diagram which shows the defect inspection apparatus which concerns on one Embodiment of this invention. It is a functional block diagram showing schematic structure of the signal filter part with which the defect inspection apparatus which concerns on one Embodiment of this invention was equipped. It is a functional block diagram showing schematic structure of the control apparatus with which the defect inspection apparatus which concerns on one Embodiment of this invention was equipped. It is a figure showing an example of the setting screen of the signal acquisition condition with which the defect inspection apparatus which concerns on one Embodiment of this invention was equipped. It is the figure which represented typically an example of the data of the determination conditions of the defect in the defect inspection apparatus which concerns on one Embodiment of this invention. It is a flowchart showing the output procedure of the defect signal by the signal filter part with which the defect inspection apparatus which concerns on one Embodiment of this invention was equipped. It is the model for comparing the difference in the scattering pattern of the scattered light by a defect shape, and is the top view which looked at the scattering pattern of the scattered light scattered by the defect close | similar to a spherical form from the upper direction of the wafer. It is a schematic diagram for comparing the difference in scattering pattern of scattered light depending on the defect shape, and is a plan view of the scattered pattern of scattered light scattered by a defect having a shape different from a spherical shape as viewed from above the wafer. It is a figure showing the concept of a comparison with a scattered light signal and a threshold value. It is explanatory drawing for demonstrating the effect by the defect inspection apparatus which concerns on one Embodiment of this invention. It is a figure showing the scattered light signal acquired on the determination conditions which could be set conventionally. It is a figure showing the scattered light signal acquired on the determination conditions which can be set with the defect inspection apparatus which concerns on one Embodiment of this invention. It is a figure showing the scattered light signal acquired when the signal which does not need acquisition is designated on the determination conditions which can be set with the defect inspection apparatus which concerns on one Embodiment of this invention.

  Embodiments of the present invention will be described below with reference to the drawings.

  Embodiments of the present invention will be described below with reference to the drawings.

  In the defect inspection apparatus according to the present embodiment, a wafer to be subjected to defect inspection is placed on a sample stage, the wafer is obliquely illuminated while moving the sample stage, and scattered light is detected by a plurality of scattered light detectors. Comparison of a set of scattered light signals (scattered light intensity) scattered at the same coordinates above and simultaneously detected by each scattered light detector and the corresponding threshold values in time series as the scan progresses As a result, a set of signals satisfying the set condition is determined as a scattered light signal caused by a defect (hereinafter, appropriately described as “defect signal”) and acquired together with coordinate information (scanning information). As a result, the scattered light signals of individual scattered light detectors can be acquired flexibly for the detected defects, so there is too much or insufficient information such as useful coordinates for defect classification in addition to defect coordinate and size information. It can be acquired with restraint.

  In the specification of the present application, “acquiring scattered light signals” means storing the scattered light signals in the storage unit. For scattered light signals that are not determined to be defective signals, Not acquired due to suppression. The present embodiment is significant in that the degree of freedom in setting the condition for defect determination is greatly improved when acquiring the scattered light signal as defect information without excess or deficiency. Hereinafter, an embodiment of the defect inspection apparatus of the present invention will be specifically described.

1. Constitution
(1) Defect Inspection Apparatus FIG. 1 is a schematic diagram showing a defect inspection apparatus according to an embodiment of the present invention.

  The defect inspection apparatus shown in FIG. 1 includes a stage apparatus 10 on which a wafer 100 is placed, an inspection light irradiation apparatus 20 that obliquely irradiates inspection light (laser light) 21 on the surface of the wafer 100 on the stage apparatus 10, and A plurality of scattered light detectors 30a-30c that detect scattered light 1a-1c from wafer 100 and output scattered light signals 2a-2c, respectively, and defect signals are selected from the scattered light signals of scattered light detectors 30a-30c. A defect information acquisition device 40, and a control device 50 that controls the stage device 10, the inspection light irradiation device 20, and the defect information acquisition device 40 are provided.

(2) Stage device 10
The stage apparatus 10 includes a sample stage 11 that holds the wafer 100 horizontally and a sample stage moving mechanism 12 that moves the sample stage 11. The sample stage moving mechanism 12 includes a θ table 13 that rotates the sample stage 11 in the horizontal plane in the θ direction around the vertical axis, and an XY table 14 that moves the sample stage 11 and the θ table 13 in the horizontal direction (XY direction). And an automatic focusing mechanism (not shown) for automatically focusing the inspection light 21 by moving the sample table 11 and the tables 13 and 14 in the vertical direction (Z direction). The stage apparatus 10 appropriately moves the XY table 14 in the XY directions while rotating the θ table 13 in accordance with a command signal from the control apparatus 50, and moves the wafer 100 relative to the inspection light 21. As a result, the surface of the wafer 100 is scanned with the inspection light 21. The command signal instructing the operation of the θ table 13 and the XY table 14 during the scanning is associated with the defect signal output from the defect information acquisition device 40 by the control device 50, and the detected defect signal is generated. Coordinate information on the wafer 100 is stored in the storage unit 56 of the control device 50 together with the defect signal.

(3) Inspection light irradiation device 20
The inspection light irradiation device 20 is positioned obliquely above the stage device 10 and constitutes an irradiation optical system together with a condenser lens (not shown) that condenses the inspection light 21, and the light of the inspection light 21 on the wafer 100. The axis is inclined with respect to a line perpendicular to the surface of the wafer 100. The inspection light 21 irradiated obliquely onto the surface of the wafer 100 from the inspection light irradiation apparatus 20 is condensed by the condenser lens and irradiated onto the wafer 100 placed on the stage apparatus 10 at a low angle.

(4) Scattered light detectors 30a-30c
The scattered light detectors 30a-30c are located above the wafer 100 on the stage device 10, and collect and detect scattered light 1a-1c generated by the irregular reflection of the inspection light 21 on the surface of the wafer 100, respectively. To do. The detection signals 2a-2c of the scattered light detectors 30a-30c are respectively input to the A / D converters 31a-31c and converted into digital signals that numerically represent the scattered light intensity. In the present embodiment, the case where three scattered light detectors 30a to 30c are provided is illustrated, but the number of scattered light detectors may be plural (that is, two or more), and may be two or four or more. . In order to improve the required defect classification accuracy, a scattered light detector having a different installation angle in the plan view and the side view can be further added.

(5) Defect information acquisition device 40
The defect information acquisition device 40 includes an arithmetic processing unit 41 that performs arithmetic processing on the scattered light signals 2a to 2c, and a signal filter unit 42 that executes defect determination and the like.

(5-1) Arithmetic processing unit 41
The arithmetic processing unit 41 inputs the individual scattered light signals 2a-2c of the scattered light detectors 30a-30c, and performs predetermined mathematical arithmetic processing (for example, averaging processing, integration processing, etc.) based on the scattered light signals 2a-2c. ) To calculate one scattered light signal 2x with less noise. The scattered light signal 2x calculated by the arithmetic processing unit 41 is also converted into a scattered light signal that can be used for defect determination and stored in the storage unit 56 in the same manner as the individual scattered light signals 2a-2c of the scattered light detectors 30a-30c. included.

(5-2) Signal filter unit 42
The signal filter unit 42 removes signals other than the defect signal from the scattered light signals 2a-2c and 2x that are input as needed in time series, and selects only the defect signal that satisfies a preset condition and selects the storage unit. 56 is a circuit to output to 56.

  FIG. 2 is a functional block diagram illustrating a schematic configuration of the signal filter unit 42.

  As shown in FIG. 2, the signal filter unit 42 includes comparison necessity discrimination units 43a-43c, 43x, threshold value comparison units 44a-44c, 44x, a defect determination unit 45, and acquired signal discrimination units 46a-46c. , 46x.

(I) Comparison necessity discrimination part 43a-43c, 43x
Information indicating whether or not each of the scattered light signals 2a-2c and 2x needs to be compared with a threshold value for defect determination is set in the comparison necessity discrimination units 43a to 43c and 43x. These comparison necessity discrimination units 43a-43c, 43x discriminate whether or not the threshold value comparison units 44a-44c, 44x need to determine the magnitude relationship between the scattered light signal and the threshold value.

(Ii) Threshold comparison units 44a-44c, 44x
In the threshold comparison units 44a-44c, 44x, threshold values used for defect determination are set for the individual scattered light signals 2a-2c, 2x, and the corresponding comparison necessity discrimination unit “comparison determination required”. Is compared with the threshold value, and the determination information of the magnitude relation is added to the defect determination unit 45 and output to the defect determination unit 45. . The threshold comparison section discriminated as “comparison determination unnecessary” by the corresponding comparison necessity discrimination section does not compare the scattered light signal input from the corresponding comparison necessity discrimination section with the threshold value, and is defective as it is. It outputs to the determination part 45.

(Iii) Defect determination unit 45
The defect determination unit 45 determines whether the set of scattered light signals 2a-2c and 2x by the scattered light detectors 30a-30b for the scattered light 1a-1c generated simultaneously from the same coordinates on the wafer 100 is a defect signal scattered by a defect. It is a processing unit that determines whether or not, selects only the scattered light signal of the group determined to be a defect signal, and outputs to the acquired signal discriminating units 46a-46c-46x. The defect determination unit 45 performs a logical operation on the scattered light signals 2a-2c and 2x to determine whether or not the scattered light signals 2a-2c and 2x are defect signals scattered by defects. Here, the logical operation expression used as the defect determination condition is constructed by combining the comparison results of the magnitude relationship with respect to the threshold values of the scattered light signals 2a-2c and 2x by a logical operation (described later) prepared as an option. The defect determination unit 45 is set.

(Iv) Acquired signal discriminators 46a-46c, 46x
The acquired signal discriminating units 46a-46c, 46x discriminate whether or not the set of scattered light signals 2a-2c, 2x determined to be defect signals can be output, and the scattered light signal 2a input from the defect determining unit 45. -2c, 2x are set individually for the scattered light signals 2a-2c, 2x, as to whether to output to the control device 50 to store them in the storage unit 56.

(6) Control device 50
FIG. 3 is a functional block diagram illustrating a schematic configuration of the control device 50.

  The control device 50 includes a control device main body 51, an operation unit 52, and a display unit 53.

(6-1) Control device body 51
The control device main body 51 includes an input / output unit 54, a calculation unit 55, and a storage unit 56.

  The input / output unit 54 is an interface for exchanging signals among the stage device 10, the inspection light irradiation device 20, the defect information acquisition device 40, the operation unit 52, and the display unit 53.

  The calculation unit 55 executes various calculation processes in accordance with signals input from the operation unit 52, the stage device 10, the defect information acquisition device 40, and the like or a program stored in advance, and the display unit 53, the stage device 10, the inspection light irradiation device. 20 and various signals for the defect information acquisition device 40 and the like are calculated.

  The storage unit 56 stores various signals and programs input to the control device main body 51. The defect signal input from the defect information acquisition device 40 is stored in the storage unit 56 in association with the coordinate information. In addition, data of logical operation choices that are elements of the determination conditions are also stored in a predetermined area of the storage unit 56 in advance. As logical operation options, various logical operations such as logical product (AND), logical sum (OR), negation (NOT), negative logical product (NAND), exclusive logical sum (XOR), negative logical sum (NOR), etc. Can be used.

(6-2) Operation unit 52
The operation unit 52 is an interface for an operator to input an instruction to the control device main body 51. In this embodiment, the defect determination unit 45 of the defect information acquisition device 40 determines a defect by operating the operation unit 52. The judgment conditions used in the above are constructed on the operation screen described later. In this embodiment, it is determined whether or not the pair of scattered light signals 2a-2c and 2x by the scattered light detectors 30a-30c for the scattered light generated simultaneously from the same coordinates on the wafer 100 are defect signals scattered by the defect. The determination condition to be set is appropriately constructed by a logical operation expression, and is set by combining one or a plurality selected from a plurality of logical operations prepared as options. The operation unit 52 functions as a condition setting unit that sets the determination condition.

(6-3) Display unit 53
The display unit 53 is a display device such as a liquid crystal monitor that displays display contents according to a display signal from the control device main body 51, and a setting screen for performing various settings such as defect determination and output of a defect signal by the signal filter unit 42. 60 (see FIG. 4) and various screens such as the result of defect inspection are displayed.

(7) Setting screen 60
FIG. 4 is a diagram illustrating an example of a setting screen for signal acquisition conditions.

  A setting screen 60 shown in FIG. 4 is a screen displayed on the display unit 53 by the control device main body 51 in response to an operation signal from the operation unit 52. On this setting screen 60, a comparison necessity setting area 61, a threshold setting area 62, a determination condition setting area 63, an acquisition signal setting area 64, and a logical operation selection area 65 are displayed.

(7-1) Comparison necessity setting area 61
The comparison necessity setting area 61 is an area for setting the comparison necessity discrimination sections 43a-43c, 43x of the signal filter section 42, and the scattered light signals 2a-2c, 2x are individually check boxes 61a-61c, 61x. have. By selecting a signal to be used for defect determination, operating the operation unit 52 and checking the corresponding check box, a scattered light signal with a check is a signal used for defect determination, a scattered light signal without a check Is set as a signal that is not used for defect determination, and setting information as to whether or not each threshold comparison unit performs comparison determination with a threshold value is stored in the corresponding comparison necessity setting unit. FIG. 4 illustrates a state in which the threshold value comparison units 44a to 44c are selected as threshold value comparison units that perform comparison with the threshold value and the check boxes 61a to 61c are checked.

(7-2) Threshold setting area 62
The threshold value setting area 62 is an area for setting the threshold value comparison sections 44a-44c, 44x of the signal filter section 42. The threshold value input fields 62a-62c are individually set for the scattered light signals 2a-2c, 2x. , 62x. By operating the operation unit 52 and inputting a threshold value into each threshold value input field for the scattered light signal used for defect determination, a threshold value is set in the corresponding threshold value setting unit. FIG. 4 illustrates a state in which threshold values are input in the threshold value input fields 62a-62c for the scattered light signals 2a-2c used for defect determination. In the figure, for convenience, the input threshold values are replaced with α, β, and γ, but these are threshold values to be compared with the quantified scattered light signals 2a-2c and 2x. Actually, a numerical value is input.

(7-3) Logical operation selection area 65
The logical operation selection area 65 is an area for displaying logical operation choices for constructing the determination condition. In FIG. 4, an AND icon 65A for using the logical product (AND) and a logical sum (OR) are used. In this example, an OR icon 65B, a knot icon 65C for using negation (NOT), and a NAND icon 65D for using NAND (NAND) are prepared as options. Although not in the example of FIG. 4, other logical operations such as exclusive OR (XOR) and negative OR (NOR) can be prepared. Each logic operation icon 65A-65D is dragged and dropped into the determination condition setting area 63, and the scattered light signal used for defect determination is combined by the logical operation, thereby setting a defect determination condition.

(7-4) Determination condition setting area 63
The determination condition setting area 63 is an area in which the defect determination section 45 of the signal filter section 42 is set. This operation is performed in accordance with the operation of the comparison necessity setting area 61, the threshold setting area 62, and the logical operation selection area 65. In the determination condition setting area 63, the coupling state between the scattered light signal used for defect determination and the logical operation is displayed with a symbol or the like, and the determination condition is schematically displayed. The defect determination conditions set in the determination condition setting area 63 are stored in the defect determination unit 45.

Since the scattered light signal and the logical operation for combining the scattered light signals can be arbitrarily selected, for example, by using the AND icon 65A or the OR icon 65B and the knot icon 65C or the NAND icon 65D together, the scattered light signals 2a-2c, The determination condition includes that at least one scattered light signal selected from 2x exceeds a corresponding threshold value and that at least one scattered light signal selected from other signals is equal to or lower than the corresponding threshold value, It is also possible to determine a set of scattered light signals satisfying both conditions simultaneously as a defect signal. FIG. 4 illustrates a case where the determination condition is set as (scattered light signal 2a) AND ((scattered light signal 2b) NAND (scattered light signal 2c)). That is,
(A) the scattered light signal 2a exceeds the corresponding threshold value α, and
(B) In this example, when the scattered light signals 2b and 2c are equal to or less than the corresponding threshold values β and γ, the set of the scattered light signals 2a to 2c and 2x is determined to be a defect signal.

  It is assumed that the determination condition is basically constructed by combining a plurality of the same or different logical operations. For example, when there are two scattered light signals used for defect determination, In some cases, the calculation is used alone, or when there is only one scattered light signal used for defect determination, no logical operation is used, and the determination process is based on whether or not the defect signal simply exceeds the threshold value. May be executed.

  In addition, the setting of the determination condition on the setting screen 60 can of course be built from scratch with a complete manual setting, but for example, a name can be stored for each defect type and a defect can be detected. The accuracy of the determination condition can be gradually improved by finely adjusting the determination condition each time and overwriting the file or saving the file with a different name.

(7-5) Acquisition signal setting area 64
The acquisition signal setting area 64 is an area for setting the acquisition signal discriminating units 46a-46c, 46x, and has check boxes 64a-64c, 64x individually for the scattered light signals 2a-2c, 2x. When it is determined that a certain set of scattered light signals 2a-2c, 2x generated simultaneously at the same coordinates is a defect signal, which signal is output to the control device 50 and stored in the storage unit 52? Is selected, and the corresponding check box is checked by operating the operation unit 52, so that the scattered light signal that is checked is output to the control device 50, and the scattered light signal that is not checked is defective. Even if it is a signal, it is set as a signal that is not output to the control device 50, and setting information is stored in a corresponding acquired signal selection unit. FIG. 4 illustrates a state where the scattered light signal 2a-2c is selected and the check boxes 64a-64c are checked. That is, when it is determined that a certain set of scattered light signals 2a-2c, 2x is a defect signal, only the scattered light signal 2a-2c of the defect signals is acquired, and the scattered light signal 2x is not acquired. It is.

(8) Determination Condition Data FIG. 5 is a diagram schematically showing an example of defect determination condition data.

  The table 80 illustrated in FIG. 5 exemplifies the data of the determination condition illustrated in the determination condition setting area 63 of FIG. 4, and the determination condition includes two logical operations (AND and NAND), so that the row 84 , 85. Columns 81a to 81c and 81x represent information indicating whether or not the scattered light signals 2a to 2c and 2x are used for defect determination, respectively, and are used (determine the magnitude relationship with the corresponding threshold value). A light signal is represented by “◯”, and a scattered light signal not used (does not determine the magnitude relationship with the threshold value) is represented by “−”. “◯” and “−” are determined by the setting of the comparison necessity setting area 61. Columns 82 and 83 represent the logical operations selected in the logical operation selection area 65. Column 82 represents a logical operation applied to the condition of the same row, and column 83 represents a logical operation applied to the condition of the next row.

  As described above, the logical arithmetic expression illustrated in the determination condition setting region 63 of FIG. 4 is (scattered light signal 2a) AND ((scattered light signal 2b) NAND (scattered light signal 2c)), and (A) scattered light. When the optical signal 2a exceeds the corresponding threshold value α and (B) the scattered light signals 2b and 2c are both equal to or lower than the corresponding threshold values β and γ, the scattered light signals 2a-2c and 2x Is a determination condition for determining that the signal is a defect signal. In the example of FIG. 5, the rows 84 and 85 represent the conditions (A) and (B), respectively, and the row 84 simply represents the condition “whether or not the scattered light signal 2a exceeds the threshold value α”. On the other hand, in row 85, the logical operation in column 82 is set to NAND and represents the condition "whether both scattered light signals 2b and 2c are equal to or less than the corresponding threshold values β and γ, respectively". Since AND is set as a logical operation in the column 83 of the row 84, the conditions (A) and (B) of the rows 84 and 85 are combined by AND to constitute the determination condition.

2. Defect Inspection Procedure Subsequently, the defect inspection procedure in this embodiment will be described.

(1) Condition setting First, the defect determination condition is set on the setting screen 60 based on the feature of the defect to be detected, or the determination condition file corresponding to the defect type to be detected is opened, and if necessary In the setting screen 60, adjustments are made to the determination conditions. Here, in accordance with the determination condition of the setting screen 60 illustrated in FIG. 4 above, the scattered light pattern of the defect to be detected is
Judgment is made from scratch for defects having characteristics that (a) the scattered light 1a incident on the scattered light detector 30a is strong and (b) the scattered light 1b, 1c incident on the scattered light detectors 30b, 30c is weak. The case where conditions are set is illustrated.

  In this case, since the scattered light signal 2x is not used for defect determination, the check box 61x is unchecked in the setting screen 60 and the check boxes 61a-61c are checked. Then, the scattered light intensity α that should be exceeded by the scattered light signal 2a from the defect is input as a threshold value to the threshold value input column 62a, and the scattered light signal 2a from the defect is input to the threshold value input columns 62b and 62c. If so, the scattered light intensities β and γ that are not likely to be exceeded (there is a high possibility that they are other types of defects or are not likely to be defects) are input as threshold values. The threshold value input column 62x may be blank.

Next, based on the feature (b) of the scattered light pattern, the scattered light signals 2b and 2c are designated, and the NAND icon 65D is dragged and dropped onto the determination condition setting area 63. Based on the feature (a), Then, the scattered light signal 2a and the NAND symbol are designated, and the AND icon 65A is dragged and dropped into the determination condition setting area 63. Thereby, a determination condition of (scattered light signal 2a) AND ((scattered light signal 2b) NAND (scattered light signal 2c)) is set,
(A) the scattered light signal 2a exceeds the corresponding threshold value α, and
(B) When both the scattered light signals 2b and 2c are equal to or less than the corresponding threshold values β and γ, the set of the scattered light signals 2a to 2c and 2x is determined to be a defect signal.

  Finally, when the scattered light signal 2x is not necessary as a defect signal component, the check box 64x is unchecked in the acquisition signal setting area 64 and the check boxes 64a to 64c are checked.

(2) Inspection execution
(2-1) When the scanning operation unit 52 is operated to instruct to start an inspection, the control device 50 starts scanning the wafer 100 according to a program stored in advance. First, the θ table 13 is rotated by a command signal from the control device 50, and the inspection light irradiation device 20 irradiates the wafer 100 with the inspection light 21 at a low angle. Thereafter, the XY table 14 is moved in the XY direction by a command signal from the control device 50, and the inspection light 21 is scanned on the wafer 100. When the inspection light 21 is irradiated onto the wafer 100, scattered light 1a-1c in the dark field is generated from a defect on the surface of the wafer 100 or a circuit pattern (after pattern formation). The scattered light 1a-1c is incident on the scattered light detectors 30a-30c.

  The scattered light signals 2a-2c from the scattered light detectors 30a-30c are converted (digital signals) into numerical values representing the scattered light intensity by the A / D converters 31a-31c, respectively, and input to the defect information acquisition device 40. The The scattered light signal 2a-2c input to the defect information acquisition device 40 is input to the arithmetic processing unit 41 and the comparison necessity discrimination unit 43a-43c of the signal filter unit 42, respectively. The scattered light signals 2 a-2 c input to the arithmetic processing unit 41 are subjected to predetermined arithmetic processing and are combined into one scattered light signal 2 x with less noise, and input to the comparison necessity discrimination unit 43 x of the signal filter unit 42. Is done. Scattered light signals 2 a-2 c and 2 x for scattered light 1 a-1 c incident on the scattered light detectors 30 a-30 c simultaneously (or within a preset minute time range) are generated at the same coordinates on the wafer 100. It is treated as a set of scattered light signals and is associated with coordinate information sent from the control device 50.

(2-2) Defect Information Acquisition FIG. 6 is a flowchart showing a defect signal output procedure by the signal filter unit 42.

  The flowchart of FIG. 6 shows processing for a set of scattered light signals 2a-2c and 2x with respect to the scattered light 1a-1c generated simultaneously from the same coordinates on the wafer 100, and the scattered light signal 2a- inputted as needed. The processing of FIG. 6 is executed for each set of 2c and 2x.

<Step 101>
In step 101, the validity flag of the comparison necessity discriminating units 43a-43c, 43x is checked, and the threshold value comparing units 44a-44c, 44x are to compare the scattered light signals 2a-2c, 2x with the threshold values. Are distinguished from each other. Under the setting exemplified in the setting screen 60 of FIG. 4, since the valid flag is set only in the comparison necessity discrimination unit 43a-43c, the threshold value comparison units 44a-44c corresponding to the comparison necessity discrimination unit 43a-43c. Each of the scattered light signals 2a-2c is compared with the threshold value in FIG. 2, and the scattered light signal 2x input to the threshold value comparing unit 44x is not compared with the threshold value.

<Step 102>
In step 102, the threshold value comparison unit to which the valid flag is attached by the corresponding comparison necessity discrimination unit compares the input scattered light signal with the threshold value, and determines the magnitude relation with respect to the threshold value. Under the setting illustrated in the setting screen 60 of FIG. 4, since the valid flag is set only in the comparison necessity discrimination unit 43a-43c, the threshold value comparison unit 44a-44c has the threshold value of the scattered light signal 2a-2c. Specifically, the threshold value comparing unit 44a determines whether or not the scattered light signal 2a exceeds the threshold value α, and the threshold value comparing units 44b and 44c determines whether the scattered light signal 2b is compared with the values α, β, and γ. , 2c are determined to be less than or equal to threshold values β and γ, respectively. In this case, if the scattered light signal 2a is a value larger than the threshold value α, it is input to the defect determination unit 45 together with information to that effect, and if the scattered light signal 2a is a value equal to or smaller than the threshold value α, the defect is not given information. Input to the determination unit 45. On the other hand, if the scattered light signals 2b and 2c are values below the threshold values β and γ, they are input to the defect determination unit 45 together with information to that effect, and if the values are larger than the threshold values β and γ, the information is displayed. It is input to the defect determination unit 45 without being attached. The threshold comparison unit 44x does not compare the scattered light signal 2x with the threshold value, and the scattered light signal 2x is input to the defect determination unit 45 via the threshold comparison unit 44x without any information. The

<Step 103>
In step 103, a defect determination process is executed by the defect determination unit 45 based on information given to the scattered light signals 2a-2c, 2x by the threshold comparison units 44a-44c, 44x. Under the settings exemplified in the setting screen 60 of FIG.
(A) the scattered light signal 2a exceeds the corresponding threshold value α, and
(B) A set of scattered light signals 2a-2c and 2x that satisfies the determination condition that the scattered light signals 2b and 2c are equal to or less than the corresponding threshold values β and γ is determined to be a defect signal. The set of scattered light signals 2a-2c, 2x that does not satisfy this determination condition is determined not to be a defect signal, and the defect determination unit 45 converts the scattered light signals 2a-2c, 2x into acquired signal discrimination units 46a-46c, 46x. The procedure shown in FIG. 6 is terminated by shutting off without outputting. On the other hand, the set of scattered light signals 2a-2c, 2x that satisfy the determination condition is determined to be a defect signal, and the defect determination unit 45 obtains the scattered light signals 2a-2c, 2x as acquired signal discriminating units 46a-46c, 46x. Output to.

<Step 104>
In step 104, the effective flags of the acquisition signal discriminating units 46a-46c, 46x are checked, and the scattered light signals 2a-2c, 2x input to the acquisition signal discrimination units 46a-46c, 46x are output to the storage unit 56, or The scattered light 2a-2c-2x is discriminated whether it is blocked without being output. Under the setting illustrated in the setting screen 60 of FIG. 4, since the valid flag is set only in the acquisition signal discriminating unit 46a-46c, the scattered light signal 2a-2c input to the acquisition signal discriminating unit 46a-46c is stored in the storage unit. The scattered light signal 2x output to 56 and input to the acquired signal discriminating unit 46x is blocked without being output to the storage unit 56.

<Step 105>
In step 105, when the scattered light signals 2a-2c, 2x are input to the acquired signal discriminating units 46a-46c, 46x, the scattered light signal is output to the storage unit 56 only from the acquired signal discriminating unit with the valid flag. Is done. Under the setting illustrated in the setting screen 60 of FIG. 4, since the effective flag is set only in the acquisition signal discriminating unit 46a-46c, the scattered light signal 2a-2c input to the acquisition signal discrimination unit 46a-46c is controlled by the control device. The scattered light signal 2x that is output to 50 and stored together with the coordinate information in the storage unit 56 and input to the acquisition signal discrimination unit 46x is not stored in the storage unit 56 but is blocked by the acquisition signal discrimination unit 46x.

  The signal filter unit 42 executes the above-described steps 101-105 for each set of scattered light signals 2a-2c, 2x that are input as needed, determines that the signal is a defect signal due to a defect on the wafer 100, and Only the signals instructed to be acquired are selected and stored in the storage unit 56.

3. Effect
(1) Conventional technical problems FIGS. 7 and 8 are schematic diagrams for comparing the difference in scattering pattern of scattered light depending on the defect shape, and FIG. 7 shows the scattering pattern of scattered light scattered by a defect close to a sphere. FIG. 8 is a plan view of a scattered pattern of scattered light scattered by a defect having a shape different from a spherical shape, as viewed from above the wafer 100.

  7 and 8, defects X1 and X2 exist on the surface of the wafer 100, respectively, and the defects X1 and X2 are generated from the defects X1 and X2 when the inspection light irradiation device 20 irradiates the defects X1 and X2. The scattered light 1a-1c is detected by the scattered light detectors 30a-30c. The scattered light 1a-1c does not necessarily scatter uniformly in all directions, and the intensity variation of the scattered light 1a-1c differs depending on the shapes of the defects X1 and X2. Specifically, the defect X1 may be nearly spherical as shown in FIG. 7 and the intensity of the scattered light 1a-1c may be substantially equal, whereas the shape of the defect X2 is far from the spherical shape as shown in FIG. The intensity of the scattered light 1a-1c may vary due to the shape of the defect X2, such that the intensity of the scattered light 1b, 1c is significantly weaker than the intensity of the scattered light 1a. .

  As shown in FIG. 9, as in a general defect inspection apparatus, the scattered light signals 2a-2c of the scattered light detectors 30a-30c are not used for defect determination, and the scattered light signals 2a-2c are processed. When one scattered light signal 2x with less noise is compared with the threshold value σ and the scattered light signal 2x exceeding the threshold σ is simply determined as a defect signal, the acquired defect signal is scattered light. Since only the signal 2x and its coordinate information are obtained and the scattered light signal 2a-2c is not acquired, the amount of information for analyzing the shape of the defect is not always sufficient.

  However, if the individual scattered light signals 2a-2c are to be acquired together, an appropriate threshold must be set for each of the scattered light signals 2a-2c in order to suppress an increase in the amount of acquired scattered light signals. I must. It is not easy to individually optimize the threshold values of the scattered light signals 2a to 2c, and the amount of the scattered light signal acquired may be significantly increased due to a slight difference in threshold setting.

  Therefore, for example, one or a plurality of signals used for the defect determination are selected from the scattered light signals 2a-2c and 2x according to the feature of the defect, and any of the signals selected as the defect determination signal corresponds. When the threshold value is exceeded, it is considered that the set of the scattered light signals 2a-2c, 2x is determined as a defect signal (for convenience, this is appropriately described as “determination condition that can be set in the past”). ). In this case, since not only the scattered light signal 2x with reduced noise but also the scattered light signal 2a-2c, which is a component thereof, are acquired together, not only the coordinates and size of the defect but also the classification and analysis of the shape It is beneficial. Further, since only the selected scattered light signal is used for defect determination among the scattered light signals 2a-2c, 2x, the threshold value is set as compared with the case where all the scattered light signals are compared with the threshold value. And adjustment becomes easy.

  However, under “judgment conditions that can be set in the past”, for example, although the scattered light pattern is similar to some extent and the scattered light detectors that should detect scattered light exceeding the threshold value are common, they are distinguished as types. If there are different types of defects, the scattered light signals are acquired without distinction for these different types of defects as long as the selection signals all exceed the threshold value, and the amount of unnecessary scattered light signals acquired can be reduced. There was room for improvement.

(2) Advantage of this embodiment
(2-1) Flexibility of determination conditions Hereinafter, the superiority of the determination conditions that can be set in the present embodiment will be described while specifically comparing with the determination conditions that can be set conventionally.

  Here, FIG. 10 is an explanatory diagram for explaining the superiority of the present embodiment.

  As shown in FIG. 10, for example, when the threshold values are set to 20, 30, 25, and 27 for the scattered light signals 2a-2c and 2x, the scattered light signal 2a-2c during the time t1-t6. Is assumed to change as shown in FIG. Moreover, although only the scattered light signals 2a-2c, 2x at the time t3 are true defect signals to be detected, the scattered light signals 2a-2c, 2x at the time when the determination condition is satisfied are both acquired. To do.

  First, a signal acquired under “determination conditions that can be set in the past” is specified. Here, the scattered light signals 2a and 2b are used as determination conditions. When the scattered light signals 2a and 2b exceed the corresponding threshold values (30 and 25), the scattered light signals 2a and 2b It is determined that the scattered light signals 2a-2c and 2x generated at the same time are defect signals. In this case, the signal filter unit 42 obtains the scattered light signals 2a-2c and 2x at time t3, which are true defect signals, as shown in FIG. , 2b exceed the corresponding threshold values 30, 25, and the scattered light signals 2a-2c, 2x at times t1, t5, t6 are also acquired. That is, in addition to the true defect signal, a total of 12 unnecessary scattered light signals at times t1, t5, and t6 that are not actually caused by the defect to be detected are acquired.

  Next, the scattered light signal acquired under the determination conditions that can be set in the present embodiment is specified. Here, a logical operation expression is constructed by combining AND and NOT, and in addition to the scattered light signals 2a and 2b exceeding the threshold value (30, 25), the scattered light signal 2c is equal to or lower than the threshold value (27). The determination condition is to satisfy the above simultaneously. In this case, as shown in FIG. 12, in addition to the scattered light signals 2a-2c and 2x at time t3, which are true defect signals, unnecessary signals acquired are scattered light signals 2a-2c and 2x at time t1. It becomes only. That is, acquisition of a total of six signals at times t5 and t6 among the unnecessary scattered light signals acquired in the example of FIG. 11 is suppressed.

  As described above, according to the present embodiment, a logical operation expression can be constructed as a defect determination condition by arbitrarily combining a plurality of prepared logical operation options, so the defect determination condition is flexibly set. It is possible to improve the detection accuracy of the defect to be detected and to further optimize the acquisition amount of the scattered light signal related to the defect, and to suppress the acquisition amount of the unnecessary scattered light signal and enlarge the acquisition data Can be suppressed.

(2-2) Further suppression of unnecessary signal acquisition amount In the case of this embodiment, the scattered light signal determined as the defect signal by the defect determination unit 45 by providing the acquisition signal discriminating units 46a-46c, 46x. Only the scattered light signal designated from 2a-2c and 2x can be discriminated and output to the storage unit 56. Even when the signal is determined to be a defect signal, for example, when the signals used for analysis are limited and it is not necessary to acquire all of the scattered light signals 2a-2c and 2x, the acquisition signal discriminating unit outputs signals that do not need to be acquired. It is possible to block, and the amount of unnecessary signal acquisition can be further suppressed. For example, when it is not necessary to acquire the scattered light signal 2x in the example illustrated in FIG. 12, the scattered light signal 2x at the times t1 and t3 is removed as illustrated in FIG. Are further reduced by two.

4). In the above-described embodiment, the case where the acquisition signal discriminators 46a-46c, 46x are provided with the aim of further suppressing the acquisition amount of unnecessary signals has been described as an example. However, the degree of freedom in setting determination conditions is improved. The acquisition signal discriminating units 46a to 46c and 46x are not always necessary to obtain the essential effect, and can be omitted if unnecessary. In addition, the comparison necessity discrimination units 43a-43c and 43x can discriminate whether or not it is necessary to execute comparison with the threshold values for the scattered light signals 2a-2c and 2x, but they are not used for defect determination. Since there is no particular problem even if the signal is compared with the threshold value, the comparison necessity discrimination parts 43a-43c, 43x are not always necessary and unnecessary for obtaining the essential effect of improving the degree of freedom in setting the determination condition. If so, it can be omitted.

  In addition, the scattered light signal 2x, which is obtained by calculating the individual scattered light signals 2a-2c and combining them into one, is included in the defect determination signal. However, if the scattered light signal 2x is not required, the arithmetic processing is performed. The part 41, the comparison necessity discrimination part 43x, the threshold value comparison part 44x, and the acquired signal discrimination part 46x can be omitted.

1a-c scattered light 2a-c, x scattered light signal 11 sample table 12 sample table moving mechanism 20 inspection light irradiation device 21 inspection light (laser light)
30a-c Scattered light detector 41 Arithmetic processing section 42 Signal filter section 43a-c, x Comparison necessity discrimination section 44a-c, x Threshold comparison section 45 Defect determination section 46a-c, x Acquisition signal discrimination section 52 Operation Part (condition setting part)
56 Storage Unit 100 Wafer (Sample)
α, β, γ, σ threshold

Claims (12)

A sample stage on which the sample is placed;
A sample stage moving mechanism for moving the sample stage;
An inspection light irradiation device for obliquely irradiating inspection light onto the sample on the moving sample stage;
A plurality of scattered light detectors for detecting scattered light from the sample;
The scattered light signals generated by the plurality of scattered light detectors for the scattered light generated simultaneously from the same coordinates on the sample are logically operated to determine whether or not the scattered light signal is a defect signal scattered by a defect. A defect determination unit that outputs only the scattered light signal determined as:
A storage unit for storing the scattered light signal output from the defect determination unit;
A defect inspection apparatus comprising: a condition setting unit that sets a logical operation expression used as a defect determination condition in the defect determination unit by combining one or a plurality selected from a plurality of logical operations. A sample stage on which the sample is placed;
A sample stage moving mechanism for moving the sample stage;
An inspection light irradiation device for obliquely irradiating inspection light onto the sample on the moving sample stage;
A plurality of scattered light detectors for detecting scattered light from the sample;
A plurality of threshold comparison units for comparing individual scattered light signals of the plurality of scattered light detectors with corresponding threshold values for defect determination, respectively, for determining a magnitude relationship with respect to the threshold values;
A defect in which the scattered light signal is scattered by a defect by performing a logical operation on the comparison result of the threshold value comparison unit of the scattered light signal by the plurality of scattered light detectors with respect to the scattered light generated simultaneously from the same coordinates on the sample. A defect determination unit that determines whether the signal is a signal and outputs only a scattered light signal determined to be a defect signal;
A storage unit for storing the scattered light signal output from the defect determination unit;
A condition for setting a logical operation expression used as a defect determination condition in the defect determination unit by combining the comparison results of the threshold value comparison unit by one or a plurality of logical operations selected from a plurality of logical operations prepared as options A defect inspection apparatus comprising a setting unit. A sample stage on which the sample is placed;
A sample stage moving mechanism for moving the sample stage;
An inspection light irradiation device for obliquely irradiating inspection light onto the sample on the moving sample stage;
A plurality of scattered light detectors for detecting scattered light from the sample;
It is determined whether or not the scattered light signals by the plurality of scattered light detectors for the scattered light generated simultaneously from the same coordinates on the sample are defect signals scattered by the defect, and only the scattered light signal determined as the defect signal is used. A defect determination unit to output;
A storage unit for storing the scattered light signal output from the defect determination unit;
A defect that uses a logical operation expression that simultaneously satisfies that at least one scattered light signal exceeds a corresponding threshold value and that at least one other scattered light signal is equal to or less than a corresponding threshold value in the defect determination unit. A defect inspection apparatus comprising a defect determination unit that is set as the determination condition. The defect inspection apparatus according to claim 1,
A defect inspection apparatus comprising: an acquisition signal discriminating unit that discriminates only a scattered light signal designated from scattered light signals determined to be a defect signal by the defect determination unit and outputs the discriminated signal to the storage unit. The defect inspection apparatus according to claim 2,
A defect inspection apparatus comprising a comparison necessity discrimination unit for discriminating whether or not to perform comparison between scattered light signals of the plurality of threshold comparison units and thresholds. The defect inspection apparatus according to claim 1,
The scattered light signal that is used for defect determination and can be stored in the storage unit includes a scattered light signal that is obtained by performing mathematical operation on the individual scattered light signals of the plurality of scattered light detectors. Defect inspection equipment.   Using a logical operation formula constructed by combining one or more selected from a plurality of logical operations as a defect judgment condition, scattered light signals from multiple scattered light detectors for scattered light generated simultaneously from the same coordinate on the sample A defect information acquisition apparatus characterized by performing a logical operation to determine whether or not the scattered light signal is a defect signal scattered by a defect and outputting only the scattered light signal determined to be a defect signal to a storage unit. A plurality of threshold comparison units for comparing individual scattered light signals of the plurality of scattered light detectors with corresponding thresholds for defect determination and determining a magnitude relationship with respect to the threshold values,
Using the logical operation formula constructed by combining the comparison results of the threshold comparison unit by one or a plurality of logical operations selected from a plurality of logical operations prepared as options as the defect judgment conditions, the same coordinates on the sample A logical operation is performed on the comparison result of the threshold value comparison unit of the scattered light signal by the plurality of scattered light detectors with respect to the scattered light generated simultaneously, and it is determined whether or not the scattered light signal is a defect signal scattered by a defect. And a defect determination unit that outputs only the scattered light signal determined to be a defect signal to the storage unit.   Using a logical arithmetic expression that simultaneously satisfies that at least one scattered light signal exceeds a corresponding threshold value and that at least one other scattered light signal is equal to or lower than the corresponding threshold value as a defect determination condition, It is determined whether or not the scattered light signal from the plurality of scattered light detectors for the scattered light generated simultaneously from the same coordinates above is a defect signal scattered by the defect, and only the scattered light signal determined to be a defect signal is stored in the storage unit. A defect information acquisition apparatus characterized by outputting the defect information. A logical operation formula constructed by combining one or more selected from a plurality of logical operations is set as a defect judgment condition,
The sample on the moving sample stage is obliquely irradiated with inspection light, and the scattered light from the sample is detected by multiple scattered light detectors.
A logical operation of the scattered light signals by the plurality of scattered light detectors for scattered light generated simultaneously from the same coordinates on the sample to determine whether the scattered light signal is a defect signal scattered by a defect;
Only a scattered light signal determined as a defect signal is stored in a storage unit. A logical operation expression constructed by combining the comparison result of the scattered light signal and the corresponding threshold value by one or a plurality of logical operations selected from a plurality of logical operations prepared as options is set as a defect judgment condition,
The sample on the moving sample stage is obliquely irradiated with inspection light, and the scattered light from the sample is detected by multiple scattered light detectors.
Each scattered light signal of the plurality of scattered light detectors is compared with a corresponding defect determination threshold value to determine a magnitude relationship with respect to each threshold value,
Whether the scattered light signal is a defect signal scattered by a defect by performing a logical operation on a comparison result of the scattered light signal generated by the plurality of scattered light detectors with respect to the scattered light generated simultaneously from the same coordinates on the sample. Determine whether or not
Only a scattered light signal determined as a defect signal is stored in a storage unit. A defect that uses a logical operation expression that simultaneously satisfies that at least one scattered light signal exceeds a corresponding threshold value and that at least one other scattered light signal is equal to or less than a corresponding threshold value in the defect determination unit. Set as the judgment condition of
The sample on the moving sample stage is obliquely irradiated with inspection light, and the scattered light from the sample is detected by multiple scattered light detectors.
Determining whether or not the scattered light signal by the plurality of scattered light detectors for the scattered light generated simultaneously from the same coordinates on the sample is a defect signal scattered by a defect,
Only a scattered light signal determined as a defect signal is stored in a storage unit.

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