JP4001681B2 - Foreign matter diameter determination method and foreign matter inspection device in foreign matter inspection device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention provides, for example, a reticle / mask used to print a pattern on a wafer in an LSI manufacturing process, a product wafer on which a pattern is formed, or a surface of an inspection target substrate such as a liquid crystal substrate. The present invention relates to a foreign matter inspection apparatus capable of specifying whether or not, and its size and place of attachment, and a foreign matter diameter determination method in the foreign matter inspection device.
[0002]
[Prior art]
First, FIG. 2 schematically shows an example of an optical system of, for example, a light scattering type foreign matter inspection apparatus. In this figure, 1 is a reticle as a substrate to be inspected (sample), and an arrow is placed on the base plate 2. It is placed on the upper surface of the inspection stage 3 that can reciprocate linearly in the X direction. Reference numeral 4 denotes a pellicle frame.
[0003]
Reference numeral 5 denotes an incident optical system that irradiates the surface of the sample 1 with the laser beam L in the direction of the arrow Y perpendicular to the moving direction X of the inspection stage 3 and emits the laser beam L having a certain deflection angle. For example, a He-Ne laser oscillator 6, a beam expander 7, a galvano mirror 8 that scans the laser light L, a scanning lens 9, and the like, and the laser light L is emitted obliquely from above the surface of the sample 1 by a predetermined angle. Scanning irradiation is performed in the arrow Y direction.
[0004]
Reference numerals 10A and 10B denote left and right detection optical systems that individually detect scattered light R based on the irradiation of the laser light L on the left half and the right half of the surface of the sample 1, and laser light irradiation in the middle of the scanning direction of the incident optical system 5 Arranged on the left and right sides with respect to the reference center C, respectively, a condensing lens 11, a slit member 12 in which a slit (not shown) for limiting incident light with respect to the scattered light R is formed, and, for example, a photomultiplier tube And the like.
[0005]
In the foreign matter inspection apparatus, the surface of the sample 1 is irradiated with the laser beam L while the inspection stage 3 is moved in the arrow X direction and the laser beam L is reciprocated in the arrow Y direction. When the foreign matter is present in the irradiated portion of the laser beam L, the laser light L is scattered at random in all directions by the foreign matter, and when the foreign matter is present on the left half of the surface of the sample 1, the irradiation direction of the laser light L A part of the scattered light R reflected backward is detected by the left detection optical system 10A, and when a foreign substance is present on the right half of the surface of the sample 1, the scattered light R is detected by the right detection optical system 10B. Thus, the presence of foreign matter on the surface of the sample 1 is detected.
[0006]
[Problems to be solved by the invention]
By the way, in the light scattering type foreign matter inspection apparatus as shown in FIG. 2, the resolution (range represented by one signal) of the foreign matter signal on the sample 1 is generally as shown in FIG. This is determined by the signal capturing interval Ty or position resolution in the Y direction of the laser beam L to be scanned and the scanning interval Sx in the X direction of the laser beam L.
[0007]
Then, when counting a signal (caused by scattered light) obtained from a unit range (indicated by reference numeral 21 in FIG. 4) determined by the signal capturing interval Ty and the laser beam scanning interval Sx, one foreign object 22 is counted. The number of signals obtained from is generally plural. In order to obtain the size of the foreign matter 22 from a plurality of signals obtained from such a single foreign matter 22, the following is performed.
[0008]
That is, first, based on the distances between the individual signal generation points, signals within a certain range of each other are considered to be signals from the same foreign substance 22, and these are grouped. Next, among those groups, the one having the highest signal intensity is set as the representative value of the scattered light of the group. Then, this representative value is substituted into a calibration curve for obtaining the foreign substance diameter based on the intensity of the signal output from the photodetector 13 (hereinafter simply referred to as a calibration curve based on the signal intensity), and the size of the foreign substance 22 in the group. (Foreign material diameter) can be obtained. On the other hand, the number of signals in said group, a calibration curve for determining the foreign substance diameter based on the number of signals output from the photodetector 13 (hereinafter, referred to as a calibration curve by the number of signals) by substituting the, of the group of the foreign matter 22 The size (foreign material diameter) can also be obtained.
[0009]
It is assumed that the calibration curve based on the signal intensity is as shown in FIG. In this figure, A is a calibration curve based on signal intensity, and the horizontal axis represents the dynamic range of signal intensity in the signal processing circuit, and is in the range of 0-100. The vertical axis represents the foreign substance diameter, and D _p1 and D _p2 are the minimum diameter and the maximum diameter, respectively.
[0010]
By the way, as the semiconductor circuit becomes higher in LSI, the finer and higher density of the pattern is required, and the foreign matter to be detected by the foreign matter inspection apparatus is becoming smaller. To cope with this, the foreign matter detection sensitivity As the sensitivity increases, the dynamic range of the system that processes signals based on scattered light moves to the weak signal side, that is, the small diameter side of the foreign matter, and the calibration curve A shown in FIG. When the signal intensity exceeds 100, the signal processing system is saturated, and the diameter larger than D _p2 is indefinite . For this reason, the size of a larger foreign object cannot be determined.
[0011]
However, in reality, there is a high possibility that there is a large foreign object that exceeds the detection limit (D _p2 in FIG. 5 above), and generally, the presence of a larger foreign object becomes a problem.
[0012]
The present invention has been made in consideration of the above-mentioned matters, and the object thereof is a foreign matter in a foreign matter inspection apparatus capable of accurately determining the foreign matter diameter in a wide foreign matter diameter range regardless of the dynamic range of the signal processing system. It is to provide a diameter determining method (hereinafter simply referred to as a foreign substance diameter determining method) and a foreign substance inspection apparatus .
[0013]
[Means for Solving the Problems]
In order to achieve the above object, the foreign matter diameter determining method according to the present invention irradiates the surface of the substrate to be inspected while scanning the laser beam, and injects the scattered light from the foreign matter from the surface of the substrate to be inspected at that time. by, a photodetector for detecting foreign matter on the surface of the inspection target board, the foreign substance diameter determination method in the signal processing system and in which the particle inspection apparatus comprising a to process captures a signal output from the optical detector A calibration curve for obtaining a foreign substance diameter based on the signal intensity output from the photodetector, and a signal output from the photodetector and having a generation point within a predetermined range as a signal from one foreign substance. as is, the is a calibration curve for determining the foreign substance diameter based on the number of signals in a predetermined range, within the dynamic range regarding the signal strength of the signal processing system Information, wherein the larger of the foreign substance diameter respectively obtained by both calibration curves determined in foreign substance diameter, also, to the extent that exceeds the dynamic range comprises a dynamic range spread than the dynamic range larger diameter The diameter obtained by the calibration curve for obtaining the foreign substance diameter based on the number of signals obtained by the signal processing system is determined as the foreign substance diameter.
Further, the foreign matter inspection apparatus according to the present invention irradiates the surface of the inspection target substrate while scanning with laser light, and causes the scattered light caused by the foreign matter from the surface of the inspection target substrate to enter the inspection target substrate. In a foreign substance inspection apparatus comprising a photodetector for detecting foreign substances on the surface of a substrate and a signal processing system for taking in and processing signals output from the photodetectors, in order to determine the foreign substance diameter based on the signal intensity When the scattered light signal obtained from the calibration curve, the signal capture interval in the scanning direction of the laser beam and the unit range determined by the scanning interval in the moving direction of the inspection target substrate of the laser beam is 1, it is obtained from one foreign matter. And a calibration curve for determining the foreign substance diameter based on the number of scattered light signals, and within the dynamic range of the signal processing system related to signal intensity. In this case, the larger of the foreign substance diameters obtained by the both calibration curves is determined as the foreign substance diameter, and in the range exceeding the dynamic range, a dynamic range that extends to the larger diameter side than the dynamic range is provided. And a means for determining the diameter obtained by the calibration curve for obtaining the foreign substance diameter based on the number of signals from the signal processing system as the foreign substance diameter.
[0014]
According to the foreign substance diameter determination method and particle inspection apparatus, well within the range of the dynamic range of the signal processing system related to the signal strength, can also be accurately determined for foreign substance diameter in the range of greater than this, the foreign substance diameter, its It can be accurately determined over a wide range of foreign matter diameters from very small to quite large.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows an example of a calibration curve used in the foreign substance diameter determination method and apparatus of the present invention. A calibration curve A based on signal intensity and a calibration curve B based on the number of signals are placed on the same axis based on the foreign substance diameter. Represents. These two calibration curves A and B have the following relationship. That is, the calibration curve A based on the signal intensity is set so that the evaluation diameters of the calibration curve B based on the number of scattered light signals from the same foreign substance substantially coincide with each other at the foreign substance diameter _Dp2 corresponding to the level at which the signal is saturated in the signal processing circuit. Is done. In other words, the calibration curve A, B, the code I calibration curve in the saturation level indicated by _M A and the calibration curve B has a relationship as to substantially coincide in FIG.
[0016]
The dynamic range of the calibration curve B based on the number of signals is greatly expanded toward the large diameter side compared to the dynamic range of the calibration curve A based on the signal intensity. That is, the dynamic range of the calibration curve B based on the number of signals is from the number of signals 0 to the number of signals limited by the storage capacity assigned by the arithmetic processing unit (not shown) for calculating the foreign substance diameter, It can be said that the degree of freedom is higher than the dynamic range of the circuit (which is often determined by a signal amplifier or an AD converter circuit), and there is no practical limit.
[0017]
And in this invention, when determining the magnitude | size of a foreign material, it is as follows. That is, in the range where the calibration curve A based on the signal intensity is effective, that is , within the dynamic range where the calibration curve A based on the signal intensity is not saturated, the foreign substance diameters Da, obtained by the two calibration curves A and B, respectively. Db is compared, and the larger one is always the representative diameter of the foreign material. In this way, the foreign matter diameter is always determined to be larger than the actual size, and is always evaluated on the safe side. In the example shown in FIG. 1, the foreign substance diameter Db obtained by the calibration curve B based on the number of signals is always adopted as the representative diameter.
[0018]
Further, in the range where the calibration curve A based on the signal intensity does not make sense, that is, on the large diameter side exceeding the dynamic range of the signal processing system related to the signal intensity, the calibration curve based on the signal intensity is denoted by the symbol A in FIG. As indicated by ', the calibration curve B based on the number of signals is made constant so that the calibration curve A' based on signal intensity always becomes large. That is, in the range where the calibration curve A based on the signal intensity is saturated, the foreign substance diameter Db obtained by the calibration curve B based on the number of signals is always adopted as the representative diameter.
[0019]
In the two calibration curves A and B in FIG. 1, the foreign substance diameter Db obtained by the calibration curve B based on the number of signals is obtained by the calibration curve A based on the signal strength in a range where the calibration curve A based on the signal strength is effective. Although it is made larger than the foreign substance diameter Da, it is needless to say that there are various relationships between these two calibration curves A and B as shown in FIGS. 3 (A) and 3 (B).
[0020]
【The invention's effect】
According to the foreign matter diameter determining method and foreign matter inspection device of the present invention, the calibration curve based on the signal intensity is effective, that is, within the range of the dynamic range of the signal processing system , that is, the range beyond this, that is, the large diameter side. Also, the foreign substance diameter can be accurately determined. Therefore, it is possible to accurately determine the diameter of a foreign substance over a wide range of foreign substance diameters as compared to the conventional case, so that foreign substance management can be performed more efficiently and accurately in various processes that require foreign substance management such as LSI manufacturing processes. Can do.
[Brief description of the drawings]
FIG. 1 is a diagram schematically showing an example of a calibration curve used in a foreign matter diameter determination method in a foreign matter inspection apparatus of the present invention.
FIG. 2 is a diagram schematically showing a configuration of an optical system of a foreign matter inspection apparatus to which the present invention is applied.
FIG. 3 is a diagram schematically showing another example of a calibration curve used in the foreign matter diameter determining method in the foreign matter inspection apparatus of the present invention.
FIG. 4 is a diagram for explaining resolution in a two-dimensional direction of a foreign substance signal.
FIG. 5 is a diagram for explaining a conventional technique.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Inspection board | substrate, 13 ... Photodetector, L ... Laser beam, R ... Scattered light, A ... Calibration curve by signal intensity, B ... Calibration curve by the number of signals.

Claims (2)

Photodetector that detects foreign matter on the surface of the inspection target substrate by irradiating the surface of the inspection target substrate while scanning with laser light and making the scattered light from the foreign matter from the surface of the inspection target substrate enter at that time And a foreign substance diameter determination method in a foreign substance inspection apparatus comprising a signal processing system that takes in and processes a signal output from the photodetector,
A calibration curve for obtaining a foreign substance diameter based on the signal intensity output from the photodetector, and a signal output from the photodetector and having a generation point within a predetermined range are signals from one foreign substance. as, on the basis of the number of signals within a predetermined range and a calibration curve for determining the foreign substance diameter, within the scope of the dynamic range is about the signal strength of the signal processing system, respectively, by the two calibration curves obtained The larger foreign substance diameter is determined as the foreign substance diameter, and in the range exceeding the dynamic range , based on the number of signals by the signal processing system having a dynamic range wider than the dynamic range. A foreign matter diameter determining method in a foreign matter inspection apparatus, wherein the diameter obtained by a calibration curve for determining the foreign matter diameter is determined as the foreign matter diameter. Photodetector that detects foreign matter on the surface of the inspection target substrate by irradiating the surface of the inspection target substrate while scanning with laser light and making the scattered light from the foreign matter from the surface of the inspection target substrate enter at that time And a foreign matter inspection apparatus comprising a signal processing system that captures and processes a signal output from the photodetector,
A calibration curve for obtaining a foreign substance diameter based on the signal intensity, a scattered light signal obtained from a unit range determined by a signal capturing interval in the scanning direction of the laser beam and a scanning interval in the moving direction of the inspection target substrate of the laser beam is 1 A calibration curve for determining the diameter of the foreign matter based on the number of scattered light signals obtained from one foreign matter, and within the range of the dynamic range of the signal processing system relating to the signal intensity, The larger of the foreign substance diameters obtained by the calibration curve is determined as the foreign substance diameter, and in the range exceeding the dynamic range, a signal processing system having a dynamic range that extends to the larger diameter side than the dynamic range is used. Means for determining the diameter obtained by a calibration curve for determining the diameter of a foreign substance based on the number of signals as the foreign substance diameter; Particle inspection apparatus characterized by.

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