JP3732560B2 - Inspection performance evaluation method for pattern inspection apparatus and apparatus therefor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention provides a high-accuracy dimension of a pattern to be inspected consisting of a fine circuit pattern or wiring pattern formed on an object to be inspected such as a semiconductor substrate such as a semiconductor wafer, a TFT liquid crystal substrate, a thin film multilayer substrate, or a printed circuit board. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pattern inspection apparatus on an inspection object to be measured and detected, an inspection performance evaluation method of a defect inspection apparatus for a pattern on an inspection object that performs fine defect inspection on a pattern on the inspection object, and an apparatus therefor Is.
[0002]
[Prior art]
Recently, for example, a pattern to be inspected consisting of a circuit pattern or a wiring pattern formed on a semiconductor wafer, a TFT liquid crystal substrate, a thin film multilayer substrate, a printed circuit board, etc. has been miniaturized in response to the need for high integration. Yes. By the way, since circuit patterns or wiring patterns are increasingly miniaturized as the degree of integration increases, the defects that must be detected become increasingly minute. Detection of such fine defects has become a very important issue in determining the quality of these circuit patterns or wiring patterns when manufacturing circuit patterns or wiring patterns.
[0003]
However, since the miniaturization has further progressed and minute defect detection has reached the resolution limit of the imaging optical system in the inspected pattern such as a circuit pattern or a wiring pattern, an improvement in essential resolution is required. Yes.
[0004]
As a conventional technique for improving the essential resolution in this way, a technique described in Japanese Patent Laid-Open No. 5-160002 is known. In this prior art, an illuminating means for irradiating a minute circuit pattern formed on a mask with a ring-shaped diffused illumination configured by arranging a large number of virtual point light sources by a light source spatial filter, and the illumination The diffracted light from the fine pattern that is transmitted or reflected through the mask that is diffusely illuminated almost uniformly by the means is sufficiently captured, and at least a part of the 0th-order diffracted light or the low-order diffracted light is shielded from the captured light. A light receiving means for receiving a circuit pattern formed by passing through the optical pupil and obtaining an image signal, and an image signal obtained from the light receiving means and a mask. There is described a pattern inspection apparatus provided with comparison means for inspecting a pattern in comparison with pattern data, wafer pattern data, or data from a transfer simulator.
[0005]
This prior art also describes controlling the shapes of the light source spatial filter and the imaging spatial filter in accordance with the pattern shape data.
[0006]
[Problems to be solved by the invention]
However, in the above prior art, an annular diffuse illumination is applied to the fine pattern on the object to be inspected, and the diffracted light from the fine pattern is sufficiently taken into the aperture (pupil) of the objective lens. In order to detect fine pattern defects by obtaining high-resolution image signals, the state of the inspection device itself is monitored, and there is no function to maintain the device performance in a constant state, so it is highly reliable and fine. There was a problem that the point of detecting defects was not sufficiently considered.
[0007]
That is, in the conventional apparatus, when the optical system is affected by heat or the like and the focal position, the resolution, and the like change, there is no means for detecting and correcting this. Further, for alignment, there is no means for correcting drift and the like, and the illuminance distribution needs to be measured using a dummy flat wafer.
[0008]
In addition, as for the running performance of the stage, there was no way to evaluate its performance, so it was replaced when a certain period of time arrived, or it was replaced when it was found that the performance was significantly reduced and the cause was the stage. .
[0009]
The object of the present invention is to solve the above-mentioned problems of the prior art, and to highly reliable various fine patterns existing on an object to be inspected on a semiconductor substrate such as a semiconductor wafer, a TFT liquid crystal substrate, a thin film multilayer substrate, and a printed substrate. An object of the present invention is to provide an inspection performance evaluation method for a pattern inspection apparatus on an object to be inspected that can be detected, and an apparatus therefor.
[0010]
[Means for Solving the Problems]
In order to solve the above problems, the present invention mainly adopts the following configuration.
A method for evaluating the characteristics of an inspection apparatus for determining the quality of a circuit pattern or a wiring pattern of an inspection object,
A pattern for evaluating optical system characteristics, a pattern for evaluating alignment characteristics, and a pattern for evaluating illuminance distribution characteristics provided on the stage on which the inspection object is placed are not overlapped with the inspection object. Detect with detection means ,
By processing the images of the respective patterns obtained by the detection , information on the optical system characteristics, alignment characteristics, and illuminance distribution characteristics of the inspection apparatus is obtained,
A characteristic evaluation method for an inspection apparatus, characterized by evaluating each characteristic of the inspection apparatus from these pieces of information.
[0011]
According to the present invention, since basic conditions of various important inspection items in the pattern inspection apparatus can be detected and corrected, it becomes possible to always manage the inspection apparatus in an optimum specified state, and to improve reliability. High inspection is possible.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of a pattern inspection apparatus according to the present invention will be described with reference to the drawings.
[0013]
FIG. 1 is a block diagram showing an embodiment of a pattern inspection apparatus according to the present invention. That is, 1 is an objective lens, and 2 is a semiconductor wafer which is an example of a pattern to be inspected. Reference numeral 3 denotes an illumination light source for illuminating the semiconductor wafer 2 which is an example of a pattern to be inspected. Reference numeral 4 denotes an X, Y, Z, θ (rotation) stage on which a semiconductor wafer 2 which is an example of a pattern to be inspected is mounted.
[0014]
5 is an inspection performance evaluation having a pattern capable of evaluating the focal position, magnification, resolution, illuminance distribution, alignment and running performance of the stage 4 of the optical system, and having a detection element for detecting the amount of light from the pattern. As shown in FIG. 2, the detector is set at the position where it does not overlap the semiconductor wafer 2 within the stage movable range on the stage 4 so as to be the same height as the semiconductor wafer 2. The detector 5 includes a detection light quantity and autofocus inspection area 5a, a resolution inspection area 5b, an alignment inspection area 5c, an illumination light quantity inspection area 5d, and a stage inspection area shown in FIG. 5e and a defect detection evaluation region 5f. The pattern is obtained, for example, by etching a Si substrate as shown in FIG. 4 or by forming a glass substrate as shown in FIG. 5 and etching it.
[0015]
Reference numeral 6 denotes a half mirror, which is configured to reflect light from the illumination light source 3 and perform, for example, bright field illumination on the semiconductor wafer 2 through the objective lens 1. A second objective lens 7 forms an image at a desired position at the magnification of the objective lens. 8 and 9 are half mirrors for reflecting a part of the reflected light from the semiconductor wafer 2, and 10 is a zoom lens.
[0016]
11 is an alignment sensor, 12 is an autofocus sensor, and 13 is a bright field detection image sensor. Reference numeral 14 denotes a control unit for the stage 4, and 15 denotes a control unit for the illumination light source 3. Reference numeral 16 denotes an alignment control unit, 17 denotes an autofocus control unit, and 18 denotes a zoom lens control unit. Reference numeral 19 denotes a bright field detection control unit, and 20 denotes an apparatus main body. Reference numeral 21 denotes a transmittance variable unit which can change the brightness at an arbitrary position, for example, like a liquid crystal, and 22 is a control unit thereof.
[0017]
Next, the operation will be described. The stage 4 is moved so that the detection light quantity of the detector 5 and the area 5a for autofocus inspection come to the detection area of the objective lens 1. Next, the stage 4 is moved in a predetermined step in the Z direction, and brightness information is detected by the autofocus sensor 12.
[0018]
Then, the stage 4 is scanned at each step to move the detector 5 at a constant speed, or the stage 4 is fixed and the brightness information (grayscale image signal) of 5a on the detector 5 is obtained by the image sensor 13. To detect. Information is sent to the bright field detection control unit 19 with the Z position having the highest value of the obtained image signal as the best focus position. For calculation of the best focus position, for example, as shown in FIG. 6, the brightness at each position is plotted in a hill-climbing equation, for example, a quadratic curve is approximated, and the vertex position is set as the best focus position.
[0019]
Further, the best focus position is obtained by the autofocus control unit 17 from the image signal obtained by the autofocus sensor 12, and this information is sent to the bright field detection control unit 19. The difference between the two pieces of information is a device offset, which is sent to the main body 20 and registered as a new device offset. With respect to the image signal obtained at the best focus position and the calculated Z position, the light amount distribution in the image sensor 13 is registered in the main body 20 as a new light level distribution.
[0020]
The stage 4 is moved so that the resolution inspection region 5b of the detector 5 comes to the Z position which is the best focus position by the above method. The resolution inspection 5b has at least one pattern as shown in FIG. FIG. 8 shows another pattern example of the embodiment of FIG. 7, which is an L-shaped pattern in which horizontal and vertical patterns are integrated. Then, while scanning the stage 4 and moving the detector 5 at a constant speed, the image sensor 13 detects the brightness information (grayscale image signal) of the pattern in the resolution inspection area 5b on the detector 5.
[0021]
The resolution is evaluated based on the detection signal (FIG. 9), it is determined whether or not the resolution is lowered, which hinders the inspection of the apparatus 20, and if it causes trouble, an abnormal signal is issued to prompt maintenance. Further, the bright field detection control unit 19 obtains the pattern pitch p from the detected image of FIG. 9, calculates the magnification from this, obtains the magnification variation of the zoom lens 10, and sends the magnification variation amount information to the zoom lens control unit 18, to correct.
[0022]
Next, the stage 4 is moved so that the alignment inspection area 5 c on the detector 5 is located, and the alignment pattern on the alignment inspection area 5 c is detected by the alignment sensor 11. An example of the alignment pattern is a cross mark shown in FIG. The alignment control unit 16 calculates the alignment position and compares it with the alignment position coordinates of the stage 4, and the stage control unit 14 corrects the positional deviation amount.
[0023]
Next, the stage 4 is moved to the light quantity measurement region 5d on the detector 5, and as shown in FIG. 11, the detection element 23 built in the detector 5 is moved from the light shielding portion 24 and the transmission portion 25 as shown in FIG. The amount of light is measured using the following pattern. By performing this while sequentially moving the stage 4, an illumination illuminance distribution as shown in FIG. 13 is measured.
[0024]
When the illumination illuminance distribution is different from the initial state of the apparatus, the illumination light source control unit 15 adjusts the lamp house position. Further, this information is sent to the bright field detection control unit 19 and compared with the illuminance distribution on the image sensor 13 to determine whether the illuminance distribution fluctuation is caused by the illumination or the detection optical system. When there is a cause of fluctuation in illuminance distribution in the illumination system, the lamp house control unit 15 optimizes the lamp house state, or the transmittance variable control unit 22 changes the transmittance of the transmittance variable unit 21 so that the illumination distribution is uniform. Control to be Further, when the illuminance distribution is not in specification, this information is transferred to the main body 20 and an abnormal signal is issued to prompt maintenance.
[0025]
As the light quantity measurement pattern, the illuminance distribution of the entire region can be measured by moving in one direction if the pattern is as shown in FIG. Furthermore, if the pattern is as shown in FIG. 15, the illuminance distribution over the entire region can be measured without moving the stage 4. At this time, as a distribution measuring method, as shown in FIG. 16, a number of sensors are arranged so that light passing through each pinhole does not interfere with each other, and detection of a one-dimensional or two-dimensional image sensor as shown in FIG. There is a method obtained by dividing a region and adding signals within the region.
[0026]
Next, the stage 4 is moved so that the stage inspection area 5e on the detector 5 comes. Then, while scanning the stage 4 and moving the detector 5 at a constant speed, the image sensor 13 detects the brightness information (grayscale image signal) of the pattern in the stage inspection area 5e on the detector 5. Based on this detection signal, the stage running performance is evaluated, and it is judged whether or not the stage running performance is degraded by the apparatus 20, and if so, an abnormal signal is issued to prompt maintenance.
[0027]
A line and space as shown in FIG. 18 is used as the pattern of the stage inspection area 5e. This horizontal line-and-space pattern is used for stage pitching evaluation. The vertical line and space pattern is used for evaluation of constant speed.
[0028]
FIG. 19 shows another embodiment of the pattern shown in FIG. 18, and the evaluation of pitching and constant speed can be performed at once by using a staggered pattern.
[0029]
Next, the stage 4 is moved so that the defect detection evaluation area 5f on the detector 5 comes. Then, while scanning the stage 4 and moving the detector 5 at a constant speed, the image sensor 13 detects brightness information (grayscale image signal) of the pattern in the stage inspection area 5f on the detector 5. Then, the defect detection performance is evaluated based on the detection signal of the defective portion and the detection signal of the non-defective portion, and it is determined whether the apparatus 20 has a defect detection performance degradation that interferes with the inspection. If so, an abnormal signal is issued to encourage maintenance.
[0030]
FIG. 20 shows an embodiment of an evaluation pattern, in which at least two types of bulge and bulge patterns having at least different sizes are formed in at least two types of line and space having different intervals.
[0031]
FIG. 21 is an embodiment in which a defect is provided on a pattern oriented perpendicular to the pattern in FIG. 20, and FIG. 22 is an embodiment in which both FIG. 20 and FIG. FIG. 23 shows an embodiment of an isolated defect, which is effective when performing not only bright field detection but also dark field detection.
[0032]
【The invention's effect】
According to the present invention, since the basic conditions of various inspection items of the inspection apparatus itself can be detected and corrected, it is possible to always manage in an optimum specified state, and to perform a highly reliable inspection. It can be carried out.
[Brief description of the drawings]
FIG. 1 is a configuration diagram showing an embodiment of an inspection pattern inspection apparatus according to the present invention.
FIG. 2 is a layout diagram of detectors on a stage.
FIG. 3 is a diagram showing a pattern on a detector.
FIG. 4 is an embodiment of a pattern shape cross section.
FIG. 5 shows an embodiment of a pattern shape cross section.
FIG. 6 shows a relationship between z and brightness information.
FIG. 7 is an embodiment of a resolution evaluation pattern.
FIG. 8 is an embodiment of a resolution evaluation pattern.
FIG. 9 is a diagram illustrating a detection signal.
FIG. 10 is an embodiment of an alignment evaluation pattern.
FIG. 11 is a diagram showing a state in which a detector is built in a stage.
FIG. 12 shows an embodiment of a pattern for evaluating the amount of illumination light.
FIG. 13 is a diagram showing an illumination illuminance distribution.
FIG. 14 is an embodiment of a pattern for illumination light quantity evaluation.
FIG. 15 is an embodiment of a pattern for illumination light quantity evaluation.
FIG. 16 is an embodiment of a sensor for measuring the amount of illumination light.
FIG. 17 is an embodiment of a sensor for measuring the amount of illumination light.
FIG. 18 shows an embodiment of a stage evaluation pattern.
FIG. 19 is an embodiment of a pattern for stage evaluation.
FIG. 20 shows an embodiment of a pattern for evaluating defect detection performance.
FIG. 21 shows an embodiment of a pattern for evaluating defect detection performance.
FIG. 22 shows an embodiment of a pattern for evaluating defect detection performance.
FIG. 23 is an embodiment of a pattern for evaluating defect detection performance.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Objective lens 2 Semiconductor wafer 3 Illumination light source 4 X, Y, Z, (theta) stage 5 Inspection performance evaluation detector 6 Half mirror 7 Second objective lens 8 Half mirror 9 Half mirror 10 Zoom lens 11 Alignment sensor 12 Autofocus sensor DESCRIPTION OF SYMBOLS 13 Image sensor 14 for bright field detection Stage control part 15 Illumination light source control part 16 Alignment control part 17 Auto focus control part 18 Zoom lens control part 19 Bright field detection control part 20 Device main body 21 Transmittance variable part 22 Transmittance variable part control Part 23 detecting element 24 light shielding part 25 transmitting part 26 covering pattern 27 bulging pattern 28 isolated defect

Claims (8)

A method for evaluating the characteristics of an inspection apparatus for determining the quality of a circuit pattern or a wiring pattern of an inspection object,
Pattern for evaluating the optical system characteristics provided in the not overlapping the inspection object position on the stage for mounting the inspection object, a pattern for evaluating the alignment characteristic, the inspection device patterns to evaluate the irradiation distribution characteristics The detection means
Optics properties of the test devices by processing an image of the respective patterns obtained by said detection, alignment characteristic, obtain information irradiation distribution characteristic,
A characteristic evaluation method for an inspection apparatus, characterized by evaluating each characteristic of the inspection apparatus from these pieces of information. A method for evaluating the characteristics of an inspection apparatus for determining the quality of a circuit pattern or a wiring pattern of an inspection object,
Pattern for evaluating the optical system characteristics provided in the not overlapping the inspection object position on the stage for mounting the inspection object, a pattern for evaluating the alignment characteristic, a pattern for evaluating the illuminance distribution characteristics, stages running characteristics Detecting the pattern for evaluating the detection means of the inspection apparatus,
Optics properties of the test devices by processing an image of the respective patterns obtained by said detection, alignment characteristic, resulting illuminance distribution characteristics, the information of the stages running characteristics,
A characteristic evaluation method for an inspection apparatus, characterized by evaluating each characteristic of the inspection apparatus from these pieces of information. In claim 1,
The pattern for evaluating the optical system characteristics, patterns of measuring detected light, pattern for measuring the autofocus, characterization method of inspecting and wherein the Ru pattern der to measure the resolution. In claim 2,
The pattern for evaluating the optical system characteristics is a pattern for measuring the detected light amount, a pattern for measuring autofocus, and a pattern for measuring resolution.
In addition to the optical system characteristic evaluation pattern, the evaluation pattern detected by the detection means has a pattern for evaluating stage travel performance for evaluating the travel performance of the stage . An inspection apparatus for determining the quality of a circuit pattern or a wiring pattern of an inspection object,
Stage means for placing and moving the object to be inspected;
Patterns to evaluate the installed optical properties in a region which does not overlap with a region for mounting the inspection object on the stage unit, a pattern for evaluating the alignment characteristics, the testing device having a pattern for evaluating the irradiation distribution characteristics Characteristic evaluation pattern part,
Detecting means for detecting an image of each pattern of the characteristic evaluation pattern portion;
Image processing means for obtaining information on optical system characteristics, alignment characteristics, and illuminance distribution characteristics of the inspection apparatus from an image of the pattern detected by the detection means;
An inspection apparatus having a characteristic evaluation function, comprising: characteristic evaluation means for evaluating each characteristic of the inspection apparatus from information obtained by the image processing means. An inspection apparatus for determining the quality of a circuit pattern or a wiring pattern of an inspection object,
Stage means for placing and moving the object to be inspected;
Patterns to evaluate the installed optical properties in a region which does not overlap with a region for mounting the inspection object on the stage unit, a pattern for evaluating the alignment characteristic, a pattern for evaluating the illuminance distribution characteristics, the stages running characteristics A characteristic evaluation pattern portion of an inspection apparatus having a pattern to be evaluated;
Detecting means for detecting an image of each pattern of the characteristic evaluation pattern portion;
Image processing means for obtaining optical system characteristics, alignment characteristics, illuminance distribution characteristics, and stage running characteristics information of the inspection apparatus from the pattern image detected by the detection means;
An inspection apparatus having a characteristic evaluation function, comprising: characteristic evaluation means for evaluating each characteristic of the inspection apparatus from information obtained by the image processing means. In claim 5,
The pattern for evaluating the optical system characteristics, patterns of measuring detected light, pattern for measuring the autofocus, the inspection apparatus having the characterization function, wherein the Ru pattern der to measure the resolution. In claim 6,
The pattern for evaluating the optical system characteristics is a pattern for measuring the detected light amount, a pattern for measuring autofocus, and a pattern for measuring resolution.
In addition to the optical system characteristic evaluation pattern, the inspection apparatus having a characteristic evaluation function has a pattern for evaluating the stage running performance for evaluating the running performance of the stage as the evaluation pattern detected by the detecting means .

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