JPH10300825A - Defect inspection device for circuit pattern of substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform a defect inspection with high precision and high throughput by use of a sample stage less changed in attitude precision, inclination, height or the like with the lapse of time by holding and moving a substrate within vacuum, forming an image by secondary electrons, and automatically inspecting the defect of a circuit pattern by comparison. SOLUTION: When a wafer 14 is placed on a sample stage 5, electron beams are emitted from an electron gun 1 to the wafer 14. The electron beams scan only one dimension, and the sample stage 5 is continuously moved in the direction orthogonal to the scanning direction. In order to obtain the image of the wafer 14, the generated secondary electrons are detected synchronously with the scanning of the electron beam and the movement of the sample stage 5. This signal is transmitted to the image memory 10 of an image processing part 104, and compared with the taken image of the adjacent part one before. The part where a difference is recognized as the comparison result is judged as a defect, and the information such as coordinate is transmitted to a system computer 105.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device, and more particularly to a device for inspecting a substrate, and more particularly to a device for inspecting a circuit pattern on a substrate.

[0002]

2. Description of the Related Art Conventional scanning electron microscopes (SEMs)
This is an apparatus for observing a very limited visual field at high magnification, for example, an area of several tens of μm square over time. In addition, the scanning electron microscope for length measurement, which is one of the semiconductor inspection devices, measures only a predetermined plurality of points on a substrate such as a wafer at a high magnification, so the sample stage adopts a step-and-repeat method, The importance of "static" positioning accuracy, position detection accuracy, and attitude accuracy was emphasized.

[0003]

In the above-mentioned conventional mechanism, the objective is to observe a limited portion of a substrate such as a wafer at a high magnification, so that the sample stage employs a step-and-repeat method. On the other hand, since the present apparatus is an apparatus for searching for a defect on a substrate such as a wafer, it is necessary to inspect a very wide range.
When performing this wide-range inspection by the conventional step-and-repeat method, the sample stage must be moved to the target position and the inspection must be performed in the middle stage until the vibration is settled. Lower. In order to set this middle stage time to 0 and to form an image similar to two-dimensional scanning of the electron beam, the electron beam is one-dimensionally scanned in one direction in this apparatus, and the sample stage is moved in a direction orthogonal to the scanning direction. Is adopted.

However, in this method, if the speed of the continuous movement of the sample stage fluctuates, the formed image becomes erroneous, and if this is compared with the previous image, the correct pattern is recognized as a defect. The problem that occurs. In addition, when the sliding material is significantly worn, there is a problem that the posture accuracy, inclination, height (focus), etc. of the sample stage are changed with time, and the operation rate of the apparatus is reduced due to downtime such as repair.

An object of the present invention is to achieve high accuracy and high throughput by using a sample stage which can be continuously moved at a stable speed in a vacuum and has little change with time such as posture accuracy, inclination and height (focus). An object of the present invention is to provide a defect inspection device for a circuit pattern on a substrate.

[0006]

In order to achieve the above object, the present invention requires that the frictional resistance of the sample stage be reduced. To reduce the load applied to the sliding surface as a result. To reduce the weight of the sample stage, a change in shape, material, and the like can be raised. However, this has the adverse effect of lowering the rigidity, that is, lowering the accuracy of the sample stage, and a great effect cannot be expected. Therefore, the present invention adopts a structure in which a means for applying an external force is employed and a weight reduction mechanism is provided in the sample table.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 is an overall configuration diagram of a defect inspection apparatus for a circuit pattern on a substrate according to the present invention. This apparatus is roughly divided into an electron optical system 101, a sample chamber 102, a control unit 10
3, an image processing unit 104 and a system computer 105. The electron optical system 101 includes an electron gun 1, a condenser lens 2, a scanning deflector 3, and an objective lens 4. The sample chamber 102 includes a sample stage 5, a laser measuring system 6, and a wafer height measuring device 7. The secondary electron detector 8 is below the objective lens 4, and the output signal of the secondary electron detector 8 is converted into digital data by the AD converter 9 and sent to the image processing unit 104. The image processing unit 104 includes an image memory 10, an image memory 11, and an arithmetic unit 12.
It is composed of Operation commands and operation conditions of each part of the inspection apparatus are input and output from the control unit 103. Further, a correction signal is generated from the signals of the laser length measuring system 6 and the wafer height measuring device 7 and the correction signal is sent to the objective lens 4 and the scanning signal generator 13 so that the electron beam 201 is always irradiated to a correct position. . The image processing unit 104 and the control unit 103 are controlled by a higher-order system computer 105.

The acceleration of the electron beam 201 is performed by applying a high negative potential to the electron gun 1. As a result, the electron beam 201 advances toward the wafer 14 with energy corresponding to the potential, is converged by the condenser lens 2, is further narrowed down by the objective lens 4, and irradiates the wafer 14 mounted on the sample stage 5. . The optimum irradiation electron energy for observing the wafer 14 is several hundred eV. However, in this apparatus, since the electron beam current is large, the electron beam 201 cannot be narrowed down due to the space charge effect in which electrons repel each other at an energy as low as several hundred eV due to the large electron beam current. Then, from the electron gun 1 to the wafer 1
Until just before 4, the electron beam 201 is accelerated to a high energy of 10 keV. In order to reduce this energy to an optimum value of several hundred eV immediately before the wafer 14, a high negative voltage can be applied to the wafer 14.

When the wafer 14 is placed on the sample stage 5, an electron beam 201 from the electron gun 1 is irradiated on the wafer 14. The electron beam 201 scans only one dimension, and employs a method of continuously moving the sample stage 5 in a direction perpendicular to the scanning direction. In order to acquire an image of the wafer 14, generated secondary electrons are detected, and these are
In synchronization with the scanning of the sample and the movement of the sample stage 5. This signal is sent to the image memory 10 of the image processing unit 104, and is compared with the image of the adjacent part that has been captured immediately before and has already been captured. The part where a difference is found as a result of the comparison is judged as a defect, and information such as coordinates is transmitted to the system computer 105.
Send to When the comparison is completed, the image memory 11 is updated with the image in the image memory 10, and the same is repeated.

When the inspection of a predetermined range is completed, the wafer 1
4 is sent to the atmosphere.

By the above-described series of operations, a defect of the semiconductor wafer 14 during the process can be inspected at high speed.

FIG. 2 is a front view of the sample stage 5 using the weight reducing mechanism 21, and FIG. 3 is a side view of the sample stage 5 using the weight reducing mechanism 21. The sample stage 5 includes a table 22, a table 23, a table 24, a stage drive system 25, a weight reducing mechanism 21, and a sliding member 26. The table 23 is continuously moved by the stage drive system 25. At this time, the table 23 is in contact with the table 22 via the sliding member 26, and the weights of the table 23, the table 24, and the wafer 14 are all frictional resistance of the sliding member 26. Here, by providing the weight reduction mechanism 21 between the table 22 and the table 23, the weight burden on the sliding member 26 can be reduced. Since the sliding resistance and the amount of wear of the sliding member 26 are proportional to the weight, they can be reduced by the operation of the weight reducing mechanism 21, respectively. The weight reduction mechanism 21 includes a leaf spring 27 and a bearing 28 that rolls on the table 22. The leaf spring 27 generates an appropriate weight reduction force that prevents the table 23 from floating.

[0014]

As a result, defects generated in the manufacturing process can be stably found in a short time, and the defect rate of the semiconductor device is reduced by feeding back to the semiconductor process, thereby improving the reliability.

[Brief description of the drawings]

FIG. 1 is a block diagram of a semiconductor device of the present invention.

FIG. 2 is a front view of a sample stage using a weight reduction mechanism.

FIG. 3 is a side view of a sample stage using a weight reduction mechanism.

[Explanation of symbols]

1. Electron gun, 2. Condenser lens, 3. Scanning deflector,
4 Objective lens 5 Sample stage 6 Laser length measuring system 7 Wafer height measuring device 8 Secondary electron detector 9
AD converters, 10, 11: image memory, 12: operation unit,
13: scanning signal generator, 14: wafer, 101: electron optical system, 102: sample chamber, 103: control unit, 104: image processing unit, 105: system computer, 201: electron beam.

Claims (1)

[Claims] An irradiating means for irradiating the substrate with an electron beam; a detecting means for detecting secondary electrons excited by the electron beam irradiation from the substrate; and automatically moving the substrate from the atmosphere into a vacuum. Transport means for transporting, a moving means having a weight reduction mechanism while holding and moving the substrate in a vacuum, a coordinate detecting means for detecting the coordinates of the moving means, and forming and comparing an image with the secondary electrons A defect detecting means for automatically detecting a defect of a circuit pattern formed on the substrate based on a comparison between the image forming means and a defect of the circuit pattern formed on the substrate.