JPH1140631A - Method and apparatus for inspecting pattern - Google Patents

Abstract

PROBLEM TO BE SOLVED: To permit precise inspection by inspecting a pattern region not adjoining a pattern region inspected just before it, and inspecting the adjoining region after a charge accumulated in the inspected region is released. SOLUTION: A control unit causes a scanning deflector to deflect an electron beam in the direction Y for scanning, and orders to move an X-Y stage in the direction continuously and to perform two-dimensional scanning of a board to be inspected with an electron beam. First of all, two-dimensional scanning is performed in a region 1, and pattern inspection is started. Next, pattern inspection for a region 2 is started. After the inspection of the region 2, inspection for a region 3 is performed. After the inspection of the region 3, the stage moves to a region next to the regions inspected already i.e., a region 4 between the regions 1 and 2. Consequently, it becomes possible to prevent charge accumulation at scanning region end parts, since it is possible to inspect adjoining regions, after a time interval long enough for a charge accumulated in an insulator to discharge by electron beam irradiation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus and method for inspecting a semiconductor, and more particularly to an apparatus and method for inspecting a pattern on a wafer, which can stably inspect an insulator sample.

[0002]

2. Description of the Related Art In a circuit pattern inspection apparatus for inspecting a circuit pattern on a wafer using an electron beam, when a pattern composed of an insulator such as a resist is inspected by an electron beam, the inspection is performed due to charge accumulation in the insulator. Had become difficult. The order of inspection by scanning with an electron beam is described in, for example,
In the electron beam inspection method disclosed in Japanese Patent Application No. 258703, first, as shown in FIG. 3, in the region, the electron beam is scanned in the Y direction, and the stage is continuously moved in the X direction. Perform a dimensional scan. Next, the stage moves in the Y direction by the scanning width in the X direction to perform two-dimensional scanning of the next area. As described above, the conventional method sequentially analyzes the inspection areas adjacent to each other in the Y direction.

[0003]

However, when the adjacent pattern areas are scanned in order, the adjacent pattern areas are irradiated before the electric charges accumulated in the insulator by the electron beam irradiation are discharged. In particular, charge accumulation at the end of the scanning region increases, and the surface potential changes.
As a result, the generation amount and energy distribution of secondary electrons and reflected electrons obtained by electron beam irradiation change, which affects the signal detected by the detector, causing a problem that accurate inspection cannot be performed. Had occurred.

[0004]

According to the present invention, immediately after a certain pattern area is inspected, a pattern area which is not adjacent to the pattern area is inspected, and a pattern adjacent to the pattern area is released after electric charges accumulated in the inspection area are released. It is characterized by inspecting.

According to the present invention, as the charge accumulation at the pattern edge is reduced, the pattern can be inspected without affecting the detection signals of secondary electrons, reflected electrons and the like.
Accurate inspection can also be performed on patterns composed of insulators such as resists and oxide films.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described with reference to FIGS. As shown in FIG. 1, the semiconductor device manufacturing process repeats a number of pattern forming steps. The pattern forming process roughly includes steps of film formation, photosensitive resist coating, exposure, development, etching, resist removal, and cleaning. If the manufacturing conditions are not optimized in each step, the circuit pattern of the semiconductor device formed on the substrate will not be formed properly.

For example, when an abnormality occurs in the film forming process of FIG. 1, particles are generated, adhere to the wafer surface, and an isolated defect occurs. If the conditions such as the focus and the exposure time are not optimal at the time of resist exposure, there will be places where the amount or intensity of light applied to the resist is too large or insufficient, resulting in short-circuiting, disconnection, and pattern narrowing. If there is a defect on the mask or reticle at the time of exposure, similar pattern shape abnormality is likely to occur. In addition, when the etching amount is not optimized or a thin film or a particle generated during the etching, a short circuit, a projection, an isolated defect, an opening defect, or the like occurs. At the time of cleaning, abnormal oxidation is likely to occur at the corners of the pattern and the like depending on the condition of running out of water during drying.

Accordingly, in the wafer manufacturing process, it is necessary to optimize the processing conditions so that these defects do not occur, and it is necessary to detect the occurrence of an abnormality at an early stage and feed it back to the process. Therefore, in the present embodiment, an example will be described in which inspection is applied after exposure and development of resist in the n-th pattern forming step.

The basic concept of the present invention is to inspect an insulating sample such as a resist with high accuracy so that the same area is not repeatedly exposed to a charged particle beam such as an electron beam in a short time. It is to determine the measurement order. Thus, it is possible to prevent a decrease in measurement accuracy due to charge accumulation of the insulator sample.

Hereinafter, embodiments will be described in detail. FIG. 2 shows a configuration diagram of the first embodiment. The inspection apparatus is roughly composed of an electron optical system 101, a sample chamber 102, a control unit 103, and an image processing unit 104. The electron optical system 101 includes an electron gun 1, an electron beam extraction electrode 2, a condenser lens 3, a blanking deflector 4, a scanning deflector 5, a diaphragm 6, a shield pipe 7, an ExB deflector 8, and an objective lens 9. I have.

The sample chamber 102 comprises an XY stage 11, a rotary stage 12, an optical height measuring instrument 26, a position monitoring length measuring instrument 27, and a secondary electron detector 1
3 is above the objective lens 9, and the output signal of the secondary electron detector 13 is amplified by the preamplifier 21 and converted into digital data by the AD converter 22. The image processing unit 104 includes image storage units 30a and 30b, a calculation unit 33, and a defect determination unit 34. The captured electron beam image and optical image are displayed on the monitor 32. Operation commands and operation conditions of each part of the inspection apparatus are input and output from the control unit 103. Conditions such as an acceleration voltage at the time of generation of an electron beam, an electron beam deflection width, a deflection speed, a moving speed of a sample stage, and a signal capturing timing of a detector are input to the control unit 103 in advance. Further, a correction signal is generated from the signals of the optical height measuring device 26 and the position measuring length measuring device 27, and correction control is performed on the objective lens power supply 25 and the scanning signal generator 24 so that the electron beam is always irradiated to the correct position. A correction signal is sent from 28 to the circuit.

The electron gun 1 uses a diffusion-supply type thermal field emission electron source. As a result, a comparative inspection image with a small variation in brightness can be obtained, and the electron beam current can be increased, so that a high-speed inspection can be performed. The electron beam 201 is extracted from the electron gun 1 by applying a voltage to the extraction electrode 2. The electron beam 201 is accelerated by applying a high negative voltage to the electron gun. Thereby, the electron beam 2
01 is the energy corresponding to the potential, for example, 4.5
The light travels in the direction of the sample stage 11 at kV, is focused by the condenser lens 3, is further narrowed down by the objective lens 9, and is XY.
Irradiation is performed on a substrate to be inspected 10 (such as a wafer or a chip) mounted on the stage 11. A negative voltage can be applied to the substrate to be inspected 10 by the high voltage power supply 23. By adjusting the high-voltage power supply 23, it becomes easy to adjust the electron beam irradiation energy to the inspection target substrate 10 to an optimum value.

In order to acquire an image of the substrate 10 to be inspected, the substrate 10 to be inspected is irradiated with a narrowed electron beam 201 to generate secondary electrons, which are scanned by the electron beam 201 and moved by the stage. An image of the surface of the substrate to be inspected is obtained by synchronous detection. In the automatic inspection as described in the present invention, a high inspection speed is essential. Therefore, the normal SE
It does not irradiate a beam current of pA order at a low speed unlike M. Therefore, an image is formed by scanning only once or several times with a large current electron beam of, for example, 100 nA, which is about 100 times or more that of a normal SEM. For example,
One image was obtained at 1000 × 1000 pixels in 10 msec. The image signal is delayed by one image, the image comparison and evaluation are performed in synchronization with the capture of the next image, and a defect search on the circuit board is performed.

Next, a pattern inspection procedure according to the present invention will be described. Data of the measurement order is input to the control unit 103 in advance based on the material of the inspection pattern of the inspection target substrate 10 and the like. For example, if the discharge time of the charge accumulation of the pattern to be inspected is a second and the measurement time in the X direction is the control unit 1
The measurement order of the adjacent inspection areas set to 03 is selected at least after (a / b) times.

For example, FIG. 4 shows an example in which the inspection order of the two-dimensional scanning area is set at every other order. The condition is such that the inspection of the adjacent area is performed at least twice later. The control unit 103 causes the scanning deflector 5 to scan the electron beam in the Y direction, and instructs the XY stage 11 to continuously move in the X direction to two-dimensionally scan the electron beam 201 on the substrate 10 to be inspected. First, pattern inspection is started by two-dimensionally scanning the area. XY stage 11
Reaches the end in the X direction, the stage moves in the Y direction by twice the scanning width in the X direction, and starts pattern inspection of the next area. After inspection of the area, the stage is again X
The area is inspected by moving in the Y direction by twice the scanning width in the direction. After inspecting the region that is the end in the Y direction, the stage moves to the region next to the already inspected region, that is, the region between the regions. The inspection interval between adjacent regions is three times later, and the inspection interval between regions is two times later. As described above, the control unit 103 determines the inspection order of the areas so as not to always be adjacent to the previous scanning area. By using this inspection method, it is possible to inspect adjacent regions after a time interval such that charges accumulated in the insulator due to electron beam irradiation are discharged, thereby preventing charge accumulation at the end of the scanning region. be able to.

Embodiment 2 is an embodiment using a continuously moving sample stage, in which the electron beam scanning width in the direction orthogonal to the moving direction of the sample stage is an integral multiple of the width of the inspection area. For example, it is assumed that the scanning width of the electron beam in the X direction is five times the width of the inspection area. Put another inspection order in the Y direction,
That is, if the inspection order is selected like the numbers in FIG. 5, the patterns can be inspected in an order that is not always adjacent to the previous scanning area. After reaching the end in the X direction, the stage moves in the Y direction by a scanning width in the X direction or larger, for example, twice, in the Y direction, and starts inspection of the next two-dimensional scanning area.

The third embodiment is an embodiment using a sample stage of a step-and-repeat system, which moves in a unit of a section and performs inspection while standing still. FIG. 6 shows a case where the inspection area in the section is divided into 16 areas. If the inspection order is selected in the order of the circled numbers in the figure, the pattern can be inspected in an order that is not always adjacent to the previous scanning area. . After reaching the end in the X direction, the stage moves in the Y direction by a scanning width in the X direction or larger, for example, twice, in the Y direction, and starts inspection of the next two-dimensional scanning area.

[0018]

As described above, in the pattern inspection apparatus of the present invention, since the two-dimensional scanning of the sample is dispersed, the charge accumulation at a specific portion of the insulator can be suppressed. Even patterns can be inspected accurately.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a semiconductor device manufacturing process flow.

FIG. 2 is an explanatory diagram of an apparatus configuration according to a first embodiment of the present invention.

FIG. 3 is an explanatory diagram of a conventional inspection order.

FIG. 4 is an explanatory diagram of an inspection order according to the first embodiment of the present invention.

FIG. 5 is an explanatory diagram of an inspection order according to the second embodiment of the present invention.

FIG. 6 is an explanatory diagram of an inspection order according to a third embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Electron gun, 2 ... Extraction electrode, 3 ... Condenser lens, 4 ... Blanking deflector, 5 ... Scanning deflector, 6 ...
Aperture, 7: shield pipe, 8: ExB deflector, 9: objective lens, 10: substrate to be inspected, 11: XY stage,
12 rotary stage, 13 secondary electron detector, 14 suction electrode, 21 preamplifier, 22 AD converter, 23
High-voltage power supply, 24: scanning signal generator, 25: objective lens power supply, 26: optical sample height measuring device, 27: position measuring length measuring device, 30a, 30b: image storage unit, 31: delay circuit, 32 ... Monitor, 33 ... calculation unit, 34: defect determination unit,
101: electron optical system, 102: sample chamber, 103: control unit, 104: image processing system, 201: primary electron beam, 202
... first secondary electrons, 203 ... secondary electrons, 300 ...
Reflector, 301: ground electrode.

Continuing on the front page (72) Inventor Yusuke Yajima 1-280 Higashi-Koigakubo, Kokubunji-shi, Tokyo Inside the Hitachi, Ltd.Central Research Laboratories (72) Inventor Masaki Hasegawa 1-280 Higashi-Koigakubo, Kokubunji-shi, Tokyo Inside the Hitachi, Ltd. (72) Inventor Kaoru Umemura 1-280 Higashi-Koigakubo, Kokubunji-shi, Tokyo Inside the Hitachi, Ltd.Central Research Laboratory (72) Inventor ▲ Taka ▼ Fuji 1-280 Higashi-Koikekubo, Kokubunji-shi, Tokyo Inside the Central Research Laboratory, Hitachi, Ltd.

Claims (4)

[Claims] A means for two-dimensionally scanning an electron beam on a substrate on which a circuit pattern is formed; a means for imaging secondary electrons generated from the circuit pattern; A pattern inspection apparatus for performing a two-dimensional scan of an area adjacent to a two-dimensionally scanned scan area after the charges accumulated in the scan area are sufficiently discharged. 2. A step of two-dimensionally scanning an electron beam on a substrate on which a circuit pattern is formed, a step of imaging secondary electrons generated from the circuit pattern, and comparing the image with a defect of the circuit pattern. A pattern inspection method for making a determination, comprising: performing a two-dimensional scan of an area adjacent to a two-dimensionally scanned scan area after sufficient discharge of charges accumulated in the scan area. 3. A means for two-dimensionally scanning an electron beam on a substrate on which a circuit pattern is formed, a means for imaging secondary electrons generated from the circuit pattern, and comparing the image with a defect in the circuit pattern. A pattern inspection apparatus for making a determination, wherein an interval between a two-dimensionally scanned area and a next two-dimensionally scanned area is larger than the width of the two-dimensionally scanned area. 4. A step of two-dimensionally scanning an electron beam on a substrate on which a circuit pattern is formed, a step of imaging secondary electrons generated from the circuit pattern, and comparing the image with a defect of the circuit pattern. A pattern inspection method for making a determination, wherein an interval between a two-dimensionally scanned scanning area and a next two-dimensionally scanned area is larger than the width of the two-dimensional scanning.