JPH05267409A - Deflection circuit for surface processing and cross-section observing apparatus - Google Patents

Abstract

PURPOSE:To form a cross section having different angles at a plurality of points by a method wherein the processing region of a converged ion beam is continuously indicated by a pointer on a secondary electron image which is formed by the converged ion beam on the surface of a sample before processing. CONSTITUTION:A pointer which is inputted from a processing position indicating pointer circuit 21 and a secondary electron image are simultaneously displayed on a display circuit 20 and the points of the outline of a processing region are successively indicated and stored in a processing region storing circuit 22. Directions, intervals, scanning clocks, etc., of ion beam scanning are inputted and stored in a processing program registration circuit 18 as parameters for processing. A processing program calculating circuit 17 calculates rows of X-Y co-ordinates to which the ion beam is applied in accordance with the processing region and the processing parameters and makes a deflection signal generating circuit 16 output deflection signals. Scanning contents such as up and down, left and right, intervals and directions are calculated for all the points inside the outline and scanning signals are supplied to a beam deflection control circuit 15. Therefore, processing of an arbitrarily curved cross section can be instructed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used as a process monitor for defect analysis of LSIs and semiconductor manufacturing, and irradiates a focused ion beam on the surface of a sample to process a minute area on the surface, and the shape and material of its cross section The present invention relates to a deflection circuit for a focused ion beam in a surface processing and cross-section observation apparatus for obtaining a magnified image of distribution.

[0002]

2. Description of the Related Art As the application of a focused ion beam device in the semiconductor field is well known, its main functions are: (1) an enlarged image of surface irregularities and material distribution obtained by scanning a sample surface with a focused ion beam ( Secondary electron or secondary ion image)
(2) Processing of a fine area by sputtering, that is, correction of a wiring pattern, punching, wiring cutting, and (3) wiring addition by deposition of a metal film such as tungsten. In recent years, LSI devices have been miniaturized, and focused ion beam devices have been widely used as processing means on the order of submicrons. In particular, a focused ion beam device has been attracting attention in order to obtain a cross-section observation by performing cross-section processing on a failed part or foreign material part of an LSI.

In order to perform the processing of the fine area of the function (2), the processing area is designated by using the enlarged image of the sample surface of the function (1). That is, the conventional focused ion beam apparatus scans a focused ion beam in the XY directions to irradiate the sample surface, detects secondary electrons or secondary ions emitted from the sample surface, and detects a secondary electron image or secondary ion. A secondary ion image is obtained, a processing region is designated on the image, and then, the processing region on the sample surface is irradiated with a focused ion beam to perform rough processing and finishing processing. Roughing is a process of removing unnecessary parts before observing a desired cross-section in order to create a space necessary for obliquely irradiating a focused ion beam when observing a cross-section. It is determined by the depth of the cross section and the viewing angle required for cross section observation. In general, a focused ion beam is made to have a large current, and a relatively wide range is sputtered quickly to make a hole. The finishing process is to cut a desired cross section cleanly to reduce the current of the focused ion beam and to gradually sputter the cross section formed by rough processing. After the processing, the sample is tilted and the finished surface thereof is irradiated with a focused ion beam to obtain a secondary electron image or a secondary ion image, and the cross section is observed.

The designation of the processing area of the conventional focused ion beam apparatus is a rectangular pattern by two points of the start point and the end point of the XY deflection signal. And, JP-A-63-180385 (S63-
07-25), a method of processing a processing area constituted by a plurality of rectangular patterns at a uniform speed is known.

[0005]

In the conventional focused ion beam apparatus, it is only a plane cross section, and it is one plane on which the sample is tilted for observation. However, in general, the sample to be measured has a three-dimensional structure in three dimensions, and it is extremely inconvenient to use only one specific plane.

[0006]

In order to solve the above problems, a means for superimposing a pointer on a secondary electron image or a secondary ion image and a point designated by the pointer are stored in a deflection circuit for a focused ion beam. Means, means for setting processing parameters, means for calculating a processing area, and means for outputting a deflection signal by a program are provided, and at the time of processing, the sample surface is irradiated with a focused ion beam in the order of the programmed XY coordinate sequence. .. Parameters such as the scanning direction (horizontal up / down), orientation (left / right up / down), scanning interval (interlace), and scanning clock are set as a program for machining. Further, it is possible to program a plurality of processing area designations, and it is possible to perform processing sequentially. Therefore, curved cross-section processing is also possible.

[0007]

A secondary electron image or a secondary ion image obtained by scanning a focused ion beam is stored in a storage device, a pointer is placed on the image, and a desired processing area is pointed by the pointer to indicate a point on the outline. Memorize the meeting. All the points inside the outline are calculated, and at the time of processing, only these points are irradiated with the focused ion beam according to the processing parameters and in the order of the programmed XY coordinate sequence. Cross-section processing of arbitrary shape and curve can be obtained by combining the points of the outline that can be specified with the pointer. Furthermore, it is possible to sequentially shift the contour of the processing region during processing, and it is possible to obtain cross-section processing with an inclination in the depth direction of the sample surface.

[0008]

FIG. 1 shows the configuration of an embodiment for explaining a focused ion beam deflection circuit of a surface processing and cross-section observation apparatus according to the present invention. Liquid metal ion source 1 and ion beam extraction electrode 2
During this period, a high voltage is applied, and a high-intensity ion beam is extracted from the ion source 1 and accelerated. The ion beam 10 is finely focused on the surface of the sample 7 by the electrostatic lenses 3 and 6 and the slit 4. An ion source control circuit 12, an emission control circuit 13, and an electrostatic lens control circuit 14 are connected to the ion source 1, the extraction electrode 2, and the electrostatic lenses 3 and 6, respectively, and a desired potential is applied to each of them. A direct current component that determines the position of the ion beam and an alternating current component for obtaining a secondary electron image or a secondary ion image, that is, a scanning signal, are applied to the ion deflection electrode 5 in an overlapping manner from the ion beam deflection control circuit 15. When the surface of the sample 7 is irradiated with the focused ion beam, secondary electrons characterized by the shape and material distribution of the sample surface,
When secondary ions and the like are emitted and the focused ion beam is continuously irradiated for a certain period of time, the sputtering on the surface of the sample is overlapped and the surface is processed. Secondary electrons or secondary ions emitted from the surface of the sample are detected by the secondary charged particle detector 9, and in synchronization with the ion beam deflection control circuit 15, a secondary electron image or secondary ion image storage circuit 17 is stored. Remember. In order to obtain a desired processing position of the sample, the sample fine movement stage 8 is set by XYZ, rotation, and inclination by the stage control circuit 23. Generally, a processor (not shown) controls each of the above control circuits. The configuration so far is a conventional focused ion beam device. Further, FIG. 2 illustrates processing of the sample surface and observation of its cross section in the conventional focused ion beam apparatus. FIG. 2 (a) shows a focused ion beam 10 (a beam having a large beam diameter and a large beam current is used for rough processing, and a beam is used for fine portion processing and finishing processing on the surface of a sample 7 positioned horizontally. A small diameter and a small beam current is used.) By repeatedly scanning the processing area, the surface of the processing area is sputtered and a part of the surface is scraped off. As shown in FIG. 2C, when a part of the surface of the semiconductor element is processed, the laminated internal structure appears. Figure 2
The secondary electron image or the secondary ion image obtained by irradiating the sample, which is processed as shown in (a) or (c) with a tilt, with a beam 10 that is extremely finely focused and scanned, is a focused ion beam. It is a cross-sectional observation by. However, in the conventional focused ion beam device, the deflection of the focused ion beam is XY.
Although only the rectangular processing area is formed only by the scanning in which the direction is fixed, in the present invention, as in the configuration of FIG. 1, the pointer input from the processing position designation pointer circuit 21 and the secondary electron image or secondary The secondary electron image or secondary ion image of the sample surface before processing stored in the ion image storage circuit 19 is simultaneously displayed on the display circuit 20, and the points on the outer contour of the processing region are continuously designated. This designation is stored in the machining area storage circuit 22 each time. Further, the machining program registration circuit 18 stores and stores parameters such as a scanning direction of an ion beam, an interval, and a scanning clock as parameters for machining. The machining program calculation circuit 17 calculates an XY coordinate sequence for irradiating an ion beam during machining from the stored machining area and machining parameters, and the deflection signal generation circuit 1
The output of the deflection signal is controlled by 6. The scanning contents such as up / down, left / right, interval, direction, etc. are calculated for all the points inside the outer contour, and a scanning signal is supplied to the beam deflection control circuit 15.
Therefore, it is possible to specify the cross-section processing of an arbitrary curve. Further, if the shift of the machining region with the machining time is registered in the machining program and executed, a cross section inclined with respect to the depth direction can be obtained.

FIG. 3 shows an embodiment of surface processing according to the present invention. FIG. 3A is an example of a cross section having a complicated processed cross section and a plurality of locations in which the directions of the cross sections are also changed. FIG. 3B is an example of a cross section that is inclined with respect to the depth direction by shifting the processing region with the processing time during the processing. FIG. 3C is a cross-sectional example of a combination of a cross-section parallel to the sample plane and a cross-section in the depth direction in which the working depth is partially designated. Figure 3
When (a) and FIG. 3 (c) are combined, three cross sections at a certain point in the three-dimensional structure are obtained.

[0010]

EFFECT OF THE INVENTION Designation of the processing area of the focused ion beam
Cross-sections having different angles at a plurality of points can be obtained by successively designating with a pointer on the secondary electron or secondary ion image by the focused ion beam on the sample surface before processing. By shifting the processing region with the processing time, a cross section inclined with respect to the depth direction can be obtained.

[Brief description of drawings]

FIG. 1 is a block diagram illustrating an embodiment according to the present invention.

FIG. 2 is a diagram illustrating surface processing and cross-sectional observation by a general focused ion beam device.

FIG. 3 is a diagram illustrating an example of surface processing according to the present invention.

[Explanation of symbols]

1 ... Liquid metal ion source, 2 ... Ion beam extraction electrode,
3, 6 ... Electrostatic lens, 4 ... Slit, 5 ... Ion beam deflection electrode, 7 ... Sample, 8 ... Sample fine movement stage, 9 ... Secondary charged particle detector, 10 ... Focused ion beam, 11 ... Secondary electron or Secondary ions, 12 ... Ion source control circuit, 13 ...
Emission control circuit, 14 ... Electrostatic lens control circuit, 1
5 ... Ion beam deflection control circuit, 16 ... Deflection signal generation circuit, 17 ... Machining program calculation circuit, 18 ... Machining program registration circuit, 19 ... Secondary electron image or secondary ion image storage circuit, 20 ... Display circuit, 21 ... Machining position designation pointer circuit, 22 ... Machining area storage circuit, 23 ... Sample fine movement stage control circuit.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location H01L 21/66 N 8406-4M

Claims (1)

[Claims] 1. A means for generating ions, an ion beam focusing means composed of an electrostatic lens and a slit, and irradiating the focused ion beam on a sample surface to deflect the XY beam of the ion beam and secondary electrons. Alternatively, a means for detecting secondary ions and a means for storing and displaying the secondary electron image signal or the secondary ion image signal thereof are provided to detect the secondary electrons or secondary ions emitted from the sample surface, The sample surface image of the area is obtained, the sample surface designated on the secondary electron image or the secondary ion image is provided with a means for irradiating a focused ion beam for surface processing, and then the sample is inclined. In the surface processing and cross-section observing device for observing the cross section by the means for obtaining the sample surface image, the pointer means and the pointer means which can be displayed simultaneously with the secondary electron image or the secondary ion image and designated and designated can be designated. It is equipped with a means for storing the designated processing area designation, a means for inputting and registering parameters at the time of processing, and a means for calculating an XY coordinate sequence at the time of processing, and the deflection of the focused ion beam irradiated on the sample surface Any combination of coordinates, Y coordinate and irradiation time,
A deflection circuit for a surface processing and cross-section observation apparatus, which is capable of surface processing.