KR100694580B1 - method for manufacturing Transmission Electron Microscope of Specimen for Analyzing - Google Patents

Abstract

Disclosed is a method for fabricating a specimen for TEM analysis using an ion beam focusing device. In the specimen for TEM analysis produced using the ion beam focusing apparatus, a mark for identifying the analysis point is formed on a wafer including the analysis point. A protective film is deposited on the analysis point, and the wafer is etched to form preliminary specimens so that both end surfaces perpendicular to the analysis direction of the analysis point are formed. Then, the preliminary specimen is separated from the wafer on which the preliminary specimen is formed to form an analytical specimen. Providing the TEM analysis specimen manufacturing method comprising the step of attaching the analytical specimen to the grid can reduce the contamination and production time generated during the TEM analysis specimen manufacturing.

Description

Method for manufacturing Transmission Electron Microscope of Specimen for Analyzing

1 is a process chart showing a manufacturing process of a specimen for a conventional TEM analysis.

Figure 2 is an enlarged perspective view of a conventional TEM analysis specimen.

3A to 3E are diagrams illustrating a process for explaining a method for preparing a specimen for TEM analysis of the present invention.

Explanation of symbols on the main parts of the drawings

50: marker for analysis 52: analysis point

54 protective film 56 analytical specimens

58: carbon coating grid T: thickness of the analytical specimen

W: Wafer

The present invention relates to a method for preparing a Specimens for Transmission Electron Microscope (TEM) analysis, and more particularly, to a method for manufacturing TEM Specimens using FIB (Focusing ion beam).                         

In general, a plurality of films are formed on a wafer as the deposition process is repeatedly performed in a semiconductor device manufacturing process. If a defect occurs in a specific film among the films formed by the above process, an error occurs in the semiconductor device formed by the subsequent process.

Therefore, after selecting a wafer in which defects are generated among the wafers in which the semiconductor device manufacturing process is performed, analytical work is performed to determine whether a specific film is defective by preparing an analytical specimen.

In order to use the TEM for the analysis, the thickness of the analytical specimen must be very thin because an electron beam must be transmitted into the analytical specimen. Therefore, before performing the analysis, a predetermined sample preparation process for thinning the thickness of the analytical specimen should be performed.

TEM analysis specimens for determining whether a specific film formed on the wafer is presently defective include an ion milling method and an focusing ion beam (FIB) method.

In the method using the FIB, the peripheral portion of the analysis point is etched while observing the analysis point in the analysis specimen electronically. Therefore, since the thickness of the analysis specimen can be adjusted, there is an advantage in that a sample for TEM analysis can be easily produced.

As an example of a method for manufacturing a TEM analysis specimen using the FIB, US Patent No. 6,194,720 (issued Li et al) discloses a method for manufacturing a TEM analysis specimen that can transmit electrons using FIB U.S. Patent No. 6,080,991 (issued Tsai) discloses a method for fabricating a specimen for TEM analysis in which a thin film is formed in an area to be analyzed using FIB.

1 is a process chart showing a manufacturing process of a specimen for a conventional TEM analysis.

Referring to FIG. 1, a mark for identifying the analysis point is formed on the wafer including the analysis point by using an ion beam. (S100) The specimen is 2 × 3 mm so that the analysis point displayed on the wafer is located at the center. A diamond cutter is cut to a size of (S200). The specimen including the analysis point is ground to have a thickness of 40 μm.

Then, the specimen is attached to a nickel grid using an epoxy adhesive (S400). A protective film is deposited on the analysis point to protect the analysis point. (S500) Analysis including the analysis point Both sides of the specimen are etched with an ion beam to form a dragon specimen (S600). At this time, the ion density of the ion beam is adjusted to 11500 to 70 pA and sequentially etched from the step of high current density to the step of low.

Figure 2 is an enlarged perspective view of a conventional TEM analysis specimen.

The TEM analysis specimen 10 shown in FIG. 2 is attached to the nickel grid 12 with an epoxy adhesive. When the periphery of the analysis point 14 of the specimen is etched to form both end surfaces perpendicular to the analysis direction, an analysis specimen 10 having a predetermined width and height and a thickness T1 or less is formed.

It takes a long time to go through the above process, there is a problem that the success rate of manufacture of the test specimen for analysis is lowered. In addition, the analytical specimens cause contamination in the process of adhering to the nickel grid using an epoxy adhesive after the grinding operation. Therefore, a problem arises that it is difficult to accurately analyze the specimen for TEM analysis.

Accordingly, an object of the present invention is to provide a method for preparing a test specimen for TEM analysis, which reduces the production time of the test specimen including the analysis point and prevents contamination of the specimen by using an ion beam focusing device (FIB).

The present invention for achieving the above object

Forming a mark for identifying the analysis point on a wafer comprising the analysis point;

Depositing a protective film on the analysis point;

Forming a preliminary specimen by etching a predetermined portion of the wafer such that both cross-sections perpendicular to the analysis direction of the analysis point are formed while including the analysis point;

Separating the preliminary specimen from the wafer to form an analytical specimen; And

By adsorbing the analytical specimen on a grid, to constitute a specimen for TEM analysis.

By preparing the TEM analysis specimen directly on the wafer using the FIB as described above, it is possible to prevent contamination of the TEM analysis specimen and shorten the manufacturing time.                     

Hereinafter, a preferred embodiment of the present invention will be described in more detail with reference to the accompanying drawings.

3A to 3E are diagrams illustrating a process for explaining a method for preparing a specimen for TEM analysis of the present invention.

Referring to FIG. 3A, a wafer W in which a defect is generated is selected to perform an analysis operation for determining whether a specific film is defective among a plurality of films formed on the wafer W. FIG. The analysis point 52 to be observed on the wafer W is observed by an electron microscope to determine its position. The marks 50 for identifying the analysis points 52 are positioned on the coordinate axes perpendicularly intersecting with respect to the analysis points 52 to be observed, and a predetermined portion of the wafer W is etched by FIB. It is formed by.

If the mark 50 for identifying the analysis point 52 is not formed on the wafer W, an analysis specimen which does not include the analysis point 52 may be formed in the grinding process and the milling process. . Then, a situation arises in which the specimen for analysis is produced again for a long time.

Referring to FIG. 3B, a protective film 54 is deposited on the analysis point 52. The protective film 54 minimizes damage that may occur on the surface of the TEM analysis specimen by the FIB when observing or micro-milling the analysis point 52 of the TEM analysis specimen using the FIB. It plays a role. The protective film 54 may be a tungsten (W) film, a platinum (Pt) film, a carbon (C) film, an aluminum (Al) film, or the like.

Referring to FIG. 3C, the preliminary specimen 55 may be formed by etching the analysis point 52 on which the protective film 54 is formed, with the FIB perpendicular to the analysis direction from the peripheral portion to the center direction. The preliminary specimen 55 forms both cross sections including the analysis point 52 to be observed. Both cross-sections of the preliminary specimen 55 are formed to have a thickness of 600 to 1000 mV, which can transmit TEM electrons, which is a thickness capable of analyzing the specimen using a transmission electron microscope. Specifically, while preliminarily adjusting the current density of the FIB to 2700 to 70 Pa (pico ampere), a predetermined portion of the wafer may be etched to form the preliminary specimen to have a thin thickness of 600 to 1000 kW. In other words, by increasing the current density of the FIB coarse milling around the analysis point 52, the fine milling while gradually decreasing the current density as the etching is closer to the analysis point 52 in the peripheral portion Is carried out. Therefore, it is possible to shorten the time for forming the preliminary test piece 55 and to have an accurate thickness.

Referring to FIG. 3D, the preliminary specimen 55 is separated from the wafer W to be formed as an analytical specimen 56.

Specifically, the preliminary specimen 55 formed in the previous step is not separated from the wafer W on each side except for both cross-sections including the analysis point 52. Therefore, by etching each surface of the preliminary test piece 55 which is not separated from the wafer W by FIB, the preliminary test piece 55 is separated from the wafer W and formed as an analytical test piece. The analytical specimen 56 formed not only has a thickness capable of transmitting TEM electrons, but also includes an analysis point 52 and a mark 50.

Referring to FIG. 3E, the sample for analysis is adsorbed on a grid to complete the sample for TEM analysis.                     

The analytical specimen 56 separated from the wafer has a very thin thickness T of 600 to 1000 mm 3, which is not easy to move. Therefore, fine needles with static electricity are used to move onto the grid 58. That is, only the analysis specimen 56 placed on the wafer by static electricity is adsorbed onto the fine needle and then moved onto the grid 58. Since the static electricity of the fine needle is relatively smaller than that of the grid 58, the analytical specimen 56 is separated from the fine needle and adsorbed to the grid 58.

The analytical specimen 56 may be adsorbed onto the grid 58 without performing a separate attachment process using an epoxy adhesive. This is because, unlike the conventional analytical specimens, a fine sized analytical specimen 56 can be manufactured by directly processing a preliminary specimen on a wafer without fabricating the specimen using an epoxy adhesive on a grid. In addition, the analytical specimen 56 is adsorbed on the grid 58 only by the static electricity generated between the grids 58, and the TEM measurement of the analytical specimen 56 is performed on the vacuum atmosphere so that no movement occurs. Therefore, it is possible to prevent contamination of the test specimen with the epoxy adhesive.

The fine needle having static electricity generally uses a glass material. However, there is no problem using a material having static electricity. In other words, even when using a material having an electrostatic energy is obviously included in the spirit of the present invention.

The grid 58 is not a conventional horseshoe shape but a square plate. The grid 58 is a material that transmits electrons, and is coated with a carbon material on an upper surface on which the analytical specimen 56 is placed. This is to prevent the TEM analysis specimens from adsorbing (charging) the electrons and make the analysis easier. The coated material of the grid 58 is limited to carbon. However, the coated material of the grid 58 may be a material having a characteristic of transmitting a conductive material and an electron except for metal.

TEM analysis specimens formed by the method described above are fabricated directly on the wafer containing the analysis points, thereby reducing manufacturing process steps. In addition, since the epoxy adhesive is not used when attaching the analytical specimen on the grid, contamination of the TEM analytical specimen by the adhesive may be minimized.

As described above, according to the present invention, a wafer including an analysis point may be etched by FIB to form a specimen having a predetermined size and used for TEM analysis. Therefore, the process step for forming the TEM analysis specimen is shortened, the manufacturing time of the TEM analysis specimen is reduced, and the manufacturing success rate is increased. In addition, since the epoxy adhesive is not used, contamination of the TEM analysis specimen by the adhesive may be minimized. As a result, analysis errors that may occur due to contamination of the TEM analysis specimen may be reduced, and thus more accurate analysis may be performed.

Although described above with reference to a preferred embodiment of the present invention, those skilled in the art will be variously modified and changed within the scope of the invention without departing from the spirit and scope of the invention described in the claims below I can understand that you can.

Claims (6)

Forming a mark for identifying the analysis point on a wafer comprising the analysis point; Depositing a protective film on the analysis point; Forming a preliminary specimen by etching the wafer so that both cross-sections perpendicular to the analysis direction of the analysis point are formed while including the analysis point; Separating the preliminary specimen from the wafer to form an analytical specimen; And TEM analysis specimen manufacturing method comprising the step of adsorbing the analysis specimen on a grid. The method of claim 1, wherein the etching for forming the preliminary specimen is performed using FIB. The method of claim 1, wherein the forming of the analytical specimens by separating the preliminary specimens is performed by etching respective portions of the preliminary specimens formed in the wafer. The method of claim 1, wherein both cross sections perpendicular to the analysis direction of the analysis point are etched to have a thickness of 600 to 1000 μm. The method of claim 1, wherein the test specimen is transferred to and adsorbed on a grid of needles formed of a glass material having static electricity. The method of claim 1, wherein the grid has a plate shape and is coated with a conductive carbon material.

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