Radiant energy – Inspection of solids or liquids by charged particles – Analyte supports
Reexamination Certificate
2002-02-21
2004-04-06
Lee, John R. (Department: 2881)
Radiant energy
Inspection of solids or liquids by charged particles
Analyte supports
C250S492100, C250S377000, C073S864910
Reexamination Certificate
active
06717156
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a technology of extracting a micro-sample from a specimen substrate, i.e., a technology of separating, extracting, and storing of the micro-sample. More particularly, the present invention relates to a method and an equipment for separating and extracting a micro-sample including a specific region from a specimen substrate, and for storing it.
2. Description of the Related Prior Arts
In recent years, in a structure analysis of semiconductor devices, there has been demanded an observation of a very minute structure which is so small that, at a resolving power of an ordinary scanning electron microscope (hereinafter, abbreviated as an SEM), the structure cannot be observed any longer. As a result, observation by means of a transmission electron microscope (hereinafter, abbreviated as a TEM) is indispensable in place of an SEM. As for the fabrication of an observation micro-sample to be used for TEM observation, there is a method described in WO99/05506 (cited reference 1). With the method described in the foregoing cited reference 1, first, the periphery of a region desired to be subjected to an analysis on a specimen substrate (hereinafter, referred to as an observation region) is subjected to ion beam sputtering processing, thereby defining and forming the observation region. Then, the tip of a probe is firmly joined to the observation region thus defined and formed. Subsequently, in order to separate the observation region from the specimen substrate, ion beam sputtering processing is performed thereon to separate and extract a micro-sample including the observation region from the specimen substrate. Then, the micro-sample separated and extracted while being firmly joined to the probe tip is transferred to a position at which a sample holder exists. The extracted micro-sample is then fixed on the sample holder. Thus, the probe tip is cut off from the micro-sample by an ion beam sputtering method. With the foregoing operation, separation and extraction of the micro-sample, and firm attachment (storing) of the micro-sample onto the sample holder are completed. Thereafter, a desired observation, analysis, and measurement are performed on the observation region on the micro-sample which has been cut off from the probe tip and firmly attached on the sample holder.
Further, as another method, in Japanese Published Unexamined Patent Application No. Hei 8-132363 (cited reference 2), there is proposed a two-finger microhand mechanism whereby a minute micro-sample is held by effecting extension and contraction of two hands by piezoelectric elements by means of a parallel linkage. As still other method, in Japanese Published Unexamined Patent Application No. Hei 3-154784 (cited reference 3), there is proposed a tweezers mechanism using bimorph type piezoelectric elements as driving sources. With either of these methods, the micro-sample is held by moving the hands or tweezers by using piezoelectric elements.
Further, in the section in the literature (cited reference 4) entitled “Specimen Preparation for Transmission Electron Microscopy of Materials IV” on pages 19 to 27 of Material Research Society (MRS) Symposium Proceedings, vol. 480, L. A. Giannuzzi et. al., disclose a Lift-Out method. With this method, a thin specimen portion for TEM observation is formed in a specimen substrate by using an FIB (Focused Ion Beam) (corresponding to the steps of
FIGS. 21A
to
21
G). After formation of the thin specimen portion, the specimen substrate is taken out into the air, and placed under an optical microscope. Thus, a sharpened glass rod is brought to the proximity of the thin specimen portion. Then, the sharpened tip of the glass rod is pressed against a part of the thin specimen portion to separate the thin specimen portion from the specimen substrate. Further, the tip of the same glass rod is brought to the proximity of the separated thin specimen portion. Accordingly, the thin specimen portion is allowed to electrostatically adsorb to the glass rod tip by the static electroricity occurring at the glass rod tip. The thin specimen portion adsorbed and held on the glass rod tip is transferred onto a carbon film-coated hollow grid, and the thin specimen portion is attached to, and held by the hollow grid so as to face the carbon film. The hollow grid holding the thin specimen portion is introduced into a specimen chamber of a TEM to permit the TEM observation of the thin specimen portion.
Still further, in WO99/17103 (cited reference 5), mention is made of the use of tweezers for extracting a micro-sample. However, neither disclosure nor suggestion is made on the mechanism or the structure of the ones referred to as the tweezers.
The foregoing prior art technologies have the problems as shown below.
A first problem is in that contamination may be caused on the micro-sample and the specimen substrate upon extracting the micro-sample. In the prior art technology disclosed in the cited reference 1 described above, when the probe tip is firmly joined to the vicinity of the observation region of the specimen substrate, the firm joining therebetween is established through an ion beam assisted deposition film (hereinafter, referred to as a deposition film) or an ion beam sputtered particle redeposition film. This entails the following problem. When an assist gas to be the raw material for the deposition film is supplied, the observation region in the micro-sample and the neighboring region thereof are contaminated by the assist gas. The region which has been once contaminated is difficult to define. Further, it also causes failures in the subsequent and later steps. Still further, the contaminated region may also be expanded according to the steps. In such a case, unfavorably, the specimen substrate cannot be used for observation or analysis in the subsequent and later steps any longer.
A second problem is a problem associated with the extraction of the micro-sample. The cited reference 1 has a description to the effect that an electrostatic adsorption method may be used as the method for firmly joining the probe tip to the micro-sample. Further, the method in which the micro-sample is held by utilizing the electrostatic adsorption force at the glass rod tip is known as the Lift-Out method (the cited reference 4). With this method, there occurs no problem of contamination on the micro-sample because the electrostatic adsorption method is used. However, since the micro-sample is minute, a sufficient electrostatic force cannot be given thereto. Accordingly, the micro-sample is difficult to hold with stability. Specifically, with this method, when the separated minute micro-sample is transferred onto the grid, the specimen substrate is taken out into the air (into a laboratory), and then the micro-sample is electrostatically adsorbed to the glass rod tip. Therefore, the electrostatic adsorption force of the micro-sample to the glass rod tip largely depends on the humidity in the laboratory. For this reason, it may happen that, the micro-sample cannot be adsorbed to be separated and extracted from the specimen substrate, or the micro-sample is dropped during transfer onto the grid. This results in a very low probability (success rate) that the micro-sample can be ideally attached onto the carbon film. Further, the thin specimen is not always adsorbed to the tip of the glass rod, and it is often attached to the side of the glass rod according to the distribution of the generated electrostatic force. In this case, it is not possible to attach the micro-sample onto the carbon film-coated surface on the grid. Once the micro-sample is adsorbed to the side of the glass rod, the micro-sample cannot be transferred to the tip of the glass rod afterward because the micro-sample is a thin piece with very minute dimensions of about several micrometers to ten and several micrometers per side. After all, the micro-sample cannot be attached onto the carbon film-coated surface of the grid, and hence it cannot be made available for u
Fukuda Muneyuki
Koike Hidemi
Shichi Hiroyasu
Sugaya Masakazu
Umemura Kaoru
Antonelli Terry Stout & Kraus LLP
Hitachi , Ltd.
Hughes James P.
Lee John R.
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