Optics: measuring and testing – Inspection of flaws or impurities – Surface condition
Reexamination Certificate
2000-03-15
2001-11-20
Pham, Hoa Q. (Department: 2877)
Optics: measuring and testing
Inspection of flaws or impurities
Surface condition
C356S237500, C356S614000, C356S072000
Reexamination Certificate
active
06320655
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a defect-position identifying method for a semiconductor substrate.
2. Description of the Related Art
With the high density integration of ULSIs, zero defects in the surface layer of a semiconductor substrate serving as an element active layer are required. It is generally known that defects due to pull-up, called on grown-in defects, exist in the crystal of a semiconductor substrate which is obtained by slicing and polishing a single crystalline silicon pulled up from a crucible. These defects have only a density of about 10
6
cm
−'
detected mainly by light scattering. Therefore, it is very difficult to carry out the direct observation by means of a transmission electron microscope (which will be also hereinafter referred to as a “TEM”) or an atomic force microscope (which will be also hereinafter referred to as an “AFM”), and the substance thereof did not clear until recent years.
However, it was succeeded in 1995 to observe defects themselves in a gate oxide film by means of a TEM by utilizing the copper's property of being selectively deposited on defect existing places, and it was revealed that most of these defects comprised voids.
In general, systems for evaluating a semiconductor substrate having defects are classified into two kinds of systems, i.e., systems for macroscopically catching the presence of defects, and systems for microscopically catching the presence of defects. The macroscopically catching systems are classified into two kinds of systems, i.e., systems for catching defects on the surface of a semiconductor substrate (e.g., a particle counter), and systems for catching defects directly below the surface of a semiconductor substrate (e.g., a visible light scattering topography), as shown in FIG.
16
. The microscopically catching systems are classified into two kinds of systems, i.e., systems for catching defects on the surface of a semiconductor substrate (e.g., AFM), and systems for capturing defects directly below the surface of a semiconductor substrate (e.g., a scanning capacitance microscope (which will be also hereinafter referred to as a “SCM”) and a cross-section TEM), as shown in FIG.
16
. Furthermore, although the SCM originally carries out an evaluating method for obtaining a two-dimensional distribution of the density of dopant (impurity) in a semiconductor element, the SCM can also be used for evaluating defects below the surface, which can not be observed by the AFM.
In order to identify the position of a defect, it is general to evaluate the defect by a microscopically catching system after evaluating the defect by a macroscopically catching system. It is therefore important to deliver coordinate values indicative of the position of the defect between the macroscopically catching system and the microscopically catching system.
Conventionally, the coordinate values of the defect have been measured by using the X-Y stage of each of systems, on which a semiconductor substrate is mounted, and the shape of the semiconductor substrate (a circumference and an orientation flat or notch).
However, there is a limit to the mechanical precision of the stage, and the shape of the semiconductor substrate has errors during working. Therefore, even if a defect is found by the macroscopically capturing system, the defect does not always come within the range of the microscopically catching system, so that there is a problem in that the position of the defect can not be identified.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to eliminate the aforementioned problems and to provide a defect-position identifying method for a semiconductor substrate, which is capable of precisely identifying the position of a defect.
In order to accomplish the aforementioned and other objects, according to a first aspect of the present invention, there is provided a defect-position identifying method for a semiconductor substrate comprising the steps of: forming at least three reference points on a semiconductor substrate; detecting the reference points and a defect on the semiconductor substrate by means of a first evaluating system, which is provided for evaluating the defect on the semiconductor substrate, to measure coordinate values of the reference points and the defect in a system of coordinates of the first evaluating system; detecting the reference points on the semiconductor substrate by means of a second evaluating system, which is provided for evaluating the defect on the semiconductor substrate, to measure coordinate values of the reference points in a system of coordinates of the second evaluating system; determining an affine transformation for transforming the system of coordinates of the first evaluating system to the system of coordinates of the second evaluating system on the basis of the coordinate values of each of the reference points in the first and second evaluating systems; and identifying the position of the defect in the system of coordinates of the second evaluating system on the basis of the determined affine transformation and the coordinate values of the defect in the system of coordinates of the first evaluating system.
The first evaluating system may be a particle counter, and the second evaluating system may comprise an optical microscope and an atomic force microscope having a common system of coordinates to the optical microscope, the coordinate values of the reference points in the system of coordinates of the second evaluating system being measured by means of the optical microscope.
Alternatively, the first evaluating system may comprise an optical microscope and a visible light scattering topography having a common system of coordinates to the optical microscope, and the second evaluating system may comprise a focused ion beam drawing system, the coordinate values of the reference points and the defect in the system of coordinates of the first evaluating system being measured by means of the optical microscope and the visible light scattering topography.
The defect-position identifying method for a semiconductor substrate may further comprise a step of selecting an internal defect existing in the semiconductor substrate from the defects detected by means of the visible light scattering topography, and the step of identifying the position of the defect in the system of coordinates of the second evaluating system may comprise the steps of: estimating the position of the defect in a system of coordinates of the focused ion beam drawing system on the basis of the determined affine transformation and coordinate values of the selected defect to form a plurality of etched impressions near the estimated position; deriving coordinates and relative positions of the selected defect and the etched impressions by means of a visible light scattering topography; measuring coordinate values of the etched impressions by means of a focused ion beam drawing system; determining a second affine transformation on the basis of the coordinate value of the etched impressions by the focused ion beam drawing system and the coordinate values of the etched impressions by the visible light scattering topography; and estimating the position of the defect in the system of coordinates of the focused ion beam drawing system on the basis of the second affine transformation and the coordinate values of the defect by the visible light scattering topography.
According to a second aspect of the present invention, there is provided a defect-position identifying method for a semiconductor substrate comprising the steps of: forming at least three reference points on a semiconductor substrate; detecting the reference points and defects of the semiconductor substrate by means of a first evaluating system, which is provided for evaluating the defects of the semiconductor substrate, to measure coordinate values of the reference points and defects in a system of coordinates of the first evaluating system; selecting an internal defect exis
Matsushita Hiroshi
Toyomaru Youko
Tsuchiya Norihiko
Kabushiki Kaisha Toshiba
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Pham Hoa Q.
Punnoose Roy M
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