X-ray or gamma ray systems or devices – Specific application – Diffraction – reflection – or scattering analysis
Reexamination Certificate
1999-05-28
2001-03-06
Bruce, David V. (Department: 2876)
X-ray or gamma ray systems or devices
Specific application
Diffraction, reflection, or scattering analysis
C378S076000, C378S081000
Reexamination Certificate
active
06198796
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method and apparatus for automatically selecting Bragg reflections and to a method and system for automatically determining crystallographic orientation, which are useful in analyzing and characterizing structures of crystal samples such as wafers for semiconductor and thin films deposited on the wafers.
2. Description of the Related Art
In crystal structure analysis developed for analysis of atomic structure, x-rays, or particles beams such as neutron beams or electron beams are applied to a crystal sample with the unknown structure, and then, using diffraction phenomenon of rays scattered by the crystal sample, the lattice type of the crystal sample or the atomic arrangement in the lattice are clarified. In this crystal structure analysis, for example, x-rays are used for the analysis of electron density in the crystal sample, neutron beams are used for the analysis of atomic nuclei positions in the crystal sample, and electron beams are used for the analysis of electric potential in the crystal sample.
On the other hand, a method, so-called two-reflection method, for determining the crystallographic orientation of a crystal sample having known crystal structure has been utilized frequently. In this two-reflection method, two Bragg reflections in the recipricol space of the crystal sample are searched, and then the crystallographic orientation are determined using the positions of the obtained two Bragg reflections.
More specifically, in this two-reflection method, first, when the reciprocal lattice of a crystal sample is at the standard position, reference Bragg reflections K
1
and K
2
together forming a basis for determination of crystallographic orientation of this crystal sample are selected arbitrarily, as shown in FIG.
1
(
a
). Next, actual Bragg reflections K
1
′ and K
2
′ satisfying their diffraction conditions, i.e., 2&thgr;-angles, &ohgr;-angles, &khgr;-angles, and &phgr;-angles, of the reference Bragg reflections K
1
and K
2
, respectively, are actually measured with a four-axis goniometer system, as shown in FIG.
1
(
b
). Then, rotation angle from the reference position of the reciprocal lattice is determined using the positions of the actual Bragg reflections K
1
′ and K
2
′ (i.e., using the rotation angles from the reference Bragg reflections K
1
and K
2
to the actual Bragg reflections K
1
′ and K
2
′). In this way, the actual crystallographic orientation of the crystal sample are determined.
A four-axis goniometer system is well-known in the art. For example, as shown in
FIGS. 2 and 3
, the four-axis goniometer system comprises a 4-axis goniometer
100
having four rotating axes (i.e., an &OHgr;-axis for determining the crystal direction of a crystal sample
200
, a X-&PHgr; assembly carried on the &OHgr;-axis, and 2&thgr;-axis for detecting diffracted x-rays), an x-ray source
110
, a detector
120
such as an x-ray counter for detecting diffracted rays, a computer
130
used for control, and a 2&thgr;-rotation driving device
141
, an &OHgr;-rotation driving device
142
, a &khgr;-rotation driving device
143
and a &phgr;-rotation driving device
144
for rotating the respective rotation axes of the 4-axis goniometer
100
. The computer
130
has a CPU
131
, a memory
132
, and a CRT display
133
.
The rotation angles of the 2&thgr;-axis, &OHgr;-axis, X-axis, and the &phgr;-axis of the 4-axis goniometer
100
are, respectively, 2&PHgr;-angle that is the angle of diffraction, &ohgr;-angle that is the angle of incidence, &khgr;-angle that is the tilt angle of the crystal sample
200
, and &phgr;-angle that is the angular position of the crystal sample
200
on the &PHgr;-axis.
The computer
130
controls the 2&thgr;-rotation driving device
141
, the &ohgr;-rotation driving device
142
, the &khgr;-rotation driving device
143
, and the &phgr;-rotation driving device
144
so as to rotate the 2&thgr;-axis, &OHgr;-axis, X-axis, and &PHgr;-axis so that the actual angles of the 4-axis goniometer
100
becomes equal to the diffraction conditions, i.e., 2&thgr;-angles, &ohgr;-angles, &khgr;-angles, and &phgr;-angles, of the reference Bragg reflections K
1
and K
2
. Then, the diffracted x-rays at these 2&thgr;-angles, &ohgr;-angles, &khgr;-angles, and &phgr;-angles, i.e., the actual Bragg Reflections K
1
′ and K
2
′ satisfying the diffraction conditions, are detected by the detector
120
.
However, in this prior art method for determining the crystallographic orientation using the two-reflection method described above, the two reference Bragg reflections K
1
and K
2
forming a basis for the determination of the crystallographic orientation must be selected manually. Automatic selection techniques using a computer are not yet established. Therefore, after selecting the reference Bragg reflections K
1
and K
2
manually, actual Bragg reflections K
1
′ and K
2
′ must be measured in additional experiments to find the positions accurately, and then the crystallographic orientation are computed. Thus, determination of the crystallographic orientation in one continuous process could not have been made, thereby making it very cumbersome to perform and time-consuming. Consequently, there has been a great demand for an technique capable of automatically determining the crystallographic orientation in one continuous process.
SUMMARY OF THE INVENTION
The present invention has been made in view of the foregoing circumstances, and it is an object of the present invention to provide a novel method and apparatus that are free of the foregoing problems with the prior art technique and are capable of selecting Bragg reflections automatically and easily.
this method and apparatus automatically select two Bragg reflections as reference Bragg reflections pc1 and pc2, using a computer. The reference Bragg reflections pc1 and pc2 form a basis for determination of crystallographic orientation of a crystal sample by the two-reflection method. First, x-ray intensities and diffraction conditions of all Bragg reflections which are measurable are calculated using crystallographic information given to the computer. This crystallographic information is information intrinsic to crystals of the crystal sample, such as space groups, lattice constants and atomic positions, and the diffraction conditions to be calculated using such crystallographic information are 2&thgr;-angles, &ohgr;-angles, &khgr;-angles, and &phgr;-angles. Next, a weight-point is obtained and assigned to each of the Bragg reflections according to both its x-ray intensity and its angle (hereinafter denoted by &Dgr;G) between the sample normal and its scattering vector. Then, two Bragg reflections having the first and second largest weight-points are selected as the reference Bragg reflections pc1 and pc2.
It is another object of the invention to provide a novel method and apparatus that are free of the foregoing problems with the prior art technique and are capable of automatically selecting Bragg reflections and of determining the crystallographic orientation of a crystal sample automatically and easily.
This method and system use a computer for performing various calculations and a four-axis goniometer system for performing various measurements according to the results of calculations made by the computer. First, x-ray intensities and diffraction conditions, i.e., 2&thgr;-angles, &ohgr;-angles, &khgr;-angles, and &phgr;-angles, of all Bragg reflections which are measurable are calculated using crystallographic information such as space groups, lattice constants and atomic positions. Next, a weight-point is obtained and assigned to each of the Bragg reflections according to both its x-ray intensity and its angle &Dgr;G between the sample normal and its scattering vector, and the two Bragg reflections having the first and second largest weights are selected as the reference Bragg reflections pc1 and pc2, respectively. Thereafter, the four-axis goniometer system searches a
Harada Jimpei
Yokoyama Ryoichi
Bruce David V.
Rigaku Corporation
Wenderoth , Lind & Ponack, L.L.P.
LandOfFree
Method and apparatus of automatically selecting bragg... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and apparatus of automatically selecting bragg..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and apparatus of automatically selecting bragg... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2460789