X-ray or gamma ray systems or devices – Specific application – Diffraction – reflection – or scattering analysis
Reexamination Certificate
2001-10-25
2004-07-06
Arana, Louis M. (Department: 2859)
X-ray or gamma ray systems or devices
Specific application
Diffraction, reflection, or scattering analysis
C378S070000
Reexamination Certificate
active
06760403
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to the manufacture of crystalline bodies, such as crystalline ingots, and, more particularly, to methods and apparatus for orienting a crystalline body during radiation diffractometry, such as for purposes of initially identifying the location at which an alignment feature, such as a flat or a notch, is to be formed or for thereafter verifying the location of the alignment feature.
BACKGROUND OF THE INVENTION
The crystalline bodies that are grown, generally in the form of crystalline ingots, during the process of manufacturing semiconductor wafers are crystalline structures. In this regard, the ingots have a predefined crystal orientation in the axial direction, such as an <100> axial orientation. During a number of subsequent manufacturing operations, the position of the ingot as well as the wafers that are subsequently formed from the ingot with respect to a target plane location, must be precisely determined. For example, other material layers must generally be grown, deposited or otherwise formed upon the wafer in a predetermined manner with respect to the target plane. As known to those skilled in the art, the target plane location is related to the axial orientation in that the relative positional relationship of a family of target planes are defined by the axial orientation. In other words, the axial orientation provides information relating to the angular spacing of a family of target planes, but does not dictate the particular location of any of the target planes. For example, wafers formed from an ingot having an <100> axial orientation will have a family of four {110} planes separated by 90° from one another; any one of which may serve as the target plane.
In order to facilitate proper positioning of the ingot or wafer during subsequent manufacturing operations, an alignment feature, such as a notch or a flat, is typically formed lengthwise along the ingot or more commonly along a block or segment of the ingot (hereinafter collectively referred to as an ingot). By directly identifying the location of the target plane with the alignment feature, subsequent manufacturing operations can be referenced to the alignment feature and, in turn, to the target plane. Alignment features are well known with a flat being typically formed to be parallel to the target plane. In contrast, a notch is typically formed such that a radial line that bisects the notch is perpendicular to the target plane.
In order to form the alignment feature in a desired location, the crystalline body is typically examined to identify the target plane location. Typically, the crystalline body is subjected to radiation, such as x-rays, at a variety of incidence angles. The reflected radiation is monitored and the position of the crystalline body at the time at which the intensity or power of the reflected radiation peaks is noted since the peak power or intensity is indicative of reflections from a crystalline plane, such as the crystalline plane that defines the target plane. Once the crystalline plane that defines the target plane has been identified, the alignment feature can be formed lengthwise along the ingot so as to identify the target plane as described above. Secondary alignment features may also be formed lengthwise along the ingot at other predetermined angular positions with respect to the initial or primary alignment features.
In order to identify the crystalline plane
10
that defines the target plane and, in turn, the proper position of the alignment feature
14
, the crystalline body
12
is typically placed upon a stage
16
and is illuminated by a radiation source
18
, as shown in FIG.
1
. The signals reflected or otherwise returning from the crystalline body are captured by a radiation detector
20
. While the crystalline body can be placed in various orientations upon the stage, the crystalline body is typically initially positioned upon the stage based upon habit lines that develop during the growth of the crystalline body and that are consistently located in a known manner with respect to the axial orientation. The crystalline body is then moved upon the stage to alter the angle of incidence of the radiation as the radiation source continues to direct radiation to the crystalline body and the radiation detector continues to detect the reflected radiation. For a substantially cylindrical ingot, for example, the ingot is rotated about its longitudinal axis to vary the angle of incidence. Upon detecting the peak of the reflected radiation, the position of the crystalline plane that defines the target plane is identified and the alignment feature is formed so as to directly identify the target plane. While a variety of devices have been developed for examining a crystalline body to determine the location of a target plane, x-ray diffractometers, such as those sold by Rigaku/USA, Inc. of The Woodlands, Tex., are commonly utilized.
After the alignment feature
14
has been formed, such as by grinding a flat or a notch, the crystalline body
12
is typically re-inspected to verify the position of the alignment feature relative to the target plane since the position of the alignment feature to the target plane is critical during subsequent manufacturing operations. This verification is typically performed by again placing the ingot
12
upon the stage
16
and irradiating the ingot. Based upon the alignment feature, the ingot is positioned upon the stage in such a manner that the crystal plane
10
that defines the target plane of the ingot will reflect the incident radiation, thereby maximizing the power or intensity of the reflected radiation. The radiation reflected or otherwise returning from the ingot is detected while the angle of incidence of the radiation is varied slightly, such as by rotating the stage and the ingot relative to the radiation source
18
and detector
20
. By determining the peak of the reflected radiation, the position of the target plane and, in turn, the position of the alignment feature relative to the target plane can be confirmed.
In order to facilitate positioning of the ingot
12
and, in particular, the alignment feature
14
of the ingot relative to the underlying stage
16
and, in turn, to the radiation source
18
and detector
20
, a fixture
22
is utilized to engage one end of the ingot and to maintain the ingot in a predefined position relative to the underlying stage. As shown in
FIG. 1
, a fixture generally includes an upstanding plate
24
having a base
26
for contacting a bar
28
that is mounted to and extends upwardly from the stage. The fixture also includes a pair of supports
30
, typically in the form of rollers, carried by the plate for engaging circumferential portions of the crystalline ingot. Additionally, the fixture includes an engagement member
32
threadably connected to the edge of the fixture opposite the base for engaging the alignment feature of the ingot. In this regard, the distal end of the engagement member can include a pin for engaging the bottom portion of a notch. Alternatively, the distal end of the engagement member can be planar for engaging a flat. As shown, a conventional fixture therefore engages the alignment feature of a crystalline ingot such that the alignment feature is positioned opposite the bar with the engagement member extending towards the bar in a perpendicular relationship thereto.
Once the end of the crystalline ingot
12
is engaged by the fixture
22
, the ingot is irradiated and the radiation reflected by or otherwise returning from the ingot is detected. The stage
16
is then rotated slightly, such as through an angle of about +/−0.5°, in order to vary the angle of incidence and to determine the position of the crystalline ingot that maximizes the reflected radiation. A conventional fixture, such as shown in
FIG. 1
, is therefore useful in conjunction with crystalline ingots having an alignment feature
14
that directly identifies the crystal plane
10
that defines the target plane by bei
Aydelott Richard M.
Secrest Mark E.
Arana Louis M.
SEH America Inc.
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