Radiant energy – Inspection of solids or liquids by charged particles – Analyte supports
Reexamination Certificate
2002-08-05
2004-07-13
Lee, John D. (Department: 2881)
Radiant energy
Inspection of solids or liquids by charged particles
Analyte supports
C250S440110, C250S441110, C250S492300, C250S458100, C250S492210, C250S492220, C204S298250, C315S111810, C474S035000, C474S037000, C474S133000, C474S161000
Reexamination Certificate
active
06762417
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an assembly for tilting a wafer platen of an ion implanter for manufacturing semiconductor devices. More particularly, the present invention relates to the connection between a rotating body and a shaft of a transmission mechanism for transmitting a drive force to the wafer platen.
2. Description of the Related Art
Ion implantation is a semiconductor manufacturing technique in which impurities are ionized, accelerated, and implanted into a desired area of a semiconductor substrate. Furthermore, ion implantation allows the impurities to be selectively implanted with accurate control. In addition, ion implantation can be performed with excellent process reproducibility and process uniformity. Therefore, the ion implantation process lends itself well to the mass-production of highly integrated semiconductor devices. Accordingly, the role of ion implantation in the semiconductor manufacturing process is continuing to gain in importance.
For maximum efficacy of the implantation process, it is known that a semiconductor wafer should be oriented at a predetermined angle relative to the ion beam. However, the wafer may be supported unstably while being tilted. Facility inspections have uncovered problems in the attachment of a drive shaft to a rotating arm controlling the Y-axis tilt of the wafer, and the attachment of a rotary shaft to a pulley controlling the X-axis tilt of the wafer. When these problems exist, the impurities are implanted to different depths in various portions of the wafer instead of being implanted to a uniform depth. Thus, these problems adversely affect the reliability of the facilities and the productivity of the manufacturing process.
The orienting of a wafer platen of the ion implanter will now be briefly described with reference to FIG.
5
. The wafer platen
75
can be moved in the direction of arrows A″ for controlling the X-axis tilt and in the direction of arrows B′ for controlling the Y-axis tilt.
FIG. 1
illustrates a connecting system for controlling the Y-axis tilt of a wafer platen in an implanter according to the prior art. Referring to
FIG. 1
, the connecting system includes a drive shaft
6
, a rotating arm
10
, ferrules
8
, a bracket
14
, and screws
12
. The drive shaft
6
is rotated by a drive motor
2
. Reference numeral
4
designates a plate to which the motor
2
is fixed. The rotating arm
10
is engaged with the drive shaft
6
so as to be rotated by the same. The ferrules
8
are positioned between the rotating arm
10
and the drive shaft
6
. The bracket
14
tightens the ferrules
8
and holds the drive shaft
6
. The screws
12
fix the bracket
14
onto the side of the rotating arm
10
.
The ferrules
8
have alternating flat and angled outer edges, and are disposed on the outside of the drive shaft
6
. Because the bracket
14
is fixed on the rotating arm
10
, the ferrules
8
transmit the rotary force of the drive shaft
6
to the rotating arm
10
. However, the ferrules
8
slip relative to the drive shaft
6
because both the drive shaft
6
and the ferrules
8
are made of steel. The rotation of the drive shaft
6
is thus not completely transmitted to the rotating arm
10
, and the wafer platen (not shown) is oriented inaccurately by the rotating arm
10
.
FIG. 2
is a graph showing encoder values and surface resistance values of a drive motor for controlling Y-axis tilt, by date, using the connecting system shown in FIG.
1
. Reference numerals
21
through
23
designate plots showing the distribution of the surface resistance values against the angle of the ion beam for finding the encoder values of the drive motor corresponding to the zero point of the Y-axis tilt. Reference numerals
31
through
33
designate plots showing the distribution of the surface resistance values against the angle of the ion beam when the drive motor was operated under encoder values corresponding to the zero point of the Y-axis tilt. Reference numerals
41
through
43
designate plots showing the distribution of the surface resistance values against the angle of the ion beam for finding the encoder values of the drive motor corresponding to the zero point of the Y-axis tilt, after the drive motor had been operated for a certain period of time.
First, on April 2
nd
, an encoder value −64.61 mm of the drive motor was finally obtained through first (
21
), second (
22
), and third tests (
23
) in order to establish the zero point of the Y-axis tilt. The absolute value of the surface resistance at an angle of −1° of the ion beam is similar to the absolute value of the surface resistance at an angle of +1° of the ion beam on the plot
23
, yielding encoder values suitable to set the zero point. Here, the surface resistance values are symmetrical about the angle of 0° of the ion beam.
On April 30, the surface resistance values at an angle of −1-+1° of the ion beam were compared through first (
31
), second (
32
), and third tests (
33
) after the encoder value of the drive motor, in which the zero point had been set, was set to −64.61 mm. However, as the tests, showed, the absolute values of the surface resistance were not symmetrical about the angle of 0° of the ion beam. Thus, the angle of the ion beam was determined to vary even though the drive motor was operated by the same encoder values.
On May 4
th
, encoder values of the drive motor were obtained through first (
41
), second (
42
), and third tests (
43
) when the absolute values of the surface resistance were symmetrical about the angle of 0° of the ion beam. The encoder values of the drive motor obtained through these tests were −65.85 mm, −65.05 mm, and −65.15 mm, which are different from the encoder value −64.61 mm of the drive motor in which the zero point was first set. Thus, it was apparent that the connection between the drive shaft and the rotating arm in the system for controlling the Y-axis tilt was creating a problem.
FIGS. 3 and 4
illustrate a drive system for controlling the X-axis tilt in an ion implanter according to the prior art. Referring to these figures, the drive system includes rotary shafts
53
and
59
, drive and follower pulleys
51
and
57
, a belt
65
wrapped around the pulleys
51
and
57
, spacers
63
and
73
spacing the shafts
53
and
59
from the pulleys
51
and
57
, respectively, and nuts
61
and
71
for tightening the spacers
63
and
73
. Reference numeral
67
designates a boss of the follower pulley
57
.
The rotary output of a drive motor is transmitted to the follower pulley
57
by the belt
65
. The rotary force of the follower pulley
57
is, in turn, transmitted to the rotary shaft
59
connected to the follower pulley
57
by the nut
61
. The shaft
59
rotates a wafer platen connecter
69
for controlling the X-axis tilt (angle of the wafer platen). In this drive system, the follower pulley
57
will slip relative to the shaft
59
if the nut
61
becomes loose. Also, slip occurs between the shaft
59
and the spacer
63
because both the shaft
59
and the spacer
63
are made of steel. Accordingly, the drive shaft
53
does not completely transmit its rotary force to the shaft
59
. Thus, the angle of the wafer platen (not shown) is set inaccurately by the shaft
59
.
SUMMARY OF THE INVENTION
An object of the present invention is to solve the above-described problems. More specifically, an object of the present invention is to provide a mechanism in which a rotating body and a rotary shaft are connected in a tilt assembly of an ion implanter such that the orientation or tilt of a wafer platen can be accurately controlled with respect to the ion beam.
To achieve the above object, according to a first aspect of the present invention, the rotary shaft has a key way extending parallel to the longitudinal axis of the shaft and at least one internally threaded hole in an end surface thereof. The rotating body has a boss defining a protrusion, and a plurality of internally
Jang Jin-Hyeung
Kim Hak-Young
Lee John D.
Samsung Electronics Co,. Ltd.
Vanore David A.
Volentine & Francos, PLLC
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