Adhesive bonding and miscellaneous chemical manufacture – Differential fluid etching apparatus – With measuring – sensing – detection or process control means
Reexamination Certificate
2002-07-15
2004-05-11
Hassanzadeh, P. (Department: 1763)
Adhesive bonding and miscellaneous chemical manufacture
Differential fluid etching apparatus
With measuring, sensing, detection or process control means
C118S712000
Reexamination Certificate
active
06733619
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the semiconductor industry in general, and to an apparatus for monitoring wafers and process control in the semiconductor processing and a method for use thereof, in particular.
BACKGROUND OF THE INVENTION
The current trends of shrinking dimensions in the semiconductors industry and the dynamic nature of the processes involved in the semiconductor manufacturing, increase the need for accurate diagnostic tools, capable of providing real time measurements for short time to-respond feedback loops, such as closed loop control and feed forward control. Such stringent requirements cannot be obtained by off-line (“stand alone”) measuring systems, which do not provide a real time response. Inspection and measuring by such systems, however precise and accurate they are, slow-down the manufacturing process and consume valuable time and clean room space. On the other hand, in-situ detection devices such as end-point detection devices, which are used at different stages of the production line, although they provide real-time monitoring, their performance is not accurate enough. Such devices are exposed to the conditions in the active area of the production line, thus the data obtained by them is rather an averaging over a relatively large area and they cannot provide mapping capabilities.
This situation enhanced the development of a fundamental solution by means of integrated monitoring and process control, i.e., physical implementation of monitoring tools, with full metrology capabilities, within the production line in the semiconductor fabrication plant. (Dishon, G., Finarov, M., Kipper, R. (1997) Monitoring choices of CMP planarization process, 2
nd
International CMP planarization conference, February 13-14, Santa Clara, Calif.)
The terms “integrated apparatus” or “integrated device” as used in the present invention refers to an apparatus that is physically installed inside the processing equipment or is attached to it and is dedicated to a specific process. Wafers are transferred to said apparatus by the same robot which serves the processing equipment.
Integrated devices should be considered from several aspects and meet specific requirements in order to become real and feasible:
(a) Small footprint—an integrated device should have as small footprint as possible in order to be physically installed inside the Processing Equipment (hereinafter called PE), e.g., inside the Chemical Vapor Deposition (hereinafter called CVD) equipment, inside the Chemical Mechanical Polishing (hereinafter called CMP) polisher or inside the photocluster equipment;
(b) Separation of the measuring unit from the PE environment, e.g., using sealed enclosure. This is aimed at two objectives:
(I) Cleanliness—measuring unit must not interfere in any way with the operation of the PE or introduce any potential risk for contamination;
(II) To enable the application of certain conditions inside the integrated apparatus, such as pressurized gases in the CMP equipment (in order to prevent water vapor from penetrating the apparatus);
(c) Maintaining a stationary wafer during measurement in order to minimize system's footprint and to exclude extra wafer handling;
(d) High speed measuring unit (e.g., fast positioning, autofocusing and measurement);
(e) Means to directly respond to a certain cause with the correct straightforward correction action.
(f) Easy and quick maintenance by simple replacement of each functioning unit (component).
(g) Having the option to be bypassed by the production process and to operate at off-line mode.
In addition to the aforementioned specific design requirements, integrated device should have other general functions as described hereinafter.
Reference is made to
FIG. 1
, prior art, which generally illustrates an integrated apparatus which measures the thickness of thin films on the surface of a silicon wafer (the metrology device known as Integrated Thickness Monitoring system—ITM NovaScan 210, commercially available from Nova measuring instruments Ltd., Rehovot, Israel). The prior art will be described using this metrology device. In general, the known metrology apparatus of
FIG. 1
comprises an optical measurement unit (MU)
1
, an external light source
10
and a control unit (CU)
2
, which controls the movement and image acquisition of the optical measurement system
1
as well as the operation of the external light source
10
. The optical measurement system ‘sees’ the wafer through an optical window
3
.
Optical measurement system
1
typically comprises an optical unit
4
, whose optical path is shown in detail in
FIG. 2
, a translation system
5
capable of allocating measurement at any point on the wafer w, such as an X-Y stage, and data and image processing unit
6
forming part of the control unit
2
.
The optical path for the exemplary apparatus is illustrated in FIG.
2
and is described hereinafter. The optical unit comprises an external (to the MU
1
) white light source
10
, an optic fiber
11
, a condenser
12
, which directs the light onto a beam splitter
13
, a focusing target
25
, a tube lens
14
, a translatable objective
15
, an optical window
3
and the wafer's plan w. Behind the beam splitter
13
are located a pinhole mirror
16
, a relay lens
17
and a CCD camera
18
. Behind the pinhole mirror
16
there is another relay lens
19
, a mirror
20
and a spectrophotometer
21
. For the apparatus described here, only the objective
15
is translated, parallel to the wafer's plan w.
A light beam
22
emanates from the external light source
10
, is conveyed to the MU
1
by fiber optic
11
. It enters the MU
1
, to the condenser
12
till beam splitter
13
which deflects it toward the wafer w, via lenses
14
and
15
(mirrors which serve as well to convey light beam
22
are not shown) The reflected light beam (not labeled) is transmitted by lenses
14
and
15
, passes through beam splitter
13
and is deflected by pinhole mirror
16
to the CCD camera
18
where the image acquisition takes place. The portion of the light beam, which passes through the pinhole in the pinhole mirror
16
, reaches the spectrophotometer
21
. The focusing target
25
is any high contrast object, such as a metallic pattern on a glass substrate. The pattern can be any easily identifiable pattern, such as a contrast edge, a grid, etc.
The main two functions of the optical unit
4
are the positioning (including focusing, image acquisition and image processing) channel
100
and the measuring (including illumination and detection) channel
200
. The positioning channel
100
is aimed at identifying the exact location of the wafer w and the specific sites on the wafer w where measurements have to be done. Autofocusing using, among other things, focusing target
25
, is performed according to any method known in the art. Such a method based on the patterned features on the wafers is disclosed in U.S. Pat. No. 5,604,344. After the positioning and autofocusing are done, the objective
15
is located above the predetermined location on the wafer w. Now, a measurement is conducted by the measuring channel
200
. It should be noted that the positioning channel
100
and the measuring channel
200
are partly composed of the same optical elements as shown in
FIG. 2
, especially with respect to the moving optical head which is the objective
15
in this case. This overlap is feasible, mainly because both channels
100
and
200
in the ITM NovaScan 210 use almost the same spectral range. A direct result of this situation is that single optical window
3
is capable to serve both channels.
However, another situation is when an integrated measurement device uses different wavelengths for the positioning channel and for the measuring channel, or when optical measurements are required at more than one spectral range. For example, a method for layer composition measurements and contamination analysis during the CVD process is conducted by infrared optical assembly which cannot be used for the positioning channel
100
.
T
Dekel Patent Ltd.
Hassanzadeh P.
Klein David
Moore Karla
Nova Measuring Instruments Ltd.
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