Method and system for semiconductor wafer fabrication...

Details Method and system for semiconductor wafer fabrication... Method and system for semiconductor wafer fabrication...

1998-12-29

2002-03-26

Grant, William (Department: 2121)

Data processing: generic control systems or specific application

Specific application, apparatus or process

Product assembly or manufacturing

C700S117000, C438S005000, C438S800000

Reexamination Certificate

active

06363294

ABSTRACT:

FIELD OF INVENTION
The present invention relates generally to the manufacture of semiconductor integrated circuits and more particularly to a method and a system for real-time in-situ interactive supervision of the semiconductor wafer fabrication process. In a dedicated tool controlled by a computer, a method is developed which includes the steps of monitoring in real-time in-situ a plurality of process parameters in parallel by an end-point controller. Analysis rules are developed to perform a comparison and associated rejection criteria are coded in the form of algorithms and likewise stored in a database. If a process deviation is detected, an alert code is flagged to signal an alarm and the adequate action is immediately taken and these data stored in the database may be used to up-date the operating conditions of a step before it takes place.
BACKGROUND OF THE INVENTION
Due to the constant integration density increase, the fabrication processes that are used to date in the manufacture of semiconductor wafers for the production of integrated circuits (ICs) have to be very accurately controlled. For this reason, processing tools which are required to that end, are becoming more and more complex. A processing tool can include a plurality of chambers, and in turn, each chamber can run a great number of processing steps. For money saving and high throughputs, the wafer is generally processed in sequence via said plurality of chambers of the tool under computer control. The selection of the chamber depends on a number of factors such as: availability, contamination level, specialization, . . . etc.
New methods for tool and process characterization such as in-situ contamination monitoring, measurements, gas analysis and the like, are now of common use in the semiconductor industry. All these characterization techniques produce huge quantity of data of various types. In particular such data include the physical process parameters such as: gas flows, pressures, RF powers, temperatures, and the like, that are permanently under computer control during a determined step. Other data include results provided by controllers (e.g. etch rates) which continuously monitor the process and by measurement units.
FIG. 1
schematically shows a conventional system of the prior art referenced
10
that implements a typical process flow for processing semiconductor wafers. The description which follows will be made by reference to a multi-chamber RIE tool such as the AME 5000 manufactured by Applied Materials, Santa Clara, Calif., USA, that is adapted to perform a sequence of steps for etching different materials at the surface of the wafer. However, other tools such as deposition equipments and the like may be envisioned as well. Now turning to
FIG. 1
, system
10
is thus comprised of such a RIE etching tool
11
with a tool computer
12
associated thereto. As apparent from
FIG. 1
, tool
11
is only comprised of two chambers
11
-
1
and
11
-
2
for sake of simplicity, but in reality, it must be understood that it may have more, for instance, up to six independent chambers. Still for sake of simplicity, we will assume that each chamber performs the same sequence of processing steps, labelled A, B, . . . , I, . . . , X. A data bus referenced
13
provides the electrical connection between the tool chambers and the computer
12
for data flow exchange therebetween.
At initialization, computer
12
down-loads the physical process parameters of step A into chamber
11
-
1
or
11
-
2
as appropriate. Typical physical process parameters are gas flows, pressures, RF powers, temperatures and the like. Then, step A is performed and is generally stopped after a fixed time. This procedure applies for the other steps B, C, . . . X, whenever necessary. During these steps, computer
12
checks the different physical process parameters via data bus
12
for process control and only stops the current process if one of them passes beyond a predefined limit. A stop generally occurs after a serious hardware failure such as a RF power shut-down or a gas flow missing.
FIG. 2
describes an improved version of the system depicted in
FIG. 1
now referenced
10
′, the same elements bearing the same references. For sake of illustration, only three (A to C) and one (A) processing steps are performed in chambers
11
-
1
and
11
-
2
respectively. In addition to the tool
11
, the computer
12
and the data bus
13
connected therebetween, the improved system
10
′ includes additional equipments associated to each tool chamber. As apparent in
FIG. 2
, two etch end-point detection (EPD) controllers
14
-
1
and
14
-
2
are provided with optical fibers
15
-
1
and
15
-
2
to view the plasma inside chambers
11
-
1
and
11
-
2
respectively. The role of these EPD controllers is only to perform optical/interferometric measurements. An adequate EPD controller that can be used in system
10
′ is the DIGISEM or DIGITWIN sold by SOFIE Instr., Arpajon, FRANCE. However, in the present application, “EPD” denotes either “etch end point detection” or more generally “end point detection”, for instance, if a deposition process is used instead of an etch process. Likewise, two control devices
16
-
1
and
16
-
2
, typically particle counters, gas detectors, mass spectrometers and the like are associated to chambers
11
-
1
and
11
-
2
respectively. The nature of these control devices depends on the function: etching, deposition, . . . of the tool in consideration. Control devices are used by the operators for visual inspection of the on-going process, so that they may stop it in case of need, for instance, if a contamination in excess is detected by a particle counter. Finally, two measurement units
17
-
1
and
17
-
2
are necessary for intermediate and post-processing measurements to determine whether or not the wafer is still within the specifications at the output of each chamber. Note that, in some cases, measurement units
17
-
1
and
17
-
2
can designate a single and same unit
17
. As apparent in
FIG. 2
, these measurement are respectively performed at the output of chambers
11
-
1
and
11
-
2
. Measurement units and control devices are generally provided with a local database to record the main events for subsequent review by the operators at the end of the process. Data bus
18
provides the necessary electrical connection between the computer
12
and the EPD controllers
14
-
1
and
14
-
2
for an elementary data exchange. As a matter of fact, the role of EPD controllers is only to signal that the etch end point has been detected or if not, that the processing step hag reached the maximum allowed time for that determined step.
The operation of system
10
′ is relatively simple. Let us assume that for sake of simplicity, that (1) only three steps labelled A to C are performed in the first chamber
11
-
1
with only two steps (A and C) monitored by EPD controller
14
-
1
and (2) only one step (A) is performed in chamber
11
-
2
. First, computer
12
down-loads physical process parameters to chamber
11
-
1
via data bus
13
the way described above, and in the meantime, the identification number of the algorithm to be used in step A is sent to EPD controller
14
-
1
via bus
18
. Starting step A in chamber
11
-
1
also starts the EPD controller
14
-
1
scanning of the selected etch end point parameter, typically a specific radiation wavelength that is emitted by a determined layer at the surface of the wafer. A surge in the signal representing this emission indicates that the end point has been reached. However, other parameters can be used as well. The signal transmitted via optic fiber
15
-
1
is processed in EPD controller
14
-
1
to detect the etch end point. In that case, a signal is emitted by EPD controller
14
-
1
via data bus
18
to inform computer
12
that the etch end point has been reached and that step A must be stopped. In the contrary, EPD controller
14
-
1
informs computer
12
that the maximum allowed time has been reached. Next, step B is initiated. The

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