Chemical mechanical polishing apparatus

Details Chemical mechanical polishing apparatus Chemical mechanical polishing apparatus

2000-03-10

2002-01-29

Hail, III, Joseph J. (Department: 3723)

Abrading

Precision device or process - or with condition responsive...

By optical sensor

C451S041000, C451S283000

Reexamination Certificate

active

06341995

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to an apparatus of chemical mechanical polishing (CMP), and more particularly to, an improved apparatus of chemical mechanical polishing, which reduces air sharp pressure on the polish head for preventing the breakage of unpolished wafers.
2. Description of the Prior Art
Chemical mechanical polishing (CMP) is the only technology, which can provide a total planarization for ULSI process. This technology comes from IBM company and has been developed through many decades, and been already applied on many products, such as central processing unit (CPU). The philosophy is the planarization technique that uses a “knife grinder” like mechanical polishing method and in accompanies with a proper chemical reagent to planarize the rough sketch on wafer surface. Once all parameters are controlled well, chemical mechanical polishing can offer a smooth degree of more than 94%. Therefore, semiconductor manufacturers and the suppliers of facilities and chemicals all over the world are continually investing the development of CMP technology.
Referring to
FIG. 1
, which indicates a partial structural drawing the conventional traditional chemical mechanical polishing apparatus
10
which is composed of a wafer head
110
, and a polish head
120
. Wafer head
110
includes a wafer air inlet
112
, a carrier firm
114
and a wear ring
116
. Polish head
120
includes a polish air inlet
122
, a polish air outlet
124
, a pad air inlet
126
and a slurry diaphragm
128
. When an unpolished wafer
118
is placed on the wafer head
110
, the carrier firm
114
is put smoothly on the unpolished wafer
118
, which is composed of high molecule polymerization, for example, plastic, rubber . . . etc, and then pouring in air from the wafer air inlet
112
. The air pressure on the wafer head
110
is P
wafer
, which is being pressed uniformly on the unpolished wafer
118
through the carrier firm
114
, and the function of the wear ring
116
is to prevent the unpolished wafer
118
from slipping out from the wafer head
110
to break. Then, to pour air into the wafer air inlet
122
and the air will press uniformly on the slurry diaphragm
128
, which is composed of high molecule polymerization, such as plastic, rubber . . . etc, and then leave from the polish air outlet
124
. The air pressure on polish head
120
is P
polish
. Especially to take notice on the difference between P
wafer
and P
polish
, which should be negative (it means &Dgr;P=P
wafer
−P
polish
<0). By means of letting P
polish
to be greater than P
wafer
unpolished wafer
118
can stick on the carrier firm
114
to process polishing. When the difference is positive (It means &Dgr;P=P
wafer
−P
polish
>0), the unpolished wafer
118
can't stick on the carrier firm
114
, and the unpolished wafer
118
will slip out the wear ring
116
and break. Besides, when polishing pad directly polishes the surface of the unpolished wafer
118
, not only the slurry diaphragm
128
will release slurry to increase efficiently, but also the pad air inlet
126
will pour in air to maintain the system operation balance.
A partial air pressure regulation system is illustrated in FIG.
2
. When air goes into the polish head
120
(through an air supply line
132
), it needs to pass a regulator E/P first. Because the air pressure controlling system (not shown in Figure) must change way to send signal from digital to analog through this regulator and to adjust air pressure from the polish head
120
. When the air leave the polish head
120
through another air line
134
, it needs to pass a second polish pressure transducer P/I
138
, which functions to change signal from analog to digital and to send back to air pressure control system. It owes to adjust air pressure through the wafer head
120
.
But when pouring air to process chemical mechanical polishing, no matter the wafer air inlet
112
, the polish air inlet
122
or the pad air inlet
126
, the air pressure curves will all be the one illustrated in FIG.
3
. The curve first show some time a sharp pressure, and gradually become air pressure steady state. In sharp pressure condition, due to the curve range of air pressure is huge:
(1) When P
wafer
on the top point of the sharp pressure, and P
polish
is on the low point, it will increase the probability of &Dgr;P=P
wafer
−P
polish
>0, and the unpolished wafer
118
will slip out the wear ring
116
and break.
(2) When the pressure difference between P
wafer
and P
polish
is too huge, it will cause slurry diaphragm
128
to break. In polishing process, slurry flows into the polish air inlet
122
/outlet
124
from break and flows through the air supply line
132
,
134
to the first regulator E/P
136
, the second regulator E/P
138
. It will make the real air pressure not be detected, and will send out a wrong signal to the air pressure control system. It will cause error on adjustment of air pressure, &Dgr;P=P
wafer
−P
polish
>0, and make unpolished wafer
118
slip out the wear ring
116
and break.
SUMMARY OF THE INVENTION
In accordance with the present invention, an improved chemical mechanical polishing apparatus is provided for processing chemical mechanical polishing that substantially overcomes drawbacks of above mentioned problems aroused form the conventional methods.
Accordingly, it is an object of the present invention to provide an improved chemical mechanical polishing apparatus which can reduce the sharp pressure and the probability of &Dgr;P=P
wafer
−P
Polish.
>0.
Another object of the present invention is to provide an improved chemical mechanical polishing apparatus that can detect whether slurry flows from the broken point of diaphragm to air supply line or not.
This invention is related to an improved chemical mechanical polishing apparatus, which is composed of a wafer head, a polish head, a damper and a sensor. The flowing speed of gas is reduced by making the diameter of the gas line connected to the damper air inlet smaller than the diameter of the gas line connected to the damper air outlet. The initial air sharp pressure is reduced and make &Dgr;P=P
wafer
−P
polish
<0, by adding an air temporary storage machine in between the inlet and the outlet. It means that an unpolished wafer can stick on the carrier firm and won't slip out to break when polishing. Besides, putting a sensor on the air lines under the air temporary storage machine, when slurry flows in the air line owing to the breaking of slurry diaphragm, the sensor will send a signal to a control system of the improved apparatus of chemical mechanical polishing, and make the related parts stop operating automatically to avoid breaking.


REFERENCES:
patent: 6042455 (2000-03-01), Togawa et al.
patent: 6159073 (2000-12-01), Wiswesser et al.
patent: 6190234 (2001-02-01), Swedek et al.
patent: 6196904 (2001-03-01), Matsuo et al.

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