SOG dispensing system and its controlling sequences

Details SOG dispensing system and its controlling sequences SOG dispensing system and its controlling sequences

1999-04-28

2001-06-12

Crispino, Richard (Department: 1734)

Coating apparatus

Control means responsive to a randomly occurring sensed...

Responsive to attribute, absence or presence of work

C118S667000, C118S684000, C118S692000, C118S694000, C118S064000, C118S069000, C427S240000, C427S096400, C222S064000, C222S146100, C222S373000, C438S758000

Reexamination Certificate

active

06245148

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a SOG (Spin-On-Glass, hereinafter referred as SOG) dispensing system and its controlling sequences and, more particularly, to a SOG dispensing system allowing for continuous production and raising its operating efficient.
2. Description of the Prior Art
Before we start to introduce a SOG dispensing system of prior art, it is necessary to explain importance of SOG for a semiconductor device and its fabrication processes. It is well known that uneven (non-planar) surface topology of a wafer can cause undesirable effects and difficulties in the application of subsequent layers and fabrication processes such as pattern distortion after developing due to a focusing problem in a photolithography process, it becoming more serious at a recessed area because of insufficient exposure, Especially at a multilevel metallization structure, an interlevel dielectric (hereinafter referred as ILD ) is not only used as a dielectric layer but a planarizing layer to eliminate voids formed at gaps between metal conduction lines. During a photolithography process, if there are voids formed, photoresist would flow into these voids and thus the thickness of photoresist isn't thick enough to protect the ILD layer during etching process and causes a quality-controlled issue of ILD. Besides, it is hard to clear photoresist inside the voids and thus causes a wafer-contaminated problem so as to reduce production yield. In order to overcome said problem, SOG is dispensed to the wafer for planarizing its surface topology because SOG has a flowing characteristic like a photoresist to fully filling up gaps between metal conduction lines. The wafer is then baked so that organic solvent inside the SOG can be evaporated to make it transform from a fluidity to a solidity.
A SOG dispensing system of prior art, shown in
FIG. 1
, comprises a source tank
10
in which contains a SOG bottle
11
having a volume 500 cc, and a coating unit
20
. The reason why we use the SOG bottle is that life time of SOG chemical is maintained at a temperature between −1° C. and 4° C. and reduced to about 10 days at room temperature so that a SOG bottle is easy to be replaced when used up. Otherwise, a cooling unit is needed to provide low temperature and this is not ecnomical. The coating unit
20
comprises a valve V
1
and a valve V
2
conncected to the valve V
1
, wherein the valve V
1
is controlled by a timing circuit (not shown in
FIG. 1
) to dispense a certain amount of SOG to a wafer and the valve V
2
is controlled by a detector (not shown in
FIG. 1
) to suck back residual SOG at nozzle of its output pipe line. SOG is pushed by a high pressure of N
2
and transmitted from the SOC bottle
11
through the valve V
1
, the valve V
2
to nozzle of its output pipe line, finally dropping to the wafer W,as shown in FIG.
1
. According to practical situation of production line, about 100 cc-200 cc of SOC is left after finishing SOG coating of three lots of wafers (i.e. 150 wafers) and in order to avoid process discontinuity for a next lot of wafers due to insufficient SOC, the residue can't be used and the SOG bottle should be replaced. Thus, the SOG dispensing system must be idle when changing the SOG bottle
11
, thereby prolonging fabrication cycle time, as well as raising fabrication cost because of unused residue of the SOG bottle. Since in order to issure that there are no bubbles or particles in these dispensing lines, a dummy dispensing of a test running for particles and thickness confirmation is necessary after changing the SOG bottle, idle time of the SOG dispensing system is further prolonged and thus considerably lowers its operating efficient. Therefore, it is needed to propose a new SOG dispensing system allowing for continuous production, thereby raising its operating efficient and reducing fabrication cost by saving SOG waste .
SUMMARY OF INVENTION
It is therefore an object of the present invention to provide a new SOG dispensing system and its controlling sequences allowing for continuous production.
It is another object of the present invention to provide a new SOG dispensing system and its controlling sequences allowing for raising its operating efficient and reducing fabrication cost by saving SOG waste.
According to the present invention, a buffer tank, whose wall is set a plurality of level sensors at different level heights, is connected between a source tank with a SOG bottle inside and a coating unit of prior art and then SOG is supplied for a time interval from the source tank into the buffer tank by control signals from these level sensors. Besides, the buffer tank is surrounded with a cooling unit to provide a low temperature enviroment allowing for prolonging life time of SOG and preventing organic solvent inside SOG from evaporating and then crystallizing to form contamination particles at wall of the SOG dispensing system. Thus, the resultant SOG dispensing system, according to the present invention, can resolve a shortcoming of discontinuous production of prior art due to a need for changing the SOG bottle, as well as another shortcoming of residue of the SOG bottle, thereby considerably raising operating efficient of the dispensing system by reducing its idle time and lowering fabrication cost by saving a SOG waste.


REFERENCES:
patent: 4886012 (1989-12-01), Ikeno et al.
patent: 5433344 (1995-07-01), Fulton et al.
patent: 5857619 (1999-01-01), Huang et al.

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