Two-slurry CMP polishing with different particle size abrasives

Details Two-slurry CMP polishing with different particle size abrasives Two-slurry CMP polishing with different particle size abrasives

1999-06-03

2001-05-08

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

Abrading

Abrading process

Combined abrading

C451S041000, C216S088000

Reexamination Certificate

active

06227949

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a chemical mechanical polishing process used in semiconductor fabrication, and more particularly, to a two-step chemical mechanical polishing process.
BACKGROUND OF THE INVENTION
During the manufacture of multilayer integrated circuits, it is desirable to effect planarization of the integrated circuit structures in the form of semiconductor wafers. This is usually accomplished by chemical mechanical polishing (CMP).
FIG. 1
shows a cross-sectional view of a conventional CMP apparatus
10
, which includes a rotating table
12
having a polishing pad
14
disposed thereon, and a wafer carrier
16
that holds a wafer
18
. The wafer
18
is held in an inverted position against the polishing pad
14
, with the side to be polished against the polishing pad. A predetermined pressure is exerted on the wafer
18
against the polishing pad
14
. As shown in
FIG. 2
, an enlarged cross-sectional view, a slurry
19
is applied between the wafer
18
and the polishing pad
14
. In operation, the polishing pad
14
and the wafer
18
rotate in relation to one another. The wafer is polished by mechanical abrasion from the polishing pad
14
and particles in the slurry
19
and by chemical action from the slurry
19
on the polishing pad
14
. Apparatus for polishing semiconductor wafers are well-known in the art. Such planarization apparatus are manufactured by IPEC Planar and SpeedFam Corporation among others.
In a typical CMP process, two polishing pads are used. The semiconductor wafer is first polished by using a hard pad on a primary rotating table. The hard pad increases the planarity of the wafer. The wafer is then polished by using a soft pad and a lower downward force on a secondary rotating table. The soft pad increases the uniformity of the wafer. During the CMP process, the CMP apparatus will generate, either chemically or mechanically, unwanted particles that degrade the performance of the circuits. When the wafer is transferred from the primary table to the secondary table, the slurry becomes dry and hard due to contact with the air. A cleaning step is required. The cleaning step may include scrubbing, rinsing and spin-drying. This cleaning step undesirably reduces production efficiency. Moreover, the transferring of the wafer between the primary table and the secondary table creates the potential for contamination of the clean environment necessary during wafer fabrication.
There are also several different types of slurries used in the CMP process. The most common abrasives used are silica (SiO
2
), alumina (Al
2
O
3
), ceria (CeO
2
), titania (TiO
2
), and zirconia (ZrO
2
). The abrasives are formed using two different methods that result in fumed and colloidal abrasives. Fumed abrasives tend to be chained particles that are larger in size than colloidal abrasives, which consist of discrete particles in a dispersion. For the same solids concentration, the removal rate using a fumed abrasive is higher than that using a colloidal abrasive due to larger particle size. For the same reason, the defect density using a fumed abrasive is also higher.
For this reason, the colloidal abrasive having a uniform particle size is preferred. However, to achieve the same removal rate as using a fumed abrasive, the solids concentration of a colloidal slurry must be almost three times higher. This increases the cost of the slurry.
Thus, what is needed is a method of CMP that has a low slurry cost, a high throughput rate, and a low defect rate.
SUMMARY OF THE INVENTION
A method for chemical mechanical polishing (CMP) of a wafer having a top layer to be polished, said CMP being performed on a CMP apparatus, is disclosed. The method comprises the steps of: using said CMP apparatus to polish said top layer using a first slurry having abrasive particles of a first size; and using said CMP apparatus to polish said top layer using a second slurry having abrasive particles of a second size, said second size being smaller than said first size.


REFERENCES:
patent: 5503592 (1996-04-01), Neumann
patent: 5571373 (1996-11-01), Krishna et al.
patent: 5676587 (1997-10-01), Landers et al.
patent: 5954997 (1999-09-01), Kaufman et al.
patent: 5961372 (1999-10-01), Shendon
patent: 5985755 (1999-11-01), Bajaj et al.
patent: 6062952 (2000-05-01), Robinson et al.

Affiliated with

Also associated with

Rating

Two-slurry CMP polishing with different particle size abrasives does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Two-slurry CMP polishing with different particle size abrasives, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Two-slurry CMP polishing with different particle size abrasives will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2534012