Method of mixing slurries

Details Method of mixing slurries Method of mixing slurries

1998-12-24

2001-08-28

Soohoo, Tony G. (Department: 1723)

Agitating

Method

C366S263000, C451S061000

Reexamination Certificate

active

06280079

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to chemical mechanical polishing (CMP) polisher and more particularly to a slurry mixing apparatus for the CMP polisher.
2. Description of the Related Art
Planarization is an important technology in semiconductor process. The surface of the wafer has an even topography after planarization and it is able to prevent exposure light source from being scattered, so that the pattern transfer can be carried out precisely. Planarization technology mainly includes two methods, spin-on glass (SOG) and chemical mechanical polishing (CMP). SOG can not satisfy gradually the requirement of planarization as the semiconductor technique enters the field of sub-half-micron. CMP is the only process currently that can provide global planarization in very-large scale integration (VLSI) and ultra-large scale integration (ULSI).
CMP is a planarization process to planarize an uneven surface by applying mechanical polishing and adding suitable chemical reagent and slurry. When conditional parameters of process can be controlled appropriately, the planarization degree may reach 94% by CMP. Referring to FIG.
1
and
FIG. 2
, schematic top view and side view of a CMP polisher known in prior art are shown respectively. A holder
102
holds a backside
106
of a wafer
112
, and a front side
120
of the wafer
112
is facing a polish pad
114
on a polish table
100
. A slurry
110
from a slurry supplier
118
is pumped into a pipe
104
by a pump
116
, and thus, the slurry
110
can be supplied to the polish pad
114
continually. The chemical reagent in the slurry
110
is reacted with the front side
120
of the wafer
112
, and the polish table
100
and the holder
102
are rotated along directions
108
a,
108
b
to polish the wafer
112
mechanically by particles in the slurry
110
. Chemical reaction and mechanical polishing are repetitively applied on the wafer, and an even surface can be therefore obtained by the planarized process of CMP.
The quality of the slurry determines the stability of the process, so it is important in the planarized process of CMP. Chemical reaction and mechanical polishing are decided by chemical reagent and particles in the slurry respectively. The slurry needs to be diluted by solvent and then can be used, so that the slurry is varied from different materials and it is often necessary to use two kinds of slurry to planarized the wafer.
Since the slurry needs to be diluted to a suitable concentration, a premixer (not shown) is added in the slurry supplier
118
to mix slurry in advance. However, the property of the slurry is easily varied after being mixed. Thus, the slurry has to be consumed after being mixed and before reaching a Pot life. Due to the instability of the mixed slurry, another in-situ slurry mixing apparatus is developed due to the unstable property of the pre-mixed slurry.
Referring to
FIG. 3
, it shows a side view of an in-situ slurry mixing apparatus in prior art. The in-situ slurry mixing apparatus includes a pipe
202
, a pipe
204
(in order to simplify the illustration, only pipes
202
,
204
are shown in
FIG. 3
) and a slurry pipe
206
. Different slurries are pumped into the slurry pipe
206
through the direction shown as arrow
202
a,
204
a
from pipes
202
,
204
. The slurry in the slurry pipe
206
is directly provided onto the polished pad (such as
110
shown in
FIG. 2
) along the direction of the arrow
206
a.
However, the mixing time of the in-situ slurry mixing apparatus is too short to cause nonuniformity of the slurry, so that the quality of the slurry can not be easily controlled and result in worse performance of CMP.
SUMMARY OF THE INVENTION
It is therefore an object of the invention to provide a slurry mixing apparatus for the CMP polisher. The slurry mixing apparatus solves the problem of time-varying-property of the pre-mixing slurry.
It is another object of the invention to provide a slurry mixing apparatus for the CMP polisher. The slurry mixing apparatus solves the problem of nonuniform mixed slurry from the in-situ slurry mixing apparatus.
To achieve these objects and advantages, and in accordance with the purpose of the invention, as embodied and broadly described herein, the invention is directed towards a slurry mixing apparatus. The apparatus includes a mixing chamber, a rotatable bearing and several blades. The bearing is connected to the blades and installed in the mixing chamber. Several kinds of the slurries can be mixed rapidly in the apparatus and flowed into the CMP polisher immediately to perform a CMP process. The disadvantage of property of pre-mixing slurry being varied from time can be solved and the problem of nonuniform slurry due to in-situ slurry mixing can be overcome. The quality of the mixing slurry is thus improved.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention as claimed.


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