Adhesive bonding and miscellaneous chemical manufacture – Differential fluid etching apparatus – For liquid etchant
Reexamination Certificate
1999-11-05
2002-12-17
Mills, Gregory (Department: 1763)
Adhesive bonding and miscellaneous chemical manufacture
Differential fluid etching apparatus
For liquid etchant
C451S285000, C438S690000, C216S088000
Reexamination Certificate
active
06494985
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method and apparatus for polishing a substrate, and more particularly to a method and apparatus for polishing a substrate such as a semiconductor wafer, a glass substrate, or a liquid crystal display to a flat mirror finish, and then cleaning a polished substrate that requires a high degree of cleanliness.
2. Description of the Related Art
As semiconductor devices have become more highly integrated in recently years, circuit interconnections on semiconductor substrates become finer and the distances between those circuit interconnections have become smaller. One of the processes available for forming such circuit interconnections is photolithography. Though the photolithographic process can form interconnections that are at most 0.5 &mgr;m wide, it requires that surfaces on which pattern images are to be focused by a stepper be as flat as possible because the depth of focus of the optical system is relatively small.
Further, if a particle greater than the distance between interconnections exists on a semiconductor substrate, then the particle will short-circuit interconnections on the semiconductor substrate. Therefore, any undesirable particles on the semiconductor substrate have to be sufficiently smaller than the distance between interconnections on the semiconductor substrate.
Therefore, in processing the semiconductor substrate, it is important to planarize the semiconductor substrate and clean the semiconductor substrate to a high degree of cleanliness. Such a requirement holds true for the processing of other substrates including a glass substrate to be used as a mask, a liquid crystal panel, and so on.
In order to achieve planarization of the semiconductor substrate, it has heretofore been customary to use a polishing apparatus, the process of which is called chemical-mechanical polishing (CMP). As shown in
FIGS. 10 and 11
, a conventional polishing apparatus comprises a polishing section
10
, a load and unload section
22
, two transfer robots
24
a
and
24
b,
a cleaning section
26
having three cleaning units
26
a,
26
b
and
26
c,
and a reversing device
28
as necessary. The transfer robots
24
a
and
24
b
may be a mobile type robot which moves along rails shown in
FIG. 10
, or a stationary type robot having robot hands at forward ends of articulated arms shown in FIG.
11
.
As shown in
FIG. 12
, the polishing section
10
comprises a turntable
12
having a polishing cloth
11
thereon, a top ring
13
for supporting a semiconductor wafer (substrate) W and pressing the semiconductor substrate W against the turntable
12
, and a nozzle
14
for supplying an abrasive liquid onto the polishing cloth
11
. A transfer device
38
is disposed adjacent to the turntable
12
(FIGS.
10
and
11
). The adjacent two sections are partitioned by a partition wall to prevent cross-contamination. Specifically, in order to prevent dirty atmosphere in the polishing section
10
from being scattered into a chamber in which a cleaning process and a subsequent process are performed, air conditioning and pressure regulation in each of the chambers are performed.
In the polishing apparatus having the above structure, the semiconductor substrate W is transported from the load and unload section
22
to the transfer device
38
by the transfer robots
24
a
and
24
b
and transferred to the top ring
13
by the transfer device
38
. In the polishing section
10
, the semiconductor substrate W is held by the lower surface of the top ring
13
and pressed against the polishing cloth
11
providing a polishing surface on the turntable
12
. The abrasive liquid Q is supplied from the nozzle
14
onto the polishing cloth
11
and retained on the polishing cloth
11
. During operation, the top ring
13
exerts a certain pressure on the turntable
12
, and the surface of the semiconductor substrate W held against the polishing cloth
11
is therefore polished in the presence of the abrasive liquid Q between the surface of the semiconductor substrate W and the polishing surface on the polishing cloth
11
by a combination of chemical polishing and mechanical polishing while the top ring
13
and the turntable
12
are rotated. In case of polishing an insulating layer made of an oxide film (SiO
2
) on the silicon substrate, the abrasive liquid Q contains abrasive particles having a certain diameter suspended in an alkali solution. The semiconductor substrate W which has been polished is transported to the cleaning section
26
in which the semiconductor substrate W is cleaned and dried, and then returned to the load and unload section
22
.
The primary cleaning unit
26
a
in the cleaning section
26
has a plurality of vertical spindles
30
arranged at spaced intervals for supporting the outer circumferential edge of the semiconductor substrate W by their holding grooves formed at the upper end portions of the spindles
30
and rotating the semiconductor substrate in a horizontal plane at a relatively low rotational speed, and a pair of cleaning members comprising a roller type or a pencil type sponge which can be brought in contact with the semiconductor substrate W or out of contact with the semiconductor substrate W. The primary cleaning unit
26
a
is a low rotational speed type cleaning unit. The secondary and tertiary cleaning units
26
b
and
26
c
have a rotating table
36
comprising a rotating shaft
32
and a plurality of arms
34
which extend radially outwardly from the rotating shaft
32
and hold the outer circumferential edge of the semiconductor substrate W. The secondary and tertiary cleaning units
26
b
and
26
c
are a high rotational speed type cleaning unit. In each of the primary, secondary and tertiary cleaning units
26
a,
26
b
and
26
c,
there are provided a nozzle for supplying a cleaning liquid to the surface of the semiconductor substrate W, a cover for preventing the cleaning liquid from being scattered around, and a ventilating equipment for creating down draft (descending air current) to prevent mist from being scattered around.
The cleaning processes for cleaning the semiconductor substrate which has been polished are carried out in the following manner:
In the primary cleaning unit
26
a,
while the semiconductor substrate W is held and rotated by the spindles
30
, a scrubbing cleaning is performed by allowing the cleaning members to scrub the upper and lower surfaces of the semiconductor substrate W while supplying a cleaning liquid. In this scrubbing cleaning process, the first cleaning liquid having substantially the same pH as the abrasive liquid used in the polishing process is used to prevent particles from being aggregated due to so-called pH shock. To be more specific, if the abrasive liquid is rapidly diluted with pure water to lower the pH of the abrasive liquid, then the abrasive particles become unstable, to thus aggregate secondary particles to form larger aggregates. In this specification, pH shock is defined as a rapid change of a pH. Therefore, in order to prevent pH shock from occurring, the first cleaning liquid having substantially the same pH as the abrasive liquid is used in the scrubbing cleaning process. For example, in case of polishing a SiO
2
layer, aqueous ammonia is used as the first cleaning liquid, and after the particles are removed from the surfaces of the semiconductor substrate W, the surfaces of the semiconductor substrate are shifted from alkali to neutrality by supplying a neutral cleaning liquid such as pure water thereto. Thereafter, the semiconductor substrate W is transferred to the secondary cleaning unit
26
b.
In the secondary cleaning unit
26
b,
in order to remove metal ions attached to the semiconductor substrate W, an acid chemical is normally supplied to the surfaces of the semiconductor substrate W from the nozzle to cause etching (chemical cleaning) of the surfaces of the semiconductor substrate, and then a neutral cleaning liquid such as pure water is supplied to cause the surfaces of the semiconducto
Ato Koji
Sotozaki Hiroshi
Ebara Corporation
MacArthur Sylvia R.
Mills Gregory
Wenderoth, Lind & Ponack L L P
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