Abrading – Abrading process – Abradant supplying
Reexamination Certificate
2000-11-29
2002-03-19
Hail, III, Joseph J. (Department: 3723)
Abrading
Abrading process
Abradant supplying
C451S446000, C451S036000, C210S096100, C210S416100
Reexamination Certificate
active
06358125
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a polishing liquid supply apparatus for use in a polishing unit for polishing a surface of a workpiece such as a semiconductor wafer, and more particularly to a polishing liquid supply apparatus which is capable of supplying a polishing liquid that stably contains an additive.
2. Description of the Related Art
Recent rapid progress in semiconductor device integration demands smaller and smaller wiring patterns or interconnections and also narrower spaces between interconnections which connect active areas. One of the processes available for forming such interconnection 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.
It is therefore necessary to make the surfaces of semiconductor wafers flat for photolithography. One customary way of flattening the surfaces of semiconductor wafers is to polish them with a polishing apparatus.
FIG. 5
of the accompanying drawings shows a conventional polishing unit. As shown in
FIG. 5
, the conventional polishing unit comprises a turntable
142
with a polishing cloth
140
attached to an upper surface thereof, a top ring
144
for holding a semiconductor wafer W which is a workpiece to be polished while rotating the semiconductor wafer W and pressing the semiconductor wafer W against the polishing cloth
140
, and a polishing liquid supply nozzle
146
for supplying a polishing liquid Q to the polishing cloth
140
. The top ring
144
is connected to a top ring drive shaft
148
, and vertically movably supported by an air cylinder (not shown).
The top ring
144
supports on its lower surface an elastic pad
150
made of polyurethane or the like. The semiconductor wafer W is held on the top ring
144
in intimate contact with the elastic pad
150
. The top ring
144
also has a cylindrical guide ring
152
mounted on a lower outer circumferential surface thereof for preventing the semiconductor wafer W from being dislodged from the lower surface of the top ring
144
while the semiconductor wafer W is being polished. The guide ring
152
is fixed to the top ring
144
, and has a lower end projecting downwardly beyond the lower holding surface of the top ring
144
to define a recess between the lower holding surface of the top ring
144
and the projecting lower end of the guide ring
152
for holding the semiconductor wafer W therein.
With the above structure, the semiconductor wafer W is held against the lower surface of the elastic pad
150
on the lower surface of the top ring
144
, and pressed against the polishing cloth
140
by the top ring
144
. The turntable
142
and the top ring
144
are rotated about their own axes to move the polishing cloth
140
and the semiconductor wafer W relatively to each other for thereby polishing the semiconductor wafer W. At this time, the polishing liquid Q is supplied from the polishing liquid supply nozzle
146
to the polishing cloth
140
. The polishing liquid Q comprises fine abrasive particles suspended in, for example, an alkaline solution. Therefore, the semiconductor wafer W is polished by a composite action of a chemical action of the alkaline solution and a mechanical action of the fine abrasive particles. Such a polishing process is referred to as chemical mechanical polishing (CMP).
In order to polish the semiconductor wafer W satisfactorily by the polishing apparatus, it is necessary that the polishing liquid having a constant concentration be supplied stably at a constant rate to the polishing unit. The polishing liquid is supplied from a polishing liquid supply system which includes a raw material tank for storing a raw material that comprises a mixture of KOH, NH
4
OH, or the like, and powder silica, and an adjustment tank for adjusting the raw material supplied from the raw material tank to a predetermined concentration by diluting the raw material with pure water or a chemical solution. The polishing liquid supply system further includes a supply tank for temporarily storing a polishing liquid adjusted by the adjustment tank and supplying the polishing liquid, and a polishing liquid supply piping system interconnecting the tanks for supplying the polishing liquid from the supply tank to the polishing liquid supply nozzle
146
in the abrasive unit.
The polishing liquid contains an additive such as an oxidizing agent for modifying or reforming the polished surface of the semiconductor wafer. Specifically, an oxidizing agent such as H
2
O
2
(hydrogen peroxide) is added for the purpose of oxidizing a metal film of copper or tungsten that has been deposited on the semiconductor wafer. It has been customary to add the additive when the polishing liquid is produced. Thus, in the case where the additive, like oxidizing agent, added to the polishing liquid is chemically unstable, the properties of the polishing liquid tend to be changed when the polishing liquid with the additive is held in stock for a long period of time, with the result that the polishing capability of the polishing liquid becomes unstable.
If the additive is added to the polishing liquid in the polishing liquid supply system, then it has been the general practice to supply the additive, which has been diluted to a desired concentration with a solvent such as pure water in a polyethylene container or the like, from an additive supply unit to the polishing liquid supply system. Thus, the additive supply unit is relatively large in size, and needs a large installation space. In addition, because the additive is added in a small quantity to the polishing liquid in the polishing liquid supply system, the additive is required to be supplied highly accurately.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a polishing liquid supply apparatus which is capable of supplying a polishing liquid that stably contains an additive to a polishing unit, and a polishing apparatus having such polishing liquid supply apparatus.
According to an aspect of the present invention, there is provided an apparatus for supplying a polishing liquid to a polishing unit for polishing a workpiece, comprising: a supply tank for storing a polishing liquid having a predetermined concentration; a polishing liquid pipe for delivering the polishing liquid from the supply tank to a polishing liquid supply nozzle in the polishing unit; an additive tank for storing an additive having a predetermined concentration; and an additive supply pipe for adding the additive supplied from the additive tank to the polishing liquid stored in the supply tank or to the polishing liquid in a polishing liquid passage including the polishing liquid pipe.
Since the additive is added to the polishing liquid at a position close to the polishing unit where the polishing liquid is used, the polishing liquid that contains the additive of stable quality at a required concentration can be supplied to the polishing unit even if the additive comprises an oxidizing agent or the like that tends to be easily degraded or decomposed due to aging. Therefore, the polishing unit can polish a workpiece stably in a high quality with the polishing liquid. The additive may comprise an oxidizing agent such as iron nitrate, an aqueous solution of hydrogen peroxide or ammonium persulfate, or material of stabilizing the distribution of particle diameters of abrasive particles in the polishing liquid.
The polishing liquid supply apparatus may further comprise an additive concentration adjusting device for adjusting the concentration of the additive. The additive concentration adjusting device may comprise an additive preparing device for mixing a raw material powder and a solvent to form the additive. Inasmuch as the additive is prepared from its raw material immediately before it is used, the additive is prevented from being degraded or d
Chono Keiko
Kawashima Kiyotaka
Shimomoto Hiroshi
Tanikawa Mutsumi
Ebara Corporation
Hail III Joseph J.
Ojini Anthony
Wenderoth , Lind & Ponack, L.L.P.
LandOfFree
Polishing liquid supply apparatus does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Polishing liquid supply apparatus, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Polishing liquid supply apparatus will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2821300