Adhesive bonding and miscellaneous chemical manufacture – Differential fluid etching apparatus – With microwave gas energizing means
Reexamination Certificate
1999-06-17
2001-08-21
Mills, Gregory (Department: 1763)
Adhesive bonding and miscellaneous chemical manufacture
Differential fluid etching apparatus
With microwave gas energizing means
C451S287000
Reexamination Certificate
active
06277236
ABSTRACT:
BACKGROUND
1. Field of Invention
The present invention relates to semiconductor device manufacturing and, in particular, to apparatuses and methods for chemical-mechanical polishing of semiconductor wafers.
2. Related Art
FIG. 1
is a side view of a conventional chemical-mechanical polishing (CMP) apparatus used, for example, to planarize the device surface of a processed semiconductor wafer during device fabrication. Circular platen
10
is shown connected to platen drive
12
through shaft
14
. Platen drive
12
causes platen
10
to rotate during polishing operations. Polishing pad
16
is shown mounted on platen
10
top surface
18
. The top surface of pad
16
is polishing surface
20
. Pad
16
is typically felt or urethane with a foam backing, or a material having an abrasive embedded in surface
20
.
Also shown is a conventional wafer carrier
22
positioned over platen
10
. Carrier
22
is attached to carrier drive
24
through shaft
26
. Carrier
22
holds device surface
28
of processed semiconductor wafer
30
against polishing surface
20
during polishing. During some conventional polishing operations, carrier drive
24
causes carrier
22
, and hence wafer
30
, to rotate against polishing surface
20
. In other conventional polishing operations, carrier drive
24
causes carrier
22
, and hence wafer
30
, to translate laterally across polishing surface
20
. In some apparatuses drive
24
may cause simultaneous rotational and translational motion of carrier
22
.
Slurry reservoir
32
supplies conventional polishing slurry
34
to polishing surface
20
using conventional slurry delivery system
36
. Slurry
34
may be an abrasive carried in a fluid suspension, a compound formulated to have a chemical effect on device surface
28
, or a combination of both. Platen
10
's rotation causes slurry
34
to flow radially outward across polishing surface
20
, thus creating a thin layer (not shown) of polishing slurry on surface
20
. Delivery system
36
typically includes pumps and tubing (not shown).
During conventional chemical-mechanical polishing, slurry
34
is dispensed at a fixed flow rate onto polishing surface
20
. Wafer
30
is mounted to carrier
22
which is then positioned to place device surface
28
against polishing surface
20
. Platen
10
and carrier
22
are rotated and, as additional slurry
34
is introduced, the desired polishing effect on device surface
28
is obtained. When polishing is completed, carrier
22
is removed from polishing surface
20
and wafer
30
is removed from carrier
22
. A new wafer may then be mounted on carrier
22
, and the polishing process is repeated.
The polishing operation adversely affects polishing surface
20
. The pressure of device surface
28
against polishing surface
20
typically deforms surface
20
's fine surface structure. Therefore, a conditioner is typically used either during or after polishing so as to keep surface
20
in a near pristine state. The conditioner is typically a compound of diamonds that are bonded to a substrate. The bonded diamonds and substrate are then nickel plated, and the combination is used to clean and roughen the polishing pad surface. The conditioning process is difficult to optimize, however, and consequently it is difficult to keep polishing surface
20
in the required state for proper polishing. What is required is a chemical-mechanical polishing apparatus and process in which the polishing surface is easily kept in a near optimum state for polishing.
SUMMARY
In accordance with the invention, a chemical-mechanical polishing (CMP) apparatus is configured with an aggregate polishing disk mounted on a rotating platen. The aggregate polishing disk includes abrasive particles held in solid suspension by a radiant energy sensitive bonding agent. In some embodiments the abrasive particles are of silicon oxide (silica), aluminum oxide, or cerium oxide, and the bonding agent is a conventional positive photoresist that is sensitive to ultraviolet (UV) light. The aggregate polishing disk has a flat top surface.
The CMP apparatus also includes a fixture holding a radiant energy source for emitting energy to which the bonding agent is sensitive, such as a UV light source. In some embodiments the UV light source is a plurality of conventional UV producing light bulbs, and in other embodiments a single conventional long UV producing bulb is used. The UV light source fixture is configured with a slot so that UV light from the UV light source shines through the slot. The fixture is positioned over the aggregate polishing disk's top surface so that the slot is approximately aligned with a radius of the disk. Thus, UV light from the UV light source is incident on the aggregate polishing disk top surface through the slot. In some embodiments the slot is a tapered shape so that an approximately equal amount of UV light is incident per unit area of the top surface as the rotating top surface passes beneath the slot. A thin layer of the positive photoresist underneath the top surface is exposed by the incident UV light.
In addition, the CMP apparatus comprises a reservoir containing a developing fluid and a conventional dispensing mechanism to dispense the developing fluid to the aggregate disk's top surface. Some embodiments of the invention use potassium hydroxide (KOH) or ammonium hydroxide (NH
4
OH) as the developing fluid, although other compounds may be used. In some embodiments of the invention a second reservoir containing a rinsing fluid and a second conventional dispensing mechanism is added. Some embodiments of the invention use deionized water as a rinsing fluid.
In accordance with the invention, a semiconductor wafer may be processed as follows. The aggregate polishing disk is rotated and the top surface receives UV light through the slot in the UV fixture. The UV light exposes a thin top portion of the aggregate disk as the disk rotates. After exposure, developing solution is dispensed onto the aggregate disk's top surface and is dispersed into a thin film by the disk's rotation. The developing fluid develops and dissolves the thin layer of UV-exposed positive photoresist, thus releasing the abrasive particles within the UV-exposed layer. Thus a polishing slurry of developing fluid and abrasive particles is created. The surface underlying the developed thin layer acts as a polishing surface.
A processed semiconductor wafer is mounted to a conventional wafer carrier and is held against the polishing surface of the rotating aggregate disk such that a thin film of polishing slurry exists between the polishing surface and the wafer's device surface. In some embodiments the polishing surface continually receives UV light and developing fluid during polishing. The constant UV exposure and developing of a thin top portion of the polishing disk ensures adequate slurry is available for polishing. In some embodiments the amount of UV exposure and dispensed developing fluid is controlled so as to control the resulting amount of polishing slurry. When polishing is complete the wafer is removed, rinsing fluid is dispensed onto the polishing surface to remove the used polishing slurry, and the polishing process may be repeated for another processed wafer. No polishing surface conditioning is required.
REFERENCES:
patent: 5811355 (1998-09-01), Jordan
patent: 5827112 (1998-10-01), Ball
patent: 61-270060 (1986-11-01), None
patent: 63-134162 (1988-06-01), None
patent: 10-249735 (1998-09-01), None
Allenby Christopher B.
Goudreau George
Mills Gregory
National Semiconductor Corporation
Skjerven Morrill & MacPherson LLP
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