Apparatus for sidewall profile control during an etch process

Details Apparatus for sidewall profile control during an etch process Apparatus for sidewall profile control during an etch process

1996-10-01

2001-06-19

Mills, Gregory (Department: 1763)

Adhesive bonding and miscellaneous chemical manufacture

Differential fluid etching apparatus

With microwave gas energizing means

C118S712000, C118S7230ER, C118S7230IR, C118S7230ME

Reexamination Certificate

active

06248206

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Technical Field
The invention relates to plasma processing. More particularly, the invention relates to a plasma etch process for controlling the profile of an etched sidewall.
2. Description of the Prior Art
Plasma processing is an essential tool of the semiconductor manufacturing industry. In a plasma etch process, electromagnetic radiation is used to dissociate the molecules of process gas to produce a reactive species. i.e. a plasma. The plasma is directed to the surface of a workpiece, such as a semiconductor wafer, in a process environment, typically a vacuum chamber. The wafer is masked with a photoresist material to define a circuit pattern. The plasma etches openings into unmasked portions of the wafer. The slope or profile of these openings varies according to the choice of plasma precursor process gases. Thus, an isotropic process etches equally in all directions, while an anisotropic process etches primarily in one direction. For example, processes such as reactive ion etch (“RIE”) permit the anisotropic etching of small openings having high aspect ratios. Smaller device features may thereby be produced.
FIG. 1
illustrates a typical RIE apparatus, according to the prior art. A wafer support
12
is located within the process chamber
10
. The wafer support is connected to a radio frequency (“RF”) power source
14
and serves as a cathode. The walls
16
and base
18
of the chamber form the grounded anode of the system.
Gas supplied to the chamber through an inlet port
20
passes through a gas distribution plate
22
and is directed to the surface of the workpiece
24
. The RF energy supplied to the process chamber dissociates the molecules of the process as to produce a reactive species that is used to etch the workpiece.
Alternately, the plasma may be remotely generated in an applicator
26
by application of a microwave (“MW”) or RF power source
28
. The remotely generated plasma is then ported to the process chamber. An anisotropic etch is achieved as the amount of RF energy supplied to the electrodes is increased. The spent process gas is then exhausted from the process chamber through an outlet port
30
by a vacuum pump
32
.
It is often desirable to control the profile of the sidewalls of the etched opening. For example, sloped sidewalls are desired when an opening is made in a dielectric layer, such as silicon oxide, for the deposition of metal. It is known to use various etchant mixtures to produce sloped sidewalls. However, such processes are generally difficult to control, such that the resulting openings are non-uniform. Further, it is difficult to provide smaller interlayer and active element contact regions than the corresponding feature size on the overlying photoresist layer. Rather, the etch process tends to etch under the photoresist, thereby producing an opening having a larger diameter than that of the masked region of the wafer.
It would therefore be advantageous to provide a process for controlling the profiles of sidewalls formed when etching a workpiece. It would be a further advantage if such process provided smaller interlayer and active element contact regions than the corresponding feature size on the overlying photoresist layer.
SUMMARY OF THE INVENTION
The invention provides a process for controlling the profile of the sidewalls in an opening that is etched in a semiconductor wafer. Microwave or radio frequency energy is remotely applied to pre-excite a process gas that is used in a process chamber. Radio frequency energy is also supplied to a process gas within the process chamber. The sidewall profile is controlled by independently varying the ratio of remote microwave or radio frequency energy supplied to that of the radio frequency energy supplied within the process chamber. The sidewall profile is also controlled by varying the process gas flow rate and composition, and the pressure within the process chamber. For example, a more vertical, anisotropic etch profile is obtained by providing increased radio frequency energy to the process chamber, while operating the process chamber at a lower pressure. Likewise, a more horizontal, isotropic profile is obtained by supplying decreased radio frequency energy to the process chamber, while operating the process chamber at a higher pressure. The same process chamber may thereby be used for both isotropic and anisotropic etching processes.
As the etch process progresses, the radio frequency component supplied to the process chamber is varied to provide an etched feature that is narrower than the overlying photoresist pattern. Interlayer and active element contact regions may thus be provided that are smaller than the corresponding feature size on the overlying photoresist layer. Further, the etch profile may be varied within a single etch process by supplying a programmed energy/pressure profile to the process chamber.


REFERENCES:
patent: 4891118 (1990-01-01), Ooiwa et al.
patent: 4960073 (1990-10-01), Suzuki et al.
patent: 5160397 (1992-11-01), Doki et al.
patent: 5181986 (1993-01-01), Ooiwa
patent: 5385624 (1995-01-01), Ameniya et al.
patent: 5611863 (1997-03-01), Miyagi
patent: 5626679 (1997-05-01), Shimiuz et al.
patent: 5739051 (1998-04-01), Saito
patent: 5916455 (1999-06-01), Kumagai

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