Coating apparatus – Gas or vapor deposition
Reexamination Certificate
2000-03-07
2002-09-03
Lund, Jeffrie R. (Department: 1763)
Coating apparatus
Gas or vapor deposition
C156S345340
Reexamination Certificate
active
06444039
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to an apparatus for use in the integrated circuit (IC) fabrication processes and, more particularly to a three-dimensional showerhead for use in delivery of precursors to a substrate.
BACKGROUND OF THE INVENTION
Two of the most fundamental processes in IC fabrication are chemical vapor deposition (CVD) and etching. CVD processes use vapor precursors for the deposition of thin films on an IC substrate, while etching processes use vapor precursors for the etching of thin films on an IC substrate. The basic differences between CVD and etching processes are the precursors used and the process conditions applied, since the reaction systems used in both processes are similar. Basically, the reactor used for both processes consists of a precursor delivery system, a substrate and an energy source to decompose the precursor vapor to a reactive species to allow a thin film to form on the substrate (CVD process) or to etch an existing thin film on the substrate (etch process). Effective power sources are heat and plasma energy such as radio frequency (RF) power, microwave energy (MW) power, low frequency (10 KHz-1 MHz) power, optical energy (e.g. a laser or ultraviolet light) to decompose the introduced precursors. Also, the substrate could be biased or heated (100° C.-1200° C.), often in the case of CVD processes, to promote the reaction of the decomposed atoms or molecules and to control the physical properties of the formed films.
The precursor delivery system often consists of a showerhead-type disperser for the introduction of precursor vapor into the reactor. The showerhead could incorporated a heat transfer structure whereby the temperature of the precursors is controllably maintained at the desired temperature level for efficient operation. Precursors are the chemical compounds that could be brought together in a reactor chamber. The reactive precursors either decompose or react with each other under a catalyst or an energy source. Non-reactive precursors such as helium, nitrogen, argon sometimes are used to dilute the reactive precursors or to provide a curtain wall. The precursors should be in the gaseous state before reaching the substrate to ensure uniform coating (CVD) or uniform etching (etching system), and to allow efficient molecular interaction. Outside the reaction chamber, the precursors could be in gaseous, liquid or solid state. Gaseous state precursors are the simplest form in IC processing since no extra work will be involve in the delivery of the precursors to the substrate. Liquid precursors require a vaporizer to convert to the gaseous state before exiting the showerhead. Solid precursors also need to be converted into the gaseous state. A vaporizer is normally a heated plate where the thermal energy supplied can vaporize the liquid precursor at the inlet and release vapor precursor at the outlet.
FIG. 1
is a prior art schematic diagram showing a typical showerhead. The showerhead consists of the body structure
6
, enclosing an interior volume
8
. The precursor enters through the inlet port
3
, disperses in the interior volume
8
by the baffle
5
, and exits through the outlet ports
4
to the wafer
18
, sitting on top of the substrate
1
. The heater
2
is used to maintain the showerhead at the desired temperature. The basic structure of the showerhead is the flat surface
7
in parallel to the substrate
1
. The precursor flow
20
is in one direction only which is perpendicular to the flat surface
7
. A significant portion of the unreacted precursor is lost through the gap between the showerhead bottom surface
7
and the substrate
1
. Various designs of the showerhead exist in the literature, but all of them have a flat bottom surface containing the outlet ports, therefore significant precursor loss is inevitable.
FIG. 2
is another prior art schematic diagram described by Yong Ku Baek (U.S. Pat. No. 5,670,218) to focus the precursor onto the substrate. The showerhead has a baffle guide
9
, surrounding the substrate
1
and the showerhead. This baffle guide
9
serves to prevent the precursor from the showerhead from diffusing too widely or from leaking into a vacuum port too rapidly. This design helps reduce precursor loss, but with the complexity of a separate baffle guide. Furthermore, uniform heating of the showerhead and the baffle guide is difficult or complex. In fact, Yong Ku Back has not attempted to provide a heater element for his showerhead system. Also the precursor flow is in one direction only.
Another important aspect of the process reactor, be it a CVD system or an etching system, is the heating of the reactor walls to prevent precursor condensation or moisture absorption. In both prior art showerhead designs, separate heated reactor walls are needed to confine the showerhead and the substrate.
It would be advantageous if the precursor flow from the showerhead has more than one direction to further mixing of the precursor.
It would be advantageous if a showerhead could minimize the precursor loss during delivery to the substrate.
It would be advantageous if a showerhead could confine the precursor vapor within the reaction zone.
It would be advantageous if a showerhead could be efficiently heated.
It would be advantageous if a showerhead could function as the reaction container to simplify the reactor design.
It would be advantageous if a showerhead could offer a vapor curtain wall to further confine the precursor inside the reaction zone.
Accordingly, a three-dimensional showerhead for a vapor supply apparatus is provided. The three-dimensional showerhead comprises an inverted-cup structure having double walls, an outer wall and an inner wall, said double walls defining a first interior volume and said inner wall defining an exterior cavity, said structure further having:
a plurality of first inlet ports connected to said outer wall for introducing first process precursors into said first interior volume;
a plurality of first outlet ports at said inner wall for discharging the first precursor vapor from said first interior volume to said exterior cavity.
The invention provides a three-dimensional showerhead covering all directions except the direction covered by the substrate. Accordingly, the precursor vapor exiting from the showerhead will come from all directions except the direction covered by the substrate. The showerhead could be made of metal such as stainless steel, aluminum, or anodized aluminum. The metal showerhead could be used as an electrode in generating a plasma for the reactor. The showerhead could also be made of insulated material such as ceramic. The showerhead could also be made of transparent materials such as glass or quartz to permit the use of a lamp heating system.
In some aspects of the invention, the outlet port dimension ranges from 0.2 mm to 2 mm in diameter. The outlet ports in the horizontal flat area of the showerhead are arranged in such a configuration as to provide uniform delivery of the precursor vapor to the flat portion of the substrate. Concentric circles, repeated polygons such as a hexagon, square, or triangle pattern are some examples of the outlet ports pattern. The outer ports in the vertical walls of the showerhead are arranged in such configuration to optimize the process film quality. In some aspects of the invention, the flow will be horizontal with small openings to create a high velocity gas in the cavity. In some aspects of the invention, the flow will be angled downward to minimize the turbulence in the cavity. The inlet ports are arranged in such configuration to maximize the uniformity of the precursor flow at the outlet. Examples of the configuration could be a single inlet port at the center of the showerhead, or 3 inlet ports arranged in a triangular pattern, or 4 inlet ports arranged in a square pattern.
In some aspects of the invention, a heat transfer structure is included in the showerhead structure to controllably maintain the showerhead at the desired temperature level for efficient operation.
In some aspects of the inv
Lund Jeffrie R.
Simplus Systems Corporation
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