Coating apparatus – Gas or vapor deposition – With treating means
Reexamination Certificate
2000-11-08
2003-09-30
Alejandro, Luz L. (Department: 1763)
Coating apparatus
Gas or vapor deposition
With treating means
C118S715000, C118S7230AN
Reexamination Certificate
active
06626998
ABSTRACT:
FIELD OF THE INVENTION
The present invention is in the field of thin-film deposition, such as Chemical Vapor Deposition (CVD) and Plasma Enhanced Chemical Vapor Deposition (PECVD) for semiconductor manufacture, and pertains more particularly to methods and apparatus for generating and maintaining a uniformly-charged plasma in a reactor without requiring extensive metal-from-metal insulation.
BACKGROUND OF THE INVENTION
In the field of Thin Film Technology, used extensively in manufacture of integrated circuits, requirements for thinner deposition layers, better uniformity over larger surfaces, and larger production yields have been, and are, driving forces behind emerging technologies developed by equipment manufactures. As semiconductor devices become smaller and faster, the need for greater uniformity and process control of film properties such as layer thickness, uniformity, and the like rises dramatically.
Various technologies are well known in the art for applying thin films to substrates in manufacturing steps for integrated circuits (ICs). Among the more established technologies available for applying thin films is Chemical Vapor Deposition (CVD), which includes Plasma Enhanced Chemical Vapor Deposition (PECVD). These are flux-dependent applications requiring specific and uniform substrate temperature and precursors (chemical species) to be in a state of uniformity in the process chamber in order to produce a desired film of uniform thickness on a substrate surface. These requirements become more critical as substrate size and device size increases, creating a need for more complexity in chamber design and gas flow techniques to maintain adequate uniformity.
CVD systems use a variety of known apparatus for delivering precursor gases to target substrates. Generally speaking, gas delivery schemes for CVD and PECVD processes are designed specifically for one particular application and substrate size. Therefore variations in theme of such delivery apparatus and methods will depend on the particular process parameters and size of substrates being processed in a single reactor. Prior art gas manifolds and diffusers have been manufactured from a variety of materials and are widely varied in design. For example, some gas delivery manifolds are long tubes that are either straight or helical with a plurality of small, often differently sized, gas delivery holes spaced longitudinally along the manifold. Most diffusers and showerheads are basically baffle-type structures having a plurality of holes placed in circular or spiral type arrangements on opposite facing plates or surfaces. Often the holes are contained in a series of expanding radii circles on each plate. Often such apparatus is adapted only for one type of process and cannot be used with other processes using the same CVD equipment.
One characteristic that is generally required in CVD gas delivery apparatus is that hole sizes and spacing between the holes is strictly controlled such that a uniform gas distribution or zone is maintained over a particular surface area. Uneven gas flow often results if some holes are inadvertently made too large in comparison with a mean size, or placed in wrong positions. If a larger substrate is used in a same or different chamber, then the gas delivery apparatus must often be exchanged for one that is designed and adapted for the variance in substrate size and/or chamber parameters. Improvements made to manifold and diffuser designs depend largely on empirical methods in the field resulting in numerous cases of product expenditure through batch testing.
One problem with many diffusing showerhead systems relates to limited gas flow dynamics and control capability. For example, gas delivered through a typical showerhead covers a diffusion zone inside the chamber that is produced by the array of diffusion holes placed in the showerhead. If a system is designed for processing a 200-mm wafer or wafer batch, the gas diffusion apparatus associated with that system will produce a zone that is optimum for that size. If the wafer size is increased or reduced beyond the fixed zone capability of a particular showerhead, then a new diffusion apparatus must be provided to accommodate the new size. There are typically no conventions for providing more than a few zones or for alternating precursor delivery for differing size substrates in one process.
In an environment wherein different sizes of substrates are commonly processed, it is desired that diffusing methods and apparatus be more flexible such that multi-zone diffusing on differing size substrates is practical using one showerhead system. This would allow for less downtime associated with swapping equipment for varying situations, and better uniformity by combining and alternating different zones during diffusion.
A gas diffusing system known to the inventor provides multi-zone (target zone) gas diffusing capability for CVD and PECVD systems. Zone-independent gas-supply lines integrated with the system allow process operators to adjust gas flow to each created target zone. A plurality of physical gas zones provided and contained in the diffuser assembly may be used alternately, in unison, or in specific combinations such that deposition uniformity is enhanced and may be fine-tuned during process.
The multi-zone diffuser known to the inventor uses an upper diffusing component, a gas transition component, and a lower diffusion component. All three components cooperate to provide a uniform layering capability that is consistent from process to process and batch to batch. The diffuser also is flexible to variances in substrate size by virtue of adding or subtracting physical gas zones in the diffuser thereby affecting target zones in the reactor.
As described above, PECVD has certain advantages over stock CVD applications because of a higher reactive state of precursor, which is charged by an RF plasma electrode. In standard CVD, plasma is sometimes used, not as a precursor, but for enhanced cleaning operations between deposition processes.
In PECVD, it is desired that a constant uniform state of charged plasma be maintained for enhancing reactivity for deposition and, of course, chamber cleaning. As with gas introduction, it is important that plasma is uniformly generated for the purpose of providing a uniform precursor reaction. If plasma is not uniform in generation than precursor will not react uniformly over a target, and may act to actually disturb otherwise uniform layering. In generating the plasma, it is desired that bombardment of precursor be directed in an effective manner to enhance uniformity.
In prior art applications the diffuser assembly or showerhead itself is used as the electrode for plasma charging and RF power is applied directly. This method requires extensive insulation steps in order to isolate the desired component acting as the electrode from the rest of an assembly. Also, typical gas diffusion apparatus has have large cavities to allow the gas to diffuse, and these areas can be susceptible to striking a plasma which is undesirable.
As a result of the above, insulating components, such as rings, plates and so on must be placed between metal components. Moreover, the component acting as the RF electrode is, most often, not physically designed to optimize plasma generation in the chamber.
What is clearly needed is a modular apparatus and method for generating and maintaining a uniform charged plasma in a PECVD or CVD process that requires minimum metal-from-metal insulation procedures. Such a system would enhance uniform plasma reactivity in process and facilitate expeditious maintenance operations between processes.
SUMMARY OF THE INVENTION
In a preferred embodiment of the present invention an RF electrode module for use with a gas-diffuser showerhead device in a CVD chamber is provided, comprising an electrically-conductive electrode ring with a ring inside diameter (R-ID) and a ring outside diameter (R-OD), the ring having an upwardly-extending power post, and an internal water-cooling channel open to an upwardly extendi
Alejandro Luz L.
Boys Donald R.
Central Coast Patent Agency Inc.
Crowell Michelle
Genus Inc.
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