Semiconductor device manufacturing: process – Coating with electrically or thermally conductive material – To form ohmic contact to semiconductive material
Reexamination Certificate
1998-04-20
2003-10-21
Smith, Matthew (Department: 2825)
Semiconductor device manufacturing: process
Coating with electrically or thermally conductive material
To form ohmic contact to semiconductive material
C438S685000, C134S001100, C134S002000
Reexamination Certificate
active
06635569
ABSTRACT:
This invention relates semiconductor substrate processing by the application of titanium coatings, particularly by plasma enhanced chemical vapor deposition (PECVD) methods. The invention more particularly relates to the cleaning and stabilizing of CVD reactors used in such processing and to the passivating and conditioning of such reactors following such cleaning and to maintaining the reactors in a stable state during the subsequent use of the reactors for Ti-PECVD processing of semiconductor substrates.
BACKGROUND OF THE INVENTION
Chemical vapor deposition (CVD), and particularly plasma enhanced chemical vapor deposition (PECVD) are processes that are being increasingly used in the application of titanium (Ti) or titanium-containing films to substrates in semiconductor manufacture. One such Ti-PECVD process is at least theoretically available to deposit titanium on contacts of features, particularly high aspect ratio features, on semiconductor wafers. In investigating contact level metallurgy in the course of arriving at the present invention, applicants have determined that production applications with such processes involve issues of process uniformity, process repeatability and process stability that are as important as the fundamental film properties and deposition characteristics.
One such issue is the cleaning methodology for the chamber of the reactor in which the CVD is carried out. Such reactors must be treated to remove accumulated reactants, reaction products and reaction by-products from the reactor surfaces. Materials that collect on these surfaces during the use of the reactor for Ti-CVD are often sources of peeling and contamination in the chamber, leading to a high number of particles which cause contamination of the surfaces of the wafers being processed resulting in interference with critical process reactions on the wafer. Also, accumulation of this material on the surfaces of a reactor can cause long term drifts in process parameters leading to unstable or unpredictable process performance and degraded process results. Furthermore, many CVD reactors that are available for Ti-CVD are provided with nickel alloy susceptors on which the wafers are supported for processing. Silicon wafers have a greater tendency to stick to a nickel alloy susceptor following the cleaning of the susceptor.
When the conditions of surfaces in a CVD reactor used for Ti-PECVD are changed, such as by cleaning the reactor to remove deposits that accumulate during deposition, changes occur in the deposition processes which stabilize only after some form of chamber conditioning. Applicants' empirical observation is that, following such changes in reactor conditions, there is either some amount of reactor operating time that must transpire or some number of wafers that must be processed in a reactor before the process stabilizes. Applicants believe that this effect is due to a change in the state of the reactor surfaces, due in part to film deposition on the surfaces which alters thermal emissivity, adhesive properties, electrical conductivity or other properties that directly affect the results on the processed wafers. It is desirable to minimize the amount of time devoted to the initial conditioning of a reactor following cleaning or other such condition changes of the reactor before the introduction of wafers into the chamber for processing, particularly in a manufacturing environment.
Deposition chambers are typically cleaned in one of two ways: 1) In situ cleaning, by which reactor surfaces are cleaned without opening the system to air, and preferably without cooling any parts of the chamber, and 2) wet cleaning, which generally entails cooling the reactor components, opening the system and wiping or scrubbing the reactor components with water or other chemicals to remove deposits from them. For both of these methods, applicants observe that the process must be recovered, that is, the chamber should be reconditioned, to stable baseline performance after the cleaning procedure has been carried out.
The Ti-PECVD process uses TiCl
4
and H
2
in a reduction reaction conducted in a plasma environment to form metallic Ti as the main reaction product and HCl as the main reaction by-product. During the course of this reduction reaction, other by-products may form, such as TiCl
x
, with x<4. These products, along with metallic Ti, may be deposited on reactor surfaces to an extent that is strongly related to the chamber geometry and to the temperature distribution on the reaction chamber surfaces. Hot metallic surfaces, such as hot nickel alloy surfaces for example, when directly exposed to TiCl
4
, have a tendency for metal chlorides to form thereon that may have a detrimental effect on process performance. For the PHOENIX™ system of applicants' assignee, for example, such reactor surfaces on which such undesirable deposition may tend to occur are the face of the substrate-supporting susceptor, the face of the process gas dispersing showerhead, and a limited region on the reactor walls located near the plane of the wafer and below. The composition of deposited material is related to the temperature of the surface on which it deposits and to the concentration of various reaction species, reactants, reaction products and reaction by-products at such surface.
For example, during continuous operation of a Ti-PECVD process, Ti bearing films accumulate on the internal surfaces of the reactor. The composition of these films range from Ti rich on the hotter surfaces to Cl rich on the colder surfaces of the reactor. These films are intrinsically unstable. The Ti rich films oxidize over time upon exposure to the residual water and oxygen that are present in the chamber. Since this oxidation has, in the prior art, been a highly uncontrolled process, it has been regarded as undesirable. During oxidation of these Ti rich films, their physical properties change from electrically conducting to electrically insulating, resulting in unstable and otherwise changing plasma and other characteristics within the chamber during the performance of coating processes. Cl rich films, on the other hand, have a relatively high vapor pressure and result in an uncontrolled background of TiCl
x
(x<4) in the chamber. These TiCl
x
species contribute to the deposition reaction and result in unstable process characteristics.
The material that deposits on the walls and other reactor surfaces during the formation of titanium is very hygroscopic and deliquescent, reacting with residual water vapor and O
2
, when present, to form a TiO
2
-based film. The gettering properties of such Ti films are well known. TiO
2
film has the properties of being chemically stable and electrically non-conductive. Where a reactor having a titanium rich coating on its internal components must be opened for cleaning, these reactions accelerate, producing airborne reaction by-products and heat, which are hazards that must be controlled.
Titanium films that are deposited onto semiconductor wafers are usually followed by a passivation process by which a passivating layer of a stable substance such as titanium nitride is deposited on the surface of the titanium film. Where the Ti deposition process is one of CVD, the TiN film is formed in a dedicated reactor by the reaction of titanium with ammonia. The formations of the Ti and overlying TiN films is carried out in a multiple reactor tool having a Ti-CVD reactor and a TiN-CVD reactor connected to a transfer module through which wafers are transferred from the Ti-CVD module to the TiN-CVD module for successive processing.
There exists a need to more efficiently and effectively condition a reactor, particularly one used for the PECVD of titanium, following the cleaning of the reactor.
SUMMARY OF THE INVENTION
A primary objective of the present invention is to provide stable process performance in a Ti-PECVD apparatus.
A particular objective of the present invention is to provide a Ti-PECVD method and apparatus which maintains the reactor in a stable condition and maintains the stable p
Ameen Michael S.
Hillman Joseph T.
Leusink Gert
Ward Michael
Yasar Tugrul
Rocchegiani Renzo
Smith Matthew
Tokyo Electron Limited
Wood Herron & Evans L.L.P.
LandOfFree
Method of passivating and stabilizing a Ti-PECVD process... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method of passivating and stabilizing a Ti-PECVD process..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method of passivating and stabilizing a Ti-PECVD process... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3166111