Semiconductor device manufacturing: process – Coating with electrically or thermally conductive material – To form ohmic contact to semiconductive material
Reexamination Certificate
2002-10-02
2004-04-13
Ghyka, Alexander (Department: 2812)
Semiconductor device manufacturing: process
Coating with electrically or thermally conductive material
To form ohmic contact to semiconductive material
C438S681000, C438S785000, C427S248100
Reexamination Certificate
active
06720259
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to semiconductor processing and, more particularly, to a method for improved control of uniformity and repeatability in Atomic Layer Deposition and/or Chemical Vapor Deposition.
BACKGROUND OF THE RELATED ART
Chemical Vapor Deposition (CVD) is a widely used deposition process for the growth of thin films on various substrates, including semiconductor wafers. As microelectronics device dimensions are reduced, or scaled down, CVD is becoming an attractive method for the deposition of conformal films over complex device topography. Additionally, new materials are considered in the design of advanced devices. For example, high dielectric constant (k) oxide materials are attractive alternative to the conventionally employed silicon-based oxides for use as gate or capacitor dielectrics. Recently, some dynamic random access memory (DRAM) products have been manufactured, in which CVD is used to deposit high-k tantalum pentoxide (Ta
2
O
5
).
In the field of material deposition, a process known as Atomic Layer Deposition (ALD) has emerged as a promising candidate to extend the abilities of CVD techniques. Generally, ALD is a process wherein conventional CVD processes are divided into separate deposition steps that theoretically go to saturation at a single molecular or atomic monolayer thickness and self-terminate. For ALD applications, the molecular precursors are introduced into the reactor separately. Typically, an ALD precursor reaction is followed by inert gas purging of the reactor to remove the precursor from the reactor prior to the introduction of the next precursor.
One way of classification of the CVD/ALD type of deposition reactors is by the temperature at which the reactor wall is maintained with respect to the deposition temperature of a substrate resident in the reactor. In “cold wall” and “warm wall” reactors, the reactor chamber wall (or vacuum containing surface) is maintained at a temperature that permits physisorption or limited (or imperfect, or partial) chemisorption. This is in contrast to hot wall reactors where the wall temperature is close to or near the substrate deposition temperature, where chemisorption and deposition takes place by design.
In CVD the films are deposited from molecular precursors that are carried to the reactor in a vapor state, typically mixed with an inert carrier gas. A substrate is kept at temperature that is optimized to promote chemical reaction between the molecular precursors concurrent with efficient desorption of byproducts. Accordingly, the reaction proceeds to deposit the desired pure film. The selection of a suitable precursor is a key in CVD, as there are a number of restrictions on the precursor's physical and chemical properties. In particular, the precursor should be of sufficient volatility at temperatures below the decomposition temperature in order for the vapors to be transported to the reactor without premature decomposition. The requirement for saturation of the precursor reactions in ALD imposes additional constraints on the potential precursors.
Generally the precursors for CVD and ALD fall in 3 categories based on their volatility: 1) gases (e.g., NH
3
and WF
6
); 2) high vapor pressure (e.g., 5 to 40 Torr @ room temperature (RT)) liquids (e.g., trimethyl aluminum (TMA), SiCl
4
, TiCl
4
, H
2
O) and solids (e.g., W(CO)
6
); and
3)
low vapor pressure (e.g., less than 0.5 Torr @ RT) liquids (e.g., some metal organic Zr, Ta, and Hf precursors) and solids (e.g., TaCl
5
, HfCl
4
, ZrCl
4
). Additionally some solids may be dissolved in a solvent and handled as liquids. While gases and high vapor pressure precursors are clearly desirable, such precursors are not available for the deposition of pure, high quality films by CVD or ALD.
Containers for precursors with high vapor pressure are typically maintained at room temperature and some gas lines between the precursor container and CVD or ALD reactor may be heated to a moderate temperature (e.g., <100° C.) to reduce adsorption or condensation. In warm and/or cold (warm/cold) wall reactors, the reactor chamber walls are typically maintained at or below the temperature where precursor condensation occurs. In contrast, the containers for precursors with low vapor pressure are typically maintained at high temperature to generate sufficient vapor and gas lines between the precursor container and CVD or ALD reactor are usually heated to a temperature higher than the temperature of the precursor container to prevent condensation. When the precursor container temperature is higher than the temperature of some inner reactor surfaces, precursor condensation typically occurs on these surfaces. In CVD processes this may cause thickness non-uniformity due to precursor depletion and consequently different deposition rate on different areas on the substrate. In ALD processes some of the condensed precursor may be desorbed and travel to some areas of the substrate surface simultaneously with the second precursor, resulting in excess film thickness deposition on these areas of the substrate. The precursor that remains condensed on the reactor surfaces may react with the second precursor to form a parasitic film on these surfaces. Typically this film is of poor or inferior quality compared to the quality of the film deposited on the substrate. The net effect is depletion of one or both precursors which may result in less film thickness on some areas of the substrate due to insufficient precursor delivery to the substrate surface. Thus, various mechanisms may contribute to non-uniform film deposition and also lead to gradual deterioration of the thickness uniformity and repeatability of deposited films over time.
Thus, a need is present to improve uniformity and repeatability when depositing a film layer in ALD and CVD reactors. The need is more pronounced in depositing films on substrates using low vapor pressure precursors.
SUMMARY
A technique to deposit a passivating layer by a first chemical process on a cold or warm wall CVD or ALD reactor to improve uniformity of a film layer deposited on a substrate resident in a reactor chamber. The passivating layer is deposited as a non-reactive (inert) coating on surfaces where parasitic deposition may occur by remnants of a precursor chemical used to deposit the film layer remaining on the surfaces of the chamber. The passivating layer is non-reactive with one or more precursors used to deposit the film layer on the substrate. In one embodiment Al
2
O
3
is used as a passivation layer for deposition of film layers of high-k dielectrics, ZrO
2
and HfO
2
.
REFERENCES:
patent: 4493142 (1985-01-01), Hwang
patent: 5728629 (1998-03-01), Mizuno et al.
patent: 5843239 (1998-12-01), Shrotriya et al.
patent: 6251793 (2001-06-01), Wicker et al.
patent: 6420279 (2002-07-01), Ono et al.
patent: 2003/0049372 (2003-03-01), Cook et al.
Londergan Ana R.
Ramanathan Sasangan
Seidel Thomas E.
Winkler Jereld
Blakely , Sokoloff, Taylor & Zafman LLP
Genus Inc.
Ghyka Alexander
LandOfFree
Passivation method for improved uniformity and repeatability... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Passivation method for improved uniformity and repeatability..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Passivation method for improved uniformity and repeatability... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3201771