Coating processes – Direct application of electrical – magnetic – wave – or... – Photoinitiated chemical vapor deposition
Reexamination Certificate
2002-02-19
2003-07-01
Meeks, Timothy (Department: 1762)
Coating processes
Direct application of electrical, magnetic, wave, or...
Photoinitiated chemical vapor deposition
C427S583000, C427S255150, C427S255170, C427S255393, C427S255394, C427S255700
Reexamination Certificate
active
06586056
ABSTRACT:
BACKGROUND OF THE INVENTION
Semiconductor technologies such as flat panel displays and solar applications which involve thin film transistors (TFT) and microelectronic devices such as RAM (memory and logic chips), employ silicon based thin films for various purposes including semiconductor substrates, diffusion masks, oxidation barriers, and dielectric layers. Current manufacturing technologies for producing these films use precursors such as silane (SiH
4
) for thermal low-pressure chemical vapor deposition (LPCVD) or plasma enhanced CVD (PECVD). Unfortunately, the thermal LPCVD methods require temperatures in excess of 700° C., and the plasma assisted methods require use of a vacuum environment.
The use of these thermal and plasma assisted CVD technologies precludes efficient and cost-effective production of silicon based film systems for many applications. The high processing temperatures of thermal CVD methods require large energy input and are incompatible with some semiconductor applications. For example, use of low cost glass substrates in TFT applications requires processing temperatures below 400° C.
Plasma assisted CVD techniques provide a lower temperature alternative to thermal CVD, but they also have several important drawbacks. First, plasma use often causes large hydrogen concentrations in the resulting films, which may lead to film instability and device degradation. Plasma methods may also result in ion bombardment damage to underlying device structures. Finally, plasma assisted techniques require a vacuum environment. The required vacuum equipment makes plasma assisted CVD equipment much more complicated and expensive to manufacture and operate than the equipment typically used for near atmospheric pressure CVD. Additionally, the vacuum environment of plasma assisted CVD is not compatible with film formation for many important semiconductor technologies such as flat panel displays and solar applications, which involve large area substrates and high throughput demands.
Traditional CVD precursors for forming silicon based films have also caused difficulties in semiconductor film deposition. Many known precursors such as silane, disilane, dichlorosilane, and trichlorosilane have minimum film deposition temperatures so high that their use as precursors for semiconductor applications that require low processing temperatures is precluded. Such known precursors also tend to have low film growth rates at their minimum deposition temperatures, which makes CVD methods using these precursors inefficient. Additionally, widely used silane precursors require stringent safety precautions, as they can be pyrophoric, toxic, and corrosive.
Due to the manufacturing requirements of the semiconductor industry and the above-mentioned processing disadvantages of traditional high temperature CVD techniques, plasma assisted CVD techniques, and standard silicon precursors, there exists a need in the art for a low temperature, near atmospheric pressure CVD (APCVD) technique which does not require plasma assistance or use silane or other traditional silicon precursors, such as those listed above. The inventors named in this patent application have developed methods using organic silicon precursors, as described in B. Arkles, “Silicon Nitride from Organosilazane Cyclic and Linear Prepolymers,”
Journal of the Electrochemical Society
, Vol. 133, No. 1 (1986), pp.233-234; and B. Arkles et al., A. Kaloyeros et al., “Atmospheric Chemical Vapor Deposition of Silicon Nitride,” 31 st Organosilicon Symposium, May 29, 1998. The material presented at the Organosilicon Symposium in May, 1998 is also the subject of a co-pending U.S. Patent Application of the same inventors named in the present application. However, the organic precursors can require a somewhat complex synthesis, such that a need still exists in the art for an alternative low temperature, near atmospheric pressure CVD method which employs a simple inorganic precursor. Further, when using organic precursors, generally process parameters have to be controlled to minimize incorporation of low levels of carbon into films.
BRIEF SUMMARY OF THE INVENTION
The present invention includes a method for near atmospheric pressure chemical vapor deposition of a silicon based film onto a substrate, comprising introducing into a deposition chamber at about atmospheric pressure a substrate, an iodosilane precursor in a vapor state, the precursor having at least three iodine atoms bound to silicon, and at least one transport gas. The deposition temperature is maintained within the chamber from about 250° C. to about 650° C. for a period of time sufficient to deposit a silicon based film on the substrate.
In an alternative embodiment, the invention includes a method for near atmospheric pressure chemical vapor deposition of a silicon based film onto a substrate, comprising introducing into a deposition chamber at about atmospheric pressure a substrate, a precursor in a vapor state, and at least one transport gas. Ultraviolet radiation is provided to the chamber such that the radiation reaches an interface between the substrate and the precursor, and the chamber is heated for a period of time sufficient to deposit a silicon based film on the substrate.
The invention further includes a silicon based film formed by chemical vapor deposition at about atmospheric pressure using an iodosilane precursor in a vapor state having a formula (I):
I
(4-n)
SiX
n
(I)
wherein n=0 or 1 and X is selected from the group consisting of a bromine atom, a chlorine atom, a hydrogen atom, and a triiodosilyl moiety.
DETAILED DESCRIPTION OF THE INVENTION
The present invention relates to silicon based films formed from iodosilane precursors and associated methods for the near atmospheric pressure chemical vapor deposition of such films on various substrates. The method of the invention may deposit such silicon based films as a single film on a substrate, or as one of several layers applied to a substrate forming a multilayered structure.
As used herein, silicon based films are those films or coatings which have silicon as a major component. In one embodiment, such silicon based films are silicon nitride films, typically having the chemical formula SiN
x
, wherein x is greater than 0 and preferably no greater than 2. Preferably x ranges from about 1.0 to 1.9. While there may be some impurities in the films of the invention, which are residual components from the deposition reactants, such as iodine, hydrogen, and oxygen, it is preferred that the films have impurity concentrations that are as low as possible, and most preferably, the films are pure. If impurities are present, preferably they are less than 35 at % for hydrogen, 10 at % for oxygen, and 5 at % for iodide. In another embodiment, the silicon based films are silicon oxide films with the formula SiO
y
, wherein y is greater than 0 and preferably no greater than 2.2, and preferably ranges from about 1.8 to about 2.0. These films are also preferably pure, with impurity concentrations for hydrogen and iodide similar to those noted above for forming silicon nitride films. In a third embodiment, the silicon based films are preferably pure silicon films with minor, and preferably no impurities. Any presence of impurities for semiconductor silicon films is preferably less than about 35 at % hydrogen and 3% iodide. Similarly, films of the formula SiN
x
O
y
may also be made in accordance with the invention, where x and y range from greater than 0 to about 2.0 and the sum of x+y is ≦about 3.0. Such films are preferably pure, and, if present, the levels of impurities are as noted above for hydrogen and iodide.
Such films are especially useful on substrates such as semiconductor substrates, for example, silicon and gallium arsenide substrates, having sub-micron features and structures. Preferred semiconductor substrates include, for example, silicon, silicon dioxide, or silicon-nitrogen materials or doped versions or as part of the interconnect architecture. When forming a flat panel, the preferred subst
Arkles Barry C.
Kaloyeros Alain E.
Akin Gump Strauss Hauer & Feld L.L.P.
Gelest Inc.
Meeks Timothy
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