Coating processes – Direct application of electrical – magnetic – wave – or... – Ion plating or implantation
Reexamination Certificate
2002-10-23
2004-09-07
Pianalto, Bernard (Department: 1762)
Coating processes
Direct application of electrical, magnetic, wave, or...
Ion plating or implantation
C427S377000, C427S383100, C427S523000, C427S529000, C427S530000, C427S531000, C427S533000, C427S551000, C427S552000, C427S553000, C427S555000, C427S556000, C427S596000
Reexamination Certificate
active
06787198
ABSTRACT:
FIELD OF THE INVENTION
The field of the present invention involves the hydrothermal treatment of photolytically deposited metal and metal oxide films to favorably alter film characteristics at low temperatures for use in semiconductor manufacturing.
BACKGROUND OF THE INVENTION
The semiconductor and packaging industries, among others, utilize conventional processes to form thin metal and metal oxide films in their products. Examples of such processes include evaporation, sputter deposition or sputtering, chemical vapor deposition (“CVD”) and thermal oxidation. Evaporation is a process whereby a material to be deposited is heated near the substrate on which deposition is desired. Normally conducted under vacuum conditions, the material to be deposited volatilizes and subsequently condenses on the substrate, resulting in a blanket, or unpatterned, film of the desired material on the substrate. This method has several disadvantages, including the requirement to heat the desired film material to high temperatures and the need for high vacuum conditions.
Sputtering is a technique similar to evaporation, in which the process of transferring the material for deposition into the vapor phase is assisted by bombarding that material with incident atoms of sufficient kinetic energy such that particles of the material are dislodged into the vapor phase and subsequently condense onto the substrate. Sputtering suffers from the same disadvantages as evaporation and, additionally, requires equipment and consumables capable of generating incident particles of sufficient kinetic energy to dislodge particles of the deposition material.
CVD is similar to evaporation and sputtering but further requires that the particles being deposited onto the substrate and undergo a chemical reaction during the deposition process in order to form a film on the substrate. While the requirement for a chemical reaction distinguishes CVD from evaporation and sputtering, the CVD method still demands the use of sophisticated equipment and extreme conditions of temperature and pressure during film deposition.
Thermal oxidation also employs extreme conditions of temperature and an oxygen atmosphere. In this technique, a blanket layer of an oxidized film on a substrate is produced by oxidizing an unoxidized layer which had previously been deposited on the substrate.
Several existing film deposition methods may be undertaken under conditions of ambient temperature and pressure, including sol-gel and other spin-on methods. In these methods, a solution containing a precursor compound that may be subsequently converted to the desired film composition is applied to the substrate. The application of this solution may be accomplished through spin-coating or spin-casting, where the substrate is rotated around an axis while the solution is dropped onto the middle of the substrate. After such application, the coated substrate is subjected to high temperatures which convert the film into a film of the desired material. Thus, these methods do not allow for direct imaging to form patterns of the amorphous film. Instead, they result in blanket, unpatterned films of the desired material. These methods have less stringent equipment requirements than the vapor-phase methods, but still require the application of extreme temperatures to effect conversion of the deposited film to the desired material.
In one method of patterning blanket films, the blanket film is coated (conventionally by spin coating or other solution-based coating methods; or by application of a photosensitive dry film) with a photosensitive coating. This photosensitive layer is selectively exposed to light of a specific wavelength through a mask. The exposure changes the solubility of the exposed areas of the photosensitive layer in such a manner that either the exposed or unexposed areas may be selectively removed by use of a developing solution. The remaining material is then used as a pattern transfer medium, or mask, to an etching medium that patterns the film of the desired material. Following this etch step, the remaining (formerly photosensitive) material is removed, and any by-products generated during the etching process are cleaned away if necessary.
In another method of forming patterned films on a substrate, a photosensitive material may be patterned as described above. Following patterning, a conformal blanket of the desired material may be deposited on top of the patterned (formerly photosensitive) material, and then the substrate with the patterned material and the blanket film of the desired material may be exposed to a treatment that attacks the formerly photosensitive material. This treatment removes the remaining formerly photosensitive material and with it portions of the blanket film of desired material on top. In this fashion a patterned film of the desired material results; no etching step is necessary in this “liftoff” process. However, the use of an intermediate pattern transfer medium (photosensitive material) is still required, and this is a disadvantage of this method. It is also known that the “liftoff” method has severe limitations with regard to the resolution (minimum size) that may be determined by the pattern of the desired material. This disadvantage severely limits the usefulness of this method.
It is thus evident that the conventional processes for the deposition of blanket films that subsequently need to be patterned invokes the need for several extra costly and difficult processing steps. However, some semiconductor applications, such as applications using a polymer-based substrate, are sensitive to the high temperatures typical in such conventional processes. Therefore a need exists for a low temperature deposition and patterning means of forming films in such applications.
While some of these methods are more equipment-intensive than others and differ in the use of either solution- or vapor-phase methods, such conventional processes for forming metal and metal oxide films is not optimal because, for example, they each require costly equipment, are time consuming, require the use of high temperatures to achieve the desired result, and result in blanket, unpatterned films where, if patterning is needed, further patterning steps are required. A desirable alternative to these methods would be the use of a precursor material that may be applied to a substrate and selectively imaged and directly photolytically patterned to form an amorphous film without the need for intermediate steps. Such films are herein referred to as a film deposited by photochemical metal organic deposition (PMOD™ film), as described in U.S. Pat. No. 5,534,312, which is incorporated herein by reference in its entirety.
Such films may have a certain amount of porosity due to the existence of nanopores in the film matrix. The level of porosity is a factor of the process conditions used, as described in co-pending application entitled “Nanostructured and Nanoporous Film Compositions, Structures, and Methods for Making the Same,” filed Sep. 30, 2002 and incorporated herein by reference in its entirety. As the porosity of such films increases, the density and permitivity decrease. In applications that require a high dielectric constant (k), including embedded capacitors for electronic packaging, future gate oxides for transistors in semiconductor devices, high-density dynamic random access memory (DRAM), piezoelectric micro-or nanoactuators, sensors and microwave tuning devices, this is not preferable. Additionally, in some applications it may be preferable to use crystalline, not amorphous films, such as when ferroelectric behavior is desired (e.g., use as a decoupling capacitor).
Conventional annealing methods that may be used to crystallize such films, also decrease the porosity of such films causing outgassing of the nanopores. However, the current and future industry needs have led to the use of polymer based electronic packaging substrates. Polymer based substrates cannot undergo conventional high temperature (>400° C.) heat treatment needed to increase the de
Madsen Harold O.
Mukherjee Shyama P.
Roman, Jr. Paul J.
Svendsen Leo G.
EKC Technology, Inc.
Morgan Lewis & Bockius
Pianalto Bernard
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