Patent Application
20070210420
Traditionally, patterning of semiconductor-oriented devices is accomplished by using photolithography. However, such patterning of devices in which there is a thin metal film on a plastic substrate can be disadvantageous. In particular, the photolithographic process can be very slow for such devices.
Therefore, more recently, laser delamination has been employed to pattern thin metal films on plastic substrates. Laser delamination is advantageous because it can be performed more quickly than traditional photolithography. However, laser delamination is disadvantageous in that it roughens the surfaces of the channels formed during patterning, including the surface of the underlying exposed plastic substrate.
The drawings referenced herein form a part of the specification. Features shown in the drawing are meant as illustrative of only some embodiments of the invention, and not of all embodiments of the invention, unless otherwise explicitly indicated.
In the following detailed description of exemplary embodiments of the invention, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration specific exemplary embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention. Other embodiments may be utilized, and logical, mechanical, and other changes may be made without departing from the spirit or scope of the present invention. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is defined only by the appended claims.
A plastic substrate is provided, on which a sacrificial polymer layer and a thin metal film over the sacrificial polymer layer are disposed (102). In one embodiment, part 102 of the method 100 is performed as follows. First, a plastic substrate is provided (104). The plastic substrate may be polyethyleneterephthalate (PET), polyethylenenaphthalate (PEN), polyamide, polyether, polysulfone, polyethersulfone (PES), polycarbonate, polyarylate, polyetherimide, polyetheretherketone (PEEK), polyimide, polyparabanic acid, or another type of plastic substrate.
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Laser-delamination patterning can be performed by selectively exposing the thin metal film, and thus the underlying sacrificial polymer layer, to one or more pulses of a laser. For instance, the laser may be a laser having a wavelength of 248 nm, 308 nm, 355 nm, 532 nm, 1064 nm, at a fluence up to one Joule per square centimeter (J/cm2), in one embodiment of the invention. The laser may be turned on for a length of time equal to a single shot of less than or equal to thirty nanoseconds (ns) in one embodiment.
Therefore, in one embodiment, laser-delamination patterning results in the following. First, the thin metal film is selectively laser-induced exploded (112). Explosion in this context can include and encompass vaporization and decomposition of the thin metal film to cause its removal. At these same locations of the electronic device being fabricated, the sacrificial polymer layer is also selectively laser-induced exploded (114). Likewise, explosion in this context can include and encompass vaporization and decomposition of the sacrificial polymer layer to cause its at least partial removal. It is noted that while parts 112 and 114 are described herein separately, this is for descriptive purposes only. In actuality, the thin metal film is photochemically and/or photothermally ablated at the same time that the sacrificial polymer layer is photochemically and/or photothermally ablated exploded. That is, in the same exposure to a laser, both the thin metal film and the sacrificial polymer layer are removed.
It is noted that this process is unlike the prior art, such as that described in U.S. Pat. No. 6,617,541, issued to Wadman et al. In the Wadman patent, for instance, an underlying “assist layer” is exploded, the explosion of which causes removal of the overlying thin metal film. That is, in Wadman, the thin metal film is itself not exploded, but rather is removed as a result of the removal of the underlying assist layer. By comparison, in at least some embodiments of the invention, both the thin metal film and the sacrificial polymer layer are exploded via laser inducement.
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It has been found that the presence of the sacrificial polymer layer 204 during the laser-delamination patterning process provides for smoother surfaces of the channel 504 than if the sacrificial polymer layer 204 were absent during the laser-delamination patterning process. These smoother surfaces of the channel 504 include the sidewalls of the channel 504, such as those of the thin metal film 206, as well as the floor of the channel 504, such as that of the plastic substrate 202. For instance, where the thin metal film 206 is aluminum, it has been found that a surface roughness factor known within the art as Rq may be within the range of 20-80 nm without the sacrificial polymer layer 204. However, where the sacrificial polymer layer 204 is present, the surface roughness factor Rq decreases to 4 nm, a reduction in roughness of at least 80%.
Therefore, the sacrificial polymer layer 204 is sacrificial in the sense that it is present just to be at least partially removed during laser-delamination patterning, so that the surfaces of the channel that is formed are smoother than they would otherwise be if the layer 204 were not present. That is, the primary, if not only, function of the sacrificial polymer layer 204 is to be at least partially removed during laser-delamination patterning, to cause smoother channels during the laser-delamination patterning process. The sacrificial polymer layer 204 in at least some embodiments has no other functionality or purpose other than this sacrificial functionality and purpose.
In one embodiment, the heat-absorption characteristics of the sacrificial polymer layer 204 are matched to the wavelength of the laser 502 being used, such that the sacrificial polymer layer 204 is heated and ultimately vaporized or otherwise decomposed during laser-delamination patterning. However, it has been found that, in another embodiment, the heat-absorption characteristics of the sacrificial polymer layer 204 may be specifically not matched, or unmatched, to the wavelength of the laser 502 being used. As such, the sacrificial polymer layer 204 is not directly heated by the laser 502. In this embodiment, too, however, it has been found that the utilization of such a sacrificial polymer layer 204 nevertheless results in smoother channels being formed.
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It is noted that although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that any arrangement calculated to achieve the same purpose may be substituted for the specific embodiments shown. This application is intended to cover any adaptations or variations of the disclosed embodiments of the present invention. It is thus manifestly intended that this invention be limited only by the claims and equivalents thereof.
