Metal working – Method of mechanical manufacture – Electrical device making
Reexamination Certificate
1998-09-30
2002-08-13
Vo, Peter (Department: 3729)
Metal working
Method of mechanical manufacture
Electrical device making
C029S825000, C029S829000, C029S831000, C029S835000, C029S847000, C083S875000, C083S880000, C083S886000
Reexamination Certificate
active
06430810
ABSTRACT:
TECHNICAL FIELD
This invention pertains generally to the field of fabrication of electronic devices. More particularly, this invention relates to mechanical scribing methods of forming a patterned metal layer which is useful in an electronic device. More specifically, this invention pertains to new methods of forming a patterned metal layer in an electronic device, wherein the metal layer is in contact with an underlying organic polymeric layer (e.g., a conductive or semiconductive organic polymeric layer), which methods comprise mechanically scribing the metal layer with a mechanical scribing instrument to form the patterned metal layer.
BACKGROUND
Throughout this application, various publications, patents, and published patent applications are referred to by an identifying citation; full citations for these documents may be found at the end of the specification immediately preceding the claims. The disclosures of the publications, patents, and published patent specifications referenced in this application are hereby incorporated by reference into the present disclosure to more fully describe the state of the art to which this invention pertains.
With the advent of solid state electronics and the integrated circuit (IC) chip industry, many new methods for the fabrication and processing of solid state electronic devices have been developed. For example, many solid state electronic devices are manufactured by depositing and processing, often sequentially, one or more relatively thin layers of specific materials (e.g., metals, alloys, semiconductors) on a substrate, in order to form a three-dimensional device with the desired electronic function. In many cases, one or more of these layers are “patterned,” that is, fabricated or processed to possess a pre-determined shape within the two-dimensional plane of the layer, to provide additional structure to the device.
Many methods for fabricating patterned layers of specific materials have been developed. One common class of patterning methods may be conveniently classified as photolithography methods. In such methods, selected areas of a surface are protected or “masked” (for example, by a shadow mask pressed against the layer, or by a layer of photoresist processed with the aid of a shadow mask), while the unmasked areas are exposed to processes such as the introduction of impurities, deposition of thin films, removal of material by etching, and the like.
For example, it is often possible to form a patterned metal layer by first pressing a “negative” shadow mask against the surface, and subsequently vapor depositing the metal. The metal is deposited only on the open areas within the shadow mask (hence creating a “positive” image) and not on those areas protected by the shadow mask. Following deposition, the shadow mask is withdrawn, yielding the patterned metal layer. In another method, a continuous metal layer is first deposited, and then coated with uncured photoresist (e.g., a polymeric material which is cured, and thus rendered insoluble in certain solvents, by exposure to an appropriate wavelength of light). A “negative” shadow mask is pressed against the photoresist layer, and the assembly exposed to the appropriate light (e.g., ultraviolet light), thereby curing the photoresist in the open areas within the shadow mask. The shadow mask is withdrawn and the uncured photoresist removed, often using wet chemical methods (e.g., by washing with an appropriate solvent), to expose areas of metal. The exposed metal is then removed, for example, using wet chemical etching methods, and finally the cured photoresist is removed to yield the desired patterned metal layer (with a “positive” image pattern).
Screen printing methods have also been employed in the fabrication of patterned metal layers, typically with the aid of an (often electrically conducting) ink or paste which comprises metal particles. Screen printing methods, which may conveniently be considered refined stenciling methods, typically employ a stencil (akin to the photolithography mask) in combination with a screen (a woven fabric, generally of polyester, nylon, or stainless steel). During printing, a squeegee presses the ink or paste through the screen; where the stencil permits, the ink or paste is applied to the surface to be patterned. The stencil and screen are then removed to yield the printed pattern. Following screen printing with metallic inks and pastes, the layer is often heated, dried, and/or cured.
Recently, laser methods, such as laser scribing, laser ablation, and laser etching, have been used in the fabrication of patterned layers. Typically, in these methods, an intense focused laser beam is rastered across the surface, causing the illuminated material to be vaporized, sputtered, or otherwise removed, leaving a groove, trench, via, trough, or other indentation with a shape determined by the path of the laser beam, and a depth determined by the intensity and raster speed of the laser beam.
Many of these methods are particularly well adapted for the specific materials. For example, for metals which can be easily vapor deposited, photolithography methods employing a negative shadow mask are often very useful. For more refractory materials, such as oxides, nitrides, and many inorganic semiconductor materials, laser ablation methods may be better suited. Whichever method is employed, an important factor for assessing that method's usefulness is the quality of the resulting pattern, determined, for example, by the sharpness of the edges of the pattern and the amount and size of any residual debris.
Many electronic devices comprise a metal layer, often in the form of a relatively thin layer of metal material. Such metal layers, which often function as an electrode for the electronic device, are often patterned. For example, many common electronic devices require a thin patterned layer of conducting metal over an insulating or semiconducting substrate, with a pattern comprising a large number of very narrow electrically isolated bars (e.g., stripes) of metal, each separated by a very narrow gap. In such cases, a particularly useful patterning method would be one which offers both very sharp pattern edges (facilitating narrow metal bars, narrow gaps, and thus a large number of bars per unit distance perpendicular to the bar (i.e., high resolution) with a large “fill factor” (i.e., ratio of active to non-active area)) and residual debris which is small compared to the dimensions of the gap (so that the debris is unlikely to bridge the gap and cause an inadvertent electrical short).
The present invention pertains to new methods of forming a patterned metal layer (which comprise mechanically scribing the metal layer with a mechanical scribing instrument to form the patterned metal layer) and which address many or all of these requirements.
Mechanical scribing methods are well known to those of skill in the art. However, the primary use of mechanical scribing in the manufacture of electronic devices has been to effect separation (e.g., of dice from a larger wafer). Typically, a wafer is first mechanically scribed or scored and subsequently fractured or cleaved along the scribe or score line. Such methods are widely used to effect the separation of partially or completely finished individual electronic devices (e.g., dice) from a larger wafer. For example, large numbers of electronic devices are often fabricated simultaneously on a single wafer; when the fabrication is partially or fully complete, the wafer is scribed or scored (often using mechanical scribing methods), and individual devices are cleaved off.
Methods of separating individual dice from a larger wafer which employ, as a first, step, mechanical scribing to form a scribe line for cleaving have apparently been disclosed (see, for example, Nath et al., 1992, at column 13, where a scribe line through a metallic top layer and partially through an underlying semiconductor layer is described). Methods of cleaving semiconductor diode lasers from a larger wafer which employ a diamond circular saw blade to cut
Kim Paul
Uniax Corporation
Vo Peter
LandOfFree
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