Laser resist transfer for microfabrication of electronic devices

Abstract

A method for forming a resist pattern on a substrate (18) places a donor element (12) having a layer of thermoresist material proximate the substrate. A gap is maintained such that the surface of the layer of thermoresist material is spaced apart from the surface of the substrate by a number of spacing elements. Thermal energy is directed toward the donor element (12) according to the resist pattern, whereby a portion of thermoresist material is transferred from the donor element (12) across the gap by ablative transfer and is deposited onto the substrate (18) forming the resist pattern.

Description

CROSS REFERENCE TO RELATED APPLICATIONS [0001] Reference is made to commonly-assigned copending U.S. patent application Ser. No. ______ (Attorney Docket No. 89243 / RLO), filed herewith, entitled PATTERNING OLED DEVICE ELECTRODES AND OPTICAL MATERIAL by Newman et al.; and U.S. patent application Ser. No. 10 / 944,586, filed Sep. 17, 2004, entitled METHOD OF FORMING A STRUCTURED SURFACE USING ABLATABLE RADIATION SENSITIVE MATERIAL, by Ali et al., the disclosures of which are incorporated herein. FIELD OF THE INVENTION [0002] The present invention relates, in general, to fabrication of microelectronic devices and in particular to fabrication of microelectronic devices using a dry process with a resist formed by laser transfer. BACKGROUND OF THE INVENTION [0003] Lithographic patterning techniques have been employed in conventional fabrication of microelectronic devices, including thin film transistor (TFT) arrays for flat panel application. Conventional photoresist lithographic techniques ...

AI Technical Summary

Benefits of technology

[0032] The invention and its objects and advantages will become more apparent in the detailed description of the preferred embodiment presented below.

Problems solved by technology

Because of the very different nature of processes carried out in each of these steps, it would be difficult and costly to combine steps (i)-(v) in any type of automated, continuous fabrication system or apparatus.

Among disadvantages of conventional photoresist use is the requirement for careful control of ambient illumination until curing is complete.

However, in spite of these advantages, some performance drawbacks remain.

Adhesive transfer, used in the methods of each of these disclosures, has inherent limitations for maintaining precise tolerances.

FIG. 2 shows a familiar problem with adhesive transfer.

This problem occurs as donor sheet 70 is pulled away from substrate 18.

One of two problems is possible, however, as illustrated in FIG. 2.

A second possible problem relates to a portion of the adhered resist transfer layer 68 that is not perfectly affixed to substrate 18, due to some slight surface imperfection for example, or due to excessive thickness or strength of the surrounding un-adhered resist donor on resist transfer layer 68.

However, in some cases, this effect could cause jagged edges of surface features where excessive resist material has been removed.

But because it is not possible to obtain perfect separation between adhered and un-adhered portions of a pattern, adhesive transfer, as proposed in the Burberry et al.

'384, and Toyoda '74705 disclosures, suffers from inherent problems in maintaining precision edge definition.

This, in turn, limits the dimensional resolution that can be obtained for a resist pattern formed using adhesion bonding methods.

A further, significant disadvantage of adhesive transfer relates to overall energy level requirements.

When a donor sheet is in flush contact with a receiver substrate, the laser spot necessarily loses some amount of heat through thermal diffusion.

Thermal diffusion can be particularly troublesome when the receiving substrate is a metal surface with a high thermal conductivity.

Yet other disadvantages of adhesive transfer relate to the need for intimate, planar surface contact between donor and receiver substrate.

The presence of any type of surface features on the receiver surface tends to separate the donor from the receiver surface, resulting in less-than-ideal bonding conditions for precision transfer using adhesive transfer techniques.

Similarly, dust or dirt particles, inevitable even in controlled “clean room” environments, may settle between the surfaces of the donor and receiver substrate.

Imperfect adhesion bonding caused by dust or other particulate can have a pronounced effect, resulting in a drop-out near the point of contact.

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