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Melt-based patterning for electronic devices

Melt-based patterning for electronic devices description/claims

The present invention is related to a process for fabricating an electronic device having a pattern formed on a surface by a deposition material. Further, the invention is related to a process for fabricating a field-effect transistor and in particular to high-resolution patterning for RGB displays.

Organic electronic devices and in particular organic light-emitting devices (OLEDs) are commonly manufactured as a sequence of layers deposited on top of each other such as a first electrode on a supporting substrate, several organic and inorganic layers, and a second electrode. So far, OLED technology is lacking a high-resolution patterning method for RGB displays for small molecules. The deposition technologies developed for small molecules so far show limitations for mass production of large-sized displays.

Conventionally, vacuum evaporation is employed as the physical vapor deposition method in forming the organic layers. A common method for patterning of the organic layers e.g. for red, green, and blue emitting sub-pixels in a full-color display, is the shadow mask technique. However, this technique is limited in size, resolution of the panel, and the individual fill-factor of the pixel. For example, shadow mask technology becomes extremely complicated in particular for small feature sizes. The material deposition during the process requires regular mask cleaning steps which delay the manufacturing. Thermal expansion of the mask during the deposition limits the precision and aperture ratio. Moreover, repeatedly necessary mask alignment is time consuming and reduces yield.

A method used for patterning polymer light-emitting devices is ink-jet printing of dissolved polymers as described in U.S. Pat. No. 6,087,196. This method of dispensing a liquid solution is not suitable for multi-layer OLEDs based on small molecules because previously deposited layers are re-dissolved and intermixed by the sequential deposition of multiple layers from different solutions. When small molecules are heated some of the small molecules sublime directly, while others first melt and then evaporate. Therefore a new way of depositing such molecules is needed. It follows that there is still a need in the art for improved patterning of structures for the fabrication of semiconductor devices, sensors, biochips, and displays using organic and/or inorganic active or biological layers.

An aspect of the present invention is to provide methods and apparatus for the fabrication of semiconductor devices, circuits, sensors, biological patterns, biochips, and monochrome and/or color displays using organic and/or inorganic active or biological layers. It involves the deposition of molecules, oligomers or nanoparticles by a phase-change printing or spray technique and the fabrication of organic light-emitting devices (OLEDs), color displays and other semiconductor devices.

In an example embodiment of the present invention, there is provided a process for fabricating an electronic device having a pattern formed on a surface by a deposition material. The process comprises the steps of heating and applying a pressure to the deposition material to form a melt, and depositing the melted deposition material on the surface with a phase-change printing technique or a spray technique. Thereby the melted deposition material solidifies on the surface, i.e. when it reaches the surface.

In an other example embodiment of the present invention, a field-effect transistor, also referred to as a thin-film field-effect transistor, is made by a process comprising the steps of forming source and drain contacts on a substrate; heating and applying a pressure to a deposition material to form a melt, the deposition material comprising an organic semiconducting material; depositing the melted deposition material onto the substrate with the source and drain contacts by one of a phase-change printing technique, and a spray technique, wherein the melted deposition material solidifies on the substrate and forms an organic semiconducting layer; forming an insulating layer on the organic semiconducting layer; and forming a gate contact on the insulating layer.

It is also possible to form the source, drain, and gate contacts as well as the insulating layer by the phase-change printing or spray technique. This has the advantage that the whole device can be fabricated by the disclosed process.

Embodiments of the invention are described in detail below, by way of example only, with reference to the following schematic drawings, in which:

FIG. 1 illustrates a phase diagram of a one-component system;

FIGS. 2 a-c illustrate steps for forming a pattern on a surface by deposition of a deposition material using a pressure chamber in accordance with the present invention;

FIGS. 3a, b show schematic illustrations of a formation of organic light-emitting devices;

FIG. 3c shows a schematic illustration of a formation of an RGB display;

FIG. 5 shows a schematic illustration of a formation of a field-effect transistor; and

FIG. 6 illustrates a printing principle.

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