Problem
One of the most common defect type in industrial fabrication of electrically conductive micro and nano structures are the open-defects, where locally electrically conductive material is missing. For example, in ramping-up production line of thin-film-transistor (TFT) liquid crystal display (LCD) the quality control reject can be as high as 50%!
Example of open defect in an electrically conductive structure.
Market segments where open-defects are present:
- TFT-panels for LCD and Organic Light – Emitting Diode (OLED) displays
- integrated circuits (IC)
- printed circuit boards (PCB)
- multichip modules (MCM)
Current solution
Existing technologies for repairing of open-defect are: (a) focus ion beam (FIB) and (b) laser chemical vapor deposition (LCVD). Below a comparison of current market solutions with the method developed by XTPL S.A.*:
| Parameter | FIB | LCVD | XTPL* (initial lab results) |
Impact on |
| Minimal feature size [um] | <0.05 | >5 | 0.2–1 | flexibility of process |
| Deposition rate [um3/s] | 0.05 | 10 | 50 | Throughput |
| Maximal line length | <100um | mm range | cm range | flexibility of process |
| Vacuum chamber required | YES | YES | NO | process cost and throughput |
| Toxic/ dangerous gases/media required | NO | YES | NO | process cost and throughput |
| Surface damage | YES | YES | NO | flexibility of process |
| Price | $$$ HIGH |
$$ MEDIUM |
$ LOW |
process cost |
XTPL Method
XTPL approach is based on a guided assembly of nanoparticles. During the printing process, nanoparticles chaotically distributed in a liquid solution (ink) are guided by the external electric field and form very narrow electrically conductive lines/structures.
The technology is protected by international patent application.
XTPL Technology
The width of lines printed using the dielectrophoretic force ranges from 200nm to 3µm. Here we give examples of silver electrically conductive lines on a glass substrate.
Example of an open defect using XTPL printing. Here a 20µm gap is bridged using the XTPL printing of a 1µm (left) and 5µm (right) wide silver line.
XTPL printing method enables printing of very long lines/structures. Electrically conductive lines of 2cm length and 1um width were demonstrated, with line resistance of below 3Ohm/µm.
Initial current load tests show that the XTPL repaired defects can conduct current up to 4mA. The current load resistance can be increased up to 10mA.
XTPL develops a complete solution to print submicron electrically conductive lines/structures. This includes proprietary technology, design and construction of the unique XTPL print-head, printer and the formulation of inks.
