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Computers & Semiconductor IC Products
SPUTTERING TARGET MATERIALS FOR LIQUID CRYSTAL PANELS
Overview
The
liquid crystal display (LCD) market has expanded as the range of
applications for these devices increases. As the increased use of
liquid crystal in TVs demonstrates, it is expected that demand for
large screens will grow steadily.
Current State of the Technology
Moving
away from conventional Cr- and Mo-based materials for source/drain
metal wiring for signal transmission within TFT devices and metal
gate electrodes, manufacturers of large screens are increasingly
adopting Al-based materials (typically Al) with low wiring resistance.
As a result of significant advances in multiple pattern technology using large glass substrates developed to reduce large-screen manufacturing costs, the technology for the production of large, integrated target materialsÑthe materials for forming the membrane used in multiple pattern technologyÑis becoming vital. Because of this, demand for large integrated Al-based target materials has grown rapidly.
As a result of significant advances in multiple pattern technology using large glass substrates developed to reduce large-screen manufacturing costs, the technology for the production of large, integrated target materialsÑthe materials for forming the membrane used in multiple pattern technologyÑis becoming vital. Because of this, demand for large integrated Al-based target materials has grown rapidly.
Product Explanation
The products introduced here are large integrated, pure Al
target materials made with a special manufacturing technology
that minimizes splash defects during the forming of Al membranes.
| Problems
with membrane formation using sputtering |
A current major problem with membrane formation using Al sputtering is lower yield rates due to splash defects. |
|---|---|
| Nature of the problems | Because the fusion
point of the Al itself is low, during the sputter
forming of the membrane small areas of the Al melt
droplets of liquid Al form and attach themselves
to the glass substrate so that the following three
causes of defects in target material quality arise:
Currently, splash defects arising from problems 1 and 2 occur frequently in melted and cast products, the main materials of Al targets. |
| How Hitachi Metals' pure Al target materials solve these problems | Hitachi Metals' pure Al target is a flawless, fine-grained target material created by pressurized sintering with the HIP (hot isostatic pressing) method, using low-oxygen powder as a starting material. In addition, we have cut the quantity of oxygen, traditionally a problem in powder sintering, to 200ppm or under. This is half the usual ratio to powder. |
Comparisons
Chart 1 is a comparative overview of Hitachi Metals' materials
and conventional melting and casting materials. Figure 1 compares
base-material soundness and microstructure. Hitachi Metals'
materials show no increase in comparative resistivity through
increased oxygen volume, which evaluations show to be a customer
concern,and generally perform well in the comparison.
Chart 1: Comparison of Hitachi Metals' new materials and others
| Manufacturing method | Material soundness (ultrasonic flaw detection) | Average crystal grain size (μm) |
Oxygen quantity (ppm) |
|
|---|---|---|---|---|
| Hitachi Metals' materials |
Powder HIP | 99.98% | 38 | 170 |
| Conventional materials (of rival companies) | Melting/Casting | 97.63% | 400 | 30 |
Figure 1: Comparison of soundness and microstructure of Hitachi
Metals' products
and other conventional materials
and other conventional materials
| Material soundness (ultrasonic flaw detection) |
Microstructure | |
|---|---|---|
| Hitachi Metals' products |
 |
 |
| Conventional materials (of rival companies) |  |
 |
