 |
Limitations of Other Lithography and Via-Generation Approaches
The ideal lithography system for production of displays, printed circuit boards, multichip modules, flexible circuits and opto-electronic devices should have the following attributes: high resolution with non-contact imaging, high throughput with low cost of ownership, and ability to handle large substrates in different configurations. The ideal system for generation of vias and ablation of other structures should have the following characteristics: high resolution with clean ablation, high etching speed at low cost of ownership, and absence of damage to the device. In the context of these desirable attributes, we highlight below how all other lithography and via-generation approaches fall short:
Contact Printing
- Frequent contact between mask and substrate causes defects on substrate and degrades mask life, resulting in poor yield.
- Long vacuum pull-down time required to achieve acceptable contact reduces throughput.
- Hard contact renders mask-to-board alignment poor since precise alignment requires relative movement.
- Poor contact limits achievable resolution. Good contact is difficult to achieve over large areas.
Proximity Printing
- Proximity printing requires maintaining small and uniform gap over large areas.
- Variations in proximiy gap cause feature size errors.
Conventional Projection and Step-and-Repeat Imaging
- Conventional, or single-field, projection systems (i.e., those designed for use with substrates that are small enough to fit in the image field of the projection lens) are limited in substrate size capability.
- Step-and-repeat systems have low throughput due to large overhead time (i.e., non-exposure time).
- Steppers also have low yield due to stitching errors, and very high system cost.
Direct Writing
- Focused-beam direct-write systems are fundamentally limited in throughput due to point-by-point, serial nature of exposure.
- Direct-write exposure systems are incompatible with commonly used photoresists.
Via Generation
- Mechanical drilling systems are extremely slow and limited in resolution.
- Reactive ion etching (RIE) processes have very low ablation rates.
- Systems using solid-state lasers have extremely low throughput due to serial (one via at a time) drilling -- a few hundred vias/sec compared to tens of thousands of vias/sec possible with Anvik's projection systems.
- Holographic systems have very complex mask requirements and high system costs.
- In-situ masking techniques are expensive due to requirement of numerous additional process steps.
- Systems using CO2 lasers are limited in application due to thermal nature of material removal process.
From the above summary it is clear that other technologies for lithography and via generation for production of microelectronic and opto-electronic devices suffer from important limitations. Whereas, without a comprehensive performance versus cost analysis one system may appear attractive in a certain aspect and another from a different consideration, ideally one must consider the aggregate performance criteria that fully address the overall cost-effectiveness of different approaches. As described in detail in the Technology section, the Anvik lithography and via-generation systems eliminate all of the limitations listed above, and represent the optimum solution for high-volume manufacturing of microelectronic and opto-electronic products.
|
|
|
