Columbia University

Technology Ventures

High device-to-device uniformity in thin film transistors

Technology #m02-012

Thin film transistors are important components of advanced technological consumer products such as LCD displays. Thin film transistors need to have high device-to-device uniformity to ensure optimal functionality. This is increasingly challenging in low-temperature polycrystalline silicon processes because the inherent randomness of grain boundaries contributes to troublesome off-current. This technology provides a solution to this problem by proposing an alternative alignment of the microstructure relative to the channel region. With some control in patterning, this may decrease the spread in the number of perpendicular grain boundaries. The end result is large device-to-device uniformity and improved performance.

Adjusting microstructure alignment relative to channel region improves uniformity and performance of thin film transistor devices

There are two aspects to the problems with small-grain thin film transistors: periodicity, and location control. Lithography is one possible way to induce periodicity in films, but would naturally require excessively precise location control. This adds unreasonable complexity and cost. Instead, periodicity can be established by patterning laser beams in an optics-based method known as sequential lateral solidification. This controls the periodicity of long grain boundaries, but not short ones. This technology aims to reduce the number of perpendicular grain boundaries with a tunable tilting of the periodic microstructure relative to the channel region. This has been demonstrated in 2-shot material, n-shot material, and 2n-shot material.

Lead Inventor:

James Im, Ph.D.

Applications:

  • Low temperature polycrystalline silicon processes
  • Thin film transistors
  • Liquid crystal displays

Advantages:

  • Simple procedure
  • Improved device-to-device uniformity
  • Improved performance

Patent Information:

Patent Issued (US 7,160,163)

Tech Ventures Reference: IR M02-012