SRC, Columbia University Discover Why Electronics Fail

In order to understand and control chip defects that cause failures, Semiconductor Research Corp. (SRC) and Columbia University reported today that its researchers have come up with new ways of evaluating and measuring why the advanced insulators in semiconductor chips potentially fail.

This work has the potential to extend the life and increase the reliability of semiconductor chips, SRC and Columbia asserted.

"This is an endeavor to take a truly fundamental approach to these issues. To solve an engineering problem, technologists typically tend to keep building new devices with subtle tweaks based on intuition until they find the solution. Now, we are looking directly at how the fundamental physical properties of the insulator material itself are being affected. By doing so, we believe we can find and fix many of the insulator reliability issues and help extend the lifetime of the world’s most advanced semiconductor chips," explained Dr. Robert B. Laibowitz, senior research scientist at Columbia University, in a statement.

The problem researchers wanted to address concerns the fact that as the wires connecting devices has become smaller and smaller over the decades, the silicon dioxide material used to insulate chip wiring and keep circuits from shorting has resulted in unacceptably slow circuits that consume excessive power in several key applications. Low-k dielectric (LKD) material has replaced silicon dioxide films in these applications and is now widely used in the industry, but while LKDs were implemented to solve the performance and power issues, they created a new problem: the resulting devices had much shorter life spans than devices based on traditional silicon dioxide insulating films.

To combat this, Columbia University researchers, supported by SRC and industry partners, have incorporated optical excitation techniques in their investigation of LKDs to determine electron barrier heights, trap levels and trap densities in LKD thin films and the interfaces between other materials, with new, insightful results.

The researchers said they now have a better understanding of the role of these parameters in defining electrical properties that can help to predict degradation and control leakage of currents contributing to potential breakdown.

"These data will help meet an industry-wide need to understand conduction mechanisms in low-k films, particularly those leading to leakage, time dependent dielectric breakdown (TDDB) and reliability concerns. The problems associated with traps in LKD films are expected to increase in importance as the push to even smaller circuitry and lower dielectric constants continue, and these measurements provide us the best insight available to help solve these problems," said Dr. Scott List, director of Interconnect and Packaging Sciences at SRC.

Further, the research focuses on optical and electrical studies of charge transport and trapping in LKD with samples used in the study consisting of both blanket LKD films on silicon and metal substrates, as well as more complex test structures used in industry reliability studies.

Then, using photo-induced current, laser second harmonic generation and capacitance-voltage measurements, Columbia University graduate student Joanna Atkin determined the density of traps in LKD thin films and their generation dynamics with application of applied field for the first time.

Her work will be extended to an array of films and structures of varying dielectric constant and thickness, varying contact metallurgy and process history.

"As semiconductors migrate to new manufacturing technology nodes and smaller circuitry, further materials analysis will be needed," Laibowitz added.

Columbia University and SRC said they plan to continue this work and extend both the techniques and LKD film advances for future generations of semiconductor manufacturing technology.

Semiconductor Research