Aerogel films as electronic insulators.

As computer chips get smaller, the need for high-quality component materials grows larger. One of the latest prospects is nanoporous silica, a whisper-light gel that's an exceptionally good electrical insulator. Douglas M. Smith, president of NanoPore in Albuquerque, N.M., reports a simplified method that deposits thin films of this material and enables researchers to control both the thickness and the porosity of the films.

For years, nanoporous silica has been used as bulk thermal insulation in refrigerators and for other industrial applications in a form called an aerogel. Because it contains an abundance of air-filled pores, many only 20 or 30 nanometers in diameter, the gel effectively blocks the transfer of heat.

The pores also make the gel almost as good an electrical insulator as air. The gel could shield chip components from each other to prevent cross talk-interference that becomes increasingly troublesome as the components of electronic devices are crammed closer together. Use of nanoporous silica could also allow chips to run faster, says Changming Jin of Texas Instruments in Dallas. Jin presented his group's research on characterizing the deposited films and making them water repellent.

Unlike silica gels used for thermal insulation, gels for computer chips must be able to dissipate heat rapidly. "As you shrink the device size, the metal mass gets smaller and smaller," Jin says, "but it's going to pass the same current." The increased current density generates more heat, which can damage the electronic components.

To improve heat conduction, Jin and his colleagues are testing denser gels, which have about 75 percent of the gel volume filled with air. Silica gels used for thermal insulation typically have porosities of 95 to 99 percent, he says.