Austin, Texas-TFA/Leo Burnett Technology Group, Chicago, announced Wednesday the opening of a new office here, a town known within the computer industry as ``Silicon Hills.'' It will become TFA/Leo Burnett's main base in the Southwest, supplanting the agency's Dallas office, which opened in 1996 and will remain in operation as a satellite office. The move was made, explained Sean Bisceglia, TFA/Burnett's CEO, because ``the thriving Austin high-technology sector offers extremely attractive growth opportunities for the organization.'' Scott Murray, president of TFA/Leo Burnett, Austin, will head the new office, which currently has 12 employees to serve its two accounts: Motorola SPS, Austin, and Efficient Networks, Dallas. TFA/Leo Burnett also plans to open an office in San Francisco in the second quarter.