RF Test Gage R&R Improvement
Advanced cell phone architectures require high performance multi-throw RF switches. Reliably measuring the very low RF power levels of the third harmonic signal of these switches is a significant challenge. This paper discusses the use of Gage studies to identify and measure the sources of variation in RF probe measurements. Tester Gage study results are presented. Evaluations of factors including test instrument repeatability, probe card wear, probe tip planarity, probe pressure, and probe placement within the bond pad are presented. The data indicated the repeatability of the test instrumentation was very good. However, the reproducibility needed improvement. The most significant factor in achieving reproducible RF measurements is sufficient probe contact. A method to provide probe operators feedback of sufficient probe contact was developed and implemented. As a result, the Gage study passed. Further, the percentage of die requiring re-test was reduced significantly. INTRODUCTION State of the art multi-throw RF switches need to meet third harmonic performance specifications in the range of -30 to -40 dBm power at RF frequencies in the range of 824 to 915 MHz. -30 and -40 dBm correspond to 1uW and 100nW of power respectively. To provide known good switch die for Skyworks Front End Modules (FEM), the Skyworks pHEMT wafer fab performs RF probe testing on all switch die. Reliably making these low power measurements at high frequencies in a probe test environment requires advanced test instruments and rigid production discipline. The Skyworks Quality System requires Gage studies be performed on all measurement equipment. Further, Skyworks customers can and do request measurement system Gage study results.
Web-Based Business Intelligence for Semiconductor Manufacturing
Business Intelligence (BI) is a relatively new concept that has received a tremendous amount of coverage in recent manufacturing publications. The use of an integrated knowledge base in establishing best business practices is not new, but the demands of very high volume wireless semiconductor manufacturing with high product and process yields, combined with thin profit margins, has intensified effort in this area. This paper includes the architecture of the business intelligence solutions used at Skyworks and details how this integrated system is being used to improve our competitiveness in a global marketplace.
Characterization and Control of Galvanic Corrosion During GaAs Wafer Photoresist Processing
The occurrence of galvanic corrosion on compound semiconductor substrates with exposed metal has been observed as deleterious device effects. 1-7 Noble metals, e.g. gold, platinum, etc., in contact with exposed GaAs can induce undesired galvanic etching during wet process steps and result in surface irregularities that adversely affect yield. This phenomenon can occur when stripping photoresist using an aggressive wet chemistry. Rinsing steps that use de-ionized (DI) water can make matters worse. 1-3,5-7 Control and minimization of compound semiconductor and metal corrosion has received much attention in wafer fabrication. Some facilities have used electrical measurements or SEM (scanning electron microscopy) observations to characterize and alleviate corrosion issues. For photoresist mask strip steps, some facilities avoid problems by choosing a corrosion-safe chemistry, which may not necessarily provide optimum performance. Unfortunately, challenges in removing tenacious organic residues exist, especially from deep ultraviolet (DUV) and hard-baked exposures. Although residue removal typically involves more aggressive chemistries, substrate protection and cleaning efficacy can be achieved. Using novel chemistry formulations and process techniques, galvanic corrosion can be controlled. This paper characterizes GaAs based corrosion near ohmic and gate metal layer features and shows how it varies with the choice of chemistry and the addition of water due to absorption or rinsing.