The fabrication of high frequency fundamental crystals by plasma etching

A method is described for manufacturing AT-cut high-frequency-fundamental crystals up to 150 MHz. Individual samples at fundamental frequencies up to 500 MHz have also been fabricated, demonstrating that batch production of crystals with very high fundamental frequencies is also feasible. Plasma etching is used for recessing blanks to the desired thickness. High-quality quartz is essential as the starting material and careful preparation of the blanks prior to plasma etching is required. Examples of electrical parameter measurements on production batches of crystals at fundamental frequencies between 60 MHz and 150 MHz are given, together with results from sample crystals at frequencies up to 500 MHz