| 摘要 |
A method and apparatus whereby etching of a sacrificial silicon dioxide (Si02) portion 18 in a microstructure 5 such as a microelectro-mechanical structures (MEMS) by the use an etchant gas, namely Hydrogen Fluoride (HF) vapour, is performed with greater selectivity to other portions within the MEMS, and in particular portions of silicon nitride (Si3N4) 17. This is achieved by the addition of a secondary non-etchant gas suitable for increasing the ratio of difluoride reactive species (HF2- and H2F2) to monofluoride reactive species (F-, and HF) within the HF vapour. The secondary non-etchant gas may comprise a hydrogen compound gas selected from a group of compounds comprising hydrogen (H2), ammonia (NH3), methane (CH4) ethane (C2H6) and mixtures thereof. The ratio of difluoride reactive species (HF2- and H2F2) to the monofluoride reactive species (F-, and HF) within the HF vapour can also be increased by setting the etch operating temperature to 20°C or below. Also disclosed (figure 1) are details of a vapour phase MEMS etching apparatus which comprises a process chamber (3, fig 1) for receiving the silicon dioxide to be etched, a hydrogen fluoride (HF) vapour source (6 fig 1), and non-etchant gas source(s) (7,10b, figure 1). Gas lines and flow controllers 11 control the quantity of suitable gases flowing to the process chamber. A vacuum pump 4 is further connected to the process chamber. The method may also comprise providing the process chamber with a catalyst such as water vapour 8. |
