基于各向同性干法刻蚀的大面积悬空Al膜制备

热声传感器随着多孔硅的热致超声发射现象的发现越来越受到关注。热声传感器通过改变器件表面热量而在周围空气中产生交变压力，从而向外发出声波。热声传感器的关键器件是悬空金属薄膜。制备大面积悬空薄膜释放有一定的难度，需要考虑金属薄膜本身的应力与粘附效应。该文提出了两种基于各向同性干法刻蚀的制备金属薄膜的方法，利用XeF2/SF6制备悬空Al膜。由于XeF2与SF6气体刻蚀硅时对于Al有较高的选择比，XeF2对于硅是各向同性刻蚀且有很高的刻蚀速率，而通过设置感应耦合等离子体（ICP）刻蚀机的参数也可利用SF6达到各向同性刻蚀。基于上述特点制备了悬空Al膜,设计相应的制备流程，探索XeF2刻蚀机与ICP刻蚀机合适的刻蚀参数。所制备的悬空Al膜平整、无杂质，具有良好的形貌。

Fabrication of Large Area Suspended Al Membrane Based on Isotropic Dry Etching

The thermo acoustic sensors are getting more and more attention with the discovery of thermal induced ultrasonic emission phenomenon from the porous silicon. The thermo acoustic sensors generate the alternating pressure in the surrounding air by changing the heat of the surface of the device, thereby emitting sound waves outward. The suspended metal film is the key component of the thermo acoustic sensor. However, it is difficult to prepare and release the large area suspended film and it is necessary to consider the stress and adhesion effect of the metal film itself. In this paper, two methods based on the isotropic dry etching for fabricating metal thin films are proposed, and the suspended Al membrane is fabricated by XeF2/SF6. Because the XeF2 gas has a higher choice ratio for Al while etching silicon, and for silicon, it has a high etching rate for isotropic etching. By setting the parameters of ICP etching machine, SF6 can also be used for isotropic etching. The suspended Al membrane is fabricated based on the above mentioned characteristics. The corresponding preparation process is designed and the appropriate etching parameters of XeF2 etching machine and ICP etching machine are explored. The prepared suspended Al membrane has a smooth, free of impurities and has good morphology.