A production process of silicon sensor elements for a fibre-optic pressure sensor

Silicon micromachining has been used for small-scale production of sensor elements for a fibre-optic pressure sensor. Each sensor is integrated with a guide wire for insertion of catheters during balloon dilatation of constricted arteries of the heart. The manufacturing process of the sensor elements is described in detail. It consists of four lithographic steps and five etch steps. The sensor elements have been manufactured using anisotropic etching of slowly dissolving {100} silicon planes in KOH. The sensor elements are supported by a carrier for use of a micromanipulator when assembling the sensor. The dimensions of the sensor elements are 55 μ × 76 μm × 1240 μm, and the resulting guide-wire pressure sensor has an outer diameter of 0.36 mm. Critical element dimensions determing the sensor performance have been identified, and resulting etch depth variations are presented. It is shown that the sensor elements could be produced with sufficient accuracy using time etching of {100} planes. The yield of the total manufacturing process is about 40%. The sensor is a commercial product and the production volume of sensor elements is 10 000 units/year.