Method of making silicon capacitive pressure sensor with glass layer between silicon wafers

A method bonding two silicon wafers to form a capacitive pressure sensor including the steps of:

• forming a first silicon wafer,
• forming a second silicon wafer,
• forming a first capacitive electrode on said first silicon wafer;
• forming a second capacitive electrode on said second silicon wafer;
• forming a first and second highly doped electrically semiconductive feedthrough path through the second silicon wafer, so that the first path can be used to contact the first capacitive electrode and the second path can be used to contact the second capacitive electrode;
• forming a first glass layer, with sodium ions and coefficient of thermal expansion close to that of silicon, on the first silicon wafer;
• forming a metal layer on a region of the first glass layer;
• forming a second glass layer on the metal layer and on a region of the first glass layer devoid of said metal layer;
• and
• anodically bonding the first and second glass layers respectively to the first and second silicon wafers in the region of the metal layer and anodically bonding the first and second silicon wafers to each other in the region devoid of said metal layer, wherein the step of anodically bonding includes applying a voltage between the metal layer and the silicon wafers to be anodically bonded to the glass layers, and wherein forming the first and second silicon wafers includes lightly doping the first and second silicon wafers with an n-type carrier.