Spectroscopic sensor including interference filter unit having silicon oxide cavity

A spectroscopic sensor comprising:

• an interference filter unit, having a cavity layer and first and second mirror layers opposing each other through the cavity layer, for selectively transmitting therethrough light in a predetermined wavelength range according to an incident position thereof;
• a light-transmitting substrate, arranged on the first mirror layer side, for transmitting therethrough light incident on the interference filter unit;
• a light-detecting substrate, arranged on the second mirror layer side, for detecting the light transmitted through the interference filter unit;
• and
• a first coupling layer arranged between the interference filter unit and the light-transmitting substrate;
• wherein the cavity layer and the first coupling layer are silicon oxide films,
• the thickness of the cavity layer varies between the first and second mirror layers,
• the thickness of the first coupling layer varies such that the light-transmitting substrate and the light-detecting substrate are arranged parallel to each other,
• the cavity layer has a filter region held between the first and second mirror layers, and a surrounding region continuously surrounding the whole perimeter of the filter region as seen in a direction in which the light-transmitting substrate and the light-detecting substrate oppose each other,
• the cavity layer is formed continuously over the filter region and the surrounding region,
• an entire face on the light-transmitting substrate side of the surrounding region has substantially the same height as a part of a face of the filter region on which the first mirror layer is formed located closest to the light-transmitting substrate or the entire face on the light-transmitting substrate side of the surrounding region is positioned nearer to the light-transmitting substrate than the part,
• the filter region overlaps with a light-receiving unit of the light-detecting substrate and the surrounding region does not overlap with the light-receiving unit as seen in the direction in which the light-transmitting substrate and the light-detecting substrate oppose each other, and
• the thickness of the filter region varies between the first and second mirror layers.