Infrared detector based on suspended bolometric micro-plates

A bolometric array detector for detecting electromagnetic radiation in a predetermined range of infrared or terahertz wavelengths comprising a substrate and an array of bolometric micro-plates for detecting said radiation, said micro-plates being suspended above the substrate by means of support arms,

• wherein said detector comprises a metallic membrane placed on top and around each micro-plate and in which openings are formed;
• wherein the openings formed in the metallic membrane are periodically located in said membrane along at least one predetermined axis with a period equal to or less than
• λ
• n
• ,
• where λ is a wavelength range of the electromagnetic radiation to be detected and n is the average refraction index of a medium that separates each micro-plate from the metallic membrane;
• wherein the width of the openings along the, or each, predetermined axis increases from a location on the metallic membrane positioned above a central area of micro-plate towards the periphery of said metallic membrane, and
• wherein the width of the openings at said location on the membrane satisfies the equation
• 0.25
• <
• W
• 0
• P
• <
• 0.75
• ,
• where W0 is the width at said location and P is the period along the predetermined axis, with the difference in width between two adjacent openings being
• λ
• 200
• ×
• n
• ⁢
• ⁢
• to
• ⁢
• ⁢
• λ
• 20
• ×
• n
• .

A method for manufacturing a bolometric array detector for detecting electromagnetic radiation in a predetermined range of infrared or terahertz wavelengths, said detector comprising an array of micro-plates for detecting said radiation suspended above a substrate by means of support arms and a metallic membrane placed on top and around each micro-plate and separated therefrom by a medium, said method comprising:

• fabricating the substrate;
• depositing a first sacrificial layer on the substrate;
• fabricating the array of bolometric micro-plates over the first sacrificial layer;
• depositing a second sacrificial layer over the array of micro-plates;
• etching the first and second sacrificial layers down to the substrate in order to expose a cut all the way around each micro-plate;
• depositing a metallic layer over the second sacrificial layer and the cuts around the micro-plates;
• forming openings in a portion of the metallic layer placed on top and around each micro-plate, wherein the openings formed in each of said areas are periodically located along at least one predetermined axis with a period equal to or less than
• λ
• n
• ,
• where λ is a wavelength in the wavelength range of the electromagnetic radiation to be detected and n is the average refraction index of the medium, thereby forming said membranes;
• and
• removing the first and second sacrificial layers.

A method for manufacturing a bolometric array detector for detecting electromagnetic radiation in a predetermined range of infrared or terahertz wavelengths, said detector comprising an array of micro-plates for detecting said radiation suspended above a substrate by means of support arms and a metallic membrane placed on the top and around each micro-plate and separated therefrom by a medium, said method comprising:

• fabricating the substrate;
• depositing a first sacrificial layer on the substrate;
• fabricating the array of bolometric micro-plates over the first sacrificial layer;
• depositing a second sacrificial layer over the array of micro-plates;
• depositing a layer of supporting material over the second sacrificial layer;
• etching the layer of supporting material and the first and second sacrificial layers down to the substrate in order to expose a cut all the way around each micro-plate;
• depositing a metallic layer over the layer of supporting material and the cuts around the micro-plates;
• forming openings in a portion of the metallic layer placed on top and around each micro-plate, wherein the openings formed in each of said areas are periodically located along at least one predetermined axis with a period equal to or less than
• λ
• n
• ,
• where λ is a wavelength in the wavelength range of the electromagnetic radiation to be detected and n is the average refraction index of the medium, thereby forming said membranes;
• and
• removing the first and second sacrificial layers.