Sensor arrangement with a silicon-based optical sensor and a substrate for functional layer systems
A sensor arrangement with a silicon-based optical sensor, particularly color sensors for colorimetric applications is disclosed. The invention aims to find a novel possibility for suppressing interference ripples occurring in optical sensors when adding substrates with optically functional coatings which permits a simple production without complicated adaptation layers. The sensor passivation is composed of a combination of thin SiO 2 layer in the range of 5 to 10 nm and an antireflection-matched Si 3 N 4 layer and a substrate which carries at least one optical filter is arranged over the sensor passivation and connected to the sensor by means of an adhesive and forms an intermediate space between sensor surface and optical filter which is filled with an optical medium having a low refractive index (n 2 ) and a height variation (Δh) over the associated sensor surface.
1. A sensor arrangement with at least one silicon-based optical sensor comprising:
a sensor passivation comprising a combination of a SiO 2 layer and an antireflection-matched Si 3 N 4 layer, wherein the SiO 2 layer has a thickness in a range from 5 to 10 nm;
a substrate disposed above the sensor passivation, the substrate carrying at least one optical filter and being connected to the sensor by an adhesive in that way to form an intermediate space between a light-sensitive sensor surface and the at least one optical filter; the intermediate space being filled with an optical medium having a lower refractive index (n 2 ) than that of the sensor passivation of the sensor, wherein the optical medium of the intermediate space between sensor passivation and substrate has a height variation (Δh) over the light-sensitive sensor surface,
wherein the height variation (Δh) is formed by tilting the substrate relative to the light-sensitive sensor surface.
2. The sensor arrangement according to claim 1 , further comprising spacers disposed at predetermined positions on the substrate for a defined adjustment of the tilting of the substrate each spacer having a defined height produced by separated filter layers during the process of successive coating of the optical filters having a known layer thicknesses.
3. The sensor arrangement according to claim 1 , wherein the height variation (Δh) is determined by a defined gradation of the substrate relative to the light-sensitive sensor surface in areas of equal size for arranging at least two height-offset filter segments.
4. Sensor arrangement according to claim 3 , wherein the gradation of the substrate is produced by structured glass deposition on the substrate.
5. The sensor arrangement according to claim 1 , wherein the intermediate space comprises an adhesive layer as the optical medium.
6. The sensor arrangement according to claim 1 , wherein the intermediate space comprises an air layer as the optical medium, the air layer being at least partially surrounded by the adhesive.
7. The sensor arrangement according to claim 1 , wherein the tilting is adjusted to generate interference ripples of different frequencies which are mixingly superposed and mutually compensating by selecting a quantity (x) of superposition periods.
8. The sensor arrangement according to claim 7 , wherein the height variation (Δh) for optimal tilting is adjusted according to an equation Δh=x⊕λ/(2n 2 ), where x is the quantity of superposition periods, λ is a wavelength of a light incident to the light-sensitive sensor surface, and n 2 is the refractive index of the adhesive.
9. The sensor arrangement according to claim 3 , wherein the defined gradation of the substrate is adjusted to generate interference ripples of different phase-shifted frequencies which are destructively superposed and mutually compensating.
10. The sensor arrangement according to claim 9 , wherein the height variation (Δh) of the gradation of the substrate for optimal compensation of different-phase shifted interference ripples in a two-filter segment arrangement is determined by the following equation Δh=½λ/(2n 2 ), where λ is a wavelength of a light incident to the light-sensitive sensor surface and n 2 is the refractive index of the adhesive, the intermediate space being filled with an optical medium having a lower refractive index (n 2 ).