JPH0599745A - 1-chip type spectrometer - Google Patents

Abstract

(57) [Summary] [Purpose] An ultra-compact spectroscope is obtained by providing the function of the spectroscope with one chip. [Structure] A metal film filter having a large number of holes with different hole diameters for each element is provided on the surface of each light receiving element on the chip so that only incident light having a cutoff wavelength of the hole or less can be transmitted, and The spectral distribution of the incident light is obtained by taking the difference between the output signals of the adjacent elements with respect to the incident light with respect to the element.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device having a spectroscopic function, and more particularly to a one-chip spectroscope belonging to a sensor IC.

[0002]

2 and 3 are views showing the principle of a conventional spectroscope, in which 10 and 19 are slits and 11
Is a prism, 12 is a photodetector composed of a photomultiplier or a photodiode, and 13 is a diffraction grating.

The operation of these spectroscopes will be described below. The incident light that has passed through the slit 10 is dispersed by the prism 11 or the diffraction grating 13, the light of a single wavelength is selected by the slit 19, and the light intensity is measured by the light receiver 12. Then, here, by rotating the prism 11 or the diffraction grating 13, arbitrary wavelengths can be selected.

[0004]

As described above, the conventional spectroscope has a problem in that the size of the device becomes large because it uses slits, prisms, diffraction gratings, etc., and it cannot be made lighter or smaller. Further, the rotation of the prism or the diffraction grating must be performed mechanically, and a drive system such as a motor must be used for automatic operation.

The present invention has been made in view of the above problems, and an object thereof is to obtain a one-chip type spectroscope which is small and lightweight and which can be operated only by an electric signal.

[0006]

A one-chip spectroscope according to the present invention forms a light receiving element by forming a metal film having a large number of holes on each element surface of an image sensor spread on a semiconductor chip. In this structure, the spectrum of the incident light is obtained by taking the difference between the outputs of the elements having different hole diameters.

[0007]

In the 1-chip type spectroscope according to the present invention, the hole of the metal film provided on the surface of the light receiving element functions as a waveguide, so that it functions as a filter for electromagnetic waves (incident light) having a cut-off wavelength or longer, As a result, the spectrum of the incident light wavelength can be measured by repeating the work of obtaining the difference in transmitted light intensity between the adjacent elements.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 5 is a diagram schematically showing an overall configuration of a one-chip type spectroscope according to one embodiment of the present invention.
Reference numeral 17 is a metal film filter, and 18 is a light receiving element.
The metal film filter 17 is provided on each of the xb light receiving elements 18.

FIG. 1 is a sectional side view of each element (one element) of this one-chip type spectroscope. In the figure, 1 is a hole, 2 is a metal film, 3 is a SiO ₂ film, 4 is a light receiving layer, Reference numeral 5 is a guard ring, 6 is a P-type Si crystal substrate having an N-type channel impurity layer on its surface, 7 is a polysilicon electrode, 8 is Al wiring 8, and 9 is a SiO ₂ insulating film. ₂ film 3, light receiving layer 4, guard ring (N type)
5, a P-type Si crystal substrate 6 having an N-type channel impurity layer on its surface 6, an image sensor composed of a polysilicon electrode 7, an Al wiring 8 and a SiO ₂ insulating film 9) and a metal film in which a large number of holes 1 are formed. 2 is vapor-deposited. Here, the metal film 2 is made of Al, Cu, etc., and has a large number of holes 1.
Is opened by photolithography and etching. The diameters of the holes 1 in one element are all the same, the range of the hole diameter x is determined by the measurement wavelength range, and 0.2 in the infrared part.
It is not less than μm and not more than 0.2 μm in the visible portion. And
In the 1-chip type spectroscope of FIG. 5, each element is composed of the elements having the same structure shown in FIG. 1, and the hole diameter x of each element is from the coordinates (1, 1) to (a, b). The wavelength resolution is gradually changed, and the wavelength resolution is determined by the hole diameter difference Δx between the elements.

The basic operation of this one-chip spectroscope will be described below. The hole 1 of the metal film 2 shown in FIG. 1 functions as a waveguide, and functions as a filter for electromagnetic waves (incident light) having a cutoff wavelength λ _C or more. Then, after the incident light passes through this filter, the light receiving element [coordinates (n, m)
Transmitted light intensity I _{n, m} is observed by the light receiving element located at the position [1], and the immediately preceding element [light receiving element located at the coordinates (n, m + 1)], that is, the light receiving element arranged adjacently The spectrum of the incident light wavelength is measured by sequentially repeating the operation of obtaining the difference from the transmitted light intensity I _{n, m + 1} . Next, the operation when the continuous spectrum light as shown in FIG. 6 (a) is incident on this spectroscope will be described.

Hole radius R of the light receiving element at coordinates (n, m)
_{n, m,} and its adjacent coordinates (n, m + 1) radius R _n of _{elements, m + 1} of the cut-off wavelength of each λ _cn ─, λ _cn ─
_{Assuming +1} , the spectrum of the light transmitted through each filter is as shown in FIGS. 6 (b) and 6 (c). Here, the transmitted light intensity received by the element at coordinates (n, m) and the element at coordinates (n, m + 1) are respectively

[0012]

[Equation 1]

[0013]

[Equation 2]

Therefore, the incident light spectrum λ _cn ─, λ _cn ─
The minute intensity ΔI between ₊₁ is

-Number 3-ΔI _nm = I _{n, m + 1} −I _{n, m} (3)

And the shaded area shown in FIG.

Then, by repeating this operation from the element having the coordinates (1, 1) to the element having the coordinates (a, b), the spectrum shown in FIG. 8 can be obtained.

Next, the hole diameter is set to 1.0 μm to 0.52 μm.
An example of measurement of the incident light spectrum when 25 elements are arranged and m is set to 0.02 μm will be described.

Here, the cutoff wavelength λ _n of each element is as shown in FIG. 9, and a metal hole having a radius of 0.5 μm transmits light having a wavelength shorter than 1.71 μm and transmits light having a wavelength shorter than 1.71 μm. Decay. Of the many cutoff wavelength modes existing in the circular waveguide of radius R, the mode with the largest cutoff wavelength is the TE ₁₁ mode, and λ _C =
It is 3.41a. Here, for simplicity, strength: I
₁ , spectrum: 1.42 μm A case where a single wavelength light is incident will be described.

Table 1 shows the minute intensity ΔI = I _n −I _{n + 1} corresponding to the output of each element and each wavelength.

[0021]

[Table 1]

The spectrum shown in FIG. 11 can be obtained. Then, FIG. 10 is a diagram showing an incident light spectrum, and it can be seen that the spectrum agrees with the spectrum shown in FIG. 11 obtained by the measurement. Where the wavelength step is Δ
It is determined by _{R = R n -R n + 1} .

In such a one-chip type spectroscope of the present embodiment, a metal film which covers the surface of each light receiving element and has a large number of holes in which the diameter of each element is changed stepwise is provided. ,
Electromagnetic waves (incident light) above the cutoff wavelength in each element
Since it functions as a filter for, a difference in the transmitted light intensity between adjacent elements is generated, and by repeating the measurement of this difference for the elements of the entire chip, it is possible to obtain the spectrum of the incident light wavelength, and Since it can be operated only by an electrical signal, it is extremely small and lightweight compared to conventional spectroscopes.

In the present invention, if the metal film of FIG. 1 is vapor-deposited on glass, it can be used as a high-pass filter for light from the visible portion to the infrared portion.

[0025]

As described above, according to the one-chip spectroscope of the present invention, the metal film having a large number of holes on the surface of each element of the image sensor laid on the semiconductor chip has a stepwise hole diameter. Since each of the light receiving elements is formed differently, the spectrum of the incident light wavelength can be obtained by taking the difference in the transmitted light intensity between the adjacent elements in the elements of the entire chip. Since it can be operated by electrical operation without requiring physical operation, it is smaller and lighter than conventional spectroscopes, and it can be formed by existing semiconductor manufacturing methods, so low cost is realized. There is an effect that can be done.

[Brief description of drawings]

FIG. 1 is a sectional side view of one element constituting a one-chip type spectroscope according to an embodiment of the present invention.

FIG. 2 is a diagram showing the principle of a conventional spectroscope using a prism.

FIG. 3 is a diagram showing the principle of a conventional spectroscope using a diffraction grating.

FIG. 4 is a diagram showing how a single wavelength is extracted from incident light split by the prism or diffraction grating shown in FIG. 2 or FIG.

FIG. 5 is a diagram showing an overall configuration of a one-chip type spectroscope according to an embodiment of the present invention.

FIG. 6 is a graph used to explain the operating principle of the present device.

FIG. 7 is a graph used to explain the operation principle of the present apparatus.

FIG. 8 is a graph used to explain the operating principle of the present apparatus.

FIG. 9 is a graph used to explain the operation principle of the present apparatus.

FIG. 10 is a graph used for explaining the operation principle of the present apparatus.

FIG. 11 is a graph used to explain the operating principle of the present device.

[Explanation of symbols]

1 hole 2 metal film filter 3 SiO ₂ 4 light receiving layer 5 guard ring 6 P-type Si substrate 7 polysilicon electrode 8 Al wiring 9 SiO ₂ insulating film 10 slit 11 prism 12 photomal or photodiode 13 diffraction grating 14 spectral image 15 measurement Single spectrum 16 Incident light spectrum 17 Metal film 18 Photodetector 19 Slit

Claims (1)

[Claims] 1. A semiconductor chip comprising a plurality of light receiving elements in which a large number of light receiving elements are arranged in each of vertical and horizontal directions, and the light receiving element comprises a light receiving layer and a light shielding film having a plurality of holes covering the light receiving layer. 1-chip spectroscope, characterized in that the diameter of the hole is changed stepwise for each element so that an output signal between the elements with respect to incident light varies. Spectroscope.