FI91806C - Surface Plasma Resonance Sensor with Integrated Optics for Measurement of Liquids and Gases and Method of Preparation thereof - Google Patents

Description

91 Βϋ6

Surface plasmon resonance integrated optics sensor for measuring liquids and gases and a method for manufacturing the sensor

The invention relates to an integrated optics sensor based on surface plasmon resonance according to the preamble of claim 1 for measuring liquids and gases.

The invention also relates to a method for manufacturing a sensor.

10 Surface plasmon resonance sensors implemented with micro-optics are known. However, these are difficult to manufacture and therefore expensive. The path of light in these solutions is mainly air and this causes a complex scattering mechanics to achieve the correct alignment.

15 Known sensor manufacturing methods are described in references / 1 /, / 3 / and / 4 /. These methods are based on the growth of three light-conducting insulating layers on a silicon wafer. Ion-exchanged glass waveguides according to the method described in reference / 5 / can also act as a passive planar waveguide structure.

The object of the present invention is to provide a completely new type of sensor based on surface plasmon resonance and a method for manufacturing the same.

The invention is based on the fact that the sensor is manufactured miniaturized by means of integrated optics on a silicon substrate, so that the most important biosensor components 25 are placed in a planar waveguide on a single silicon chip, whereby a plane waveguide acts as a radiation path.

The manufacturing method according to the invention, in turn, is based on the fact that the connection surface of the planar waveguide is formed by marking V-30 grooves on the surface of the silicon chip in the direction of the crystal direction of the silicon chip and cutting the chip in the direction of the grooves.

More specifically, the sensor according to the invention is characterized by what is set forth in the characterizing part of claim 1.

91806 2

The manufacturing method according to the invention, in turn, is characterized by what is stated in the characterizing part of claim 4.

The invention provides considerable advantages.

5

The solution according to the invention offers possibilities to manufacture a biosensor which is simple, small and inexpensive and which is the most sensitive of the methods using the electromagnetic evanecent wave. The integrated optics according to the invention on a silicon substrate enable the miniaturization of optical functions by monolithic integration, in which as many optical components as possible, including the active region of the surface plasmon resonance, are placed in a planar waveguide on a single silicon chip. In the sensor according to the invention, the microelectronics processing devices and steps can be applied to the sensor technology. The plane wave technology used guarantees very good reproducibility and yield in manufacturing. The light switching optics to the sensor circuit of the integrated optics can be made very reliable because the alignment accuracy requirements are not critical. Silicon wafer is cheap, has a large surface area and has very good optical and mechanical properties as a base material. The cutting of the disc can be done industrially, V-groove technology also offers a good solution. The average alignment accuracy of the passive subcomponents is 20 very good (approx. 0.2 μιη) inside the silicon chip. The number of mechanical parts is decisively reduced compared to a sensor based on micro-optics.

The invention will now be examined in more detail with the aid of exemplary embodiments according to the accompanying figures.

25

Figure 1 shows a perspective view of one sensor according to the invention.

Figure 2 shows a detail of the sensor of Figure 1.

Fig. 3 shows a plan view of the step of manufacturing the V-grooves of the sensor according to the invention.

I: 91 8ΰ6 3

Fig. 4 shows a side view of section A-A of the manufacturing step according to Fig. 3.

According to Figure 1, the component according to the invention comprises a refractive index structure of a planar waveguide 5, which has been manufactured, for example, by the methods according to references (1,2,3 or 4). The refractive index structure is optimized for the uniform wavelengths used. The polarized light 2 is guided from the laser 11 directly by means of a slit 3 or a fiber or V-groove acting as a point source to a planar waveguide 1, where it propagates through a large numerical aperture to a surface of a total reflective ellipse 4 etched perpendicular to the silicon wafer 5. The light directed at and reflected from the ellipse 4 excites the surface plasmon resonance at a certain value of the angle of incidence in the vaporized metal foil 6 of the planar waveguide, which is suitably gold (Au), silver (Ag) or aluminum (Al). The thickness of the metal film 6 is suitably 50 to 150 nm. The resonance is very sensitive to changes in the refractive index on the surface of the film 6, which can be observed as the loss of reflection at a certain angle of incidence. The reflected beam is directed by means of a total reflective parabola 8 to a CCD structure 9 which hybridizes to the edge of the silicon chip 5, which is further connected to the electronics.

Figure 2 shows an enlarged schematic view of the light switching point 10 at the edge of the silicon chip 20 5 in the resonant region. The light switching point 10 is initially etched by anisotropic reactive ion etching (RIE) in the same mask phase together with the other substructures in a planar waveguide parallel to the drawing plane in the figure. This procedure does not result in alignment errors. That is, the focal point of the beam coming from the ellipse 4 is aligned to the correct position by etching the side of the barrel 5 intended as the coupling point 10.

According to Fig. 3, a flat and perpendicular surface along the connection point 10 can also be formed in the silicon-based component by cutting the silicon chip according to the figure. The basic idea is to use known KOH-treadable V-grooves 20 30 to cut the silicon chip 5 and at the same time the planar waveguide at the right place, whereby in the direction of the V-grooves 20 in the figure the silicon substrate and the plane waveguide edge are sharply cut at about 90 °. With this method, compared to reactive ion etching (RIE), the non-idealities of the slope and especially the flatness of the 91806 4 planar waveguide edge do not become a problem in the critical resonance region 10, because the unevenness widens the intensity intensity measured with the CCD structure and worsens the surface area multiplier.

5

Fig. 4 shows the structure of Fig. 3 in section A-A after cutting. The width and distance between the V-grooves 20 are experimentally optimized. The direction of the V-grooves is selected according to the <100> crystal direction of the silicon wafer 5. In the example of Figure 3, the width of the groove 20 is 50 μπι and the distance between the grooves is about 100 μπα.

10

According to Fig. 4, the angle between the planar waveguide and the crystal plane <111> is 55 ° in the KOH viewfinder.

A metal film 6 of the desired thickness is then deposited. The metal film and the edge of the planar conductor 15 form a surface plasmon resonance region suitable for measuring changes in the refractive indices of a biological substance, liquid or gas. A liquid, gas or biological substance on the surface of the metal film 6 changes the resonant angle, which is reflected in a decrease in intensity at the corresponding reflection angle. According to Figure 1, the intensity positions corresponding to the different reflection angles and the changes in position 20 are determined by means of the total reflective parabola 8 and the CCD structure 9.

References: 25/1 / G. Grand, S. Valette, G. J. Cannell, J. Aamio, M. del Giudice, "Fiber Pigtailed

Silicon Based Low Cost Passive Optical Components ", Proc. Of the 16th European Conference on Optical Communication, Amsterdam, The Netherlands, pp. 525-528 (1990).

30/2 / P. Heimala, J. Aamio, U. Gyllenberg, H. Ronkanen, "Evaluation of LPCVD

PSG layers for applications in integrated optics ", Proc. Of the 14th Nordic Semiconductor Meeting, Aarhus, Denmark, Technical University of Denmark & University of l, 91806 5 Aarhus, pp. 194-197 (1990).

/ 3 / J. Aamio: "An Integrated-Optic Polarization Splitter on Silicon Substrate", Proc. Of 14th ECOC, IEE, Brighton, I, p. 34-37 (1988) 5/4 / J. Bismuth, P. Gidon, F. Revol, S. Valette, "Low-loss ring resonators fabricated from Silicon based integrated optics technologies", Electronics letterrs, 27, p. 722-724 (1991) 10/5 / A. Tervonen, "Optical waveguides by ion exchange in glass: Fabrication processes for integrated optics applications", Commentary Physio-Mathematicae 109/1990, Dissertations No 28, The Finnish Society of Sciences and Letters. ·

Claims (4)

1. Surface plasmon resonance based sensor with integrated optics for measuring liquids and gases, comprising - means (11) for generating polarized electromagnetic radiation (2), - a passage (1) for radiation (2), such as the polarized electromagnetic radiation (2) can be led to, - a point source (3) for converting the polarized electromagnetic radiation into a point form, a directing device (4) with which the point-shaped electromagnetic radiation can be directed to a coupling stall (10), - one behind the coupling stall (10) formed a metal foil (6), a directional means by which the electromagnetic radiation directed at the coupling number (10) can be directed to be detected, and - a detection device (9), by means of which the optical properties of a material behind the metal foil (6) can be determined from the radiation reflected therefrom, characterized therefrom, that - the passage (1) for the radiation is constituted by a plane wave conductor, and The point source (3), the alignment device (4), the alignment device (8) and the detection device (9) are formed on the same uniform silicon piece (5) in the planar conductor (1). 91806 9 2. Sensor according to claim 1, characterized in that the alignment device (4) is a total reflecting ellipse surface and the directional device (8) is a total reflecting parabola surface. 3. Sensor according to claim 1, characterized in that the detector (9) is a CCD cell. 4. A method of manufacturing a sensor according to claim 1, characterized in that the coupling surface (10) of the planar conductor (1) is formed so that V-grooves (20) are wetted on the surface of a silicon piece (5) parallel to the silicon bit (5) < 100> crystal direction and the silicon bit (5) 10 is interrupted in the direction of the grooves (20).