JP2011095137A - Semiconductor optical element and semiconductor optical device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor optical element capable of selectively detecting light with a predetermined wavelength without using a filter structure, and a semiconductor optical device. <P>SOLUTION: A thermal infrared sensor element 100 includes a temperature detection part 5 and an absorption umbrella 10 thermally connected to the temperature detection part, and detects light entering the absorption umbrella. The absorption umbrella has recesses 11 disposed in an array on the surface to induce a surface plasmon for coupling a specific wavelength to the surface, and the absorption amount of incident light of the specific wavelength is set to be larger than the absorption amount of incident light of wavelengths other than the specific wavelength. In the semiconductor optical device, a plurality of semiconductor optical elements are disposed in an array. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a semiconductor optical device and a semiconductor optical device, and more particularly, to a semiconductor optical device in which thermal infrared sensor elements and thermal infrared sensor elements are arranged in an array.

  In the conventional thermal infrared sensor device, when selecting the wavelength of infrared rays to be detected, an optical filter is mounted in front of the thermal infrared sensor element. As this optical filter, in addition to a multilayer optical filter, for example, as shown in Patent Document 1, an optical filter that selectively transmits light of a desired wavelength using plasmon resonance, or an electric field in the vicinity of a structure pole An optical filter using enhancement is used.

JP 2007-248382 A

  However, in the structure in which the wavelength selection filter and the thermal infrared sensor are combined, first, a filter is required in addition to the sensor, and the structure becomes complicated. Second, the wavelength required regardless of which filter is used. The components are also partially cut and the detection efficiency is lowered. Third, the optical filter is highly dependent on the incident angle, and the detection characteristics are also largely dependent on the incident angle. Fourth, a plurality of wavelengths in the infrared region are used. In order to detect simultaneously, there existed problems, such as having to mount | wear with the filter from which a structure differs for every sensor element.

  Therefore, an object of the present invention is to provide a semiconductor optical device and a semiconductor optical device that can selectively detect light having a predetermined wavelength without using a filter structure.

  One aspect of the present invention is a semiconductor optical element that includes a temperature detection unit and an absorption umbrella thermally connected to the temperature detection unit, and detects light incident on the absorption umbrella. In order to excite surface plasmons by coupling incident light of a wavelength to the surface, the surface has concave portions arranged in an array, and the amount of incident light having a specific wavelength is larger than the amount of incident light having a wavelength other than the specific wavelength. This is a semiconductor optical device characterized by the above.

  Another embodiment of the present invention is a semiconductor optical device that includes a temperature detection unit and an absorption film stacked on the temperature detection unit, and detects light incident on the absorption film, wherein the absorption film has a specific wavelength. It has concave portions arranged in an array on the surface so as to induce surface plasmons that bind to the surface, and the amount of incident light with a specific wavelength is made larger than the amount of incident light with a wavelength other than the specific wavelength. This is a semiconductor optical device.

  Another embodiment of the present invention is a semiconductor optical device in which a plurality of semiconductor optical elements are arranged in an array.

  As described above, in the semiconductor optical device according to the present invention, incident light with a specific wavelength can be selectively enhanced without using a filter, so that detection sensitivity can be improved and dependency on the incident angle is small. it can.

  In the semiconductor optical device according to the present invention, incident light having different wavelengths can be detected simultaneously.

It is a top view of the thermal type infrared sensor element concerning Embodiment 1 of this invention. It is sectional drawing of the thermal type infrared sensor element concerning Embodiment 1 of this invention. It is a top view of the fine pattern provided in the absorber umbrella of the thermal type infrared sensor element concerning Embodiment 1 of this invention. The absorption characteristic of the absorber umbrella concerning Embodiment 1 of this invention is shown. The top view of the fine pattern provided in the absorber umbrella of the thermal type infrared sensor element concerning Embodiment 2 of this invention is shown. The absorption characteristic of the absorber umbrella concerning Embodiment 2 of this invention is shown. It is sectional drawing of the fine pattern provided in the absorber umbrella of the thermal type infrared sensor element concerning Embodiment 3 of this invention. It is a top view of the thermal type infrared sensor element array concerning Embodiment 4 of this invention. It is a top view of the thermal type infrared sensor element array concerning Embodiment 5 of this invention. It is a top view of the thermal type infrared sensor element array concerning Embodiment 5 of this invention. It is sectional drawing of the thermal type infrared sensor element concerning Embodiment 6 of this invention.

Embodiment 1 FIG.
FIG. 1 is a top view of a thermal infrared sensor element according to a first embodiment of the present invention, the whole being represented by 100, and FIG. 2 is a thermal infrared sensor element in AA of FIG. FIG.

  As shown in FIGS. 1 and 2, the thermal infrared sensor element 100 includes a substrate 1 made of, for example, silicon. A hollow portion 2 is provided in the substrate 1, and a temperature detection unit 4 is supported on the hollow portion 2 by a support leg 3. The support legs 3 are two here, and have a bridge shape that is bent in an L shape when viewed from above. The support leg 3 includes a thin film metal wiring 6 and a dielectric film that supports it.

  The temperature detection unit 4 includes a detection film 5 and a thin film metal wiring 6. The detection film 5 is made of, for example, a diode using crystalline silicon. The thin-film metal wiring 6 is also provided on the support leg 3 to electrically connect the detection film 5 and the aluminum wiring 7. The thin film metal wiring 6 is made of, for example, a titanium alloy having a thickness of 100 nm. The electrical signal output from the detection film 5 is transmitted to the aluminum wiring 7 via the thin film metal wiring 6 formed on the support leg 3, and is taken out by a detection circuit (not shown). Electrical connection between the thin-film metal wiring 6 and the detection film 5 and between the thin-film metal wiring 6 and the aluminum wiring 7 is performed via a conductor (not shown) extending in the vertical direction as necessary. May be.

  The reflective film 8 that reflects infrared rays is disposed so as to cover the hollow portion 2. However, the reflective film 8 and the temperature detection unit 4 are arranged so as to cover at least a part of the support leg 3 in a state where they are not thermally connected.

  A support column 9 is provided on the temperature detection unit 4, and an absorbent umbrella 10 is supported thereon. As shown in FIG. 1, in the thermal infrared sensor element 100, only the absorber 10 can be seen when viewed from above. The absorber 10 is made of a metal thin film 6 such as Au or Ag, and has a film thickness of about several nm to several hundred nm. Here, the absorber 10 has a single-layer structure of the metal thin film 6. However, for example, a three-layer structure in which the upper and lower sides of the metal thin film 6 are sandwiched between dielectric thin films such as silicon oxide of about 100 to 200 nm, or a top of the dielectric thin film. Alternatively, a two-layer structure in which a metal thin film 6 is formed may be used. As will be described later, when surface plasmon is used, it is preferable to use Au or Ag as the metal thin film 6.

  The absorbent umbrella 10 is provided with recesses 11 in an array. The recesses 11 are arranged at equal intervals, and the period (pitch) thereof is approximately the same as the wavelength (specific wavelength) of the infrared ray that is to be detected. Further, the depth of the recess 11 is preferably, for example, about one quarter of the specific wavelength that is a wavelength to be detected.

  For example, when the specific wavelength to be detected is 1000 nm, the shape of the recess 11 is preferably a square (plane) with a side of 500 nm, the depth is 250 nm, and the interval between the recesses is 500 nm. In this case, the period (pitch) of the recess 11 is 1000 nm, which is the same as the specific wavelength.

  The film thickness of the absorber 10 is appropriately determined in consideration of absorption, thermal time constant, material stress, and the like. As can be seen from FIG. 2, the absorbent umbrella 10 is connected to the temperature detection unit 4 by the support pillar 9, that is, the absorption umbrella 10 and the temperature detection unit 4 are thermally connected. On the other hand, the absorbing umbrella 10 is held above the reflecting film 8 in a state where it is not thermally connected to the reflecting film 8, and spreads laterally so as to cover at least a part of the reflecting film 8. .

  In such a thermal infrared sensor element 100, incident infrared rays are mainly absorbed by the absorber 10. On the other hand, the infrared light that has passed through the absorbing umbrella 10 is reflected by the reflecting film 8 and is incident on the absorbing umbrella 10 from the back surface and absorbed. Infrared rays absorbed by the absorber 10 are converted into heat and transmitted to the temperature detection unit 4 through the support column 9. In the temperature detection unit 4, since the electric resistance of the detection film 5 varies depending on the temperature, the amount of infrared rays is detected by detecting this with a detection circuit (not shown) provided outside. Although the structure provided with the reflective film 8 is shown here, the reflective film 8 may not be provided.

Next, the surface plasmon of the absorbent umbrella 10 will be described. A system in which collective vibrations of free charges are combined with electromagnetic waves is called plasmon polariton (however, in this embodiment, it is called surface plasmon unless otherwise distinguished). On the surface (or boundary surface), the situation is different from plasmons in solids, and there is another collective vibration that satisfies the boundary condition on the surface.
In order to excite surface plasmons with electromagnetic waves, the phase velocity of the electromagnetic waves must match the phase velocity of the surface plasmons. At this time, an evanescent wave generated when the electromagnetic wave is totally reflected at the boundary surface is used.

  For example, consider a boundary surface sandwiched between medium 1 (phase velocity: β1, dielectric constant: ε1) and medium 2 (phase velocity: β2, dielectric constant: ε2) (when medium 1 is a substance and medium 2 is vacuum) This interface corresponds to the material surface). The condition under which the surface plasmon mode can exist at this boundary surface is expressed by the following equation (1).

  That is, ε1 and ε2 have opposite signs, that is, one has a positive dielectric constant and the other has a negative dielectric constant.

In general, a substance having a free charge such as a metal has a negative dielectric constant in a frequency region below a plasma frequency. Therefore, a surface wave satisfying the above equation 1 can exist at the interface between the metal and the dielectric (including air and vacuum). Furthermore, perpendicular to the propagation direction of the surface plasmon, when the wave number of the boundary surface and k _sp, dispersion relation of surface plasmon is as Equation 2 below.

  Where ω is the frequency and c is the speed of light in vacuum.

  That is, Equation 2 is a resonance condition for exciting surface plasmons between the dielectric and the metal.

  In general, surface plasmons have a dispersion relationship of Formula 2. When this condition is satisfied, surface plasmons that are strongly localized on the surface are excited, and the formation of such surface waves has a strong wavelength dependence. Further, since Equation 2 is below the normal light line, it is necessary to excite the surface plasmon using an evanescent wave, and it has strong incident angle dependency.

However, when a periodic structure (for example, the recess 11 shown in FIG. 1) is provided on the surface, surface plasmons can be excited by normal incident light. In other words, the wave number vector of surface plasmon
Wave vector of incident light
Reciprocal lattice vector
Then,

It becomes. For example, in the case of a one-dimensional periodic structure, assuming that the wave number of surface plasmon is k _sp , the wave number of incident light is k ₀ , the incident angle is θ, the period of the structure is d, and m is an integer, A relationship is established.

  As can be seen from Equations 3 and 4, the periodic structure overcomes the wave number mismatch and excites surface plasmons in normal incident light and couples to the surface. Since light coupled to the surface will eventually be absorbed, absorption will increase at the resonant wavelength.

  Here, even in the mid-infrared wavelength range, far-infrared wavelength range, and terahertz wavelength range, which are longer than the near-infrared range, a surface called pseudo-surface plasmon is formed by forming periodic irregularities on the surface. It is possible to form a mode that is strongly localized in the region. This is different from the original surface plasmon which is collective vibration of free electrons, but the dispersion relation, that is, the effect of coupling incident light to the surface is similar. Similarly, effects called “metamaterials” mean the same thing.

  In this wavelength range, the metal is almost a perfect conductor. However, for example, when a, b, and c are sufficiently small with respect to the wavelength in the shape as shown in FIG. 3, effective medium approximation can be applied. That is, incident electromagnetic waves exist inside periodic irregularities that are small enough to be ignored with respect to the wavelength, and can be regarded as equivalent to penetration of electromagnetic waves into a perfect conductor (metal). For this reason, the same relationship as the surface plasmon represented by Formula 2 can be equivalently formed as the dispersion relationship. In this way, the dispersion relation can be determined by the structural parameters a, b, and c.

In this way, surface plasmon, surface plasmon polariton, surface plasmon resonance, pseudo surface plasmon, and metamaterial are different in terms, respectively, but the incident light is strongly coupled to the interface between the conductor (metal) and the dielectric by periodic unevenness and absorbed. This is the same from the viewpoint of controlling the wavelength.
In the following description and claims, these terms are not particularly distinguished and are simply referred to as “surface plasmon” or “surface coupled wave”.

  Further, although the following analysis examples are intended for absorption in the vicinity of the near infrared region, as described above, the present invention can be effectively applied to wavelengths that are larger than the visible region or the near infrared region.

  Next, the structure which provided the cyclic | annular recessed part 11 in the plate-shaped absorber 10 is demonstrated. Incident electromagnetic waves are combined with the structure of the absorber 10 at a wavelength corresponding to the size, period, and depth of the concave portion 11, and a surface plasmon mode that is strongly localized on the surface is excited.

  FIG. 3 is a plan view of a fine pattern (concave portion 11) provided in the absorber 10 of the thermal infrared sensor element 100 according to the first embodiment. In FIG. 3, the array of the recesses 11 is shown in 3 rows and 3 columns (3 × 3), but it can be formed in an arbitrary array. a and b are vertical and horizontal lengths of the recesses, and c is the interval between the recesses (the interval is c in both the vertical and horizontal directions). In FIG. 3, the horizontal period is (a + c), and the vertical period is (b + c).

  FIG. 4 shows the absorption characteristics of the absorber obtained by calculating the absorption with respect to the normal incident wave by a strict coupled wave analysis method under the conditions that a = b = c, the material of the absorber 10 is Au, and the depth of the recess is 100 nm. In FIG. 4, the horizontal axis indicates the wavelength, and the vertical axis indicates the amount of absorption. The solid line is for a = b = c = 0.5 μm, the long dashed line is for a = b = c = 1.0 μm, and the short dashed line is for a = b = c = 1.5 μm.

  FIG. 4 shows that the peak wavelength of absorption can be controlled by the size and shape of the recess 11. For example, in the solid line (0.5 μm), the pattern period is 1.0 μm (a + c), and the peak wavelength of absorption is about 1 μm. On the longer dotted line (1.0 μm), the pattern period is 2.0 μm (a + c), and the absorption peak wavelengths are about 1.5 μm and about 2 μm. On the shorter dotted line (1.5 μm), the pattern period is 3.0 μm (a + c), and the absorption peak wavelengths are about 2 μm and about 3 μm.

  Further, the absorption tends to increase by deepening the recess 11. Here, for the sake of simplicity, a simple two-dimensional periodic pattern using an Au single-layer thin film has been described. However, the pattern shape can also be applied to other materials such as Ag or a multilayer structure sandwiched between dielectric layers. The same effect can be obtained by controlling. Moreover, the absorption wavelength peak can also be adjusted by adjusting the shape and period of the recess 11.

  In the structure of FIG. 2, the periodic recesses 11 are provided only on the upper surface of the absorber 10, that is, only on the incident surface of the electromagnetic wave. However, in order to absorb the light reflected by the reflective film 8, the absorber 10. It may also be provided on the back surface of. In this case, the surface plasmon is similarly generated on the back surface of the absorbent umbrella 10.

  As described above, in the thermal infrared sensor element 100 according to the first exemplary embodiment, by using the absorber 10 having the concave portions 11 arranged periodically, the infrared of a specific wavelength is resonated, and only the wavelength is obtained. It is possible to selectively absorb, eliminating the need for a conventional bandpass filter, and enabling efficient detection. In addition, since the band-pass filter is unnecessary, the optical system as the sensor module can be reduced in size and simplified. Furthermore, the incident angle dependency of the detection characteristics is almost eliminated.

Embodiment 2. FIG.
FIG. 5 shows a fine pattern (concave portion) provided on the absorption umbrella of the thermal infrared sensor element according to the second embodiment of the present invention. The recess 10 has a circular plane, and the rest is the same as the structure of FIG. Here, although a = b is a perfect circle, an ellipse having different a and b may be used. In the case of an ellipse, the surface plasmon is emphasized only with respect to specific polarization, so that it can be used when detection is performed only for specific polarization.

  FIG. 6 shows the absorption characteristics of the absorber having the structure shown in FIG. 5, where a = b = c, the absorber material is Au, and the depth of the recess 11 is 100 nm.

  From FIG. 6, it is understood that the absorption amount and the absorption peak wavelength can be changed by making the concave portion 11 circular. For example, the solid line (0.5 μm) has a pattern period of 1.0 μm (a + c) and an absorption peak wavelength of about 1 μm. On the other hand, in the longer dotted line (1.0 μm), the pattern period is 2.0 μm (a + c), and the absorption peak wavelength is shifted slightly longer than about 2 μm. Thus, by making the recessed part 11 circular, the amount of absorption, the number of absorption peaks, and the absorption wavelength can be changed, and infrared rays with an arbitrary wavelength can be detected.

Embodiment 3 FIG.
FIG. 7: is sectional drawing of the fine pattern provided in the absorber of the thermal type infrared sensor element concerning Embodiment 3 of this invention. In the first and second embodiments, the recess 11 has a rectangular cross section (see, for example, FIG. 2), but in the third embodiment, the recess 11 has a rounded shape without corners. That is, in the cross section, the continuous surface (inner wall) connecting the vertices of the bottom surface and the top surface of the recess 11 is a curved surface. Preferably, the curved surface is a sine curve. When the absorbent umbrella 10 is viewed from above, the recess 11 is rectangular or circular as shown in FIGS.

  In the absorbent umbrella 10 according to the present embodiment, the side surface of the recess 11 is a curved surface, so that surface plasmons are generated with respect to electromagnetic waves having a wider incident angle. In addition, the absorption umbrella 10 is less dependent on polarization, and can absorb a wider range of incident light. For this reason, highly efficient heat conversion becomes possible, and infrared detection efficiency becomes high.

Embodiment 4 FIG.
FIG. 8 is a plan view of the thermal infrared sensor element array according to the fourth embodiment of the present invention, in which the thermal infrared sensor elements 100 shown in FIG. 1 are arranged in an array. Here, for the sake of simplicity, a thermal infrared sensor element array including a total of four thermal infrared sensor elements in 2 rows and 2 columns is shown. There is no limit to the number. These thermal infrared sensor element arrays select a thermal infrared sensor element in each row and each column by an external scanning circuit (not shown), etc., and take out information detected by each element in time series It is good. Moreover, the system read in parallel may be used.

  In this way, by arranging the thermal infrared sensor elements in an array and selectively detecting a specific wavelength within a certain plane, it can be used as a thermal imager for detecting an image.

Embodiment 5 FIG.
FIG. 9 is a plan view of a thermal infrared sensor element array according to the fifth embodiment of the present invention. In the thermal infrared sensor element array of FIG. 9, the patterns formed on the absorber 10 of the thermal infrared sensor element are different from each other, and a = b = c = 0.5 μm (absorber umbrella A13) shown in FIG. It has a structure in which three thermal infrared sensor elements each having a pattern of 1.0 μm (absorbing umbrella B14) and 1.5 μm (absorbing umbrella C15) are combined. These thermal infrared sensor elements have strong absorption peaks at different wavelengths.

  FIG. 10 is a plan view of a thermal infrared sensor element array in which these three different thermal infrared sensor elements are taken as one unit and many units of thermal infrared sensor elements are arrayed. Here, for simplicity of explanation, a thermal infrared sensor element array including 12 (4 units) thermal infrared sensor elements is shown. There is no limit. Further, the arrangement of one unit of the thermal infrared sensor element may not be a triangular arrangement as shown in FIG.

  These thermal infrared sensor element arrays select a thermal infrared sensor element in each row and each column by an external scanning circuit (not shown), etc., and take out information detected by each element in time series Or a method of reading in parallel.

  In this way, by arranging the thermal infrared sensor elements in an array and selectively detecting a plurality of wavelengths within a certain plane, it can be used as a thermal imager for detecting an image. Further, by selectively absorbing a plurality of wavelengths, a more detailed image can be obtained than in the case of the fourth embodiment.

Embodiment 6 FIG.
FIG. 11 is a cross-sectional view of the temperature detection unit 4 of the thermal infrared sensor element according to the sixth embodiment of the present invention. The temperature detection unit 4 includes a detection film 5 and a thin film metal wiring 6. The detection film 5 is a diode, for example, and is made of silicon. The thin metal wiring 6 is made of, for example, a titanium alloy film having a thickness of 100 nm. The electrical signal output from the detection film 5 is taken out by a detection circuit (not shown) through the thin film metal wiring 6. Electrical connection between the thin-film metal wiring 6 and the detection film 5 may be performed via a conductor (not shown) extending in the vertical direction as necessary.

  The temperature detection unit 4 includes an absorption film 16 that absorbs infrared rays directly on the upper portion thereof. The absorption film 16 is made of a metal such as Au or Ag, and the material is selected according to the surface wave to be detected. Furthermore, periodic recesses as shown in the first to third embodiments are formed in the absorption film 16, and the absorption at a specific wavelength is increased by the surface plasmon determined by the structure.

  The structure other than the temperature detection unit 4 is the same as that of the thermal infrared sensor element 100 of FIG. 2, and the temperature detection unit 4 is supported on the upper portion of the hollow portion 2 by the support legs 3.

  In such a thermal infrared sensor element having the temperature detecting unit 4 integrally formed with the absorber, the desired infrared wavelength resonates and the amount of absorption is selectively increased, so that only a specific wavelength is selectively selected. Can be detected. Further, the process of supporting the absorbent umbrella with the support pillar is not required, the manufacturing process is simplified, and the product can be manufactured at a lower cost.

  The thermal infrared sensor element of the sixth embodiment may be used as the thermal infrared sensor element used in the thermal infrared sensor element array of the fourth and fifth embodiments.

  DESCRIPTION OF SYMBOLS 1 Board | substrate, 2 Hollow part, 3 Support leg, 4 Temperature detection part, 5 Detection film | membrane, 6 Thin film metal wiring, 7 Aluminum wiring, 8 Reflective film, 9 Support pillar, 10 Absorbing umbrella, 11 Recessed part, 12 Insulating film, 13 Absorption Umbrella A, 14 Absorbing umbrella B, 15 Absorbing umbrella C, 16 Absorbing film, 100 Thermal infrared sensor element.

Claims (9)

A semiconductor optical element that includes a temperature detection unit and an absorption umbrella thermally connected to the temperature detection unit, and detects light incident on the absorption umbrella;
The absorber has concave portions arranged in an array on the surface so as to induce surface plasmons that couple the specific wavelength to the surface, and the amount of incident light of the specific wavelength is determined by the incident light other than the specific wavelength. A semiconductor optical device characterized by being larger than the amount of absorption. A semiconductor optical element that includes a temperature detection unit and an absorption film stacked on the temperature detection unit, and detects light incident on the absorption film,
The absorption film has concave portions arranged in an array on the surface so as to induce surface plasmons that couple the specific wavelength to the surface, and the amount of incident light of the specific wavelength is determined by the incident light other than the specific wavelength. A semiconductor optical device characterized by being larger than the amount of absorption.   3. The semiconductor optical device according to claim 1, wherein the absorption umbrella or the absorption film has a single-layer structure of a metal film or a multilayer structure of a metal film and a dielectric film.   3. The semiconductor optical device according to claim 1, wherein the concave portion of the absorption umbrella or the absorption film has a circular plane, an elliptical shape, a square shape, or a rectangular shape, and a rectangular cross section.   3. The semiconductor optical device according to claim 1, wherein an inner wall of the concave portion of the absorbing umbrella or the absorbing film is formed from a curved surface.   3. The semiconductor optical device according to claim 1, wherein the concave portions of the absorbing umbrella or the absorbing film are arranged at a constant period, and the period is substantially the same as the specific wavelength.   7. A semiconductor optical device comprising a plurality of semiconductor optical elements according to claim 1 arranged in an array.   A first semiconductor optical element that induces a surface wave of a first specific wavelength, and a second semiconductor optical element that induces a surface wave of a second specific wavelength different from the first specific wavelength, 8. The semiconductor optical device according to claim 7, wherein the semiconductor optical device is arranged in an array.   9. The semiconductor optical device according to claim 7, wherein a period of the concave portion of the first semiconductor optical element is different from a period of the concave portion of the second semiconductor optical element.