JP2011128162A - Light receiving element and optical interconnection lsi - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve high-speed responsiveness without reducing a transmitted light volume of surface plasmon in an aperture for transmitting the surface plasmon. <P>SOLUTION: A light receiving element includes a conductive thin film 21 on one face of which a coupling periodic structure 22 to convert incident light into the surface plasmon is disposed, the aperture 23 penetrating the opposite faces being disposed in the coupling periodic structure 22, and a light receiving unit disposed at the end of the other face opposite to the one face of the aperture 23 on which the coupling periodic structure 22 is disposed. The shape of the aperture 23 is a crisscross formed by two orthogonally-crossed slits, wherein a long side length of each slit is longer than 1/2 of a surface plasmon wavelength, and its short side length is shorter than 1/2 of the surface plasmon wavelength. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a light receiving element having a plasmon condensing antenna and an optical wiring LSI using the same.

  In recent years, the performance of electronic devices such as bipolar transistors and field effect transistors has been improved, and the operating speed of large scale integrated circuits (LSIs) has been dramatically improved. However, while performance is improved by miniaturization of transistors, an increase in wiring resistance and inter-wiring capacitance becomes a serious problem due to miniaturization of electrical wiring connecting the transistors, which is becoming a bottleneck for improving LSI performance.

  In view of such a problem of electrical wiring, several optical wiring LSIs for connecting the inside of the LSI with light have been proposed. Optical wiring has a frequency dependence of loss from DC to 100 GHz or higher, and there is no electromagnetic interference in the wiring path, so wiring of several tens of Gbps or more can be easily realized.

This type of intra-LSI optical wiring requires a high-speed light receiving element made of silicon (Si), which is the substrate material for the LSI. In general, since Si is an indirect transition semiconductor, light absorption efficiency is low, and it is difficult to achieve both light reception efficiency and high speed. In order to solve this problem, a converging antenna type light receiving element using surface plasmons transmitted on the surface of a conductive material such as metal is known (for example, see Non-Patent Document 1). Furthermore, light collection by this surface plasmon and light transmission through a minute aperture are also known (see, for example, Non-Patent Document 2). On the other hand, a method using an asymmetric aperture is known in order to improve the light transmission efficiency of a minute aperture in a laser device, although it is different from a plasmon condensing antenna type light receiving device (see, for example, Patent Document 1).

JP 2001-189519 A

Japanese Journal of Applied Physics Vol.44, No.12, p.L364 (2005) Optics Letters Vol.26, No.24, p.1972 (2001)

  In the technique as described in Non-Patent Document 1, it is necessary to photoelectrically convert the light collected by the plasmon condensing antenna immediately after passing through the minute aperture, that is, by arranging the Si light receiving layer at the exit of the minute aperture. In addition, if the length of the minute aperture (corresponding to the thickness of the conductive thin film) is long, the light passing through the aperture is greatly attenuated. Therefore, the conductive thin film that forms the plasmon condensing antenna is such that light does not pass therethrough. It is necessary to form thinly.

  For this reason, when applying light to LSI wiring, a method of forming a condensing antenna type light receiving element on a transistor formation surface (Si substrate surface), a condensing antenna type light receiving element formed on another substrate, and bonding, It is necessary to use one of a method in which a plasmon antenna and a poly-Si light-receiving layer are arranged on a multilayer wiring and photoelectric conversion is performed on the multilayer wiring and a signal is transmitted to the transistor formation surface by electric wiring.

  However, the method of forming the converging antenna type light receiving element on the transistor formation surface is not practical because the number of LSI transistors integrated is drastically reduced and the essential functions of the LSI are impaired. In addition, a method of forming a condensing antenna type light receiving element on an LSI multilayer wiring and electrically wiring from there to the Si substrate surface is due to signal degradation and noise increase due to parasitic LCR of the electrical wiring portion, and crossing to other electrical wiring. There is a problem that problems such as the occurrence of talk are likely to occur, and high-speed performance due to optical wiring is easily impaired.

  In the method of Non-Patent Document 2, it is desirable to reduce the opening for high-speed response. However, if the opening is reduced, there is a problem in that the amount of transmitted light of surface plasmons is reduced.

  The present invention has been made in view of the above circumstances, and the object of the present invention is to improve the high-speed response without causing a decrease in the amount of transmitted light of the surface plasmon in the opening for transmitting the surface plasmon. The object is to provide a light receiving element.

  Another object of the present invention is that high-speed optical wiring can be realized on an LSI chip, the configuration is simple and there are no problems such as signal degradation and crosstalk, and the LSI integration degree and high-speed optical wiring It is to provide an optical wiring LSI that does not impair the performance.

  In order to solve the above problems, the present invention adopts the following configuration.

  That is, according to one aspect of the present invention, there is provided a conductive thin film in which a coupling periodic structure for converting incident light into surface plasmons is provided on the surface, and an opening penetrating the front and back surfaces is provided in the coupling periodic structure; A light receiving element having a light receiving portion disposed at an end of the opposite surface and a surface provided with the coupling periodic structure of the opening, wherein the shape of the opening is a cross shape in which two slits are orthogonally crossed. And the long side direction of each slit is longer than ½ of the surface plasmon wavelength, and the short side direction is shorter than ½ of the surface plasmon wavelength.

  According to another aspect of the present invention, in an optical wiring LSI, transistor elements integrated on a semiconductor substrate, a multilayer wiring structure provided on the transistor elements, and a multilayer wiring structure provided on the multilayer wiring structure A conductive thin film in which a coupling periodic structure for converting incident light into surface plasmons is formed on the upper surface, and an opening penetrating the upper and lower surfaces is formed in the coupling periodic structure; A conductive column provided through the lower surface and having a waveguide opening continuous with the opening of the conductive thin film; and the semiconductor substrate positioned at an end of the waveguide opening of the conductive column A semiconductor light-receiving portion provided on the surface of the aperture, and the opening has two long side directions longer than ½ of the surface plasmon wavelength and short side directions shorter than ½ of the surface plasmon wavelength. Crossing the slits orthogonally A cross shape was, wherein said coupling periodic structure is a concentric structure around the opening.

The top view which shows schematic structure of the plasmon condensing antenna in the light receiving element concerning 1st Embodiment. FIG. 2 is a perspective view showing the schematic configuration of the light receiving element according to the first embodiment with a part cut away. The perspective view which expands and shows the principal part of the light receiving element concerning 1st Embodiment. FIG. 3 is a cross-sectional view illustrating a schematic configuration of a light receiving element according to the first embodiment. The plane which shows schematic structure of the plasmon condensing antenna in the light receiving element concerning 2nd Embodiment. FIG. 6 is a perspective view showing a schematic configuration of a light receiving element according to a second embodiment with a part cut away. The perspective view which expands and shows the principal part of the light receiving element concerning 2nd Embodiment. FIG. 9 is a perspective view showing a schematic configuration of an optical wiring LSI according to a third embodiment with a part cut away. The perspective view which expands and shows the principal part of the optical wiring LSI concerning 3rd Embodiment.

  The essence of the present invention is that a plasmon condensing antenna for receiving light is provided on or in an LSI multilayer wiring, and the surface plasmon collected there is transmitted to the Si substrate surface by a micro-aperture waveguide. Then, light is received (photoelectric conversion). In general, the amount of light transmitted through an aperture having a wavelength equal to or smaller than the wavelength of the light dramatically decreases as the aperture size is reduced. Therefore, in the present invention, a certain polarization direction of the incident light is selectively condensed. Thus, polarization selective transmission by an asymmetric aperture is performed, or polarization separation transmission is performed by a synthetic aperture of an asymmetric aperture orthogonally focused by non-selectively condensing the polarization direction.

  The details of the present invention will be described below with reference to the illustrated embodiments.

  Here, description will be made using Si as a specific light receiving material. For example, a material capable of receiving light such as Ge, SiGe, SiC, GaAs, InP, GaInAs, GaInAsP, and AlGaAs is used as the light receiving portion ( If it exists in a photoelectric conversion part), it can implement similarly, and this invention is not limited to the following embodiment. In addition, here, one light receiving element (optical wiring receiving unit) is shown in an extracted form, but of course, this is intended to integrate a large number of light receiving elements and to be integrated on an LSI chip. The number of light receiving elements and optical wirings to be integrated is arbitrary.

(First embodiment)
FIG. 1 is a plan view showing a schematic configuration of a plasmon condensing antenna portion in the light receiving element according to the first embodiment of the present invention.

  In the figure, 11 is a conductive thin film, 12 is a concentric periodic structure (partial digging pattern), and 13 is an opening. The opening 13 is provided so as to penetrate from the front surface to the back surface of the conductive thin film 11. The concentric circular structure 12 is a partial excavation pattern obtained by etching a part of the surface of the conductive thin film. The inner region (A) of the concentric periodic structure 12 is a coupling periodic structure that couples light incident in the direction perpendicular to the paper surface to surface plasmons, and the outer region (B) is coupled by the coupling periodic structure (A). This is a reflection periodic structure in which a component that diverges from the surface plasmon toward the outside of the element is Bragg-reflected and returned to the inside.

  The conductive thin film 11 may be formed by using a metal such as Ag, Au, Cu, Al, Ni, Pd, Pt, W, Ti, Cr, or Mo and using a technique such as sputtering or heat evaporation. Here, Ag is used as the conductive thin film 11 and is formed to a thickness of, for example, 100 nm on the surface of a Si substrate for forming a light receiving element described later.

The concentric periodic structure 12 needs to form a period according to the wavelength of light to be received. When the received light wavelength is λ, the dielectric constant of the conductive thin film 11 is ε1, and the dielectric constant of the substance in contact with the conductive thin film is ε2, the period Pc of the coupling periodic structure (A) is
Pc to λ (1 / ε1 + 1 / ε2) ^1/2
It is approximated by the value. The period Pb of the reflection periodic structure (B) is
Pb = Pc / 2
What should I do?

As an example, a concentric periodic structure as shown in FIG. 1 is formed on the surface of the conductive thin film 11 (Ag thickness 100 nm) at a depth of 50 nm using a focused ion beam (FIB) apparatus. When Pc is 840 nm (Pb = 420 nm) when the surface is air, and Pc is 560 nm (Pb = 280 nm) when a SiO ₂ passivation film having a thickness of about 1 μm is formed on the surface of the conductive thin film 11, both receive light. The possible center wavelength λ is in the vicinity of 850 nm. At this time, as shown in FIG. 1, the concentric periodic structure 12 has a symmetric fan shape centered on the opening 13, and the opening angle of the fan shape is, for example, 45 °. This shape corresponds to the shape when the concentric periodic structure 12 is divided into four in a central symmetry, and every other one is cut out to leave two.

  By doing so, the light polarized in the fan-shaped central axis direction (left and right direction in the drawing) is converted into surface plasmon and condensed, and the polarization component orthogonal to the surface plasmon is not condensed. This means that the light component received through the central opening 13 becomes light polarized in the direction of the central axis of the sector, and polarization selective light reception becomes possible. In order to more reliably separate the polarization components, light received at a fan angle of around 45 ° may be cut off. For example, if the fan-shaped opening angle in FIG.

  The opening 13 in FIG. 1 has a minimum size so that a light receiving layer for photoelectrically converting light is limited to a sufficiently small region. As a reference, the direction orthogonal to the central axis of the sector in FIG. 1 is set slightly larger than ½ of the plasmon wavelength, and the direction parallel to the central axis of the sector is set smaller than ½ of the plasmon wavelength. That is, the opening 13 is a slit-like opening related to the polarization direction of incident light. Strictly speaking, the plasmon wavelength λp is a plasmon wavelength inside the aperture, but since it has almost the same size as the above-mentioned Pc (corresponding to the plasmon wavelength on the surface of the plasmon focusing antenna), the aperture 13 has a long side ( The short side (polarization direction) may be much smaller than Pc / 2 as long as Pc / 2 or more is orthogonal to the polarization direction.

For example, when a SiO ₂ passivation film having a thickness of about 1 μm is formed on the surface of the conductive thin film 11 in the case of λ to 850 nm, the long side (perpendicular to the polarization direction) of the opening 13 is 280 nm or more (for example, 400 nm). The short side (polarization direction) is 280 nm or less (for example, 100 nm). Of course, the opening 13 is a hole penetrating the conductive thin film 11, and in the above example (Ag thickness 100 nm), the FIB is used to perform a digging process with a depth of 100 nm or more as a groove having a length of 400 nm and a width of 100 nm. .

With this configuration, the propagation loss of the opening 13 can be reduced by the principle shown in (Patent Document 1), and the plasmon attenuation in the opening 13 can be greatly reduced even if only the opening 13 is formed thick. Can be reduced. As an example, when the thickness of the opening 13 (opening length) is 1 μm and the transmittance of polarized light orthogonal to the long side of the slit-shaped opening of 400 nm × 100 nm is estimated, the transmittance is about 41%. On the other hand, the transmittance of polarized light parallel to the long side of the slit-shaped opening was substantially zero (˜1 × 10 ⁻¹⁸ ). Even if the thickness (opening length) of the opening 13 is 10 μm, the transmittance of polarized light in the direction perpendicular to the long side of the 400 nm × 100 nm slit-like opening can be secured to about 6%.

For reference, when the transmittance is estimated with a circular opening (diameter 226 nm) having the same area as the slit-shaped opening described above, it is 2 × 10 ⁻⁹ , which is close to zero, and the thickness of the opening is made extremely thin in the prior art. Or it turns out that it is necessary to enlarge an opening diameter. For example, when the thickness of the circular opening is 100 nm, the transmittance is about 16%. Further, if the opening thickness is 1 μm and the opening diameter is 500 nm, a transmittance of about 80% is possible, but the opening area becomes about five times that of the slit-shaped opening of the present embodiment.

  In addition, in order to prepare a large circular opening as large as 500 nm, a larger conductive cylinder (for example, a diameter of 800 nm) is required, which greatly affects the layout limitation of multilayer wiring and the transistor arrangement in mounting on an LSI described later. Furthermore, there is a problem that the number of integrated transistors in the LSI is lowered due to a decrease in the number of integrated transistors in the light receiving element section. Furthermore, as the aperture system increases, the area of the light receiving element increases. For example, when a photodiode is formed with a pn junction, high-speed response is difficult because of the large junction capacitance.

  Here, the long side of the opening 13 of this embodiment (FIG. 1) needs to be orthogonal to the polarization direction of the incident light. In order to satisfy this condition, the fan-shaped plasmon condensing antenna is used as described above. Used. When a completely concentric plasmon condensing antenna as in the conventional example is applied to the slit-shaped aperture 13 described above, a polarization component parallel to the long side of the slit-shaped aperture cannot enter the aperture 13, and the plasmon collection It is confined by multiple reflection by the reflection periodic structure (B) until it attenuates by scattering or absorption on the optical antenna. At this time, a part of the scattered surface plasmon becomes a component that can be incident on the slit-shaped opening 13, and there is a problem that it becomes delayed incident light and causes deterioration of the received waveform and increase in noise.

Next, details of the light receiving element to which the plasmon condensing antenna shown in FIG. 1 is applied are shown in FIGS. 2 and FIG. 3 are perspective views in which a 1/4 region is cut out at a portion I-13-I ′ in the plan view of FIG. 1, 14 is an n-type Si substrate, 15 is a back electrode (for example, Al), 16 Is a low-concentration Si layer for receiving light, and 17 is a SiO ₂ thermal oxide film for defining a light receiving region. 4 is a cross-sectional view taken along a line II ″ in the plan view of FIG.

Although not shown in FIGS. 2 to 4, a SiO ₂ passivation film may be formed on the conductive thin film 11, and in that case, the function is equivalent by changing the period of the concentric circular structure 12. Become.

For example, the plasmon condensing antenna is provided with a Ti film (not shown) having a thickness of 10 nm as an adhesion metal with the Schottky electrode with the low-concentration Si layer 16 and the SiO ₂ thermal oxide film 17, and Ag as the conductive thin film 11. Provide 100 nm. The slit-shaped opening 13 is 400 nm × 100 nm, the concentric periodic structure 12 is 50 nm deep, the coupling periodic structure A (for example, 10 periods) as in FIG. 1, and the reflective periodic structure B (for example, 5 periods) outside thereof. Place.

At this time, assuming that the light receiving wavelength is 850 nm, a periodic structure diameter of about 14 μmφ is obtained in the SiO ₂ passivation type element (Pc = 560 nm). The light receiving diameter is about 11 μmφ, and light transmitted through the single mode optical fiber can be received by butt joint coupling. The light receiving layer 16 has a thickness of 2 μm, for example, and a thermally oxidized SiO ₂ film 17 defining the light receiving region is formed to 2 μm. As a result, the low-concentration Si layer 16 other than the light receiving portion (below the opening 13) changes to about 1 μm into the thermally oxidized SiO ₂ film 17 and the remaining thickness becomes about 1 μm.

  With such a configuration, a light receiving element having characteristics such as a light receiving efficiency of about 10% (photoelectric conversion coefficient 0.08 A / W) and a response speed of 15 GHz or more was obtained.

  As described above, according to this embodiment, the photoelectric conversion area of the light receiving element is much smaller than the area of the light receiving antenna (plasmon condensing antenna), and can be significantly smaller than the circle whose diameter is the light receiving wavelength. Moreover, by forming the opening 13 for transmitting the surface plasmon in the shape of a slit, the opening area can be reduced without causing a decrease in the amount of transmitted light compared to a circular opening having the same diameter, and high-speed response can be achieved. Improvements can be made. That is, a light receiving element having excellent light receiving efficiency and response speed can be realized.

(Second Embodiment)
FIG. 5 is a plan view showing a schematic configuration of a plasmon focusing antenna portion of a light receiving element according to the second embodiment of the present invention. In addition, 21-23 in FIG. 5 is corresponded to 11-13 in FIG.

  In the first embodiment described above, the polarization direction is selectively collected by selectively condensing a certain polarization direction of the incident light. However, in this embodiment, the polarization direction is not selected. The light is condensed and polarized light is split and transmitted by a synthetic aperture of orthogonal asymmetric apertures (slit apertures).

  That is, FIG. 5 shows two combinations of the polarization-selective plasmon condensing antenna and the slit-shaped aperture shown in FIG. As a result, in this embodiment, the plasmon condensing antenna has a concentric periodic structure similar to that of the prior art, but the central opening 23 has a cross-shaped opening different from that of the conventional example. Here, the long side direction of each slit of the cross-shaped opening 23 is longer than ½ of the surface plasmon wavelength, and the short side direction is shorter than ½ of the surface plasmon wavelength.

  The characteristics of the cross-shaped opening 23 are the same as those of the slit-shaped opening 13, and the distance between the apexes of the cross-shaped (the length of the top, that is, the long side direction of the slit) is ½ or more of the plasmon wavelength. Even if the groove width (line width, that is, the short side direction of the slit) is considerably narrower than ½ of the plasmon wavelength, the transmittance of the opening can be kept high.

  The principle is basically the same as that of the slit-shaped opening, and it is easy to understand if the cross shape is separated and divided into two slit openings. That is, each slit has high transmittance for polarized light in a specific direction, and low transmittance for polarized light orthogonal thereto. However, as a result of the orthogonal arrangement of the slits, no matter which direction of polarization enters, the slits are divided into high-direction components and the two slits transmit each component, resulting in polarization. The aperture is transmitted regardless of the direction.

  For example, when polarized light inclined by 45 ° with respect to the longitudinal direction of one slit obtained by dividing the cross shape is incident, if there is one slit opening, light having a half component is incident on the opening, and the remaining 1 As described above, the / 2 minutes are multiple-reflected in the plasmon condensing antenna and eventually disappear due to scattering and absorption. However, when there is another orthogonal slit opening, the remaining half of the time immediately enters the other slit opening. As a result, surface plasmons having orthogonal components appear on the opposite side of the cross-shaped opening as if they passed through separate slits, and are synthesized at the exit of the cross-opening to restore the original surface plasmon.

  As a result, the top length of the cross-shaped slit is set to 1/2 or more of the plasmon wavelength, and by sufficiently narrowing the groove width, the opening area is reduced and sufficiently larger than 1/2 of the plasmon wavelength. High transmittance characteristics similar to a circular opening can be obtained. In addition, it is possible to realize a high-speed light receiving element having a small light receiving area that does not depend on the polarization direction of incident light.

  FIGS. 6 and 7 are perspective views in which a quarter region is cut out at the II-23-II ′ portion of the plan view of FIG. 5, and reference numerals 21 to 25 in FIGS. 6 and 7 denote FIGS. It corresponds to 11-15.

The plasmon condensing antenna in this case is provided with, for example, 10 nm of Ti as the conductive thin film 21 and 10 nm of Ag as the adhesion metal between the Schottky electrode with the low concentration Si layer 26 and the SiO ₂ film 27. The top length of the cross opening 23 is 400 nm, the groove width (line width) of the cross opening 23 is 100 nm, and the concentric periodic structure 22 is 50 nm in depth with the coupling periodic structure A (for example, 10 periods) as in FIG. ), And the reflection periodic structure B (for example, 5 periods) is arranged concentrically as shown in FIG.

At this time, assuming that the light receiving wavelength is 850 nm, a periodic structure diameter of about 14 μmφ is obtained in the SiO ₂ passivation type element (Pc = 560 nm). The light receiving diameter is about 11 μmφ, and light transmitted through the single mode optical fiber can be received by butt joint coupling. The light receiving layer 26 has a thickness of 2 μm, for example, and a thermally oxidized SiO ₂ film 27 defining the light receiving region is formed to 2 μm. As a result, the low-concentration Si layer 26 other than the light receiving portion (below the opening 23) changes to about 1 μm into the thermally oxidized SiO ₂ film 27, and the remaining thickness becomes about 1 μm.

  With such a configuration, a light receiving element having characteristics such as a light receiving efficiency of about 10% (photoelectric conversion coefficient 0.08 A / W) and a response speed of 15 GHz or more and having no dependence on the polarization direction of incident light was obtained. In this case, the cross-sectional area of the opening 23 is about twice that of the first embodiment and the light receiving area is also about twice, but the parasitic capacitance of the element is sufficiently small and the light receiving element response characteristic is Si layer. 26, the response speed equivalent to that of the first embodiment is obtained.

(Third embodiment)
8 and 9 are cross-sectional perspective views showing a schematic configuration of an optical interconnection LSI according to the third embodiment of the present invention. In FIG. 8 and FIG. 9, the same numbers as those in FIG. 6 and FIG.

  In FIG. 8, 31 is a semiconductor light receiving portion, 32 is a CMOS transistor, 33 is a Cu wiring, 34 is an interlayer insulating film, 35 is a multilayer wiring structure, and 36 is a cylindrical conductor (metal column). Here, an example is shown in which the optical wiring LSI is configured using the light receiving element having a cross-shaped aperture that does not depend on polarization shown in FIGS. 6 and 7. In FIG. 9, 31 a is a p-type well, 31 b is an n-type light-receiving layer, and p-type well 31 a is an inverted conductive well that is electrically separable from n-type substrate 24.

  Further, the opening (cross-shaped) 23 transmits a surface plasmon from the plasmon condensing antenna on the multilayer wiring structure portion 35 through the multilayer wiring structure portion 35, so that a metal column (conductive) that is thicker than the condensing antenna portion. (Column) 36 is extended to the Si substrate surface. Since the opening 23 has a cross shape, the outer shape of the metal column 36 extending through the multilayer wiring structure 35 is also formed in a cross shape, thereby occupying a large layout area like a cylindrical metal column. Instead, it is possible to embed in the gap between the multilayer wiring structure 35 and the section (square area) of the transistor layout.

  The cross-shaped metal column 36 in the multilayer wiring structure portion 35 may be made of Cu, which is a multilayer wiring metal. However, since absorption loss is somewhat large, it is desirable to use Ag if possible. In that case, for example, after completion of the multilayer wiring process, a cross-shaped groove extending through the interlayer insulating film 34 of the multilayer wiring and a part of the Cu wiring 33 (such as a bias line of the light receiving element) is provided, and Ag-filling is performed by plating, thereby 36 is formed. Thereafter, a plasmon focusing antenna may be formed and a cross opening may be formed by dry etching.

  LSI multilayer wiring generally has a thickness of about 10 μm, and the plasmon transmission distance of the cross-shaped opening is about 10 μm. This is different from the transmission only through the conductive thin film 21 of the second embodiment described above, and it is desirable to prepare an opening with a size having a margin to reduce transmission loss. For example, when 10 μm is transmitted through an Ag waveguide having a top length of 450 nm and a cross groove width of 200 nm as the cross-shaped opening 23, a transmission efficiency of about 20% can be obtained with incident light having a wavelength of 850 nm. The opening area (light receiving area) at this time is an area of a circular opening having a diameter of 420 nm, and does not become an area that reduces the response speed of the light receiving element from about 15 GHz.

  Therefore, in the present embodiment, even if the surface plasmon is transmitted from the upper part of the LSI multilayer wiring to the Si substrate surface, the loss is about -7 dB, and it can be sufficiently recovered with a gain using only one or two transistors. In addition, there is an effect that a high-speed operation (for example, 10 GHz clock) by the optical wiring can be realized in a state where there is no deterioration in waveform or increase in excess jitter.

  As described above, according to this embodiment, the same effect as that of the second embodiment can be obtained, and the light receiving antenna can be formed at a position away from the transistor integration surface of the LSI. Optical wiring can be introduced with almost no decrease in the degree of integration, and the layout of the multilayer wiring can be made extremely small. As a result, the light receiving element photoelectric conversion portion can be formed in a slight gap region of the LSI transistor integration surface (Si substrate), and can be wired almost directly to the transistor, so that deterioration due to electric wiring and noise increase hardly occur. It has the features such as. Therefore, high-speed optical wiring in the LSI chip can be effectively constructed, and it is possible to greatly contribute to the advancement of information communication equipment by promoting the high speed and high performance of the LSI.

(Modification)
The present invention is not limited to the above-described embodiments. For example, the above-described embodiments of the present invention show some specific examples. However, these are merely configuration examples, and other means (materials, dimensions, etc.) may be used for individual elements in accordance with the gist of the present invention. It doesn't matter. In addition, the materials, shapes, arrangements, and the like shown in the embodiments are merely examples, and the embodiments can be implemented in combination. For example, in the first embodiment, the light receiving element has strong polarization dependence and is sensitive to the deviation of the polarization plane. By utilizing this, the light receiving elements according to the first embodiment are prepared. By arranging them orthogonal to each other, it is possible to receive the light by polarization-separation with respect to the collectively irradiated light that has been polarization multiplexed.

Further, the inside of the opening does not necessarily need to be hollow, and a dielectric such as SiO ₂ or SiN may be embedded. The light receiving portion is not limited to a photodiode, and a phototransistor can be used. Further, a photoelectric conversion material that converts light into an electrical signal may be provided.

  In addition, the present invention can be variously modified and implemented without departing from the spirit of the present invention.

11, 21 ... conductive thin film, 12, 22 ... periodic structure, 13, 23 ... minute aperture, 14, 24 ... Si substrate, 15, 25 ... electrode, 16 ... low concentration i layer (light receiving layer), 17 ... SiO ₂ Thermal oxide film 31... Semiconductor light receiving portion, 31 a... P type well, 31 b... N type light receiving layer, 32... CMOS transistor, 33. (Conductive pillar).

Claims (5)

A coupling periodic structure for converting incident light into surface plasmons is provided on the surface, a conductive thin film provided with an opening penetrating the front and back surfaces in the coupling periodic structure, and the coupling periodic structure of the opening is provided. A light receiving element having a light receiving portion disposed at an end of the opposite surface and the opposite surface,
The shape of the opening is a cruciform shape in which two slits are orthogonally crossed. The long side direction of each slit is longer than ½ of the surface plasmon wavelength, and the short side direction is ½ of the surface plasmon wavelength. A light receiving element characterized by being shorter.   The light receiving element according to claim 1, wherein the coupling periodic structure is a concentric structure centered on the opening.   The light receiving element according to claim 1, wherein a reflection periodic structure for reflecting and confining the surface plasmon is further formed outside the coupling periodic structure on the surface of the conductive thin film.   The light-receiving element according to claim 1, wherein the conductive thin film is formed on a semiconductor substrate, and the light-receiving portion is formed by forming a photodiode on a surface of the semiconductor substrate. Transistor elements integrated on a semiconductor substrate;
A multilayer wiring structure provided on the transistor element;
A conductive thin film provided on the multilayer wiring structure, the coupling periodic structure for converting incident light into surface plasmons is formed on the upper surface, and the openings penetrating the upper and lower surfaces are formed in the coupling periodic structure; ,
A conductive pillar provided penetrating the upper and lower surfaces of the multilayer wiring structure portion, and having a waveguide opening formed continuously with the opening of the conductive thin film;
A semiconductor light receiving portion provided on the surface of the semiconductor substrate so as to be positioned at an end portion of the waveguide opening of the conductive pillar;
Comprising
The opening has a cross shape in which two slits having a long side direction longer than ½ of the surface plasmon wavelength and a short side direction shorter than ½ of the surface plasmon wavelength are orthogonally crossed, and the coupling period structure An optical wiring LSI characterized by having a concentric circular structure centered on the opening.

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