JP2005176156A - Antenna integrated element and its producing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To produce an antenna integrated element using a semiconductor process technology with high reproducibility or controllability, the antenna integrated element being adopted to suppress a loss of incident light and to make a surface where light is made incident, different from a surface where an electromagnetic wave is radiated. <P>SOLUTION: A photo-detector 2, a plane antenna 4, wiring 6 are formed on a semiconductor substrate 1, a high dielectric film 7 is formed and flattened thereon, an insulator substrate 8 is adhered, and the semiconductor substrate 1 is finally removed. Thus, the antenna integrated element can be produced using the semiconductor process technology. In this formed antenna integrated element, light is made incident from a lower surface side, and electromagnetic waves are radiated from an upper surface side. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an antenna integrated element in which a light receiving element and a planar antenna are integrated on a plane of an insulating substrate, and a method for manufacturing the same.

  In recent years, a broadband millimeter wave / submillimeter wave source has been demanded as a reference signal source in wireless communication, high-speed signal measurement, or radio astronomy. Among these, since a high-frequency signal can be transmitted over a long distance, a millimeter-wave / sub-millimeter wave generation method using beat light has attracted attention. In this method, generation of millimeter waves and submillimeter waves is realized by an antenna integrated element in which a light receiving element responsible for optical / electrical conversion and an antenna that radiates the converted electric signal to space are integrated.

  As a configuration example of the antenna integrated element, a combination of a photodiode as a light receiving element and a planar antenna is suitable because it is suitable for mass production by application of a widely established semiconductor process technology.

FIG. 3 is a diagram showing an antenna integrated element of Conventional Example 1 (see, for example, H. Ito et al., Electron. Lett., Vol. 38, No. 17, pp. 989-990, 2001).
3A is a view of the central portion of the antenna integrated element as viewed from directly above, and FIGS. 3B and 3C are AA ′ and B in FIG. 3A, respectively. It is sectional drawing of the site | part shown by -B '.

  First, an epitaxial layer of the light receiving element 13 is formed on the semiconductor substrate 11 by epitaxial growth. After forming a mesa structure by etching using a photoresist as a mask, ohmic contact electrodes are formed on the p-type and n-type layers, respectively. Next, the planar antenna 12 is formed. Further, after forming the insulating film 15, the wiring 14 is formed so as to connect the planar antenna 12 and the light receiving element 13. Finally, the reflective film 16 is formed on the back surface of the substrate, thereby completing the antenna integrated element.

  In the antenna integrated element manufactured in this way, light enters from the front side of the paper in FIG. 3A (above FIGS. 3B and 3C). As shown in FIGS. 3B and 3C, a part of the incident light is reflected on the surfaces of the wiring 14 and the planar antenna 12, and the rest enters the substrate 11. The light that has entered the semiconductor substrate 11 is reflected by the reflective film 16 formed on the back surface, and received by focusing on the absorption layer of the light receiving element 13. A signal converted from light to electricity by the light receiving element 13 is transmitted to the planar antenna 12 via the wiring 14. As shown in FIG. 3C, in this configuration, since the space (air) is directly above the planar antenna 12, the electromagnetic wave has a higher dielectric constant on the semiconductor substrate 11 side (the lower side in FIG. 3C). Mainly radiated to.

  When light is incident from the front side of FIG. 3A, light is reflected at a portion covered with the wiring 14 and the planar antenna 12, and only a part of the incident light can enter the semiconductor substrate 11. For example, when a wideband log periodic antenna is employed as the planar antenna as shown in the prior art 1, the semiconductor substrate 11 is covered with the antenna about half of its surface area, so at least about 50% in this portion. There was a loss and was a problem.

  In order to solve this loss of incident light, a method in which light is incident from the back surface of the semiconductor substrate 11 that is not covered by the wiring 14 and the planar antenna 12 is also conceivable. However, as described above, the electromagnetic wave is a semiconductor substrate 11 having a high dielectric constant. It is mainly emitted to the back side of the light and is in the same direction as the incidence of light.

  At this time, there is a problem that a lens or a fiber for incident light is positioned on the electromagnetic wave radiation surface, which becomes an obstacle to the radiation of the electromagnetic wave.

  On the other hand, if a wiring is formed between the substrate and the light receiving element, the loss of incident light can be kept low, and the light incidence and electromagnetic wave radiation directions can be reversed in the conventional manner, which solves these problems.

  In Conventional Example 2, an element having such a structure is manufactured using flip-chip connection (Japanese Patent Laid-Open No. 2002-43839). FIG. 4A is a view of this element as viewed from directly above, and FIG. 4B is a cross-sectional view of a portion indicated by CC ′ in FIG.

  A light receiving element chip 21 having a light receiving element 20 formed on a chip surface 26 and a transmission path 22 on the light receiving element chip, and a planar antenna chip 23 having a planar antenna chip transmission path 25 and a planar antenna 24 are provided. The transmission path on the light receiving element chip 21 and the planar antenna chip 23 is prepared and flip-chip connected so that the pads 28 are connected to each other. In this configuration, light is incident from the light receiving element chip back surface 27, and the light / electrically converted signal is transmitted through the transmission path and is mainly emitted from the planar antenna 24 to the lower side of the planar antenna chip 23. Here, a slot antenna is illustrated as a planar antenna.

  However, in the case of the sub-millimeter wave band logperiodic antenna as used in the conventional example 1, as shown in FIG. 3 (a), it corresponds to an electromagnetic wave having a certain frequency from the center position of the whole antenna. If the distance to the center of the tooth is the antenna radius, this antenna radius corresponds to ¼ of the effective wavelength of the electromagnetic wave, so that the antenna structure becomes smaller as the frequency increases. For example, when the substrate on which the antenna is formed is Si and handles an electromagnetic wave of 1 THz, the radius of the antenna is about 30 μm. As described above, in order to efficiently radiate electromagnetic waves generated in the element structure of Conventional Example 2 toward the substrate, it is necessary to make the chip size of the light receiving element to be flip-chip connected smaller than the antenna radius. Then, the limit is about several hundred μm at most. For this reason, the upper limit of the band of the generated electromagnetic wave is determined by the chip size of the light receiving element.

  Further, when handling the super-high frequency in the submillimeter wave band, the transmission loss of the flip chip connecting portion between the light receiving element and the planar antenna increases, and it does not reach the antenna integrated element formed on the same plane. In addition, although the flip chip connection method has been established as a stable technology for consumer use, it cannot be said that it is suitable for mass production when compared with a semiconductor process. Furthermore, when flip chip connection is performed, a slight gap remains between the substrate on which the planar antenna is formed and the light receiving element, so that radiation efficiency is deteriorated and there is a problem with the rating.

JP2002-43839 H. Ito et al., Electron. Lett., Vol. 38, No. 17, pp. 989-990, 2001

  An object of the present invention is to use an antenna integrated element that can cope with a submillimeter wave band that solves the problems of the light incident efficiency and the electromagnetic wave radiation direction, using a widely established semiconductor process technology suitable for mass production. An antenna integrated element that can be manufactured with good reproducibility and controllability, and a manufacturing method thereof.

In order to solve the above problems, a method for manufacturing an antenna integrated element proposed in the present invention includes a light receiving element made of a semiconductor formed on an insulator substrate, and a planar antenna electrically connected to the light receiving element by wiring. And a method of manufacturing an antenna integrated element configured to cause an optical signal to be incident on the light receiving element from a side of the substrate on which the planar antenna is formed. Forming, a step of forming a high dielectric film on the surface of the semiconductor substrate, a step of flattening irregularities on the surface of the high dielectric film, and a step of adhering an insulator substrate on the high dielectric film; And a step of removing the semiconductor substrate.
Through such a process, an antenna integrated element with a low loss of incident light can be manufactured with good reproducibility and controllability.

  The antenna integrated element of the present invention includes at least a light receiving element made of a semiconductor formed on an insulator substrate, and a planar antenna electrically connected to the light receiving element by wiring, An antenna integrated element configured to allow an optical signal to be incident on the light receiving element from a side where the planar antenna is formed, wherein a light receiving element, a planar antenna, and a wiring are formed on a semiconductor substrate, and a high dielectric is formed on the surface of the semiconductor substrate A film is formed, the unevenness on the surface of the high dielectric film is flattened, an insulating substrate is bonded onto the high dielectric film, and the semiconductor substrate is removed.

  The antenna integrated element of the present invention electrically connects the light receiving element whose light incident surface side is exposed to the space, the planar antenna whose one surface is exposed to the space, and the light receiving element and the planar antenna on the opposite side of the space. A wiring to be connected, a high dielectric film formed so as to cover the light receiving element, the planar antenna and the wiring on the opposite side of the space, and an insulator substrate formed so as to cover the high dielectric film It is configured.

The method for manufacturing an antenna integrated element of the present invention includes at least a light receiving element made of a semiconductor formed on an insulator substrate, and a planar antenna electrically connected to the light receiving element by wiring, and the substrate. Forming a light receiving element, a planar antenna, and a wiring on a semiconductor substrate, and a surface of the semiconductor substrate, wherein the optical signal is incident on the light receiving element from the side where the planar antenna is formed. A step of applying an insulating adhesive for a semiconductor, a step of bonding an insulator substrate on the semiconductor substrate, and a step of removing the semiconductor substrate.
Through such a process, an antenna integrated element with a low loss of incident light can be manufactured with good reproducibility and controllability.

  The antenna integrated element of the present invention includes at least a light receiving element made of a semiconductor formed on an insulator substrate, and a planar antenna electrically connected to the light receiving element by wiring, An antenna integrated element configured to allow an optical signal to be incident on the light receiving element from a side on which the planar antenna is formed, wherein a light receiving element, a planar antenna, and a wiring are formed on a semiconductor substrate, and semiconductor insulation is formed on the surface of the semiconductor substrate It is characterized by applying a conductive adhesive, adhering an insulator substrate onto the semiconductor substrate, and removing the semiconductor substrate.

  The antenna integrated element of the present invention electrically connects the light receiving element whose light incident surface side is exposed to the space, the planar antenna whose one surface is exposed to the space, and the light receiving element and the planar antenna on the opposite side of the space. A wiring to be connected, an insulating adhesive for a semiconductor formed in a state of covering the light receiving element, the planar antenna and the wiring on the side opposite to the space, and an insulation formed in a state of covering the insulating adhesive for the semiconductor It is characterized by comprising a body substrate.

According to the antenna integrated element and the manufacturing method thereof of the present invention, an antenna integrated element capable of supporting a submillimeter wave band with a low loss of light incidence is utilized by utilizing a widely established semiconductor process technology suitable for mass production. Can be manufactured with good reproducibility and controllability.
Further, in the present invention, since it is not necessary to make the light receiving element into a chip, the upper limit of the band of the antenna needs to consider only the element size.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, the thing which has the same function in drawing demonstrated below attaches | subjects the same symbol, and the repeated description is abbreviate | omitted.

[Embodiment 1]
1A to 1H are sectional views of Embodiment 1 of the present invention.
The cross-sectional direction corresponds to BB ′ in FIG.

  First, as shown in FIG. 1A, an InGaAsP layer lattice-matched to an InP substrate is formed as an etching stopper layer 3 by epitaxial growth on a semiconductor substrate 1 made of InP. Thereafter, an epitaxial layer of the light receiving element 2 is formed by epitaxial growth. As the light receiving element, for example, a high output photodiode described in JP-A-9-275224 is suitable. It consists mainly of an n-type InP layer, a non-doped InP layer, and a p-type InGaAs layer. The InP and InGaAs layers are etched by a hydrochloric acid etching solution and a citric acid etching solution, respectively, to form a mesa structure of the light receiving element 2. Thereafter, ohmic contact electrodes are formed on the P-type and n-type layers, respectively.

  Next, the planar antenna 4 made of Ti / Au is formed as shown in FIG. 1B by a lift-off method using a photoresist.

  Further, as shown in FIG. 1C, after the insulating film 5 is formed, a wiring 6 made of Ti / Au is formed by a lift-off method using a photoresist.

Next, as shown in FIG. 1D, a high dielectric film 7 is formed on the surface side of the semiconductor substrate 1.
As a formation method, a sputtering method or a CVD method can be used.

  The high dielectric film 7 is preferably made of a material having a dielectric constant as high as possible. For example, titanium oxide (80), strontium titanate (300), bismuth strontium tantalate (250), barium strontium titanate (500), lead zirconate titanate (1000), etc. are suitable as the high dielectric film. The relative dielectric constant is shown in parentheses.

  Further, when the dielectric constant of the portion in contact with the antenna is increased, the effective wavelength of the electromagnetic wave is shortened. Accordingly, the size of the planar antenna is reduced. This can increase the element density on the substrate and increase the mass productivity. On the other hand, if the antenna size becomes too small, the antenna processing accuracy becomes a problem. It is necessary to design optimally among the maximum frequency of the electromagnetic wave to be generated, the dielectric constant of the high dielectric film, and the processing critical dimension.

  After that, as shown in FIG. 1E, the surface of the high dielectric film 7 is planarized by performing surface polishing.

Next, as shown in FIG. 1F, an insulator substrate 8 is bonded to the surface side of the high dielectric film 7.
It is preferable to use an insulating semiconductor adhesive or the like for bonding, but other bonding methods may be used.

Insulator substrate 8 is preferably made of a highly insulating material such as quartz or sapphire in order to prevent absorption of radiated electromagnetic waves. Alternatively, a highly insulating Si substrate may be used in consideration of the affinity with a silicon super-hemisphere lens that is often used for efficiently releasing electromagnetic waves into the space. In order to radiate electromagnetic waves more efficiently, a substrate made of an insulating material having a high dielectric constant, such as titanium oxide, strontium titanate, bismuth strontium tantalate, barium strontium titanate, lead zirconate titanate, or the like can be used. At this time, it goes without saying that the loss is further reduced if the material of the insulating substrate 8 matches the material of the high dielectric film 7.
Further, since there is no gap between the high dielectric film 7 and the insulating substrate 8, the problem of heat dissipation can be avoided.

Next, as shown in FIG. 1G, the semiconductor substrate 1 is removed.
First, the thickness of the semiconductor substrate 1 is reduced to 200 μm by a polishing process. Next, the remaining portion is removed by etching with a hydrochloric acid-based etching solution.
At this time, the progress of etching stops at the etching stopper layer 3 made of InGaAsP.

  Finally, as shown in FIG. 1H, the InGaAsP in the etching stopper layer 3 is etched with a sulfuric acid-based etchant. At this time, since the above etchant has a large selectivity with respect to InP, it is possible to substantially prevent the light receiving element 2 from being damaged by etching. If damage becomes a problem, the n-InP layer of the light receiving element 2 may be stacked thickly.

  Through such a manufacturing process, the antenna integrated element of Embodiment 1 is manufactured. The antenna integrated element according to the first embodiment is opposite to the light receiving element 2 in which the light incident surface side (light absorption layer side) is exposed to the space, the planar antenna 4 in which one surface (lower surface) is exposed to the space, and the space. A wiring 6 for electrically connecting the light receiving element 2 and the planar antenna 4 on the side, and a high dielectric film 7 formed so as to cover the light receiving element 2, the planar antenna 4 and the wiring 6 on the side opposite to the space The insulating substrate 8 is formed so as to cover the high dielectric film 7.

  Accordingly, when light is incident from the lower side of FIG. 1H, the light reaches the light absorption layer of the light receiving element 2 without being blocked by the wiring 6 and the planar antenna 4, and the loss is small.

  Further, the lower side (light incident direction) of the planar antenna 4 is exposed to a space (usually air), and electromagnetic waves radiated from the antenna are mainly radiated to the upper side (insulator substrate 8 side) having a high dielectric constant. . Since the radiation power is proportional to the 1/2 power of the dielectric constant, the efficiency of electromagnetic wave radiation can be improved by selecting a material having a high dielectric constant. In the conventional example, an InP substrate having a relative dielectric constant of 12.5 was used. However, in the manufacturing method of the present invention, a material having a higher relative dielectric constant, for example, a lead zirconate titanate material having a relative dielectric constant of 1000 is a high dielectric constant. When used for the body film 7 and the insulator substrate 8, the efficiency is improved from 78% for InP to 97% assuming that the substrate is sufficiently larger than the wavelength of the electromagnetic wave.

  For this reason, an antenna integrated element in which the loss of incident light is kept low and the directions of light incidence and electromagnetic wave radiation are opposite to each other can be manufactured with good reproducibility and controllability using semiconductor process technology.

Further, since the planar antenna 4 and the light receiving element 2 are formed on the same substrate, the light receiving element 2, the planar antenna 4 and the wiring 6 can be aligned with the accuracy of lithography as in the conventional example 1, and the submillimeter wave band. Transmission loss can be reduced even with ultra-high frequency signals. Therefore, the manufacturing method according to the present invention is suitable for manufacturing an antenna integrated element that handles ultra-high frequency electromagnetic waves.
In addition, since it is not necessary to make the light receiving element into a chip, the upper limit of the band of the antenna needs to consider only the element size.

[Embodiment 2]
2A to 2F are cross-sectional views of Embodiment 2 of the present invention.
First, as shown in FIG. 2A, the light receiving element 2 is formed on the InP substrate by the method described in the first embodiment.

  Next, the planar antenna 4 made of Ti / Au is formed as shown in FIG. 2B by a lift-off method using a photoresist.

  Further, as shown in FIG. 2C, after forming the insulating film 5, the wiring 6 made of Ti / Au is formed by a lift-off method using a photoresist.

  Next, as shown in FIG. 2D, the surface side of the semiconductor substrate 1 and the insulator substrate 8 are bonded with an insulating insulating adhesive 9 for semiconductor.

  At this time, a sufficient thickness of the adhesive is ensured so that the unevenness due to the planar antenna 4 and the light receiving element 2 on the surface of the semiconductor substrate 1 can be completely embedded. The insulator substrate 8 is as described in the first embodiment.

Next, as shown in FIG. 2E, the semiconductor substrate 1 is removed.
First, the thickness of the semiconductor substrate 1 is reduced to 200 μm by a polishing process. Next, the remaining portion is removed by etching with a hydrochloric acid-based etching solution.
At this time, the progress of etching stops at the etching stopper layer 3 made of InGaAsP.

  Finally, as shown in FIG. 2F, the InGaAsP in the etching stopper layer 3 is etched with a sulfuric acid-based etchant. At this time, since the above etchant has a large selectivity with respect to InP, it is possible to substantially prevent the light receiving element 2 from being damaged by etching.

  Through such a manufacturing process, the antenna integrated element of Embodiment 2 is manufactured. The antenna integrated element according to the second embodiment is opposite to the light receiving element 2 whose light incident surface side (light absorption layer side) is exposed to the space, the planar antenna 4 whose one surface (lower surface) is exposed to the space, and the space. A wiring 6 that electrically connects the light receiving element 2 and the planar antenna 4 on the side, and an insulating adhesive for semiconductor formed so as to cover the light receiving element 2, the planar antenna 4 and the wiring 6 on the side opposite to the space 9 and an insulating substrate 8 formed so as to cover the insulating adhesive 9 for semiconductor.

  In the second embodiment, it is possible to manufacture an antenna integrated element in which the loss of incident light is kept low and the directions of light incidence and electromagnetic wave radiation are opposite to each other with good reproducibility and controllability using semiconductor process technology. The same as in the first embodiment.

Further, in the second embodiment, there is a disadvantage that the electromagnetic radiation efficiency is reduced by omitting the process of forming a high dielectric film directly above the planar antenna, but the number of manufacturing steps is reduced, and the antenna integrated element can be reduced in a shorter time and at a lower cost. There is an advantage that can be produced.
In addition, since it is not necessary to make the light receiving element into a chip, the upper limit of the band of the antenna needs to consider only the element size.

  Although the present invention has been specifically described above based on the embodiment, the present invention is not limited to the above-described embodiment, and it is needless to say that various changes can be made without departing from the scope of the invention.

  For example, in the above embodiment, an example of a photodiode as a light receiving element has been described, but another light receiving element such as a phototransistor may be used.

Moreover, as long as the substrate 1 is a material capable of forming a light receiving element such as InP or GaAs,
Various semiconductor substrates may be used.

Also, other known solutions can be used for the etching solution.
Furthermore, as a film constituting the planar antenna 4, a conductive film such as graphite may be used in addition to the metal film.

It is sectional drawing which shows the process of the manufacturing method of the antenna integrated element of Embodiment 1 of this invention. It is sectional drawing which shows the process of the manufacturing method of the antenna integrated element of Embodiment 2 of this invention. It is a block diagram which shows the structure of the antenna integrated element of the prior art example 1. FIG. It is a block diagram which shows the structure of the antenna integrated element of the prior art example 2.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Semiconductor substrate 2 Light receiving element 3 Etching stopper layer 4 Planar antenna 5 Insulating film 6 Wiring 7 High dielectric film 8 Insulating substrate 9 Insulating adhesive for semiconductor 11 Semiconductor substrate 12 Planar antenna 13 Light receiving element 14 Wiring 15 Insulating film 16 Reflection Film 20 Light-receiving element 21 Light-receiving element chip 22 Transmission path on light-receiving element chip 23 Planar antenna chip 24 Planar antenna 25 Transmission path on planar antenna chip 26 Chip surface 27 Chip back surface 28 Pad

Claims (6)

A light receiving element made of a semiconductor formed on an insulator substrate, and a planar antenna electrically connected to the light receiving element by wiring; and from the side of the insulator substrate on which the planar antenna is formed In a method for manufacturing an antenna integrated element configured to cause an optical signal to enter the light receiving element,
Forming a light receiving element, a planar antenna, and wiring on a semiconductor substrate;
Forming a high dielectric film on the surface of the semiconductor substrate;
Flattening irregularities on the surface of the high dielectric film;
Bonding an insulating substrate on the high dielectric film;
And a step of removing the semiconductor substrate. A method for manufacturing an antenna integrated element. A light receiving element made of a semiconductor formed on an insulator substrate, and a planar antenna electrically connected to the light receiving element by wiring; and from the side of the insulator substrate on which the planar antenna is formed An antenna integrated element configured to cause an optical signal to enter the light receiving element,
A light receiving element, a planar antenna, and wiring are formed on a semiconductor substrate.
Forming a high dielectric film on the surface of the semiconductor substrate;
Flattening irregularities on the surface of the high dielectric film,
Adhering an insulating substrate on the high dielectric film,
An antenna integrated element, comprising: removing the semiconductor substrate. A light receiving element whose light incident surface side is exposed to the space;
A planar antenna with one surface exposed to the space;
Wiring for electrically connecting the light receiving element and the planar antenna on the opposite side of the space;
A high dielectric film formed in a state of covering the light receiving element, the planar antenna and the wiring on the side opposite to the space;
An antenna integrated element comprising: an insulating substrate formed so as to cover the high dielectric film. A light receiving element made of a semiconductor formed on an insulator substrate, and a planar antenna electrically connected to the light receiving element by wiring; and from the side of the insulator substrate on which the planar antenna is formed In a method for manufacturing an antenna integrated element configured to cause an optical signal to enter the light receiving element,
Forming a light receiving element, a planar antenna, and wiring on a semiconductor substrate;
Applying a semiconductor insulating adhesive to the semiconductor substrate surface;
Bonding an insulator substrate on the semiconductor substrate;
And a step of removing the semiconductor substrate. A method for manufacturing an antenna integrated element. A light receiving element made of a semiconductor formed on an insulator substrate, and a planar antenna electrically connected to the light receiving element by wiring; and from the side of the insulator substrate on which the planar antenna is formed An antenna integrated element configured to cause an optical signal to enter the light receiving element,
A light receiving element, a planar antenna, and wiring are formed on a semiconductor substrate.
Applying a semiconductor insulating adhesive to the semiconductor substrate surface,
Bonding an insulator substrate on the semiconductor substrate;
An antenna integrated element, comprising: removing the semiconductor substrate. A light receiving element whose light incident surface side is exposed to the space;
A planar antenna with one surface exposed to the space;
Wiring for electrically connecting the light receiving element and the planar antenna on the opposite side of the space;
An insulating adhesive for semiconductor formed in a state of covering the light receiving element, the planar antenna and the wiring on the opposite side of the space;
An antenna integrated element comprising: an insulating substrate formed so as to cover the semiconductor insulating adhesive.

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