JP2010114183A - Infrared radiation detector and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To practically use an infrared radiation detector using a silicon waveguide. <P>SOLUTION: The infrared radiation detector includes: a rib-type core layer 102 consisting of a monocrystal silicon and having a rib 121 and a slab 122 and a slab 123 formed at both sides of the rib 121; and in addition a loop-type crystal defect 124 which is formed at a center section in the cross-sectional direction of the rib 121. In the loop-type crystal defect 124 provided in the rib 121, a light is absorbed to carry out a carrier. The generated carrier is taken out to an external circuit by applying a reverse bias to a p-type impurity region 103 and an n-type impurity region 104. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an infrared detector composed of a rib-type silicon waveguide and a method for manufacturing the same.

  A waveguide using silicon as a core generally uses a silicon oxide film as a cladding layer, and the refractive index difference between them is about 0.4, which is several tens of times larger than that of a quartz-based waveguide. It is characterized by a large confinement effect due to the rate difference. In such an optical waveguide made of silicon, the cross-sectional dimension of the core satisfying the single mode condition is about 500 × 200 nm for an optical signal having a wavelength of about 1.55 μm for optical communication, and the number of silica-based waveguides is several hundred. The cross-sectional area is a fraction. In addition, the silicon waveguide can have a very small bending radius of several μm due to a high refractive index difference, and a minute optical integrated circuit can be formed. In addition, silicon is the most commonly used semiconductor material for electronic devices, and optoelectronic devices that combine silicon waveguides and electronic devices have also been developed.

  By the way, in order to incorporate and use the silicon waveguide as described above as a part of the optical communication system, it is important to be able to receive light by being coupled with a photodetector. As one method for realizing this, a waveguide type light receiving device in which slab portions on both sides of a silicon waveguide having a rib shape are p-type and n-type semiconductors, and a lattice defect is introduced into a rib portion where light propagates. A structure has been proposed (see Non-Patent Document 1).

  Normally, silicon transmits and does not absorb light in the vicinity of a wavelength of 1.55 μm for communication, and therefore does not serve as a photodetector in this wavelength band. However, when a lattice defect is introduced by ion implantation of a rare gas element such as argon or helium, or silicon, a light is absorbed and a carrier is generated in a portion where the lattice defect (multi-hole lattice defect) is introduced. . This carrier can be taken out to an external circuit by applying a reverse bias to the p-type and n-type semiconductors of the slab part on both sides of the rib part. As described above, the rib-type silicon waveguide having the above-described configuration can operate as an infrared light receiver that guides a waveguide including a silicon core.

MWGeis, et al., "CMOS-Compatible All-Si High-Speed Waveguide Photodiode With High Responsivity in Near-Infrared Communication Band", IEEE PHOTONICS TECHNOLOGY LETTERS, Vol.19, No.3, pp.152-154, 2007 . William C. O'Mara, et al., "HANDBOOK OF SEMICONDUCTOR SILICON TECHNOLOGY", NOYES PUBLICATIONS, p555, 1990. M. Takahashi, et al., "Source / Drain Ion Implantation into Ultra-Thin-Single-Crystalline-Silicon-Layer of Separation by IMplanted OXygen (SIMOX) Wafers", Jpn. J. Appl. Phys., Vol.35, pp.5237-5241, 1996. Koji Yamada, et al., “Nonlinear optical effect of silicon and its application”, Optics, Japan Society of Applied Physics, Japan Optical Society, Vol. 37, No. 1, pp. 27-34, 2008.

  By the way, in order to put the above-described infrared receiver (infrared detector) using a waveguide into practical use, it is important to form an electrode for obtaining an electrical output and an upper cladding layer that also protects the waveguide. . In these formations, a high temperature treatment of 400 to 500 ° C. is usually performed. However, it is known that the multi-hole lattice defect, which is the source of the function of the infrared detector described above, disappears due to the high temperature treatment of about 400 ° C., so that the function as the infrared detector is greatly impaired. (See Non-Patent Document 1). Thus, conventionally, there has been a problem that the infrared receiver configured as described above is not easy to use practically.

  The present invention has been made to solve the above-described problems, and an object thereof is to enable practical use of an infrared detector using a silicon waveguide.

  An infrared detector according to the present invention is a rib type formed of a single crystal silicon, which is formed on a lower clad layer and includes a rib portion and first and second slab portions formed on both sides of the rib portion. A core layer, a p-type impurity region connected to the first slab portion, an n-type impurity region connected to the second slab portion, a loop-type crystal defect formed in a central portion in the cross-sectional direction of the rib portion, and a core And an upper clad layer covering the layer, a first electrode connected to the p-type impurity region, and a second electrode connected to the n-type impurity region.

  In addition, the method for manufacturing an infrared detector according to the present invention comprises a single crystal silicon including a rib portion and a first slab portion and a second slab portion formed on both sides of the rib portion on the lower clad layer. Forming a rib-type core layer, forming a p-type impurity region in the first slab portion, forming an n-type impurity region in the second slab portion, and a first slab portion including the rib portion Forming an amorphous region of silicon by ion implantation in a partial region of the second slab portion and recrystallizing the amorphous region by heat treatment to form a loop-type crystal defect in the rib portion; At least a step of forming an upper clad layer covering the layer, a step of forming a first electrode connected to the p-type impurity region, and a step of forming a second electrode connected to the n-type impurity region. The formation of the crystalline region is A method con has to perform an ion implantation of elements does not exhibit conductivity type p-type and n-type.

  In the manufacturing method of the infrared detector, the amorphous region of silicon may be formed by ion implantation of an element selected from a rare gas element, silicon, and germanium. Further, the recrystallization of the amorphous region may be performed by a heat treatment in the range of 600 to 1000 ° C.

  As described above, according to the present invention, since the loop type crystal defect is formed in the central portion of the rib portion in the cross-sectional direction, an infrared detector using a silicon waveguide can be used practically. An excellent effect is obtained.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view schematically showing a configuration example of an infrared detector according to an embodiment of the present invention. This infrared detector first includes a lower clad layer 101, a slab part (first slab part) 122 formed on both sides of the rib part 121 and the rib part 121, and a slab. And a rib-type core layer 102 having a portion (second slab portion) 123. For example, the rib 121 has a width of 500 nm and a height (thickness) of 200 nm. Moreover, the slab parts 122 and 123 are 50-50 nm in thickness, for example. Such a rib-type core layer 102 is made of single crystal silicon.

  The infrared detector in the present embodiment includes a p-type impurity region 103 connected to the slab part 122 and an n-type impurity region 104 connected to the slab part 123. In addition, an upper clad layer 105 covering the core layer 102, an electrode (first electrode) 106 connected to the p-type impurity region 103, and an electrode (second electrode) 107 connected to the n-type impurity region 104 are provided.

  In addition, the infrared detector in the present embodiment includes a loop-type crystal defect 124 formed in the central portion of the rib portion 121 in the cross-sectional direction. In the present embodiment, light is absorbed in the loop-type crystal defect 124 provided in the rib portion 121 to generate carriers, and the generated carriers are applied with a reverse bias to the p-type impurity region 103 and the n-type impurity region 104. Take it out to the external circuit.

  Here, infrared detection will be described. The principle of infrared light reception by lattice defects is that the energy level is formed in the band gap of silicon due to the introduced lattice defect, and the valence band electrons are excited by the infrared to the conductor via this energy level. It has been. In particular, the double-vacancy lattice defect forms an energy level in the vicinity of the center of the band gap, and is an appropriate intermediate level for infrared rays having energy lower than that of silicon. In other words, in infrared detection using a silicon waveguide, it is considered important to introduce a lattice defect having energy near the center of the band gap of silicon into the core (rib portion).

  Therefore, if a lattice defect that has an energy level almost in the center of the band gap of silicon and that is stable against the thermal load applied by the formation of each upper layer can be introduced into the core, high-temperature treatment is performed after the lattice defect is introduced. Even after passing, a highly sensitive infrared detector can be realized without impairing the function of infrared detection. As a lattice defect that satisfies such conditions, a dislocation loop (loop-type crystal defect) in which dislocations and dislocations are formed in a ring shape can be considered.

  Loop-type crystal defects in silicon are those in which primary defects such as single vacancies and interstitial atoms are separated and concentrated by heat treatment at a high temperature of 600 ° C. or higher. For this reason, it is a stable lattice defect at least at a temperature lower than 600 ° C. In addition, the energy level of the loop-type crystal defect formed in this way is located substantially at the center of the silicon band gap, as in the case of the double-hole lattice defect (see Non-Patent Document 2). Therefore, by using the loop type crystal defect 124, when forming the upper clad layer 105 and the electrodes 106 and 107, a practical infrared ray in which a decrease in sensitivity is suppressed even when a high temperature treatment of 400 to 500 ° C. is performed. A detector can be realized.

  Next, an example of a method for manufacturing the infrared detector according to the embodiment of the present invention will be described. First, as shown in the cross-sectional view of FIG. 2, the core layer 102 including the rib portion 121, the slab portion 122, and the slab portion 123 is formed on the single crystal silicon layer 201 on the lower cladding layer 101. For example, the lower cladding layer 101 is a well-known buried insulating layer of an SOI (Silicon on Insulator) substrate, and the single crystal silicon layer 201 is an SOI layer. The single crystal silicon layer 201 is patterned by a known photolithography technique and etching technique to selectively remove the slab part 122 and the region to be the slab part 123 and extend in the normal direction of the paper surface of FIG. As a result, the rib 121 serving as the core of the waveguide is formed.

  Next, as shown in the cross-sectional view of FIG. 3, a p-type impurity region 103 connected to the slab part 122 and an n-type impurity region 104 connected to the slab part 123 are formed. For example, first, a mask pattern in which a region to be the p-type impurity region 103 is opened is formed, and p-type impurities such as boron are ion-implanted. Further, a mask pattern in which a region to be the n-type impurity region 104 is opened is formed, and n-type impurities such as phosphorus are ion-implanted. Next, annealing is performed, for example, at a temperature of 800 ° C. or higher in order to recrystallize the amorphous state (crystal defects) generated by the ion implantation and to activate the introduced impurity atoms. As a result, the p-type impurity region 103 and the n-type impurity region 104 are formed.

  Next, as shown in the cross-sectional view of FIG. 4, a resist mask layer 401 including an opening 402 is formed on the single crystal silicon layer 201 by a known photolithography technique. For example, the resist mask layer 401 can be formed by exposing and developing a resist layer sensitive to ultraviolet rays with an ultraviolet exposure device. Alternatively, the resist mask layer 401 may be formed by exposing and developing a resist layer sensitive to an electron beam by an electron beam exposure apparatus.

  The opening 402 only needs to be open in the extending direction of the rib portion 121 in a region where an infrared detection function is to be developed. The opening 402 is in a state in which a predetermined region centered on the rib 121 is opened in the width direction perpendicular to the extending direction. The opening width of the opening 402 may be the same as that of the rib 121 or a range slightly wider than the rib 121.

Next, using the resist mask layer 401 as a mask for restricting ion implantation, ion implantation is performed on a partial region of the slab part 122 and the slab part 123 including the rib part 121 exposed to the opening 402. For example, a region exposed to the opening 402 may be irradiated with 130 keV argon ions at a density of 2 × 10 ¹⁴ cm ⁻² . In this ion implantation, a rare gas element such as argon or krypton, or an element such as silicon or germanium may be used. In this ion implantation, ions of an element that does not become n-type or p-type even if introduced into silicon may be implanted.

By the ion implantation described above, as shown in FIG. 5, a defect region 501 in which primary lattice defects such as interstitial atoms and vacancies are formed in the ion implanted region. Here, the above-described ion implantation is performed so that the lattice defect density is 2 × 10 ²² cm ⁻³ or more so that the defect region 501 can be regarded as an amorphous state (see Non-Patent Document 3). After ion implantation, the resist mask layer 401 is removed.

  As described above, an amorphous region is formed in a partial region of the slab portion 122 and the slab portion 123 including the rib portion 121, and after the resist mask layer 401 is removed, heat treatment for recrystallization of crystal defects is performed. Do. By this heat treatment, as shown in the cross-sectional view of FIG. 6, the crystal part 122a of the slab part 122 and the crystal part 123a of the slab part 123 are used as seed crystals, and the rib part is formed from the outer side in the width direction of the defect region 501 by solid phase epitaxial recovery. Recrystallization proceeds to the center of 121.

  In this way, the recrystallized surface that has advanced from both outer sides to the central portion of the rib portion 121 meets at the central portion of the rib portion 121. And secondary defects such as dislocations are formed. As a result, as shown in the cross-sectional view of FIG. 7, the loop type crystal defect 124 is formed concentrated on the central portion of the rib portion 121.

  Here, if the width of the defect region 501 defined by the width of the opening 402 of the resist mask layer 401 is too large, the above-described portion where the crystallized surface of recrystallization progressing from both sides meets the center of the rib portion 121. The case where it deviates from the part comes to occur. In other words, if the width of the defective road oil region 501 is too large, the positional accuracy at which the loop type crystal defect is formed deteriorates. From the viewpoint of ensuring the positional accuracy, it is preferable that the width of the crystal defect region 501 is not more than twice the width of the rib portion 121. Further, the crystal defect region 501 has a range that does not overlap with the p-type impurity region 103 and the n-type impurity region 104.

  The heating temperature range for forming the loop-type crystal defect 501 by recrystallization considers the following. First, in solid phase epitaxial growth, it is important to heat to 600 ° C. or higher at which lattice defects and atoms can move in crystalline silicon. In addition, it has been reported that loop-type crystal defects are formed in a short time with a processing time of 15 minutes under the heating condition of 900 ° C. (see Non-Patent Document 4). It is presumed that the movement of defects becomes intense and the formation of loop-type crystal defects proceeds in seconds. In such a state, there is a possibility that lattice defects may disappear through the formation of very large loop-type crystal defects. When heating at a temperature exceeding 1000 ° C., loop-type crystal defects having desired characteristics are formed with good controllability. Is estimated to be difficult. Therefore, it is appropriate that the above-described heating temperature range is 600 to 1000 ° C. For example, the heat treatment may be performed at 900 ° C. for 15 minutes, for example.

  As described above, after forming the loop type crystal defect 124 at the center of the rib 121, as shown in the cross-sectional view of FIG. 8, a silicon oxide film is formed on the single crystal silicon layer 201 by, for example, CVD. Is deposited to form the upper clad layer 105. Thereafter, the upper clad layer 105 is patterned by a known photolithography technique and etching technique to form openings that penetrate the partial regions of the p-type impurity region 103 and the n-type impurity region 104, respectively. Next, on the upper clad layer 105 in which each opening is formed, a metal layer such as aluminum is deposited by, for example, a CVD method or a sputtering method to form a metal layer, and this metal layer is formed by a known photolithography technique and etching. Patterning is performed using technology to form the electrode 106 and the electrode 107.

  As described above, in the deposition of the silicon oxide film by the CVD method and the formation of the metal layer, the processing temperature is 400 to 500 ° C. According to the present embodiment, the loop type crystal formed in the rib portion 121. The defect 124 never disappears.

  In the above description, the loop crystal defect 124 is formed after the annealing process for forming the p-type impurity region 103 and the n-type impurity region 104. However, the present invention is not limited to this. In the formation of the p-type impurity region 103 and the n-type impurity region 104, in order to further diffuse the ion-implanted ions, a temperature treatment higher than the annealing of the loop-type crystal defect 124 is required. After the annealing process for forming the p-type impurity region 103 and the n-type impurity region 104, the loop-type crystal defect 124 is formed.

  However, when it is not necessary to diffuse the implanted ions so much, the same annealing conditions as those for forming the loop-type crystal defect 124 can be applied to the formation of the p-type impurity region 103 and the n-type impurity region 104. In such a case, for example, after ion implantation for the p-type impurity region 103 and the n-type impurity region 104 and ion implantation for the loop-type crystal defect 124 are performed, annealing treatment for forming the impurity region is performed. Further, the annealing process for forming the loop type crystal defect 124 may be performed simultaneously.

It is sectional drawing which shows typically the structural example of the infrared detector in embodiment of this invention. It is sectional drawing for demonstrating the example of the manufacturing method of the infrared detector in embodiment of this invention. It is sectional drawing for demonstrating the example of the manufacturing method of the infrared detector in embodiment of this invention. It is sectional drawing for demonstrating the example of the manufacturing method of the infrared detector in embodiment of this invention. It is sectional drawing for demonstrating the example of the manufacturing method of the infrared detector in embodiment of this invention. It is sectional drawing for demonstrating the example of the manufacturing method of the infrared detector in embodiment of this invention. It is sectional drawing for demonstrating the example of the manufacturing method of the infrared detector in embodiment of this invention. It is sectional drawing for demonstrating the example of the manufacturing method of the infrared detector in embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 101 ... Lower clad layer, 102 ... Core layer, 103 ... P-type impurity region, 104 ... N-type impurity region, 105 ... Upper clad layer, 106 ... Electrode (first electrode), 107 ... Electrode (second electrode), 121 ... rib part, 122 ... slab part (first slab part), 123 ... slab part (second slab part), 124 ... loop type crystal defect.

Claims (4)

A rib-type core layer formed on the lower cladding layer and made of single crystal silicon, the rib-type core layer including a rib portion and first and second slab portions formed on both sides of the rib portion;
A p-type impurity region connected to the first slab portion;
An n-type impurity region connected to the second slab portion;
A loop-type crystal defect formed in a central portion in the cross-sectional direction of the rib portion;
An upper cladding layer covering the core layer;
A first electrode connected to the p-type impurity region;
An infrared detector comprising at least a second electrode connected to the n-type impurity region. Forming a rib-type core layer comprising a rib portion and a first slab portion and a second slab portion formed on both sides of the rib portion on the lower clad layer; and
Forming a p-type impurity region connected to the first slab portion;
Forming an n-type impurity region connected to the second slab part;
An amorphous region of silicon is formed by ion implantation in a partial region of the first slab portion and the second slab portion including the rib portion, and the amorphous region is recrystallized by heat treatment to thereby form the rib. Forming a loop-type crystal defect in the part;
Forming an upper clad layer covering the core layer;
Forming a first electrode connected to the p-type impurity region;
Forming a second electrode connected to the n-type impurity region, and
The method for manufacturing an infrared detector is characterized in that the amorphous region of silicon is formed by ion implantation of an element whose silicon does not exhibit p-type and n-type conductivity types. In the manufacturing method of the infrared detector of Claim 2,
The method for producing an infrared detector is characterized in that the amorphous region of silicon is formed by ion implantation of an element selected from a rare gas element, silicon, and germanium. In the manufacturing method of the infrared detector of Claim 2 or 3,
The method for manufacturing an infrared detector, wherein the recrystallization of the amorphous region is performed by a heat treatment in a range of 600 to 1000 ° C.

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