JP2009283638A - Method of manufacturing waveguide type photodetector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a waveguide type photodetector, wherein a lattice defect concentrates only on the center portion of a rib-type waveguide of a semiconductor even in the case of using an exposure apparatus of which the resolution is equal to or higher than the width of the rib-type waveguide. <P>SOLUTION: In the method of manufacturing a waveguide type photodetector wherein a rib-type waveguide 1 made of a semiconductor has a lattice defect 7 in the center portion and slab portions 2 on both sides of the rib-type waveguide 1 are a p-type semiconductor and an n-type semiconductor respectively, the lattice defect 7 of the rib-type waveguide 1 is formed by: an ion implantation process of implanting ions to a prescribed region including a portion which forms the lattice defect 7 until the prescribed region is made amorphous from a single crystalline state into an amorphous region 5 after the rib-type waveguide 1 and the slab portions 2 are formed; and a heat treatment process of applying heat after the ion implantation process until the amorphous region 5 is recrystallized (RC) from both outer sides of the amorphous region 5 toward the center portion of the rib-type waveguide 1 to have a desired width. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method of manufacturing a waveguide type light receiver formed on the same substrate as a semiconductor optical waveguide and connected thereto.

  An electromagnetic wave waveguide using silicon, which is a semiconductor, as a core generally uses a silicon oxide film as a cladding layer, and its relative refractive index difference is about 0.4, which is several tens of times larger than that of a silica-based waveguide. The confinement effect due to the rate difference is very large. For an electromagnetic wave having a wavelength of about 1.55 μm for optical communication, the core size satisfying the single mode condition is about 500 × 200 nm, which is a cross-sectional area of several hundredths of that of a silica-based waveguide. Further, because of this high refractive index difference, a minute bending radius of several microns is possible, and a minute optical integrated circuit can be formed. Silicon is also used in the manufacture of electronic devices, and development of optoelectronic devices combining electromagnetic wave waveguides and electronic devices is also being studied.

  By the way, in order to use the silicon electromagnetic wave waveguide as described above as a part of the optical communication system, it is necessary to receive light in combination with a photodetector. For this reason, a waveguide type light receiver as shown in FIG. 1 has been proposed (see Non-Patent Document 1). FIG. 1 is a cross-sectional view illustrating the structure of a waveguide type light receiver. The waveguide type light receiver shown in FIG. 1 has a surface of the slab portion 2 on both sides of the rib-type waveguide 1 through which light propagates as a high-concentration impurity p-type semiconductor 14 and a high-concentration impurity n-type semiconductor 16. The side surface of 1 and the surface of the slab portion 2 in the vicinity of the rib-type waveguide 1 are a low-concentration impurity p-type semiconductor 15 and a low-concentration impurity n-type semiconductor 17, and the rib-type waveguide 1 has a lattice defect 7. Normally, silicon does not absorb light in the vicinity of a wavelength of 1.55 μm for communication, so it does not serve as a photodetector in this wavelength band. However, if a lattice defect 7 is formed in the rib-type waveguide 1, the light is absorbed and the carrier is absorbed. Is generated. The waveguide type light receiver shown in FIG. 1 is provided between a low-concentration impurity p-type semiconductor 15 and a low-concentration impurity n-type semiconductor 17 via a metal 11, a high-concentration impurity p-type semiconductor 14, and a high-concentration impurity n-type semiconductor 16. By applying a reverse bias to the carrier, this carrier can be taken out to an external circuit and can operate as a light receiver.

The lattice defect 7 is formed by ion implantation of a rare gas element such as argon or helium or silicon. Specifically, a mask in which only a portion where a lattice defect is to be formed in the rib waveguide is formed by a lithography process, and then ion implantation is performed. Only the opening is not implanted into the portion where the mask is formed, and lattice defects are formed in the silicon in the opening.
M.M. W. Geis et al., “CMOS-Compatible All-Si High-Speed Waveguide Photodiodes With High Responsibility in Near-Infrared Communication Band.” 19, no. 3, pp. 152-154 (2007) “Source / Drain Ion Implantation into Ultra-Thin-Single-Crystalline-Silicon-Layer of Separated by Oxygen (SIMOX) Wafers”, Jpn. J. et al. Appl. Phys. Vol. 35 (1996) pp. 5237-5241, Part 1, no. 10. Koji Yamada et al., “Nonlinear optical effect of silicon and its application”, optics 37, 1, pp. 27-34 (2008)

  Here, when the opening of the mask extends to the slab part and a lattice defect is formed to the slab part, a current (dark current) flows through the lattice defect when the reverse bias is applied, and the minimum light receiving sensitivity is deteriorated. In order to prevent such dark current, it is necessary to accurately form a lattice defect only in the central portion of the rib waveguide. For this reason, it is necessary to make the opening of the mask equal to or smaller than the width of the rib waveguide, and the exposure apparatus in the lithography process is required to have a resolution equal to or smaller than the width of the rib waveguide. However, as described above, the width of the rib-type waveguide is about 500 nm, and in order to accurately form a lattice defect only in the central portion of the rib-type waveguide, an electron beam or a depth sufficiently smaller than 500 nm is used. There was a problem that an expensive and low-exposure exposure apparatus using ultraviolet light (DUV) was required.

  Therefore, the present invention has been made to solve the above problems, and even when an exposure apparatus having a resolution equal to or larger than the width of the rib-type waveguide is used, the lattice defect is only in the central portion of the rib-type waveguide of the waveguide. An object of the present invention is to provide a method for manufacturing a waveguide type light receiver that concentrates on the substrate.

  In order to achieve the above object, a method for manufacturing a waveguide-type light receiver according to the present invention is characterized in that a semiconductor is made amorphous by performing ion implantation in a range wider than the width of a lattice defect formed in a rib-type waveguide. A step of forming a region, and a step of concentrating and forming lattice defects at the center of the rib portion by performing heat treatment.

  Specifically, in the method for manufacturing a waveguide type photoreceiver according to the present invention, a semiconductor rib-type waveguide has a lattice defect at the center, and each of the slab portions on both sides of the rib-type waveguide is p. A method of manufacturing a waveguide type photoreceiver that is an n-type semiconductor and an n-type semiconductor, wherein the lattice defect of the rib-type waveguide is formed, and after the rib-type waveguide and the slab portion are formed, the lattice defect is formed An ion implantation step of implanting ions into the predetermined region until the predetermined region including the portion to be amorphized from the single crystal becomes an amorphous region, and after the ion implantation step, from both outer sides of the amorphous region The amorphous region is recrystallized toward the central portion of the rib-type waveguide, and is formed by a heat treatment process in which heat is applied until the amorphous region has a desired width.

  In the ion implantation process, the semiconductor is formed with an amorphous region which is ion-implanted and a single-crystal region which is left without being implanted into the periphery of the amorphous region. When heat treatment is performed in the heat treatment step, the amorphous region is recrystallized from the outside to the center by solid phase epitaxial recovery using the single crystal region as a seed crystal. Therefore, even if the amorphous region is wider than the width of the lattice defect formed in the rib-type waveguide, the desired lattice defect width can be obtained by adjusting the temperature and time of the heat treatment.

  Therefore, the present invention provides a method for manufacturing a waveguide type light receiving device in which lattice defects are concentrated only in the central portion of the rib type waveguide of the waveguide even when an exposure apparatus having a resolution equal to or larger than the width of the rib type waveguide is used. Can be provided.

  The rib-type waveguide of the waveguide-type photodetector and the semiconductor of the slab portion can be silicon. A waveguide type light receiver capable of receiving light having a wavelength of about 1.55 μm for optical communication can be manufactured.

  The ions to be implanted in the ion implantation step of the method for manufacturing a waveguide type light receiver according to the present invention are preferably noble gas, silicon or germanium ions. Since it does not become an n-type or p-type impurity even in silicon, the characteristics of the waveguide type light receiver can be maintained.

  In the heat treatment step of the waveguide type light receiving device manufacturing method according to the present invention, it is preferable to apply heat of 600 ° C. to 1000 ° C. First, in solid phase epitaxial growth, it is necessary to heat to 600 ° C. or higher at which lattice defects and atoms can move in crystalline silicon. On the other hand, it has been reported that a dislocation loop is formed in 900 minutes at a short time of 15 minutes (see, for example, Non-Patent Document 3). For this reason, when the temperature exceeds 1000 ° C., the movement of lattice defects becomes severe, and it is estimated that the formation of dislocation loops proceeds in seconds. As a result, the lattice defects may disappear through the formation of very large dislocation loops. There is. Therefore, dislocation loops with desired characteristics can be formed with good controllability by heat treatment at 600 ° C. or higher and 1000 ° C. or lower.

  The present invention provides a method of manufacturing a waveguide type light receiver in which lattice defects are concentrated only in the central portion of the rib type waveguide of the waveguide even if an exposure apparatus having a resolution equal to or greater than the width of the rib type waveguide is used. be able to.

  Embodiments of the present invention will be described with reference to the accompanying drawings. The embodiment described below is an example of the configuration of the present invention, and the present invention is not limited to the following embodiment. In the present specification and drawings, the same reference numerals denote the same components.

  2 to 5 are cross-sectional views of the waveguide type light receiver for explaining the method for manufacturing the waveguide type light receiver of the present embodiment.

  In the method of manufacturing the waveguide type photoreceiver of the present embodiment, the semiconductor rib-type waveguide 1 has a lattice defect 7 in the center, and each of the slab portions 2 on both sides of the rib-type waveguide 1 is a p-type semiconductor. And a method of manufacturing a waveguide type optical receiver that is an n-type semiconductor, wherein the lattice defect 7 of the rib-type waveguide 1 is formed after the rib-type waveguide 1 and the slab portion 2 are formed. An ion implantation step in which ions are implanted into the predetermined region until the predetermined region containing amorphized from the single crystal becomes the amorphous region 5, and after the ion implantation step, a rib type is formed from both sides of the amorphous region 5 The amorphous region 5 is recrystallized toward the central portion of the waveguide 1 and is formed by a heat treatment process in which heat is applied until the amorphous region 5 has a desired width.

  In the following description, it is assumed that the semiconductor of the rib-type waveguide 1 and the slab portion 2 is silicon. However, the semiconductor is not limited to silicon, and the same applies to germanium and compound semiconductors. Although the description will be given assuming that the width of the rib-type waveguide is 500 nm, this width is not limited to 500 nm and may be wide or narrow.

The substrate 3 is, for example, a silicon dioxide (SiO ₂ ) layer formed on a silicon wafer. The rib-type waveguide 1 and the slab portion 2 are formed of single crystal silicon on the substrate 3 until the ion implantation step. FIG. 2 is a diagram illustrating an ion implantation process. First, as shown in FIG. 2, an ion implantation limiting mask 4 is formed in a wider area than the rib-type waveguide 1 using an exposure apparatus. For example, as the exposure apparatus, a widespread exposure apparatus having a resolution larger than 500 nm, such as that using g-ray ultraviolet rays of a mercury lamp, can be used. In FIG. 2, the opening of the mask 4 is drawn wider than the width of the rib-type waveguide 1, but may be wider than the width of the lattice defect 7 of FIG. 5 depending on the resolution of the exposure machine.

  Next, as shown in FIG. 2, ion implantation I / I is performed from the rib-type waveguide 1 and slab part 2 side. As an element used for the ion implantation I / I, it is necessary to select ions of an element that does not become an n-type impurity or a p-type impurity even in a rare gas atom such as argon or krypton, or silicon such as silicon or germanium. In the case of a semiconductor other than silicon, ions of elements that do not become n-type impurities or p-type impurities in the semiconductor are selected.

Lattice defects such as interstitial atoms and vacancies are generated in the range that was the opening of the mask 4 by the ions implanted in the ion implantation step of FIG. The ion implantation I / I is performed until the lattice defect density at which silicon can be regarded as amorphous becomes 2 × 10 ²² cm ⁻³ or more (for example, see Non-Patent Document 2). The mask 4 for limiting ion implantation may be removed after the ion implantation I / I is completed. FIG. 3 is a diagram for explaining the state after the ion implantation step. As shown in FIG. 3, the amorphous region 5 is formed after the ion implantation process. The outside of the amorphous region 5 is a single crystal region 6.

  FIG. 4 is a diagram for explaining the heat treatment process. When heat treatment is performed in a state where the amorphous region 5 and the single crystal region 6 are in contact with each other, recrystallization RC proceeds from the outside to the center by solid phase epitaxial recovery using the single crystal region 6 as a seed crystal.

  FIG. 5 is a diagram for explaining the state after the heat treatment step. In the heat treatment step, the recrystallized plane that has advanced from both ends of the amorphous region 5 to the central portion meets at the central portion, where the crystal planes do not match and lattice defects 7 such as dislocations are formed as shown in FIG. . The lattice defect 7 having a desired width can be formed by adjusting the time and temperature of the heat treatment step. For example, the width of the lattice defect 7 can be accurately controlled by setting the temperature of the heat treatment to 600 ° C. or more and 1000 ° C. or less. In the case of a semiconductor other than silicon, the temperature is set so that the width of the lattice defect 7 can be accurately controlled.

  After the heat treatment step, ion implantation is performed so that the surface of the slab portion 2 and the side surface of the rib-type waveguide 1 are p-type or n-type, and then a metal such as Al or Ti is formed at a predetermined position. A waveguide type light receiver structure as shown in FIG.

  If the manufacturing method described with reference to FIGS. 2 to 5 is used, even if an ion implantation mask is formed using an exposure apparatus having a high resolution, that is, an already widespread exposure apparatus, lattice defects are concentrated at the center of a narrow rib-type waveguide. Can be formed. For this reason, an optoelectronic device combining an electromagnetic wave waveguide and an electronic device can be manufactured at low cost and in large quantities.

  The manufacturing method according to the present invention is not limited to the waveguide type light receiver, but can be applied to an optoelectronic device in which an electromagnetic wave waveguide and an electronic device are combined.

It is a figure explaining the structure of a waveguide type light receiver. It is sectional drawing of the waveguide type light receiver explaining the manufacturing method of the waveguide type light receiver which concerns on this invention. It is sectional drawing of the waveguide type light receiver explaining the manufacturing method of the waveguide type light receiver which concerns on this invention. It is sectional drawing of the waveguide type light receiver explaining the manufacturing method of the waveguide type light receiver which concerns on this invention. It is sectional drawing of the waveguide type light receiver explaining the manufacturing method of the waveguide type light receiver which concerns on this invention.

Explanation of symbols

1: rib-type waveguide 2: slab portion 3: substrate 4: mask 5: amorphous region 6: single crystal region 7: lattice defect 11: metal 14: high-concentration impurity p-type semiconductor 15: low-concentration impurity p-type semiconductor 16: High-concentration impurity n-type semiconductor 17: Low-concentration impurity n-type semiconductor I / I: Ion implantation RC: Recrystallization

Claims (4)

A semiconductor rib-type waveguide has a lattice defect at the center, and a slab portion on each side of the rib-type waveguide is a p-type semiconductor and an n-type semiconductor, respectively. ,
The lattice defects of the rib-type waveguide are
After forming the rib waveguide and the slab portion, ions are implanted into the predetermined region until the predetermined region including the portion where the lattice defect is formed becomes amorphous from a single crystal to become an amorphous region. An injection process;
After the ion implantation step, the amorphous region is recrystallized from both outer sides of the amorphous region toward the center of the rib-type waveguide, and heat is applied until the amorphous region has a desired width. A heat treatment step of adding
A method for manufacturing a waveguide-type light receiver, characterized by comprising:   2. The method of manufacturing a waveguide receiver according to claim 1, wherein the semiconductor of the rib waveguide and the slab portion is silicon.   3. The method of manufacturing a waveguide type light receiving device according to claim 2, wherein ions implanted in the ion implantation step are ions of a rare gas, silicon, or germanium.   4. The method of manufacturing a waveguide receiver according to claim 2, wherein in the heat treatment step, heat of 600 ° C. or more and 1000 ° C. or less is applied. 5.

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