JP2009192588A - Shg element and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To increase the productivity of the SHG element in: an SHG element which has periodical polarization inversion regions formed on a ferroelectric substrate and also has an optical waveguide overlapping with the regions; and a method of manufacturing the same. <P>SOLUTION: The SHG element 1 is formed by further sticking a silicon substrate 7 on a principal surface of a protective film 6 constituting the SHG element 1, and polishing an incident/projection surface of the optical waveguide 3, formed of end surfaces of the ferroelectric substrate 4, protective film 6, and silicon substrate 7, as the same polished surface. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an SHG element having an optical waveguide in which a periodic domain-inverted region is formed in a ferroelectric substrate and overlaps the region, and a method of manufacturing the SHG device.

  An optical second harmonic generating element (having an optical waveguide that forms a periodic domain-inverted region on a conventional ferroelectric substrate and overlaps the region, and converts the wavelength of the incident light beam to the opposite wavelength) Hereinafter, the SHG element) has a configuration in which a protective film is provided on the main surface of a ferroelectric substrate in which a trench constituting an optical waveguide having a support substrate bonded to the back surface is formed.

  When forming such an SHG element, first, a support substrate is attached to the back surface of the ferroelectric substrate on which the domain-inverted regions are formed, and then the ferroelectric substrate is polished in the thickness direction to obtain a desired thickness. Next, a trench constituting an optical waveguide is formed on the main surface of the ferroelectric substrate, and a protective film is formed on the surface thereof. Thereafter, the substrate is divided into individual pieces by dicing and the end surfaces are polished.

As prior art document information related to the invention of this application, for example, Patent Document 1 is known.
JP 2006-18243 A

  However, in the SHG element formed in this way, since the trench portion constituting the optical waveguide is disposed close to the outer peripheral surface of the SHG element, the individual division by dicing in the batch forming of a large number using a wafer, In the polishing of the light incident / exit surface of the optical waveguide, a large processing stress is concentrated on the end portion of the trench, resulting in cracking and chipping in the manufacturing process of the SHG element.

  Therefore, the present invention aims to solve such problems and increase the productivity of SHG elements.

  In order to achieve this object, the present invention provides a ferroelectric substrate, a protective film, and a protective substrate, in which a silicon substrate is further bonded to the main surface of the protective film constituting the SHG element, and the incident / exit surface of the optical waveguide is a polished surface. The end surface of the silicon substrate is the same polished surface.

  With this configuration, the productivity of the SHG element can be improved.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 shows a cross-sectional structure of a state in which the SHG element 1 is mounted on a metal base 2. A support substrate 5 is bonded to the main surface of a ferroelectric substrate 4 on which an optical waveguide 3 is formed. The protective film 6 and the silicon substrate 7 are bonded to one main surface on the opposite side.

  The ferroelectric substrate 4 is a magnesium-doped 5 ° Y-Cut lithium niobate substrate, the support substrate 5 is a Y-Cut lithium niobate substrate, and the protective film 6 is silicon oxide. Is used.

  Further, as will be described later with reference to FIG. 2, the ferroelectric substrate 4 has a pair of trenches 8 formed on one main surface on which the protective film 6 is provided, and a ridge 9 formed between the trenches 8 is an optical waveguide. 3 and a plurality of domain-inverted regions 10 are periodically arranged in the extending direction of the optical waveguide 3 to perform wavelength conversion.

  As a manufacturing method thereof, as shown in FIG. 2, a comb-shaped aluminum electrode formed in a pattern corresponding to the pitch and width of the domain-inverted structure on the main surface of the wafer-like ferroelectric substrate 4 having a thickness of about 300 μm. 11 is formed by photolithography, and an aluminum electrode 12 is formed on substantially the entire back surface. Next, by applying a pulse electric field between the comb-shaped aluminum electrode 11 and the aluminum electrode 12, the domain-inverted regions 10 are formed in the Z-axis direction from the respective combs, and then immersed in an alkaline etchant to form the comb-shaped aluminum. The electrode 11 and the aluminum electrode 12 are removed.

  Then, after the support substrate 5 having a thickness of about 200 μm is bonded to the surface on which the comb-shaped aluminum electrode 11 is provided using the epoxy adhesive 13, until the ferroelectric substrate 4 becomes about 4.5 μm. A pair of trenches 8 are formed by mirror polishing and then dry etching, and a ridge 9 (optical waveguide 3) having a width of about 10 μm and a height of about 1.5 μm is formed therebetween.

  In the case where the support substrate 5 and the ferroelectric substrate 4 are directly bonded, unlike the case of bonding with the adhesive 13, there is no difference in the refractive index of the substrate material to be bonded, and signal leakage from the optical waveguide 3 occurs. Therefore, although not shown in particular, it is necessary to provide a gap for filling a material such as a resin having a different refractive index between the ridge 9 and the ferroelectric substrate 4.

  Next, a silicon oxide film is formed as a protective film 6 by sputtering on the surface of the ferroelectric substrate 4 on which the optical waveguide 3 is formed, and a silicon substrate 7 having a thickness of about 150 μm is attached to the surface with an epoxy adhesive 14. To match. The series of steps up to this point is performed by batch molding using a wafer substrate (not shown in particular). After the silicon substrate 7 is bonded, it is divided into individual pieces by dicing. The SHG element 1 is created by mirror-polishing the incident / exit surface of each element.

  Further, by providing the silicon substrate 7 on the protective film 6 provided on the optical waveguide 3 in the configuration of the SHG element 1, the productivity of the SHG element 1 can be improved as compared with the conventional manufacturing method. . That is, by further providing a silicon substrate 7 on the protective film 6 provided on the optical waveguide 3, the edge portions of the ridges 9 and the end surfaces of the trenches 8 forming the optical waveguide 3 are compared to the conventional structure. Therefore, the influence of the processing stress applied during dicing when dividing the individual pieces is reduced, and yield deterioration due to cracks and chips in the manufacturing process can be suppressed.

  In addition, cracking and chipping suppression can be reduced during mirror polishing as well as during dicing, and the entire incident / exit surface of the SHG element 1 is polished as the same polished surface, so that a wafer-like substrate formed up to the silicon substrate 7 is also obtained. The effect on the end face accuracy of the optical waveguide 3 due to the phenomenon that the polishing amount of the outer peripheral portion becomes larger than the central portion of the polished surface, that is, the so-called sagging phenomenon, can be reduced.

  When the silicon substrate 7 is bonded onto the protective film 6, if the substrates are simply bonded to each other, the thickness of the SHG element 1 is increased by the thickness of the silicon substrate 7, but the silicon substrate 7 is enlarged. By polishing the support substrate 5 and adjusting the thickness after bonding, it is possible to prevent an increase in size of the product. This is because the support substrate 5 reinforces the substrate strength of the thin ferroelectric substrate 4 forming the optical waveguide 3, and when the silicon substrate 7 is provided on the protective film 6, the silicon substrate 7 is also a substrate. Since the strength is reinforced, the thickness of the support substrate 5 can be reduced by an amount corresponding to the reinforcement strength obtained by the silicon substrate 7, so that an increase in size of the product accompanying the bonding of the silicon substrate 7 can be suppressed.

  In addition, such an SHG element 1 is mounted on a metal base 2 provided with a laser oscillation element serving as a light source by using an adhesive, and an optical axis of the laser oscillation element and an optical waveguide in the SHG element 1 In this mounting process, it is necessary to match not only the in-plane direction of the mounting surface but also the height direction with respect to the mounting surface with high accuracy.

  In the case of the configuration of the conventional SHG element 1, the protective film 6 serving as a mounting surface is a thin and hard film made of silicon oxide, and a trench that forms the metal base 2 and the optical waveguide 3 with the protective film 6 interposed therebetween. 8 and the edge of the ridge 9 are close to each other. Therefore, when the SHG element 1 is mounted on the metal base 2 in such a configuration, it can be pressed against the metal base 2 with a very large force in consideration of the strength of the protective film 6. Therefore, the layer thickness due to the adhesive is increased, and the influence of the curing shrinkage of the adhesive is greatly increased, and it is difficult to increase the positioning accuracy of the SHG element 1 with respect to the laser light source.

  However, if the structure of the SHG element 1 shown in FIG. 1 is used, since the silicon substrate 7 is further interposed between the protective film 6 and the metal base 2, the silicon substrate 7 acts as a protective layer for the optical waveguide 3 during mounting. Therefore, the SHG element 1 can be sufficiently pressed against the metal base 2, and as a result, the adhesive layer interposed between the SHG element 1 and the metal base 2 becomes thin, thereby suppressing the influence of curing shrinkage of the adhesive. Is possible.

  Further, in recent years, the power of the laser light source incident on the SHG element 1 has increased, and countermeasures against heat in the SHG element 1 have become an important study subject, and as described above, on the protective film 6 of the SHG element 1. The thickness of the adhesive 15 interposed between the SHG element 1 and the metal base 2 can be reduced by providing the silicon substrate 7 on the surface, that is, the adhesive 15 formed of a resin material having poor thermal conductivity in the heat transfer path. In addition, the heat conductivity of the silicon substrate 7 itself is much higher than that of the adhesive 15 and the protective film 6, so that the heat dissipation of the SHG element 1 is enhanced.

  The SHG element and the manufacturing method according to the present invention can increase the productivity of the SHG element, and are useful mainly for short wavelength laser oscillation module applications used in optical pickup devices and the like.

Sectional drawing which shows the state which mounted the SHG element of one Embodiment of this invention on the metal base Schematic showing the manufacturing method of the SHG element

Explanation of symbols

1 SHG element 3 Optical waveguide 4 Ferroelectric substrate (ferroelectric wafer)
5 Support substrate 6 Protective film 7 Silicon substrate 8 Trench 10 Polarization inversion region

Claims (2)

A step of forming a domain-inverted region on a ferroelectric wafer, a step of bonding a support substrate to the ferroelectric wafer, and a surface of the ferroelectric substrate opposite to the surface on which the support substrate is bonded Forming a trench on the surface of the polished dielectric substrate to form an optical waveguide, forming a protective film on the surface of the ferroelectric wafer on which the optical waveguide is formed, A process for producing an SHG element comprising: a step of bonding a silicon substrate to a surface of a ferroelectric wafer on which a protective film is formed; and a step of dividing the ferroelectric wafer bonded with the silicon substrate into pieces. Method. A ferroelectric substrate having a domain-inverted region, an optical waveguide formed on the main surface of the ferroelectric substrate, a protective film provided on the main surface of the ferroelectric substrate, and a back surface of the ferroelectric substrate A silicon substrate is bonded to the main surface of the protective film, and the input / output surfaces of the optical waveguide formed by the end surfaces of the ferroelectric substrate, the protective film, and the silicon substrate are the same. A SHG element having a polished surface.

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