JP2014115416A - Optical waveguide substrate and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical waveguide substrate in which a metal pad is selectively formed only in a desired portion, and a method for manufacturing the substrate.SOLUTION: The method for manufacturing an optical waveguide includes steps of: forming a substrate-side alignment mark 12 on a surface of a quartz substrate 11; forming a core 13 on the surface of the quartz substrate 11; forming a clad 14 that covers the core 13 on the surface of the quartz substrate 11; forming a photoresist 15 on a back surface of the quartz substrate 11; positioning a photomask 17 having a mask-side alignment mark 16 formed thereon on the back surface of the quartz substrate 11; forming a photoresist pattern 18 by photolithography on the back surface of the quartz substrate 11; and forming a metal pad 19 corresponding to the photoresist pattern 18 on the back surface of the quartz substrate 11.

Description

  The present invention relates to an optical waveguide substrate in which an optical waveguide is formed on the surface of a quartz substrate and a method for manufacturing the same.

  As shown in FIG. 5, since solder cannot be directly placed on the quartz substrate 51, an optical waveguide substrate 50 in which an optical waveguide composed of a core 52 and a clad 53 is formed on the surface of the quartz substrate 51 is printed. In addition, it is difficult to perform solder bonding on a silicon substrate.

  Therefore, a metal pad 54 for solder bonding is formed on the back surface of the quartz substrate 51, and the metal pad 54 and the printed circuit board or silicon substrate are soldered to each other, whereby the optical waveguide substrate 50 is placed on the printed circuit board or silicon substrate. Soldered.

JP 2001-242332 A

  However, conventionally, since the metal pad 54 is formed on the entire back surface of the quartz substrate 51, there is a possibility that the polarization dependent loss of the light propagating through the core 52 may increase due to the stress at the time of soldering. It was.

  Accordingly, an object of the present invention is to provide an optical waveguide substrate in which metal pads are selectively formed only at desired portions, and a method for manufacturing the same.

  The present invention devised to achieve this object includes a step of forming a substrate-side alignment mark on the surface of a quartz substrate, a step of forming a core on the surface of the quartz substrate, and the core on the surface of the quartz substrate. Forming a clad covering the substrate, forming a photoresist on the back surface of the quartz substrate, aligning a photomask having a mask-side alignment mark formed on the back surface of the quartz substrate, and An optical waveguide substrate manufacturing method comprising: forming a photoresist pattern on the back surface by photolithography, and forming a metal pad corresponding to the photoresist pattern on the back surface of the quartz substrate.

  The photoresist pattern may be formed so that the metal pad is not formed directly under the core.

  The substrate side alignment mark may be formed of amorphous silicon.

  The clad may be formed by flame deposition or plasma enhanced chemical vapor deposition.

  The metal pad may be formed of Ta / Pt / Au, Ti / Pt / Au, or Cu.

  The metal pad may be formed by vacuum deposition or sputtering.

  Moreover, this invention is an optical waveguide board manufactured with the manufacturing method of these optical waveguide boards.

  ADVANTAGE OF THE INVENTION According to this invention, the optical waveguide board | substrate which formed the metal pad selectively only in the desired part, and its manufacturing method can be provided.

(A)-(f) is a cross-sectional schematic diagram explaining the manufacturing method of the optical waveguide board | substrate which concerns on this invention. (A)-(e) is a cross-sectional schematic diagram explaining the manufacturing method of the optical waveguide board | substrate which concerns on this invention. It is the top view which looked at the surface patterning substrate from the back side. It is the top view which looked at the process of FIG.2 (b) from the back surface side of the quartz substrate. It is a cross-sectional schematic diagram which shows the optical waveguide board | substrate which concerns on a prior art.

  Preferred embodiments of the present invention will be described below with reference to the accompanying drawings.

  As shown in FIGS. 1 and 2, the method for manufacturing an optical waveguide substrate according to the present embodiment includes a step of forming a substrate-side alignment mark 12 on the surface of the quartz substrate 11, and a core 13 on the surface of the quartz substrate 11. A step of forming a clad 14 covering the core 13 on the surface of the quartz substrate 11, a step of forming a photoresist 15 on the back surface of the quartz substrate 11, and a mask-side alignment mark 16 ( 4), a step of aligning the photomask 17 on which the photomask 17 is formed, a step of forming a photoresist pattern 18 by photolithography on the back surface of the quartz substrate 11, and a photoresist pattern 18 on the back surface of the quartz substrate 11. And a step of forming the metal pad 19.

  First, steps related to a method for patterning the surface of the quartz substrate 11 will be described.

  In the step of forming the substrate-side alignment mark 12 on the surface of the quartz substrate 11, the substrate-side alignment mark 12 is formed at a predetermined position on the surface of the quartz substrate 11 (for example, two locations on the edge of the wafer) (FIG. 1A )reference).

  At this time, the substrate side alignment mark 12 is formed of amorphous silicon. Amorphous silicon is an amorphous semiconductor mainly composed of silicon, and has characteristics that it has a higher light absorption coefficient than that of crystalline silicon and can be easily and inexpensively formed into a film.

In the step of forming the core 13 on the surface of the quartz substrate 11, first, a core film 21 made of SiO ₂ —GeO ₂ or the like is formed so as to cover the surface of the quartz substrate 11 together with the substrate-side alignment mark 12 (FIG. 1). (See (b)).

  Thereafter, a core etching metal film 22 is formed on the surface of the core film 21, and a waveguide resist pattern 23 is formed on the surface of the core etching metal film 22 (see FIG. 1C).

  The core 13 can be formed by etching the core etching metal film 22 with the waveguide resist pattern 23 (see FIG. 1D) and further etching the core film 21 with the core etching metal film 22. (See FIG. 1 (e)).

  The core film 21 remaining on the surface of the substrate side alignment mark 12 does not become the core 13.

  In the step of forming the core 13 on the surface of the quartz substrate 11, for example, the thickness of the core 13 is set to 2 μm or more and 8 μm or less. Here, the thickness of the core 13 is the thickness from the surface of the quartz substrate 11 to the surface of the core 13.

  In the step of forming the clad 14 covering the core 13 on the surface of the quartz substrate 11, the clad 14 is formed until the core 13 is completely filled (see FIG. 1 (f)).

  At this time, the clad 14 is formed by a flame deposition method or a plasma chemical vapor deposition (CVD) method, and for example, the thickness of the clad 14 is set to 15 μm or more and 40 μm or less. Here, the thickness of the clad 14 is the thickness from the surface of the quartz substrate 11 to the surface of the clad 14.

  At this time, even if the flame deposition method is selected, the amorphous silicon used for the substrate side alignment mark 12 has high heat resistance that can withstand a high temperature process (about 1100 ° C.) of the flame deposition method. In the high temperature process, the substrate side alignment mark 12 is not burned out.

  When the flame deposition method is selected, the quartz is melted by a high temperature process, so that the surface of the clad 14 can be flattened without requiring any other treatment.

  On the other hand, when the plasma chemical vapor deposition method is selected, it is necessary to perform a process such as chemical mechanical polishing (CMP) in order to flatten the surface of the clad 14.

  Through the above steps, the surface patterning substrate 10 is obtained. When the front surface patterning substrate 10 is viewed from the back surface side, as shown in FIG. 3, the substrate side alignment mark 12 (in the figure, a cross shape as an example) can be seen through from the back surface side.

  Next, the process regarding the patterning method of the back surface of the quartz substrate 11 is demonstrated.

  In the step of forming the photoresist 15 on the back surface of the quartz substrate 11, the photoresist 15 is formed on the entire back surface of the quartz substrate 11 (see FIG. 2A).

  In the step of aligning the photomask 17 in which the mask-side alignment mark 16 is formed on the back surface of the quartz substrate 11, a photo is formed on the back surface side of the quartz substrate 11 so that the mask-side alignment mark 16 matches the substrate-side alignment mark 12. The mask 17 is aligned and disposed (see FIGS. 2B and 4).

  At this time, since the light absorption coefficient of the amorphous silicon used for the substrate side alignment mark 12 is higher than the light absorption coefficient of the quartz substrate 11, there is a light / dark difference between them, and the substrate side alignment mark 12 is clearly visible or This makes it possible to recognize the back surface of the quartz substrate 11 and the photomask 17 easily and accurately.

  Thus, accurate alignment of the photomask 17 becomes possible only by the substrate side alignment mark 12 and the mask side alignment mark 16, and the metal pad 19 can be selectively formed only at a desired portion in a later process. It becomes.

  A pattern 24 is formed on the photomask 17 at a position corresponding to the metal pad 19 to be formed in a later process.

  In the step of forming the photoresist pattern 18 on the back surface of the quartz substrate 11 by photolithography, light is applied to the photoresist 15 through the photomask 17 and the pattern 24 of the photomask 17 is transferred and baked onto the photoresist 15. Pattern development is performed to form a photoresist pattern 18 (see FIG. 2C).

  At this time, the photoresist pattern 18 is formed so that the metal pad 19 is not formed directly under the core 13. Thereby, the influence which the metal pad 19 has on the light which propagates the core 13 can be decreased, and it becomes possible to further reduce the polarization dependence loss.

  In the step of forming the metal pad 19 corresponding to the photoresist pattern 18 on the back surface of the quartz substrate 11, first, a metal film 25 is deposited on the entire back surface of the quartz substrate 11 on which the photoresist pattern 18 is formed (FIG. 2). (See (d)).

  At this time, in order to form the metal pad 19 corresponding to the photoresist pattern 18, the metal film 25 deposited on the quartz substrate 11 and the metal film 25 deposited on the photoresist pattern 18 are not connected. It is necessary to make the thickness of the film 25 thinner than the thickness of the photoresist pattern 18.

  Thereafter, the photoresist pattern 18 is removed (lifted off) to form a metal pad 19 corresponding to the photoresist pattern 18 (see FIG. 2E).

  In the step of forming the metal pad 19 corresponding to the photoresist pattern 18 on the back surface of the quartz substrate 11, the metal pad 19 is formed of any one of Ta / Pt / Au, Ti / Pt / Au, or Cu. 19 is formed by vacuum deposition or sputtering, for example, the thickness of the metal pad 19 is 0.1 μm or more and 0.5 μm or less, and the width of the metal pad 19 is 10 μm or more and 500 μm or less. Here, the thickness of the metal pad 19 is the thickness from the back surface of the quartz substrate 11 to the surface of the metal pad 19.

  Through the above steps, a back surface patterning substrate (hereinafter referred to as an optical waveguide substrate) 20 which is an optical waveguide substrate is obtained.

  According to the optical waveguide substrate manufacturing method described so far, the metal pad 19 corresponding to the photoresist pattern 18 is formed. Therefore, if the photoresist pattern 18 is changed, it is selectively applied only to a desired portion. The metal pad 19 can be formed.

  At this time, by forming the metal pad 19 as far as possible from the core 13, the influence on the light propagating through the core 13 can be reduced, and the polarization-dependent loss can be further reduced. .

  Therefore, in the optical waveguide substrate 20 manufactured by the method of manufacturing an optical waveguide substrate according to the present embodiment, the metal pads 19 are selectively formed only in a desired portion. The possibility that the polarization dependent loss of the light propagating through 13 will increase can be kept low, or can be eliminated altogether.

  The substrate-side alignment mark 12 can also be used for surface mounting (SMT) image recognition, and the effect that the surface mounting operation and the like becomes easier than the conventional one is also obtained.

DESCRIPTION OF SYMBOLS 10 Surface patterning substrate 11 Quartz substrate 12 Substrate side alignment mark 13 Core 14 Clad 15 Photoresist 16 Mask side alignment mark 17 Photomask 18 Photoresist pattern 19 Metal pad 20 Optical waveguide substrate (Back surface patterning substrate)
21 Core film 22 Core etching metal film 23 Waveguide resist pattern 24 Pattern 25 Metal film

Claims (7)

Forming a substrate-side alignment mark on the surface of the quartz substrate;
Forming a core on the surface of the quartz substrate;
Forming a clad covering the core on the surface of the quartz substrate;
Forming a photoresist on the back surface of the quartz substrate;
Aligning a photomask having a mask-side alignment mark formed on the back surface of the quartz substrate;
Forming a photoresist pattern by photolithography on the back surface of the quartz substrate;
Forming a metal pad corresponding to the photoresist pattern on the back surface of the quartz substrate;
A method for producing an optical waveguide substrate, comprising:   The method of manufacturing an optical waveguide substrate according to claim 1, wherein the photoresist pattern is formed so that the metal pad is not formed immediately below the core.   The method for manufacturing an optical waveguide substrate according to claim 1, wherein the substrate side alignment mark is formed of amorphous silicon.   The method for manufacturing an optical waveguide substrate according to claim 1, wherein the clad is formed by a flame deposition method or a plasma chemical vapor deposition method.   The method for manufacturing an optical waveguide substrate according to claim 1, wherein the metal pad is formed of any one of Ta / Pt / Au, Ti / Pt / Au, or Cu.   The method for manufacturing an optical waveguide substrate according to claim 1, wherein the metal pad is formed by a vacuum deposition method or a sputtering method.   An optical waveguide substrate manufactured by the method for manufacturing an optical waveguide substrate according to claim 1.