JP2009128829A - Manufacturing method for waveguide - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method for a waveguide with which loss and polarization dependency are reduced without making a manufacturing process complicated. <P>SOLUTION: The manufacturing method includes: an underclad layer formation step in which an underclad layer is formed; a side-clad layer formation step in which a side-clad layer is formed on the underclad layer; a side-clad layer formation step in which the side-clad layer is etched to form a first side clad and a second side clad; a resist arrangement step in which a resist is arranged on the first and second side-clads; a core formation step in which a core film is deposited between the first side clad and the second side clad, thereby forming a core; a lift-off step in which the resist is removed by lift-off; and an over-clad formation step in which an over-clad layer is formed on the first side clad and the second side clad and the core. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a waveguide, and more particularly, to a method for manufacturing a waveguide of a quartz-based planar lightwave circuit (PLC) device.

  PLC devices play a central role in optical communication systems and optical / electronic circuits. In a conventional PLC device waveguide, development of a high-performance waveguide using semiconductor manufacturing technology such as LSI technology has been advanced, and a manufacturing method thereof has already been established.

  The production method of the quartz optical waveguide is roughly classified into a flame deposition (FHD) method, a low pressure chemical vapor deposition (LP-CVD) method, an atmospheric pressure chemical vapor deposition (AP-CVD) method, a plasma chemical vapor deposition ( (P-CVD) method, etc., each of which has a characteristic deposition technique (see non-patent literature).

M. Kawachi, “Silica waveguides on silicon and their application to integrated-optic components,” Opt. Quantum Electron., Vol. 22, pp. 391-416, 1990

  However, in any of the conventional methods for producing a silica-based optical waveguide, the deposited core film is processed, and an overclad (OC) is deposited thereon, which causes problems that occur. is there. The core that guides the signal light is formed by dry etching the core film. However, the dry etching causes the side surface roughness of the core, and this side surface roughness directly affects the signal light. This leads to loss (processing loss). In addition, an over clad is deposited to limit signal light guided through the core. However, when the core is embedded with the over clad, the core is deformed, and non-uniform stress is generated on the side surface of the core and the core surface. Such non-uniform stress distribution causes polarization dependence. As an example, in an arrayed waveguide grating (AWG), there is a center wavelength difference (PDλ) between TE light and TM light. Technical devices for reducing PDλ, such as UV light irradiation, heat treatment, and post-optical circuit manufacturing processes such as wave plate insertion, have been developed. However, the process becomes complicated and the manufacturing process becomes heavy. Yes.

  The present invention has been made in view of such problems, and an object of the present invention is to reduce processing loss and polarization dependence without complicating the manufacturing process in a method for manufacturing a waveguide of a PLC device. Another object of the present invention is to provide a method for manufacturing a waveguide.

  In order to achieve such an object, according to a first aspect of the present invention, in the waveguide manufacturing method, an under-cladding layer forming step for forming an under-cladding layer, and a side cladding layer is formed on the under-cladding layer. A side cladding layer forming step, a side cladding forming step of etching the side cladding layer to form a first side cladding and a second side cladding, and on the first side cladding and the second side cladding. In addition, a resist disposing step for disposing a resist, a core forming step for forming a core by depositing a core film between the first side cladding and the second side cladding, and removing the resist by lift-off. A lift-off step, and the first side cladding and the second side cladding Head and on said core, characterized in that it comprises and an over-cladding layer formation step of forming an overcladding layer.

  According to a second aspect of the present invention, in the first aspect, the step of forming the side cladding includes a step of applying a first resist to the entire surface of the side cladding layer, and introducing the first resist by photolithography. The method includes patterning into a waveguide pattern to form a resist pattern, and etching the side cladding layer using the resist pattern as a mask.

  According to a third aspect of the present invention, in the second aspect, the resist placement step includes the step of removing the first resist, the first and second side claddings, and the first and second steps. Applying a second resist between the second side clads, and patterning the second resist into a waveguide pattern by photolithography, so that the second resist is applied only on the first and second side clads. Leaving the resist.

  According to the present invention, since the core for guiding the signal light is formed by providing the side clad in advance and depositing the core film between the side clads, the conventional dry etching of the core film is unnecessary. It is. In addition, batch deposition in which the side surfaces and the surface of the core are collectively filled with the over clad layer is not necessary. Therefore, it is possible to provide a method of manufacturing a waveguide that prevents the side surface roughness of the core and nonuniform stress distribution, and reduces loss and polarization dependence without complicating the manufacturing process.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. 1 to 7 show the steps of the waveguide manufacturing method according to the present invention. In each of the following steps, heat treatment for stabilizing the film quality is appropriately performed.

  First, in a first step, an under cladding layer 102 is formed on a Si substrate 101 (see FIG. 1). For forming the under-cladding layer 102, an FHD method or the like can be used.

  Subsequently, a side cladding layer 103 is deposited in a second step (see FIG. 2). An LP-CVD method or the like can be used. The side cladding layer 103 may have a dopant such as P or B having a certain concentration composition in order to adjust the difference in refractive index between the core and the cladding.

  Next, in a third step, the side cladding layer 103 is etched to form the core region 103A (see FIG. 3). Specifically, a resist is applied to the entire surface of the side cladding layer 103, the resist is patterned into a waveguide pattern by photolithography, and the side cladding layer 103 is etched using the resist pattern as a mask. The side cladding layer 103 is divided into a core region 103A and a side cladding 103B. Then, the resist is removed. Etching of the side cladding layer 103 may be dry etching or wet etching.

  Subsequently, in a fourth step, a resist 104 is disposed on the side cladding 103B (see FIG. 4). Specifically, a resist can be applied to the core region 103A and the side cladding 103B, and the resist can be patterned into a waveguide pattern by photolithography, leaving the resist 104 only on the side cladding 103B. It is preferable to apply the resist again because of problems with etching selectivity and heat resistance, but by using a resist that can avoid this, the resist is used in the fourth step without removing the resist in the third step. You can also

  In the fifth step, a core film having the same thickness as the side cladding layer 103 is deposited on the resist 104 (see FIG. 5). Part of the core film is deposited on the resist 104 to become the core layer 105B, and part of the core film is deposited on the core region 103A to become the core 105A. The FHD method can be used for the deposition of the core film.

  Next, in the sixth step, the resist 104 and the core layer 105B are removed by lift-off (see FIG. 6). As a result, flat surfaces of the side cladding 103B and the core 105A appear.

  Finally, in the seventh step, an overcladding layer 106 is deposited (see FIG. 7). An LP-CVD method or the like can be used. Here, the over clad layer 106 has the same composition as the side clad layer 103.

  Since the present invention does not perform dry etching when forming the core, roughening of the side surface of the core is avoided. In addition, by forming the core by depositing the core film in the core region (or between the side claddings), the film becomes thinner as it approaches the side of the core based on the shadow effect (the effect of thinning the shadowed portion during deposition). It becomes obvious. As a result, a natural core deposition shape 105A that is not formed by etching, in which the perpendicularity of the core side surface is lost, becomes a structure in which non-uniform tension is not applied to the surface of the core 105A. Such a core serves as a buffer structure when depositing the over clad layer, and the over clad layer 106 having the same composition slowly penetrates into the gap between the core 105A and the side clad 103B generated due to the shadow effect. Therefore, the uneven stress distribution on the core side surface and the core surface and the polarization dependence can be reduced.

  As can be seen from the description of each step described above, such an effect realizes a significant process reduction as compared with the prior art. In addition, since the yield of the waveguide can be greatly improved by the simple method of the present invention as compared with the yield of the process performed after the conventional optical circuit manufacturing, as a result, the overall yield of the waveguide fabrication is greatly improved. As an example, in the deposition method in which only the stress distribution is slightly reduced without using the side cladding in the conventional method, the PDλ is 0.07 nm, which is significantly improved from 0.16 nm in the conventional method. Therefore, it can be said that reducing the non-uniform stress distribution is effective in improving PDλ, and thus the effectiveness of the present invention was shown.

It is a figure which shows the 1st step of the manufacturing method of the waveguide concerning the present invention. It is a figure which shows the 2nd step of the manufacturing method of the waveguide based on this invention. It is a figure which shows the 3rd step of the manufacturing method of the waveguide based on this invention. It is a figure which shows the 4th step of the manufacturing method of the waveguide based on this invention. It is a figure which shows the 5th step of the manufacturing method of the waveguide based on this invention. It is a figure which shows the 6th step of the manufacturing method of the waveguide based on this invention. It is a figure which shows the 7th step of the manufacturing method of the waveguide based on this invention.

Explanation of symbols

101 Si substrate 102 Under clad layer 103 Side clad layer 103A Core region 103B Side clad 104 Resist 105A Core 105B Core layer 106 Over clad layer

Claims (3)

In a method for manufacturing a waveguide,
An underclad layer forming step for forming an underclad layer;
A side cladding layer forming step of forming a side cladding layer on the under cladding layer;
A side cladding forming step of etching the side cladding layer to form a first side cladding and a second side cladding;
A resist placement step of placing a resist on the first side cladding and the second side cladding;
A core forming step of forming a core by depositing a core film between the first side clad and the second side clad;
A lift-off step of removing the resist by lift-off;
An over-cladding layer forming step of forming an over-cladding layer on the first side cladding, the second side cladding, and the core. The side cladding forming step includes
Applying a first resist to the entire surface of the side cladding layer;
Patterning the first resist into a waveguide pattern by photolithography to form a resist pattern;
The method according to claim 1, further comprising: etching the side clad layer using the resist pattern as a mask. The resist placement step includes
Removing the first resist;
Applying a second resist over the first and second side claddings and between the first and second side claddings;
3. The step of patterning the second resist into a waveguide pattern by photolithography to leave the second resist only on the first and second side claddings. Manufacturing method.

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