JP2004028820A - Measurement method of v-groove width - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for measuring width in a V groove that is provided on a silicon substrate, is used for mounting optical fibers, and forms a silicon dioxide film by a nondestructive method. <P>SOLUTION: In the method for measuring width in the V groove that is provided on the silicon substrate, is used for mounting the optical fibers, and forms the silicon dioxide film, the edge of the V groove on the surface of the silicon dioxide film is detected as a focus position, and the width in the V groove is measured. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for measuring a V-groove width, and more particularly to a method for providing a V-groove for mounting an optical fiber on a silicon substrate and measuring a V-groove width of a silicon dioxide film formed thereon.
[0002]
[Prior art]
2. Description of the Related Art With the spread of personal computers and the Internet in recent years, demand for information transmission has been rapidly increasing. For this reason, it is desired that optical transmission with a high transmission speed be spread to terminal information processing devices such as personal computers. To achieve this, it is necessary to manufacture high-performance optical waveguides and optical multiplexer / demultiplexers at low cost and in large quantities for optical interconnection.
[0003]
As a material of the optical waveguide, an inorganic material such as glass or a semiconductor material and a resin are known. When an optical waveguide is manufactured from an inorganic material, a method is used in which an inorganic material film is formed by a film forming apparatus such as a vacuum evaporation apparatus or a sputtering apparatus, and the inorganic material film is etched into a desired optical waveguide shape. . However, the vacuum evaporation apparatus and the sputtering apparatus require large-scale evacuation equipment, and are therefore large and expensive.
In addition, since the evacuation step is required, the step becomes complicated. On the other hand, when an optical waveguide is manufactured using a resin, the film formation process can be performed at atmospheric pressure by coating and heating, so that there is an advantage that the apparatus and the process are simple.
[0004]
Various resins are known as resins constituting the core layer and the cladding layer of the optical waveguide. Polyimides having a high glass transition temperature (Tg) and excellent heat resistance are particularly expected. When the core layer and the clad layer of the optical waveguide are formed of polyimide, long-term reliability can be expected, and it can withstand soldering.
For such a polymer optical waveguide, for example, a lower clad layer is formed on a substrate such as silicon, a core layer is formed on the lower clad layer, a resist layer is provided on the core layer, and a core shape is formed. It is manufactured by patterning to form a core, removing the resist layer, and then forming an upper clad layer on the lower clad layer and the core surface. In general, all of these layers are formed using a spin coating method. As described above, by forming the core and the clad layer with the resin, the resin optical waveguide can be manufactured by a simple manufacturing process.
[0005]
A resin optical waveguide is generally formed by providing a V-groove for mounting an optical fiber on a substrate, and further laminating a resin lower clad layer, an optical waveguide layer, and an upper clad layer. At this time, whether or not the positional deviation between the V-groove for mounting the optical fiber and the optical waveguide is within a predetermined range is important for accurately aligning the fiber mounted on the V-groove with the optical waveguide. is there.
The positional deviation includes a positional deviation (lateral deviation) in the main plane direction of the substrate and a positional deviation (vertical deviation) in a direction perpendicular to the main plane direction of the substrate. To measure the vertical deviation, the substrate is cut vertically to expose the cross section of the V groove, and the cross section is photographed with a CCD camera or the like, and the V groove width is measured. For example, as shown in FIG. 2, the edge of the slope A of the V-groove is detected, and the optical fiber center position C having a diameter R circumscribing the edge is calculated. Next, the position of the V-groove top surface is detected by detecting the edge of the portion B. The difference d between the optical fiber center position C and the V-groove top surface position, that is, the substrate surface, is calculated, and the value of d is compared with the distance between the center position of the core of the optical waveguide provided on the substrate and the substrate surface. If the difference is larger than a predetermined value, the difference is determined to be defective.
[0006]
However, in this method, the width of the V-groove is measured from the cross-sectional direction, and the displacement (vertical deviation) of the V-groove formed on the substrate in a wafer state cannot be measured without cutting out the V-groove cross-section. . Therefore, in addition to the problem that it is difficult to control the quality of each wafer, it is necessary to cut out a V-groove cross section formed on the substrate in a wafer state. Therefore, there is a demand for a non-destructive V-groove width measurement method that does not require cutting out the V-groove cross section.
[0007]
[Problems to be solved by the invention]
Accordingly, an object of the present invention is to provide a method of measuring a V-groove width by a non-destructive method, and more specifically, to provide a V-groove for mounting an optical fiber on a silicon substrate and forming a V-groove width on a silicon dioxide film. Is to provide a method for measuring
[0008]
[Means for Solving the Problems]
The present invention relates to a method for measuring the width of a V-groove of a silicon dioxide film formed by providing a V-groove for mounting an optical fiber on a silicon substrate. Is detected as a focus position, and the width of the V-groove is measured.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail with reference to FIG.
There are a laser reflection method and an image processing method for measuring the width of the V-groove 3 by autofocusing from the vertical direction of the substrate 1. Incidentally, a silicon dioxide film is usually formed on the entire upper surface of the wafer-like substrate 1 by a thermal oxidation method, a vapor deposition method, or the like. Since the silicon dioxide film 2 is almost colorless and transparent, the image processing method does not detect the surface of the silicon dioxide film 2 but detects the edges 4, 4 'of the surface of the silicon substrate 1 (blue) as the focus position. Would. Since the silicon dioxide film 2 has a thickness of 1 μm, the width (2x ′) of the V-groove 3 detected by the image processing method is about 1 μm wider than the actual width (2x), and the accurate V-groove width Cannot be measured, and an accurate distance d from the substrate to the center of the optical fiber cannot be obtained.
For this reason, in the present invention, the focus positions 5, 5 'are detected from the amount of laser reflection on the surface of the silicon dioxide film 2 using the laser reflection method, and the width of the V-groove 3 is measured. As a result, the V groove width 2x can be measured more accurately, so that an accurate distance d from the substrate surface to the optical fiber center position C can be obtained.
[0010]
The V groove 3 is a groove having a depth of about 100 μm formed by anisotropically etching the silicon single crystal substrate 1 and has a V-shaped cross section.
As shown in FIG. 1, the sectional shape of the V-groove 3 has a relationship of x: y = 1: √2, where the width of the V-groove 3 is 2x and the depth is y. This ratio is constant since the V-groove is formed by anisotropic etching. Assuming that the radius of the optical fiber is R and the distance from the bottom of the V-groove 3 to the center of the optical fiber is z, z = √3R from the relation of z: R = √3: 1. Further, since the depth y of the V-groove is y = √2x, the distance between the center position C of the fiber and the surface of the silicon dioxide coating 2, that is, the distance d from the substrate surface to the center position C of the optical fiber is zy. = √3R-√2x.
The type of laser is not particularly limited, and for example, a 780 nm laser can be used.
[0011]
【The invention's effect】
According to the method of the present invention, the width of the V-groove is accurately measured and the distance d from the substrate surface to the optical fiber center position C is calculated from the V-groove width. There is no need to cut out the cross section of the groove, and quality control can be easily performed in wafer units.
The measurement accuracy of the V-groove width measured by the method of the present invention is ± 0.1 μm, which is much better than ± 0.6 μm when a telecomparator is used, and the measurement time is about 0.5 seconds. Thus, the measurement can be performed in a shorter time as compared with 1 to 2 seconds in the case of the image processing method.
[Brief description of the drawings]
FIG. 1 is a drawing for explaining a method of measuring a V-groove width according to the present invention.
FIG. 2 is a drawing for explaining a conventional V groove width measuring method.
[Explanation of symbols]
1: silicon substrate, 2: silicon dioxide coating, 3: V groove, 4, 4 ': edge of V groove on silicon substrate, 5, 5': edge of V groove on silicon dioxide coating, C: optical fiber Center position, R: radius of optical fiber, d: distance from substrate surface to optical fiber center position C, 2x: width of V groove, y: depth of V groove

Claims (1)

In a method of providing a V-groove for mounting an optical fiber on a silicon substrate and measuring the width of the V-groove of a silicon dioxide film formed, the edge of the V-groove on the surface of the silicon dioxide film is focused by a laser reflection type autofocus. A method of detecting the position and measuring the width of the V-groove.

Images