JP2006159313A - Grinding method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a grinding method for realizing simple, inexpensive, and highly accurate groove machining or the like of an optical element by executing the groove machining or the like of an optical element by using a conventional grinding device with conventional grinding work. <P>SOLUTION: A different material 2, which is ground with an abrasive 8 at a grinding speed slower than the speed of a workpiece 1, is vapor-deposited on a machining face of the workpiece 1 with a photo-lithography technique. The workpiece 1 is pasted on a grinding plate 4 with an adhesive or the like when executing the grinding. An exclusive jig is mounted on a naval 5 part of the grinding plate 4. The grinding is executed while relatively reciprocating the grinding plate 4 to a grinding surface plate 7, to which a grinding cloth 6 is pasted, and allowing the abrasive 8 to flow. The workpiece 1 is removed by the grinding when the grinding is finished. The different material 2 remains. Eventually, the different material 2 is also removed. Consequently, an objective groove machining shape can be formed. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention performs polishing for groove processing on a workpiece of an optical element. For example, the present invention specifically relates to a polishing method for forming an optical waveguide.

  Usually, when grooves such as optical waveguides are formed on optical elements, dry machining such as precision machining using diamond tools, laser processing using excimer laser, or anisotropic ion etching (RIE) is performed. Utilized processing or the like is used (for example, see Patent Document 1, Patent Document 2, Patent Document 3, and Patent Document 4).

Among them, in machining used for the ridge type optical waveguide forming means, a diamond tool is used, and this tool is moved or an optical element is moved to process a target groove shape. In the dicing process, the groove shape is processed by moving the optical element with a rotary blade coated with diamond. Laser processing uses an excimer laser or the like, uses laser ablation, and processes the groove shape by moving the optical element or the laser position. In the etching process, a pattern is transferred onto an optical element using a photolithographic technique with a mask, and a groove shape process is performed by dry etching using plasma or ions.
Japanese Patent No. 2550606 JP 2003-119044 A JP 2004-109915 A JP 2004-219494 A

However, the groove processing of an optical element is a processing that requires accuracy on the order of μm in both width and depth. For this reason, the operation of the processing tool in the apparatus for performing the groove processing needs to be controlled with an accuracy of the order of μm or more, and sufficient stability is required. The etching process is slightly different from other processing methods, and because it uses semiconductor technology, very fine processing is possible. However, etching on the order of μm takes a very long time, and ions or plasma is applied to the optical element. May cause damage. In addition, dicing processing, laser processing, and the like all require very expensive machines.
Therefore, in view of the above circumstances, the present invention uses a conventional polishing apparatus for groove processing of an optical element and the like, and makes it possible to perform simple and inexpensive groove processing with high accuracy by using a conventional polishing operation. Is to provide.

The polishing method provided by the present invention provides the following polishing method in order to solve the above problems.
That is, a process of patterning different materials having a polishing rate slower than that of the workpiece on the processed surface of the workpiece into a target processing shape, and applying an abrasive to the patterned processed surface of the workpiece The process consists of a process of polishing while supplying, and a polishing process of a desired processing shape is performed on the polishing surface of the work piece by causing a difference in polishing speed between the work piece and the patterned material. Is.
The difference in the polishing rate by the abrasive is determined by the workpiece (optical element) and the abrasive, the material to be patterned and the ease of polishing by the abrasive, and more specifically each of the workpiece and the material to be patterned. Due to the difference in hardness.

Patterning can be easily performed by using a photolithography technique. As a material for patterning, an optimum material may be selected depending on a workpiece and an abrasive, and physical vapor deposition (PVD) or chemical vapor deposition (CVD) can be used.
Furthermore, the polishing method provided by the present invention causes a difference in the polishing rate due to a chemical reaction by a solution of an abrasive, and the polishing rate of a workpiece is higher than that of a material patterned into a target processing shape. A solution that produces a chemical effect early is used.
Examples of the chemical effect include an etching effect of an abrasive called mechanical chemical polishing, and an effect of generating an oxide film or hydrate on a workpiece surface called chemomechanical polishing. Which chemical effect to use is selected depending on the type of workpiece or abrasive (abrasive grain).

  The polishing method provided by the present invention is as described above in detail, and does not require an expensive apparatus, can use a conventionally used polishing apparatus, and can easily and inexpensively process a workpiece. A desired processing shape, that is, a groove-shaped polishing process can be performed on the surface.

The present invention uses two physical characteristics that each material has hardness, and that the hardness varies depending on the material, and causes a polishing rate difference due to the difference in hardness during the polishing. Thus, it is possible to generate a difference in the polishing amount between the materials and finally obtain a desired processed shape.
The target processed shape, for example, the groove shape, is patterned on the processed surface of the workpiece by using a photolithography technique to pattern a different material (a material having a lower polishing rate with an abrasive than the workpiece) into the target shape. However, it is desirable to use physical vapor deposition or chemical vapor deposition for this patterning. The material to be patterned may be selected depending on the characteristics (hardness) of the material of the workpiece, and examples thereof include SiO ₂ , Ti, Cr, a nitride film, and a carbide film. Here, in order to obtain the target groove shape, when patterning the target processing shape on the processing surface of the workpiece, the final groove shape and the patterning shape do not necessarily have to coincide with each other. What is necessary is just to determine patterning shape so that the target groove shape may be made.

It is desirable that the abrasive has a higher hardness than both materials. For example, diamond abrasive grains are desirable. The particle size may be selected depending on the pattern shape and the desired groove shape, and stepwise polishing due to the difference in particle size is also possible.
The polishing cloth may be either a non-woven cloth type or a suede type, but a suede type is more desirable when polishing the groove shape.
In addition, when a solution having a chemical effect is used as an abrasive, not only a physical hardness difference but also a chemical effect is added, and the workpiece can be polished more selectively. For obtaining a chemical effect, depending on the material of the workpiece, for example, lithium niobate (LiNbO ₃ ), the polishing process utilizing the chemical effect is ensured by making the polishing liquid alkaline.

Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.
First, as shown in FIG. 1, a different material (hereinafter simply referred to as a different material) 2 having a lower polishing rate than the workpiece 1 is deposited on the processed surface of the workpiece 1 by a photolithography technique. Patterning the desired processing shape (groove shape).
In this processing operation, first, a resist is applied to the processed surface of the workpiece 1. Then, a mask (not shown) having a groove-shaped slit is placed on the resist-coated surface, and light is irradiated through the mask to burn and develop the resist-coated surface. As a result of this baking and development, irregularities in the processed shape are formed. The concave portion is the upper surface of the workpiece 1, and the convex portion is a resist coated on the upper surface of the workpiece 1. A material which is the different material 2, for example, a silicon dioxide material is deposited on the uneven surface thus formed. Then, a silicon dioxide material is formed on the upper surfaces of the concave portions and the convex portions.

  Next, the film-formed workpiece 1 is entirely immersed in a solvent (not shown) to remove the resist. Then, the film of the silicon dioxide material is removed from the convex portion together with the resist, and as a result, only the film of the silicon dioxide material deposited on the upper surface of the workpiece 1 remains. In this way, the patterning operation using the different material 2 is completed. The result of this patterning is shown in FIG. 2, which shows an enlarged view of the portion 3 in FIG. 1, and shows a state in which the pattern shape of the different material 2 is raised in a convex shape on the processed surface of the workpiece 1. Yes. In FIG. 2, the width of the different material 2 is indicated by a, the distance between the different material 2 and the different material 2 is indicated by b, and the height of the different material 2 is indicated by c.

Next, the polishing process is performed. In this polishing process, for example, a polishing apparatus shown in FIG. 3 is used. In this figure, the patterned foreign material 2 shown in FIG. 2 is not shown greatly.
Hereinafter, specific processing methods, conditions, materials, and the like by the polishing apparatus shown in FIG. 3 will be described. The workpiece 1 is affixed to the polishing dish 4 with wax, an adhesive, or the like, and on the other hand, a dedicated jig, for example, a kanzashi (not shown) is attached to the portion of the tread 5 attached to the polishing dish 4. The dedicated jig has a constant weight, and the polishing dish 4 presses the workpiece 1 against the polishing cloth 6 attached to the upper surface of the polishing surface plate 7 with a constant load. It has become. The cloth of the polishing cloth 6 uses polyurethane or the like.

In polishing, the polishing agent 8 is supplied between the polishing cloth 6 and the polishing surface plate 7, specifically, while flowing. Depending on the material of the workpiece 1, diamond water mixed with diamond particles is employed.
The polishing process proceeds by reciprocating the polishing plate 4 relative to the polishing surface plate 7. In this way, when the target processing shape is a groove, the process until the groove processing can be performed is shown in FIGS. 4 to 7. 4 to 7 show the processing surface in an enlarged manner as in FIG.

FIG. 4 shows a state before polishing attached to the polishing dish 4. FIG. 5 shows the initial state of polishing. The corners of the different material 2 begin to be removed by polishing, and the workpiece 1 in a portion without the different material 2 is slightly polished (groove depth: d1).
FIG. 6 shows a state close to the end of the polishing process. Most of the different material 2 is polished, and accordingly, the portion without the different material 2 is also greatly polished (groove depth: d2).
FIG. 7 shows a state at the end of the polishing process. The workpiece 1 is removed by polishing, and the groove 1M is formed with the foreign material 2 removed. The width of the groove 1M is indicated by e, the groove interval is indicated by f, and the groove depth is indicated by d3. The following relationship is established between d1, d2 and d3.
d1 <d2 <d3

The final groove width e, groove interval f, and groove depth d3 vary depending on the abrasive, polishing time, and polishing cloth, but under the same conditions, the width a, interval b, and height of the dissimilar material 2 at the initial stage are almost the same. determined by the value of c. Therefore, it is necessary to determine the width a, the interval b, and the height c value according to the intended processing shape. In this way, the target groove (shape) polishing process is completed.
Examples of the material of the workpiece 1 shown in this embodiment include lithium niobate (LiNbO ₃ ), lithium tantalate (LiTaO ₃ ), silicon (Si), glass, and the like. (Ti, Cr, etc.), nitride films (TiN, etc.), carbide films (TiC, etc.), and the like.

Next, a second embodiment of the present invention will be described.
The configuration and operation of the polishing apparatus in the second embodiment are exactly the same as those in the first embodiment, and a material having a chemical effect on the workpiece 1 is used as the abrasive. Specifically, the polishing agent uses alkaline water in which alkaline water having a PH value of 9 to 11 and colloidal silica granules are mixed at a weight ratio of 60%: 40%. The particle size is on the nano order. In addition to polishing due to a physical hardness difference, the workpiece is selectively polished by a chemical effect, and groove processing can be performed more efficiently.

The material of the chemical effect, that is, the solution differs depending on the material of the workpiece 1. For example, when the material of the workpiece 1 is the above-described lithium niobate (LiNbO ₃ ), lithium tantalate (LiTaO ₃ ), or the like, polishing is performed. As the agent, an alkaline aqueous solution is beneficial as in the previous example.

The features of the present invention are as described in detail above, but the present invention is not limited to the above and illustrated examples, and includes various modifications. First, regarding the workpiece, the optical element, particularly the optical waveguide, has been described as the processing object and product, but it can also be applied to processing for other processing purposes. The material is not limited to lithium niobate (LiNbO ₃ ) or lithium tantalate (LiTaO ₃ ). The processing can be applied not only to groove processing but also to pattern processing. The solution utilizing the chemical effect is not limited to the alkaline aqueous solution. The polishing apparatus is not limited to the example shown in the figure, and it is possible to use a method of supplying an abrasive while applying a constant pressure instead of supplying the abrasive. The present invention includes all these modified embodiments.

It is a figure which shows the to-be-processed object which patterned different materials with the slow polishing speed by an abrasive | polishing agent. It is a figure which expands and shows the part of a to-be-processed object. It is a figure which shows the structure of a grinding | polishing processing apparatus. It is a figure which shows before the groove process in grinding | polishing. It is a figure which shows the state of the process initial stage in a to-be-processed. It is a figure which shows the state near completion | finish of grinding | polishing process. It is a figure which shows the state at the time of completion | finish of grinding | polishing process.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Workpiece 1M Groove 2 Dissimilar material 3 Portion 4 Polishing dish 5 Navel 6 Polishing cloth 7 Polishing surface plate 8 Polishing agent a Width b Interval c Height d1, d2, d3 Groove depth e Groove width f Groove interval

Claims (4)

  A process of patterning different materials having a polishing rate slower than that of the workpiece on the processed surface of the workpiece into a target processing shape, and supplying an abrasive to the patterned processed surface of the workpiece The polishing process of the desired shape of processing on the polishing surface of the workpiece by causing a difference in the polishing rate between the workpiece and the patterned material. A characteristic polishing method.   2. The polishing method according to claim 1, wherein the abrasive solution is a solution that exerts a chemical effect such that the workpiece is subjected to a chemical reaction and is quickly polished as compared with a patterned material.   The polishing method according to claim 1 or 2, wherein the workpiece is an optical element.   4. The polishing method according to claim 3, wherein the workpiece is an optical waveguide.

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