JPH09213676A - Etching - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate an etching residues and to perform evenly an etching by a method wherein a sample to be etched having a silicon film is electrically insulated from a jig for protecting the sample leaving a region to be etched. SOLUTION: An insulating material 21 is held between a liquid crystal cell 17 and a lower cap 12 and an electrical insulation between both of the cell 17 and the cap 12 is ensured. The size and shape of a jig 11 are also specially limited, but various noble metals, such as SUS, gold, silver, copper and platinum, their alloys, a resin fluorine, such as a Teflon, and the like are used as the material for the jig 11. As the material 21, any material, which exhibits insulating properties, can be arbitrariry used and the Teflon and a vinyl can be used in addition to a polyimide tape of a thickness of 34μm, for example. Thereby, an etching process can be made to progress evenly.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to anisotropic etching of silicon, and more particularly to a sample to be etched containing the silicon and a jig for protecting the sample.

[0002]

2. Description of the Related Art Conventionally, anisotropic etching of silicon has been performed in the manufacturing process of X-ray masks, pressure sensors, various micromachines, liquid crystal display devices and the like. Since the etching is usually performed only on a specific region of the sample to be etched, the sample to be etched is protected from the etching solution by various etching masks and jigs while leaving the region.

A conventional etching method will be described with reference to a case where a liquid crystal cell is used as a sample to be etched. FIG. 4 is a sectional view showing a conventional etching process. 11 in the figure
Is a jig for protecting the sample to be etched and includes a lower lid 12 and an upper lid 13. Reference numeral 14 is an O-ring, 15 is a silicone rubber, 16 is a Teflon sheet, 17 is a liquid crystal cell, and a glass substrate 18 and a single crystal silicon substrate 19 are bonded together, and a liquid crystal 20 is sandwiched therebetween. 22 is an etching mask, 23 is an etching solution, and 24 is an etching tank.

As the etching solution 23, the liquid crystal cell 17 is fixed to the jig 11 and dipped in an approximately 20% aqueous solution of TMAH (tetramethylammonium hydroxide) heated to approximately 80 ° C. Conductive etching is performed to make the substrate transparent. A thermal oxide film having a thickness of, for example, about 1 μm is formed as an etching mask 22 around the area to be etched so that the area other than a predetermined area is not etched.

The liquid crystal cell 17 is housed in the lower lid 12 of the jig 11 via a Teflon sheet 16 and is in contact with the upper lid 13 via a silicone rubber 15. Lower lid 1 of jig 11
The upper lid 13 and the upper lid 13 are fixed to each other via an O-ring 14 with a frame (not shown) so that the etching solution 23 does not enter the jig. Therefore, the part where the etching solution 23 is dipped is only inside the opening of the upper lid 13 surrounded by the silicone rubber 15. The upper lid 13 has a slope formed in its opening in order to allow gas generated by etching to escape (drain) from the etching surface. Usually about 15
In time, the single crystal silicon substrate 19 having a thickness of 625 μm is hollowed out and made transparent, leaving a thin film such as an oxide film formed on the inner surface of the substrate.

[0006]

However, in the conventional etching method, about 10% of the phenomenon that the etching does not proceed at all (hereinafter referred to as "removal") is a problem in the process.

Further, since the liquid crystal cell is flat with a 2 cm square and a thickness of about 2 mm, the jig has a size of 5 cm square and a thickness of about 1 cm. Therefore, when placed flat, the number of pieces that can enter the etching tank is small, and when multiple layers are stacked to etch a large amount, the circulation of the etching solution and the gas escape are deteriorated, the etching progresses unevenly, and the etching residue or local Over etching is likely to occur. Further, when the jig was placed vertically, the gas escaped from the opening of the upper lid was deteriorated, and the progress of etching was slowed particularly in the upper portion where the gas was attached, resulting in the etching residue. Therefore, some measure has to be taken for the installation method in the etching tank.

The present invention is an etching method which solves the above-mentioned problems, and more specifically, a method which allows uniform etching without any etching residue including "missing" of etching.

[0009]

The present invention is a method of anisotropically etching silicon using an alkaline etching solution, which comprises: a sample to be etched having the above silicon; and a sample to be etched leaving a region to be etched. It is an etching method characterized in that it is electrically insulated from a jig for protecting it.

The present inventors have found that
The present invention has been accomplished by discovering that the liquid crystal cell, which is the sample to be etched, is electrically connected to the jig. That is, the present inventors compared the etching situation between the case where the liquid crystal cell and the jig are short-circuited with a conductive rubber containing carbon, and the case where insulation is performed using a polyimide insulating tape. While "out of" occurred in 49 cells out of 52, the latter did not occur at all out of 26 cells.

Further, in the etching method of the present invention, when the jig is immersed in the etching solution, if the angle of the etching surface with respect to the water surface is up to 60 °, the etching is uniform even if the jig is obliquely arranged. It was confirmed to proceed.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment of the present invention. FIG. 1 is a cross-sectional view of the liquid crystal cell fixed to a jig, and the same parts as those in FIG. In FIG. 1, 21 is an insulating material.

In the present invention, the liquid crystal cell 17 and the lower lid 12
An insulating material 21 is sandwiched between and to ensure electrical insulation between them. Further, the jig 11 is heated in advance in an oven or the like, and the attached water is removed by cleaning.

In the present invention, the sample to be etched is not limited to the liquid crystal cell, but the present invention can be preferably applied to the manufacturing process of the above-mentioned X-ray mask, pressure sensor and various micromachines. Further, the size and shape of the jig 11 are not particularly limited, but as the material, various noble metals such as SUS, gold, silver, copper, platinum and their alloys, and fluororesins such as Teflon are used. Of these, metals, particularly SUS, are preferably used.

In the present invention, any material can be used as the insulating material 21 as long as it has an insulating property. For example, Teflon or vinyl can be used in addition to a polyimide tape having a thickness of 30 μm. Alternatively, FIG.
As shown in, by forming the coating layer 26 made of an insulating material on the inner surface of the lower lid 12, the Teflon sheet 16 can also be formed. As the coating material, a fluorine-based resin such as Teflon, an organic substance, a ceramic or the like is preferably used, and depending on the material of the jig, the jig can be directly fluorinated, oxidized or nitrided. Further, the coating may be not only the inner surface of the lower lid but also the entire surface.

The etching solution is an alkaline aqueous solution usually used for anisotropic etching of single crystal silicon, such as an aqueous solution of TMAH, an aqueous solution of sodium hydroxide,
Aqueous potassium hydroxide solution, ethylenediamine / pyrocatechol / water mixed solution (EPW) and the like are preferably used.

In the present invention, the jig 11 storing the sample to be etched has an angle θ of 60 with respect to the water surface 25 of the etching solution 23 as shown in FIG.
It is tilted so as to have an angle of 0 ° and placed in the etching bath 24. The distance d between adjacent jigs is 5 mm (length 5 cm, width 24 cm, height 1 cm) so that the jigs do not overlap when viewed from above.
If it is a continuous jig, it may be set to about 3.5 cm), and if a means for stirring the etching solution is provided, it can be further narrowed. The angle θ between the etching surface and the water surface may be 0 ° when the number to be processed is small, that is, the plate may be placed flat, and when the number is large, the angle θ may be tilted up to 60 ° to give 5 cm / cm. Even in the case of individual pieces, the occupied area can be reduced to 3.5 cm / piece, which is about 1 / 1.4, and the number of processed pieces can be increased. In addition, a small etching bath can be used even when the same number is processed.

[0018]

As described above in detail, according to the present invention, the etching process does not occur at all and the etching process proceeds uniformly. Therefore, the yield in the etching process is improved as compared with the conventional method, and since many samples can be etched at the same time, the cost required for etching is reduced and a highly reliable product can be provided at low cost. You can

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is a diagram showing an arrangement example of jigs according to the present invention.

FIG. 3 is a sectional view showing a different embodiment of the present invention.

FIG. 4 is a cross-sectional view for explaining a conventional etching method.

[Explanation of symbols]

 11 jig 12 lower lid 13 upper lid 14 O-ring 15 silicon rubber 16 Teflon sheet 17 liquid crystal cell 18 glass substrate 19 silicon substrate 20 liquid crystal 21 insulating material 22 etching mask 23 etching solution 24 etching bath 25 water surface 26 coating layer

Claims (11)

[Claims] 1. A method for anisotropically etching silicon using an alkaline etching solution, which comprises: a sample to be etched having the silicon; and a jig for protecting the sample while leaving a region to be etched. Is electrically insulated. 2. The etching method according to claim 1, wherein the etching solution is a tetramethylammonium hydroxide aqueous solution. 3. The etching method according to claim 1, wherein the silicon is single crystal silicon. 4. The etching method according to claim 1, wherein the sample to be etched is a liquid crystal cell. 5. The jig is made of a conductive material.
The etching method according to any one of to 4. 6. The etching method according to claim 5, wherein the jig is made of metal. 7. The etching method according to claim 6, wherein the jig is made of SUS. 8. The etching method according to claim 1, wherein the means for electrically insulating is to sandwich an insulating material between the sample to be etched and the jig. 9. The etching method according to claim 1, wherein the electrically insulating means is an insulating treatment on an inner surface of the jig in contact with the sample to be etched. 10. The etching method according to claim 9, wherein the insulating treatment is Teflon coating. 11. The method according to claim 1, wherein when the sample to be etched is fixed to the jig and immersed in the etching solution, the etching surface is set at an angle of 0 to 60 ° with respect to the surface of the etching solution. The etching method according to.