JPH01231330A - Formation of thin-film pattern and manufacture of pyroelectric thin-film - Google Patents

Abstract

PURPOSE:To form a pattern of a thin-film material, which cannot be formed through a conventional etching method and a lift-off method, by a method wherein a substrate is etched to form a projecting section having an overhang shape, a thin-film forming the pattern is provided onto the substrate, the projection section is etched and removed, and only the thin-film on an opening section in the substrate is left. CONSTITUTION:The pattern of a photo-resist 11 is formed onto a substrate 10 composed of MgO, etc. When the MgO substrate 10 is etched by using concentrated phosphoric acid, an opening section 12 in MgO left without being etched is formed to a reverse tapered shape. A thin-film 13 having a composition represented by Pb0.9La0.1Ti0.975O3 is shaped onto the MgO substrate 10 by employing an RF magnetron sputtering method. When the substrate is etched by using concentrated phosphoric acid, phosphoric acid permeates from the section of a cut 14 in the PLT thin-film 13 formed in a reverse tapered section in the MgO substrate 10, a projecting section 15 is melted, and the projecting section 15 and the thin-film 13 on the projecting section 15 are removed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for patterning thin films and a method for manufacturing pyroelectric thin films.

Conventional Technology There are various techniques for forming thin film patterns, but they can be broadly classified into two types: etching and lift-off.

The steps of the etching method are shown in FIG. The etching method is
(a) After forming a thin film 2 to be patterned on the substrate l, (b) forming a resist pattern 3 on the i film 2, and (c) forming a thin film using an etchant that dissolves only the l film 2. This method involves etching the resist pattern 2 and leaving only the thin film 4 under the resist pattern 3.
is removed with a solvent, etc.

The steps of the lift-off method are shown in FIG. The lift-off method is
(a) A resist pattern 6 is formed on the substrate 5 so that the opening 7 becomes smaller toward the top, and (b) a thin film 8 is formed thereon. (c) only the resist 6 is formed. There is a method of forming a pattern of the thin film 8 by removing the thin film 8 on the resist 6 along with the resist 6 using a soluble solvent. By forming the resist 6 into an inverted tapered shape, the thin film 8 is not formed in the inverted tapered portion 9 of the resist 6 when forming the thin film 8, and the solvent permeates through the cuts 9 in the thin film and the resist is quickly removed. It becomes like this.

Problems to be Solved by the Invention The etching method requires an etchant that dissolves only thin films. Etchant that melts resist and substrates causes poor pattern formation and other circuit characteristics. Therefore, the thin films that can be patterned by etching are limited.

In the lift-off method, since an organic resist is used, the conditions for forming a thin film after forming a resist pattern are considerably limited. In other words, the resist is at a high temperature (150
It has problems such as damage and deterioration due to exposure to plasma shock, ultraviolet rays, etc.), making it no longer soluble in solvents, or deforming from an inverted tapered shape, resulting in no breaks in the thin film, making it impossible to separate the thin film properly. .

Both the etching method and the lift-off method limit the number of thin films that can be patterned, and there are many thin films that cannot be separated by either method.

For example, thin films using ceramic materials generally have high chemical resistance and require high film formation temperatures, so there is no method for forming fine patterns.

Means for Solving the Problems: Etching a substrate to form a protrusion having an overhang shape, forming a patterned thin film on the substrate, etching and removing the protrusion of the substrate, and simultaneously etching the protrusion of the substrate. The thin film on top is removed, leaving only the thin film on the opening of the substrate.

By etching the working substrate, a pattern having an inverse taper is created on the substrate, a thin film is formed on this, and the protruding portion of the substrate and the thin film thereon are simultaneously removed by etching to form the pattern. In the lift-off method, a reverse taper was formed using an organic resist, but in the present invention, a reverse taper is formed by etching an inorganic substrate, which is resistant to high temperatures, plasma impact, and ultraviolet rays, and is resistant to deterioration or deformation. For this reason, it is possible to form a pattern on the /il film which could not be patterned by etching or by the lift-off method.

Embodiment FIG. 1 shows an embodiment of the pattern forming method of the present invention. (
a) A pattern of photoresist 11 (microbodies 1400) is formed on an MgO substrate 10 using photolithography. (b) This MgO substrate 10 is
When etching is performed using concentrated phosphoric acid at a temperature of .degree. C., the MgO remaining without being etched forms an inverted tapered shape in which the opening 12 becomes smaller toward the top. As for the etching conditions, it is easier to form a reverse taper when the temperature is relatively high and the phosphoric acid concentration is high. (C) P b O, 9L aO, IT i O, 97503 on this MgO substrate lO
A thin film 13 (hereinafter abbreviated as PLT thin film) having the following structure was formed using an RF magnetron sputtering method. (d) Using concentrated phosphoric acid, the protrusion 15 of the MgO substrate 1O and the PLTi film 13 on the protrusion 15 are removed by etching. Phosphoric acid permeates through the cut 14 in the PLT thin film that occurs in a part of the reverse taper of the MgO substrate 10 during the formation of the PLTi film 13, dissolves the protrusion 15 of the MgO substrate, and dissolves the protrusion 15 and the PLT thin film 1.3 thereon. is removed. In this way, only the PLT thin film 13 on the opening 12 of the MgO substrate 20 remains, allowing pattern formation.

This PLT thin film 13 shows excellent characteristics as a pyroelectric infrared sensor, and is also made of MgO single crystal (100).
By forming a film on a surface or a (100) oriented Pt thin film, a pyroelectric infrared sensor with high sensitivity can be obtained, with C-axis orientation and naturally aligned polarization, without the need for polarization treatment. However, since this PLT thin film is resistant to acids and there is no suitable etchant, it is difficult to pattern the PLT thin film by etching. Furthermore, the film formation temperature must be as high as 600° C. to align the C-axis and naturally align the polarization, so a lift-off method using photoresist cannot be used. For this reason, conventionally, a metal mask is used to form a pattern when forming a PLTN film. With this method, it is not possible to form fine patterns of 100 μm or less.

Therefore, when the PLTa film 13 is formed on the MgO substrate IO with a reverse taper as described above, the MgO substrate 10 can withstand a high temperature of 600°C, so the PLTa film 13 is
A pattern of the film 13 can be formed, and microfabrication of 100 μm or less is also possible.

The thin film pattern forming method of the present invention is not limited to PLTi films, but also enables pattern formation of other thin films that cannot be patterned by etching or lift-off methods.

Effects of the Invention By using the thin film pattern forming method of the present invention, it becomes possible to form patterns on thin film materials that could not be patterned using conventional etching methods or lift-off methods.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the steps of the thin film pattern forming method according to the present invention, and FIGS. 2 and 3 are sectional views showing the steps of the conventional thin film pattern forming method. lO...substrate, 11...resist, 12...opening 13...thin film, 14...cut in thin film, 15...
・Protrusion.

Claims (3)

[Claims] (1) A step of etching a substrate to form a protrusion having an overhang shape, a step of forming a thin film to be patterned on the substrate, and a step of etching and removing the protrusion of the substrate while simultaneously removing the protrusion of the substrate. A thin film pattern forming method comprising the step of removing the thin film above. (2) The thin film pattern forming method according to claim 1, wherein MgO is used for the substrate, and the etchant for the substrate contains phosphoric acid. (3) A method for producing a pyroelectric film, which includes the step of using a pyroelectric material for the thin film and producing a fine pattern of the thin film on a substrate using the thin film pattern forming method according to claim 1.