JPS6367531A - Dielectric thin film element and its manufacture - Google Patents

Abstract

PURPOSE:To prevent a dielectric thin film from being affected by an etchant by forming an insulator thin film which has resistance to the etchant on the dielectric thin film so as to enclose the dielectric thin film together with the lower electrode. CONSTITUTION:A platinum thin film is formed as a lower electrode 12 on a substrate 11. The same device with the formation of this lower electrode 12 is used to form a thin film of Pb0.9La0.1Ti0.975O3 on the lower electrode 12 as the dielectric thin film 13. Further, as an upper electrode 14, an Ni-Cr thin film is formed on the dielectric thin film 13. The upper electrode 14 is made smaller in area than the dielectric thin film 13 not to be short-circuited with the lower electrode 12, and the part where the leadout part of the upper electrode 14 overlaps with the border of the dielectric thin film 13 is previously insulated by an SiO2 thin film. Further, an SiO2 thin film is formed as an insulator thin film 15 on the dielectric thin film 13 so as to enclose the dielectric thin film 13 together with the lower electrode 12.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a dielectric thin film element, particularly the structure of a pyroelectric infrared sensor and its manufacturing method.

BACKGROUND OF THE INVENTION FIG. 3 shows a cross section of an example of a conventional dielectric thin film element. Further, FIG. 4 is a top view thereof. Lower electrode 2 on substrate 1
A dielectric thin film 3 is created on the lower electrode 2, an upper electrode 4 is created on the dielectric thin film 3, and a portion 5 of the substrate 1 corresponding to the back surface of the dielectric thin Mi3 is removed. ing. The removed portion 5 of the substrate 1 is created by etching from the back side.

Problems to be Solved by the Invention Some dielectric thin film devices require or have improved performance by removing the substrate. For example, an infrared sensor that uses the pyroelectric effect converts the temperature rise caused by infrared absorption into an electrical signal.
By removing the substrate, heat conduction to the outside is reduced, and temperature changes are made thicker (by which the sensitivity is improved.In addition, vibration sensors using piezoelectric effects have lower heat transfer by removing the substrate and creating a cantilever structure. Sensitivity on the frequency side is improved.Wet etching is used to remove the substrate in this way.

In the dielectric thin film element shown in the conventional example, since an etching solution strong enough to dissolve the substrate material is used, there is a high possibility that the dielectric thin film 3 itself will be immersed. Also, the lower electrode 2
Even if etching is used as an etching stopper, etching takes time because the substrate is thick, and there are localized areas where etching ends early and areas where etching is slow. This results in corrosion and cracking due to penetration and circulation of the etching solution, resulting in poor yield.

The present invention aims to solve the above-mentioned problems and to obtain a dielectric thin film element with a portion of the substrate removed at a high yield.

Means for Solving the Problems In order to solve the above problems, the present invention has a dielectric thin film provided with electrodes on both sides and an insulating thin film on a substrate, and the dielectric thin film of the substrate In the dielectric thin film element in which a portion corresponding to the back surface of the dielectric thin film is removed, the insulating thin film is made of a material that has a slower removal rate with respect to the means for removing the substrate than the substrate, and The surface of the body thin film is covered with the insulating thin film.

Function In the dielectric thin film element shown in the conventional example, there is a risk that the dielectric thin film may be immersed in the etching solution. By forming the dielectric thin film so as to wrap it around the body thin film, the dielectric thin film is not immersed in the etching solution.

In other words, even if the etching solution penetrates between the masking material on the dielectric thin film and the dielectric thin film during etching, there is an insulator thin film on the dielectric thin film and a lower electrode on the back side, so the etching solution will not be able to penetrate directly into the dielectric thin film. This is because they never come into contact with the

Embodiment FIGS. 1 and 2 show an embodiment of the present invention. FIG. 1 is a sectional view thereof, and FIG. 2 is a top view thereof.

A (100)-oriented MgO single crystal was used as the substrate 11, and a (100)-oriented thin film of platinum was formed as the lower electrode 12 on the substrate 11 by RF magnetron sputtering. Using the same apparatus and the same vapor deposition mask as used to form the lower electrode 12, a dielectric thin film 13 of PbO, 9L"0.I
T'0.975 9 (hereinafter abbreviated as PLT) of (0
01) An oriented thin film was created. In other words, a PLT thin film of the same size as the platinum electrode was created on the platinum electrode. A NiCr thin film was formed on the dielectric thin film 13 as the upper electrode 14 . Note that the upper electrode 14 has a smaller surface than the dielectric thin film 13 in order to prevent short-circuiting with the lower electrode 12, and the overlapping portion of the lead-out portion of the upper electrode 14 and the boundary of the dielectric thin film 13 is covered with a SiOs thin film in advance. I kept it insulated. Furthermore, an insulator thin film 15 is placed on the dielectric thin film 13.
A SiO2 thin film was formed so as to wrap around the dielectric thin film 13 together with the lower electrode 12. The same RF magnetron sputtering device was used to create this S i O 2 thin film. Table 1 shows the thickness of each component of this dielectric thin film element.
Shown below.

Table 1 The dielectric thin film element prepared above is intended for use in a pyroelectric infrared sensor, and the PLT used has a high performance as a pyroelectric material, and its (001) orientation makes it even more sensitive. Currently, there are only a limited number of substrates on which a (001) oriented thin film of PLT can be formed, and MgO and a (100) oriented platinum thin film formed on MgO are limited substrate materials. Since the pyroelectric infrared sensor converts temperature rise due to infrared absorption into an electrical signal, high sensitivity can be achieved by removing the substrate 11, reducing heat conduction to the outside, and increasing temperature change.

Therefore, a portion 17 of the MgO substrate 11 corresponding to the back surface of the portion of the dielectric thin film 13 that is effective as a sensor was removed by etching. On the other hand, in the dielectric element manufacturing process described above, a device was also created in which the MgO substrate 11 was removed without forming the 5i02 thin film as the insulator thin film 15. Note that this embodiment uses a dielectric thin film 1 for use in an array sensor.
3 is separated into each element in order to suppress heat conduction between each element and reduce crosstalk.

Phosphoric acid at 70° C. was used as the etching solution, the top surface of the dielectric thin film element was masked with protective wax, and the back surface was etched by forming an etching pattern with photoresist. In order to examine the acid-resistant effect of the 5i02 thin film as the insulator thin film 15, we etched samples with and without the insulator thin film 15, and continued etching even after the lower electrode 12 was exposed. The number of cracks in the thin film 13 was measured. The results are shown in Table 2.

Table 2 From Table 2, insulator thin film 1 that is resistant to etching liquid
The effect of No. 5 is obvious, but the reason for this is that phosphoric acid penetrates between the protective wax and the dielectric thin film 13, and if there is no insulating thin film 15, the dielectric thin film 13 is immersed from the top surface. This can be considered. The dielectric thin film 1 is an insulating thin film 15 that is resistant to phosphoric acid even if phosphoric acid penetrates into it.
3, the dielectric thin film 13 does not come into direct contact with the phosphoric acid and is therefore not immersed. Cracks also occur when the insulating thin film 15 is present, but this is thought to be due to the phosphoric acid penetrating the insulating thin film 15 little by little. If more time is required, the insulator thin film 15 may be made thicker.

According to the present invention, in the etching process of the substrate 11, it is possible to obtain a dielectric thin film element with a good yield without causing cracking or corrosion of the dielectric thin film 13.

Effects of the Invention According to the present invention, in the process of producing a dielectric thin film element by removing a part of the substrate, it is possible to obtain the dielectric thin film element with a high yield without causing cracking or corrosion of the dielectric thin film. became.

[Brief explanation of drawings]

1 and 2 are a sectional view and a top view showing an embodiment of the present invention, respectively, and FIGS. 3 and 4 are a sectional view and a top view showing a conventional example. DESCRIPTION OF SYMBOLS 11... Substrate, 12... Lower electrode, 13... Dielectric thin film, 14... Upper electrode, 15... Insulator thin film. Name of agent: Patent attorney Toshio Nakao and one other person Figure 1 Figure 2 Figure 30 4J: See the department Figure 4

Claims (3)

[Claims] (1) In a dielectric thin film element having a dielectric thin film with electrodes provided on both sides and an insulating thin film on a substrate, a portion of the substrate corresponding to the back surface of the dielectric thin film is removed. , the insulating thin film is made of a material that has a slow removal rate relative to the substrate with respect to the means for removing the substrate,
A dielectric thin film element characterized in that a surface of the dielectric thin film is covered with the insulating thin film. (2) The dielectric thin film element according to claim 1, wherein the substrate and the dielectric thin film are made of a material that can be immersed in acid, and the insulating thin film has acid resistance. (3) In the step of creating a dielectric thin film having electrodes on both sides on a substrate and removing a portion of the substrate corresponding to the back surface of the dielectric thin film, the substrate is removed relative to the substrate. A method for manufacturing a dielectric thin film element, characterized in that the substrate is removed after the dielectric thin film is covered with an insulating thin film made of a material that has a slow removal rate relative to the means.