JPH0722207B2 - Pyroelectric element manufacturing method and pyroelectric element manufactured by the same method - Google Patents

Description

Detailed Description of the Invention a. TECHNICAL FIELD The present invention relates to a thin pyroelectric element.

B. 2. Description of the Related Art Pyroelectric devices have been widely used recently as infrared sensors, but in order to improve the S / N value of pyroelectric devices, it is required to develop as thin a device as possible. Since the rate of temperature change of the pyroelectric element is inversely proportional to the heat capacity, if the element is thin, the heat capacity decreases and the rate of temperature change of the element increases. However, as the element becomes thinner, the capacitance of the element increases and the voltage sensitivity to temperature rise decreases, so the voltage sensitivity to the amount of light is the same, but noise, especially tan δ noise and input resistance noise, decreases when the capacitance is large. . Therefore, if the element is thinned, the S / N value will be improved overall.

Thus, it is desirable to thin the element in order to improve the S / N value of the pyroelectric element. There are many types of pyroelectric elements, but among them, LiTaO ₃ has a Curie temperature of 610.
Since it is as high as ℃, it has no deliquescent property and good pyroelectric performance, it is desired to develop an element that can be stably joined to the electrode with a thin element, but in the past, cracks occurred during the process of thinning the element. Then, it was not possible to stably manufacture an element having a thickness of 20 μm or less. Also, in order to avoid cracks, it is necessary to use very fine abrasives,
Even if a thin element is produced, the surface of the element will be mirror-like or close to it, and peeling and cracking will occur when electrodes (Pt, Au, Al, Cr, etc.) are attached to the element surface by vapor deposition, sputtering, etc. There was a problem that it was easy.

C. DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention It is an object of the present invention to provide a pyroelectric element, particularly LiTaO ₃ , which can be stably made thin and which is less likely to cause electrode peeling or cracking.

D. Means for Solving Problems A device substrate that has been thinned to a certain extent by a conventional method, such as a polishing method, for polishing a single crystal plate of a pyroelectric element with abrasive grains having different roughnesses By setting the surface so that it is immersed in the liquid, heating the solution to an appropriate temperature, and stirring it appropriately, the element is dissolved in the solution and subjected to a thinning process. A ground glass element substrate having appropriate irregularities is manufactured, and electrode films are formed on both surfaces of the element substrate.

E. In pyroelectric element, especially in LiTaO ₃ , the element substrate is thinned to a certain extent by the conventional thinning process such as polishing method, and finally by finishing the both surfaces by the dissolving action in the hydrofluoric nitric acid solution. Moreover, it becomes possible to easily manufacture an element having appropriate unevenness on at least one surface due to the corrosive action of the acid solution, and it is possible to easily manufacture a pyroelectric element of 15 μm or less. In addition, since the manufactured element has a rough surface as described above, the adhesive area with the electrode increases, and the resistance to the force parallel to the surface increases due to the unevenness of the surface, It has become possible to easily fabricate an element in which electrode peeling or cracking caused by changes or the like is unlikely to occur.

F. Example FIG. 2 shows an example of one processing step of the device of the present invention. In FIG. 2, 1 is a LiTaO ₃ single crystal that is a substrate of a pyroelectric element, 2 is a glass table that is a processing table when thinning the single crystal 1, and 3 is a melting box made of Teflon. Reference numeral 4 is a melting vessel for containing a single crystal, which has a fine hole at the bottom. Reference numeral 5 is a hydrofluoric nitric acid solution for dissolving the single crystal, 6 is a plate heater for raising the temperature of the hydrofluoric nitric acid solution, and 7 is a stirrer.

In FIG. 2A, 1 is a pre-poled LiTaO ₃ single crystal Z plate, which is an element substrate having a diameter of 2.0 inch to 4.0 inch and a thickness of 100 μm or more. The cathode side surface is polished to a mirror surface or a surface close to it. To process.

In FIG. 2B, the mirror-finished cathode surface of the element substrate 1 processed above is adhered to the glass base 2. The mirror-finished surface on the cathode side improves adhesion to the glass table, and
This is because when the adhesive is peeled off, the peeling is facilitated.

In FIG. 2C, the anode-side surface of the above-bonded element substrate is lapped with 1000 # abrasive grains to 50 μm.

In FIG. 2D, the anode surface of the element substrate, which has been lapped to 50 μm as described above, is further lapped to 20 μm with 4000 # abrasive grains.

In FIG. 2E, the element substrate lapped to 20 μm is removed from the glass table 2 and placed in a container 4 with the anode surface facing upward and the bottom having fine holes. The container 4 is installed in the dissolution box 3 which can be stirred. A 50% hydrofluoric acid solution and a 70% nitric acid solution are mixed in the same box 1 at a ratio of 1: 1, and the mixed solution 5 is put in the box 3 until the element substrate 1 is submerged in the same solution 5. The solution is heated to 80 ° C. by 6 and left for about 2 hours while stirring the solution by bubbling in water (not shown), and then the element substrate 1 is taken out and washed with water.

In the process of the acid treatment, the element substrate 1 has a faster dissolution rate on the cathode side than on the anode side. Therefore, the reduction of the thickness of the substrate due to the acid treatment mainly proceeds on the surface on the cathode side.

By processing in such a step, a ground glass-like element substrate 1 having a thickness of 10 μm and having appropriate irregularities on both surfaces is prepared.

As shown in FIG. 2, sand scratches caused by abrasive grains on the anode surface of the element substrate 1 obtained as shown in FIG. 2 become a tilment-like surface having gentle irregularities due to acid treatment, and the cathode surface has a myriad of finely-etched concave pyramids. It is covered with pits and looks like a shimmering diamond glass when viewed under a microscope of about 300 times.

G. Effect According to the present invention, the dissolution processing using hydrofluoric nitric acid enables processing without straining the element during processing, and the surface becomes a rough surface due to the dissolution action. It has become possible to easily provide a pyroelectric element having a thickness of 15 μm or less that does not peel off or crack.

[Brief description of drawings]

FIG. 1 is a sectional view of an embodiment of the present invention, FIG. 2 is a working process drawing, and A, B, C, D and E are intermediate process drawings.

Claims (2)

[Claims] 1. A pyroelectric element single crystal thin plate, at least one surface of which is immersed in a hydrofluoric nitric acid solution, and the solution is heated and stirred to dissolve the thin plate surface, thereby further thinning the thin plate and making it pyroelectric. A method for manufacturing a pyroelectric element, which comprises using an element substrate. 2. A pyroelectric element single crystal substrate having a thickness of 15 μm or less,
A pyroelectric element characterized in that at least one surface has a ground glass shape having irregularities generated during the melting process.