CN106409818A - Method of acquiring flexible ferroelectric thin film capacitor nondestructively - Google Patents

Abstract

The invention discloses a non-destructive method for obtaining flexible ferroelectric film capacitance, which belongs to the field of ferroelectric devices and semiconductor technology. The present invention obtains inorganic substrates and flexible ferroelectric film capacitors through a convenient and economical method. Common materials such as corundum, industrial wax, glass flakes, and glass plates are used as tools for substrate grinding, and a heating platform is used to make the industrial The wax melts and bonds the glass sheet and PZT, and then uses corundum to thin the rigid PZT device with a substrate thickness of about 500 μm to 100 μm thick to become a flexible PZT, and then use a small amount of chemical reagents to remove the residual industrial adhesion on the surface of the device wax. The method is simple in principle, low in cost, safe and reliable. Compared with other methods, flexible ferroelectric thin film devices can be obtained faster and safer without losing its excellent electrical properties, and the flexible device remains stable under repeated stress conditions. It can maintain good electrical properties and has excellent reliability.

Description

A non-destructive method for obtaining flexible ferroelectric film capacitors

technical field

The invention relates to the field of ferroelectric thin film devices and semiconductor technology, is applicable to various ferroelectric thin film capacitors, and is mainly used to obtain ferroelectric thin film capacitors with flexible characteristics.

Background technique

With the development of semiconductor technology level, the development of flexible substrate devices based on ferroelectric materials has received more and more attention. Its good physical and chemical properties make flexible substrate devices have very broad application prospects. Traditional silicon-based materials are mechanically brittle and difficult to withstand large deformations, so silicon-based material devices have their own limitations in flexible applications.

In general, flexible devices are grown on organic substrates, and their electrical properties are far from ideal for devices grown on inorganic substrates. At the same time, considering that the fabrication of organic flexible substrate devices has high requirements on equipment and processes, it requires a lot of time and capital investment. Based on this, we propose a more convenient and economical method to obtain flexible ferroelectric thin film capacitors, which can ensure that its electrical properties will not be affected. At the same time, it can deform under large stress conditions, and maintain the original electrical properties, and has the characteristics of flexible devices.

The invention provides a method for obtaining flexible ferroelectric film capacitance conveniently, and the method is simple and quick, and can also be applied to other small-sized silicon substrate devices.

Contents of the invention

The object to be achieved by the present invention is to provide a safe and reliable method to grow lead zirconate titanate (PbZr _0.44 Ti _0.56 O ₃ , PZT) film capacitor structure Pt/PZT/Pt/SiO on a silicon (Si) substrate ₂ /Si is the main research object. By grinding the rigid silicon substrate, the flexible PZT film capacitor can be obtained without destroying the structure and performance of the device.

To achieve the above object, the present invention provides the following solutions:

The structural features of a lead zirconate titanate (PbZr _0.44 Ti _0.56 O ₃ , PZT) film capacitor grown on a silicon substrate include: a silicon substrate 1, an epitaxial buffer silicon dioxide layer 2, a lower electrode 3, PZT4, and an upper electrode 5. The material of the lower electrode 3 and the upper electrode 5 is platinum. The epitaxial buffer silicon dioxide layer 2 is grown on the silicon substrate 1, the lower electrode 3 is grown on the epitaxial buffer silicon dioxide layer 2, the PZT4 is grown on the lower electrode 3, and the upper electrode 5 is grown on the PZT4.

First protect the upper electrode 5 and PZT4 with industrial wax 6, and use the thermal melting and condensation of the industrial wax 6 to bond the upper electrode 5 and the small glass piece 7 together, and then use emery to realize the grinding of the substrate.

A non-destructive method for obtaining a flexible ferroelectric thin film capacitor using the above structure as a sample, the steps of the method are implemented as follows.

The experimental equipment for implementing the method includes: a lead zirconate titanate (PbZr _0.44 Ti _0.56 O ₃ , PZT) film capacitor structure grown on a silicon substrate, corundum, industrial wax 6, small glass pieces 7, large glass plates, Spiral micrometer, blades, tweezers, heating platform, chemical reagents, lens paper, small beakers, spring steel sheets. Chemicals include carbon tetrachloride, trichloroethylene, acetone, ethanol, and deionized water; a heated platform melts the wax.

Step 1: Protect the upper electrode 5 on the top of the PZT4 by using the thermal melting and condensation of the industrial wax 6, and bond the upper electrode 5 to one side of the small glass piece 7 at the same time.

Step 2: Use corundum to grind a silicon substrate 1 with a lead zirconate titanate film capacitor structure grown on a silicon substrate, hold a small glass piece 7 and "draw a character 8" on the silicon substrate 1 until The thickness of the silicon substrate 1 is reduced to about 100 μm.

Step 3: heat the small glass piece 7 again to melt the industrial wax 6, remove the PZT4 and put it into a small beaker lined with lens paper, and use chemical reagents to clean it finally.

Considering that electrical measurement needs to be carried out before and after the sample is ground, and that it needs to maintain a relatively tight bond with the small glass piece 7 during the grinding process, industrial wax 6, a relatively stable material, is used.

The PZT silicon substrate 1 is quickly ground by using corundum, and the main component of corundum is Al ₂ O ₃ , which will not affect the performance of the sample.

The final chemical reagent cleaning can effectively remove the protective industrial wax 6 attached to the top of the PZT4, so as to prevent the residual industrial wax 6 from affecting the electrical properties of the sample. Rigid sample: a sample with a thick substrate and no flexible characteristics (that is, the electrical properties degrade after repeated bending). Flexible sample: obtained by this method, the substrate is thinned and has the characteristics of a flexible device (that is, the electrical performance does not degrade after repeated bending).

In this method, industrial wax is used to protect the top electrode before grinding the PZT thin film capacitor grown on the silicon substrate, so that the electrode structure on the top of the sample will not be damaged during the thinning process of the substrate. The material can safely and quickly complete the thinning operation of the substrate without affecting the electrical properties of the sample, thereby obtaining flexible PZT.

The thinned PZT can better achieve repeated bending, has the properties of a flexible device, and has no degradation in electrical performance. Moreover, the method is simple and easy to implement, simple to operate, widely used, and low in price, and can be used in any field where flexible ferroelectric thin film capacitors need to be obtained.

Description of drawings

The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

Figure 1 is a PZT film capacitor structure of lead zirconate titanate grown on a silicon (Si) substrate.

Figure 2 shows the PZT structure of a rigid silicon substrate bonded to a glass sheet.

Figure 3 shows a flexible (after substrate grinding) PZT structure bonded to a glass sheet.

Figure 4 is a comparison of the hysteresis loops of rigid and flexible PZT samples.

Fig. 5 is the electric hysteresis loop of the flexible PZT under different stress circles.

Fig. 6 is a comparison of electric hysteresis loops measured after repeated bending of PZT of a rigid silicon substrate (substrate thickness is about 500 μm) 5 times (strain 0.186%) and 55 times (strain 0.186%).

In the figure: 1. Silicon substrate, 2. Epitaxial buffer layer silicon dioxide (SiO ₂ ) layer, 3. Lower electrode, 4. PZT, 5. Upper electrode, 6. Industrial wax, 7. Glass sheet.

detailed description

A PZT structural feature of a rigid silicon substrate includes: a silicon substrate 1 , an epitaxial buffer silicon dioxide (SiO ₂ ) layer 2 , a lower electrode 3 , a PZT 4 , and an upper electrode 5 , as shown in FIG. 1 .

Before grinding, measure the hysteresis loop of the sample in advance to compare the subsequent measurement results. The instrument used is a ferroelectric performance tester. The test conditions are: voltage 40V, frequency 1kHz, and test waveform is triangular wave.

First, heat up the heating platform, put the small glass piece 7 on the heating platform, and at the same time place a small piece of industrial wax 6 at the center of the small glass piece 7, when the industrial wax 6 is completely melted (about 80 ℃ ) clamp the sample with tweezers, at this time the sample is rigid, and at the same time the silicon substrate 1 is facing up, placed in the center of the small glass piece 7, so that it is fully in contact with the industrial wax 6, as shown in Figure 2.

Then take off the small glass sheet 7 and cool to normal temperature, scrape off the redundant industrial wax 6 around PZT4 with a blade after it cools completely, and note that the side that the small glass sheet is stuck with PZT4 is the front.

Take an appropriate amount of corundum and place it on the large glass plate, measure the thickness of the small glass piece 7 glued with PZT with a spiral micrometer and record it, place the small glass piece 7 face down on the large glass plate covered with corundum, press and hold Small glass sheet 7 and " draw 8 characters " on the large glass plate.

Always keep corundum between the silicon substrate 1 and the large glass plate, and repeat the above operation, measure the thickness of the small glass plate 7 bonded with PZT4 with a spiral micrometer every 10 times or so, and compare with the previous measurement results. Compare.

Since the thickness of the sample is about 500 μm, the amount of grinding of the silicon substrate can be obtained through the difference before and after grinding, and then the remaining thickness of the silicon substrate 1 can be obtained.

Stop grinding when the thickness of its silicon substrate 1 is reduced to about 100 μm, and wipe off the corundum on the small glass sheet 7 with a clean test paper, as shown in Figure 3.

At this time, the obtained flexible PZT together with the glass sheet was placed on the heating platform again to be heated until the industrial wax 6 melted, and the ground PZT was removed with tweezers. Put the lens paper on the bottom of the beaker, put carbon tetrachloride and PZT, take out the PZT after boiling for 2 minutes, then repeat the above operation with trichloroethylene, acetone, ethanol reagents, and finally rinse the PZT with deionized water for at least 20 times , to remove residual chemical reagents.

The probe station and ferroelectric performance tester are used to measure the hysteresis loop of the sample, so as to judge whether the electrical characteristics of the sample have changed before and after grinding. And the measurement results are integrated, as shown in Figure 4.

In order to determine the difference in electrical properties between rigid and flexible PZT samples under different bending amplitudes, the flexible PZT samples were bonded to a spring steel sheet of 30mmx8mmx0.5mm, and the samples were made to have a size of 0.186%, 0.223%, and 0.260% by applying an external force. Each strain was applied repeatedly 50 times, and the hysteresis loop of the sample was measured. The results are shown in Figure 5, and the polarization value of the sample did not degrade.

Take a PZT sample of a rigid silicon substrate, make it produce 5 times of 0.186% bending strain and 50 times of 0.186% bending strain, and measure its hysteresis loop. The results are shown in Figure 6, after the sample was repeatedly bent 50 times, its polarization value degraded by 22.8%.

It is considered that the electrical properties of the obtained flexible PZT sample have not degraded, and at the same time, it can maintain its electrical properties (electrical hysteresis loop) after hundreds of repeated bendings, which is more stable than the PZT sample of the rigid silicon substrate. With flexible characteristics.

Finally, it should be noted that: the above embodiments are only used to illustrate the best embodiments of the present invention, rather than limit the technical solutions described in the present invention; therefore, those of ordinary skill in the art should understand All equivalent changes should fall within the scope of the claims of the present invention.

Claims (3)

1. a kind of non-destructive obtain flexible ferroelectric capacitor method it is characterised in that：The structure realizing the method includes Silicon substrate (1), epitaxial buffer silicon dioxide layer (2), bottom electrode (3), PZT (4), Top electrode (5)；Bottom electrode (3) and Top electrode (5) material is platinum；Epitaxial buffer silicon dioxide layer (2) is grown on silicon substrate (1), and bottom electrode (3) is grown in epitaxial buffer In silicon dioxide layer (2), PZT (4) is grown on bottom electrode (3), and Top electrode (5) is grown on PZT (4)；

First Top electrode (5) and PZT (4) are protected with industrial wax (6), and made using the hot melt and condensation of industrial wax (6) Electrode (5) is bonded together with little sheet glass (7), and then realizes the grinding of substrate with diamond dust；

The method that a kind of non-destructive being carried out as sample by the use of said structure obtains flexible ferroelectric capacitor, the method Step is implemented as follows；

The experiment equipment implementing the method includes：A kind of growth PZT thin film capacitance structure on a silicon substrate, diamond dust, Industrial wax (6), little sheet glass (7), big glass plate, screw-thread micrometer, blade, tweezers, heating platform, chemical reagent, lens paper, Small beaker, spring steel plate；Chemical reagent includes carbon tetrachloride, trichloro ethylene, acetone, ethanol and deionized water；Heating platform energy Wax is enough made to melt；

Step one：Hot melt and condensation using industrial wax (6) are protected to the Top electrode (5) at PZT (4) top, simultaneously will be upper Electrode (5) is bonded with the side of little sheet glass (7)；

Step 2：Using diamond dust, to a kind of growth, the silicon substrate (1) of PZT thin film capacitance structure on a silicon substrate enters Row grinds, and holds little sheet glass (7) and " draws 8 words " above in silicon substrate (1), until silicon substrate (1) thickness reduces to 100 μm of left sides Right；

Step 3：So that industrial wax (6) is melted little sheet glass (7) heating again, take off PZT (4) and put into and be lined with lens paper In small beaker, using chemical reagent, it is done with last cleaning；

Need to carry out electrical measurement before and after grinding in view of sample, and need to keep relatively with little sheet glass (7) in process of lapping For close tacky state, therefore adopt industrial wax (6) this relatively stable material；

Using the silicon substrate (1) of diamond dust ground PZT quickly, the main component of diamond dust is Al simultaneously₂O₃, will not be to sample Moral character can produce impact；

Last chemical reagent cleaning can effectively remove the industrial wax (6) being attached to PZT (4) top, shielding, with Prevent from remaining industrial wax (6) and the electric property of sample being produced affecting.

2. a kind of non-destructive according to claim 1 obtain flexible ferroelectric capacitor method it is characterised in that：Grind In advance the ferroelectric hysteresis loop of sample is measured before mill, be that subsequent measurement contrasts, the instrument of use is surveyed for ferroelectric properties Try instrument, test condition is：Voltage 40V, frequency 1kHz, test waveform is triangular wave.

3. a kind of non-destructive according to claim 1 obtain flexible ferroelectric capacitor method it is characterised in that：First Warming temperature is carried out to heating platform, while little sheet glass (7) is put on heating platform, one fritter industrial wax (6) is placed in The center position of little sheet glass (7), clamps sample with tweezers after industrial wax (6) melts completely, and now sample is rigidity, with When silicon substrate (1) face up, be placed on the center of little sheet glass (7) so as to be fully contacted with industrial wax (6)；

Then take off little sheet glass (7) and be cooled to normal temperature, after it cools down completely, wipe unnecessary work around PZT (4) off with blade Industry wax (6), remembers that the one side that little sheet glass is stained with PZT (4) is front；

Take appropriate diamond dust to be placed on big glass plate, be stained with little sheet glass (7) thickness of PZT with screw-thread micrometer measurement and remember Under, little sheet glass (7) face down is placed on the big glass plate being covered with diamond dust, pins little sheet glass (7) and in big glass " 8 words are drawn " in glass plate；

Moment keeps there is diamond dust between silicon substrate (1) and big glass plate, and repeats aforesaid operations, uses spiral every 10 times about Micrometer measures to little sheet glass (7) thickness being stained with PZT (4), and compared with measurement result before；

Thickness due to sample is about 500 μm, obtains the amount of grinding of silicon substrate by the difference before and after grinding, and then learns that silicon serves as a contrast Bottom (1) residual thickness；

Stop when the thickness of its silicon substrate (1) is thinned to about 100 μm grinding, wiped on little sheet glass (7) with clean test paper Diamond dust；

Now the flexible PZT obtaining is placed into heating on heating platform again together with sheet glass, until industrial wax (6) melts, Take off the PZT after grinding with tweezers；By camera lens paper washer to beaker bottom, put into carbon tetrachloride and PZT, take out after boiling 2 minutes PZT, then uses trichloro ethylene, acetone, ethanol reagent to repeat aforesaid operations, last deionized water rinses PZT extremely repeatedly successively Few 20 times, to remove residual chemical agents.