JP2001060731A - Method for fabrication of piezoelectric ferroelectric device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To protect a structure against damage by stripping the structure from a first substrate without using a laser light irradiation process thereby providing a degree of freedom in the selection of substrate material. SOLUTION: A diaphragm is stripped off from a first substrate 101 together with a polyester film sheet 105 and an adhesive layer 106 by setting the bonding force between the diaphragm and the polyester film sheet 105 higher than adhesion between platinum in the lowermost layer of a lower electrode 102 formed through an intermediate layer and silicon dioxide in the uppermost layer of the first substrate 101. Adhesion strength is then weakened between the polyester film sheet 105 and the upper and lower electrodes 104, 102 by irradiating the adhesive layer 106 with a UV ray through the polyester film sheet 105 which is thereby stripped off further from a second substrate 108.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a piezoelectric / ferroelectric thin film device in which a piezoelectric / ferroelectric thin film is formed on a first substrate and transferred to a second substrate to form a device. About the method.

[0002]

2. Description of the Related Art In recent years, PZT (lead zirconate titanate) has been developed.
Based thin films and microactuators using them,
Research and development of devices such as ferroelectric memories and pyroelectric sensors have been actively conducted.

A conventional method for transferring a structure including these functional thin films from a first substrate to a second substrate is as follows.
There is a method described in Japanese Patent Application Laid-Open No. Hei 10-202874 previously proposed by the present applicant. That is, in the "Detailed Description of the Invention" in the same publication, a structure including a separation layer of amorphous silicon or the like and a piezoelectric thin film is formed on a substrate, and the separation layer is irradiated with light. There is disclosed a technique in which the internal structure of the separation layer or the adhesion between the layers in contact with the separation layer is reduced to separate the structure and transfer the structure to another substrate.

[0004]

However, the above-mentioned prior art has the following problems.
First, when the structure including the piezoelectric thin film is separated from the substrate, it is necessary to irradiate the separation layer with light. When a metal electrode is present above the separation layer, the light to be irradiated needs to be incident from the substrate side. Further, when amorphous silicon is used for the separation layer, it is necessary to irradiate ultraviolet laser light such as xenon chloride or krypton fluoride, and in this case, a material such as quartz or glass that transmits the laser light is used as the substrate. Must be used. That is, the selection of the substrate material is restricted. Further, at the time of irradiation with the ultraviolet laser light, damage to the structure including the piezoelectric thin film has occurred. Further, since a separation layer, which is unnecessary in the device configuration, is formed, the number of manufacturing steps is increased, and the cost of the device is increased. Furthermore, the state of separation in the separation layer is different, such as separation from the inside of the separation layer, separation from the interface between the separation layer and the component, or separation from the interface between the separation layer and the substrate. The device characteristics varied due to the cause.

The present invention has been made in view of the above-mentioned problems of the prior art, and has the following objects.

(1) By peeling off the component without using a laser beam irradiation process, it is possible to give a degree of freedom in selecting a substrate material, and a piezoelectric / ferroelectric which does not damage the component. Provided is a method for manufacturing a body thin film device.

(2) To provide a method of manufacturing a piezoelectric / ferroelectric thin-film device at low cost and with little characteristic variation by peeling off a component without using a process for forming a separation layer.

[0008]

In order to solve the above problems, a method of manufacturing a piezoelectric / ferroelectric thin film device according to the present invention comprises the steps of: forming an intermediate layer on a first substrate; Forming a lower electrode having at least one or more conductive layers, forming a piezoelectric / ferroelectric thin film on the lower electrode, and forming at least one layer on the piezoelectric / ferroelectric thin film. Forming an upper electrode having the above conductive layer, patterning the upper electrode and the piezoelectric / ferroelectric thin film, bonding a substrate or sheet from the upper electrode side, Removing the sheet from the first substrate together with the lower electrode, the piezoelectric / ferroelectric thin film, and the upper electrode; and removing the substrate or sheet, the lower electrode, and the piezoelectric / ferroelectric from the first substrate Thin film and the upper electrode Adhering to the second substrate, reducing the adhesive strength of an adhesive layer between the substrate or sheet and the upper electrode, the piezoelectric / ferroelectric thin film and the lower electrode, and bonding the substrate or sheet to the second substrate or sheet. A step of peeling off the substrate, the lower electrode, the piezoelectric / ferroelectric thin film, and the upper electrode.

According to the above configuration, since a process of irradiating the separation layer with light is not used, the degree of freedom in selecting a substrate material is improved, and a piezoelectric / ferroelectric thin film device which does not damage the structure is realized. Is done. Further, since the component can be peeled off without using a process of forming the separation layer, a piezoelectric / ferroelectric device with low cost and little characteristic variation can be realized.

Further, by dissolving an adhesive layer between the substrate or the sheet and the upper electrode, the piezoelectric / ferroelectric thin film, and the lower electrode, the substrate or the sheet is moved to the second substrate, the lower electrode and the lower electrode. It is characterized in that it is peeled off from the piezoelectric / ferroelectric thin film and the upper electrode.

According to the above configuration, the adhesive layer on the piezoelectric / ferroelectric thin film element can be completely removed.

Further, a step of patterning the lower electrode is provided before the step of forming the piezoelectric / ferroelectric thin film or after the step of patterning the upper electrode and the piezoelectric / ferroelectric thin film. And

According to the above configuration, it is easy to keep the surface of the lower electrode clean before forming the piezoelectric / ferroelectric thin film.

The first substrate is a single crystal silicon substrate with a silicon oxide layer, the intermediate layer is Ti or Cr, and the layer of the lower electrode which is in contact with the first substrate is Pt, Ir,
It is characterized by using a noble metal such as Ru.

According to the above configuration, the adhesion between the first substrate and the lower electrode can be slightly improved, and the lower electrode, the piezoelectric / ferroelectric thin film, and the upper electrode can be formed on the first substrate. It is possible to suppress separation that occurs between the first substrate and the lower electrode.

Further, the present invention is characterized in that the first substrate is a single crystal ceramic substrate of strontium titanate, sapphire, magnesia or the like.

According to the above configuration, the piezoelectric / ferroelectric thin film can be epitaxially grown, and a high performance piezoelectric / ferroelectric thin film device can be realized.

[0018]

Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 is a sectional view of a liquid jet recording head as a piezoelectric thin film device according to an embodiment of the present invention in the order of manufacturing steps, and FIG. At the end of the step of forming the diaphragm on the substrate, FIG. 4B shows the step of bonding the substrate or the sheet from the upper electrode side, and FIG. 4C shows the step of peeling the substrate or the sheet together with the diaphragm from the first substrate. At the end, FIG. 9D shows the end of the step of bonding the substrate or sheet and the diaphragm on the second substrate, and FIG. 10E shows the end of the step of peeling the substrate or sheet from the second substrate and the diaphragm. It is sectional drawing at the time.

As the first substrate 101, the present inventors used a single crystal silicon substrate with a silicon dioxide film formed by a thermal oxidation method. Titanium was formed thereon as a middle layer by a sputtering method (not shown), and three layers of a platinum layer, an iridium layer, and a titanium layer were formed as a lower electrode 102 in this order by a sputtering method. And the lower electrode 102
The intermediate layer was patterned by a reactive ion etching (hereinafter referred to as RIE) method. Further, a piezoelectric thin film 103 was formed by a sol-gel method. As the piezoelectric thin film 103, lead zirconate titanate (hereinafter, PZT) containing 10% by mole of lead magnesium niobate (hereinafter, referred to as PMN) is used.
) Was used. The molar ratio of PMN, lead titanate and lead zirconate was 10:40:50. Then, two layers of a titanium layer and an iridium layer were formed in this order by a sputtering method as the upper electrode 104. Thereafter, the upper electrode 104 and the piezoelectric thin film 103 are successively patterned by the RIE method using the same mask, and the sectional view shown in FIG. 1A is obtained. In this case, the diaphragm is constituted by the lower electrode 102, the piezoelectric thin film 103, and the upper electrode 104. Then, the substrate or sheet 105 is adhered to the upper electrode side on the first substrate 101 via the adhesive layer 106, and FIG.
The sectional view shown in FIG. As the substrate or sheet 105, a polyester film sheet to which an acrylic adhesive was applied in advance as the adhesive layer 106 was used. The adhesive strength of the adhesive layer 106 is reduced by UV lamp irradiation. Further, when the polyester film sheet 105 is peeled off from the first substrate 101, a sectional view shown in FIG. 1C is obtained. Adhesive layer 1 between diaphragm and polyester film sheet 105
06 is set so as to be larger than the adhesion between platinum, which is the lowermost layer of the lower electrode 102 formed via the intermediate layer, and silicon dioxide, which is the uppermost layer of the first substrate 101. Thereby, the diaphragm is peeled off from the first substrate together with the polyester film sheet 105 and the adhesive layer 106. The present inventors succeeded in completely peeling the diaphragm over the entire area of the 6-inch Φ substrate by carefully peeling the polyester film sheet 105 from the edge of the substrate 101. Further, the peeled diaphragm, polyester film sheet 105 and adhesive layer 1
FIG. 1D is bonded to the second substrate 108 which has been processed in advance via the bonding layer 107 to obtain
The sectional view shown in FIG. As the second substrate 108, zirconia having a through pattern formed from the front to the back was used, and an epoxy-based adhesive was used for the adhesive layer 107. Thereafter, by irradiating the adhesive layer 106 with UV light through the polyester film sheet 105, the adhesive strength between the polyester film sheet 105 and the upper electrode 104 and the lower electrode 102 is weakened.
Is peeled off from the second substrate 108 to obtain FIG.
The sectional view shown in FIG. This UV light irradiation was performed by a UV lamp. In this case, as compared with the case of irradiating the UV laser light as shown in the conventional example, the light intensity is 1 unit.
/ 100 or less is sufficient, and no damage to the diaphragm (constituent body) as shown in the above-mentioned conventional example occurred. Further, when the diaphragm (constituent body) shown in FIG. 1C is peeled, peeling always occurs at the interface between platinum and silicon dioxide, which has weak adhesion, and a clean peeling interface can be obtained. Variation in plate characteristics was reduced. Also, the first
A non-translucent substrate such as single crystal silicon can be used as the substrate 101, and the degree of freedom in selecting a substrate material is increased.

FIG. 2 is a perspective view of a liquid jet recording head, which is a piezoelectric thin film device, formed by using the manufacturing method of the present invention. In this figure, the same symbols as those in FIG.
Represents the same thing as The diaphragm composed of the lower electrode 102, the PZT 103, and the upper electrode 104 is transferred and adhered to the zirconia substrate 108 having the penetrating pattern 201 formed from the front to the back by the above method. At the lower part of the zirconia substrate 108, the flow path substrate 20 having the liquid passage 203 is formed.
2 are adhered. Hereinafter, the operation of the liquid jet recording head will be described. The penetrating pattern 201 becomes a liquid chamber, which is filled with liquid. Lower electrode 102 and upper electrode 1
04, the diaphragm is moved to the liquid chamber 2.
When the liquid in the liquid chamber 201 is bent in a direction in which the volume of the liquid 01 decreases, the liquid in the liquid chamber 201 is ejected from the nozzle hole 204 to the outside through the liquid passage 203. Although not shown, the liquid passage 2
Reference numeral 03 is connected to the liquid storage chamber via a liquid supply hole 205 on the back side. When the application of the voltage to the diaphragm is stopped, the diaphragm returns to the original state, and the liquid flows from the liquid storage chamber (not shown) to the liquid supply hole 20 by capillary action.
5 and the liquid chamber 201 fills the liquid chamber 201.
By repeating the above operation, liquid ejection recording is performed.

In the above embodiment, the second substrate 10
After the diaphragm is bonded to the substrate 8, the substrate or sheet 105 is peeled off by irradiating a UV lamp to reduce the bonding strength of the bonding layer 106.
6 may be composed of a water-soluble adhesive, and the substrate or sheet 105 may be peeled off by dissolving in water. Alternatively, the substrate or sheet 105 may be dissolved by using a normal adhesive for the adhesive layer 106 in an organic solvent. The sheet 105 may be peeled off. In this way, the adhesive layer 106 is dissolved and the substrate or sheet 10 is melted.
By peeling off 5, the remaining adhesive layer on the diaphragm can be eliminated.

In the above embodiment, the lower electrode 1
In 02, the layer in contact with the intermediate layer on the single crystal silicon substrate 101 with the silicon oxide layer is made of platinum, but may be a noble metal such as iridium or ruthenium. For example, the configuration of the lower electrode 102 may be a three-layer configuration of iridium / platinum / titanium from the intermediate layer side, or a configuration of one ruthenium layer. Further, as a configuration of the lower electrode 102, an insulator layer may be inserted from the intermediate layer side, such as a five-layer configuration of platinum / zirconia / titanium / iridium / platinum / titanium. Further, the first substrate 101 is not limited to a single crystal silicon substrate provided with a silicon oxide layer, but may be made of another material such as quartz.

As the intermediate layer on the first substrate 101, a material such as chromium can be used in addition to the above-described titanium.

(Embodiment 2) FIG. 3 shows a piezoelectric / ferroelectric material according to a second embodiment of the present invention, in which a step of patterning a lower electrode is provided after a step of patterning an upper electrode and a piezoelectric / ferroelectric thin film. FIGS. 7A and 7B are cross-sectional views in the order of the device manufacturing process, in which FIG. 7A is at the time of completion of film formation of the upper electrode, and FIG.
FIG. 3C is a cross-sectional view at the time of completion of the lower electrode patterning step. In the figure, the same symbols as those in FIG. 1 represent the same as those in FIG.

First, an intermediate layer (not shown), a lower electrode 102, a piezoelectric / ferroelectric thin film 103, and an upper electrode 104 are formed in this order on the first substrate 101, and a sectional view shown in FIG. Then, the upper electrode 104 and the piezoelectric / ferroelectric thin film 103
Is performed using the same mask, and a sectional view shown in FIG. 3B is obtained. Further, patterning of the lower electrode 102 is performed to obtain a cross-sectional view shown in FIG. Then, as shown in (Example 1), the lower electrode 10 is formed using a method after the step of bonding a substrate or a sheet from the upper electrode 104 side.
2. When the structure formed by the piezoelectric / ferroelectric thin film 103 and the upper electrode 104 is transferred to the second substrate, the creation of the piezoelectric / ferroelectric thin film device is completed.

By patterning the lower electrode 102 after forming the piezoelectric / ferroelectric thin film as in this embodiment,
The lower electrode surface can be prevented from being contaminated when the piezoelectric / ferroelectric thin film is formed, and a device using the high-performance piezoelectric / ferroelectric thin film 103 can be formed.

(Embodiment 3) FIG. 4 is a cross-sectional view of a piezoelectric / ferroelectric thin-film element formed on a single-crystal ceramic substrate such as strontium titanate, sapphire, and magnesia. FIG. 4 is a diagram for explaining a case where a method for manufacturing a ferroelectric device is applied to a piezoelectric / ferroelectric thin film element formed on a single-crystal ceramic substrate such as strontium titanate, sapphire, and magnesia. In the figure, the same symbols as those in FIG. 1 represent the same as those in FIG.

Reference numeral 401 denotes the single crystal ceramic substrate, and reference numeral 402 denotes a platinum electrode layer. 403 is an oxide electrode layer of strontium ruthenate or the like. Between the single crystal ceramic substrate 401 and the platinum electrode layer 402, a titanium layer is inserted as an intermediate layer. From this state,
As shown in (Example 1) and (Example 2), the platinum electrode layer 402 and the oxide electrode layer 403 are formed by using a method after the step of bonding a substrate or a sheet from the upper electrode 104 side.
When the structure formed by the piezoelectric / ferroelectric thin film 103 and the upper electrode 104 is transferred to the second substrate, the fabrication of the piezoelectric / ferroelectric thin film device is completed.

An intermediate layer of a titanium layer (not shown), a platinum electrode layer 402, an oxide electrode layer 403 such as strontium ruthenate, etc.
By laminating the ferroelectric thin film 103, each layer can be grown epitaxially, and a higher performance piezoelectric / ferroelectric thin film 103 can be obtained. Therefore, a piezoelectric / ferroelectric thin film device formed by transferring the thin film onto the second substrate also has high performance. Usually, the ceramic substrate 401 such as strontium titanate used for epitaxial growth is quite expensive, but the element formed thereon is transferred to a second substrate, and the ceramic substrate 401 used as the first substrate is used. By recycling and using, it has become possible to manufacture high-performance piezoelectric / ferroelectric devices at low cost.

(Embodiment 4) FIG. 5 is a cross-sectional view of a ferroelectric memory manufactured by using the method for manufacturing a piezoelectric / ferroelectric device of the present invention. In FIG. 5, the same symbols as those in FIG. It represents the same thing as FIG. 501 is a single crystal silicon substrate,
502 is a source / drain region of a MOS transistor,
Reference numeral 503 denotes a gate insulating film of the MOS transistor, 504 denotes a gate electrode of the MOS transistor, 505 denotes a field oxide film, 506 denotes a first interlayer insulating film, 507 denotes a second interlayer insulating film, and 508 denotes a metal electrode for wiring.

First, a field oxide film 505, a gate insulating film 503, and a gate electrode 50 are formed on a single crystal silicon substrate 501.
4 and source / drain regions 502 are formed, and MOS
Create a transistor. Thereafter, the first interlayer insulating film 5
06 is formed. A ferroelectric thin film element including the lower electrode 102, the ferroelectric thin film 103, and the upper electrode 104 is formed thereon via the adhesive layer 107. The ferroelectric thin-film element is formed on another first substrate as in the above-described embodiment, and is replaced with a single-crystal silicon substrate 50 serving as a second substrate.
1 is transferred and formed on the field oxide film 505. As the ferroelectric thin film 103, PZT or SrBi ₂ Ta
₂ O ₉ or the like can be suitably used. Further, a second interlayer insulating film 507, a through hole, and a wiring metal electrode 50 are formed.
8 is formed to complete the ferroelectric memory.

The ferroelectric memory formed as described above
Since the process of forming the MOS transistor and the process of forming the ferroelectric thin film element can be performed separately, for example, the process for forming the ferroelectric thin film 103 which occurs during the manufacturing process of continuously forming them on the same substrate is performed. Diffusion of lead and other elements into the interlayer insulating film at the time of oxygen annealing and the effect of oxygen on the MOS transistor can be suppressed, resulting in excellent characteristics.

(Embodiment 5) FIG. 6 is a cross-sectional view of a pyroelectric infrared sensor manufactured using the method for manufacturing a piezoelectric / ferroelectric device of the present invention. In the figure, the same symbols as those in FIG. 1 represent the same as those in FIG. On a substrate 602 having a through pattern, a diaphragm portion 601 composed of a silicon dioxide layer or a silicon nitride layer or a multilayer film thereof via an adhesive layer 107, a lower electrode 102, a pyroelectric thin film 103, and an upper electrode A pyroelectric thin film element 102 is transferred and formed from another first substrate. Reference numeral 603 denotes a gold black layer, which serves as an infrared absorbing portion.

The pyroelectric infrared sensor having such a configuration is inexpensive because it is not necessary to use an expensive single crystal substrate for the substrate 602.

[0036]

As described above, by using the method for manufacturing a piezoelectric / ferroelectric device of the present invention, it is possible to peel off the structure from the first substrate without using a laser beam irradiation process. This makes it possible to use a non-translucent substrate such as single-crystal silicon as the substrate material, increasing the degree of freedom in selecting the substrate material, and eliminating damage to the structure due to laser light irradiation. We were able to. Further, the component can be separated from the first substrate without using a process of forming a separation layer, and a piezoelectric / ferroelectric thin film device with low cost and small characteristic variation has been realized.

[Brief description of the drawings]

FIG. 1 is a sectional view of a liquid jet recording head, which is a piezoelectric thin film device, according to an embodiment of the present invention in the order of manufacturing steps, and FIG. (B) is a view at the end of the step of bonding the substrate or sheet from the upper electrode side, and (c) is a view at the end of the step of peeling the substrate or sheet together with the diaphragm from the first substrate. (D) is a view at the end of the step of bonding the substrate or sheet and the diaphragm to the second substrate, and (e) is an end of the step of peeling the substrate or sheet from the second substrate and the diaphragm. It is sectional drawing at the time.

FIG. 2 is a perspective view of a liquid jet recording head, which is a piezoelectric thin film device formed using the manufacturing method of the present invention.

FIG. 3 is a cross-sectional view of a piezoelectric / ferroelectric device according to an embodiment of the present invention, in which a lower electrode is patterned after the upper electrode and the piezoelectric / ferroelectric thin film are patterned. FIG. 7A is a view when the upper electrode film formation is completed, FIG. 7B is a view when the patterning process of the upper electrode and the piezoelectric / ferroelectric thin film is completed, and FIG. It is sectional drawing at the time of the completion | finish of a process.

FIG. 4 is a cross-sectional view of a piezoelectric / ferroelectric thin film element formed on a single-crystal ceramic substrate such as strontium titanate, sapphire, and magnesia.

FIG. 5 is a cross-sectional view of a ferroelectric memory prepared using the method for manufacturing a piezoelectric / ferroelectric device according to the present invention.

FIG. 6 is a cross-sectional view of a pyroelectric infrared sensor manufactured using the method for manufacturing a piezoelectric / ferroelectric device of the present invention.

[Explanation of symbols]

 101 First substrate 102 Lower electrode 103 Piezoelectric / ferroelectric thin film 104 Upper electrode 105 Substrate or sheet 106 Adhesive layer 107 Adhesive layer 108 Second substrate

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01L 41/187 H01L 41/22 A 41/24

Claims (5)

[Claims] A step of forming an intermediate layer on a first substrate, a step of forming a lower electrode having at least one or more conductive layers on the intermediate layer, and a step of forming a piezoelectric element on the lower electrode.・
Forming a ferroelectric thin film, forming an upper electrode having at least one conductive layer on the piezoelectric / ferroelectric thin film, and forming the upper electrode and the piezoelectric / ferroelectric thin film on the piezoelectric / ferroelectric thin film. Patterning, bonding a substrate or sheet from the upper electrode side, and peeling the substrate or sheet from the first substrate together with the lower electrode and the piezoelectric / ferroelectric thin film and the upper electrode, Bonding the substrate or sheet, the lower electrode, the piezoelectric / ferroelectric thin film, and the upper electrode separated from the first substrate to the second substrate; and Weakening the adhesive strength of the adhesive layer between the dielectric thin film and the lower electrode, and separating the substrate or sheet from the second substrate, the lower electrode, the piezoelectric / ferroelectric thin film, and the upper electrode Method for manufacturing a piezoelectric-ferroelectric device characterized by having. 2. Dissolving an adhesive layer between the substrate or sheet and the upper electrode, the piezoelectric / ferroelectric thin film, and the lower electrode, thereby bonding the substrate or sheet to the second substrate, lower electrode, 2. The method for manufacturing a piezoelectric / ferroelectric device according to claim 1, further comprising peeling off the piezoelectric / ferroelectric thin film and the upper electrode. 3. A step of patterning the lower electrode before the step of forming the piezoelectric / ferroelectric thin film or after the step of patterning the upper electrode and the piezoelectric / ferroelectric thin film. The method for manufacturing a piezoelectric / ferroelectric device according to claim 1. 4. The first substrate is a single crystal silicon substrate with a silicon oxide layer, the intermediate layer is Ti or Cr, and the layer of the lower electrode which is in contact with the first substrate is a noble metal such as Pt, Ir, Ru or the like. The method for manufacturing a piezoelectric / ferroelectric device according to claim 1, wherein: 5. The piezoelectric / ferroelectric material according to claim 1, wherein the first substrate is a single crystal ceramic substrate made of strontium titanate, sapphire, magnesia, or the like. Device manufacturing method.