JP3493908B2 - Device using piezoelectric material, light condensing device, and method of manufacturing these devices - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a device using a piezoelectric body such as a piezoelectric actuator or a sensor, a light condensing device, and a method for manufacturing these devices.

[0002]

BACKGROUND ART PZT (Pb (Zr _1-x , Ti _x ) O ₃ ;
Piezoelectric materials such as lead zirconate titanate) have an amorphous phase and a pyrochlore phase and show almost no piezoelectricity before being heated. The piezoelectric material undergoes a phase transition to the perovskite phase when subjected to high-temperature heat treatment, and exhibits high piezoelectric properties. When the heating temperature is raised, the piezoelectric body becomes more piezoelectric.

A semiconductor manufacturing process is used to integrate a device (device) using such a piezoelectric element, including its electric circuit. In the semiconductor manufacturing process, a large number of devices are regularly arranged on one wafer. Each device includes elements that compose the device such as a piezoelectric body and a circuit element. Finally, the wafer is divided into individual devices by dicing. The above-described heat treatment of the piezoelectric body is performed on a wafer-by-wafer basis in the high-temperature oxygen atmosphere of the heating device, and thus has the following problems. (1) When the piezoelectric body is heated, other circuit elements etc. are also heated, so the electrical characteristics and circuit characteristics of the manufactured device change. (2) Since it is not possible to heat a plurality of piezoelectric bodies formed on a wafer at different temperatures, it is not possible to adjust the piezoelectric and mechanical characteristics of each individual device manufactured.

[0004]

DISCLOSURE OF THE INVENTION An object of the present invention is to make it possible to individually heat a large number of piezoelectric bodies formed on a wafer.

In the device using the piezoelectric body according to the present invention, a piezoelectric body which undergoes a phase transition from a mixed state of an amorphous phase and a pyrochlore phase to a perovskite phase by heating and an electrode for applying a voltage to the piezoelectric body are provided. It is formed on a substrate, and a heater for heating the piezoelectric body is formed near the piezoelectric body. Preferably, the heater is formed around the piezoelectric body.

By applying an electric current to the heater to heat the piezoelectric body, the piezoelectric body can be made to undergo a phase transition to the perovskite phase and have piezoelectric characteristics. By controlling the heating temperature, desired piezoelectric characteristics can be given. The piezoelectric characteristics can be made different for each individual piezoelectric body.

A method of manufacturing a device using a piezoelectric body according to the present invention comprises a piezoelectric body which undergoes a phase transition from a mixed state of an amorphous phase and a pyrochlore phase to a perovskite phase when heated, and a voltage for applying a voltage to the piezoelectric body. A plurality of sets of electrodes and electrodes are regularly formed on a semiconductor wafer, heaters are formed in the vicinity of the plurality of piezoelectric bodies, and the piezoelectric bodies are heated by the heaters and then divided into individual devices. Is.

A large number of piezoelectric bodies are formed on a semiconductor wafer, and heaters for heating the respective piezoelectric bodies are provided in the vicinity thereof. Since only the piezoelectric body is heated instead of heating the entire wafer at a constant temperature, other circuit elements on the wafer are hardly affected by the heat treatment.

Further, since the heating treatment of the piezoelectric body is performed individually, it is possible to change the heating temperature of the piezoelectric body, and it is possible to manufacture devices having different piezoelectric characteristics.

Furthermore, since the piezoelectric body can be heat-treated without using a heating device, the manufacturing cost can be suppressed. Further, when the piezoelectric body is small, it can be heated rapidly, so that the heat treatment efficiency is good.

Preferably, the heater is formed between the substrate and the piezoelectric body.

Since the heater is formed immediately below the piezoelectric body,
The influence of heat on other circuit elements formed on the wafer is further reduced. Further, since a space for forming the heater is not required separately, it is possible to effectively utilize the substrate surface.

More preferably, the piezoelectric body is made of PZT, the electrode is made of platinum, titanium, or an alloy of platinum and titanium, and the heater is made of single crystal silicon or polycrystalline silicon.

The light collecting device according to the present invention comprises a semiconductor substrate having an elastically deformable diaphragm portion and a support portion for supporting the diaphragm portion, a transparent substrate joined to the support portion of the semiconductor substrate, An insulating layer formed on one surface of a semiconductor substrate, a piezoelectric body formed at a position corresponding to the diaphragm section on the insulating layer, which undergoes a phase transition from a mixed state of an amorphous phase and a pyrochlore phase to a perovskite phase by heating. An actuator composed of an electrode for applying a voltage to the piezoelectric body, a heater for heating the piezoelectric body formed in the vicinity of the piezoelectric body on the insulating film, the diaphragm on the transparent substrate A light emitting element provided at a position corresponding to the light emitting element, and a light emitting element formed on a surface of the diaphragm portion facing the light emitting element. Mirror for reflecting the light emitted from,
In addition, it is provided with an optical element formed on the transparent substrate to form an image of the reflected light.

Light emitted from the light emitting element is reflected by the mirror surface formed on the diaphragm portion and is condensed by the optical element.
The diaphragm portion is deformed by applying a voltage to the electrodes sandwiching the piezoelectric body, so that the focus position of the light emitted from the light emitting element changes. According to this condensing device, since the spot position of the projected light can be changed, it can be used for display, detection of various physical quantities, and other purposes.

[0016]

【Example】

First Embodiment FIG. 1 is a perspective view showing a condenser, and FIG. 2 is a sectional view taken along line II-II of FIG. In these drawings, the wall thickness is emphasized for convenience of drawing and for easy understanding. This also applies to the drawings showing other embodiments described later.

This condensing device is a compact disc
It is used in various optical devices such as players and auto-focus cameras, and is capable of arbitrarily changing the condensing position of emitted light.

The light collecting device 1 is formed by anodic bonding a light transmitting glass substrate 10 to the lower surface of a silicon semiconductor substrate 20.

The silicon semiconductor substrate 20 is provided with a truncated pyramid-shaped recess 22 from the back side thereof, and the bottom surface of the recess 22 is a thin diaphragm portion 24 which is elastically deformable. The recess 22 is preferably formed by anisotropically etching the lower surface of the silicon semiconductor substrate 10 using an alkaline etching solution. The lower surface of the diaphragm portion 24 (the surface facing the glass substrate 10) is mirror-finished to give a mirror surface 26.
Has become. The shape of the recess 22 is not limited to the truncated pyramid shape, and may be, for example, a truncated cone shape.

An insulating film 28 is provided on almost the entire upper surface of the silicon semiconductor substrate 10. The insulating film 28 is for electrically insulating the silicon semiconductor substrate 10 from the lower electrode 32, the heater 38, and the processing circuit described later. Insulation film 28
Is preferably a silicon thermal oxide film or LPCVD
(Low Pressure Chemical Vapor Deposition) A nitride film.

An actuator 30 is formed on the upper surface of the insulating film 28 at a position corresponding to the diaphragm portion 24. The actuator 30 includes a piezoelectric layer 34 as an upper electrode 36 and a lower electrode.
It is sandwiched between 32. The piezoelectric layer 34 generates lateral strain in a direction perpendicular to the applied electric field. The piezoelectric layer 34 is preferably made of a material that is highly deformable even in a weak electric field.
Most preferably, this material has a large piezoelectric constant and is excellent in thin film formation and microfabrication, and PZT (Pb (Zr _1-X , Ti
_X ) O ₃ ; lead zirconate titanate). Upper electrode 36
And the lower electrode 32 is preferably formed of platinum, titanium, or an alloy of platinum and titanium. On the upper surface of the insulating film 28, from the electrodes 32 and 36 to the electrode pads 32a and 36a
Is extended. A voltage is applied between the electrodes 32 and 36 via the electrode pads 32a and 36a.

On the upper surface of the insulating film 28, the actuator
A frame-shaped heater 38 is formed so as to surround 30. Two electrode pads 38a extend from the periphery of the heater 38. When a current is applied to the heater 38 through the two electrode pads 38a, the heater 38 generates heat and the piezoelectric layer of the actuator 30 is heated.
Heat 34. The heater 38 is preferably formed of single crystal silicon or polycrystalline silicon.

The piezoelectric layer 34 has an amorphous phase and a pyrochlore phase mixed therein, and exhibits almost no piezoelectricity before being heated. When heated (preferably about 600 to 800 ° C.) by the heater 38 described above, the piezoelectric layer 34 undergoes a phase transition to the perovskite phase and exhibits a large piezoelectric property. When the heating temperature is increased, the piezoelectric layer 34 becomes more piezoelectric. Therefore, by adjusting the heating temperature by the heater 38, the piezoelectric characteristics of the light condensing device 1 can be arbitrarily set. That is, it is possible to have different piezoelectric characteristics in each of the light collecting devices 1.

When a voltage is applied to the piezoelectric layer 34, lateral strain occurs in the piezoelectric layer 34. The piezoelectric layer 34 is curved as shown by the chain line in FIG. 2, and accordingly, the diaphragm portion 24 and the mirror surface are curved.
26 is displaced. When the voltage value applied between the electrodes 32 and 36 is changed, the displacement amount of the diaphragm portion 24 is also changed.

A circuit element for controlling the voltage value applied to the piezoelectric layer 34 is formed at a position (region surrounded by a chain line in FIG. 1) 42 on the upper surface of the insulating film 28 away from the heater 38. .
Since the circuit element is formed at a position distant from the heater 38, the circuit element is also heated when the piezoelectric layer 34 is heated, and the electrical characteristics and circuit characteristics of the light-collecting device 1 to be manufactured change. Such a problem is solved.

A diffractive imaging element 12 such as a Fresnel lens is provided on the lower surface of the glass substrate 10. Imaging element 12
Collects or collimates the light beam. Imaging element 12
Is a glass substrate made of resin, preferably using a stamper
It is formed on the surface of 10 and the resin is photopolymerized.
zation) method to solidify.

A light emitting element 14 is provided on the upper surface of the glass substrate 10 at a position facing the mirror surface 26 with the optical axis aligned with that of the imaging element 12. The light emitting element 14 is preferably a surface emitting light emitting diode or a semiconductor laser. Since the image forming element 12 and the light emitting element 14 are previously provided on one glass substrate 10, the optical axis can be easily adjusted.

A light beam is emitted from the light emitting element 14 toward the mirror surface 26 in a state where a voltage is not applied to the actuator 30 (a state in which the diaphragm portion 24 is not displaced).
As shown by the solid line in FIG.
Is reflected by the mirror surface 26 above. The reflected light from the mirror surface 26 passes through the glass substrate 10 and is condensed by the image forming element 12 to form a spot SP ₁ .

When a voltage is applied to the actuator 30, lateral strain is generated in the piezoelectric layer 34 and the piezoelectric layer 34 bends. Along with this, the diaphragm portion 24 and the mirror portion 26 are displaced or curved in the vertical direction. The light beam emitted from the light emitting element 14 is shown in FIG.
Is reflected by the mirror surface 26 as indicated by the chain line in FIG.
Due to this, the light is condensed at a position closer to the condensing device than the spot SP ₁ , and a spot SP ₂ is formed. When the voltage value applied to the piezoelectric layer 34 is increased, the displacement amount or the degree of bending of the diaphragm portion 24 is further increased (the distance between the mirror surface 26 and the light emitting element 14 is increased). In this way, by displacing or bending the mirror surface 26 formed on the diaphragm portion 24, the condensing position of the light beam can be changed.

It is also possible to replace the light emitting element 14 of the above-described light converging device 1 with a light receiving element such as a photo diode, a photo transistor, a CCD or the like to form a light receiving device. The light beam incident on the glass substrate 10 is collected by the imaging element 12, reflected by the mirror surface 26, and then received by the light receiving element.

Second Embodiment FIG. 3 is a perspective view corresponding to FIG. 1 showing a second embodiment.
The same parts as those shown in FIG. 1 are designated by the same reference numerals to avoid redundant description. Description will be given focusing on the points different from the above-described first embodiment.

A heater 38 for heating the piezoelectric layer 34 is formed on almost the entire surface of the upper surface of the insulating film 28 corresponding to the diaphragm portion 24. An insulating film for electrically insulating the heater 38 and the lower electrode 36 is formed on the upper surface of the heater 38.
40 are formed. An actuator 30 including a piezoelectric layer 34, an upper electrode 36 and a lower electrode 32 is provided on the insulating film 40.

Since the heater 38 is formed on the entire surface immediately below the piezoelectric layer 34 and directly heats the piezoelectric layer 34, the heating efficiency is improved and the influence of heat applied to other circuit elements can be reduced. . Further, since the heater 38 is not formed around the piezoelectric layer 34, the area for forming the circuit element is correspondingly formed.
42 can be taken widely.

FIGS. 4 to 8 are views showing a processing process of a semiconductor wafer to be the semiconductor substrate 20 in the second embodiment.
It is a perspective view corresponding to. In these figures, only a portion of the semiconductor wafer corresponding to one light collecting device is shown.

First, an insulating film 28 such as a thermal oxide film or LPCVD nitride film is formed on the upper surface of the semiconductor wafer 20a (FIG. 4).

A heater made of single crystal or polycrystalline silicon is provided at a position corresponding to the diaphragm portion 24 on the upper surface of the insulating film 28.
38 is formed (FIG. 5).

An insulating film 40 is formed on the upper surface of the heater 20 (FIG. 6).

A lower electrode 32 made of platinum, titanium, or an alloy of platinum and titanium is formed on the upper surface of the insulating film 40 (FIG. 7).

A PZT piezoelectric layer 34 is formed on the upper surface of the lower electrode 24 (FIG. 8).

An upper electrode 36 is formed on the upper surface of the PZT piezoelectric layer 34. Region 42 on insulating film 28 away from actuator 30
At this point, a circuit element for controlling the voltage value applied to the PZT piezoelectric layer 34 is formed (see FIG. 3). Then, anisotropic etching is performed from the lower surface of the silicon semiconductor wafer 20a to form a truncated pyramid-shaped recess 22 (see FIG. 2).

After all the elements are formed on the semiconductor wafer 20a, the PZT piezoelectric layer 34 is heat-treated. The PZT piezoelectric layer 34 is heated by applying a voltage to the heater 38 via the two electrode pads 38a. The PZT piezoelectric layer 34, in which the amorphous phase and the pyrochlore phase are mixed, undergoes a phase transition to the perovskite phase, and the PZT piezoelectric layer 34 exhibits high piezoelectricity.

On the lower surface of the semiconductor wafer 20a, an insulator wafer (glass substrate) on which a plurality of sets of image forming elements 12 and light emitting elements 14 are formed is anodically bonded. It is possible to obtain one in which a large number of light collectors 1 are regularly arranged in one wafer composed of the semiconductor wafer 20a and the insulator wafer which are bonded to each other. When this wafer is divided by dicing, a large number of light collectors 1 as shown in FIG. 3 are completed.

Since the entire semiconductor wafer 20A can be heated at a desired temperature for each piezoelectric layer 34 instead of being heated at a constant temperature, the piezoelectric characteristics can be changed for each light-collecting device 1 to be manufactured. You can As a result, it is possible to manufacture a plurality of light collectors 1 having different piezoelectric characteristics.

Third Embodiment FIG. 9 is a conceptual diagram showing an example in which the above-mentioned light collecting device 1 is applied to a display device.

The display device comprises a light source 50 in which a large number of light-collecting devices 1 having light emitting elements 14 are regularly arranged, and a display screen on which a plurality of light beams emitted from the light source 50 are projected. It consists of 52 and. By changing the condensing position of the light beam emitted from each condensing device 1,
The size of the spot SP of the light beam projected on the display screen 52 can be variously changed. Therefore, the spot diameter of the display beam can be controlled in addition to turning on / off each condensing device 1, and various displays can be performed.

[Brief description of drawings]

FIG. 1 is a perspective view showing a light collecting device.

FIG. 2 is a sectional view taken along line II-II in FIG.

FIG. 3 is a perspective view corresponding to FIG. 1 showing a second embodiment.

FIG. 4 is a perspective view corresponding to FIG. 3, showing a process of processing a semiconductor wafer to be a semiconductor substrate.

FIG. 5 is a perspective view corresponding to FIG. 3 showing a process of processing a semiconductor wafer to be a semiconductor substrate.

FIG. 6 is a perspective view corresponding to FIG. 3 showing a process of processing a semiconductor wafer to be a semiconductor substrate.

FIG. 7 is a perspective view corresponding to FIG. 3 showing a processing process of a semiconductor wafer to be a semiconductor substrate.

FIG. 8 is a perspective view corresponding to FIG. 3 showing a process of processing a semiconductor wafer to be a semiconductor substrate.

FIG. 9 is a conceptual diagram showing an example in which a light collecting device is applied to a display device.

[Explanation of symbols]

10 glass substrate 20 Silicon semiconductor substrate 24 Diaphragm section 26 Mirror surface 28 Insulating film 30 actuator 32 Lower electrode 34 PZT piezoelectric layer 36 Upper electrode 38 heater

─────────────────────────────────────────────────── ─── Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) G02B 26/08 H01L 41/09 H01L 41/22

Claims (6)

(57) [Claims] 1. A piezoelectric body that undergoes a phase transition from a mixed state of an amorphous phase and a pyrochlore phase to a perovskite phase when heated and an electrode for applying a voltage to the piezoelectric body are formed on a substrate, and the piezoelectric body is formed. A device using a piezoelectric body, in which a heater for heating the piezoelectric body is formed in the vicinity of. 2. The device using the piezoelectric body according to claim 1, wherein the heater is formed around the piezoelectric body. 3. The device using the piezoelectric body according to claim 1, wherein the heater is formed between the substrate and the piezoelectric body. 4. The device using the piezoelectric body according to claim 1, wherein the heater is formed of single crystal silicon or polycrystalline silicon. 5. A semiconductor substrate having an elastically deformable diaphragm portion and a support portion for supporting the diaphragm portion, a transparent substrate bonded to the support portion of the semiconductor substrate, and formed on one surface of the semiconductor substrate. Insulating layer,
A piezoelectric body, which is formed at a position corresponding to the diaphragm section on the insulating layer and which undergoes a phase transition from a mixed state of an amorphous phase and a pyrochlore phase to a perovskite phase by heating, and a voltage for applying a voltage to the piezoelectric body An actuator composed of an electrode, a heater for heating the piezoelectric body formed in the vicinity of the piezoelectric body on the insulating film, and a light emitting element provided at a position corresponding to the diaphragm section on the transparent substrate. A mirror provided on a surface of the diaphragm portion facing the light emitting element, the mirror reflecting the light emitted from the light emitting element, and the optical element formed on the transparent substrate for forming an image of the reflected light. Light equipment. 6. A plurality of sets of a piezoelectric body on which a phase transition occurs from a mixed state of an amorphous phase and a pyrochlore phase to a perovskite phase by heating and electrodes for applying a voltage to the piezoelectric body on a semiconductor wafer in a regular manner. A method of manufacturing a device using a piezoelectric body, wherein a heater is formed near each of the plurality of piezoelectric bodies, the heater is used to heat the piezoelectric body, and the heater is divided into individual devices.