KR20000044806A - Actuator of thin film micromirror array-actuated device - Google Patents

Abstract

PURPOSE: An actuator TMA device is provided to prevent the weakness of the electroplasive itself and to maximize the driving of the actuator by the electric signal by forming the electroplasive with PNZT layer or PbTiO3 layer. CONSTITUTION: A device comprises a driving substrate(5), a membrane(30), a lower electrode layer(35), an electrodisplasive(40), an upper electrode(45), a driving mirror(60), and an actuator(65). A plurality of transistors are installed inside the driving substrate and the protection layer is located on the upper part of the driving substrate in order to prevent the transistor from being destroyed. The driving mirror is supported by the post(75) which is formed at the end central part of the membrane. An image signal voltage is applied on the lower electrode and the bias voltage is applied on the upper electrode which is common electrode. A manufacturing method comprises a step of forming an PbTiO3 layer with a thickness of 500-1000 angstrom which has good combining characteristic with Pb even under high temperature on the electroplasive.

Description

Actuator of thin film type optical path controller

The present invention relates to an actuator of a thin film micromirror array-actuated, and more particularly, to a thin film type optical path control device capable of preventing a deterioration of a property of a strain layer by a high temperature process for crystallizing the strain layer. It relates to an actuator.

In general, a display device capable of forming an image by adjusting a light flux has a direct view type image display device such as a CRT (Cathod Ray Tube) or a projection type image display device according to a method of projecting a light beam incident from a light source on a screen. And a liquid crystal display (DMD), a deformable mirror device (DMD), and a thin film micromirror array-actuated (TMA).

Although CRT devices have excellent image quality, as the screen size increases, the weight and volume of the device increase, and the manufacturing cost thereof increases. In contrast, a liquid crystal display (LCD) can be formed of a flat plate, but the incident light flux Due to the polarization of the light having a low light efficiency of 1 to 2%, there was a disadvantage that the response speed of the liquid crystal material therein is slow.

In order to solve the problems of the LCD, a display device such as a DMD or a TMA has been developed. At present, TMA can achieve a light efficiency of 10% or more, compared to a DMD having a light efficiency of about 5%. In addition, the TMA is not only affected by the polarity of the incident light beam, but also does not affect the polarity of the light beam.

Typically, each of the actuators formed inside the TMA causes deformation depending on the electric field generated by the applied image signal and bias voltage. When this actuator causes deformation, each of the mirrors mounted on top of the actuator is inclined in proportion to the magnitude of the electric field.

Thus, the inclined mirrors can reflect light incident from the light source at a predetermined angle.

1 is a cross-sectional view showing an example of a conventional thin film type optical path control device, Figure 2 is a cross-sectional view taken along the line A-A of FIG.

As shown in the drawing, the conventional thin film type optical path control device includes a driving substrate 5, an actuator 65 formed on the upper portion thereof, and a driving mirror 60 formed on the actuator 65.

The actuator 65 described above includes a membrane 30, a lower electrode 35, a strained layer 40, and an upper electrode 45. For example, the materials constituting the actuator 65 may be formed of silicon nitride (Si ₃ N). ₄ ) TaO / Pt / PNZT (Nb1%) / LSCO / Pt on the layer. The silicon nitride layer serves as a membrane 30, and the lower electrode 35 and the upper electrode 45 are made of platinum (Pt) material, and the strained layer 40 is formed of niobium (Pb (ZrTi) O ₃ ). Nb) is made of a PNZT material is added a small amount, between the membrane 30 and the lower electrode 35 is interposed tantalum oxide (TaO) to increase the adhesion, LSCO to help the crystallization of the strained layer 40 LaSrCoO ₃ is interposed between the strained layer 40 and the upper electrode 45.

In addition, the actuator 65 includes a via contact 55 electrically connecting the drain pad (not shown) of the driving substrate 5 to the lower electrode 35.

The driving mirror 60 is supported by the center of the post 75 formed in the center of the end of the membrane 30.

In the conventional thin film type optical path control apparatus, an image signal voltage is applied to the lower electrode 35, which is a signal electrode, and when a bias voltage is applied to the upper electrode 45, which is a common electrode, the upper electrode 45 and the lower electrode 35. An electric field is generated between them. The deformed layer 40 between the upper electrode 45 and the lower electrode 35 causes deformation by the electric field, and the deformed layer 40 contracts in a direction perpendicular to the electric field. Accordingly, the actuator 65 including the deformable layer 40 is bent at a predetermined angle, and the driving mirror 60 mounted on the driving tip of the actuator 65 is inclined by the bent membrane 30 to be incident from the light source. Reflect the light beam. The light beam reflected by the driving mirror 60 is projected onto the screen through the slit of the TMA optical system. Such a thin film type optical path control device forms a unit pixel to form an image by forming a TMA module arranged in an M × N (M, N is an integer) matrix structure.

In particular, in the conventional thin film type optical path control device, the deformable layer 40 of the PNZT material is subjected to sol-gel coating several times and dried for each coating to deposit 4000 NZ of PNZT as a whole. Finally, RTA heat treatment was performed at 650 ° C. for 100 seconds to crystallize PNZT.

However, the deformation layer 40 of the conventional thin film type optical path control device has the following problems.

When the PNZT layer is heat-treated at 650 ° C before depositing the LSCO, lead (Pb) component oxidizes inside the PNZT, and lead oxide (PbO) is generated. Such lead oxide is released from the surface of the PNZT layer. Voids are formed on the surface of the substrate.

That is, since the stability of Pb-Zr inside the PNZT is low, the Pb-Zr bond is broken on the surface of the PNZT deposited by the sol-gel coating method, so that a large amount of Pb escapes through the surface.

And inside PNZT, some PbO is detected by X-ray diffraction. This phenomenon is diffused and accelerated throughout the thin film by fast Pb loss on the surface.

As a result, a variation in density and a variation in composition occur in the strained layer 40. This phenomenon causes a problem that adversely affects the driving characteristics of the actuator 65.

Accordingly, the present invention is to solve such a conventional problem, and when the strained layer is RTA heat-treated, the components constituting the strained layer cause an oxidation reaction, thereby suppressing the generation of empty spaces from the surface of the strained layer. It is an object of the present invention to provide an actuator of a thin film type optical path control device capable of doing so.

In order to achieve the above object, the present invention provides a thin film type optical path having a driving substrate, an actuator including a first sacrificial layer, a membrane, a lower electrode, a deformation layer, and an upper electrode on the driving substrate, and a driving mirror supported at the end of the actuator. In the regulating device, the actuator of the thin film type optical path control device comprising a lead titanate (PbTiO ₃ ) layer having a strong bonding force with lead (Pb) at a high temperature on the strained layer is formed to a thickness of 500 ~ 1000Å.

The above objects and various advantages of the present invention will become more apparent from the preferred embodiments of the invention described below with reference to the accompanying drawings by those skilled in the art.

1 is a plan view of a conventional thin film type optical path control device,

FIG. 2 is a cross-sectional view taken along line AA ′ of FIG. 1;

3 is a cross-sectional view of a thin film type optical path control apparatus according to the present invention.

<Explanation of symbols for the main parts of the drawings>

5; Drive substrate 30; Membrane

35; Lower electrode 40; Strained layer

41; PNZT (Nb 1%) 42; Lead titanate (PbTiO ₃ ) layer

45; Upper electrode 55; Via Contact

60; Driving mirror 65; Actuator

Hereinafter, with reference to the accompanying drawings will be described in detail a manufacturing method of a thin film type optical path control apparatus according to the present invention.

3 is a cross-sectional view showing a thin film type optical path control apparatus according to the present invention.

As shown, the thin film type optical path control device according to the present invention is composed of a driving substrate 5, an actuator 65 formed on the upper portion and a driving mirror 60 formed on the actuator 65.

Although not shown in the drawing inside the driving substrate 5, M × N transistors are built-in, and an silicate glass is formed on the driving substrate 5 to prevent damage to the transistors embedded in the driving substrate 5. A protective layer 15 made of (PSG) material is provided.

The actuator 65 is composed of TaO / Pt / PNZT (Nb1%) / PbTiO ₃ / LSCO / Pt on the membrane 30 of silicon nitride (Si ₃ N ₄ ) material. The lower electrode 35 and the upper electrode 45 are made of platinum (Pt), and the strained layer 40 is formed of lead titanate (Pb) on a PNZT material in which niobium (Nb) is added to (Pb (ZrTi) O ₃ ). PbTiO ₃ ) PNZT (Nb 1%) / PbTiO ₃ is formed of a two-layer structure, between the membrane 30 and the lower electrode 35 is interposed tantalum oxide (TaO; 31) to increase the adhesive force, deformation LSCO (LaSrCoO ₃ ), which assists in crystallization of the layer 40, is interposed between the strained layer 40 and the upper electrode 45.

In particular, the PNZT layer 41 constituting the strained layer 40 is subjected to sol-gel coating several times, dried for each coating, and deposited as a total thickness of 4000 kPa.

In addition, the lead titanate (PbTiO ₃ ) layer 42 according to the characteristic configuration of the present invention has a strong bonding force with lead (Pb) even at high temperature, and even after RNZ heat treatment after applying the PNZT layer 41, the evaporation of lead (Pb) The lead titanate (PbTiO ₃ ) layer 42 is preferably formed on the PNZT layer 41 to a thickness of 500 to 1000 GPa.

That is PNZT layer 41, even if the stability of a Pb-Zr on the inner lead titanate (PbTiO _3), layer 42 increases the stability of the inside of the Pb-Ti on the surface of lead titanate (PbTiO ₃₎ layer 42 is much Positive lead (Pb) will not escape through the surface.

In this way, even after the lead titanate layer 42 is deposited and the PNZT layer 41 is crystallized by RTA heat treatment, the lead (Pb) component inside the PNZT layer 41 does not escape, so that the empty space is in the PNZT layer 41. The formation of voids is greatly reduced or suppressed.

As a result, the stability of the density and the uniformity of the composition inside the strained layer 40 are increased, thereby improving the characteristics of the strained layer 40.

In addition, the actuator 65 includes a via contact 55 electrically connecting the drain pad (not shown) of the driving substrate 5 to the lower electrode 35.

In addition, the central portion of the driving mirror 60 is supported by a post 75 formed in the center of the end of the membrane 30.

In the film type optical path control device as described above, an image signal voltage is applied to the lower electrode 35, which is a signal electrode, and a bias voltage is applied to the upper electrode 45, which is a common electrode, between the upper electrode 45 and the lower electrode 35. An electric field will be generated. The deformed layer 40 between the upper electrode 45 and the lower electrode 35 causes deformation by the electric field, and the deformed layer 40 contracts in a direction perpendicular to the electric field. Accordingly, the actuator 65 including the deformable layer 40 is bent at a predetermined angle, and the driving mirror 60 mounted on the driving tip of the actuator 65 is inclined by the bent membrane 30 to be incident from the light source. Reflect the light beam. The light beam reflected by the driving mirror 60 is projected onto the screen through the slit of the TMA optical system. Such a thin film type optical path control device forms a unit pixel to form an image by forming a TMA module arranged in an M × N (M, N is an integer) matrix structure.

In the above description, it should be understood that those skilled in the art can make modifications and changes to the present invention without changing the gist of the present invention as merely illustrative of a preferred embodiment of the present invention.

As described above, according to the present invention, since the strained layer is composed of a PNZT layer and a lead titanate (PbTiO ₃ ) layer, the piezoelectric coefficient value of the piezoelectric material is less decreased by a high temperature process for crystallizing the PNZT layer. It is possible to maximize the drive of the actuator by the signal, and to prevent the weakening of the deformation layer itself due to frequent driving.

Claims (1)

In the thin film type optical path control apparatus having a driving substrate, an actuator comprising a first sacrificial layer, a membrane, a lower electrode, a deformation layer and an upper electrode on the driving substrate and a driving mirror supported at the end of the actuator, Actuator of the thin film type optical path control device comprising a lead titanate (PbTiO ₃ ) layer having a strong bonding force with lead (Pb) at a high temperature on the strained layer is formed to a thickness of 500 ~ 1000Å.