KR20000044831A - Manufacturing method for thin film micromirror array-actuated device - Google Patents

Abstract

PURPOSE: A manufacturing method for a TMA device is provided to improve the function and reliability of the product by preventing the remaining images from occurring due to the lassitude of the electrodisplacive. CONSTITUTION: A device comprises a driving substrate(5), a first sacrificial layer(25), a membrane(30), a lower electrode(35), an electrodisplacive(40), an upper electrode(45), a side of a mirror(60), an actuator(65), a second sacrificial layer(70), and a post(75). A manufacturing method comprises a step of forming a driving substrate; a step of patterning after forming the first sacrificial layer on the driving substrate; a step of forming a membrane by depositing the nitration material on the exposed driving substrate; a step of forming the lower electrode; a step of forming the electroplasive by depositing the PZT on the upper part of the lower electrode; a step of forming the upper electrode by depositing conductive material; a step of forming the second sacrificial layer; and a step of forming the a side if mirror after forming the post.

Description

Manufacturing method of thin film type optical path control device

The present invention relates to a method for manufacturing a thin film micro mirror array actuated, and more particularly, to a thin film type optical path suitable for preventing an afterimage due to oxygen depletion of the piezoelectric material constituting the deformation layer. It relates to a manufacturing method of the adjusting device.

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. A liquid crystal display (hereinafter referred to as an LCD), a deformable mirror device (DMD), or 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, these inclined mirrors can reflect light incident from the light source at a predetermined angle. Piezoelectric ceramics such as PZT (Pb (Zr, Ti) O ₃ ), or PLZT ((Pb, La) (Zr, Ti) O ₃ ) are used as a constituent material of the actuator for driving the respective mirrors. As the constituent material of this actuator, electrodistorted ceramics such as PMN (Pb (Mg, Nb) O ₃ ) can be used.

1 is a plan view illustrating an example of a general thin film type optical path control device, and FIG. 2 is a cross-sectional view taken along line AA ′ of FIG. 1.

As shown, FIG. 1 is a two-layer thin film type optical path adjusting device which is an example of a previously applied thin film type optical path adjusting device, which is formed on the driving substrate 5 and the actuator 65 and the actuator 65 formed thereon. It has a two-layer structure consisting of a mirror surface (60).

The above-described actuator 65 includes a membrane 30, a lower electrode 35, a strained layer 40, and an upper electrode 45, and a drain pad (not shown) and a lower electrode (not shown) of the driving substrate 5. And a via contact 55 that electrically connects 35.

The above-described mirror surface 60 is supported at its center by a post 75 formed at 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 mirror surface 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 mirror surface 60 is projected onto the screen through the slit of the TMA optical system. Such a two-layer thin film type optical path control apparatus forms a unit pixel to form an image by forming a TMA module arranged in a matrix structure of M × N (M and N are integers).

On the other hand, in the conventional formation of the strained layer 40 of such a thin film type optical path control device, PZT (Pb (Zr, Ti) O ₃ ) by the sol-gel method (Sol-Gel) the upper portion of the lower electrode 35 PZT was determined by thermal thermal treatment (RTA: Rapid Thermal Annealing) at about 400 ° C., and then removing organic matter on the surface of the coating film (ie, strained layer) using a conventional dry method at about 400 ° C. Deform the structure.

However, Pb contained in PZT is evaporated when it is 400 ° C. or higher. In the thermal process for modifying the crystal structure of PZT, Pb forms PbO together with oxygen contained in PZT. Evaporates. As a result, oxygen depletion occurs at the interface of the PZT, and such oxygen depletion lowers the piezoelectric characteristics of the PZT, thereby lowering the drive characteristics of the actuator. That is, afterimages occur on the screen.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and provides a method for manufacturing a thin film type optical path control apparatus which can prevent afterimages caused by oxygen depletion by increasing the oxygen content in PZT. Its purpose is to.

In order to achieve the above object, the present invention includes a first sacrificial layer, a membrane, a lower electrode, a strained layer, and an upper electrode on an upper portion of a driving substrate having a transistor array of M × N (M, N is an integer). In the method of manufacturing a thin film type optical path control device by removing the first sacrificial layer after forming an actuator to the pixel unit, the lower electrode is formed of La _0.5 Sr _0.5 CoO _3-x Provided is a method for manufacturing a thin film type optical path control device.

A first step of applying PZT (Pb (Zr, Ti) O ₃ ) to the strained layer; Drying the coated PZT film; And it provides a method of manufacturing a thin film type optical path control apparatus, characterized in that by repeatedly forming a plurality of ozone dipping to increase the content of the PZT film.

1 is a plan view showing an example of a general thin film type optical path control device,

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

Figure 3a to 3g is a manufacturing process diagram of a two-layer thin film type optical path control device according to a preferred embodiment of the present invention.

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

5; Drive substrate 25; First sacrificial layer

30; Membrane 35; Bottom electrode

40; Strained layer 45; Upper electrode

55; Via contact 60; Mirror surface

65; Actuator 70; Second sacrificial layer

75; Post

Hereinafter, with reference to the accompanying Figure 3 will be described in detail a manufacturing method of a thin film type optical path control apparatus according to the present invention.

The core technical idea of the present invention is to form the lower electrode as La _0.5 Sr _0.5 CoO _3-x during the formation of the strained layer, whereby lead (Pb) in the PZT forming the strained layer during the thermal process is evaporated in the form of PbO, This is to prevent the occurrence of afterimages due to increased fatigue, which will be described with emphasis.

3A to 3G are cross-sectional views illustrating a method of manufacturing a two-layer thin film type optical path control device according to a preferred embodiment of the present invention.

Referring to FIG. 3A, a driving substrate 5 having M × N transistors embedded therein and a drain pad (not shown) formed on one side thereof is prepared. A protective layer 15 made of in-silicate glass (PSG) material is formed thereon to prevent damage to the transistor embedded in the driving substrate 5 during the subsequent process.

An etch stop layer 20 made of nitride is formed on the passivation layer 15. The etch stop layer 20 prevents the driving substrate 5 and the protective layer 15 from being damaged by an etch process that proceeds to a subsequent process.

Referring to FIG. 3B, the first sacrificial layer 25 is formed on the driving substrate 5 on which the protective layer 15 and the etch stop layer 20 are formed. The first sacrificial layer 25 is formed of phosphorous silicate glass (PSG) or polysilicon by low pressure chemical vapor deposition (LPCVD).

Since the actuator 65 is formed on the first sacrificial layer 25, it is necessary to maintain a flat state. The surface of the first sacrificial layer 25 formed on the driving substrate 5 in which the transistor is embedded has very poor flatness. . Therefore, the surface of the first sacrificial layer 25 is planarized through a chemical mechanical polishing (CMP) process.

The first sacrificial layer 25 is patterned to expose one end of the etch stop layer 20 positioned above the drain pad (not shown) to form the support region of the actuator 65.

Referring to FIG. 3C, the membrane 30 is formed by depositing nitride on top of the first sacrificial layer 25 including the support region using physical or chemical vapor deposition.

The lower electrode 35 is formed by stacking La _0.5 Sr _0.5 CoO _3-x on the membrane 30 using a method such as sputtering in an oxygen plasma (O ₂ plasma) state. At this time, unlike the conventional lower electrode is formed of a metal such as platinum (Pt) in the present invention by forming La _0.5 Sr _0.5 CoO _3-x , lead in the PZT film forming the strained layer 40 during the subsequent thermal process ( When Pb is evaporated in the form of PbO, oxygen depletion in the PZT film forming the strained layer 40 is supplied by supplying the coral of La _0.5 Sr _0.5 CoO _3-x forming the lower electrode to the strained layer 40. ) Can be prevented from occurring, and in this case, by forming the lower electrode 35 in an oxygen plasma (O ₂ plasma) state, the oxygen content in La _0.5 Sr _0.5 CoO _3-x constituting the anode is increased to The effect may be further enhanced.

Next, the strained layer 40 made of PZT, which is a piezoelectric material, is formed by a sol-gel method, and then the upper electrode 45 made of aluminum, platinum, silver, or the like by a sputtering method. To form sequentially.

Then, the upper electrode 45, the strained layer 40, the lower electrode 35, and the membrane 30 are patterned to separate the actuator 65 pixel by pixel.

Meanwhile, as shown in FIG. 3D, the upper electrode 45, the deformation layer 40, the lower electrode 35, and the membrane 30 positioned in the support region of the actuator 65 have the shape shown in FIG. 2. One end of the membrane 30 is sequentially etched to expose one end of the membrane 30, and the membrane 30, the etch stop layer 20, and the protective layer 15 are sequentially etched at one end of the exposed support region to form a drain pad (not shown). The via hole 50 is formed to expose one end, and the via contact 55 is formed to electrically connect the drain pad (not shown) and the lower electrode 35 by a lift-off process.

Referring to FIG. 3E, a second sacrificial layer 70 made of silicon (Si) is formed on the entire surface of the actuator 65 patterned in units of pixels.

Subsequently, since the mirror surface 60 should be formed flat on the second sacrificial layer 70, the surface of the second sacrificial layer 70 may be CMP to eliminate the step generated in the process of forming the actuator 65 of the one-layer structure. Planarization is done through a chemical mechanical polishing process.

Referring to FIG. 3F, after seating the post surface for forming the mirror surface 60 supported by the post 75 on the second sacrificial layer 70, aluminum (Al) having excellent reflection characteristics is formed thereon. The mirror surface 60 is formed by depositing and patterning the same by the actuator 65.

Referring to FIG. 3G, the second sacrificial layer 70 and the first sacrificial layer 25 are removed by an ashing process using XeF ₂ gas. As such, the second air gap 70 ′ is formed between the mirror surface 60 and the actuator 65 by removing the second sacrificial layer 70, and the driving substrate 5 by removing the first sacrificial layer 25. A first air gap 25 ′ is formed between the actuator 65 and the actuator 65 to complete the manufacturing process of the two-layer thin film type optical path control apparatus in which the mirror surface 60 can be driven by the actuator 65. .

As described above, the above-described contents are described with reference to a preferred embodiment of the present invention. In addition to the other two-layer structure, the single-layer thin film type optical path control device may be easily modified by applying the core technical idea of the present invention.

As described above, according to the present invention, by preventing the afterimage caused by the fatigue of the strained layer, there is an effect that can improve the performance and reliability of the thin film type optical path control device.

Claims (3)

After forming an actuator including a first sacrificial layer, a membrane, a lower electrode, a strained layer, and an upper electrode on a driving substrate having a transistor array of M × N (M, N is an integer), and patterning the pixel by pixel, In the method of manufacturing a thin film type optical path control device by removing the first sacrificial layer, Method for manufacturing a thin film type optical path control device, characterized in that for forming the lower electrode La _0.5 Sr _0.5 CoO _3-x According to claim 1, The manufacturing method of the thin film type optical path control device, Forming a driving substrate; Forming and patterning a first sacrificial layer on the driving substrate; Stacking nitride on a driving substrate exposed by patterning the first sacrificial layer and the first sacrificial layer to form a membrane; Stacking La _0.5 Sr _0.5 CoO _3-x on an upper front surface of the membrane to form a lower electrode; Stacking PZT on the lower electrode to form a strained layer; Stacking a conductive material on top of the strained layer to form an upper electrode; Sequentially patterning the upper electrode, the strain layer, the lower electrode, and the membrane to electrically connect the lower electrode and the drain pad of the driving substrate to form an actuator; Forming a second sacrificial layer of silicon (Si) on the entire surface of the actuator; Forming a post capable of supporting a mirror surface on the second sacrificial layer and then forming a mirror surface thereon; And removing the second sacrificial layer and the first sacrificial layer. The method of claim 1 or 2, wherein the forming of the lower electrode, A method of manufacturing a thin film type optical path control device, comprising sputtering in an oxygen plasma (O ₂ Plasma) state.