KR100195640B1 - Method for fabricating an optical projection system - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an optical path control device, wherein the sacrificial film, the membrane, and the lower electrode are patterned in units of pixels at the step of forming the sacrificial film. The upper electrode may be prevented from being damaged in the process of patterning the actuator on a pixel basis.

Description

Manufacturing method of optical path control device

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an optical path control device used in a projection image display device, and more particularly, to a method for manufacturing an optical path control device that can prevent damage to an upper electrode and easily separate actuators on a pixel basis.

An image display apparatus is classified into a direct view type image display apparatus and a projection type image display apparatus according to a display method.

Direct image display device includes CRT (Cathode Ray Tube), which has good image quality but it has problems such as increase of weight and thickness as the screen gets bigger and expensive. There is.

Projection type image display devices include a large screen liquid crystal display (hereinafter referred to as an LCD). Such a large screen LCD can be thinned to reduce weight. However, such an LCD has a very low light efficiency because a large loss of light due to a flat plate and a thin film transistor for driving the LCD are formed for each pixel, thereby limiting an increase in the aperture ratio (light transmission area).

Accordingly, a projection type image display device using Actuated Mirror Arrays (hereinafter referred to as AMA) has been developed by Aura, USA. A projection image display device using AMA separates white light emitted from a light source into red, green, and blue light, and then changes the light path by driving an optical path control device made of actuators. That is, the actuators are mounted on the actuators, and the actuators are individually driven to reflect the inclined mirrors, thereby changing the light path, thereby controlling the amount of light to project onto the screen. Therefore, an image appears on the screen. In the above, the actuator tilts the mirror by using an electric field generated and deformed by a voltage to which a deformable part made of piezoelectric or electrostrictive ceramic is applied. AMA is classified into one-dimensional AMA and two-dimensional AMA according to the driving method. One-dimensional AMA has mirrors arranged in an M × 1 array, and two-dimensional AMA has mirrors arranged in an M × N array. Therefore, the projection type image display apparatus using the one-dimensional AMA pre-scans the M × 1 beams using the scanning mirror, and the projection image display apparatus using the two-dimensional AMA displays the image by projecting the M × N luminous fluxes.

In addition, the actuator is classified into a bulk type and a thin film type according to the shape of the deformable portion. The bulk type thinly cuts a multilayer ceramic, mounts a ceramic wafer having a metal electrode therein on a driving substrate, processes it by sawing, and mounts a mirror. However, bulk actuators require a long process time because the actuators must be separated by sawing, and there is a problem that the response speed of the deformation part is slow. Therefore, a thin-film actuator that can be manufactured using a semiconductor process has been developed.

1 (a) to (d) is a manufacturing process diagram of the optical path control apparatus according to the prior art.

Referring to FIG. 1A, a surface of a driving substrate 11 having a pad 13 made of a metal such as Al having a transistor (not shown) embedded in the surface thereof and electrically connected to the transistor. A sacrificial film 15 for forming an air gap is formed in a thickness of about 1 to 2 mu m. Then, the sacrificial film 15 of the portion where the pad 13 is formed is removed by a conventional photolithography method to expose the driving substrate 11 around the pad 13.

Referring to FIG. 1B, the membrane 17 is formed on the driving substrate 11 and the sacrificial layer 15 to a thickness of about 1 μm to 2 μm. In addition, after the grooves are formed to expose the pads 13 in the predetermined portion of the membrane 17, a conductive metal is filled in the grooves to form plugs 19 that are electrically connected to the pads 13. do. Subsequently, a lower electrode 20 having a thickness of about 500 to 2000 micrometers is formed on the membrane 17 so as to be electrically connected to the plug 19. Therefore, the pad 13 and the lower electrode 21 are electrically connected to each other by the plug 19.

Referring to FIG. 1C, the deformation part 23 and the upper electrode 25 are formed on the surface of the lower electrode 21. In the above, the deformable portion 23 is applied to the piezoelectric ceramic or electrodistoric ceramic to a thickness of about 0.7 to 2㎛, the upper electrode 25 is formed by depositing a metal having good reflection characteristics and electrical characteristics. Subsequently, the upper electrode 25, the deformable portion 23, the lower electrode 21, and the membrane 17 are etched to expose the driving substrate 11 to separate the actuators.

That is, a photosensitive film such as photoresist is coated on the entire upper surface of the upper electrode 25 to form a photosensitive film (not shown), and the photosensitive film is formed through a mask having a predetermined shape for separating the upper electrode 25 pixel by pixel. Is exposed and developed.

As a result, the photosensitive film of the developed portion is removed, and a predetermined portion of the upper electrode 25 will be exposed through the portion from which the photosensitive film is removed. In this case, the exposed portion is a portion to be removed in order to form the upper electrode in units of pixels.

Subsequently, a portion of the deformable portion 23 may be removed by performing an etching technique having good anisotropy, for example, reactive ion etching (RIE) to remove the upper electrode 25 exposed through the photosensitive film. Expose In this case, a predetermined portion of the deformable portion 23 exposed by the removal of the upper electrode 25 is a portion to be removed in order to separate the deformable portion 23 in units of pixels. Thereafter, the photoresist film 23 is also separated by the pixel by patterning the same process as the patterning of the upper electrode 25 described above, and the process is repeated for the lower electrode 21 and the membrane 17 so that the actuator is pixel-by-pixel. To separate.

In the separation process of the actuator described above, a common mask may be used for each layer, or an individual etching mask may be used. Then, the protective film 29 is formed on the surface of the upper electrode 25 and the side surfaces of the actuators separated from each other.

Referring to FIG. 1D, the sacrificial layer 15 is removed with an etching solution such as hydrofluoric acid solution (HF). In this case, the protective layer 29 prevents sidewalls of the membrane 17 and the deformable portion 23 from being etched to separate the layers. Next, the protective film 29 is removed to form an air gap 31.

Since the mask is deformed by etching for a long time when the actuators are separated, the method of manufacturing the optical path control apparatus according to the related art etch the upper electrode, the deformable part, the lower electrode and the membrane sequentially using the respective masks.

However, since the step becomes larger toward the lower layer, such as the lower electrode and the membrane, the flatness is lowered, so that it is difficult to form a desired mask, which makes it difficult to separate the actuators. In addition, there is a problem that the upper electrode is damaged because it takes a long time more than 1 hour when etching the deformation portion.

Accordingly, an object of the present invention is to provide a method of manufacturing an optical path control device which can prevent damage to the upper electrode, can easily separate the actuator, and obtain an accurate pattern.

In order to achieve the above objects, in the present invention, there is provided a method of manufacturing an optical path control device on top of a driving substrate having pads embedded in a matrix state and having pads electrically connected to the transistors on a surface thereof. Stacking a sacrificial layer and patterning the sacrificial layer to expose a portion of the driving substrate; Forming a membrane on top of the sacrificial layer and the exposed driving substrate; Forming an opening in a predetermined portion of the membrane to expose the pad, and forming a plug in the opening; Forming a lower electrode on the membrane, the lower electrode in electrical contact with the plug; Patterning the lower electrode and the membrane in units of pixels to expose the sacrificial layer; Filling a portion of the sacrificial layer exposed by the patterning of the lower electrode and the membrane with photoresist; Forming a deformation part on the lower electrode by a lift-off process; After forming the upper electrode only on the upper portion of the deformable portion, there is provided a manufacturing method of the optical path control device comprising the step of removing the sacrificial film.

1 (a) to (d) is a manufacturing process diagram of the optical path control apparatus according to the prior art.

2 (a) to (d) is a manufacturing process diagram of the optical path control apparatus according to an embodiment of the present invention.

* Explanation of symbols for main parts of the drawings

41: drive substrate 43: pad

45: sacrificial film 47: membrane

49: opening 51: plug

53 lower electrode 55 photoresist pattern

57: deformation portion 59: upper electrode

61: protective film 63: air gap

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

2 (a) to (d) is a manufacturing process diagram of the optical path control apparatus according to the present invention.

Referring to FIG. 2 (a), a transistor (not shown) is embedded in a matrix on the surface thereof, and about 1 to 2 탆 is formed on the surface of the driving substrate 41 having the pad 43 electrically connected to the transistor. A sacrificial film 45 of thickness is formed. In the above, the driving substrate 41 is made of an insulating material such as glass or alumina (Al ₂ O ₃ ), or a semiconductor such as silicon. In the above, the sacrificial layer 45 is formed of PSG (Phospho-Silicate Glass) or polycrystalline silicon, and PSG surface spin coating method, if the polycrystalline silicon chemical vapor deposition (hereinafter, referred to as CVD) It is formed by the method. Then, the sacrificial film 45 of the predetermined portion including the pads 43 is etched to expose the driving substrate 41.

Referring to FIG. 2 (b), silicon nitride (Si ₃ N ₄ ) or silicon carbide, such as silicon nitride (Si ₃ N ₄ ) or silicon carbide, is formed on the driving substrate 41 and the sacrificial film 47 by 1 to 2 μm. The membrane 47 is formed by depositing to a thickness of a degree. Then, an opening 49 is formed in a predetermined portion of the membrane 49 by a conventional photolithography method, and the pad is filled with a metal such as tungsten (W) or titanium (Ti) inside the opening 49. And a plug 51 which is electrically connected to the 43. Subsequently, platinum (Pt), platinum / titanium (Pt / Ti), or the like is deposited on the membrane 47 to a thickness of about 500 to 2000 占 퐉 by vacuum deposition or sputtering to form a lower electrode 53. The lower electrode 53 is formed to be electrically connected to the plug 51. Therefore, the pad 43 and the lower electrode 53 are electrically connected by the plug 51.

Then, a predetermined portion of the lower electrode 53 and the membrane 47 is removed by a conventional photolithography method so as to be exposed to the driving substrate 41. In the above, the lower electrode 53 and the membrane 47 need respective etching masks. Then, the photoresist is thickly coated on the driving substrate 41 and the lower electrode 53, and then exposed and developed to form the photoresist pattern 55 on the exposed driving substrate 41. In the above, the photoresist pattern 55 is formed of a positive type photoresist or a negative type photoresist.

Referring to FIG. 2C, the deformation part 57 is formed on the surface of the lower electrode 53. The deformation part 57 may include BaTiO ₃ , PZT (Pb (Zr, Ti) O ₃ ) or PLZT ((Pb, La) (by spin coating method, spray method, or CVD. It is formed by applying piezoelectric ceramics such as Zr, Ti) O ₃ ), or electrodistortion ceramics such as PMN (Pb (Mg, Nb) O ₃ ) to a thickness of about 1 to 2 μm. Then, the photoresist pattern 55 is removed. The photoresist pattern 55 is limited so that the deformation portion 57 is formed only on the lower electrode 53 when the deformation portion 57 is formed. If the deformation portion 57 is formed by the spray method or the CVD method, the deformation portion 57 is also formed on the photoresist pattern 55. However, the deformation portion 57 formed on the photoresist pattern 55 is removed at the same time when the photoresist pattern 55 is removed. That is, in the present invention, the deformation portion 57 is formed by a lift-off process. Therefore, the deformation part 57 is formed only on the upper portion of the lower electrode 53. In addition, since the deformable portion 55 is formed thin, the deformable portion 55 is polarized by an image signal applied during driving without any additional polarization.

The upper electrode 59 is formed on the deformable portion 57. The upper electrode 59 is formed by depositing aluminum, which is a metal having good electrical conductivity and reflective properties, to a thickness of about 500 to 1000 mW by sputtering or vacuum deposition. In the above, since the membrane 47 and the lower electrode 53 are separated, the deformable portion 57 and the upper electrode 59 are formed only on the upper portion of the lower electrode 53, and the actuators are separated without a separate process. Next, a protective film 61 is formed by depositing silicon oxide (SiO ₂ ) or silicon nitride including photoresist on the upper portion of the upper electrode 59 and the side surfaces of the actuators.

Referring to FIG. 2D, the sacrificial layer 45 is removed with an etching solution such as hydrofluoric acid (HF). In the above, the space 63 in which the sacrificial layer 45 is etched becomes an air gap in which actuators are driven. The protective layer 61 prevents the side surface of the deformable portion 57 from being etched in contact with the etching solution when the sacrificial layer 45 is etched. Next, the protective film 61 is removed. In the above, if the protective film 61 is formed of silicon oxide, the protective film 61 is etched and removed together when etching the sacrificial film 45. Therefore, a separate process for removing the protective film 61 is not necessary.

As described above, the present invention forms a membrane and a lower electrode, removes a predetermined portion of the lower electrode and the membrane so that the driving substrate is exposed, forms a photoresist pattern on the exposed driving substrate, and defines the deformation part only on the surface of the lower electrode. To form. Then, by removing the photoresist pattern and forming the upper electrode on the deformation portion, the actuator is separated without any further process.

Therefore, according to the present invention, the actuator can be easily separated into an accurate shape, and it is possible to prevent the upper electrode from being damaged during the separation process.

Claims (3)

A method of manufacturing an optical path control device on a driving substrate having transistors embedded in a matrix and having pads electrically connected to the transistors on a surface thereof, wherein the sacrificial layer is stacked on the driving substrate and the sacrificial layer is patterned. Exposing a portion of the drive substrate; Forming a membrane on top of the sacrificial layer and the exposed driving substrate; Forming an opening in a predetermined portion of the membrane to expose the pad, and forming a plug in the opening; Forming a lower electrode on the membrane, the lower electrode in electrical contact with the plug; Patterning the lower electrode and the membrane in units of pixels to expose the sacrificial layer; Filling a portion of the sacrificial layer exposed by the patterning of the lower electrode and the membrane with photoresist; Forming a deformation part on the lower electrode by a lift process; And forming an upper electrode only on the deformable portion, and then removing the sacrificial layer. The method of claim 1, wherein the sacrificial layer is formed of PSG or polycrystalline silicon, the membrane is formed of a silicon nitride or a silicon carbide silicide, the lower electrode is formed of platinum or platinum / titanium, and the deformation portion is a rotary coating method And a piezoelectric ceramic or an all-ceramic ceramic by spraying or chemical vapor deposition, and the upper electrode is formed of aluminum by sputtering or vacuum deposition. According to claim 1 or 2, wherein the lower electrode is formed in the thickness range of 500 ~ 2000Å, the deformation portion is formed in the thickness range of 1 ~ 2㎛, the upper electrode is formed in the thickness range of 500 ~ 1000Å The manufacturing method of the optical path control apparatus characterized by the above-mentioned.