KR19990018836A - Manufacturing method of thin film type optical path control device - Google Patents

Abstract

The present invention relates to a method for manufacturing a thin film type optical path control device, to form a sacrificial layer formed with a support on a substrate, to form a membrane thereon, and to form an etching hole in the membrane along the portion to be etched pixel by pixel, The sacrificial layer is removed through the etching hole to form an air gap, and the lower electrode, the strain layer, and the upper electrode are formed on the membrane to be etched to form an actuator in pixels, and to apply an image signal voltage to the actuator. Forming a via contact.

Therefore, the air gap is formed by removing the sacrificial layer before forming the upper electrode serving as the strained layer and the mirror, so that damage of the strained layer and the upper electrode due to etching does not occur, and the sacrificial layer is formed for the uniform etching. It is not necessary to form an etching hole in the center of the upper electrode, which can bring about an effect of increasing the reflection efficiency of the mirror surface.

Description

Manufacturing method of thin film type optical path control device

The present invention relates to a method for manufacturing a thin film type optical path control device, and more particularly, a sacrificial layer removing process for forming an air gap of an actuator is performed before the strained layer and the upper electrode forming process to prevent damage to the strained layer and the upper electrode. It relates to a method of manufacturing a thin film type optical path control device for preventing.

In general, an optical path control device capable of forming an image by adjusting a light flux is 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. Liquid crystal displays (hereinafter referred to as "LCD"), DMD (Deformable Mirror Device), AMA (Actuated Mirror Arrays) and the like.

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 into 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 problem that the response speed of the liquid crystal material therein is slow.

Accordingly, in order to solve the problems of the LCD as described above, a device such as a DMD or an AMA has been developed. Currently, AMA can achieve a light efficiency of 10% or more, while DMD has a light efficiency of about 5%. In addition, the AMA is not only affected by the polarity of the incident luminous flux but also does not affect the polarity of the luminous flux.

Typically, the respective actuators formed inside the AMA cause 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.

The AMA is classified into a bulk type and a thin film type. Currently, AMA is the main trend of the thin-film optical path control device. The thin film type optical path control device is filed under the name of the manufacturing method of the thin film type optical path control device which the applicant has filed a patent application with the Korean Patent Office.

1 is a plan view of a thin film type optical path adjusting device described in the prior application, Figure 2 is a cross-sectional view taken along the line AA 'of FIG.

1 and 2, the thin film type optical path adjusting device described by the prior application includes a substrate 5 and an actuator 65 formed thereon.

The actuator 65 has a cantilever shape in which one side is supported at a portion where the drain pad 10 is formed below, and includes a membrane 30, a lower electrode 35, a strained layer 40, and an upper electrode 45. The via contact 55 includes a via contact 55 vertically formed to the drain pad 10 so that the drain pad 10 and the lower electrode 35 are electrically connected to each other.

One side of the planar shape of the actuator 65 has a rectangular concave portion at the center thereof, and the concave portion is formed in a shape widening stepwise toward both edges. The other side of the actuator 65 has a quadrangular protrusion that narrows in a stepped manner toward the central portion corresponding to the concave portion. Therefore, the concave portion of the actuator 65 adjacent to the concave portion of the actuator 65 is fitted, and the rectangular projection is fitted to the concave portion of the adjacent actuator 65.

On the other hand, in order to manufacture such a thin-film optical path control apparatus, first, a sacrificial layer (not shown in the drawing) is formed on the substrate 5, and then a portion in which the support part of the actuator 65 is formed is formed. Subsequently, after forming the membrane 130, the lower electrode 135, the strained layer 140 made of a piezoelectric material such as PZT or PZLT, and the upper electrode 145 made of aluminum, platinum, silver, or the like, the drain pad 10 may be formed. The via contact 55 is formed in the upper portion in which the via hole is formed so that the drain pad 10 and the lower electrode 35 are electrically connected to each other. Subsequently, the strain layer 40, the lower electrode 35, and the membrane 30 are sequentially patterned in pixel units, and then the sacrificial layer is removed to form an air gap 25.

In particular, in the process of removing the sacrificial layer, a hydrofluoric acid (HF) solution having good etching characteristics with respect to silicon oxide (PSG) containing phosphorus constituting the sacrificial layer is used as an etching solution, and a plurality of constituting actuators 65 are formed. In order to protect the layers to form a protective film by applying a PR on the entire surface and then performing an etching process, to maintain a constant pH value of the etching solution so that the etching rate of the sacrificial layer is constant To this may be added a buffer solution such as ammonium fluoride (NH ₄ F).

Nevertheless, the conventional sacrificial layer removal process has a problem in that the hydrofluoric acid solution penetrates into the cracks or gaps of the protective film to damage the strained layer 40 or the upper electrode 45.

In particular, there is a problem in that the actuator 65 is defective due to a sticking phenomenon in which one end of the actuator 65 comes into contact with the substrate due to residues in the rinsing and drying processes after removing the sacrificial layer.

The present invention is to solve the above-mentioned problems, before forming the lower electrode, the strain layer and the upper electrode, only the membrane is formed and then the sacrificial layer is removed to form an air gap and then the lower electrode, strain layer and It is an object of the present invention to provide a method of manufacturing a thin film type optical path control device capable of forming an upper electrode to prevent damage and sticking of an actuator due to a sacrificial layer removal process.

In order to achieve the above object, the present invention provides a sacrificial layer having a support formed on a substrate having M × N (M, N is an integer) transistors and a drain pad formed on one side thereof, and forming a membrane thereon. And forming an etching hole in the membrane along a portion to be etched in pixel units, forming an air gap by removing the sacrificial layer through the etching hole, and forming a lower electrode, a strain layer, and an upper electrode on the membrane. And forming an actuator in a pixel unit, and forming a via contact for applying an image signal voltage to the actuator.

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 thin film type optical path control device according to the applicant's prior application,

2 is a cross-sectional view taken along the line A-A 'of FIG.

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

Figure 4a to 4h is a manufacturing process diagram of the thin film type optical path control apparatus according to the present invention.

* Explanation of symbols for main parts of the drawings

100: substrate 105: drain pad

110: protective layer 115: etch stop layer

120: sacrificial layer 125: air gap

130: membrane 131: etching hole

135 lower electrode 140 strained layer

145: upper electrode 150: via hole

155: Via Contact 160: Actuator

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

Similar to the conventional structure, the optical path adjusting apparatus according to the present invention includes a substrate 100 and an actuator 160 formed on the substrate 100, as shown in FIG. 3. The substrate 100 is disposed on the drain pad 105 formed on one side of the substrate 100, the protective layer 110 and the protective layer 110 stacked on the substrate 100 and the drain pad 105. The stacked etch stop layer 115 is included.

The actuator 160 includes a membrane 130, a lower electrode 135, and a strained layer on a substrate 100 having M × N (M, N is an integer) transistors and a drain pad 105 formed on one side thereof. And a via contact 155 electrically connecting the upper electrode 145 and the drain pad 105 to apply an image signal voltage to the actuator 160. do.

Hereinafter, the manufacturing method of the thin film type optical path control device according to the present invention will be described in detail.

4A to 4F illustrate a manufacturing process diagram of a thin film type optical path control apparatus according to a preferred embodiment of the present invention.

Referring to FIG. 4A, a protective layer 110 of silicate glass (PSG) material is formed on an upper portion of a substrate 100 having M × N transistors embedded in a matrix and having a drain pad 105 formed on one side thereof. To form. The protective layer 110 is formed to have a thickness of about 1.0 to 2.0 μm using a chemical vapor deposition (CVD) method. The protective layer 110 prevents damage to the substrate 100 in which the transistor is embedded during subsequent processing.

An etch stop layer 115 made of nitride is formed on the passivation layer 110. The etch stop layer 115 is formed to have a thickness of about 1000 to 2000 kPa using a low pressure chemical vapor deposition (LPCVD) method. The etch stop layer 115 prevents the substrate 100 and the protective layer 110 from being damaged by the subsequent etching process.

The sacrificial layer 120 is formed on the etch stop layer 115. The sacrificial layer 120 is formed of a silicate glass (PSG) to have a thickness of about 0.5 to 4.0㎛ by the atmospheric pressure chemical vapor deposition (APCVD) method. In this case, since the sacrificial layer 120 covers the upper portion of the substrate 100 in which the transistor is embedded, the flatness of the surface thereof is very poor. Therefore, the surface of the sacrificial layer 120 is planarized by using a spin on glass (SOG) method or a chemical mechanical polishing (CMP) method.

Subsequently, a portion of the sacrificial layer 120 where the drain 105 is formed is etched to expose a portion of the etch stop layer 115, thereby forming a portion on which the support portion of the actuator 160 is to be formed.

Referring to FIG. 4B, the membrane 130 is formed on the exposed etch stop layer 115 and on the sacrificial layer 120. The membrane 130 is formed to have a thickness of about 0.1 to 1.0 ㎛ using a low pressure image vapor deposition (LPCVD) method. At this time, the stress in the membrane 130 is adjusted while changing the ratio of the reaction gas in the low pressure reaction vessel.

Referring to FIG. 4C, an etching hole 131 may be formed at one end of the membrane 130 to remove the sacrificial layer 120. 4D is a plan view of FIG. 4C, in which the etching hole 131 is formed in a portion to be patterned and removed pixel by pixel in a subsequent process. That is, the planar shape of the membrane 130 is a virtual line, one side has a concave portion of the rectangular shape in the center thereof, the concave portion is formed in a shape that widens stepwise toward both edges, The side has a quadrangular protrusion that narrows stepwise toward the central portion corresponding to the concave portion. Thus, the concave portion of the membrane 130 adjacent to the concave portion of the membrane 130 is fitted, and the rectangular protrusion is inserted into the concave portion of the adjacent membrane 130, so that the etching hole 131 is thus It is formed at the boundary between the membrane 130 and the membrane 130 to be patterned and removed in a subsequent process.

Referring to FIG. 4E, the sacrificial layer is removed with a hydrofluoric acid (HF) solution having good etching characteristics for phosphorus-containing silicon oxide (PSG) constituting the sacrificial layer 120, and thus, between the substrate 100 and the membrane 130. An air gap 125 is formed in the gap. The hydrofluoric acid solution flows into the sacrificial layer 120 through the etching hole 131.

Referring to FIG. 4F, a lower electrode 135 made of a metal such as platinum or platinum-tantalum having excellent electrical conductivity is formed on the membrane 130 on which the air gap 125 is formed to have a thickness of about 500 to 2000 μs by a sputtering method. Form. The lower electrode 135 receives an image signal from the transistor embedded in the driving substrate 100 via the drain pad 105 and the via hole 150 as a signal electrode.

Subsequently, the strained layer 140 made of a piezoelectric material such as PZT or PZLT is disposed on the lower electrode 135 using a sol-gel method, a sputtering method, or a chemical vapor deposition (CVD) method. It is formed to have a thickness of about -1.0 μm. In addition, the strained layer 140 is phase-shifted using a rapid heat treatment (RTA) method. On the other hand, the connection part of the support part 165 of the actuator 160 and the drive part 170 which are the most vulnerable to crack generation by stress concentration during the rapid heat treatment process of the deformation layer 140 can be rounded gently to disperse the deformation stress to some extent. Cracking is suppressed as much as possible.

The upper electrode 145 made of aluminum, platinum or silver is formed on the strained layer 140 to have a thickness of about 0.1 μm to about 1.0 μm by the sputtering method.

The upper electrode 145 is applied with a bias voltage as a common electrode to generate an electric field between the lower electrode 135 and the upper electrode 145.

Referring to FIG. 4G, the strained layer 140, the lower electrode 135, the membrane 130, the etch stop layer 115, and the protective layer 110 are formed from the portion where the drain pad 105 is formed in the strained layer 140. After etching sequentially to form the via hole 150, the drain pad 105 and the lower electrode 135 is electrically connected to the inside of the via hole 150 by sputtering a metal such as tungsten, platinum, aluminum, or titanium. The via contact 155 is formed to be connected to each other. The via contact 155 is formed vertically from the lower electrode 135 to the top of the drain pad 105 in the via hole 150. Accordingly, the image signal is applied to the lower electrode 135 through the drain pad 105 and the via contact 155 from the transistor embedded in the substrate 100.

Referring to FIG. 4H, as mentioned in FIG. 4D, the cantilever in which the actuator 160 is supported by the support part by sequentially patterning the strained layer 140, the lower electrode 135, and the membrane 130 along an imaginary line. Have a shape. At this time, the etching hole 131 formed in the membrane 130 is removed along the boundary of the actuator 160.

After the device of the thin film type AMA is completed as described above, platinum-tantalum (Pt-Ta) is deposited on the lower end of the driving substrate 100 using a sputtering method to form an ohmic contact (not shown).

Next, after applying a photoresist (not shown) on the driving substrate 100, a tape carrier package for applying a bias voltage to the upper electrode 145 and an image signal to the lower electrode 135. (Not shown) In order to bond, the driving substrate 100 is cut to have a predetermined thickness.

Subsequently, in order to expose the pad (not shown) of the AMA panel required for TCP bonding, the pad portion of the AMA panel is etched using a dry etching method, and the driving substrate 100 having the thin film type AMA element is formed. It is completely cut into shapes and connected to the pad of the AMA panel and TCP to complete the manufacture of the thin film AMA module.

In the thin film type optical path adjusting device, an image signal voltage is applied to the lower electrode 135, which is a signal electrode, and a bias voltage is applied to the upper electrode 145, which is a common electrode, between the upper electrode 145 and the lower electrode 135. An electric field will be generated. The strained layer 140 between the upper electrode 145 and the lower electrode 135 causes deformation by the electric field, and the strained layer 140 contracts in a direction perpendicular to the electric field. Accordingly, the actuator 160 including the deformation layer 140 is bent at a predetermined angle to form an image by projecting the light beam incident from the light source onto the screen through the slit.

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 it merely illustrates a preferred embodiment of the present invention.

Therefore, according to the present invention, before forming the lower electrode, the strain layer and the upper electrode, only the membrane is formed and then the sacrificial layer is removed to form an air gap, and then the etching solution is formed by forming the lower electrode, the strain layer and the upper electrode. There is no risk of damaging the deformable layer or the upper electrode, and the sacrificial layer removal process is performed while the both ends of the air gap are supported on the substrate, so there is no sticking phenomenon that one end of the actuator is in contact with the substrate. In addition, there is no need to form an etching hole in the center of the actuator in order to equalize the etching rate, so that the reflective area of the upper electrode can be secured.

Claims (1)

Forming a sacrificial layer on a substrate having M × N (M, N is an integer) transistors and a drain pad formed on one side thereof, forming a support on the sacrificial layer, and a sacrificial layer on which the support is formed. Forming an membrane on the membrane, forming an etching hole in the membrane along a portion to be etched in pixels, forming an air gap by removing the sacrificial layer through the etching hole, and forming a lower electrode on the membrane; Forming a strained layer and an upper electrode, etching the upper electrode, the strained layer, the lower electrode, and the membrane to form an actuator in a pixel unit, and forming a via contact for applying an image signal voltage to the actuator. Method of manufacturing a thin film type optical path control device comprising the step of.