KR100229789B1 - Planarization method for thin film actuated mirror array - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of planarizing an array of thin film actuated mirrors (TFAMA) used in a projection type image display apparatus, In order to solve the problem that the planarization efficiency of the sacrifice layer is reduced due to the rigidity of the Si substrate, the parasitic deposition layer deposited on the rear surface of the driving substrate having the active elements formed in the matrix structure of the optical path adjusting device is removed A step of planarizing the rear surface of the substrate from which the parasitic deposition layer has been removed, a step of laminating a sacrifice layer on top of the driving substrate on which the rear surface is planarized, and a step of planarizing the sacrifice layer The sacrificial layer is flattened in a state in which it is not affected by the physical state of the rear surface of the driving substrate, The surface condition of the mirror surface of the actuator formed in a predetermined shape, that is, the upper electrode, is provided in a flat state, thereby enhancing the performance and reliability of the optical path adjusting device.

Description

Planarizing method of optical path reducing device

FIG. 1 is a cross-sectional view schematically showing a general optical path adjusting device. FIG.

Figs. 2a and 2b are cross-sectional views illustrating a planarization method of an optical path adjusting apparatus according to an embodiment of the present invention;

3 (a) to 3 (e) are sectional views sequentially showing a planarizing method of an optical path adjusting apparatus according to the present invention.

Description of the Related Art [0002]

300: driving substrate 310: parasitic laminated layer

320: passivation layer 330: etch stop layer

340: sacrificial layer

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flattening method of an optical path adjusting device (TFAMA) used as a projection type image display device, and more particularly to a flattening method for flattening a rear surface of a driving substrate, The present invention relates to a method of planarizing an optical path adjusting apparatus.

2. Description of the Related Art A flat panel display (FPD) used as an image display device is a flat panel display for replacing a cathode ray tube (CRT) having a large weight, a large volume, and a large power consumption. Type display. In addition, the device used in such a display device may be a direct display of electrons emitted by an electric field effect such as a plasma display panel (PDP), electroluminescence (EL), a light emitting diode (LED) A light valve (not shown) such as a liquid crystal display (LCD), an electrochromic display (ECD), a digital micromirror display (DMD), an actuated mirror array (AMA), a grating light value emitting display device that functions as a light valve and emits an image by reflected light without emitting electrons.

At this time, the AMA (Actuated Mirror Array) has a mirror array in which a plurality of layers are sequentially stacked on a driving substrate composed of active matrix driving (active matrix driving) in order to improve electro-optical nonlinear characteristics And the actuator is formed in a cantilever structure in which an insulating layer made of a piezoelectric ceramic composition is interposed between two conductive layers respectively acting as signal electrodes and common electrodes among the plurality of layers, And reflects the white light emitted from the light source by the piezoelectric deformation of the piezoelectric material by the electric signal applied to the two conductive layers along the controlled optical path on the screen to display an image.

1, an actuator formed in a predetermined shape includes a passivation layer 110 for protecting an active element from an etchant on a driving substrate 100 having a plurality of active elements (not shown) embedded in a matrix structure, An etch stop layer 120 for protecting the passivation layer 110 from the hydrofluoric acid solution HF when the sacrificial layer is removed and a membrane 140 sequentially stacked on top of the etch stop layer, And a plurality of layers of the upper electrode 170 and the supporting portion and the other end of which one end is attached to the surface of the driving substrate 100 are formed on the surface of the driving substrate 100, Which are spaced apart from each other by a predetermined distance.

At this time, the lower electrode 150 is electrically connected to a plurality of active elements embedded in the driving substrate 100 to function as a signal electrode, while the upper electrode 170 functions as a common electrode having good reflection characteristics do.

Therefore, when an electrical signal is applied to the lower electrode 150 through the active element, the deformation portion 160 exhibits piezoelectric deformation due to a potential difference between the lower electrode 150 and the upper electrode 170 The driving unit of the actuator is tilted at a predetermined angle, and as a result, the white light of the light source incident on the surface of the upper electrode 170 serving as the reflection surface is reflected, and the image is displayed on the screen .

However, since the driving substrate 100 includes a plurality of active devices formed of transistors, such as PMOS, formed on a silicon substrate by a semiconductor integrated circuit manufacturing process, the driving substrate 100 is provided with a topology having a predetermined step, The top surface of the upper electrode 170, which functions as a reflective surface, is maintained in a poor state, and thus the surface of the upper electrode 170 It becomes difficult to control the reflection of light.

The passivation layer 110, the etch stop layer 120, and the sacrificial layer 140 are formed on the upper surface of the driving substrate 100 of the optical path adjusting device according to one embodiment of the present invention for providing the surface of the upper electrode 170 in a flat state. The sacrificial layer 130 is sequentially formed to have a predetermined thickness, and then the sacrificial layer 130 is planarized by a chemical mechanical polishing (CMP) process.

That is, as shown in FIGS. 2A and 2B, a planarizing method of an optical path adjusting device using a conventional chemical mechanical polishing (CMP) process includes a step of forming a plurality of active elements A passivation layer 110 for protecting the active device on the substrate 100 and an etch stop for protecting the passivation layer 110 from a hydrofluoric acid solution (HF) for removing the sacrificial layer 130 of the subsequent process The sacrificial layer 130 is removed by a layer 120 and a subsequent process to form a sacrificial layer 130 to be formed into an air gap by a predetermined thickness and then the sacrificial layer 130 is subjected to chemical mechanical polishing Flattened.

However, as shown in FIG. 3 (a), the method of planarizing the optical path adjusting device using the conventional chemical mechanical polishing (CMP) process includes the steps of forming an active element in the driving substrate, Not only the wafer is deformed by a plurality of thermal processes performed in the process of forming the etching stop layer, but also in a state where silicon nitride (Si3N4) having rigidity is non-uniformly deposited on the rear surface of the wafer in the process of forming the etching stop layer The planarization process is performed to reduce the planarization efficiency and reduce the flatness of the surface on which the actuator of the optical path adjusting device formed of a plurality of layers is to be formed. As a result, the optical efficiency of the upper surface of the optical path adjusting device is reduced.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a method of manufacturing a plasma display panel in which silicon nitride (Si3N4) which is parasitically deposited on the rear surface of a driving substrate is removed and the rear surface of the driving substrate is planarized by polishing, Which can improve the effect of the front planarization process of the driving substrate.

In order to achieve the above object, according to the present invention, there is provided a method of planarizing an optical path adjusting apparatus comprising an actuator corresponding to each of the active elements on a driving substrate provided with active elements of a matrix structure, Removing the deposited parasitic deposition layer; Planarizing the rear surface of the driving substrate from which the parasitic deposition layer is removed; Stacking a sacrificial layer on the front surface of the driving substrate on which the rear surface is planarized; And planarizing the sacrificial layer. The present invention also provides a method of planarizing an optical path adjusting apparatus comprising:

In one embodiment of the present invention, the silicon nitride (Si 3 N 4) is removed by dry etching.

According to an embodiment of the present invention, the dry etching process is an ion beam milling process.

According to an embodiment of the present invention, the rear surface of the driving substrate is planarized by a chemical mechanical polishing process.

According to an embodiment of the present invention, the polishing process uses alumina (Al 2 O 3) as a slurry.

According to another aspect of the present invention, there is provided a method of planarizing an optical path adjusting device, wherein the sacrificing layer is planarized by a chemical mechanical polishing (CMP) process.

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

3 (a) to 3 (e) are views sequentially illustrating planarization methods of an optical path adjusting apparatus according to the present invention.

First, active elements such as PMOS are formed in a matrix structure on a silicon substrate by a semiconductor integrated circuit manufacturing process. At this time, the silicon substrate having the plurality of active elements having the matrix structure is used as the driving substrate 300 of the optical path adjusting device to be formed by a subsequent process.

At this time, the driving substrate is deformed as shown in (a) of FIG. 3 by the thermal process according to the process of forming the active elements.

Thereafter, in order to prevent the plurality of active elements from being chemically or physically damaged from the outside under a high temperature atmosphere when the mirror array composed of a plurality of layers is formed by a deposition process performed in a later process, A passivation layer 320 for protecting the plurality of active elements is formed by applying an insulating material to a predetermined thickness by a deposition process on an upper portion of a driving substrate 300 having a structure.

At this time, the insulating material can exhibit an insulating property for preventing a plurality of active elements formed on the driving substrate 300 from being electrically conducted to each other, as well as a surface passivation characteristic of the active element And the insulating material used to satisfy such a characteristic requirement is composed of phosphorus-containing PSG (phosphosilicate glass) or BPSG (borophosphosilicate glass) exhibiting good flow characteristics at high temperature, The deposition process for depositing is performed by chemical vapor deposition (CVD).

On the other hand, in order to prevent the passivation layer 320 from being exposed to the hydrofluoric acid (HF) solution to be chemically damaged during the etching process for removing the sacrifice layer 340, HF) solution is deposited to a predetermined thickness by a deposition process to form an etch stop layer 330. The etch stop layer 330 is formed by depositing an insulating material having good corrosion resistance against the HF solution.

In addition, the insulating material constituting the etching stop layer 330 is not only excellent in insulation characteristics, but also has a composition of silicon nitride (Si 3 N 4) excellent in corrosion resistance to a hydrofluoric acid (HF) solution as described above, And is performed by a vapor deposition process, particularly a low pressure chemical vapor deposition process.

At this time, rigid silicon nitride (Si 3 N 4) is non-uniformly deposited on the rear surface of the driving substrate 300 when the etching stop layer 330 is formed by the low pressure chemical vapor deposition (LPCVD) process to form the parasitic deposition layer 310 do.

3 (a), the driving substrate 300 of the optical path adjusting device formed by the above-described process is deformed in its shape, and the driving substrate 300 formed on the rear surface 300 of the driving substrate is formed non- The rear surface remains uneven due to the parasitic deposition layer 310 of silicon nitride (Si 3 N 4).

Therefore, in order to planarize the rear surface of the driving substrate 300, first, the parasitic deposition layer 310 made of rigid silicon nitride (Si 3 N 4) is subjected to a dry etching process such as ion beam milling, Remove as shown.

3 (c), the rear surface of the driving substrate 300 is removed by a chemical mechanical polishing process using alumina (Al 2 O 3) as a slurry on the rear surface of the driving substrate 300 from which the parasitic deposition layer 310 is removed As shown in FIG.

3 (d), phosphorus-containing silicon oxide, that is, phosphosilicate glass (PSG) or polycrystalline silicon (PSG), is formed on the stop-shaped layer 330 of the back- The sacrificial layer 340 is formed by stacking a plurality of layers constituting the actuator by a post process so as to form a hydrofluoric acid solution HF So as to form an air gap.

Therefore, the surface of the sacrificial layer 340, which is provided in a state of poor topology as described above, is chemically mechanically polished (as described above) in order to provide the surface of the upper electrode of the actuator formed in a predetermined shape in a flat surface state by a subsequent step Planarization process such as a CMP process.

That is, the chemical mechanical polishing (CMP) process is performed by driving a polishing apparatus composed of a chuck for fixing a member for planarization and a rotary plate opposed to the chuck, so that the phosphorus-containing silicon oxide, that is, the phosphosilicate glass The sacrificial layer 340 is polished by driving the polishing apparatus in a state where the driving substrate 300 is fixed to the chuck such that the sacrificial layer 340 made of polycrystalline silicon (PSG) or polycrystalline silicon is in surface contact with the rotating plate Since the driving substrate 300 is provided in a flat state according to the present invention, the sacrificing layer 340 is planarized without being affected by the physical state of the rear surface of the driving substrate 300, 340 provide a flat surface condition as shown in Figure 3 (e).

On the other hand, an actuator having a predetermined shape is formed on the flattened sacrificial layer 340 as a post-process through the following process.

First, silicon nitride is deposited on the etch stop layer 330 exposed through the pattern of the sacrificial layer 340 and the sacrificial layer 340 by a physical vapor deposition process (PVD) or a chemical vapor deposition process (CVD) or the like And laminated to a predetermined thickness to form a membrane.

In addition, a conductive metal such as platinum (Pt) and titanium (Ti) or one of these elements is deposited to a predetermined thickness on the membrane by a vacuum deposition process such as a sputtering deposition process to form a lower electrode, And is electrically connected to an active element formed on the driving substrate 300 through a contact hole or the like formed in the membrane to function as a signal electrode.

In addition, a ceramic composition exhibiting piezoelectric characteristics on the lower electrode is laminated to a predetermined thickness by a sputter deposition process and a sol-gel process to form a deformed portion. The ceramic composition may be formed of a piezoelectric ceramic of BaTiO3, Pb (Zr, Ti) Pb (Mg, Nb) O3.

Thereafter, a conductive metal such as platinum (Pt) and titanium (Ti) or one of these elements is deposited on the deformed portion to a predetermined thickness by a vacuum deposition process such as a sputtering deposition process to form an upper electrode As a result, a mirror array in which a plurality of layers are sequentially stacked on the driving substrate 300 is formed.

Meanwhile, a plurality of layers constituting the mirror array are sequentially etched from the top by a dry etching process, for example, a reactive ion etching (RIE) process having a favorable anisotropic etching property, thereby forming an actuator having a predetermined shape, A portion of the sacrificial layer 340 formed on the etch stop layer 330 is exposed through a pattern.

At this time, if the actuator formed in a predetermined shape is immersed in a hydrofluoric acid solution, the sacrificial layer 340 exposed through the pattern of the actuator is removed by the etching action of the hydrofluoric acid solution, Is formed with a cantilever structure in which one end thereof is supported on the etch stop layer (330) and the other end thereof is spaced apart from the etch stop layer (330) by a predetermined distance.

Therefore, when an electric signal is applied from the external control system to the lower electrode of the actuator through the active element built in the driving board 300, a potential difference is generated between the lower electrode and the upper electrode, The actuator of the actuator is tilted at a predetermined angle by the piezoelectric deformation of the deformed portion.

That is, the white light of the light source incident on the surface of the upper electrode provided in a flat surface state according to the present invention is reflected along the optical path controlled by the driving of the actuator to display an image on a screen not shown.

Therefore, according to the present invention, the parasitic deposition layer 310 of silicon nitride (Si 3 N 4) formed on the rear surface of the driving substrate 330 is removed, and the rear surface of the deformed driving substrate 300 is flattened The surface state of the mirror surface of the actuator formed in a predetermined shape on the drive substrate 300, that is, the surface of the upper electrode, may be determined by the surface state of the sacrificial layer 340 in a state in which the sacrifice layer 340 is not affected by the physical state of the rear surface of the drive substrate. Thereby improving the performance and reliability of the optical path adjusting device.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. .

Claims (6)

A method for planarizing an optical path adjusting apparatus comprising an actuator corresponding to each of the active elements on a driving substrate having an active element having a matrix structure, the method comprising: removing a parasitic deposition layer parasitically deposited on a rear surface of the driving substrate; Planarizing the rear surface of the driving substrate from which the parasitic deposition layer is removed; Stacking a sacrificial layer on the front surface of the driving substrate on which the rear surface is planarized; And planarizing the sacrificial layer. The flattening method of an optical path adjusting apparatus according to claim 1, wherein the step of removing the parasitic deposition layer is performed by a dry etching process. 3. The method of claim 2, wherein the dry etching process is an ion beam milling process. The planarization method of an optical path adjusting apparatus according to claim 1, wherein the step of planarizing the rear surface of the driving substrate is performed by a chemical mechanical polishing (CMP) process. The method of claim 4, wherein the chemical mechanical polishing step uses alumina (Al 2 O 3) as a slurry. The planarizing method of an optical path adjusting apparatus according to claim 1, wherein the sacrificing layer is planarized by a chemical mechanical polishing (CMP) process.