KR19980023300A - Manufacturing method of thin film type optical path control device - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film type optical path adjusting device used in a projection type image display device, wherein the outgassing, intermetallic compound, and dopant generated by a high temperature process for forming an etch stop layer and a membrane of the thin film type optical path adjusting device. In order to prevent problems such as internal diffusion and destruction of MoS structure, the etching stop layer and the membrane are replaced with amorphous silicon, which can form a film even at low temperature, and formed by plasma chemical vapor deposition at a low temperature below 450 ° C. By solving this problem, the reliability and performance of the thin-film optical path control device can be improved.

Description

Manufacturing method of thin film type optical path control device

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a thin film type optical path control device used as a projection image display device. In particular, outgassing, active element destruction, and impurities that may be generated by a high temperature thermal process in forming an etch stop layer and a membrane The present invention relates to a method for manufacturing a thin film type optical path control device that can prevent various problems such as diffusion.

In general, an image display device is classified into a direct view type image display device and a projection type image display device according to a display method.

The direct view type image display device includes a CRT (Cathode Ray Tube). The CRT image display device has good image quality but has a problem such as an increase in weight and thickness as the screen is enlarged, and a price is expensive. There is.

Projection type image display apparatuses include a large crystal display (Liquid Crystal Display: hereinafter referred to as LCD), and such a large-screen LCD can be thinned to reduce weight.

However, such LCDs have a high loss of light due to a polarizing plate, and thin film transistors for driving the LCD are formed for each pixel, so that there is a limit in increasing the aperture ratio (light transmission area).

Therefore, a projection type image display apparatus using Actuated Mirror Arrays (hereinafter referred to as 'AMA') has been developed.

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 adjusting device made of actuators.

That is, the actuators are mounted on the actuators and reflected on the mirrors inclined by the actuators being individually driven to change the light path to project the light 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 deformation 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. The one-dimensional AMA has mirrors arranged in an M × 1 array, and the 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 M x 1 light beams using a scanning mirror, and the projection type image display apparatus using the two-dimensional AMA projects an M x N light beams to display an image.

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 and mounts a ceramic wafer having a metal electrode formed therein on a driving substrate, and then processes the saw by a 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.

Hereinafter, as shown in FIG. 1, a general thin film type optical path adjusting device forms a sacrificial layer on a driving substrate 100 having a matrix-type active element, and has a predetermined shape formed of a plurality of layers on the sacrificial layer. After the actuator 200 is formed, the sacrificial layer is removed, and the thin film type optical path adjusting device manufactured as described above is operated through an active element embedded in the driving substrate 100 from an external control system. When an electrical signal is applied to the upper electrode 240 of the 200, a potential difference of a predetermined magnitude is generated between the lower electrode 220 and the upper electrode 240, and the deformation part 230 causes the piezoelectric strain to be generated by the potential difference. By doing so, the plurality of actuators 200 are driven individually.

That is, the white light of the light source incident on the surface of the upper electrode 240 serving as the reflective surface is reflected along the optical path changed by the driving of the actuator 200 to display an image on a screen not shown.

On the other hand, the etch stop layer 130 formed on the top of the driving substrate 100 is a silicon nitride (Si ₃ N ₄ ) in a low pressure chemical vapor deposition process in a temperature range of about 750 ~ 800 ℃ (Low Pressure Chemical Vapor Deposition; Hereinafter, referred to as 'LPCVD') is formed by laminating a predetermined thickness on top of the passivation layer 120, the etch stop layer 130 is formed from the above chemical damage by the etching solution used in the subsequent etching process The passivation layer 120 is well protected.

In addition, among the plurality of layers constituting the actuator 200, the membrane 210 may deposit silicon nitride (SiN _x ) on the sacrificial layer (not shown) to a predetermined thickness by a low pressure chemical vapor deposition process (LPCVD). And the process takes place in the temperature range of 800-850 ° C.

However, as the etch stop layer and the membrane are formed of a nitride layer, the nitride layer is difficult to form a film at a low temperature, so that a high temperature process is required, and thus, at the interface of the plurality of layers constituting the actuator 200. Internal diffusion of lead (Pb) or oxygen, generation of intermetallic compounds, such as nitrides of titanium (Ti) or tantalum (Ta), which form unevenly, outgassing in the nitride layer, and high temperatures There is a problem that the breakdown of the MOS structure in the driving substrate due to.

Accordingly, the present invention has been made in order to solve the above problems, and the amorphous-silicon (Silver-Film Enhanced Chemical Vapor Deposition; Amorphous-Silicon) is a method for manufacturing a thin film type optical path control device that can improve the performance of an optical path control device by preventing outgassing, intermetallic compound formation, interdiffusion phenomenon, and destruction of MOS structure. To provide.

In order to achieve the above object, the present invention provides a thin film type optical path control device used as a projection image display device, the passivation layer is formed by stacking a predetermined insulating material on the silicon substrate having an active element in the form of a matrix Forming a etch stop layer by forming an insulating material having a high resistance to an etchant on the passivation layer in a low temperature process and forming an etch stop layer on the etch stop layer by a predetermined thickness. Forming a layer, patterning the sacrificial layer into a predetermined shape, and stacking the sacrificial layer and an insulating material having high resistance to etching liquid on the etch stop layer exposed by the patterning of the sacrificial layer by a low temperature process Forming the membrane, and driving the membrane through the membrane, the sacrificial layer, the etch stop layer, and passivation. Forming a via hole exposing the contact metal provided in the plate, attaching a conductive material to the via hole to form a plug metal, and forming a lower electrode, a deformable part, and an upper electrode on the membrane where the plug metal is formed. Stacking sequentially to form an actuator; patterning the upper electrode, the deformable portion, the lower electrode, and the membrane constituting the actuator into a predetermined shape; and coating the entire surface of the actuator with a material resistant to an etchant. A method of manufacturing a thin film type optical path control device comprising a step of forming an etch protective layer and a step of removing the sacrificial layer.

On the other hand, in a preferred embodiment of the present invention, the etching stop layer provides a method for manufacturing a thin film type optical path control device, characterized in that the amorphous silicon.

On the other hand, in a preferred embodiment of the present invention, the etch stop layer provides a method for manufacturing a thin film type optical path control apparatus, characterized in that formed by a plasma chemical vapor deposition (PECVD) process.

On the other hand, in a preferred embodiment of the present invention, the plasma chemical vapor deposition (PECVD) process provides a method of manufacturing a thin film type optical path control apparatus, characterized in that carried out at 450 ℃ or less.

On the other hand, in a preferred embodiment of the present invention, the membrane provides a method of manufacturing a thin film type optical path control device, characterized in that the amorphous silicon.

On the other hand, in a preferred embodiment of the present invention, the membrane provides a method of manufacturing a thin film type optical path control apparatus, characterized in that formed by a plasma chemical vapor deposition (PECVD) process.

On the other hand, in a preferred embodiment of the present invention, the plasma chemical vapor deposition (PECVD) process provides a method of manufacturing a thin film type optical path control apparatus, characterized in that carried out at 450 ℃ or less.

1 is a cross-sectional view showing a unit pixel of a general thin film type optical path control device.

2A to 2J are flowcharts sequentially showing a method of manufacturing a thin film type optical path control device according to the present invention.

<Description of the code | symbol about the principal part of drawing>

100; A driving substrate 110; Silicon substrate

120; Passivation layer 130; Etch stop layer

105; Contact metal 200; Actuator

205; Plug metal 210; Membrane

220; Lower electrode 230; Deformation part

240; Upper electrode 250; Sacrificial layer

260; Etching protection layer

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

Hereinafter, with reference to the accompanying drawings, a preferred embodiment of the present invention will be described in detail as follows and the same configuration as the general thin film type optical path control device shown in Figure 1 uses the same reference numerals.

1 is a cross-sectional view illustrating a unit pixel of a general thin film type optical path control device, and FIGS. 2A to 2J are process diagrams sequentially illustrating a method of manufacturing a thin film type optical path control device according to the present invention.

First, a method of manufacturing a thin film type optical path control apparatus according to the present invention includes a silicon substrate on which a plurality of active elements (not shown) formed of a transistor such as MOS are formed on a silicon substrate 110 by a semiconductor integrated circuit manufacturing process ( Phosphosilicate Glass (PSG) or Boro-Phosphosilicate (PSG) or Phosphosilicate Glass (PSG) to prevent the plurality of active devices from being subjected to chemical or physical damage from outside under the high temperature atmosphere of the subsequent deposition process performed on 110). Glass is deposited by Chemical Vapor Deposition (hereinafter, referred to as CVD) to form a passivation layer 120, and the protective layer 120 is an etching solution, for example, hydrofluoric acid (HF), in a subsequent etching process. Corrosion resistance to hydrofluoric acid (HF) solution on the protective layer 120 to prevent exposure to the solution to chemical damage By forming a etch stop layer 130 by laminating a good amorphous silicon (Amorphous-Silicon) to a predetermined thickness by a deposition process such as plasma chemical vapor deposition (PECVD) at 450 ℃ or less (more preferably 400 ℃ or less) The driving substrate 100 is prepared.

Thereafter, phosphorus-containing silicon oxide (PSG) or polycrystalline silicon is deposited on the driving substrate 100 to a predetermined thickness by physical vapor deposition (PVD) or chemical vapor deposition (CVD). After the sacrificial layer 250 is formed, the sacrificial layer 250 is formed into a predetermined shape having a pattern having a predetermined line width as shown in FIG. 2B by a fine pattern forming process. As a result, a part of the driving substrate 100 exposed through the pattern of the sacrificial layer 250 is provided as a place for forming the support portion and the bridge of the actuator 200.

As described above, the etch stop layer of the sacrificial layer 250 having a predetermined width on the driving substrate 100 and the pattern of the sacrificial layer 250 exposed through patterning of the sacrificial layer 250 ( Amorphous-Silicon (Amorphous-Silicon) not only has good insulating properties but also has good resistance to etching solutions such as hydrofluoric acid (HF) solution, is plasma-chemical vapor deposition at 450 ° C or below (more preferably 400 ° C or below). After the membrane 210 is formed to a predetermined thickness by a deposition process such as PECVD, as shown in FIG. 2C, the membrane 210 is embedded in the driving substrate 100 by a via hole forming process. Via holes for exposing the metal pads 105 electrically connected to the active elements (not shown) are formed as shown in FIG. 2D.

Subsequently, a lower electrode to be formed by a subsequent process by mounting a metal having conductive platinum (Pt), titanium (Ti), or tantalum (Ta) in a process such as lift-off, etc. in the via hole. A plug metal 205 that can be electrically conductive with 220 is formed as shown in FIG. 2E.

In addition, a conductive metal having good conductivity such as platinum (Pt) or detanium (Ta) is deposited on the membrane 210 and the plug metal 205 to a predetermined thickness by a vacuum deposition process such as a sputtering deposition process. The lower electrode 220 is formed and the lower electrode 220 is driven by the plug metal 205 connected from the membrane 210 to the metal pad 105 of the driving substrate 100 as described above. The lower electrode 220 is electrically connected to a plurality of active elements embedded therein, and the lower electrode 220 forms a lower electrode 220 that is formed in a predetermined shape by a subsequent etching process and operates as a signal electrode.

In this case, anisotropic etching of a portion of the lower electrode 220, part of the lower electrode 220 constituting a bridge (not shown) of the actuator 200, which is formed in a predetermined shape, is performed like a reactive ion etching process (RIE). It is removed by a dry etching process having good characteristics to form an iso cutting part (IC) for separating the electric signal flowing into the lower electrode 220 through the plurality of active elements in units of pixels.

Subsequently, a portion of the membrane 210 exposed through the iso cutting part (not shown) and a ceramic material exhibiting piezoelectric characteristics are stacked on the lower electrode 220 to a predetermined thickness by a deposition process to form a deformation part ( The ceramic material forming the deformable portion 230 is formed of BaTiO ₃ , Pb (Zr, Ti) O ₃ , (Pb, La) (Zr, Ti) O ₃ , or a piezoelectric ceramic or Pb (Mg, Nb) O _{3 is} composed of a whole-distortion ceramic and the deposition process is formed by a sputtering deposition process or a chemical vapor deposition process or a sol-gel process.

As described above, the deformable portion 230 formed by laminating to a predetermined thickness is heat-treated by a high temperature heat treatment process, in particular, Rapid Thermal Annealing, and as a result, the crystal of the ceramic composition constituting the deformable portion 230 is determined. By forming the structure into a Perovskite crystal structure, the deformable portion 230 exhibits good piezoelectric properties.

Subsequently, aluminum (Al) or platinum (Pt) and titanium having good electrical conductivity as well as good reflective properties by physical vapor deposition (PVD) or chemical vapor deposition (CVD) on the deformable portion 230. The upper electrode 240 is formed by depositing a metal such as (Ti) to a predetermined thickness, and the upper electrode 240 serves as a common electrode for tilting the driving unit of the actuator 200 formed in a predetermined shape, as well as reflecting characteristics. Acts as a reflective surface.

As shown in FIG. 2F by the multi-step process as described above, the actuator 200 formed of a plurality of layers sequentially stacked on the driving substrate 100 is formed, and the plurality of actuators constituting the actuator 200 are formed. The layers are then patterned as shown in FIG. 2G by an etching process performed thereafter to form an actuator 200 of a predetermined shape, thereby exposing a portion of the sacrificial layer 250.

As described above, the etching process for forming a part of the plurality of layers stacked on the driving substrate 100 into a predetermined shape constituting the actuator 200 may be a dry etching process having good anisotropic etching characteristics, for example, reactive ions. It is performed by an etching (RIE) process, and this reactive ion etching (RIE) process is performed by the etching action of an etchant composed of CF ₄ or CHF ₃ under oxygen plasma.

Meanwhile, in order to form the actuator 200 having a predetermined shape as described above, the cantilever structure, the sacrificial layer 250 remaining in the predetermined shape on the driving substrate 100 may be removed by an etching process. In order to prevent the side surface of the actuator 200 from being exposed to the etching solution to prevent the plurality of layers constituting the actuator from peeling off, an etching protection film 260 is formed on the outer surface of the actuator 200 as shown in FIG. 2H. To form.

In this case, the etch protection layer 260 is formed by applying an insulating material to a predetermined thickness on the outer surface of the actuator 200 to completely block the exposed portion formed on the membrane 210 from the outside. The insulating material constituting 260 is made of a polymer having good corrosion resistance to an etching solution, particularly a hydrofluoric acid (HF) solution, used in an etching process.

Meanwhile, although the sacrificial layer 250 exposed through the pattern of the actuator 200 is removed as shown in FIG. 2I by an etching process in which isotropic etching characteristics are good, the etch stop layer 130 is not damaged. Since the passivation layer 120 is well maintained, the active element is well protected, and the etching solution used in the etching process has an etching characteristic of silicon oxide (PSG) containing phosphorus constituting the sacrificial layer. It consists of a good hydrofluoric acid (HF) solution.

Subsequently, the etch protection layer 260 remaining on the upper electrode 240 of the actuator 200 by a predetermined thickness by a dry etching process such as an ion milling process is removed as shown in FIG. 2J to remove the upper electrode ( 240 may be exposed to act as a reflective surface of the mirror array.

The thin film type optical path control device manufactured as shown in FIG. 2 through a multi-step process as described above is used to control the actuator 200 through an active element embedded in the driving substrate 100 from an external control system. When an electrical signal is applied to the upper electrode 240, a potential difference of a predetermined magnitude is generated between the lower electrode 220 and the upper electrode 240, and the deformation part 230 represents piezoelectric deformation due to the occurrence of the potential difference. As a result, the plurality of actuators 200 are individually driven.

That is, the white light of the light source incident on the surface of the upper electrode 240 serving as the reflective surface is reflected along the optical path changed by the driving of the actuator 200 to display an image on a screen not shown.

The foregoing has merely described a preferred embodiment of the present invention with reference to the accompanying drawings, and those skilled in the art can make modifications and changes to the present invention without changing the gist of the invention described in the claims. Can be.

As described above, according to the present invention, the etching stop layer and the membrane are formed of amorphous silicon by a plasma chemical vapor deposition (PECVD) process at a low temperature of 450 ° C. or lower, thereby generating out-gassing and interdiffusion phenomenon according to a conventional high temperature process. It is possible to improve the reliability and performance of the thin film type optical path control device by preventing problems such as intermetallic compound formation and destruction of MOS structure.

Claims (7)

In the manufacturing method of the thin film type optical path control apparatus used as a projection image display apparatus, Forming a passivation layer by stacking an insulating material on top of a silicon substrate having an active element in a matrix form; Forming an etch stop layer by stacking an insulating material having high resistance to an etchant in a low temperature process on top of the passivation layer; Forming a sacrificial layer by laminating an insulating material to a predetermined thickness on an upper portion of the etch stop layer; Patterning the sacrificial layer into a predetermined shape; Forming a membrane by laminating a sacrificial layer and an insulating material having high resistance to an etchant in a low temperature process on the etch stop layer exposed by patterning the sacrificial layer; Forming a via hole through the membrane, the etch stop layer, and passivation to expose the contact metal provided on the driving substrate; Attaching a conductive material to the via hole to form a plug metal; Forming an actuator by sequentially stacking a lower electrode, a deformation part, and an upper electrode on the membrane on which the plug metal is formed; Patterning the upper electrode, the deformable portion, the lower electrode, and the membrane constituting the actuator into a predetermined shape; Forming an etch protective layer by coating the entire surface of the actuator with a material resistant to an etching solution; Removing the sacrificial layer; Removing the etch protective layer applied to the front surface of the actuator Method of manufacturing a thin film type optical path control device consisting of. The method of claim 1, The etching stop layer is a method of manufacturing a thin film type optical path control device, characterized in that the amorphous silicon. The method according to claim 1 or 2, The etch stop layer is a plasma chemical vapor deposition (PECVD) process characterized in that the manufacturing method of the thin film type optical path control device. The method of claim 3, wherein The plasma chemical vapor deposition (PECVD) process, the manufacturing method of the thin film type optical path control apparatus, characterized in that carried out at 450 ℃ or less. The method of claim 1, The membrane is a method of manufacturing a thin film type optical path control device, characterized in that the amorphous silicon. The method according to claim 1 or 5, And the membrane is formed by a plasma chemical vapor deposition (PECVD) process. The method of claim 6, The plasma chemical vapor deposition (PECVD) process, the manufacturing method of the thin film type optical path control apparatus, characterized in that carried out at 450 ℃ or less.