KR20000004135A - Method for manufacturing a thin film actuated mirror array - Google Patents

Abstract

PURPOSE: A method for manufacturing a thin film actuated mirrors array in an optical projection system is provided to increase light efficiency by forming a mirror having a planar top surface at the thin film actuated mirror structured two layers. CONSTITUTION: The method for manufacturing a thin film actuated mirrors array comprising the step of: preparing a driving substrate (410) including a insulating substrate, MOS transistor, and a drain pad; forming a first sacrificial layer (490), which a support portion is formed on the driving substrate; forming an actuator (510), which a membrane (520), a lower electrode (450), a deformable layer (530), an upper electrode (550) and an electron tube (565) are formed onto the first sacrificial layer and the support layer; forming a post (570) onto separated portion of the driving substrate of the actuator; forming a second sacrificial layer (580) onto the actuator; and removing the first and second sacrificial layer

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 of manufacturing a thin film type optical path control apparatus having a flat upper surface and increasing light efficiency. In particular, a second sacrificial layer having a post having the same material as the mirror and having a thickness equal to the height of the post After forming the present invention, the present invention relates to a method for manufacturing a thin film type optical path control device array having a two-layer structure.

In general, a spatial light modulator, which is an apparatus for projecting optical energy onto a screen, may be variously applied to optical communication, image processing, and information display apparatus. Such devices are classified into a direct view type image display device and a projection type image display device according to a method of projecting a light beam incident from a light source onto a screen. CRT (Cathod Ray Tube) is a direct type image display device, and liquid crystal display (hereinafter referred to as LCD), DMD (Deformable Mirror Device), or AMA (Actuated) is a projection type image display device. Mirror Arrays).

The above-described CRT apparatus is an excellent display apparatus which is guaranteed an average brightness of 100 ft-L (white display) or more, a contrast ratio of 30: 1 or more, a lifetime of 10,000 hours or more. However, since the CRT has a large weight and volume and maintains high mechanical strength, it is difficult to make the screen completely flat, which causes distortion of the peripheral part. In addition, since CRTs excite phosphors with an electron beam to emit light, there is a problem that a high voltage is required to produce an image.

Therefore, LCDs have been developed to solve the above-mentioned problems of CRT. The advantages of such LCDs are explained in comparison with CRTs. LCDs operate at low voltages, consume less power, and provide images without distortion.

However, despite the advantages described above, the LCD has a low light efficiency of 1 to 2% due to the polarization of the light beam, and there is a problem that the response speed of the liquid crystal material therein is slow.

Accordingly, devices such as DMD or AMA have been developed to solve the problems of LCD as described above. 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 mirror 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 the actuator, electrodistorted ceramics such as PMN (Pb (Mg, Nb) O ₃ ) may be used.

1A to 1F are cross-sectional views illustrating a manufacturing method of a conventional two-layer thin film type optical path control apparatus 100. As shown in FIG. 1A, the two-layer thin film type optical path control apparatus 100 is illustrated. ), The insulating substrate 112, the MOS transistor 120, the diffusion barrier layer 130, the metal layer 140, the lower protective layer 150, the blocking layer 160, the upper protective layer 170, the etch stop layer It starts with preparation of the drive board 110 in which 180 etc. are formed.

In the driving substrate 110, the MOS transistor 120 includes a gate oxide layer 121, a gate electrode 122, an interlayer insulating layer 123, a source region 124, a drain region 125, and a field oxide layer 126. ) Is formed. The diffusion barrier layer 130 prevents the silicon of the insulating substrate 112 from diffusing into the metal layer 140. The metal layer 140 may include drain pads 142 and source regions 124 formed to transmit electrical signals applied from the drain region 125 of the transistor 120 to respective actuators 210, which will be described later. It is formed of a portion 144 for electrically connecting. The lower protective layer 150 is formed to prevent the blocking layer 160 and the metal layer 140 from being electrically connected to each other. The blocking layer 160 is formed in order to prevent the photocurrent generated by the photoelectric effect from occurring in the metal layer 140 formed thereunder. The upper protective layer 170 is formed to protect the blocking layer 160 and the MOS transistor 120 from being damaged during subsequent manufacturing processes. The etch stop layer 180 is formed to prevent the driving substrate 110 from being damaged during the subsequent etching process.

Subsequently, as shown in FIG. 1B, a first sacrificial layer 190 made of polycrystalline silicon (poly-Si) material is formed on the driving substrate 110 using low pressure vapor deposition (LPCVD). Here, in order to increase the flatness on the upper surface of the first sacrificial layer 190, it is planarized by using spin on glass (SOG) or chemical mechanical polishing (CMP). Subsequently, a portion 195 in which the supporting portion of the actuator 210 to be described later is formed is etched by etching the portion formed on the drain pad 142 of the first sacrificial layer 190.

Subsequently, as illustrated in FIG. 1C, a material having excellent electrical conductivity such as a membrane 220 made of nitride, platinum (Pt), or platinum / tantalum (Pt / Ta) is formed on the first sacrificial layer 190. The lower electrode 230 made of a piezoelectric material such as PZT or PLZT, the upper electrode 250 made of the same material as the lower electrode 230, the lower electrode 230 and the drain pad 142 An electric tube 265 connected to each other forms an actuator 210 formed in this order.

Here, looking at the manufacturing process of the actuator 210, first, the membrane 220 made of nitride is formed to a thickness of 0.1 ~ 1.0㎛ using a low pressure chemical vapor deposition (LPCVD) method.

Next, a lower electrode 230 made of a metal having excellent electrical conductivity is formed on the membrane 220 to a thickness of 0.1 μm to 1.0 μm using a sputtering method.

Next, a strain layer 240 made of a piezoelectric material such as PZT or PLZT is formed on the lower electrode 230 to have a thickness of 0.1 μm to 1.0 μm using a sputtering or chemical vapor deposition (CVD) method. Subsequently, the strained layer 240 is phase shifted using a rapid heat treatment (RAT) method.

Subsequently, an upper electrode 250 made of a material having the same excellent electrical conductivity as that of the lower electrode 230 is formed on the deformation layer 240 by using a sputtering method.

Thereafter, the upper electrode 250, the strained layer 240, the lower electrode 230, and the membrane 220 are patterned in a desired shape by using a photoresist so as to be divided into respective actuators in a cell unit. The upper electrode 250, the strained layer 240, the lower electrode 230, the membrane 220, the etch stop layer 180, the upper passivation layer 170, and the lower passivation layer are formed from the drain pad 142. After etching 150 to form a via hole 260, a metal such as tungsten (W), platinum (Pt), aluminum (Al), or titanium (Ti) is formed in the via hole 260. The front tube 265 is formed to electrically connect the lower electrode 230 and the drain pad 142 using a sputtering method.

Subsequently, as shown in FIG. 1D, a second sacrificial layer 270 made of insulated glass (PSG) is formed on the actuator 210 by using an atmospheric chemical vapor deposition (APCVD) method. Then, the second sacrificial layer 270 is partially etched to form a support portion 280 of the mirror so that the mirror 310 to be formed later can be supported by the actuator 210.

Next, as shown in FIG. 1E, a material having excellent reflection characteristics is deposited on the second sacrificial layer 270 and the support portion 280 of the mirror by the sputtering method, and then each actuator 210. The mirror 310 is formed by dicing one-to-one correspondence.

Finally, as shown in FIG. 1F, the ASA device is completed by removing the second sacrificial layer 270 and the first sacrificial layer 190.

However, in the conventional two-layer thin film type optical path control apparatus, in order to support the mirror 310 on the actuator 210, the second sacrificial layer 270 is partially etched to remove the support portion 280 of the mirror. And by forming a mirror 310 by depositing a material having excellent reflection properties thereon, the mirror portion formed on the support portion 280 of the mirror is formed while forming a step with another portion of the mirror 310, Accordingly, there is a problem that the light efficiency of reflecting light from the light source is reduced.

The present invention has been made to solve the conventional problems as described above, the thin film type optical path control apparatus according to the present invention, as described above, supports the mirror to the actuator with the same material as the mirror before forming the second sacrificial layer. A second sacrificial layer having a thickness equal to the height of the post and having a flat upper surface on the upper part of the actuator, and then forming a mirror on the second sacrificial layer and the upper part of the post, It is to provide a method of manufacturing a thin film optical path control device having a two-layer structure to form a mirror without, thereby increasing the overall light efficiency.

In order to achieve the object described above, the present invention provides an insulating substrate, a MOS transistor, a diffusion barrier layer, a metal layer consisting of a drain pad and a source connection portion, a lower protective layer, a blocking layer, an upper protective layer, an etch stop layer, and the like. Preparing a driving substrate; Forming a first sacrificial layer having a support formed on the driving substrate; Forming an actuator having a membrane, a lower electrode, a strained layer, an upper electrode, an electric tube, and the like formed on the first sacrificial layer and the support part; Forming a post on each of the actuators; Forming a second sacrificial layer on the actuator, the second sacrificial layer having a flat upper surface at the same thickness as the height of the posts; ; Forming a mirror on top of the post and the second sacrificial layer; Removing the second sacrificial layer and the first sacrificial layer.

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.

1A to 1F are cross-sectional views illustrating a method for manufacturing a conventional thin film type optical path control device;

2A to 2H are cross-sectional views illustrating a method for manufacturing a thin film type optical path control device according to the present invention.

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

410: driving substrate 420: MOS transistor 430: diffusion barrier layer

440: metal layer 450: lower protective layer 460: blocking layer

470: upper protective layer 480: etch stop layer 490: first sacrificial layer

510: actuator 520: membrane 530: lower electrode

540: strained layer 550: upper electrode 565: electric tube

570: post 580: second sacrificial layer 590: photoresist

610: mirror

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

2A to 2H are cross-sectional views illustrating a method of manufacturing a thin film optical path control apparatus 400 having a two-layer structure in accordance with the present invention. As shown in FIG. 2A, the thin film optical path control apparatus having a two-layer structure is shown. The insulating layer 412, the MOS transistor 420, the diffusion barrier layer 430, the metal layer 440, the lower protective layer 450, the blocking layer 460, and the upper protective layer 470 may be etched. It starts with preparation of the drive board 410 in which the prevention layer 480 etc. are formed.

In the driving substrate 410, the MOS transistor 420 includes a gate oxide layer 421, a gate electrode 422, an interlayer insulating layer 423, a source region 424, a drain region 425, and a field oxide layer 426. ) Is formed. The diffusion barrier layer 430 prevents the silicon of the insulating substrate 412 from diffusing into the metal layer 440. The metal layer 440 is a drain pad 442 and a source region 424 formed to transmit an electrical signal applied from the drain region 425 of the transistor 420 to each actuator 510 to be formed later. Are formed as a portion 444 for electrically connecting the plurality of electrodes. The lower protective layer 450 is formed to prevent the blocking layer 460 and the metal layer 440 from being electrically connected to each other. The blocking layer 460 is formed to prevent photocurrent caused by a photoelectric effect on the metal layer 440 formed under the blocking layer 460. The upper protective layer 470 is formed to protect the blocking layer 460 and the MOS transistor 420 from being damaged during subsequent manufacturing processes. The etch stop layer 480 is formed to prevent the driving substrate 410 from being damaged during the subsequent etching process.

Subsequently, as shown in FIG. 2B, a first sacrificial layer 490 made of polycrystalline silicon (poly-Si) material is formed on the driving substrate 410 by using low pressure vapor deposition (LPCVD). Here, in order to increase the flatness on the upper surface of the first sacrificial layer 490, it is planarized by using spin on glass (SOG) or chemical mechanical polishing (CMP). Subsequently, a portion 495 is formed on the drain pad 442 of the first sacrificial layer 490 to etch the portion to form a support portion of the actuator 510.

Subsequently, as illustrated in FIG. 2C, a material having excellent electrical conductivity such as a membrane 520, platinum (Pt), or platinum / tantalum (Pt / Ta) made of nitride on the first sacrificial layer 490 is formed. The lower electrode 530, the strained layer 540 made of piezoelectric material such as PZT or PLZT, the upper electrode 550 made of the same material as the lower electrode 530, the lower electrode 530 and the drain pad 442 are electrically An actuator 510 having an electric tube 565 or the like connected thereto is formed.

Here, looking at the manufacturing process of the actuator 510, first, the membrane 520 made of nitride is formed to a thickness of 0.1 ~ 1.0㎛ using a low pressure chemical vapor deposition (LPCVD) method.

Next, a lower electrode 530 made of a metal having excellent electrical conductivity is formed on the membrane 520 to a thickness of 0.1 to 1.0 μm using a sputtering method.

Next, a strain layer 540 made of a piezoelectric material such as PZT or PLZT is formed on the lower electrode 530 to have a thickness of 0.1 to 1.0 μm using a sputtering or chemical vapor deposition (CVD) method. Subsequently, the strained layer 540 is phase shifted using a rapid heat treatment (RAT) method.

Subsequently, an upper electrode 550 made of a material having the same excellent electrical conductivity as that of the lower electrode 530 is formed on the deformation layer 540 by using a sputtering method.

Thereafter, the upper electrode 550, the strained layer 540, the lower electrode 530, and the membrane 520 are patterned in a desired shape by using a photoresist so as to be divided into respective actuators in units of cells. The upper electrode 550, the strained layer 540, the lower electrode 530, the membrane 520, the etch stop layer 480, the upper protective layer 470, and the lower protective layer are formed from the portion where the drain pad 442 is formed. After the 450 is sequentially etched to form a via hole 560, a metal such as tungsten (W), platinum (Pt), aluminum (Al), or titanium (Ti) is formed in the via hole 560. The front tube 565 is formed to electrically connect the lower electrode 530 and the drain pad 442 using a sputtering method.

Subsequently, as shown in FIG. 2D, the post 570 is formed on the upper portion of the actuator 510 spaced apart from the driving substrate 410 by using the same material as the mirror to be formed later. The post 570 is formed by depositing a material such as aluminum (Al), which is used to form the mirror 610 having a high reflection property, above the actuator 510 by a sputtering method over a predetermined thickness. Thereafter, a post 570 having a predetermined height is formed by removing by using an etching method so that only the part spaced apart from the driving substrate 410 of the actuator 510 is removed.

Next, as shown in FIG. 2E, the second sacrificial layer 580 made of poly-silicon (poly-Si) on the actuator 510 and having a thickness greater than or equal to a predetermined height of the post 570 is atmospheric pressure. Deposition is carried out using chemical vapor deposition (LPCVD). Then, the photoresist 590 is coated on the second sacrificial layer 580 to a predetermined thickness or more.

Next, as shown in FIG. 2F, portions of the photoresist 590 and the second sacrificial layer 580 are etched by using an etch-back method, so that the thickness of the post 570 is increased. A second sacrificial layer 580 is formed that is the same as the height of the upper surface 585 is flat.

Next, as shown in FIG. 2G, on the flat top surface 585 of the second sacrificial layer 580 and the top of the post 570, a material such as aluminum (Al), which is the same material as the post 570. Is deposited using a sputtering method, and then diced to correspond to each actuator 510 one-to-one to form a mirror 610.

Finally, as shown in FIG. 2H, the ASA device is completed by removing the second sacrificial layer 580 and the first sacrificial layer 490.

As described above, the thin film type optical path adjusting device according to the present invention forms a post for supporting the mirror on the actuator with the same material as the mirror before forming the second sacrificial layer, and then has the same height as that of the post on top of the actuator. By forming a second sacrificial layer having a thickness and having a flat upper surface, and then forming a mirror on the second sacrificial layer and the top of the post, a mirror having no step is formed, thereby increasing the overall light efficiency.

As described above, although the present invention has been described with reference to the drawings, those skilled in the art may variously modify and change the present invention without departing from the spirit and scope of the invention as set forth in the claims below. It will be appreciated.

Claims (3)

Preparing a driving substrate on which an insulating substrate, a MOS transistor, and a drain pad are formed; Forming a first sacrificial layer having a support formed on the driving substrate; Forming an actuator having a membrane, a lower electrode, a strained layer, an upper electrode, an electric tube, and the like formed on the first sacrificial layer and the support part; Forming a post on an upper portion of the actuator substrate spaced apart from the driving substrate; Forming a second sacrificial layer on top of the actuator; Forming a mirror on top of the post and the second sacrificial layer; Method of manufacturing a thin film type optical path control device comprising the step of removing the second sacrificial layer and the first sacrificial layer. The method of claim 1, wherein the post is formed of the same material as the mirror. The method of claim 1, wherein the second sacrificial layer is formed by first depositing a second sacrificial layer made of polycrystalline silicon on top of the actuator, and coating the second sacrificial layer with the photoresist thereon. The method of claim 2, wherein the second sacrificial layer is formed by etching back the resist until the post is exposed.