KR100270812B1 - Movable micro mirror for a video display apparatus and manufacturing method therefor - Google Patents

Abstract

PURPOSE: A method for manufacturing a moving micro mirror for an image display device is provided to prevent the strength of a joint hinge from being weakened and reduce the number of masks necessary for a mask process. CONSTITUTION: A pin member(12b) is formed on a substrates(11), and a top sacrifice layer is formed reusing the first mask. When forming an opening, the opening is formed by use of the pin member(12b) as a mask. A staple member(20) is formed as the second mask(24) at the second structure. After forming the staple member(20), a post-film sacrifice layer and an opening for forming a pillar member are formed on the staple member(20). After forming the staple member(20), The moving is provided to the pin member, the staple member(20), and the structure.

Description

Movable micro mirror for image display device and manufacturing method thereof

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a micromirror for a projection image display device constituting a large-scale image display or a television, a computer, a head mounted personal projection image display device, and a method of manufacturing the same. The present invention relates to a movable micro mirror for an image display device in which the projection direction of an image changes as the reflecting surface contacts left and right about its axis.

The most essential component of the projection image display device is a micro mirror array chip that displays an image by reflecting light pixel by pixel. Currently, micromirror array chips are known as electrostatically driven micromirrors and piezoelectrically driven micromirrors.

In the present invention, the above-mentioned electrostatic driving micro mirror array chip will be described.

That is, the electrostatically-driven micromirror array chip is a structure in which mirrors are manufactured two-dimensionally as many as the number of pixels, and each mirror is reflected according to a signal of a pixel of an image to adjust color and brightness.

Such mirrors generally have a reflector which forms a reflecting surface for reflecting light, and secures an inclination angle by dropping the reflector from the substrate, and is located between the pillar member for supporting the reflector, the reflector and the pillar member, and tilts with elastic force. The paper consists of a flexure hinge. The lower surface of each mirror includes a driver for driving the mirror and a drive circuit for controlling the drive signal.

A micromirror for a projection image display device having such a structure is disclosed in US Pat. No. 5,083,857.

The micromirror for a projection image display device known by this patent publication operates as follows.

That is, when a voltage is applied to the electrode fabricated below the reflector, that is, on the substrate, and a potential difference is generated between the reflector and the electrode, electrostatic attraction occurs to generate a torque that pulls the reflector toward the electrode and rotates the mirror hinge about its axis. If this torque value is greater than the restoring force by the torsion spring of the flexure hinge, the reflector is tilted. If this value is greater than a certain threshold, the reflector continues to tilt and touch the substrate. At this time, when the reflected light enters the screen, the switch is on, and when the light is inclined to the opposite side, the switch is turned off. The brightness and color are controlled by adjusting the on / off state of the switch. This is called a digital method.

In the accompanying drawings, Figure 1 shows a structure in which the structure connected to the pin member can be rotated by archiving the pin member as a bearing member, and FIG. 2 is a manufacturing process diagram for manufacturing the same.

The manufacturing process of a conventionally known micromirror according to this figure is as follows.

First, a sacrificial layer 201 is formed on a substrate 200 of a silicon wafer. The sacrificial layer 201 is a portion to be removed when the microstructure is completed, and materials such as PSG (phophosilicate glass) and low temperature oxide (LTO) are used, and polysilicon is used as the structure.

Subsequently, the pattern is transferred to the first mask on the sacrificial layer 201 to form a polysilicon structure and a fin member (see FIG. 2A).

When the pin member 203 is formed, an upper sacrificial layer 205 is formed thereon (see FIG. 2B).

When the upper sacrificial layer 205 is deposited, the second sacrificial layer 205 is etched to form the recess 207. In this case, the secondary mask 206 is manufactured separately in a pattern different from the primary mask 204 (see FIG. 2C).

Subsequently, polysilicon is formed on the entire top surface of the upper sacrificial layer 205 and the concave portion 207 after the patterning process so as to form a bearing member 208 attached to the bottom substrate 200 surface of the concave portion 207. Deposit structure 209 (see FIG. 2D).

On the upper surface of the polysilicon structure 209 is deposited, pattern masking is performed again with the tertiary mask 210 to form the bearing member 208 (see FIG. 2E).

Then, by removing the upper and lower sacrificial layers 201 and 205 by etching, the two bottom surfaces of the bearing member 208 are attached to the concave portion 207 to support the pin member 203 therein. See FIG. 2F)

Of course, the pin member 203 is formed together with the structure 202 and becomes an integral pin member 203 and is elastically movable to the left and right sides while being supported from the inside of the bearing member 208. .

Since the movable micro mirror having the hinge structure is driven by mechanical deformation of the hinge portion, there is a problem in that the strength of the connecting portion such as the hinge portion of the reflector is reduced.

Since the wet etching is performed upon removal of the sacrificial layer, PSG and LTO, which are the material of the sacrificial layer, cause a problem that the movable structure adheres to the substrate by the tension of the etchant, thereby increasing the defect rate of the micromirror.

In particular, in the above process, first, the process of forming the fin member, second, when forming the recess in the upper and lower sacrificial layer, third, when manufacturing the water-reducing member, such as staples, three masks for mask patterning were required. Each process mask for mask patterning requires a separate high-level manufacturing process, so if you perform this process for each process, problems related to the requirements of the high-level process for each mask production and economic problems due to the increase in the number of masks There was this.

Therefore, there is a need for a joint structure of a micro mirror capable of improving the strength of the joint structure and the hinge portion of the joint structure. Therefore, there has been a need for strengthening the material of the hinge function, and it has been required to improve the etching process in which the movable structure does not adhere to the substrate during etching by avoiding wet etching performed to remove the sacrificial layer. .

In addition, the mask patterning process to form a fin member in the above-described process, to form a recess in the upper and lower sacrificial layers, and to reuse the mask without preparing a separate mask for forming the respective patterns when manufacturing the bearing member. This was needed.

The present invention is to improve the strength of the joint structure and the hinge portion of the joint structure in consideration of the structural problems of the joint structure of the conventional projection-type image display micro mirror, and the problems and needs of the manufacturing process. There is this.

In addition, the sacrificial layer also has an object of improving the etching process in which the movable structure does not adhere to the substrate during etching, and the pin member is formed in the process of the joint structure, and the recesses are formed in the upper and lower sacrificial layers. It is also an object of the present invention to provide a manufacturing process of a micro-mirror that can reduce the number of mask manufacturing process that requires a highly separate process if possible in the mask patterning process for each etching when manufacturing the bearing member.

1 is a perspective view of a structure having a pin member and a bearing member

2 (a) to 2 (f) is a conventional manufacturing process diagram for manufacturing the same

3 (a) to 3 (g) are process drawings of the present invention for producing a micromirror having the flexure hinge of FIG.

Figure 4 (a) to Figure 4 (g) is a micro mirror manufacturing process diagram of another embodiment of the present invention

FIG. 5 is an exemplary view of a micro mirror for reflecting surfaces having a fin member and a pillar member of FIG.

※ Explanation of symbols for main parts of drawing

11: substrate ..... 12: first structure

12a: Structure ... 12b: Pin member

13: First victim layer ............ 14: First mask

15: first mask pattern ..... 16: recess

20: Staple member ........ 21: 2nd victim layer

22: second structure ...... 23: recessed part

24: 2nd mask ........ 100: Substrate

101: insulating layer ... 102: electrode

103: first victim layer ............ 104: structure

105: mask pattern ..... 106: pin member

107: second victim layer ............ 108: bearing member

109: thick film sacrificial layer ..... 110

111: fourth structure ...... 112: pillar member

113: reflector

The present invention for achieving the above object, at least three electrodes formed on the substrate; A bearing member formed on one of the center electrodes of the electrode; a pin member rotatably supported by the bearing member; A pillar member extending upward from the pin member; And a reflector for floating on an upper surface of the substrate depending on the pillar member, the upper surface of which includes a reflector for forming a reflecting surface to be driven by electrostatic force on the left and right opposing electrodes of the electrodes. Has its features.

The present invention having the above characteristics comprises the steps of forming a pin member obtained by forming a sacrificial layer on the lower surface of the first structure on the substrate of the silicon wafer as a first mask pattern; An upper sacrificial layer patterning process of removing the sacrificial layers except for the lower portions of the structures in the fin member forming step, and then forming another concave layer using the mask of the process to form recesses; Forming a second structure in a state including the recess and the sacrificial layer, and then forming a pattern as a second mask to form a bearing member; And a reflector forming step of etching the upper and thick film sacrificial layers of the fin member as a third mask.

The present invention of the above structure and process comprises the steps of depositing a first metal film on a silicon wafer and forming an electrode as a first mask; Forming a fin member with a second mask by forming a second metal film on the lower sacrificial layer in a state including the electrode; Forming a second sacrificial layer after removing the lower sacrificial layer in the fin member forming step, forming a recess in the second sacrificial layer by using the mask again, and forming a thick film sacrificial layer in the bearing member forming step; And forming a pillar member forming hole in a substantially central portion of the thick film sacrificial layer; And depositing a metal film on the thick film sacrificial layer, forming a support and a reflective surface, and removing the lower portion of the fin member and the thick film sacrificial layer.

In the above process, the present invention further includes an insulating layer forming step before forming the metal film on the silicon wafer in the forming of the electrode, and the etching process of forming the fin member is performed by excessive etching. The pattern of the mask used in the fin member etching process may be reused as it is during the formation of the second sacrificial layer in the forming of the water bearing member, and the etching process for removing the lower portion and the thick film sacrificial layer of the fin member may be dry. Most preferably, the etching process is performed, and in particular, a metal is used to form the structures constituting the electrodes, the fin member, the reflector, and the support shaft.

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

Example 1.

3 (a) to 3 (e) of the accompanying drawings is a process diagram of the present invention applied to manufacture the structure of Figure 1, according to the present invention, the invention is largely a pin member forming step, a bearing member (staple) and a reflector It consists of a forming step.

(First process)

As shown in FIG. 3A, the first sacrificial layer 13 is formed on the substrate 11 of the silicon wafer, and the first structure 12 is formed thereon. The first structure 12 is etched with the first mask 14 as a metal film. Patterning through the first mask 14 uses a photolithography process or the like.

The etching process forms the first mask pattern 15 on the first structure 12 in a horizontal state, and then removes the remaining portions except the necessary portion, while the structure 12a and the fin member 12b as shown in FIG. Will form.

The etching process of the step of forming the pin member is made of excessive etching, and the first sacrificial layer 13 is etched to form the recessed portion (16). In addition, the removal of the first sacrificial layer 13 and the first mask pattern 15 after the excessive etching in the forming of the fin member is anisotropic dry etching.

Therefore, the first sacrificial layer 13 is placed on the bottom of the substrate and the structure (after the reflector) and the fin member 12b protrude. This can be seen by the attached drawing Fig. 3 (c) as the pin member forming step.

(2nd step)

The second sacrificial layer 21 is formed in the state of FIG. 3 (c) including the structure 12a and the fin member 12b.

By using the first mask 14 again to mask the pattern, the sacrificial layer 21 formed on the recess 16 is removed and a new recess 16 is formed. This can be seen from FIG. 3 (d).

As shown in FIG. 3 (e), after depositing the second structure 22 over the concave portion 16, the pin member 12b and the structure 12a on which the sacrificial layer 21 is formed, the second structure 22 is deposited. Using the two masks 24 to mask in the state as shown in Figure 3 (f) to form a bearing member 20 of the structure in which the structure is located around the pin member (12b).

(3rd step)

By treating each sacrificial layer 13 and 21 by isotropic dry etching in the state where the bearing member 20 is formed, the upper and lower sacrificial layers 13 of the structure 12a as well as the upper and lower portions of the fin member 12b ( 21) are all removed to make the structure 12a a movable reflector.

The above embodiment shows the results of the joint structure of FIG. 1 carried out by the above embodiment of the present invention as shown in FIG.

Example 2.

4 (a) to 4 (g) show a manufacturing process of the micromirror according to another embodiment of the present invention, and FIG. 5 shows a pixel on which the reflective surface having the pin member and the pillar member of FIG. Is an illustration showing a micromirror structure of another embodiment for turning off.

(First process)

The insulating layer 101, the electrode 102, the first sacrificial layer 103 and the structure 104 thereon on the substrate 100 of the silicon wafer in a known manner as shown in FIG. 4 (a) of the accompanying drawings. To form. The fin member 106 is formed by etching the structure in a state in which the mask pattern 105 is formed on the structure 104 having the stacked structure as shown in FIG. 4 (b).

In the step of forming the fin member 106, the excessive etching is performed, and in this step, the removal of the first sacrificial layer 103 and the mask pattern 105 is performed by anisotropic dry etching.

(2nd step)

4 (c) shows a state in which the first sacrificial layer 103 and the mask pattern 105 are removed by anisotropic dry etching after excessive etching. That is, the sacrificial layer 107 is formed only on the upper surface of the fin member 106 by removing the sacrificial layer 103 and the mask pattern 105 except the lower portion of each structure in the fin member forming step and forming the second sacrificial layer 107. Let this remain.

Thereafter, the third structure 108 is formed in the state including the second sacrificial layer 107, and the water bearing member 108 can be formed by masking and etching. This is as shown in Fig. 4 (d) of the accompanying drawings. Here, the bearing member 108 includes all shaft functional members such as staples.

(3rd step)

When the water bearing member is formed as shown in FIG. 4E, a thick film sacrificial layer 109 is formed thereon, and the pillar member forming recess 110 is responsive to an approximately central portion of the thick film sacrificial layer 109. After forming by ion etching, the fourth structure 111 is deposited. The reflective structure 113 is formed by masking and etching in the state where the fourth structure 111 is formed, and at the same time, the fourth structure 111 is deposited along the recess 110 to form the pillar member 112. The pillar member 112 is connected to the lower pin member 106 and also connected to the upper plate-shaped reflector 113. Isotropic dry etching is performed to remove the upper, lower and thick film sacrificial layers 109 of the fin member 106 and the bearing member 108.

The first, second, third, and fourth structures constituting the structures of the first and second embodiments of the present invention, that is, the electrode, the pin member, the bearing member, the pillar member, and the reflector, are preferably implemented with a metal film.

The structure of the image display micromirror according to the above-described embodiment forms at least three electrodes 102 formed on the substrate 100. The bearing member 108 is connected to one of the center electrodes of the electrode 102, and the pin member 106 is formed to be rotatably supported by the bearing member 108. The pillar member 112 is formed above the pin member 106. The pillar member 112 floats upward above the electrode 102 and at the same time forms a reflector 113 which forms a reflective surface. The reflector 113 of the fin member 106 as described above retains elasticity when the upper surface forms a reflecting surface and is inclined left and right in a state supported by the bearing member 108.

The present invention manufactured through such a process provides a sacrificial layer capable of a dry etching process in which a movable structure does not adhere to a substrate during etching by avoiding conventional wet etching when the sacrificial layer is removed, and in the dry etching process By properly applying anisotropic dry etching and isotropic dry etching, problems of the etching process have been improved.

In addition, the process to reduce the use of the mask in the process of forming a fin member in the above-described process, forming a recess in the upper and lower sacrificial layers, and preparing a separate mask for forming each pattern when manufacturing the bearing member The present invention provides a method of manufacturing a movable micromirror that can reduce the number of high-level mask manufacturing processes that are separately manufactured by reusing a mask during fin member masking while forming a recess in the upper and lower sacrificial layers.

Claims (5)

A method of manufacturing a micromirror for a projection image display device by forming an insulating layer, an electrode, and a first sacrificial layer on a silicon engine, A pin member forming step of forming a structure on the first sacrificial layer formed on the silicon substrate and then etching the structure to form a fin member; A bearing member forming step of forming a second bearing layer after removing the sacrificial layers except for the lower portion of each structure in the fin member forming step, and forming and masking a third structure on the second sacrifice layer; After the bearing member is formed, a thick film sacrificial layer is formed thereon, a pillar member forming concave portion is formed in the central portion of the thick film sacrificial layer, and a new structure is formed. The structure is then etched to form the structure of the pillar member. Column member forming step: and After forming the pillar member, the upper and lower sacrificial layers of the fin member and the upper and lower sacrificial layers of the structure are etched to form a movable micro mirror manufacturing method for an image display device, including a reflector forming step of imparting mobility to the fin member, the bearing member, and the structure. . The method of manufacturing a movable micromirror for an image display apparatus according to claim 1, wherein the etching of the pin member is performed by transient etching. The method of claim 1, wherein in the forming of the pin member, the first sacrificial layer and the mask pattern are removed by anisotropic dry etching. The method of manufacturing a movable micromirror for an image display apparatus according to claim 1, wherein in masking the second sacrificial layer on the fin member in the bearing member forming step, etching is performed using the same mask as the fin member forming step. A micromirror for a projection image display device having a plurality of electrodes arranged at equal intervals on a silicon substrate, A bearing member formed in the central portion of the electrode: A pin member grasped by the bearing member and pivotable in place: Pillar member connected upward from the pin member: And And a reflector formed on an upper end of the pillar member, the reflector being spaced and seated on the substrate to be moved by an electrostatic force of adjacent left and right electrodes to change an angle of a reflecting surface formed on the upper surface of the pillar member.

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