JP4458704B2 - Planar type galvano device and manufacturing method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a planar galvano device and a method for manufacturing the same.
[0002]
[Prior art]
The planar type galvano device utilizes the principle of a galvanometer and is represented by a galvanometer mirror device used in a laser beam scanning system or the like. In order to reduce the size of the galvanometer mirror, a method of manufacturing a galvanometer mirror using a semiconductor device manufacturing process has been developed. Semiconductor planar type galvano devices are roughly classified into an electrostatic drive system and an electromagnetic drive system. The electrostatic drive system is disclosed in detail in, for example, Japanese Patent Application Laid-Open No. 11-119145. The electromagnetic drive system is disclosed in detail as, for example, a planar galvanometer mirror and a method for manufacturing the same in JP-A-7-175005. The present invention relates to an electromagnetic drive type planar galvano device and a method of manufacturing the same.
[0003]
1A and 1B are diagrams showing a conventional planar galvano device, in which FIG. 1A is a front sectional view, FIG. 1B is a top view, and FIG. 1C is a side sectional view. A reflection mirror 3 is formed at the center of the upper surface of the movable plate 2 formed integrally with the silicon substrate 1, and a planar coil 4 is formed at the periphery. The movable plate 2 is formed in a hollow state on the silicon substrate 1 and is held by torsion bars 5 and 6 formed integrally with the silicon substrate 1. The silicon substrate 1 is fixed to the upper surface of a base 8 fixed to the upper surface of the base substrate 7. In the top view (b), permanent magnets 9 and 10 are arranged above and below the silicon substrate, and a yoke 11 is placed on the periphery of the base substrate 7. The yoke 11 is constituted by stacking a plurality of hollowed and square-shaped ones.
[0004]
When the planar coil 4 formed on the movable plate 2 is energized, the movable plate 2 rotates around the torsion bars 5 and 6 as rotation centers. As shown in the side sectional view of (c), the movable plate 2 can rotate about 20 degrees up and down. Two pins 12 are implanted through the base substrate 7, and the upper surface of the pins 12 and the pattern 1a formed on the silicon substrate 1 are connected by wire bonding.
[0005]
The planar type galvano device according to the prior art has a general configuration, but in order to enlarge the reflection area, a reflection mirror is formed on the entire upper surface of the movable plate integrally formed on the silicon substrate, and a planar coil is formed on the lower surface. Forming types have been devised. This configuration will be described with reference to FIG.
[0006]
FIG. 2 is a front sectional view (a), a top view (b), and a bottom view (c) showing the configuration of a conventional planar galvano device.
[0007]
The silicon substrate 13 is integrally formed with a flat movable plate 14 and torsion bars 15 and 16 that pivotally support the movable plate 14 with respect to the silicon substrate 13 so as to be swingable in the vertical direction of the substrate. A planar coil 17 that generates a magnetic field by energization is laid on one surface of the movable plate 14, and a reflection mirror 18 is provided on the other surface. Reference numeral 19 denotes a base substrate, and the silicon substrate 13 is directly mounted with the reflection mirror 18 side provided on the movable plate 14 facing downward (base substrate side). Reference numeral 19 a denotes a hole corresponding to the reflection mirror 18 provided on the base substrate 19. Reference numeral 20 denotes a wire, which connects the wire connection pad 21 provided on the silicon substrate 13 and the pattern 19b provided on the base substrate 19 by wire bonding to form an electrical connection between the silicon substrate 13 and the base substrate 19. .
[0008]
A pair of permanent magnets 22 and 23 for applying a magnetic field to opposite sides of the movable plate 14 are fixed to the base substrate 19 at positions parallel to the axial direction of the torsion bars 15 and 16. A yoke 24 is placed on the peripheral edge portion to constitute a planar type galvano device.
[0009]
According to the prior art of FIG. 2, it is possible to realize a planar type galvano device having a large reflecting mirror surface while keeping the chip size unchanged.
[0010]
Next, a silicon substrate (galvanomirror chip) of the planar galvano device will be described. 3A and 3B are views showing a galvanometer mirror chip, where FIG. 3A is a top view, FIG. 3B is a bottom view, and FIG. 3C is a cross-sectional view along AA ′. FIG. 4 shows a manufacturing process of the galvanometer mirror chip.
Step a (oxide film forming step): a silicon bonded substrate having a thickness of 500 μm (referred to as an SOI group, for example, active layer silicon 26 (100 μm), an intermediate layer 27 (1 μm) made of a silicon oxide film, and a support substrate 28 (400 μm) A silicon oxide film (1 μm) 29 is formed by thermally oxidizing the upper and lower surfaces of 25) (hereinafter referred to as SOI substrate).
Step b (pattern formation step): Each pattern of the coil 30, the insulating film 31, and the protective film 32 is laminated on the upper surface side of the substrate by photolithography.
Step c (oxide film removal step 1): The oxide film 29 except for the upper movable plate forming portion is removed by dry etching.
Step d (active layer removal step): The active layer silicon 26 reaching the intermediate layer 27 of the SOI substrate 25 is removed by anisotropic etching.
Step e (intermediate layer removal step): The intermediate layer 27 exposed by anisotropic etching is removed by dry etching.
Step f (oxide film removal step 2): The silicon oxide film 29 in a portion excluding the movable plate forming portion on the lower surface side of the substrate is removed.
Step g (supporting substrate removing step): The supporting substrate (silicon) 28 reaching the intermediate layer 27 is removed by anisotropic etching.
Step h (intermediate layer removing step 2): Since anisotropic etching has selectivity between silicon and silicon oxide film, the etching is apparently terminated when the etching reaches the intermediate layer 27 on the lower surface of the movable plate. At this point, the through portion of the substrate is completely removed. The intermediate layer 27 remaining on the lower surface of the movable plate is removed by dry etching.
Step i (reflection mirror forming step): The total reflection mirror 33 is formed by vapor deposition or sputtering after the silicon surface is exposed.
The galvanometer mirror chip is manufactured by such a process. Usually, a large number of galvanometer mirror chips are formed on a large wafer at the same time as a semiconductor element, and are divided individually after completion.
[0011]
[Problems to be solved by the invention]
In an electromagnetically driven planar type galvano device, films with internal stress such as coils, insulating films, protective films, etc. formed on the upper surface of the movable plate are laminated in multiple layers, and this stress acts on the movable plate. As a result, the movable plate is warped. When the movable plate is warped, the reflection mirror surface formed on the lower surface of the movable plate is similarly warped, and as a result, a problem such as blurring of reflected light from a laser or the like is caused. (This is called a decrease in the flatness of the reflecting mirror)
[0012]
In the step b of the prior art described with reference to FIG. 4, the movable plate is warped by forming the coil, the insulating film, and the protective film. For example, when aluminum is used for the coil, polyimide is used for the protective film, and the protective film is used, true stress is generated separately from the thermal stress due to the difference in thermal expansion coefficient. By forming this film, warpage in the concave direction occurs on the upper surface side of the movable plate. By laminating these films, the amount of warpage is integrated and further increased.
[0013]
The tensile stress generated by the formation of the coil, insulating film, and protective film increases as the film thickness increases, and the amount of warpage of the movable plate increases accordingly. Further, the amount of warp of the movable plate due to film stress increases as the movable plate thickness decreases.
[0014]
In view of the above problems, the present invention intends to provide a planar galvano device that minimizes the occurrence of warpage of the movable plate due to the formation of a coil, an insulating film, a protective film, etc. on the upper surface of the movable plate, and a method for manufacturing the same. is there.
[0016]
A movable plate and a torsion bar that pivotably supports the movable plate relative to the substrate are integrally formed on the substrate, a reflection mirror is formed on one surface of the movable plate, and a driving planar coil is formed on the other surface side of the movable plate. In the planar type galvano device that forms and swings the movable plate, a film having a strong compressive stress is formed on the surface of the movable plate opposite to the reflecting mirror surface, and the driving is performed on the film having the strong compressive stress. A planar type galvano device in which a planar coil is formed .
[0018]
A process of forming a silicon oxide film by thermally oxidizing the upper and lower surfaces of an SOI substrate comprising an active layer silicon, an intermediate layer and a supporting substrate , and laminating each pattern of a coil, an insulating film and a protective film on the upper surface side of the SOI substrate by photolithography. a step of, removing the oxide film in a portion except for the top movable plate forming portion by dry etching, removing by anisotropic etching the active layer silicon leading to the intermediate layer of the SOI substrate, anisotropic removing the intermediate layer exposed by etching by dry etching, and removing the silicon oxide film in a portion except for the movable plate forming part of the SOI substrate lower surface, anisotropic support base plate leading to the intermediate layer removing by gender etching, and removing the intermediate layer remaining on the bottom surface movable plate by dry etching to expose the active layer silicon surface The method of manufacturing a planar galvano device having a step of forming a reflection mirror on the SOI substrate, wherein an opposite surface of the reflecting mirror formation surface coil, the insulating film, under the laminated portion of each pattern of the protective film a method for producing a planar galvano device having a step of forming a strong film having compressive stress on.
[0019]
In the present invention in order to solve the problems of the prior art, so as to offset the warpage of the variable dynamic plate, forming a strong film having compressive stress on the opposite side to form a reflecting mirror of the movable plate, a strong film having the compressive stress A planar type galvano device manufacturing method in which the warp of the movable plate is reduced or eliminated by canceling out the stresses of the coil and insulating film formed thereon.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 5 is a cross-sectional view of the reference of'll Help Lehner galvanometer device according to the present onset Akira. The silicon substrate 14 which is a movable plate has a size of 4 × 3 mm, a thickness of 150 μm, a thickness of the chromium thin film 34 is 0.2 μm, and a thickness of the aluminum thin film 33 which becomes a reflection mirror is 0.3 μm. . Although not shown, 0.05 μm of SiO 2 is further coated as a protective film for the reflecting mirror. On the thin film coil side, the thickness of the thermal oxide film (SiO2) 29, which is an insulating film, is 1 μm, the thin film coil 30A is 40 μm wide, 2 μm thick, the coil interval is 10 μm, the number of turns is 15, the thickness of the insulating film 31 is 2 μm, and the thin film The coil 30B has a width of 40 μm, a thickness of 2 μm, a coil interval of 10 μm, a number of turns of 15, and a thickness of the protective film 32 of 2 μm. The thin film coils 30A and 30B are made of aluminum, and the insulating film 31 and the protective film 32 are made of polyimide. Although chromium was used as a material having a strong tensile stress, nickel can be used as another material.
[0021]
The movable plate of the galvano device according to the prior art had a warp of about 2 μm in a convex shape on the mirror surface side. In this embodiment, the movable plate is formed by forming a thin film for correction with strong tensile stress on the mirror surface side. I was able to almost eliminate the warp. In order to eliminate the warp, it is only necessary to form a correction thin film in an amount that can correct the warp of the movable plate manufactured according to the conditions of the prior art. Therefore, if the various conditions are changed, the correction thin film is also changed. Occurrence can be prevented. The flatness (warpage amount) of the reflecting mirror is generally desired to be λ / 4 or less, but in this embodiment, the warp could be made λ / 4 or less. (Λ is the wavelength of the laser beam, for example, 670 nm for the semiconductor laser beam of red visible light.)
[0022]
6 is a cross-sectional view of one embodiment of a I Help Lehner galvanometer device to the onset bright. An aluminum thin film 33 serving as a reflection mirror is formed on one surface of the silicon substrate 14 which is a movable plate. On the opposite side of the thin film coil side, a metal thin film or a SiO2 thin film 35 having a strong compressive stress is formed, and an insulating film 36 is formed thereon (the insulating film 36 can be omitted if insulation can be ensured by the SiO2 thin film 35), and a conventional film is formed thereon. A thin film coil, an insulating film, a thin film coil, and a protective film are formed as in the technology. The thin film coil is made of aluminum, and the insulating film and the protective film are made of polyimide.
[0023]
The movable plate of the galvano device according to the prior art had a warp of about 2 μm in a convex shape on the mirror surface side. In this embodiment, a SiO2 thin film 35, which is a correction thin film having a strong compressive stress, is formed on the planar coil side. Therefore, the warp of the movable plate could be almost eliminated. In order to eliminate the warp, it is only necessary to form a correction thin film in an amount that can correct the warp of the movable plate manufactured according to the conditions of the prior art. Therefore, if the various conditions are changed, the correction thin film is also changed. Occurrence can be prevented.
[0024]
FIG. 7 is a cross-sectional view of another reference of due to the onset Akira Help Lehner galvanometer equipment. An aluminum thin film serving as a reflection mirror is formed on one side of the silicon substrate. On the opposite side of the thin film coil side, an insulating film, a thin film coil, an insulating film, a thin film coil, and an insulating film are formed as in the prior art, and a thin film having a strong compressive stress such as a SiO2 thin film 37 is formed thereon. The insulating film and the protective film are polyimide.
[0025]
The movable plate of the galvano apparatus according to the prior art had a warp of about 2 μm in a convex shape on the mirror surface side. However, in this embodiment, a correction thin film having a strong compressive stress is formed on the planar coil side. The warp was almost eliminated. In order to eliminate the warp, it is only necessary to form a correction thin film in an amount that can correct the warp of the movable plate manufactured according to the conditions of the prior art. Therefore, if the various conditions are changed, the correction thin film is also changed. Occurrence can be prevented.
[0026]
【The invention's effect】
It is possible to correct the warp of the movable plate by forming a strong compressive stress film on the surface of the movable plate opposite to the reflecting mirror surface and forming a driving planar coil on the strong compressive stress film. I can do it.
[0027]
When the deposit (coil, insulating film, protective film) on the upper surface of the movable plate is thick and the influence of the stress on the movable plate is large, or when the movable plate is thin and easily affected by the stress of the deposit, Even under conditions that warp easily, the amount of warpage can be relaxed by providing a film that forms an opposite stress that corrects warpage, thus increasing the degree of freedom in design.
[0028]
As in the case of a thin film that takes thermal stress into consideration as in the prior art, it is difficult to match the thermal expansion coefficient with that obtained by laminating materials having different thermal expansion coefficients. In the present invention, since the true stress is used, it is not affected by the thermal expansion coefficient of the material.
[Brief description of the drawings]
1A and 1B are diagrams showing a configuration of a conventional planar galvano device, in which FIG. 1A is a front sectional view, FIG. 1B is a top view, and FIG.
2A and 2B are diagrams showing a configuration of a conventional planar galvano device, where FIG. 2A is a front sectional view, FIG. 2B is a top view, and FIG. 2C is a side sectional view.
3A and 3B are diagrams showing a configuration of a conventional galvanometer mirror chip, in which FIG. 3A is a top view, FIG. 3B is a bottom view, and FIG. 3C is a cross-sectional view taken along line AA ′ of FIG.
4 is a cross-sectional view of the silicon substrate in each step of the galvanometer mirror chip forming FIG. 5 is a cross-sectional view of the reference in the present onset bright by pulp Lehner galvanometer device 6 by the present onset bright pulp Lehner type sectional view of another reference planar galvanometer device according sectional view Figure 7 this onset light of an embodiment of a galvano apparatus [description of symbols]
DESCRIPTION OF SYMBOLS 1 Silicon substrate 1a Pattern 2 Movable plate 3 Reflection mirror 4 Plane coil 5 Torsion bar 6 Torsion bar 7 Base substrate 8 Base 9 Permanent magnet 10 Permanent magnet 11 Yoke 12 Pin 13 Silicon substrate 14 Movable plate 15 Torsion bar 16 Torsion bar 17 Planar coil 18 reflecting mirror 19 base substrate 19b pattern 20 wire 21 wire-connecting pads 22 permanent magnet 23 permanent magnet 24 yoke 25 SOI substrate 26 activation Soshi silicon 27 intermediate layer 28 supporting base plate 29 silicon oxide film 30 coil 31 insulation Enmaku 32 protective film 33 Total reflection mirror 34 Chrome thin film 35 SiO2 thin film 36 Insulating film 37 SiO2 thin film

Claims (2)

A movable plate and a torsion bar that pivotably supports the movable plate relative to the substrate are integrally formed on the substrate, a reflection mirror is formed on one surface of the movable plate, and a driving planar coil is formed on the other surface side of the movable plate. In the planar galvano device that forms and swings the movable plate,
Forming a strong compressive stress film on the surface of the movable plate opposite to the reflecting mirror surface ;
A planar galvano device , wherein the driving planar coil is formed on the strong compressive stress film . A process of forming a silicon oxide film by thermally oxidizing the upper and lower surfaces of an SOI substrate comprising an active layer silicon, an intermediate layer and a supporting substrate , and laminating each pattern of a coil, an insulating film and a protective film on the upper surface side of the SOI substrate by photolithography. a step of, removing the oxide film in a portion except for the top movable plate forming portion by dry etching, removing by anisotropic etching the active layer silicon leading to the intermediate layer of the SOI substrate, anisotropic removing the intermediate layer exposed by etching by dry etching, and removing the silicon oxide film in a portion except for the movable plate forming part of the SOI substrate lower surface, anisotropic support base plate leading to the intermediate layer removing by gender etching, and removing the intermediate layer remaining on the bottom surface movable plate by dry etching to expose the active layer silicon surface The method of manufacturing a planar galvano device having a step of forming a reflection mirror on the SOI substrate, wherein an opposite surface of the reflecting mirror formation surface coil, the insulating film, under the laminated portion of each pattern of the protective film A method of manufacturing a planar galvano device, comprising the step of forming a film having a strong compressive stress on the substrate.

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