JP5543810B2 - Optical deflector package - Google Patents

Description

  The present invention relates to an optical deflector package, for example, a piezoelectric driving hermetically sealed optical deflector package.

  For example, in a projector as one form of an image display device, an optical deflector is used to deflect a light beam from a light source and project it onto a screen to display an image on the screen. As such an optical deflector, there is a piezoelectric drive type optical deflector as an apparatus using a semiconductor manufacturing process technology and a microelectromechanical system (MEMS) technology (see Patent Document 1).

  In the above-described piezoelectric drive type optical deflector, a micromirror, an elastic beam that supports the micromirror in a swingable manner, that is, a torsion bar, and a space between the support and the torsion bar are provided in the cavity of the support of the semiconductor substrate. A coupled piezoelectric actuator is formed. As a result, the piezoelectric actuator to which the drive voltage is applied transmits the torque to the torsion bar and twists and deforms the torsion bar, thereby driving the micromirror to swing. Such a piezoelectric drive type optical deflector can obtain a large driving force with a small and simple structure. Patent Document 1 discloses a two-dimensional optical deflector.

  In general, in an optical deflector having a micromirror with a large deflection angle, air flowing along the rotation axis of the micromirror flows out from the tip of the micromirror, and an air flow develops. As a result, substances such as dust brought about by the airflow are likely to adhere to the micromirror. There is a hermetically sealed optical deflector package in order to prevent adhesion of such substances as micromirror dust.

  Also, in an optical deflector driven under atmospheric pressure, if the micromirror vibrates at a high frequency and a large amplitude due to the viscous resistance of air, amplitude fluctuation and phase fluctuation occur in the micromirror, and the scanning time of the deflected light beam Cause fluctuations (jitter). In order to reduce such jitter, there is a hermetically sealed optical deflector package that is vacuumed or decompressed.

  In the above-described vacuum or reduced pressure hermetically sealed optical deflector package, since the air resistance is small, the mechanical Q value of the optical deflector is high, so that the optical deflector can be driven with small energy, The swing angle of the micromirror can be increased, or the swing angle of the micromirror can be kept small and the micromirror can be swung at a higher frequency.

  Conventional vacuum or reduced pressure hermetically sealed optical deflector packages include metal CAN packages or ceramic packages.

  In a hermetically sealed optical deflector package using a metal CAN package, the optical deflector chip is die-bonded to the metal CAN package with hermetic sealing of the lead terminals using solder or AuSn eutectic paste, and then to the lead terminals. The optical deflector chip is connected to the optical deflector chip with a bonding wire. Finally, a metal cap welded with an optical transmission window is resistance welded to a metal CAN package in a vacuum atmosphere.

  On the other hand, in a hermetically sealed optical deflector package using a ceramic package, the optical deflector chip is die-bonded to the metal CAN package with hermetic seal of the lead terminals using solder or AuSn eutectic paste, and then the lead terminals and The optical deflector chip is connected to the optical deflector chip by a bonding wire, and finally, an optical transmission window cap with a lid is seam welded in a vacuum atmosphere with a metal lid provided on the outer periphery of the opening of the ceramic shaped package ( Reference: FIG. 4 of Patent Document 2.

  In any hermetically sealed optical deflector package, the incident light beam is reflected by the micromirror of the optical deflector chip and scanned through the optical transmission window. In general, both surfaces of the optical transmission window are provided with an antireflection coating using a dielectric multilayer film so that interference of a light beam does not occur.

JP 2005-148459 A JP 2003-243550 A JP 2001-234331 A JP 2002-177765 A JP 2003-81694 A

  However, when an anti-reflection coating with a dielectric multilayer film is applied to both sides of the optical transmission window, it covers a wide wavelength range including the three wavelengths used in the projector, that is, 640 nm (red), 532 nm (green), and 450 nm (blue). In order to exhibit the antireflection function, each dielectric multilayer film has to be several tens of layers. Therefore, there is a problem that the manufacturing cost increases.

  In addition, since the dielectric multilayer structure is shifted by the heat generated when the optical transmission window cap is welded and sealed to the package, the optical transmission window needs to be separated from the seal portion to some extent. There is also a problem that the deflector package becomes larger.

  Furthermore, the optical transmission window of the dielectric multilayer film is highly dependent on the incident angle of the light beam. For example, the reflectivity differs by several percent between vertical incidence and 45 ° incidence, so that the light beam is incident on the optical deflector chip in advance. It is necessary to decide the angle. As a result, there is a problem that the versatility of the hermetically sealed optical deflector package is low. Worst, after determining the incident angle, the optical transmission window must be redesigned each time the optical system changes.

  Furthermore, although the dielectric multilayer film can be easily formed on a flat plate, it is difficult to form the dielectric multilayer film on the bottom surface of the cavity of the optical transmission window glass having a recess (cavity). Therefore, it is difficult to apply the dielectric multilayer film to a so-called wafer level package in which a flat optical deflector wafer is sealed at the wafer level using an optical transmission window glass having a cavity of a micromirror oscillation space as a cap. There is also a problem that there is. In such a wafer level package, an optical transmission window glass cap must be formed by laminating and bonding a spacer having an opening and a flat glass having an antireflection coating of a dielectric multilayer film on both sides. Increases manufacturing costs.

In order to solve the above-described problems, an optical deflector package according to the present invention includes a support, an elastic member, a mirror supported by an elastic member in a cavity of the support so as to be swingable, and a mirror via the elastic member. An optical deflector having an actuator to be oscillated , a first through electrode, and first and second joining electrodes provided above and below the first through electrode, and an oscillation of the mirror across the optical deflector The first and second sealing members for sealing the cavity for securing the space, the first sealing member facing the cavity, the optical transmission window of the antireflection function parabolic uneven structure and the first bonding A fourth bonding electrode connected to the second bonding electrode and having a third bonding electrode connected to the bonding electrode, the second sealing member being provided on the second through electrode and the second through electrode. It has the electrode for joining . As a result, the antireflection function parabolic concavo-convex structure can be easily formed by etching, imprinting, or the like, and the manufacturing cost is reduced. Further, since there is no shift due to heat, the antireflection function parabolic concavo-convex structure is brought close to the seal portion of the sealing member, thereby reducing the size of the package. Furthermore, the incidence dependence of the light beam is small. Furthermore, since the antireflection function parabolic uneven structure can be formed on the bottom surface of the cavity, a wafer level package can be applied.

  Further, the pitch of the antireflection function parabolic uneven structure is equal to or less than ½ of the wavelength of incident light, and the height of the antireflection function parabolic uneven structure is 1 to 2 times the pitch.

  According to the present invention, the manufacturing cost can be reduced and the size can be reduced. Moreover, since it can be applied to a wafer level package, the manufacturing cost can be further reduced.

It is a figure for demonstrating the principle of the reflection preventing structure which concerns on this invention. It is sectional drawing which shows embodiment of the airtight sealing optical deflector package based on this invention. It is a figure for demonstrating the incident angle of the light of the surface-ized sealing member of FIG. 2, Comprising: (A) is an enlarged view of a surface side sealing member, (B) is permeation | transmission of the optical transmission window of a surface side sealing member. It is a graph which shows a rate. The wafer level package state before cutting out of the hermetically sealed optical deflector package of FIG. 2 is shown, (A) is an overall perspective view, and (B) is a partial sectional view of (A). It is sectional drawing for demonstrating the outline of the manufacturing method of the airtight sealing optical deflector package of FIG. It is sectional drawing for demonstrating the 1st manufacturing method of the glass wafer for surface side sealing of FIG. It is sectional drawing for demonstrating the 1st manufacturing method of the glass wafer for surface side sealing of FIG. It is sectional drawing for demonstrating the 2nd manufacturing method of the glass wafer for surface side sealing of FIG. It is a top view of the optical deflector of FIG. It is sectional drawing for demonstrating the detail of the manufacturing method of the airtight sealing optical deflector package of FIG. It is sectional drawing for demonstrating the detail of the manufacturing method of the airtight sealing optical deflector package of FIG. It is sectional drawing for demonstrating the detail of the manufacturing method of the airtight sealing optical deflector package of FIG. It is sectional drawing for demonstrating the detail of the manufacturing method of the airtight sealing optical deflector package of FIG. It is sectional drawing for demonstrating the detail of the manufacturing method of the airtight sealing optical deflector package of FIG. It is sectional drawing for demonstrating the detail of the manufacturing method of the airtight sealing optical deflector package of FIG. It is sectional drawing for demonstrating the detail of the manufacturing method of the airtight sealing optical deflector package of FIG. It is sectional drawing which shows the example of a change of the airtight sealing optical deflector package of FIG.

  FIG. 1 is a view for explaining the principle of the antireflection structure according to the present invention.

As shown in FIG. 1A, when the objects A and B having different refractive indexes n _A and n _B (n _B > n _A ) are in contact, the refractive index n is at the boundary surface where the objects A and B are in contact. Since it changes sharply, a part of the incident light I is reflected as reflected light R.

On the other hand, as shown in FIG. 1B, when the boundary surface between the objects A and B has a parabolic uneven structure, the refractive index continuously changes from n _A to n _B. The reflected light R is suppressed. Specifically, in order to continuously change the refractive index, the pitch P of the parabolic uneven structure is
P ≦ λ / 2
Where λ is the wavelength of the incident light I,
The height H of the parabolic uneven structure is
H / P = 1-2
And As a result, when the object A is air and the object B is glass, the reflected light R with respect to the incident light I is suppressed to 2% or less over the entire visible light range, and the transmittance is 98% or more. In particular, in the hermetically sealed optical deflector package, incident light is reflected by the oscillating micromirror in the package and emitted outside the package as scanning light, so that it passes through the optical transmission window twice. Therefore, it is extremely important to suppress reflection of the optical transmission window. In addition, when a laser is used as incident light, it has coherence in addition to high light intensity, so the presence of reflected light on the package surface acts as noise in the projected image formed by the applied projector. Therefore, it is more important to suppress the reflection of the optical transmission window. For this reason, the present invention employs an optical transmission window having an antireflection structure shown in FIG.

  FIG. 2 is a sectional view showing an embodiment of a hermetically sealed optical deflector package according to the present invention.

  The hermetically sealed optical deflector package of FIG. 2 has a surface side sealing member 1 made of, for example, glass having an optical transmission window 11 having an antireflection structure with a parabolic concavo-convex structure, a micromirror 21 and a micromirror 21 in a horizontal axis. A support 22 for swinging with respect to the optical mirror 2, a support 23 for swinging the micromirror 21 with respect to the vertical axis, and an optical deflector 2 having a through electrode 24, and a through electrode 31 and an Au electrode 32. For example, it is comprised by the back surface side sealing member 3 which consists of glass. An Au solder electrode 4 is provided between the front surface side sealing member 1 and the optical deflector 2, and an AuSn eutectic electrode 5 is provided between the optical deflector 2 and the back surface side sealing member 3. ing.

  If the size of the micromirror 21 of the optical deflector 2 is, for example, for projectors, it is as large as about 1 mm × 1 mm, and an optical transmission window is provided on the surface side sealing member 1 in order to secure a swinging space for the micromirror 21. 11 is provided with a cavity 1a, and the back surface side sealing member 3 is provided with a cavity 3a.

The concavo-convex structure of the parabolic concavo-convex structure is preferably within a predetermined angle range. As shown in FIG. 3, since the micromirror 21 normally operates within a range of 0 to ± 20 ° , the maximum movable angle can be estimated to be 50 ° or less. The transmittance of the parabolic concavo-convex structure changes depending on the incident angle φ of the light, but the light having an incident angle φ smaller than the angle θ of the concavo-convex structure is constant at a high transmittance. Since the incident angle of light is considered to be the same as the maximum movable angle, the parabolic uneven structure has a central axis perpendicular to the surface of the optical transmission window 11 of the surface side sealing member 1, and the side surface of the uneven structure is an optical transmission window. The angle θ rising from the surface is 60 to 80 ° , more preferably 65 to 75 ° .

  4 shows a wafer level package state before cutting out the hermetically sealed optical deflector package of FIG. 2, (A) is an overall perspective view, and (B) is a partial sectional view of (A).

  As shown in FIG. 4, the hermetically sealed optical deflector package of FIG. 2 includes three wafer-side sealing glass wafers 100 in a wafer level package state, an optical deflector silicon wafer 200, and a back-side sealing. It is obtained by cutting the glass wafer 300 along the dicing line L.

  The cavity 1a of the front surface side sealing member 1 and the cavity 3a of the back surface side sealing member 3 are formed at the wafer level of the front surface side sealing glass wafer 100 and the optical deflector silicon wafer 200 of FIG. For example, a photoresist pattern is formed using a photolithography method, and then the glass wafer is etched using a wet etching method or a dry etching method. In this case, since the formation of the cavity of the front-side sealing glass wafer 100 is important in terms of light transmittance, a wet etching method is used. On the other hand, since the cavity formation of the back surface side sealing glass wafer 300 is a simple sealing member, either may be used, and a sandblasting method may be used.

  Next, an outline of a manufacturing method of the hermetically sealed optical deflector package of FIG. 2 will be described with reference to a cross-sectional view of FIG.

  First, referring to FIG. 5A, an optical deflector silicon wafer 200 on which a micromirror 21, supports 22, 23, through electrodes 24, Au electrodes 25, 26 are formed in advance is prepared. In addition, a glass wafer 300 for back side sealing on which the cavity 3a, the through electrode 31, the Au electrode 32, and the AuSn electrode 33 are formed in advance is prepared. An underlying barrier metal layer (not shown) is formed below the Au electrodes 25, 26, 32 and the AuSn electrode 33.

  Next, referring to FIG. 5B, in the vacuum container, the optical deflector silicon wafer 200 is heat-pressed onto the back-side sealing glass wafer 300 and bonded by AuSn eutectic bonding. In other words, the trapezoidal heat treatment profile is executed in the vacuum vessel as in the lead-free solder process. For example, the temperature is raised from room temperature to 310 ° C. at a constant rate, held at 310 ° C. for several seconds to several tens of seconds, and then lowered to a room temperature at a constant rate. As a result, the Au electrode 25 of the optical deflector silicon wafer 200 and the AuSn electrode 33 of the back side sealing glass wafer 300 are eutectic bonded to form a new AuSn eutectic electrode 5. When thermocompression bonding is performed in a vacuum vessel, voids are unlikely to occur in the AuSn eutectic electrode 5.

  Next, referring to FIG. 5C, a surface-side sealing glass wafer 100 on which the cavity 1a, the optical transmission window 11, and the Au electrode 12 are formed in advance is prepared. An underlying barrier metal layer (not shown) is formed below the Au electrode 12. A lead-free solder ball (not shown) is printed on the Au electrode 12.

Next, referring to FIG. 5D, the front-side sealing glass wafer 100 is placed on the optical deflector silicon wafer 200 in a vacuum vessel, and the wafer is bonded by lead-free solder bonding. Since the bonding temperature of this lead-free solder is lower than the above-mentioned AuSn eutectic bonding temperature 310 ° C., for example, 260 ° C., the AuSn eutectic electrode 5 will not be remelted. The pressure of the vacuum vessel is set to such an extent that the mechanical Q value of the optical deflector becomes excessively large so that the control of the micromirror is not difficult. Therefore, the pressure of the vacuum vessel is not so large and is reduced to about 5000 to 50000 Pa. The However, before lead-free solder bonding, in order to suppress the influence of residual adsorbed gas and the like, a high vacuum of about 10 ⁻⁴ Pa is used, and the sealing glass wafers 100 and 300 and the optical deflector silicon wafer 200 are 200 to 300. Heat to about ℃ and anneal in 99.9999% high purity nitrogen atmosphere. Thereby, the pressure level at the time of sealing can be hold | maintained for several years, without using a getter material depending on a use.

  Finally, referring to FIG. 5E, the hermetically sealed optical deflector package of FIG. 2 can be obtained by dicing the sealing glass wafers 100 and 300 and the optical deflector silicon wafer 200 for each chip. become.

  The hermetically sealed optical deflector package of FIG. 2 thus obtained includes the Au electrode 32 through the through electrodes 24 and 31, so that it can be easily surface-mounted on various printed circuit boards by a solder reflow process. be able to.

  Next, the detail of the manufacturing method of the glass wafer 100 for surface side sealing of FIG. 5 is demonstrated.

  The optical transmission window 11 for the front-side sealing glass wafer 100 is manufactured by a first method using the glass etching method shown in FIGS. 6 and 7 and a second method in which the resin shown in FIG. 8 is imprinted with a mold. There is a method.

  A first method by the glass etching method shown in FIGS. 6 and 7 will be described. 6 and 7, the cavity 1a is already formed in the front-side sealing glass wafer 100, and the glass of that portion is illustrated.

  First, referring to FIG. 6A, a resist for electron beam drawing exposure is applied on a silicon wafer 501, and a fine resist pattern 502 is formed by an electron beam direct drawing exposure / development process.

  Next, referring to FIG. 6B, the silicon wafer 501 is etched by dry etching using the resist pattern 502 as a mask. Next, the resist pattern 502 is removed and washed to obtain a master mold 503 made of silicon as shown in FIG.

  Next, referring to FIG. 6D, the pattern of the master die 503 is transferred onto the ultraviolet transparent transparent resin film 504 by thermal nanoimprint processing. Next, the master mold 503 is removed to obtain a transparent replica mold 505 shown in FIG.

  Next, referring to FIG. 7A, a resist layer 506 is applied to a region where the cavity 1a of the front-side sealing glass wafer 100 is formed, and a transparent replica mold 505 is pressed onto the resist layer 506. While performing UV nanoimprint processing by irradiating ultraviolet rays. Next, when the transparent replica mold 505 is removed, a resist pattern 507 shown in FIG. 7B is obtained.

  Next, in FIG. 7B, using the resist pattern 507 as a mask, the front-side sealing glass wafer 100 is etched by a dry etching method such as a high-frequency coupled plasma reactive ion etching (ICP-RIE) method, and then the resist When the pattern 507 is removed, as shown in FIG. 7C, the optical transmission window 11 having a parabolic uneven structure antireflection structure is obtained on one side of the surface side sealing glass wafer 100.

  When the above-mentioned process is performed on the other side of the glass wafer 100 for surface side sealing, as shown in FIG. 7D, the antireflection structure having a parabolic concavo-convex structure also on the other side of the glass wafer 100 for surface side sealing. The optical transmission window 11 is obtained.

  The manufacturing method of FIGS. 6 and 7 is based on a nanoimprint processing method using a master mold, but it is also possible to directly perform photolithography on a fine resist pattern by an electron beam drawing exposure method.

  A second method for imprinting the resin shown in FIG. 8 with a mold will be described. In FIG. 8, after going through the steps up to (A), (B), (C), (D), and (E) of FIG.

  Referring to FIG. 8A, an ultraviolet curable transparent resin layer 701 is applied on the surface-side sealing glass wafer 100, and ultraviolet rays are irradiated while pressing the transparent replica mold 505 on the transparent resin layer 701. And UV nanoimprint processing. The refractive index of the transparent resin layer 701 is about the same as the refractive index of glass. For example, the transparent resin layer 701 is made of a silicone resin. Instead of the transparent resin layer 701, a glass material such as spin-on glass may be used. Moreover, you may heat instead of ultraviolet irradiation. Next, when the transparent replica mold 505 is removed, as shown in FIG. 8B, the optical transmission window 11 of the antireflection structure of the parabolic uneven structure made of transparent resin is formed on one side of the glass wafer 100 for surface side sealing. can get. The transparent resin layer 701 in the region that does not constitute the optical transmission window 11 is removed by solvent cleaning.

  When the above-described process is performed on the other side of the glass wafer 100 for surface side sealing, as shown in (C) of FIG. 8, the other side of the glass wafer 100 for surface side sealing also has a parabolic uneven structure made of transparent resin. An optical transmission window 11 having an antireflection structure is obtained.

  In this way, the optical transmission windows 11 having a parabolic uneven structure and an antireflection structure are formed on both surfaces of the front-side sealing glass wafer 100 facing the cavity 1a. The above-described imprint processing gave a concavo-convex structure with a variation of ± 3% or less in both pitch and height. If the variation is large, the effect may not be obtained sufficiently or may vary within the window surface, but such a variation does not cause a problem.

  Before explaining the details of the manufacturing method of the hermetically sealed optical deflector package of FIG. 5, the optical deflector 2 of FIG. 2 will be described with reference to FIG. 9 which is a plan view of the optical deflector 2 of FIG. Reference: FIG. 1 of Patent Document 1).

  As shown in FIG. 9, the micromirror 21 is provided in the hollow portion of the support 22 and is supported by the support 22 so as to be swingable by torsion bars 22a and 22b. Piezoelectric actuators 22c, 22d, 22e, and 22f for transmitting torque to the torsion bars 22a and 22b are provided between the support 22 and the torsion bars 22a and 22b. Thereby, the micromirror 21 is driven to swing with respect to the XX axis.

  The support body 22 is provided in a hollow portion of the support body 23, and is supported by the support body 23 so as to be swingable by torsion bars 23a and 23b. Piezoelectric actuators 23c, 23d, 23e, and 23f for transmitting torque to the torsion bars 23a and 23b are provided between the support 23 and the torsion bars 23a and 23b. Thereby, the micromirror 21 is driven to swing with respect to the Y-Y axis.

  Next, details of the method for manufacturing the hermetically sealed optical deflector package of FIG. 5 will be described with reference to FIGS. 10 to 14 show the manufacturing process of the optical deflector silicon wafer 200, and FIG. 15 shows the bonding process by AuSn eutectic between the optical deflector silicon wafer 200 and the back side sealing glass wafer 300. Reference numeral 16 denotes a bonding process of the optical deflector silicon wafer 200 and the surface side sealing glass wafer 100 by Pb-free solder.

  First, referring to FIG. 10A, a single crystal silicon substrate (wafer) 901 having a thickness of about 525 μm is prepared. In the single crystal silicon substrate 901, a polysilicon buried electrode via 902 is formed in advance.

  Next, referring to FIG. 10B, the single crystal silicon substrate 901 is thermally oxidized to form silicon oxide layers 903 and 904 having a thickness of about 0.5 μm on the back surface and the front surface.

  Next, referring to FIG. 10C, about 50 nm thick Ti and about 150 nm thick Pt are sequentially formed on the silicon oxide layer 904 by sputtering, electron beam (EB) vapor deposition or the like. Thereby, the lower electrode layer 905 is formed. Next, a piezoelectric layer 906 made of lead zirconate titanate (PZT) having a thickness of about 3 μm is formed on the lower electrode layer 905 by a reactive arc discharge ion plating method. For the reactive arc discharge ion plating method, see Patent Documents 3, 4, and 5. Next, an upper electrode layer 907 made of Pt having a thickness of about 150 nm is formed on the piezoelectric layer 906 by sputtering, EB vapor deposition, or the like.

  Next, referring to FIG. 11A, the upper electrode layer 907 and the piezoelectric layer 906 are patterned using photolithography and dry etching. Next, the lower electrode layer 905 is patterned using photolithography and dry etching. Thus, the supports 22 and 23, the torsion bars 22a, 22b, 23a and 23b and the piezoelectric actuators 22c, 22d, 22e, 22f, 23c, 23d, 23e and 23f shown in FIG. 9 are formed.

  Next, referring to FIG. 11B, a silicon oxide layer 908 is formed on the entire surface by plasma CVD.

  Next, referring to FIG. 11C, contact holes 908a for the lower electrode layer 905, the upper electrode layer 907, and the polysilicon buried electrode via 902 are formed in the silicon oxide layer 908 using photolithography and dry etching. .

  Next, referring to FIG. 12A, a photoresist pattern is formed by photolithography, then AlSi (10% Si) is formed on the entire surface by sputtering, and AlSi wiring 909 is formed by lift-off. Form. Thereby, the lower electrode layer 905 and the upper electrode layer 907 are electrically connected to the peripheral pads.

  Next, referring to FIG. 12B, a photoresist pattern is formed by photolithography, then Ti and Ag are sequentially formed on the entire surface by sputtering, and reflection as micromirrors 21 is performed by lift-off. Layer 910 is formed.

  Next, referring to FIG. 12C, a photoresist pattern is formed by photolithography, then Ni and Au are sequentially formed on the entire surface by sputtering, and surface side sealing glass is formed by lift-off. An Au electrode 26 for bonding to the wafer 100 is formed. Ni acts as a barrier metal layer underlying the Au electrode 26.

  Next, referring to FIG. 13A, the surface side of the front-side sealing glass wafer 100 is attached to a support substrate 911 made of resin with an adhesive layer. That is, temporary bonding is performed.

  Next, referring to FIG. 13B, the back surface of the front surface side sealing glass wafer 100 is ground while holding the front surface side sealing glass wafer 100 by the support substrate 911, and polysilicon embedded electrode vias are processed. 902 is exposed. Next, the back surface of the front-side sealing glass wafer 100 is planarized by a chemical mechanical polishing (CMP) method.

  Next, referring to FIG. 13C, a silicon oxide layer 912 is formed on the entire back surface of the front-side sealing glass wafer 100 by sputtering or plasma CVD.

  Next, referring to FIG. 14A, an opening 912a for the polysilicon buried electrode 902 as the through electrode 24 and an opening for silicon processing are formed on the silicon oxide layer 912 by photolithography and dry etching. 912b is formed.

  Next, referring to FIG. 14B, a photoresist pattern is formed by photolithography, then Ni and Au are sequentially formed on the entire surface by sputtering, and backside sealing glass is formed by lift-off. An Au electrode 25 for bonding to the wafer 300 is formed. Note that Ni acts as a barrier metal layer underlying the Au electrode 25.

  Next, referring to FIG. 14C, a region corresponding to the silicon oxide layer 912 is masked on the surface of the silicon oxide layer 912 by a high frequency coupled plasma reactive ion etching (ICP-RIE) method mask, that is, by photolithography. A thick resist layer (not shown) is formed, and the single crystal silicon substrate 901 is removed by deep dry etching in an ICP-RIE apparatus using the thick resist layer as an etching mask.

  Note that the ICP-RIE method is an etching method suitable for anisotropically etching single crystal silicon, and thus the single crystal silicon substrate 901 can be etched vertically.

  In this way, the optical deflector silicon wafer 200 is completed.

  Next, referring to FIG. 15A, the optical deflector silicon wafer 200 is thermocompression bonded to the back side sealing glass wafer 300 while the support substrate 911 is temporarily bonded in a vacuum container. That is, AuSn eutectic bonding is performed. As a result, as shown in FIG. 15B, the AuSn eutectic electrode 5 is formed between the optical deflector silicon wafer 200 and the back surface side sealing glass wafer 300.

  Next, referring to FIG. 15B, the adhesive force of the support substrate 911 of the optical deflector silicon wafer 200 is irradiated with ultraviolet rays to weaken the adhesive force. As a result, as shown in FIG. The support substrate 911 is peeled off.

  Next, referring to FIG. 16A, after cleaning the AuSn eutectic bonded optical deflector silicon wafer 200 and back side sealing glass wafer 300, as described above, the front side sealing is performed in a vacuum vessel. The glass wafer 100 for fixing is joined with Pb-free solder. At that time, the pressure in the vacuum vessel is adjusted to 50000 Pa with high-purity nitrogen gas. A Pb-free solder ball 13 is printed on the front-side sealing glass wafer 100 and the Au electrode 12. As a result, as shown in FIG. 16B, the optical deflector silicon wafer 200 is sealed under reduced pressure by the sealing glass wafers 100 and 300. Finally, a chip level optical deflector package as shown in FIG. 2 is obtained by dicing.

  In the embodiment described above, a single crystal silicon wafer is used as the optical deflector wafer, but an SOI (Silicon On Insulator) wafer can also be used. In this case, as shown in FIG. 17, the back surface side sealing member 3 'is a flat plate, and it is not necessary to form a cavity in the back surface side sealing member 3'.

In the optical deflector package sealed under reduced pressure according to the present invention, a sine wave having a peak-to-peak voltage V _PP at a resonance frequency of 25 kHz and 20 V of the micromirror 21 is applied to the piezoelectric actuators 22c, 22d, 22e, and 22f for driving the horizontal XX axis. When a drive signal is applied and a sine wave drive signal having a non-resonant frequency of 60 Hz and a peak-to-peak voltage V _PP of 20 V is applied to the piezoelectric actuators 23c, 23d, 23e, and 23f for driving the vertical Y-Y axis, horizontal XX A deflection angle of the micromirror 21 of ± 9 ° on the axis and ± 7 ° on the vertical Y-Y axis was obtained, and the jitter at that time was ± 0.1%. On the other hand, in the optical deflector package without decompression, under the same driving conditions, a micro mirror deflection angle of ± 6 ° on the horizontal XX axis and ± 5 ° on the vertical YY axis can be obtained. When the jitter was ± 1%. Therefore, it was confirmed that the deflection angle was increased and the jitter was suppressed by the reduced pressure sealing.

  Sealed with glass having no antireflection function (conventional example 1), glass with antireflection function by a dielectric multilayer film (conventional example 2), and glass having antireflection function by a parabolic uneven structure (present invention). Projected images were evaluated using laser light sources of three wavelengths, ie, 640 nm (red), 532 nm (green), and 450 nm (blue), for the stopped optical deflector package. As a result, the reflection glare was large and the image luminance was low in Conventional Example 1, whereas the reflection glare was small and the image luminance was high in Conventional Example 1 and the present invention. In addition, when the incident angle of the incident laser with respect to the package is increased, that is, when the incident angle is oblique, the reflection glare is increased and the image luminance is decreased in the conventional example 2, and further, color-separated image noise is observed. On the other hand, in the present invention, the reflection glare is small and the image luminance is high as in the case of vertical incidence at any incident angle, and the color-separated image noise is small. Furthermore, even when a light source having a plurality of wavelengths is used as described above, for example, the concavo-convex structure may be provided at a pitch of 200 nm or less, which is half or less of the blue wavelength, which is the shortest wavelength. Thereby, it is possible to cope with all three colors of red, blue and green.

The present invention may apply to an optical deflector package other than hermetically sealed type.

1: Surface side sealing member 11: Optical transmission window 12: Au electrode 13: Pb-free solder ball 1a: Cavity 2: Optical deflector 21: Micromirror
22: Support
22a, 22b: torsion bars 22c, 22d, 22e, 22f: piezoelectric actuator 23: support
23c, 23d, 23e, 23f: Piezoelectric actuator 24: Through electrode 25: Au electrode 26: Au electrode 3: Back side sealing member 3a: Cavity 31: Through electrode 32: Au electrode 33: AuSn electrode 4: Au solder electrode 5 : AuSn eutectic electrode 100: Glass wafer for surface side sealing
200: optical deflector silicon wafer 300: glass wafer 501 for sealing the back surface side 1: silicon wafer
502: Resist pattern
503: Master mold
504: Transparent resin film
505: Transparent replica mold
506: Resist layer
507: Resist pattern
701: Transparent resin layer 901: Single crystal silicon substrate 902: Polysilicon embedded electrode via
905: Lower electrode layer 907: Upper electrode layer 908: Silicon oxide layer 909: AlSi wiring 911: Support substrate 912: Silicon oxide layer

Claims (7)

Support, an elastic member, a mirror which is swingably supported in the hollow portion of the support by the elastic member, the actuator for swing drive said mirror through said elastic member, the first through-electrode, and said An optical deflector having first and second joining electrodes provided above and below one through electrode ;
A cavity to secure the swinging space of the mirror across the optical deflector and a first, second sealing member for sealing,
The first sealing member has an optical transmission window having an antireflection function parabolic uneven structure facing the cavity and a third bonding electrode connected to the first bonding electrode;
An optical deflector package, wherein the second sealing member has a second through electrode and a fourth bonding electrode provided on the second through electrode and connected to the second bonding electrode . The pitch of the antireflection function parabolic concavo-convex structure is 1/2 or less of the wavelength of incident light, and the height of the antireflection function parabolic concavo-convex structure is 1 to 2 times the pitch. Optical deflector package. 2. The optical deflector package according to claim 1, wherein a central axis of the antireflection function parabolic uneven structure is perpendicular to a surface of the optical transmission window of the first sealing member and an angle is 60 to 80 °. .   2. The optical deflector package according to claim 1, wherein the antireflection function parabolic uneven structure is obtained by imprinting a transparent resin or glass formed on both surfaces of the first sealing member.   2. The optical deflector package according to claim 1, wherein each of the first and second sealing members has first and second cavities forming the cavity.   The optical deflector package according to claim 1, wherein the first sealing member has the cavity. The optical deflector package according to claim 1, wherein the first and second sealing members are made of glass.

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