Method for manufacturing vibration devices

Abstract

The present invention provides a method for manufacturing a vibration device that can suppress changes in the mass of the vibration element. [Solution] A method for manufacturing a vibration device 1 includes a vibration element 5, a base substrate 4 having a first bonding region 61r surrounding the vibration element 5 in a plan view, and a lid substrate 3 bonded to the first bonding region 61r of the base substrate 4 and hermetically sealing the vibration element 5 together with the base substrate 4, comprising: an activation step (WP) S34 or activation step (WP) S42 in which water vapor plasma is used to activate at least the first bonding region 61r of the base substrate 4; and a sealing step S53 in which the first bonding region 61r of the base substrate 4 and the lid substrate 3 are bonded together to hermetically seal the vibration element 5 in a housing space S surrounded by the base substrate 4 and the lid substrate 3.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a vibration device.

Background Art

[0002] In Patent Document 1, a neutral argon ion beam is irradiated onto a first metal layer formed on a base substrate on which a vibration element is mounted and a second metal layer formed on a lid to activate them, and the first metal layer and the second metal layer are joined to join the base substrate and the lid. A method is disclosed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the method described in Patent Document 1, when a neutral argon ion beam is irradiated onto the first metal layer of the base substrate, the vibration element is also irradiated with the neutral argon ion beam, so that the mass of the vibration element changes, and the frequency of the vibration element shifts or varies from the target frequency. There is a problem.

Means for Solving the Problems

[0005] A method for manufacturing a vibration device according to one aspect of the present application includes a vibration element, a base substrate having a bonding region surrounding the vibration element in a plan view, and a lid bonded to the bonding region of the base substrate and hermetically sealing the vibration element together with the base substrate. A method for manufacturing a vibration device, comprising: an activation step of activating at least the bonding region of the base substrate using water vapor plasma; and a sealing step of bonding the bonding region of the base substrate and the lid to hermetically seal the vibration element in a space surrounded by the base substrate and the lid. [Brief explanation of the drawing]

[0006] [Figure 1] A perspective view of a vibration device manufactured by the manufacturing method of the vibration device of Embodiment 1. [Figure 2] Figure 1 shows an exploded perspective view of the vibration device. [Figure 3] A cross-sectional view along line AA in Figure 1. [Figure 4] Cross-sectional view of a modified vibration device. [Figure 5] Overall flowchart of the manufacturing method for vibration devices. [Figure 6] A flowchart showing the details of the lid substrate preparation process. [Figure 7] A flowchart showing the details of the base substrate preparation process. [Figure 8] A flowchart showing the details of the mounting process. [Figure 9] A flowchart showing the details of the joining process. [Figure 10A] Diagram illustrating the activation process (WP). [Figure 10B] Diagram illustrating the activation process (WP). [Figure 11A] Diagram illustrating the Activation Aid (FAB) process. [Figure 11B] Diagram illustrating the Activation Aid (FAB) process. [Figure 12] A flowchart showing the details of the lid substrate preparation process according to Embodiment 2. [Figure 13] A flowchart showing the details of the joining process according to Embodiment 2. [Modes for carrying out the invention]

[0007] In embodiments of the present invention, the components shown in each drawing may be shown at different dimensional scales for clarity. Drawings sometimes depict three axes: the X, Y, and Z axes, which are mutually orthogonal.

[0008] In the following description, the tip side of the three-axis arrow may be described as the "plus side", and the base end side of the arrow may be described as the "minus side". The direction parallel to the X-axis may be described as the "X-axis direction", the direction parallel to the Y-axis may be described as the "Y-axis direction", and the direction parallel to the Z-axis may be described as the "Z-axis direction".

[0009] In the following, "planar view" means looking at an object from the plus side in the Z-axis direction of the object or from the minus side in the Z-axis direction. The plus side in the Z-axis direction may be described as "upward", and the minus side in the Z-axis direction may be described as "downward". In a planer view, the surface on the plus side in the Z direction may be described as the "upper surface", and the surface on the minus side in the Z direction, which is the opposite side, may be described as the "lower surface".

[0010] 1. Embodiment 1 In this section, the manufacturing method of the vibration device 1 according to Embodiment 1 will be described in the following order. 1.1. Configuration of the vibration device 1.2. Manufacturing method of the vibration device

[0011] 1.1. Configuration of the vibration device FIG. 1 is a perspective view of the vibration device 1 manufactured by the manufacturing method of the vibration device of this embodiment. FIG. 2 is an exploded perspective view of the vibration device 1 in FIG. 1. FIG. 3 is a cross-sectional view taken along line A-A of the vibration device 1 in FIG. 1.

[0012] As shown in FIG. 1, the vibration device 1 includes a package 2, a vibration element 5 provided in the package 2, and a semiconductor circuit 41 including an oscillation circuit. In this embodiment, the vibration device 1 is an oscillator. The vibration device 1 generates and outputs a reference signal by oscillating the vibration element 5. Note that the vibration device 1 may not be an oscillator. For example, the vibration device 1 may be an inertial sensor or the like.

[0013] The package 2 includes a base substrate 4, a lid substrate 3, and a metal layer 6. The metal layer 6 joins the base substrate 4 and the lid substrate 3. The metal layer 6 includes a first metal film 49 provided on the base substrate 4 and a second metal film 39 provided on the lid substrate 3, and is a bonding layer formed by activating and bonding the surfaces of the first metal film 49 and the second metal film 39 respectively, that is, a bonding layer formed by surface activated bonding (SAB).

[0014] Activated bonding proceeds by the free energy of the activated metal surface, and the bonding layer is completed by the diffusion and reorganization of metal atoms. Therefore, after bonding, there is no bonding interface, and a bonding strength close to the base material strength of silicon (Si) can be obtained. There is no gas generation due to bonding, and high hermetic sealing can be achieved.

[0015] In this embodiment, both the first metal film 49 and the second metal film 39 are formed of gold (Au). Therefore, the first metal film 49 and the second metal film 39 are Au-Au bonded by activated bonding.

[0016] In this embodiment, steam plasma treatment is used in the process of activating the bonding surface of the first metal film 49. As a result, the change in the mass of the vibration element 5 mounted on the base substrate 4 is suppressed, so that the vibration device 1 with high frequency accuracy and reliability can be manufactured without the frequency of the vibration element 5 shifting or varying from the target frequency. The details of the process of activating the bonding surface of the first metal film 49 will be described in section 1.2 below.

[0017] As shown in FIG. 2, the first metal film 49 is provided in the first bonding region 61r. The first bonding region 61r is a region to be bonded to the second metal film 39, and is a region surrounding the accommodation space S along the four sides of the upper surface 4t of the base substrate 4. The first metal film 49 is formed in one stroke in the first bonding region 61r.

[0018] The second metal film 39 is provided in the second bonding region 62r. ​​The second bonding region 62r is the region to be bonded to the first metal film 49, and although not shown in the figure, it is a region that surrounds the housing space S along the four sides of the lower surface of the lid substrate 3, similar to the first bonding region 61r. The second metal film 39 is formed in a single continuous line in the second bonding region 62r, similar to the first metal film 49.

[0019] 1.1.1. Base board configuration The upper surface 4t of the base substrate 4 is provided with multiple mounting electrodes 47, multiple bumps 56 made of conductive bonding members, and multiple alignment marks 4m.

[0020] The vibration element 5 is mounted on the upper surface 4t of the base substrate 4 by being joined to multiple bumps 56 in a cantilevered manner. In this embodiment, the bumps 56 are made of gold, and the bumps 56 and the vibration element 5 are joined by Au-Au diffusion bonding using ultrasonic vibration or the like.

[0021] As shown in Figure 3, the base substrate 4 includes a silicon substrate 40, a semiconductor circuit 41 provided on the upper surface 4t of the base substrate 4, a mounting electrode 47 provided on the upper surface 4t of the base substrate 4, and an external terminal 25 provided on the lower surface 4b of the base substrate 4.

[0022] The silicon substrate 40 is formed by cutting a silicon wafer into individual pieces. The silicon substrate 40 may also be formed from a wafer made of a semiconductor material other than silicon, such as Ge, GaP, GaAs, or InP.

[0023] The semiconductor circuit 41 is integrally provided on the silicon substrate 40. Therefore, in this embodiment, the vibration device 1 can be miniaturized. The semiconductor circuit 41 may also be formed on the lower surface 4b side of the base substrate 4.

[0024] The mounting electrode 47 is electrically connected to the semiconductor circuit 41 via wiring 46 that penetrates the insulating layer 42.

[0025] The external terminal 25 is electrically connected to the semiconductor circuit 41 via a through-silicon via (TSV) 45 provided in the through-hole 43. The external terminal 25 and the through-silicon via 45 are insulated from the silicon substrate 40 by an insulating layer 44.

[0026] 1.1.2. Configuration of the vibrating element The vibration element 5 includes a vibration substrate 51, excitation electrodes 52 provided on the upper and lower surfaces of the vibration substrate 51, terminals 53 joined to the bump 56, and wiring 54 connecting the terminals 53 and the excitation electrodes 52.

[0027] The excitation electrode 52 is electrically connected to the bump 56 via the wiring 54 and terminal 53, thereby electrically connected to the oscillation circuit of the semiconductor circuit 41, and vibrates when a voltage is applied by the oscillation circuit. In this embodiment, the excitation electrode 52, terminal 53, and wiring 54 are made of the same conductive material, which in this embodiment is gold.

[0028] In this embodiment, the vibrating element 5 is a quartz crystal oscillator. However, the vibrating element 5 may also be a SAW (Surface Acoustic Wave) resonator, other piezoelectric oscillators, or MEMS (Micro Electro Mechanical Systems) oscillators.

[0029] As the substrate material for the vibrating element 5, piezoelectric materials such as piezoelectric single crystals like quartz, lithium tantalate, or lithium niobate, piezoelectric ceramics such as lead zirconate titanate, or silicon semiconductor materials can be used. As the excitation means for the vibrating element 5, a piezoelectric effect may be used, or electrostatic driving by Coulomb force may be used.

[0030] 1.1.3. Configuration of the Cover Substrate The lid substrate 3 is called a lid and is a piece of silicon wafer. Since both the lid substrate 3 and the silicon substrate 40 are made of silicon, the coefficients of linear expansion of the lid substrate 3 and the silicon substrate 40 are equal, and the generation of thermal stress caused by thermal expansion is suppressed. Therefore, the vibration characteristics of the vibration device 1 are improved. In addition, since the vibration device 1 can be formed by a semiconductor process, the vibration device 1 can be manufactured with high precision and miniaturized. The lid substrate 3 may be formed from a wafer made of a semiconductor material other than silicon, such as Ge, GaP, GaAs, or InP.

[0031] The lid substrate 3 has a bottomed recess 31 that opens on its lower surface and forms a housing space S in which the vibration element 5 is housed. A porous portion 32 is provided inside the recess 31. The second metal film 39 is also provided on the lower surface of the porous portion 32. Alternatively, the porous portion 32 may be omitted, and the second metal film 39 may be provided inside the recess 31.

[0032] The lid substrate 3 is bonded to the first bonding region 61r of the base substrate 4, and together with the base substrate 4, hermetically seals the vibrating element 5 in the housing space S. The housing space S is preferably in a reduced-pressure state, more preferably in a near-vacuum state. This reduces the viscous resistance experienced by the vibrating element 5 housed in the housing space S, thereby improving the oscillation characteristics of the vibrating element 5.

[0033] In this embodiment, the containment space S can be rephrased as a vacuum chamber, and the package 2 can be rephrased as a vacuum container. As described above, package 2 is provided with a vibrating element 5 and a semiconductor circuit 41 including an oscillation circuit. Therefore, the vibration device 1 of this embodiment can have a smaller package size than a device with a vibrating element and an IC chip with an oscillation circuit packaged in a ceramic package. Furthermore, as will be described later, the packaging can be completed in the silicon wafer process, which improves the reliability and performance of the vibration device 1.

[0034] 1.1.4. Configuration of a vibration device in a modified example A modified example of the vibration device 11 will be described with reference to Figure 4. Figure 4 is a cross-sectional view of the modified example of the vibration device 11.

[0035] As shown in Figure 4, the vibration device 11 has a first substrate 7, a second substrate 8, a third substrate 9, and a circuit element 10. The third substrate 9 has a vibration element 91.

[0036] In the modified example, the first substrate 7, the second substrate 8, and the third substrate 9 are each made of quartz crystal substrates. By constructing the first substrate 7, the second substrate 8, and the third substrate 9 from quartz crystal substrates, the thermal expansion coefficients of the first substrate 7, the second substrate 8, and the third substrate 9 can be made approximately equal. Therefore, thermal stress caused by the difference in thermal expansion coefficients of the first substrate 7, the second substrate 8, and the third substrate 9 becomes less likely to occur, the vibration element 91 is less likely to be subjected to stress, and accuracy and reliability can be improved.

[0037] In this modified example, the first substrate 7, the second substrate 8, and the third substrate 9 are each AT-cut quartz substrates. The quartz substrate is not limited to AT-cut quartz substrates, and may have other cut angles, such as Z-cut, SC-cut, ST-cut, BT-cut, etc. By using quartz substrates with the same cut angle for the first substrate 7, the second substrate 8, and the third substrate 9, and aligning the orientation of their crystal axes, thermal stress caused by the difference in thermal expansion coefficients of the first substrate 7, the second substrate 8, and the third substrate 9 becomes less likely to occur, and the vibrating element 91 becomes even less susceptible to stress.

[0038] Furthermore, at least one of the first substrate 7 and the second substrate 8 may be a quartz substrate with a different cut angle than the third substrate 9, or at least one of the first substrate 7 and the second substrate 8 may be a quartz substrate with the same cut angle but whose crystal axis orientation does not coincide with that of the third substrate 9.

[0039] The third substrate 9 has a frame-shaped frame portion 93 and a vibrating portion 95 that is connected to the frame portion 93 and positioned inside the frame portion 93. The vibrating part 95 is thinner in the Z-axis direction than the frame part 93, the upper surface of the vibrating part 95 is located on the negative Z-axis side than the upper surface of the frame part 93, and the lower surface of the vibrating part 95 is located on the positive Z-axis side than the lower surface of the frame part 93. This makes it possible to suppress contact between the vibrating part 95 and the first substrate 7 and the second substrate 8. Excitation electrodes 92 are provided on the upper and lower surfaces of the vibrating section 95, respectively.

[0040] A third metal film 67 is provided in the third bonding region 67r on the upper surface 7t of the first substrate 7. A fourth metal film 69 is provided in the fourth bonding region 69r on the lower surface 8b of the second substrate 8. A fifth metal film 66a is provided on the lower surface of the third substrate 9, facing the third metal film 67, and a fifth metal film 66b is provided on the upper surface of the third substrate 9, facing the fourth metal film 69. The third metal film 67, the fourth metal film 69, and the fifth metal films 66a and 66b are all made of gold.

[0041] The third metal film 67 on the first substrate 7 and the fifth metal film 66a on the third substrate 9 are joined by activation bonding to form a metal layer 6a. Therefore, the metal layer 6a is a bonding layer in which the third metal film 67 and the fifth metal film 66a are bonded together by Au-Au bonding.

[0042] The fourth metal film 69 on the second substrate 8 and the fifth metal film 66b on the third substrate 9 are joined by activation bonding to form a metal layer 6b. Therefore, the metal layer 6b is a bonding layer in which the fourth metal film 69 and the fifth metal film 66b are Au-Au bonded.

[0043] In this way, the first substrate 7 and the third substrate 9 are joined by a metal layer 6a, and the second substrate 8 and the third substrate 9 are joined by a metal layer 6b, thereby joining the first substrate 7 and the second substrate 8 via the third substrate 9, and a housing space S is formed between the first substrate 7 and the second substrate 8. The vibration element 91 is hermetically sealed in the housing space S.

[0044] Multiple electrode patterns 81 and 82 are provided on the upper surface 8t of the second substrate 8. The multiple electrode patterns 81 and 82 are electrically connected to the excitation electrode 92 and external terminals 26, etc., via through electrodes 87.

[0045] A circuit element 10 is placed on the upper surface 8t side of the second substrate 8. The circuit element 10 is an IC (Integrated Circuit) chip. The circuit element 10 has an oscillation circuit that causes the vibration element 91 to oscillate, and is electrically connected to the excitation electrode 92 via a conductive bonding member 84 and an electrode pattern 81.

[0046] Multiple external terminals 26 are provided on the lower surface 7b of the first substrate 7. These multiple external terminals 26 are electrically connected to excitation electrodes 92, circuit elements 10, etc., via through electrodes 87.

[0047] 1.2. Method for Manufacturing Vibration Devices Next, the manufacturing method of the vibration device 1 will be described with reference to the drawings. Figure 5 is an overall flowchart of the manufacturing method for the vibration device 1. Figure 6 is a flowchart detailing the lid substrate preparation process S1. Figure 7 is a flowchart detailing the base substrate preparation process S3. Figure 8 is a flowchart detailing the mounting process S4. Figure 9 is a flowchart detailing the bonding process S5. Figures 10A and 10B are explanatory diagrams for the activation process (WP) S34 and S42. Figures 11A and 11B are explanatory diagrams for the activation process (FAB) S52.

[0048] As shown in Figure 5, the manufacturing method of the vibration device 1 includes a lid substrate preparation step S1, a vibration element preparation step S2, a base substrate preparation step S3, a mounting step S4, a bonding step S5, a thinning step S6, a pad formation step S7, a thinning step S8, a piece formation step S9, an annealing and gettering step S10, and a frequency adjustment and inspection step S110.

[0049] <Lid substrate preparation process S1> As shown in Figure 6, the lid substrate preparation step S1 includes a cleaning step S11, an etching mask formation step S12, a recess formation step S13, and a bonding layer formation step S14.

[0050] In the cleaning process S11, a silicon wafer for forming the lid substrate 3 is prepared, and the silicon wafer is cleaned using a wafer cleaning device to remove contaminants and deposits from the surface of the silicon wafer.

[0051] In etching mask formation step S12, an etching mask for forming recesses 31 is formed on the silicon wafer by photolithography.

[0052] In the recess formation step S13, the etching mask formed in the etching mask formation step S12 is used to form the recess 31 on the silicon wafer.

[0053] In the bonding layer formation step S14, a second metal film 39 is formed by sputtering or the like. The second metal film 39 consists of an Au / Ti thin film and is formed by depositing titanium (Ti) on the entire surface of the second bonding region 62r and the recess 31, and then depositing gold.

[0054] In this embodiment, the second metal film 39 is an ultrathin film of about 30 nm. In the Au / Ti thin film, the titanium film thickness is about 10 nm, and the gold film thickness is 20 nm. By forming the second metal film 39 as an ultrathin film, the surface roughness of the MP (mirror polished) surface of the silicon wafer prepared in the cleaning step S11 is left as is, preventing an increase in roughness, and the surface roughness is suppressed to Ra ≤ 1 nm or less, preferably Ra ≤ 0.3 nm, thereby maximizing the bonding force due to surface tension and suppressing voids at the bonding interface.

[0055] <Base substrate preparation process S3> As shown in Figure 7, the base substrate preparation step S3 includes the manufacturing step S31, the bonding layer formation step S32, the bump formation step S33, and the activation step (WP) S34.

[0056] In manufacturing step S31, a silicon wafer is prepared for the silicon substrate 40, and a semiconductor circuit 41 including an oscillator circuit is formed on the silicon wafer.

[0057] In the bonding layer formation step S32, titanium and gold are sputtered onto the insulating layer 42, and the resulting Au / Ti thin film is photolithographed to form a first metal film 49 in the first bonding region 61r, and a mounting electrode 47 is also formed.

[0058] In the bump formation process S33, bumps 56 made of gold are formed by a plating method or the like. Since no resin such as paste is used for the bumps 56, it is easy to maintain the vacuum level of the containment space S after sealing the containment space S.

[0059] In the activation step (WP)S34, the upper surface of the first metal film 49, that is, the surface of the first metal film 49 that is bonded to the second metal film 39 of the lid substrate 3, is subjected to water vapor plasma treatment. Water vapor plasma treatment is a plasma treatment using water vapor (H2O). In this embodiment, the water vapor plasma treatment is performed using Aqua Plasma® cleaner from Samco Corporation.

[0060] As shown in Figure 10A, the first metal film 49 consists of a surface layer Au film 49a and a lower layer Ti film 49b, and residue r is attached to the upper surface of the first metal film 49, that is, the surface of the Au film 49a. In this embodiment, the thickness of the Au film 49a is approximately 150 nm.

[0061] The residue r is an organic residue such as a resist used in the bonding layer formation process S32. The presence of residue r on the surface of the first metal film 49 reduces the surface activity of the Au film 49a.

[0062] In the subsequent bump formation process S33, when bumps 56 are formed by the plating method, the activity of the Au on the surface of the Au film 49a is further reduced due to oxidation, etc., caused by resist formation, electroless plating film deposition, and resist peeling.

[0063] By performing water vapor plasma treatment on the upper surface 4t of the base substrate 4, the residue r on the surface of the Au film 49a of the first metal film 49 is removed, and the Au2O3 on the surface of the oxidized Au film 49a is ionized by the plasma, and the H + The surface of the Au film 49a, which is reduced and activated by the reducing action of the water vapor plasma, is modified with hydroxyl groups (-OH) that are also reduced by the water vapor plasma.

[0064] The hydroxyl groups have the effect of protecting the surface of the Au film 49a. When the surface of the Au film 49a is modified with hydroxyl groups, the activity of the surface of the Au film 49a is maintained even if the surface of the Au film 49a is exposed to the atmosphere before the fixation step S41 (see Figure 8) and the sealing step S53 (see Figure 9) are carried out. According to the inventors' studies, it has been found that the activity of the surface of the Au film 49a is maintained for at least 24 hours when exposed to the atmosphere.

[0065] <Mounting process S4> As shown in Figure 8, the mounting process S4 includes a fixing process S41 and an activation process (WP) S42.

[0066] In the fixing process S41, the vibration element 5 prepared in the vibration element preparation process S2 is joined to the bump 56. When joining the vibration element 5 to the bump 56, the base substrate 4 is heated to approximately 200°C. At this time, organic matter and the like may adhere as residue r to the upper surface 4t of the base substrate 4 and the surface of the first metal film 49.

[0067] Therefore, in this embodiment, after the fixing step S41 and immediately before the bonding step S5, an activation step (WP) S42 is performed. In the activation step (WP) S42, water vapor plasma treatment is performed to remove residue r from the upper surface 4t of the base substrate 4 and the surface of the first metal film 49. At this time, the surface of the excitation electrode 52 of the vibrating element 5 is also exposed to the water vapor plasma, but unlike when a neutral argon ion beam is irradiated, the change in mass of the excitation electrode 52 is suppressed, and the frequency of the vibrating element 5 does not shift or fluctuate from the target frequency.

[0068] In this embodiment, water vapor plasma treatment is performed in both the activation step (WP)S34 and the activation step (WP)S42, but depending on the situation, either the activation step (WP)S34 or the activation step (WP)S42 may be omitted. In any case, by performing water vapor plasma treatment in either or both of the activation steps (WP)S34 and the activation step (WP)S42, the activity of the surface of the Au film 49a of the first metal film 49 is improved and maintained.

[0069] <Joining process S5> As shown in Figure 9, the bonding process S5 includes an alignment process S51, an activation process (FAB) S52, and a sealing process S53. The bonding process S5 is performed in a vacuum using a room-temperature wafer bonding apparatus. In the bonding process S5, in a vacuum, the silicon wafer on which the base substrate 4 with the vibration element 5 is mounted and the silicon wafer on which the lid substrate 3 is formed are bonded together to hermetically seal the vibration element 5 in the housing space S.

[0070] In the alignment process S51, both silicon wafers are placed in the room-temperature wafer bonding apparatus with their bonding surfaces facing each other, and the alignment marks on each silicon wafer are aligned on the image using an IR (infrared) camera.

[0071] In the activation step (FAB) S52, the surface of the second metal film 39 provided on the junction surface of the lid substrate 3, that is, the second junction region 62r, is activated by a high-purity argon (Ar) fast atom beam (FAB).

[0072] As shown in Figure 11A, the second metal film 39 consists of a surface layer Au film 39a and a lower layer Ti film 39b, and residue r is attached to the lower surface of the second metal film 39, that is, the surface of the Au film 39a.

[0073] By irradiating the bonding surface of the lid substrate 3 with a high-speed atomic beam, the residue r on the surface of the Au film 39a of the second metal film 39 is removed, as shown in Figure 11B, and the surface of the second metal film 39 is activated. Furthermore, since the outermost layer of the Au film 39a is amorphous by irradiation with a high-speed atomic beam, a high level of activity can be achieved.

[0074] In the activation process (FAB) S52, the high-speed atomic beam does not irradiate the vibrating element 5 mounted on the base substrate 4. Therefore, changes in the mass of the excitation electrode 52 are suppressed, and the frequency of the vibrating element 5 does not shift or fluctuate from the target frequency.

[0075] In the sealing process S53, the two silicon wafers are brought into contact and bonded together, thereby hermetically sealing the vibration element 5 into the housing space S. By bringing the surface of the first metal film 49, which has been activated by water vapor plasma treatment, into contact with the surface of the second metal film 39, which has been activated by irradiation with a high-speed atomic beam, the first metal film 49 and the second metal film 39 are activated and bonded together.

[0076] The activation bonding of the first metal film 49 and the second metal film 39 forms a bonding layer consisting of an Au-Au bonded metal layer 6, bonding the silicon wafers together and hermetically sealing the vibration element 5 in the housing space S. In this embodiment, the metal layer 6 includes a bonding layer with a thickness of approximately 170 nm, consisting of an Au film 49a with a thickness of approximately 150 nm and an Au film 39a with a thickness of approximately 20 nm.

[0077] Since the activation bonding of the first metal film 49 and the second metal film 39 is performed solely by activated surface free energy, there is no need to pressurize the silicon wafers when bringing them into contact, thus reducing the load on the room-temperature wafer bonding apparatus. However, the silicon wafers may be pressed when bringing them into contact, as this pressurization corrects the warping of the silicon wafers and makes the bonding at room temperature (room temperature) more reliable.

[0078] Return to Figure 5. In the thinning process S6, the silicon wafer of the base substrate 4 is ground and polished. Specifically, the silicon substrate 40 of the base substrate 4 is thinned. Then, through holes 43 and through electrodes 45 are formed in the silicon substrate 40. Dry polishing may be performed as a finishing step in thinning the silicon substrate 40. Dry polishing can release the stress caused by grinding.

[0079] In the pad formation process S7, external terminals 25 that are electrically connected to the through-electrode 45 are formed on the base substrate 4. In the thinning process S8, the silicon wafer on the lid substrate 3 side is ground and polished to make it thinner. In the individualization process S9, the bonded silicon wafer is diced to separate it into individual vibration devices 1.

[0080] In the annealing and gettering process S10, water molecules (H2O, see Figure 10B) adsorbed (associated) on the inner wall of the containment space S are detached by annealing and gettered onto the Ti films 39b, 49b, etc. Performing the annealing and gettering process S10 maintains the vacuum level in the containment space S, improving the quality and reliability of the vibration device 1. The annealing and gettering process S10 can be performed at any point between the sealing process S53 and the frequency adjustment and inspection process S110. In particular, if performed after the individualization process S9, the heat capacity required to heat the vibration device 1 is reduced, allowing for more efficient heating and enabling the annealing and gettering process S10 to be completed in a shorter time than if performed before the individualization process S9.

[0081] In the frequency adjustment and inspection process S110, the frequency of the vibration device 1 is adjusted using a PLL (phase locked loop) circuit or the like. Vibration device 1 can be manufactured through the above process.

[0082] As described above, in the manufacturing method of the vibration device 1 of this embodiment, the process up to packaging can be completed in the silicon wafer state, so a small and reliable vibration device 1 can be manufactured.

[0083] Furthermore, in the manufacturing method of the vibration device 1 of this embodiment, the bonding surface of the base substrate 4 is activated by water vapor plasma, so that the base substrate 4 and the lid substrate 3 can be firmly bonded, the airtightness of the housing space S is well maintained, and changes in the mass of the vibration element 5 mounted on the base substrate 4 are avoided, so that a vibration device 1 with high frequency accuracy and reliability can be manufactured.

[0084] As described above, the manufacturing method of the vibration device 1 of this embodiment provides the following effects. The manufacturing method for the vibration device 1 of this embodiment includes a vibration element 5, a base substrate 4 having a first bonding region 61r as a bonding region surrounding the vibration element 5 in a plan view, and a cover substrate 3 as a cover that is bonded to the first bonding region 61r of the base substrate 4 and hermetically seals the vibration element 5 together with the base substrate 4, and comprises an activation step (WP) S34 or activation step (WP) S42 in which water vapor plasma is used to activate at least the first bonding region 61r of the base substrate 4, and a sealing step S53 in which the first bonding region 61r of the base substrate 4 and the cover substrate 3 are bonded together to hermetically seal the vibration element 5 in a housing space S which is a space surrounded by the base substrate 4 and the cover substrate 3.

[0085] Thus, the manufacturing method of the vibration device 1 of this embodiment involves activating the first bonding region 61r of the base substrate 4 having the vibration element 5 using water vapor plasma. Therefore, changes in the mass of the vibrating element 5, and resulting shifts or variations in the frequency of the vibrating element 5 from the target frequency are suppressed, making it possible to manufacture a vibrating device 1 with high frequency accuracy and reliability.

[0086] The manufacturing method of the vibration device 1 of this embodiment further includes a fixing step S41 in which a vibration element 5 is fixed to a base substrate 4, and the activation step (WP) S42 is performed after the fixing step S41.

[0087] Therefore, since the decrease in activity of the first bonding region 61r can be suppressed, the change in mass of the vibrating element 5 and the shift or variation of the frequency of the vibrating element 5 from the target frequency can be suppressed, and a vibrating device 1 with high frequency accuracy and reliability can be manufactured.

[0088] The manufacturing method of the vibration device 1 of this embodiment further includes a fixing step S41 in which a vibration element 5 is fixed to a base substrate 4, and the activation step (WP) S34 is performed before the fixing step S41.

[0089] Since the first bonding region 61r is activated by water vapor plasma, its activity can be maintained for a long time. Therefore, even if the activation process (WP) S34 is performed before the fixing process S41, the activity is maintained. Thus, the base substrate 4 and the lid substrate 3 can be firmly bonded, and a vibration device 1 with high frequency accuracy and reliability can be manufactured.

[0090] The manufacturing method of the vibration device 1 of this embodiment further includes an activation step (FAB) S52, which is a step of activating the surface of the second metal film 39, which is the side of the lid substrate 3 that is bonded to the first bonding region 61r, using a high-speed atomic beam, before the sealing step S53.

[0091] The surface of the second metal film 39 is activated by a high-speed atomic beam before the sealing step S53. Therefore, the base substrate 4 and the lid substrate 3 can be firmly joined, and a vibration device 1 with high frequency accuracy and reliability can be manufactured.

[0092] 2. Embodiment 2 A method for manufacturing the vibration device 1 according to Embodiment 2 will be described with reference to Figures 12 and 13. Figure 12 is a flowchart detailing the lid substrate preparation step S1 according to Embodiment 2. Figure 13 is a flowchart detailing the bonding step S5 according to Embodiment 2.

[0093] The manufacturing method of the vibration device 1 according to Embodiment 2 differs from the manufacturing method of the vibration device 1 according to Embodiment 1 in that, as shown in Figure 12, the lid substrate preparation step S1 includes an activation step (WP) S15, and as shown in Figure 13, the bonding step S5 does not include an activation step (FAB) S52.

[0094] In the activation step (WP)S15, the upper surface of the second metal film 39 on the lid substrate 3, that is, the surface of the second metal film 39 that is junction with the first metal film 49 on the base substrate 4, is subjected to water vapor plasma treatment.

[0095] By performing water vapor plasma treatment, the residue r on the surface of the second metal film 39 is removed, and the Au2O3 on the surface of the oxidized Au film 39a is ionized by the plasma, and the H2O is removed. + It is reduced and activated by the reducing action of [unspecified substance]. Then, the surface of the activated Au film 39a is modified with hydroxyl groups (-OH).

[0096] As described above, since the hydroxyl groups have the effect of protecting the surface of the Au film 39a, even if the surface of the Au film 39a is exposed to the atmosphere before the sealing step S53 is carried out, the activity of the surface of the Au film 39a is maintained. Therefore, in the manufacturing method of the vibration device 1 according to Embodiment 2, it is not necessary to irradiate the bonding surface of the lid substrate 3 with a high-speed atomic beam in the bonding step S5.

[0097] As described above, the manufacturing method of the vibration device 1 of Embodiment 2 provides the following additional effects in addition to the effects of Embodiment 1. The manufacturing method of the vibration device 1 of Embodiment 2 further includes an activation step (WP) S15, which is a step of activating the surface of the second metal film 39, which is the side of the lid substrate 3 that is bonded to the first bonding region 61r, using water vapor plasma, before the sealing step S53.

[0098] The surface of the second metal film 39 is activated by water vapor plasma before the sealing process S53. Thus, the base substrate 4 and the lid substrate 3 can be firmly bonded, and a vibration device 1 with high frequency accuracy and reliability can be manufactured.

[0099] Although preferred embodiments have been described above, the present invention is not limited to the embodiments described above. The configuration of each part of the present invention can be replaced with any configuration that performs a similar function to the embodiments described above, and any configuration can be added. [Explanation of Symbols]

[0100] 1…Vibration device, 2…Package, 3…Lid substrate, 4…Base substrate, 4b…Bottom surface, 4m…Alignment mark, 4t…Top surface, 5…Vibration element, 6…Metal layer, 6a…Metal layer, 6b…Metal layer, 7…First substrate, 7t…Top surface, 7b…Bottom surface, 8…Second substrate, 8t…Top surface, 8b…Bottom surface, 9…Third substrate, 10…Circuit element, 11…Vibration device, 25,26…External terminals, 31…Recess, 32…Porous part, 39…Second metal film, 39a…Au film, 39b…Ti film, 40…Silicon substrate, 41…Semiconductor circuit, 42…Insulating layer, 43…Through hole, 44…Insulating layer, 45 ...through electrode, 46...wiring, 47...mount electrode, 49...first metal film, 49a...Au film, 49b...Ti film, 51...vibrating substrate, 52...excitation electrode, 53...terminal, 54...wiring, 56...bump, 61r...first bonding region, 62r...second bonding region, 66a...fifth metal film, 66b...fifth metal film, 67...third metal film, 67r...third bonding region, 69...fourth metal film, 69r...fourth bonding region, 81,82...electrode pattern, 84...conductive bonding member, 87...through electrode, 91...vibrating element, 92...excitation electrode, 93...frame part, 95...vibrating part, S...housing space, r...residue.

Claims

1. A method for manufacturing a vibration device, comprising: a vibrating element; a base substrate having a bonding region surrounding the vibrating element in a plan view; and a lid bonded to the bonding region of the base substrate and hermetically sealing the vibrating element together with the base substrate, An activation step in which water vapor plasma is used to activate at least the bonding region of the base substrate, A sealing step of joining the bonding region of the base substrate and the cover, thereby hermetically sealing the vibration element in the space enclosed by the base substrate and the cover, A method for manufacturing a vibrating device having [a specific feature].

2. The process further includes a fixing step of fixing the vibration element to the base substrate, The activation step is performed after the fixation step. A method for manufacturing a vibration device according to claim 1.

3. The process further includes a fixing step of fixing the vibration element to the base substrate, The activation step is performed before the fixation step. A method for manufacturing a vibration device according to claim 1.

4. Prior to the sealing step, the process further includes a step of activating the side of the lid that is joined to the joining region using the water vapor plasma. A method for manufacturing a vibration device according to claim 1.

5. Prior to the sealing step, the method further comprises a step of activating the side of the lid that is joined to the joining region using a high-speed atomic beam. A method for manufacturing a vibration device according to claim 1.

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