Semiconductor substrate, manufacturing method thereof, actuator, ejection head, ejection device, wearable terminal device, and eye tracking device

Abstract

To provide a semiconductor substrate on which a piezoelectric film having high piezoelectric properties can be formed.SOLUTION: A semiconductor substrate according to the present invention includes a silicon single crystal substrate, a metal film formed on the silicon single crystal substrate and oriented in (111), and an oxide electrode thin film having a metal oxide layer SrRuO3 formed on the metal film, and the orientation of the SrRuO3 film is (001).SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a semiconductor substrate, a manufacturing method thereof, an actuator, a discharge head, a discharge device, a wearable terminal device, and an eye-tracking device. [Background technology]

[0002] In Patent Document 1, γ-Al epitaxially grown on a silicon single crystal substrate is 2 O 3 A single crystal film and the γ-Al 2 O 3 A perovskite-structured pseudocubic metal oxide layer, LaNiO, formed on a single crystal film 3 or SrRuO 3 and a Pb(Zr,Ti)O thin film formed on the oxide thin film. 3 and an oriented ferroelectric thin film consisting of the ferroelectric thin film, the oxide electrode thin film, and the γ-Al 2 O 3 The single crystal film and the silicon single crystal substrate are both oriented in the (001) direction. According to this structure, the γ-Al epitaxially grown on the silicon single crystal substrate is 2 O 3 Since the oxide thin film is formed on the single crystal film, the crystallinity of the oxide thin film can be improved. 2 O 3 To form a thin oxide electrode film on the single crystal film, γ-Al 2 O 3 It is possible to improve the adhesion between the single crystal film and the oxide electrode thin film. Note that the pseudocubic crystal is disclosed as a crystal structure having two cubic crystals stacked inside an orthorhombic crystal. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5228188 Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present invention is to provide a semiconductor substrate on which a piezoelectric film having high piezoelectric properties can be formed. [Means for solving the problem]

[0005] The semiconductor substrate according to the present invention comprises a silicon single crystal substrate, a metal film formed on the silicon single crystal substrate and oriented in (111), and a metal oxide layer SrRuO 3 and an oxide electrode thin film having the SrRuO 3 The film is characterized by its (001) orientation. Effect of the Invention

[0006] It is possible to provide a semiconductor substrate on which a piezoelectric film having high piezoelectric properties can be formed. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a schematic diagram (cross-sectional view) of a first embodiment. [Diagram 2] 2 is an example of an X-ray diffraction pattern according to the first embodiment. [Diagram 3] FIG. 1 shows the correlation between the half-widths of the peaks of Pt(111) and SrRuO3(001). [Figure 4] FIG. 13 is a diagram showing the relationship between the half-width of the Pt(111) peak and the orientation ratio of SrRuO3. [Diagram 5] 1 is an example of an X-ray diffraction pattern of a comparative example. [Figure 6] FIG. 1 is a diagram showing the relationship between the film formation temperature and the orientation rate of SrRuO3(001). [Figure 7] FIG. 4 is a schematic diagram (cross-sectional view) of a second embodiment. [Figure 8] FIG. 1 is a diagram showing the relationship between the orientation rate and the piezoelectric constant (e31) of SrRuO3. [Figure 9]FIG. 11 is a schematic diagram (cross-sectional view) of a third embodiment. [Figure 10] FIG. 13 is a schematic diagram of a fourth embodiment. [Figure 11] FIG. 13 is a schematic diagram (cross-sectional view) of a fourth embodiment. [Figure 12] FIG. 13 is a schematic diagram of a fifth embodiment. [Figure 13] FIG. 13 is a schematic diagram (cross-sectional view) of a fifth embodiment. [Figure 14] FIG. 13 is a conceptual diagram (cross-sectional view) illustrating the function of the sixth embodiment. [Figure 15] FIG. 13 is a conceptual diagram (plan view) illustrating the function of the sixth embodiment. [Figure 16] FIG. 13 is a schematic diagram of a sixth embodiment. [Figure 17] FIG. 13 is a schematic diagram (cross-sectional view) of a sixth embodiment. [Figure 18] FIG. 13 is a schematic diagram of a seventh embodiment. [Figure 19] FIG. 23 is a conceptual diagram illustrating the function of the eighth embodiment. [Figure 20] FIG. 13 is a schematic diagram of the ninth embodiment. [Figure 21] FIG. 13 is a diagram illustrating an optical system according to a ninth embodiment. [Figure 22] 13 is an example of a movable device according to the ninth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the description of the drawings, the same elements are given the same reference numerals, and duplicated description will be omitted.

[0009] Piezoelectric elements used in piezoelectric MEMS (Micro Electro Mechanical Systems) devices are generally made of layers with various roles, with silicon (Si) as the substrate material for ease of processing and strength. SiO 2An oxide layer such as Pt or Ir is formed on top of it, and an electrode layer such as Pt or Ir is formed on top of it to apply voltage. TiO is placed between the oxide layer and the electrode layer to ensure adhesion. 2 In some cases, metal oxide materials such as Pt and Ir are inserted. The piezoelectric film is formed on an electrode layer, but since the preferred crystal plane of electrode materials such as Pt and Ir is the (111) orientation, if the piezoelectric film is directly deposited on the electrode, it will grow in the (111) orientation. In actuator devices such as IJ (Inkjet) heads and MEMS mirrors, the performance is improved by increasing the piezoelectric constant of the piezoelectric film, and since the piezoelectric constant is maximum in the (001) orientation, it is not desirable to deposit the film directly on the electrode. Therefore, it is already known to insert a seed layer between the electrode and the piezoelectric film to align the piezoelectric film in the (001) orientation.

[0010] In Patent Document 1, γ-Al epitaxially grown on a silicon single crystal substrate is 2 O 3 A single crystal film and the γ-Al 2 O 3 A perovskite-structured pseudocubic metal oxide layer, LaNiO3 or SrRuO, formed on a single crystal film. 3 and a Pb(Zr,Ti)O thin film formed on the oxide thin film. 3 and an oriented ferroelectric thin film consisting of the ferroelectric thin film, the oxide electrode thin film, and the γ-Al 2 O 3 The present invention is constituted by a laminated structure on a semiconductor substrate, characterized in that the orientation of the single crystal film and the orientation of the silicon single crystal substrate are both (001) orientation.

[0011] According to this configuration, γ-Al epitaxially grown on a silicon single crystal substrate 2 O 3 Since the oxide thin film is formed on the single crystal film, the crystallinity of the oxide thin film can be improved. 2 O 3 To form a thin oxide electrode film on the single crystal film, γ-Al 2 O 3It is possible to improve the adhesion between the single crystal film and the oxide electrode thin film. Note that the pseudocubic crystal is disclosed as a crystal structure having two cubic crystals stacked inside an orthorhombic crystal.

[0012] A buffer layer is formed on the silicon substrate to ensure electrical insulation. 2 O 3 A single crystal film is used, which enables epitaxial growth from a silicon single crystal substrate, and the electrode layer can be oriented in (001) and the piezoelectric film can also be oriented in (001), aiming to obtain a film with excellent properties.

[0013] However, the Al buffer layer 2 O 3 Since SiO has a high Young's modulus, when using a MEMS actuator, if the piezoelectric film does not have high properties, a large amplitude cannot be obtained. 2 The Young's modulus of Al is 76.5 GPa. 2 O 3 The Young's modulus of sapphire is 430-470 GPa. It is about six times the Young's modulus at maximum, and is very hard. If it is used in a moving part, this film will limit the speed and hinder the movement.

[0014] Al 2 O 3 The other material commonly used as a seed layer is PbTiO 3 This PbTiO 3 However, since it is an environmentally unfriendly material containing Pb, it is not preferable.

[0015] Other materials known to be used as seed layers include LaNiO 3 There is LaNiO 3 However, there is a problem with durability at high temperatures. In particular, when forming piezoelectric films such as KNN, the temperature becomes higher than that of PZT, so LaNiO 3 is difficult to use.

[0016] For these reasons, SrRuO3 However, the piezoelectric element structure of commonly used MEMS devices uses SrRuO 3 In addition, the piezoelectric film grows in the (111) direction, which reduces the piezoelectric constant (e31). 3 It was not possible to grow a piezoelectric film in the (001) orientation, which has a high piezoelectric constant, on the substrate.

[0017] In addition, ZrO was used as a buffer layer on the silicon single crystal substrate. 2 It is possible to grow a seed layer in the (001) orientation by forming a silicon substrate such as silicon carbide or sapphire and growing it epitaxially, but this has problems such as the layer not functioning adequately as an insulating layer and the high Young's modulus that could affect MEMS operation.

[0018] <First embodiment> FIG. 1 shows the SrRuO 3 1 is a schematic cross-sectional view of a (001) seed layer formed in the first embodiment, and includes a silicon substrate 1, a buffer layer 2, an adhesion layer 3, a lower electrode 4, and a seed layer 5.

[0019] In this embodiment, a silicon single crystal substrate 1 is provided with a buffer layer 2 made of SiO 2 Forming SiO 2 A (111) oriented electrode material such as Pt or Ir is deposited on the substrate, and the electrode and SiO 2 Between them, TiO is placed to ensure adhesion. 2 The adhesive layer 3 is made of SrRuO with a (001) orientation, which is formed by a unique film formation method on the electrode with a (111) orientation. 3 The unique (001) oriented SrRuO 3 The growth method will be described later.

[0020] SiO as buffer layer 2 on silicon single crystal substrate 2This ensures electrical insulation between the electrode and the silicon single crystal substrate, reducing leakage current. This leads to improved reliability. In addition, its Young's modulus is smaller than other insulating films, ensuring the amount of deformation of the MEMS device. Each film is described in detail below.

[0021] The substrate 1 is a single crystal substrate made of Si (100). Si substrates are compatible with MEMS devices in terms of workability, strength, and cost efficiency. Silicon single crystal substrates with orientations other than the (100) orientation may also be used. In addition, SOI (Silicon on Insulator), Al 2 O 3 , MgO, SrTiO 3 A substrate such as the above may also be used.

[0022] Buffer layer 2 is SiO 2 The insulating layer ensures electrical insulation between the substrate 1 and the lower electrode 4, and also serves as a sacrificial layer during MEMS processing. 2 The thickness is preferably about 100 to 300 nm.

[0023] The buffer layer on the silicon single crystal substrate is SiO 2 This makes it possible to improve the reliability of the piezoelectric driven MEMS device and ensure the amount of deformation.

[0024] The lower electrode 4 is made of (111) oriented Pt. Pt has good heat resistance, workability, and lattice matching with the seed layer 5, and is naturally oriented in the (111) direction. In order to increase the orientation rate and crystallinity of the seed layer 5, Pt was used that was 100% oriented in (111) in X-ray diffraction measurement and had a rocking curve peak half-width of 6° or less. In X-ray diffraction measurement, the narrower the half-width of the rocking curve, the better the crystallinity, which is one of the indicators of crystallinity. The method for forming this distinctive Pt (111) film will be described later.

[0025] In this embodiment, in order to enhance the crystallinity of Pt oriented in (111), many parameters were evaluated, and as described later, a method of narrowing the full width at half maximum of the rocking curve was found. With this highly crystalline Pt, the desired seed layer 5 can be obtained.

[0026] In this embodiment, Pt is formed by RF sputtering, but other physical film formation methods or chemical film formation methods such as evaporation may also be used. Also, the material of the lower electrode 4 may be a metal electrode such as Ir, Au, Al, or Cu. In order to enhance the adhesion between the buffer layer 2 and the lower electrode 4, TiO of the adhesion layer 3 2 is inserted, but there is also a configuration where it is not inserted.

[0027] The material of the seed layer 5 is SrRuO 3 It is characterized in that the (001) orientation ratio, which is calculated by taking the sum of the diffraction intensities of each crystal orientation obtained by X-ray diffraction measurement as the denominator and the (001) intensity as the numerator, is 95% - 100% SrRuO 3 The seed layer 5 is a layer that controls the crystal orientation and crystallinity of the piezoelectric film formed directly above it. SrRuO 3 is suitable because of its high thermal and chemical stability and environmental compatibility. With SrRuO 3 having an orientation ratio of 95% - 100%, it becomes possible to increase the piezoelectric constant of the piezoelectric film formed on the seed layer.

[0028] In this embodiment, SrRuO 3 is formed by RF sputtering, but it may also be formed by other physical methods such as pulsed laser deposition (PLD), or by chemical methods such as evaporation, CVD, solution method, sol - gel method, etc.

[0029] <Regarding the relationship between Pt and SRO>

[0030] Regarding the relationship between the Pt crystallinity, which is a feature of the present invention, and the SrRuO 3 crystallinity. It is known that the crystallinity of Pt changes depending on the film formation conditions. The film formation conditions include film formation temperature, RF power, film formation time, gas species (Ar, O 2The deposition conditions were changed to create many samples with different Pt crystallinity. The crystallinity was evaluated using X-ray diffraction patterns and compared using the half-width of the peaks.

[0031] We experimented with a wide variety of the conditions shown above to optimize the half-width of the Pt(111) peak value. Using techniques such as machine learning, we tried to optimize the countless conditions to efficiently reduce the half-width of the peak.

[0032] The X-ray diffraction pattern was measured with a resolution of 0.1°, and each peak was fitted with a Gaussian function to calculate the half-width. However, when the tail was short and the half-width was narrower than 1°, the half-width was calculated by fitting to a Lorentzian function. This allows the half-width to be calculated with high accuracy without reducing the resolution.

[0033] The X-ray diffraction pattern of this embodiment is shown in FIG. 2. The X-ray diffraction pattern (tilt 0 degree, tilt 35 degree) is an example of this embodiment. The reason for including the 35 degree tilt pattern will be described later. From the X-ray diffraction pattern at the 0 degree tilt, Pt(111) and SrRuO 3 The (001) peak can be seen. The half-width was read from this peak.

[0034] The deposition conditions for the sample shown in Figure 2 are as follows: deposition temperature: 600°C, RF power: 400W, deposition time: 5 minutes, gas type: Ar, sputtering pressure: 0.8Pa.

[0035] We created many examples of the structure shown in Figure 2 and investigated them from various viewpoints. Among them, the half-width of the rocking curve of Pt(111) and SrRuO 3 The correlation of the half-width of the (001) rocking curve is shown below.

[0036] In order to find the correlation coefficient, 19 conditions were tested as a sufficient number of samples. Figure 3 shows the half-width of the rocking curve of Pt(111) and SrRuO 3This is a plot of the half-width of the rocking curve for (001). In addition, the correlation coefficient was calculated for these 19 condition points. The correlation coefficient was the commonly used Pearson product-moment correlation coefficient. The square of the correlation coefficient R was 0.8315, indicating a strong correlation.

[0037] In particular, in this experiment, out of the 19 conditions in the population, 18 conditions had a half-width of 2° or less for the (111)-oriented Pt rocking curve. It was not known that such a high correlation exists among highly crystalline samples with rocking curves of 2° or less. This means that if highly crystalline (111)-oriented Pt can be realized, it will be possible to obtain highly crystalline SrRuO 3 The fact is that (001) can be realized.

[0038] Crystallinity of Pt and SrRuO 3 There is a strong correlation between the crystallinity of SrRuO 3 It was found that the crystallinity of SrRuO can be controlled by the Pt film formation conditions. 3 In order to increase the crystallinity of the Pt, it is necessary to increase the crystallinity of the Pt.

[0039] Next, SrRuO 3 The orientation rate was evaluated by X-ray diffraction pattern and can be calculated from the peak height. 3 The orientation ratio was derived by comparing the heights of peaks such as (001), (111), and (110) due to the above.

[0040] The SrRuO 3 In the X-ray diffraction pattern (tilt angle 0 degrees), SrRuO 3 Since the (111) peak overlaps with the Pt(111) peak, SrRuO 3 (111) cannot be evaluated. Therefore, SrRuO 3When the (111) orientation is present, (110) appears at a position tilted by 35°. Taking advantage of this, the (110) intensity when measuring with the wafer tilted at 35° is calculated as the (111) orientation intensity. As shown in Figure 2, a high intensity (001) peak appears, and (110) is barely detected. The (110) peak intensity at a 35° tilt is also very small, indicating that there is little (111) orientation. The diffraction intensity of (001) is 13 cps, and the diffraction intensity of (110) derived from (111) is 0.4 cps, so the (001) orientation rate is approximately 97%, and SrRuO 3 It can be seen that the preferred orientation is (001).

[0041] Using the method for calculating the orientation ratio shown above, the crystallinity of Pt and SrRuO 3 We investigated the relationship between the (001) orientation rate of SrRuO and the half-width of the rocking curve of Pt oriented in (111). 3 The (001) orientation rate of the samples was plotted. The samples were made under 20 conditions, including the 19 conditions shown above, which were obtained by changing the Pt film formation conditions, and one additional condition.

[0042] As can be seen from Figure 4, when the half-width of Pt is 5° or less, there are several outliers, but 17 out of 19 points have an orientation rate of 90% or more. In other words, it can be said that a sufficient orientation rate can be achieved if it is 5° or less.

[0043] This is due to the fact that the half-width of the rocking curve for Pt(111) and SrRuO 3 This is related to the correlation coefficient of the half-width of the rocking curve of (001). By increasing the crystallinity of Pt(111), 3 The crystallinity of (001) is also improved, and the orientation rate of (001) is also significantly improved. From this figure, it can be seen that the half-width of the rocking curve of Pt(111) is 5°, which is the threshold value for improving the orientation rate.

[0044] As a comparative example, when the half-width of the rocking curve of Pt(111) added as an additional condition exceeds 7°, SrRuO 3The (001) orientation rate is significantly reduced. The orientation rate is reduced to 40%. With such an orientation rate, it is not possible to form a piezoelectric film having a sufficient piezoelectric effect. This will be described later.

[0045] What is clear from this experiment is that it is necessary to prevent the half-width of the rocking curve of Pt(111) from exceeding 7°. Since 1° is necessary as a manufacturing tolerance to control the rocking curve of Pt(111), 6°, which is midway between 5° and 7°, can be defined as the threshold. In other words, it is possible to obtain the desired piezoelectric film by making Pt(111) 6° or less.

[0046] In addition, if the crystallinity of Pt(111) can be controlled, SrRuO 3 As mentioned above, the crystallinity of the (001) can also be controlled. 3 From the correlation of the half-width of the rocking curve of (001), if the rocking curve of Pt(111) is 6°, then SrRuO 3 The half-width of the rocking curve of (001) is also 6°. Since the square of this correlation coefficient is 0.8315, there is a certain tolerance, and it is necessary to allow about 1°. To obtain the desired piezoelectric constant, SrRuO 3 It is also desirable that the half-width of the (001) rocking curve is 6° or less.

[0047] In addition, SrRuO 3 In order to reduce the half-width of the (001) rocking curve, it is necessary to reduce the half-width of the Pt(111) rocking curve. In particular, when the half-width of the Pt(111) rocking curve shown in FIG. 3 is 2° or less, the SrRuO 3 The half-width of the rocking curve of (001) is less than 2°. SrRuO 3 By making the rocking curve of (001) 2° or less, the half-width of the rocking curve of the piezoelectric film formed on it also becomes small. It was found that if the angle is 2° or less, including manufacturing tolerances, the defect density of the piezoelectric film also decreases and the leakage current becomes sufficiently small.

[0048] From the above-mentioned electrical characteristics, it is desirable to set the half-width of the rocking curve of Pt(111) to 2° or less. 3 It is desirable for the half-width of the (001) rocking curve to be 2° or less, which allows the formation of a piezoelectric film with little leakage current.

[0049] Next, SrRuO 3 The film formation temperature was investigated. Figure 5 shows the X-ray diffraction pattern of the comparative example. Figure 5 shows the SrRuO film formed at 385°C. 3 The X-ray diffraction pattern of the film is shown in Fig. 5. The base metal used for this film formation is the Pt(111) film, which has a half-width of the rocking curve of 2° or less as shown above. It can be seen from Fig. 5 that there are no peaks other than Pt(111). In the film formation at 385°C, SrRuO 3 (001) and (110) of SrRuO are not detected at 35° tilt. 3 Since only the (110) intensity derived from the (111) of SrRuO 3 It can be seen that the crystal is 100% oriented in the (110) direction.

[0050] In the above comparative example, the half-width of the rocking curve of the Pt(111) of the underlying metal film is 2° or less. In other words, even if the crystallinity of the underlying metal film is good, the SrRuO 3 Depending on the deposition temperature, SrRuO 3 It was found that the (111) orientation of the SiO2 was predominant.

[0051] To confirm this, SrRuO 3 The film formation temperature was changed to investigate the effect of the film formation temperature on the orientation rate.

[0052] Figure 6 shows SrRuO 3 and SrRuO 3The figure shows the relationship between the (001) orientation rate and the temperature. When the film formation temperature is below 450°C, (001) does not appear, but gradually appears when the film is formed at 450°C or higher, and the (001) orientation rate increases with increasing temperature. It was found that when the film formation temperature exceeds 600°C, the (001) orientation rate is nearly 100%. For this reason, a film formation temperature of 600°C or higher is preferable.

[0053] The mechanism of the formation of the above will be considered. The high film formation temperature provides the molecules with sufficient thermal energy, which causes them to repeatedly diffuse and re-evaporate on the substrate, approaching a thermodynamic equilibrium state. In this embodiment, the stable plane is considered to be the (00n) plane, and it can be inferred that the higher the temperature, the more the (00n) plane becomes preferential.

[0054] SrRuO 3 By setting the film formation temperature at 600°C or higher, a film oriented in (001) can be obtained. The (001) orientation rate is 95% or higher. This makes it possible to increase the piezoelectric constant of the piezoelectric film formed thereon.

[0055] The semiconductor substrate according to this embodiment includes a silicon single crystal substrate 1, a metal film 4 formed on the silicon single crystal substrate and oriented in (111), and a pseudo-cubic metal oxide layer SrRuO 3 and an oxide electrode thin film 5 having the SrRuO 3 The film is characterized by its (001) orientation, which can increase the piezoelectric constant of the piezoelectric film formed on the substrate.

[0056] The semiconductor substrate according to this embodiment is characterized in that the metal film 4 is made of Pt. This allows a high-quality metal oxide layer SrRuO 3 The membrane 5 can be produced using conventional manufacturing processes.

[0057] The semiconductor substrate according to this embodiment has a SiO 2This allows the SiO layer 2, which has a lower Young's modulus than other materials, to be used in the portion where the substrate is curved, such as the drive portion of the MEMS mirror. 2 This makes it possible to employ the above, thereby expanding the driving range of the driving unit.

[0058] The semiconductor substrate according to this embodiment is the SrRuO 3 The substrate is characterized by having a (001) orientation rate of 95% or more. This improves the orientation rate of the piezoelectric film formed on the substrate, and increases the piezoelectric constant.

[0059] The semiconductor substrate according to this embodiment is the SrRuO 3 The substrate is characterized in that the half-width of the (001) rocking curve is 6° or less. This improves the orientation rate of the piezoelectric film formed on the substrate, thereby increasing the piezoelectric constant.

[0060] The semiconductor substrate according to this embodiment is the SrRuO 3 The substrate is characterized in that the half-width of the (001) rocking curve is 2° or less. This improves the orientation rate of the piezoelectric film formed on the substrate, thereby increasing the piezoelectric constant.

[0061] The semiconductor substrate according to this embodiment is characterized in that the half-width of the rocking curve of the metal film is 6° or less, which improves the orientation rate of the piezoelectric film formed on the substrate and increases the piezoelectric constant.

[0062] The semiconductor substrate according to this embodiment is characterized in that the half-width of the rocking curve of the metal film is 2° or less, which improves the orientation rate of the piezoelectric film formed on the substrate and increases the piezoelectric constant.

[0063] The method for producing a semiconductor substrate according to the present embodiment is to form a film at a temperature of 600° C. or higher using SrRuO 3 This improves the orientation rate of the piezoelectric film formed on the substrate, thereby increasing the piezoelectric constant.

[0064] <Second embodiment> FIG. 7 shows the SrRuO 3 A schematic cross-sectional view of a piezoelectric thin film formed on a (001) thin film seed layer structure. An adhesive layer is inserted, and SrRuO 3 On top of the thin film seed layer structure, PbZrTiO 3 The piezoelectric thin film is formed.

[0065] Similarly, this embodiment also comprises a substrate 1 , a buffer layer 2 , a first adhesive layer 3 , a lower electrode 4 , a seed layer 5 , a piezoelectric film 6 , a second adhesive layer 7 , and an upper electrode 8 .

[0066] In this embodiment, the first adhesive layer 3 and the second adhesive layer 7 are made of TiO 2 is deposited by RF sputtering, but other metal oxides or metal nitrides such as Nb, Ta, Zn, and Ru may also be used.

[0067] In this embodiment, the piezoelectric film 6 is made of PbZrTiO 3 We selected PbZrTiO 3 In this embodiment, the piezoelectric film is formed by RF sputtering, but it may be formed by PLD, sol-gel, or CVD. Since the seed layer is formed in the (001) orientation, the above growth method can grow PbZrTiO 3 can be formed.

[0068] SrRuO 3 Using the thin film seed structure, a PZT film was formed directly on top of the thin film seed structure and evaluated using an X-ray diffraction pattern. Only the (001) diffraction peak of PZT appeared, with almost no (110) or (111) peaks, indicating that the PZT film had a (001) preferred orientation.

[0069] By growing the piezoelectric film 6 with good crystallinity in the (001) orientation, the piezoelectric constant e31 can be increased, and the performance of MEMS actuator devices such as MEMS mirrors and IJ heads can be improved. For this reason, the piezoelectric film 6 must be aligned in the (001) orientation. Since the seed layer 5 is formed as a high-quality film with a (001) orientation, the piezoelectric film 6 on top of it is also influenced by this, and high-quality crystals can be grown in the (001) orientation.

[0070] Figure 8 shows SrRuO 3 The horizontal axis indicates the orientation rate, and the vertical axis indicates the piezoelectric constant e31 of the piezoelectric film 6. The unit of the piezoelectric constant is [m / V]. The orientation rate indicates the ratio of the area oriented in (100) to the area oriented in (111). The oriented area is estimated from the cross-sectional area of ​​the peak in the X-ray diffraction pattern. What can be seen from this figure is that the piezoelectric constant e31 exceeds 10 [m / V] for the first time when the orientation rate exceeds 90%. As will be described later, the MEMS In the case of the actuator, it cannot be used unless it exceeds 10. 3 The orientation rate of the fluororesin must exceed 90. Taking into account manufacturing tolerances, an orientation rate of 95% or more is preferably required.

[0071] The upper electrode 8 is preferably made of a metal electrode material with excellent heat resistance and workability, such as Pt or Ir. Au, Ni, Cu, etc. may also be used, and the material is not particularly limited. A second adhesive layer 7 is inserted between the piezoelectric film 6 and the upper electrode 8 to ensure adhesion and compensate for oxygen defects in the piezoelectric film.

[0072] Seed layer: SrRuO 3 By preferentially orienting SrRuO in the (001) direction, the piezoelectric film formed directly above it can be aligned to the (001) direction, improving the properties. 3 By using SrRuO, it is possible to improve heat resistance and enable high temperature deposition of piezoelectric films. 3 Since no lead is used, the environmental impact can be reduced when depositing a lead-free piezoelectric material.

[0073] (001) oriented SrRuO as a seed layer 3 By forming SrRuO, the piezoelectric film is preferentially oriented in the (001) direction. It is known that the piezoelectric constant is high in the (001) direction, which improves the actuator characteristics. 3 It has high thermal stability. Since it is a material that does not use Pb, it can reduce the environmental impact.

[0074] Generally, SrRuO 3 When a film is formed on the piezoelectric film, it will have a (111) orientation as shown in Figure 3, and the piezoelectric film formed directly above it will also have a (111) orientation. As a result, it is not possible to improve the characteristics as a MEMS actuator, but in this embodiment, a (001) orientation is achieved, and the piezoelectric film can be grown with a (001) orientation. This improves the piezoelectric constant e31, and improves the MEMS actuator characteristics.

[0075] <Third embodiment> FIG. 9 shows the SrRuO 3 A schematic cross-sectional view of a piezoelectric thin film formed on a (001) thin film seed layer structure. 3 On top of the thin film seed layer structure, potassium sodium niobate (KNaNbO 3 :KNN) It ​​has a form in which a piezoelectric thin film is formed.

[0076] Like the first embodiment, this embodiment comprises a substrate 1, a buffer layer 2, a first adhesive layer 3, a lower electrode 4, a seed layer 5, a piezoelectric film 9, a second adhesive layer 7, and an upper electrode 8.

[0077] In this embodiment, the piezoelectric film 9 is made of KNaNbO 3 (KNN) was used. It is preferable that the piezoelectric film is preferentially oriented in the (001) direction. In this embodiment, the piezoelectric film is formed by RF sputtering, but it may be formed by PLD, sol-gel, or CVD.

[0078] SrRuO 3Using the thin film seed structure, the KNN film formed directly on it was evaluated by X-ray diffraction pattern. Only the (001) diffraction peak of KNN appeared, and the (110) and (111) peaks were hardly seen, so the KNN film was formed with (001) preferred orientation. In addition, the material of the piezoelectric film was BiFeO 3 etc. are also acceptable.

[0079] <Fourth embodiment> Next, a device to which the above-mentioned piezoelectric film is applied will be described. [Configuration of movable device]

[0080] Fig. 10 is a plan view showing an example of the configuration of the movable device on which the present invention is based. As shown in Fig. 10, the movable device 13 includes a mirror section 101 that reflects incident light, a first driving member 110a and a second driving member 110b that are connected to the mirror section and drive the mirror section around a first axis parallel to the Y axis, a first support section 120 that supports the mirror section and the first driving member 110a, a third driving section 130a and a fourth driving section 130b that are connected to the first support section and drive the mirror section and the first support section around a second axis parallel to the X axis, a second support section 140 that supports the third and fourth driving sections, and an electrode connection section 150 that is electrically connected to the first to fourth driving sections and a control device.

[0081] The movable device 13 is formed, for example, by forming a single SOI (Silicon On Insulator) substrate by etching or the like, and forming the reflecting surface 14, the first and second driving units 112a, 112b, the third driving units 131a-131f, the fourth driving units 132a-132f, the electrode connection unit 150, etc., on the formed substrate, so that each component is integrally formed. Note that the formation of each of the above components may be performed after or during the formation of the SOI substrate.

[0082] Figure 11 is a cross-sectional view of the movable device shown in Figure 10. The SOI substrate is a substrate in which a silicon oxide layer 162 is provided on a first silicon support layer 161 made of single crystal silicon (Si), and a second silicon layer made of single crystal silicon is further provided on the silicon oxide layer. Hereinafter, the first silicon layer is referred to as the silicon support layer 161, and the second silicon layer is referred to as the silicon active layer 163.

[0083] Since the silicon active layer 163 has a smaller thickness in the Z-axis direction than in the X-axis direction or the Y-axis direction, the drive section formed only of the silicon active layer 163 functions as an elastic section having elasticity.

[0084] The SOI substrate does not necessarily have to be flat, and may have a curvature, etc. Also, the driving part used to form the movable device 13 is not limited to the SOI substrate, so long as it can be integrally molded by etching or the like and can be partially made elastic.

[0085] The mirror section 101 is composed of, for example, a circular mirror base 102 and a reflecting surface 14 formed on the +Z side surface of the mirror base. The mirror base 102 is composed of, for example, a silicon active layer 163. The reflecting surface 14 is composed of, for example, a metal thin film containing aluminum, gold, silver, etc. The mirror section 101 may also have a rib formed on the -Z side surface of the mirror base 102 for reinforcing the mirror section. The rib is composed of, for example, a silicon support layer 161 and a silicon oxide layer 162, and can suppress distortion of the reflecting surface 14 caused by movement.

[0086] The first driving member 110a and the second driving member 110b have one end connected to the mirror base 102 and the other end connected to the support section 120. The first driving member 110a is composed of a torsion bar 111a, a first driving section 112a, and a support for the first driving section. Two torsion bars 111a and 111b that movably support the mirror section 101 extend in the first axial direction and are connected to the support for the first driving section 112a and the support for the second driving section 112b, and the support for the driving sections is connected to the support section 120.

[0087] As shown in FIG. 11, the torsion bars 111a and 111b are made of a silicon active layer 163. The first driving section 112a and the second driving section 112b are made by forming a lower electrode 201, a piezoelectric section 202, and an upper electrode 203 in this order on the +Z side surface of the silicon active layer 163, which is the elastic section. The upper electrode 203 and the lower electrode 201 are made of, for example, gold (Au) or platinum (Pt). The piezoelectric section 202 is made of, for example, a piezoelectric material such as PZT (lead zirconate titanate), potassium sodium niobate (KNaNbO 3 :KNN).

[0088] Returning to FIG. 10, the first support section 120 is a rectangular support body formed to surround the mirror section 101 and includes, for example, a silicon support layer 161, a silicon oxide layer 162, and a silicon active layer 163.

[0089] The third driving section 130a and the fourth driving section 130b are composed of a plurality of third driving sections 131a to 131f and fourth driving sections 132a to 132f, which are connected to each other in a folded manner, and one end of the third driving section 130a and the fourth driving section 130b is connected to the outer periphery of the first support section 120, and the other end is connected to the inner periphery of the second support section 140. At this time, the connection point between the support of the third driving section 130a and the first support section 120 and the connection point between the support of the fourth driving section 130b and the first support section 120, as well as the connection point between the support of the third driving section 130a and the second support section 140 and the connection point between the support of the fourth driving section 130b and the second support section 140 are point symmetrical with respect to the center of the reflecting surface 14.

[0090] In a meander structure in which multiple beams are connected in a folded manner, piezoelectric actuator group A 113a and piezoelectric actuator group B 113b are alternately provided on the +Z side surface of each beam. By driving only piezoelectric actuator group A 113a or only piezoelectric actuator group B 113b, it is possible to control the deflection angle of the mirror to the + side or - side without using a negative voltage. In addition, when applying voltages of opposite phase to piezoelectric actuator group A 113a and piezoelectric actuator group B 113b and switching the voltage or time domain of the applied signal, it is also possible to apply a time difference to the signal switching between piezoelectric actuator group A 113a and piezoelectric actuator group B 113b, so that the generated mechanical vibrations are in opposite phase between piezoelectric actuator group A 113a and piezoelectric actuator group B 113b and are cancelled out. This enables high-speed drawing and response to complex drive waveforms.

[0091] 11, the third driving section 130a and the fourth driving section 130b are configured by forming a lower electrode 201, a piezoelectric section 202, and an upper electrode 203 in this order on the +Z side surface of the silicon active layer 163, which is the elastic section. The upper electrode 203 and the lower electrode 201 are made of, for example, gold (Au) or platinum (Pt). The piezoelectric section 202 is made of PZT (lead zirconate titanate) or SrRuO3.

[0092] Returning to FIG. 10, the second support section 140 is a rectangular support member composed of, for example, a silicon support layer 161, a silicon oxide layer 162, and a silicon active layer 163, and is formed so as to surround the mirror section 101, the first driving member 110a, the second driving member 110b, the first support section 120, the third driving section 130a, and the fourth driving section 130b.

[0093] The electrode connection part 150 is formed, for example, on the surface on the +Z side of the second support part 140, and is electrically connected to the upper electrodes 203 and lower electrodes 201 of the first drive part 112a, the second drive part 112b, the third drive parts 131a-131f, and the fourth drive parts 132a-132f, and the control device 11 via electrode wiring such as aluminum (Al). Note that the upper electrodes 203 and the lower electrodes 201 may each be directly connected to the electrode connection part, or may be indirectly connected by connecting the electrodes to each other, for example.

[0094] In this embodiment, an example has been described in which the piezoelectric portion 202 is formed only on one surface (the +Z side surface) of the silicon active layer 163, which is the elastic portion. However, the piezoelectric portion 202 may be provided on another surface (for example, the -Z side surface) of the elastic portion, or may be provided on both one surface and the other surface of the elastic portion.

[0095] In addition, as long as the mirror unit can be driven around the first axis or the second axis, the shape of each component is not limited to the shape of the embodiment. For example, the torsion bars 111a and 111b, the first driving unit 112a, and the second driving unit 112b may have a shape with a curvature.

[0096] Furthermore, an insulating layer made of a silicon oxide film may be formed on at least one of the +Z side surface of the upper electrode 203 of the first driving member 110a and the second driving member 110b, the +Z side surface of the first support part, the +Z side surface of the upper electrode 203 of the third driving part 130a and the fourth driving part 130b, and the +Z side surface of the second support part. In this case, the electrode wiring is provided on the insulating layer, and the insulating layer is partially removed or not formed as an opening only at the connection spot where the upper electrode 203 or the lower electrode 201 is connected to the electrode wiring, thereby increasing the design freedom of the first driving member 110a, the second driving member 110b, the third driving part 130a, the fourth driving part 130b, and the electrode wiring, and further suppressing short circuits due to contact between the electrodes. The silicon oxide film also functions as an anti-reflection material.

[0097] [Controller control details] Next, details of the control by the control device that drives the first to fourth drive units of the movable device will be described.

[0098] When a positive or negative voltage is applied in the polarization direction, the piezoelectric section 202 provided in the first driving member 110a, the second driving member 110b, the third driving section 130a, and the fourth driving section 130b undergoes deformation (e.g., expansion and contraction) proportional to the potential of the applied voltage, thereby exerting the so-called inverse piezoelectric effect. The first driving member 110a, the second driving member 110b, the third driving section 130a, and the fourth driving section 130b move the mirror section 101 by utilizing the inverse piezoelectric effect.

[0099] In this case, the angle formed by the XY plane and the reflecting surface 14 when the reflecting surface 14 of the mirror section 101 is tilted in the +Z direction or the -Z direction with respect to the XY plane is called the deflection angle. In this case, the +Z direction is the positive deflection angle, and the -Z direction is the negative deflection angle.

[0100] First, the control of the control device that drives the first driving unit will be described. In the first driving member 110a and the second driving member 110b, when a driving voltage is applied in parallel to the piezoelectric unit 202 of the first driving unit 112a and the second driving unit 112b via the upper electrode 203 and the lower electrode 201, each piezoelectric unit 202 is deformed. Due to the effect of the deformation of the piezoelectric unit 202, the first driving unit 112a and the second driving unit 112b are bent and deformed. As a result, a driving force about the first axis acts on the mirror unit 101 via the twist of the two torsion bars (connecting units) 111a and 111b, and the mirror unit 101 moves about the first axis. The driving voltage applied to the first driving member 110a and the second driving member 110b is controlled by the control device 11.

[0101] Therefore, the control device 11 applies a driving voltage having a predetermined sinusoidal waveform in parallel to the first driving section 112a and the second driving section 112b of the first driving member 110a and the second driving member 110b, so that the mirror section 101 can be moved around the first axis at a period of the driving voltage having a predetermined sinusoidal waveform.

[0102] In particular, for example, when the frequency of the sinusoidal waveform voltage is set to approximately 20 kHz, which is similar to the resonant frequency of the torsion bars 111a and 111b, the mirror portion 101 can be made to resonate and vibrate at approximately 20 kHz by utilizing the mechanical resonance caused by the twisting of the torsion bars 111a and 111b.

[0103] The actuator for driving the mirror according to this embodiment is characterized by using the semiconductor substrate described in the second and third embodiments. This allows the use of a substrate with a large piezoelectric constant and a small Young's modulus, realizing a large driving range. In addition, materials with no environmental impact are used.

[0104] <Fifth embodiment> An overview of this embodiment is shown in Figures 12 and 13. Figure 12 is a plan view. Figure 13 shows a cross section of the piezoelectric film 318 in the longitudinal direction along the line AA' in Figure 1.

[0105] A nozzle plate 336 is bonded to the underside of an individual liquid chamber substrate 310 having a vibration plate 338, a piezoelectric film 318, and a metal layer laminated on the upper part (upper electrode 316), and a holding substrate 344 and a common liquid chamber substrate (not shown) are laminated on the upper part of the individual liquid chamber substrate 310 to form an ink flow path, thereby forming an inkjet head.

[0106] Ink is supplied to the ink supply port 326, fluid resistance portion, and individual liquid chamber 342 that open into the individual liquid chamber substrate 310 via a common liquid chamber (common liquid chamber substrate and holding substrate 344) that communicates with an ink tank not shown, and ink is ejected from a nozzle 334 that communicates with the individual liquid chamber 342 by the pressure generated by driving a piezoelectric element 319 (composed of a piezoelectric film 318, an upper electrode 316, and a lower electrode 314) formed on a vibration plate 338 of the individual liquid chamber 342.

[0107] The piezoelectric element 319 is driven by a voltage applied to the upper electrode 316 and the lower electrode 314. The upper electrode 316 is connected to a driving IC 332 and an FPC (Flexible Printed Circuit) using an individual wiring 328, and the lower electrode 314 is connected to the FPC using a common wiring 330.

[0108] (Nozzle plate 336) The nozzle plate 336 is a substrate on which the nozzles 334 for ejecting ink are arranged, and any material can be used depending on the required rigidity and processability. Examples include metals or alloys such as SUS and nickel, inorganic materials such as silicon and ceramics, and resin materials such as polyimide. The nozzle processing method can be selected based on the characteristics of the material and the required precision and processability, and examples include electroforming plating, etching, pressing, laser processing, photolithography, etc. The nozzle opening diameter, number of arrangements, and arrangement density can be set to the optimal combination according to the specifications required for the ink head.

[0109] (Individual liquid chamber substrate 310) An individual liquid chamber 342, a fluid resistance portion, and an ink supply port 326 are formed in the individual liquid chamber substrate 310. Any substrate material can be used in consideration of processability and physical properties, but a silicon substrate that can be used with photolithography is used for 300 dpi (approximately 85 μm pitch) or more. Any substrate material can be used to process the liquid chamber, but when using the above-mentioned photolithography method, either wet etching or dry etching can be used. In either method, the liquid chamber side of the vibration plate can be made into a silicon dioxide film or the like to serve as an etch stop layer, so that the liquid chamber height can be controlled with high precision.

[0110] The individual liquid chamber 342 has a function of applying pressure to the ink, causing droplets to be ejected from the nozzle 334. A vibration plate 338 is formed above the individual liquid chamber 342, and a piezoelectric element 319 is formed on the vibration plate 338, in which a lower electrode 314, a piezoelectric film 318, and an upper electrode 316 are laminated. Any material can be used for the vibration plate 338, but it is preferable to use a highly rigid material such as silicon, nitride, oxide, or carbide. It may also be a laminate structure of these materials. When using a laminate film, it is preferable to use a structure with little residual stress, taking into account the internal stress of each material. For example, Si 3 N 4 and SiO 2 In the case of the laminate, the Si 3 N 4 and SiO 2 For example, a structure in which these are alternately laminated to relieve stress can be given.

[0111] The thickness of the vibration plate 338 can be selected according to the desired characteristics, but is preferably in the range of about 0.5 μm to 10 μm, and more preferably in the range of 1.0 to 5.0 μm. If the vibration plate 338 is too thin, it is easily damaged by cracks, etc., and if it is too thick, the amount of displacement is small and the ejection efficiency is reduced. In addition, if it is too thin, the natural frequency of the vibration plate 338 is reduced, and there is a problem that the driving frequency cannot be increased.

[0112] The lower electrode 314 and the upper electrode 316 can be made of any conductive material. Examples include metal, alloy, and oxide electrode films. These materials may be single-layered or multi-layered. If necessary, an adhesive layer may be formed in consideration of adhesion to the diaphragm 338. Examples of electrode materials that are highly stable include Pt, Ir, Ir oxide, and Ru. As an oxide electrode film, SrRuO 3 , LaNiO 3 , IrO 2 , RuO 2, SrO, etc. are used. The adhesion layer with the diaphragm 338 is made of a titanium layer, a titanium oxide layer, a titanium tungsten layer, an alumina layer, a zirconium oxide layer, etc. The adhesion layer is generally thin, about several tens of nm, and has a small contribution to rigidity. As will be described later, when an electrode material is used as the resistance temperature sensor or heating means, Pt is preferable. A laminated film containing Pt may also be used.

[0113] The present embodiment is characterized by a piezoelectric film that heats the ink, reduces the viscosity of the ink, improves the ink ejection performance, and does not lose its piezoelectric properties even at high temperatures.

[0114] The piezoelectric material of the piezoelectric film 318 is potassium sodium niobate ((K,Na)NbO 3 KNN (hereinafter also referred to as KNN) is adopted. KNN has a relatively high Curie temperature, and good piezoelectric characteristics are obtained among lead-free piezoelectric materials. KNN is a piezoelectric material with a high Curie temperature, good temperature stability, and a wide operating range for temperature. In general, KNN has a higher Curie temperature than PZT. Therefore, by using KNN, the temperature stability of the piezoelectric characteristics can be improved compared to PZT, and the temperature operating range as an inkjet can be widened. Therefore, the ink can be heated to a higher temperature to reduce the viscosity, so a higher viscosity can be used. Any method can be used as a method for forming the KNN thin film, and various film formation methods such as sputtering, PLD, CVD, and chemical solution deposition (CSD) can be appropriately selected. The upper electrode 316 and the piezoelectric film 318 need to be patterned for each individual liquid chamber 342. For patterning, a normal photolithography method can be used.

[0115] The piezoelectric element 319, which is composed of the piezoelectric film 318 and the upper and lower electrodes, needs to be formed above the individual liquid chamber 342. If it is formed on the partition wall that separates the individual liquid chamber 342, it will hinder the deformation of the vibration plate 338, which will cause a decrease in discharge efficiency and damage to the piezoelectric element 319 due to stress concentration.

[0116] The individual liquid chamber substrate 310 is formed with a fluid resistance portion (not shown) that communicates with the individual liquid chamber 342. The fluid resistance portion has a function of supplying ink from the common liquid chamber to the individual liquid chamber 342, and at the same time, it is necessary to prevent and reduce the backflow of ink by the pressure generated in the individual liquid chamber by driving the piezoelectric element 319, and to increase the fluid resistance. When silicon is used for the individual liquid chamber substrate 310 and the individual liquid chamber 342 and the fluid resistance portion are formed by photolithography and etching, there is an advantage that they can be processed under the same conditions as the individual liquid chamber 342. In order to increase the fluid resistance by making the height of the fluid resistance portion lower than the individual liquid chamber, the overetching amount of the individual liquid chamber needs to be controlled by time management, so the fluid resistance cannot be made uniform due to the variation in the etching rate. As a result, the ejection uniformity is deteriorated.

[0117] The fluid resistance portion communicates with the common liquid chamber through an ink supply port in which the vibration plate opens. The individual liquid chambers are divided by partitions, and a corresponding piezoelectric element is formed for each. The height of the individual liquid chambers can be set arbitrarily based on the head characteristics, but is preferably in the range of 20 to 100 μm. The partitions between the individual liquid chambers can be set arbitrarily based on the array density, but the partition width is preferably 10 to 30 μm. If the partition width is narrow, mutual interference between adjacent liquid chambers occurs when the piezoelectric elements of adjacent individual liquid chambers are driven, resulting in large variations in ejection. The partition width can be narrowed by lowering the liquid chamber height.

[0118] (Holding board 344) As described above, since the individual liquid chamber substrate 310 is thin, at 20 to 100 μm, a holding substrate is bonded to the side facing the nozzle plate in order to ensure the rigidity of the individual liquid chamber substrate. Any material can be used as the holding substrate material, but it is necessary to select a material with a similar thermal expansion coefficient to prevent warping of the individual liquid chamber substrate 310. For this reason, glass, silicon, SiO 2 , ZrO 2 , Al 2 O 3 However, a silicon substrate made of the same material as the individual liquid chamber substrate 310 is preferable.

[0119] The holding substrate 344 must have an opening that forms a part of the ink supply port 326. Furthermore, a holding substrate recess is formed in an area facing the individual liquid chamber. It is necessary to secure a space in which the vibration plate can be displaced by driving the piezoelectric element 319. The holding substrate recess is preferably partitioned for each individual liquid chamber 342 and bonded on the individual liquid chamber partition. This can increase the rigidity of the thin individual liquid chamber substrate, making it possible to reduce mutual interference between adjacent liquid chambers when the piezoelectric element is driven. For this purpose, the holding substrate 344 is preferably made of a high rigidity material such as silicon, rather than a low rigidity material such as resin. Furthermore, since the recess of the holding substrate 344 is partitioned for each individual liquid chamber, high processing accuracy is required for high density, and it is desirable for the width of the partition wall of the holding substrate 344 to be 5 to 20 μm in a 300 dpi head.

[0120] The ejection head according to this embodiment is characterized by using the semiconductor substrate described in the second and third embodiments. This allows the use of a substrate with a large piezoelectric constant and a small Young's modulus, thereby providing an ejection head with a large ejection force. It also makes it possible to use materials that have no environmental impact.

[0121] The discharge device according to this embodiment is characterized in that it has a discharge head that is made of the semiconductor substrate described in the second and third embodiments, thereby making it possible to provide a discharge device with strong discharge power.

[0122] Sixth embodiment (Vibration principle of piezoelectric microphone) In this embodiment, a configuration in which a piezoelectric microphone is applied will be described. FIG. 14 is a diagram showing an example of the vibration principle of a piezoelectric microphone. As shown in FIG. 14, a vibration detector 400, which is an example of a piezoelectric microphone (piezoelectric MEMS microphone), detects sound waves by converting the displacement caused by sound waves into an electric signal (voltage) by the piezoelectric effect. Specifically, the vibration detector 400 is a method in which a piezoelectric film 417 that generates electric charges by distortion is directly formed on a vibration part 411 (diaphragm). Here, the directions of each part (function) constituting the vibration detector 400 in the three-dimensional coordinate axis will be described. The X direction is the direction indicating the horizontal direction when the vibration detector shown in FIG. 15 described later is viewed from above. The Y direction is the direction indicating the vertical direction when the vibration detector 400 shown in FIG. 15 is similarly viewed from above. The Z direction is the direction indicating the depth direction when the vibration detector 400 shown in FIG. 15 is similarly viewed from above (for example, the direction from bottom to top when the vibration detector is placed on a flat surface).

[0123] In this method, input of sound waves or the like causes vibration part 411 (diaphragm) to vibrate in the plus and minus Z directions as shown in FIG. 14. This generates stress, and piezoelectric film 417 detects distortion at the portion where the stress occurs. Therefore, in terms of constraints on movement in the plus and minus Z directions, piezoelectric microphones have a higher degree of freedom than capacitive microphones. Furthermore, since vibration detectors can detect distortion with a simple structure, the device fabrication process is simple and they are suitable for miniaturization. Furthermore, since vibration detectors do not require an input power source, the passive circuitry is simple and they can have a wide dynamic range.

[0124] (Partial plan view of a piezoelectric microphone) Next, a partial plan view of the piezoelectric microphone will be described. Fig. 15 is a diagram showing an example of a partial plan view of the piezoelectric microphone according to the first embodiment. As shown in Fig. 15, in the vibration detector, one or more fixed end beam parts 413 (rectangular parts surrounded by dotted lines) are provided between each of one or more vibration parts 411 and the fixed part 412. In the example shown in Fig. 15, one or more vibration parts 411 are each formed into four approximately triangular shapes so as to approximately match four regions divided by diagonals in a rectangle inside the fixed part 412 included in the vibration detector.

[0125] One or more fixed end beam portions 413 (rectangular portions surrounded by dotted lines) are provided for each of the one or more vibrating portions 411, and at least one of the total length of the portions of the one or more fixed end beam portions 413 connected to the fixed portion 412 and the total length of the portions of the one or more fixed end beam portions 413 connected to the vibrating portion 411 is shorter than the length of the portion of the vibrating portion 411 that faces the fixed portion 412.

[0126] That is, each fixed end beam portion is connected to the fixed portion 412 within a range shorter than the length of the side of the vibration portion 411 formed in a substantially triangular shape that is closest to the fixed portion. This makes it possible to alleviate the constraint on the vibration portion 411 from the fixed portion 412. Here, each direction in the three-dimensional coordinate axes (X-axis, Y-axis, Z-axis) of each portion (function) constituting the vibration detector 400 will be described. The X-direction is the direction indicating the horizontal direction when the vibration detector 400 is viewed from above. The Y-direction is the direction indicating the vertical direction perpendicular to the X-direction (horizontal direction) when the vibration detector is viewed from above.

[0127] The Z direction is a direction indicating a depth direction perpendicular to the X direction and the Y direction when the vibration detector 400 is viewed from above (for example, a bottom-to-top direction when the vibration detector 400 is placed on a flat surface). Hereinafter, the three-dimensional coordinate axes in the vibration detector shown in the same positional relationship are assumed to indicate the same directions as in FIG. 15. In this embodiment, a weight part 415 formed of a support layer is added from a fixed part 412 of one or more vibration parts 411 in a direction away from the center of gravity of the one or more vibration parts (free end or tip). This results in a structure that lowers the general natural frequency and improves the sensitivity to vibration in the low-frequency band.

[0128] (Planar view of a piezoelectric microphone) Next, a plan view of a piezoelectric microphone will be described. FIG. 16 is a diagram showing an example of a plan view of a piezoelectric microphone according to the first embodiment. As shown in FIG. 16, a vibration detector, which uses a piezoelectric microphone as an example, has one or more vibration parts 411, a fixed part 412, a fixed end beam part 413 (a rectangular part surrounded by a dotted line), and a distortion detection part 414. The configuration of the vibration part 411 is the same as the shape and number described in FIG. 2. In the example shown in FIG. 16, one or more fixed end beam parts 413 are arranged symmetrically at a predetermined interval on each side facing the fixed part 412.

[0129] Among these, one or more vibrating parts 411 are connected to the fixed part 412 via one or more fixed end beam parts 413. Here, the term "beam part" generally refers to a member that mainly supports the force of a building or the like, and is one of the structural frameworks. That is, in this embodiment, the fixed end beam part refers to a member for connecting the vibrating part 411 and the fixed part 412. Therefore, the one or more fixed end beam parts 413 are disposed between the one or more vibrating parts 411 and the fixed part 412, and have the function of connecting the one or more vibrating parts 411 and the fixed part 412.

[0130] The strain detection unit 414 has a function of detecting sound waves by converting strain accompanying vibration of one or more vibrating units 411 into an electric signal (voltage) by the piezoelectric effect of the strain detection unit 414. The strain detection unit 414 is provided in the vicinity of one or more fixed end beam units 413 or one or more fixed end beam units 413 in one or more vibrating units 411, or in the vicinity of one or more fixed end beam units 413 and one or more fixed end beam units 413 in one or more vibrating units 411. The strain detection unit 414 further comprises a piezoelectric material such as PZT (lead zirconate of titanium Pb(Zr,Ti)O 3 , potassium sodium niobate (KNaNbO 3 The electrodes are made of highly crystalline Pt(111) and the seed layer is made of SrRuO(001) oriented Pt(111). 3 This makes it possible to form a piezoelectric film with a high piezoelectric constant, improving the sensitivity of the microphone.

[0131] In this embodiment, one or more vibration parts 411 and one or more fixed end beam parts 413 constituting the vibration detector are arranged with a size as shown in FIG. 16. In this case, in order to efficiently detect vibrations caused by sound as distortion, the vibration part 411 needs to be large, but the initial capacitance becomes large, and a trade-off occurs in which the load (power consumption) on the circuit side when detecting distortion, noise, etc. increase. Therefore, it is important to maintain sensitivity without widening the detection area, and it is necessary to balance the sizes of the vibration part 411 and the distortion detection part 414. In response to such a trade-off, in this embodiment, the fixed end beam parts 413 connecting one vibration part 411 and the fixed part 412 are provided at two (plural) places, and the distortion detection part 414 is provided so as to straddle the fixed end beam parts 413. As a result, the distortion detection part 414 can efficiently detect distortion while suppressing the area of ​​the distortion detection part 414 itself. Furthermore, it is possible to reduce the capacitance value in the detection circuit of the distortion detection part 414 and reduce power consumption.

[0132] (Side view of a piezoelectric microphone) Next, a side view of the piezoelectric microphone will be described. Fig. 17 is a diagram showing an example of the side of the piezoelectric microphone according to the first embodiment. Fig. 17 shows an outline of the side of the piezoelectric microphone shown in Fig. 16 with respect to side observation area 419 (pentagonal part surrounded by a dotted line). Specifically, Fig. 17 is an example of a schematic diagram that can be observed when side observation area 419 in Fig. 16 is rotated 90° about the Z axis.

[0133] As in the case shown in FIG. 14, the vibration detector 400 has a plurality of fixed end beams 413. The strain detection section 414 is provided on the plurality of fixed end beams 413 and one or more vibrating sections 411, and the strain detection section 414 provided on the plurality of fixed end beams 413 is continuous with the strain detection section 414 provided on one or more vibrating sections 411. Specifically, in the vibration detector, among the fixed section 412, one or more fixed end beams 413, one or more vibrating sections 411, and the strain detection section 414, a set of the fixed section 412, the fixed end beams 413, the vibrating section 411, and the strain detection section 414 are integrally joined to each other. More specifically, in the vibration detector 400, the fixed end beams 413 and the vibrating section 411 are integrally molded (joined) to a part of the fixed section 412 in the Y direction using a well-known semiconductor joining technique.

[0134] The material used for integral molding is, for example, silicon, SiO 2 Furthermore, the strain detection portion 414 is integrally joined to at least one of the vibration portion 411 and the fixed end beam portion 413 by a film forming process in a semiconductor process.

[0135] Moreover, the weight portion 415 is connected to one or more of the vibration portions 411, and is disposed in a direction away from the fixed portion 412 relative to the center of gravity of the one or more vibration portions 411, for example, near the tip of the vibration portion 411. By providing the weight portion 415 near the tip of the vibration portion 411, the moment of inertia of the vibration system becomes larger than before the weight portion 415 is provided. Also, the natural frequency becomes lower than before the weight portion 415 is provided. Furthermore, the displacement of the vibration portion 411 due to sound waves becomes larger than before the weight portion 415 is provided, improving the detection sensitivity.

[0136] Seventh embodiment The movable device and microphone shown in the second and third embodiments are used as wearable terminals because they can be made very lightly. In addition, because KNN is used as the piezoelectric material, one of the advantages is that it has good temperature characteristics in the harsh environments in which wearable terminals are used, especially at high temperatures.

[0137] FIG. 18 is a schematic diagram for explaining the external configuration of a glasses-type wearable terminal 500 as an example. The glasses-type wearable terminal 500 includes a first unit 502 and a second unit 509 as an example. The first unit 502 is arranged in a part of a glasses frame 501 as an example, and includes a controller for controlling the entire wearable terminal 500, a battery, a microphone 504, a speaker 503, and the like. The second unit 509 is also arranged in a part of the glasses frame 501, and includes a display unit 506, a camera 507, a switch 508, various sensors, and the like. The user wears the wearable terminal 500 on the head as if wearing glasses. As a result, the image displayed on the display unit realizes an augmented reality in front of the user's eyes, and provides various information. The microphone 504 uses a micro microphone with the KNN described in the third embodiment as a piezoelectric element. The display unit uses the movable device described in the second embodiment. This allows stable operation to be achieved even in a harsh environment with high temperatures.

[0138] <Eighth embodiment> In the above-described embodiment, the glasses-type wearable terminal 500 is shown as an example of a wearable terminal, but the present embodiment can be applied to other types of wearable terminals. FIG. 19(a) shows a wristwatch-type wearable terminal 600 as another example of a wearable terminal. The wearable terminal 600 includes a display unit 602 arranged on the surface of a main body unit 603, a camera 601 arranged on the side of the main body unit 603, and a band 604 that supports the main body unit 603 and is fixed to the user's arm. Although not shown, the main body unit 603 is provided with a microphone, a speaker, a switch, and the like, similar to the glasses-type wearable terminal 500. FIG. 19(b) shows a diagram of the wearable terminal 600 worn on a user's hand 606. The wearable terminal 600 is characterized by being in close contact with the wrist, and a microphone built into the main body 603 accurately measures the user's pulse. The wrist is a part where a large artery runs close to the surface, and is suitable as a part for measuring the sound waves of the pulse waves generated in the blood vessels of the artery on the skin surface. The third embodiment is optimal as a micro microphone for measuring such pulse waves. In particular, it has sensitivity to low frequencies of several hundred Hz, and the temperature characteristics of the piezoelectric material of KNN are suitable. As a wearable terminal, it is necessary to detect weak pulse sound waves in harsh environments, especially at high temperatures, so this is an application example that can take advantage of the characteristics of KNN.

[0139] <Ninth embodiment> Next, a case where the above-mentioned movable device 13 is applied as an eyeball tilt position detection device will be described. In this embodiment, the "eyeball tilt position" is the position of the pupil or cornea of ​​the eyeball, or the gaze direction of the user. In the following, an example will be described in which the "eyeball tilt position" is the position of the pupil or cornea, and the "eyeball tilt position detection device" is a "pupil (or cornea) position detection device." In addition, the eyeball tilt position detection device described below is synonymous with a gaze direction tracking device (eye tracking device) that detects or tracks the gaze direction of the user continuously or at time intervals.

[0140] Fig. 20 is a schematic diagram showing an eyeball tilt position detection device 1 equipped with an image display function. The arrows shown in the figure indicate the X, Y, and Z directions, and this figure shows the main parts as seen from above (+Y direction). An eyeball tilt position detection device 80 shown in Fig. 20 has a light source 82, a first light deflection unit 83, a light scanning unit 84, a second light deflection unit 85, and a light receiving unit 86.

[0141] The light source 82 has, for example, laser light sources (82r, 82g, 82b) that emit red, green, and blue laser light, and an infrared laser light source 82ir that emits infrared laser light. The laser light sources 82r, 82g, and 82b may be any one or a combination of two, and emit light for drawing an image by the reflecting surface 14 of the movable device 13. In addition, when the eyeball tilt position detection device is not provided with an image display function, the laser light sources (82r, 82g, 82b) may not be provided.

[0142] The infrared laser light source 82ir emits light for detecting the tilt position of the eyeball. The light for detecting the tilt position of the eyeball is not limited to infrared light, and may be visible light. However, from the viewpoint of improving the visibility of the drawn image, invisible light is preferable.

[0143] The first optical deflection unit 83 is, for example, a dichroic mirror, and deflects the light emitted from the light source 82 toward the reflection surface 14 of the movable device 13 while synthesizing the light. The first optical deflection unit 83 may have a plurality of first optical deflection units 83 according to the number of the laser light sources (82r, 82g, 82b) and the infrared laser light source 82ir included in the light source 82. For example, in the case of the configuration shown in Fig. 17, the first optical deflection unit 83 deflects the respective lights while synthesizing them using the first optical deflection units 83-1, 83-2, 83-3, 83-4, and 83-5.

[0144] The reflective surface 14 of the movable device 13 is the movable device 13 described as the optical scanning system. The reflective surface 14 of the movable device 13 scans the light deflected by the first optical deflection unit 3 in a two-dimensional direction toward the second optical deflection unit 5. At this time, the reflective surface 14 of the movable device 13 scans the light deflected by the first optical deflection unit 83 by, for example, raster scanning, to form an image.

[0145] The second optical deflection unit 85 is, for example, a holographic optical element, and deflects the light L1 scanned by the reflecting surface 14 of the movable device 13 toward the user's eyeball 87. At least a part of the light L2 deflected by the second optical deflection unit 85 is incident on the user's eyeball 87 as display image light.

[0146] The light receiving unit 86 receives the light L3 reflected by the user's eyeball 87 from the light L2 deflected by the second light deflection unit 85. The light receiving unit 86 is, for example, an imaging element capable of detecting infrared rays. In addition, a plurality of light receiving units 6 may be provided at positions capable of receiving the light L3 reflected by the user's eyeball 87. The intensity of the light received by the light receiving unit 86 changes depending on the position change of the eyeball (pupil, cornea), that is, the change in the line of sight. Therefore, the eyeball tilt position detection device 80 in this embodiment detects and estimates the eyeball tilt position based on the intensity of the light received by the light receiving unit 86. In addition, the eyeball tilt position detection device 80 may be configured to detect and estimate the eyeball tilt position based on the position of the pupil or cornea included in the image captured by the light receiving unit 86 and the reflection position of the light L2 deflected by the second light deflection unit 85.

[0147] As described above, the eyeball tilt position detection device 80 according to this embodiment can detect the eyeball tilt position while forming an image on the reflective surface 14 of the movable device 13. Furthermore, by using the movable device 13 according to the first embodiment as the reflective surface 14 of the movable device 13, optical scanning and image formation can be performed more efficiently. Furthermore, by improving the efficiency of optical scanning and image formation, image formation and eyeball tilt position detection can be achieved with lower power consumption.

[0148] The eyeball tilt position detection device 80 can also be mounted on a head mounted display as an eye tracking device to detect or track the user's gaze direction. In this case, for example, by lowering the resolution of the image displayed in the area near the user's gaze direction compared to the image displayed in the other area (foveal rendering), image processing can be speeded up compared to when a high-resolution image is displayed over the entire area.

[0149] FIG. 21 is a diagram showing in detail the optical system of the eye tracking device according to the present embodiment. The light emitted from the light source 82 is shaped by the lens 92 and the lens 93. Then, an image is formed by the image forming device 94 equipped with the movable device 13. The light that formed the image is adjusted in the direction of emission by the angle of view changing device 95. This adjustment allows the light to be appropriately projected onto the retina 32. It is also possible to intentionally adjust and switch the direction so that the light does not enter the pupil 31. The angle of view changing device can be appropriately switched upon receiving a signal St from the control unit 96. This significantly improves the accuracy of projection onto the eyeball 87 (pupil 31, retina 32), allowing the user to recognize a highly accurate image. The angle of view changing device 95 includes a movable device 13 that supports a movable part 101 at four points as shown in FIG. 22, and is suitable for vector scanning and the like, which is excellent in fine angle adjustment.

[0150] The light receiving unit 86 receives light Ls reflected by the user's eyeball 87 from the light deflected by the second light deflection unit 85. The light receiving unit 86 is, for example, an imaging element capable of detecting infrared rays. The angle of view changing device 95 accurately captures the convex portion P of the eyeball 87, thereby improving the eye tracking accuracy.

[0151] As described above, one embodiment of the present invention is as follows.

[0152] <1> The semiconductor substrate according to the present embodiment comprises a silicon single crystal substrate 1, a metal film 4 formed on the silicon single crystal substrate and oriented in (111), and a metal oxide layer SrRuO 3and an oxide electrode thin film 5 having the SrRuO 3 The film is characterized by its (001) orientation, which can increase the piezoelectric constant of the piezoelectric film formed on the substrate.

[0153] <2> The semiconductor substrate according to this embodiment is characterized in that the metal film 4 is made of Pt. <1> This provides a semiconductor substrate having a high quality metal oxide layer SrRuO 3 The membrane 5 can be produced using conventional manufacturing processes.

[0154] <3> The semiconductor substrate according to this embodiment has a SiO 2 The present invention is characterized in that it includes a layer 2. <1> ~ <2> As a result, in the portion where the substrate is curved, such as the driving portion of the MEMS mirror, a SiO 2 film having a lower Young's modulus than other materials is used. 2 This makes it possible to employ the above, thereby expanding the driving range of the driving unit.

[0155] <4> The semiconductor substrate according to this embodiment is the SrRuO 3 The (001) orientation rate of <1> ~ <3> This improves the orientation rate of the piezoelectric film formed on the substrate, and increases the piezoelectric constant.

[0156] <5> The semiconductor substrate according to this embodiment is the SrRuO 3 The (001) rocking curve half-width is 6° or less. <1> ~ <4> This improves the orientation rate of the piezoelectric film formed on the substrate, and increases the piezoelectric constant.

[0157] <6> The semiconductor substrate according to this embodiment is the SrRuO 3The (001) rocking curve half-width is 2° or less. <1> ~ <5> This improves the orientation rate of the piezoelectric film formed on the substrate, and increases the piezoelectric constant.

[0158] <7> The semiconductor substrate according to this embodiment is characterized in that the rocking curve half width of the metal film is 6° or less. <1> ~ <6> This improves the orientation rate of the piezoelectric film formed on the substrate, and increases the piezoelectric constant.

[0159] <8> The semiconductor substrate according to this embodiment is characterized in that the rocking curve half width of the metal film is 2° or less. <1> ~ <7> This improves the orientation rate of the piezoelectric film formed on the substrate, and increases the piezoelectric constant.

[0160] <9> The method for producing a semiconductor substrate according to the present embodiment is to form a film at a temperature of 600° C. or higher using SrRuO 3 The present invention is characterized in that a film is formed by <1> ~ <8> This improves the orientation rate of the piezoelectric film formed on the substrate, thereby increasing the piezoelectric constant.

[0161] <10> The actuator according to this embodiment is <1> ~ <8> The present invention is characterized by using the semiconductor substrate described in . This allows the use of a substrate with a large piezoelectric constant and a small Young's modulus, thereby providing an actuator with a wide driving range. In addition, it also makes it possible to use materials that have no environmental impact.

[0162] <11> The ejection head according to this embodiment is <1> ~ <8> The present invention is characterized in that it uses the semiconductor substrate described in . This allows the use of a substrate with a large piezoelectric constant and a small Young's modulus, thereby providing a discharge head with a large discharge force. It also makes it possible to use materials that have no environmental impact.

[0163] <12> The discharge device according to this embodiment is <11> The present invention is characterized in that it has the discharge head described above. This makes it possible to provide a discharge device with strong discharge power.

[0164] <13> The semiconductor substrate according to the present embodiment includes a silicon single crystal substrate 1, a metal film 4 formed on the silicon single crystal substrate 1, and a pseudo-cubic metal oxide layer SrRuO 3 and a thin oxide electrode film 5 having a rocking curve half width of 6° or less, 3 The film is characterized by its (001) orientation, which can increase the piezoelectric constant of the piezoelectric film formed on the substrate. [Explanation of symbols]

[0165] 1. Substrate (silicon is an example) 2 Buffer layer (SiO 2 is an example) 3 First Adhesion Layer 4, 314, 201 Bottom electrode (Pt(111) is an example) 5 Seed layer (oxide electrode thin film, SrRuO 3 (001) is an example) 6, 318, 417 Piezoelectric film (lead titanium zirconate Pb(Zr,Ti)O 3 is an example) 7 Second Adhesion Layer 8, 203, 316 upper electrode 9 Piezoelectric film (potassium sodium niobate (KNaNbO 3 :KNN) is an example.

Claims

1. Silicon single crystal substrate A metal film formed on the silicon single crystal substrate and oriented in (111); A metal oxide layer SrRuO ３ and an oxide electrode thin film having The SrRuO ３ A semiconductor substrate characterized in that the film has a (001) orientation.

2. 2. The semiconductor substrate according to claim 1, wherein the metal film is made of Pt.

3. Between the silicon single crystal substrate and the metal film, SiO ２ 10. The semiconductor substrate of claim 1 comprising a layer.

4. The SrRuO ３ 2. The semiconductor substrate according to claim 1, wherein the (001) orientation rate is 95% or more.

5. The SrRuO ３ The (001) rocking curve half-width is 6° or less 2. The semiconductor substrate according to claim 1 .

6. The SrRuO ３ The half-width of the (001) rocking curve is 2° or less 2. The semiconductor substrate according to claim 1 .

7. The half width of the rocking curve of the metal film is 6° or less.

2. The semiconductor substrate according to claim 1 .

8. The metal film has a rocking curve half-width of 2° or less.

2. The semiconductor substrate according to claim 1 .

9. At a deposition temperature of 600°C or higher, SrRuO ３ The present invention is characterized in that a film is formed by The method for manufacturing a semiconductor substrate according to claim 1 .

10. 2. An actuator using the semiconductor substrate according to claim 1 and the metal film as an electrode.

11. A discharge head using the semiconductor substrate according to claim 1.

12. A discharge device comprising the discharge head according to claim 11.

13. A wearable terminal device using the semiconductor substrate according to claim 1.

14. An eye-tracking device using the semiconductor substrate according to claim 1.

15. Silicon single crystal substrate a metal film formed on the silicon single crystal substrate; A pseudocubic metal oxide layer having a perovskite structure, SrRuO, formed on the metal film. ３ and an oxide electrode thin film having The metal film has a rocking curve half width of 6° or less; The SrRuO ３ A semiconductor substrate characterized in that the film has a (001) orientation.

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