Patent ID: 12262175

REFERENCE SIGNS

10—substrate,11—back chamber,12—first silicon layer,13—first oxide layer,14—second silicon layer;20—second oxide layer;30—piezoelectric unit,31—first electrode layer,32—piezoelectric layer,33—second electrode layer;40—slit;50—opening;60—additional film layer,61—first part,62—second part,63—through slot;70—metal pad.

DESCRIPTION OF EMBODIMENTS

The embodiments described below with reference to the drawings are exemplary only for explaining the present disclosure and should not be construed as limiting the present disclosure.

FIG.1is a schematic cross-sectional view of an acoustic transducer according to an embodiment of the present disclosure. As shown inFIG.1, an embodiment of the present disclosure provides an acoustic transducer, including first silicon layer10, second oxide layer20, piezoelectric unit30, additional film layer60and metal pad70.

The substrate10includes from bottom to top a first silicon layer12, a first oxide layer13and a second silicon layer14. The substrate10is provided with a back chamber11. Optionally, an inner contour surface of the back chamber11is a circular groove structure. The back chamber11sequentially penetrates through the first silicon layer12and the first oxide layer13, and the second silicon layer14is exposed by the back chamber11. In an embodiment, the first oxide layer13of SiO2material is prepared by vapor deposition method, thermal oxidation method or thermal decomposition method on the first silicon layer12of silicon material, and the second silicon layer14is formed on the first oxide layer13by vapor deposition method, thermal oxidation method or thermal decomposition method. The second silicon layer14and the first silicon layer12may be made of the same material. The first oxide layer13is located under the second silicon layer14and has a significantly lower etching rate compared with the second silicon layer14. When the slit40or the back chamber11is formed, it is ensured that the etching process is more uniformly stopped at the interface of the first oxide layer13and the second silicon layer14.

The second oxide layer20is formed on the substrate10, and the second oxide layer20is formed by magnetron sputtering on the surface of the second silicon layer14.

The piezoelectric unit30is formed on the second oxide layer20and includes from bottom to top a first electrode layer31, a piezoelectric layer32, and a second electrode layer33stacked in sequence.

The first electrode layer31is formed on the second oxide layer20by electron beam lift-off or magnetron sputtering, and the first electrode layer31is patterned by a photolithography process. The first electrode layer31is connected to the bottom electrode pad (not shown) through a bottom electrode lead (not shown), the material of the first electrode layer31can be one or more of Al, Mo, W, Pt, Cu, Ag, Au, ZrN, or may also be other materials with good electrical conductivity. In an embodiment, the first electrode layer31is made of molybdenum (Mo).

The piezoelectric layer32is deposited on the first electrode layer31. The piezoelectric layer32has the characteristics of generating mechanical vibration in the presence of an electric field and the characteristics of generating an electric field when the mechanical vibration occurs. The piezoelectric layer32can be lead zirconate titanate, nitrogen aluminum oxide or barium titanate or any other piezoelectric material. In an embodiment, the piezoelectric layer32is made of aluminum nitride.

The second electrode layer33is formed on the piezoelectric layer32by the electron beam lift-off or the magnetron sputtering, and the second electrode layer33is patterned using a photolithography process. The second electrode layer33passes through the top electrode lead (not shown) is connected to the top electrode pad (not shown), and the material of the second electrode layer33can be one or more of Al, Mo, W, Pt, Cu, Ag, Au, ZrN, or other materials having good conductive property. In an embodiment, the second electrode layer33is made of molybdenum (Mo).

A slit40and an opening50are formed in the piezoelectric unit30. The slit40is formed in the middle of the second electrode layer33. In an embodiment, the slit40has an inner contour formed as a circular groove. An axis of the slit40coincides with an axis of the back chamber11. The slit40sequentially penetrates through the second electrode layer33, the piezoelectric layer32, the first electrode layer31, the second oxide layer20and the second silicon layer14, until the slit40is in communication with the back chamber11. The opening50is formed at an edge of the second electrode layer33. Optionally, the opening50has a circular groove structure. The opening50sequentially penetrates through the second electrode layer33and the piezoelectric layer32, and the first electrode layer31is exposed by the opening50.

The metal pad70is stacked on the first electrode layer31at the opening50, so that the metal pad70is electrically connected to the first electrode layer31. In an embodiment, a patterned hard mask is formed on the second electrode layer33, and the opening50is etched at the edge of the second electrode layer33through dry etching or wet etching, so that part of the first electrode layer31is exposed, and then the metal pad70is deposited on the first electrode layer31to form electrical connection.

The additional film layer60includes a first part61and a second part62. In an embodiment, the first part61and the second part62integrally form into one piece, to facilitate the molding process and improve the structural stability. The second part62is located at the peripheral edge of the first part61. The size and shape of the first part61conforms to the second electrode layer33, and the first part61is lay on the second electrode layer33and covers the slit40. The size and shape of the second part62conforms to the opening50, and the second part62is lay on the metal pad70and covers the opening50. A through slot63is formed penetrating through the second part62. The position of the through slot63corresponds to the position of the metal pad70. An orthographic projection of the metal pad70along the thickness direction of the second part62is located within the through slot63, and the metal pad70is exposed by the through slot63. The additional film layer60may be any type of polymer.

Through providing the additional film layer60to cover the slit40, the sound pressure loss due to air leakage caused by the slit40is reduced. The additional film layer60has certain tensile deformation capacity, when the piezoelectric unit30vibrates, the additional film layer60deforms, to reduce the restriction to the movement of the piezoelectric unit30.

In the present disclosure, the additional film layer60is formed by rolling or hot pressing, and the additional film layer60is stacked on the piezoelectric unit30and the metal pad70. The additional film layer60is a photosensitive film. In an embodiment, the rolling includes using two or more rollers arranged in a certain form and the rolling the film to be stretched into an additional film layer60having a certain thickness and surface profile. The hot pressing process uses a movable mold and a fixed mold, and a mold cavity is provided between the movable mold and the fixed mold, the film is placed in the mold cavity and then hot-pressed to conform to the shape of the mold cavity, thereby completing the molding of the additional film layer60. Alternatively, the additional thin film layer60may also be formed by photolithography process.

Compared to the typical fully filled liquid type, the piezoelectric unit30can vibrate with maximum displacement and lowest restriction, so as to effectively improve the SPL and the structural reliability.

In the present disclosure, the first part61and the second part62have a height difference. The second part62is located below the first part61. During deformation of the piezoelectric unit30, the deformation of the first part61is smooth due to the height difference, so as to avoid the restricted deformation of the piezoelectric unit30, thereby improving the SPL and reliability of the acoustic transducer.

As shown inFIG.1, the first part61and the second part62have the same thickness, and the thicknesses at each position of the first and second parts61,62are consistent. The deformation process of the piezoelectric unit30is parabolic, so as to avoid the restricted deformation of the piezoelectric unit30due to the arrangement of the additional film layer60, thereby improving the reliability of the acoustic transducer.

As shown inFIG.1, the thickness of the metal pad70is smaller than the thickness of the piezoelectric layer32, the plane of where the bottom of the second part62is located intersects with the piezoelectric layer32, and a gap is defined between the bottom surface of the second part62and the top surface of the first electrode layer31. As a result, when the piezoelectric layer32deforms, less restriction occurs, which further improve compliance of the acoustic transducer.

FIGS.2A-2Eare flow diagrams of showing manufacture of an acoustic transducer according to embodiments of the present disclosure. The method includes the following process:

As shown inFIG.2A, a substrate10is provided. A first silicon layer12is formed. The first oxide layer13of SiO2material is prepared by vapor deposition method, thermal oxidation method or thermal decomposition method on the first silicon layer121, and the second silicon layer14is formed on the first oxide layer13by vapor deposition method, thermal oxidation method or thermal decomposition method. The second silicon layer14and the first silicon layer12can be made of the same material.

As shown inFIG.2B, a second oxide layer20is grown on the surface of the second silicon layer14by magnetron sputtering. A piezoelectric unit30is formed on the second silicon layer14. The first electrode layer31is formed on the second oxide layer20by electron beam lift-off or magnetron sputtering, and the first electrode layer31is patterned by using a photolithography process. The first electrode layer31is connected to the bottom electrode pad through a bottom electrode lead. The piezoelectric layer32is deposited on the first electrode layer31, the second electrode layer33is formed on the piezoelectric layer32by electron beam lift-off or magnetron sputtering, and the second electrode layer33is patterned using the photolithography process. The second electrode layer33is connected to the top electrode pad through a top electrode lead.

As shown inFIG.2C, a slit40is etched in the middle of the second electrode layer33, and an opening50is etched at the edge of the second oxide layer33. The slit sequentially penetrates through the second electrode layer33, the piezoelectric layer32, the first electrode layer31, the second oxide layer20and the second silicon layer14. The opening50sequentially penetrates the second electrode layer33and the piezoelectric layer32, and the first electrode layer31is exposed by the opening50. In an embodiment, a patterned hard mask is formed on the second electrode layer33, and the slit40and the opening50are formed in the second electrode33by dry etching or wet etching.

As shown inFIG.2D, a metal pad70is deposited on the first electrode layer31at the opening50. The metal pad70is deposited on the first electrode layer31by electron beam lift-off or magnetron sputtering to form an electrical connection. An additional film layer60is formed by rolling or hot pressing. The second part62is lay on the metal pad70and covers the opening50. A through slot63is formed penetrating through the second part62. The position of the through slot63corresponds to the position of the metal pad70. An orthographic projection of the metal pad70along the thickness direction of the second part62is located within the through slot63, and the metal pad70is exposed by the through slot63. In an embodiment, the additional film layer60is a photosensitive film. In an embodiment, the rolling includes using two or more rollers arranged in a certain form and the rolling the film to be stretched into an additional film layer60having a certain thickness and surface profile. The hot pressing process uses a movable mold and a fixed mold, and a mold cavity is provided between the movable mold and the fixed mold, the film is placed in the mold cavity and then hot-pressed to conform to the shape of the mold cavity.

As shown inFIG.2E, a back chamber11is formed on the bottom of the first silicon layer12. The back chamber11sequentially penetrates through the first silicon layer12and the first oxide layer13, and the second silicon layer14is exposed by the back chamber11. In an embodiment, the back chamber11is formed by dry etching or wet etching.

In the acoustic transducer prepared by the above-mentioned methods, the additional film layer60is formed by rolling or hot pressing, and the first part61of the additional film layer60is lay on the second electrode layer33and covers the slit40, the second part62is lay on the metal pad70, so that the piezoelectric unit30can vibrate with the maximum displacement and the lowest restriction, thereby effectively improving the SPL and structural reliability, the thickness of the additional film layer60is uniformly distributed on the top surface of the piezoelectric unit30, which is suitable for acoustic transducers having a larger area.

The structures, features and effects of the present disclosure have been described in detail above based on the embodiments shown in the drawings. The above descriptions are only preferred embodiments of the present disclosure, but the present disclosure is not limited to the embodiments shown in the drawings. Changes or modifications made based on the concept of the present disclosure are still within the protection scope of the present disclosure.