Integration of FBAR filter(s) and on-chip inductors

[0001] The present invention is related to the field of Microelectromechanical Systems (MEMS). More specifically, the present invention is related to integration of film bulk acoustic resonators (FBAR) filters with on-chip inductors.

[0002] Radio frequency (RF) front-end passives, such as transceivers and receivers are increasingly needed for wireless communication. These front-end passives include front-end filters. RF front-end filters consist of FBAR have been found to have a number of advantages over other technologies, such as surface acoustic wave (SAW) devices and ceramic filters, particularly at relatively high frequencies. A FBAR filter typically consists of series FBARs as well as shunt FBARs. The bandwidth of a FBAR filter is typically limited by the electromechanical coupling (K²) of piezoelectric materials. For example, the electromechanical coupling (K²) of polycrystalline ZnO films is about 4%, depending on the film's crystal orientation and quality.

[0003] The present invention will be described by way of exemplary embodiments, but not limitations, illustrated in the accompanying drawings in which like references denote similar elements, and in which:

[0004] FIG. 1 illustrates a cross sectional view of a portion of a component with two FBARs and an on-chip inductor, in accordance with one embodiment;

[0005] FIG. 2 illustrates an exposed top view of the inductor of FIG. 1 in accordance with one embodiment;

[0006] FIGS. 3a-3f illustrate a method for making the on-chip inductor and the FBAR of FIG. 1, in accordance with one embodiment; and

[0007] FIG. 4 illustrates a system having the component of FIG. 1 in accordance with one embodiment.

[0008] Embodiments of the present invention include, but are not limited to, a component having FBAR filter(s) and on-chip inductors, method for making such component, and system having such component.

[0009] Various aspects of the illustrative embodiments will be described using terms commonly employed by those skilled in the art to convey the substance of their work to others skilled in the art. However, it will be apparent to those skilled in the art that the present invention may be practiced with only some of the described aspects. For purposes of explanation, specific numbers, materials and configurations are set forth in order to provide a thorough understanding of the illustrative embodiments. However, it will be apparent to one skilled in the art that the present invention may be practiced without the specific details. In other instances, well-known features are omitted or simplified in order not to obscure the illustrative embodiments.

[0010] Various operations will be described as multiple discrete operations, in turn, in a manner that is most helpful in understanding the present invention, however, the order of description should not be construed as to imply that these operations are necessarily order dependent. In particular, these operations need not be performed in the order of presentation.

[0011] The phrase “in one embodiment” is used repeatedly. The phrase generally does not refer to the same embodiment, however, it may. The terms “comprising”, “having” and “including” are synonymous, unless the context dictates otherwise.

[0012] Referring now to FIG. 1, wherein a cross sectional view of a portion of a component having a FBAR filter and an on-chip inductor in accordance with one embodiment is shown. As illustrated, for the embodiment, component 100 includes a FBAR filter having series FBAR 102 and shunt FBAR 104. Further, component 100 includes on-chip inductor 106 electrically coupled to FBAR 102 and 104, and cavity 108 exposing undersides of the metal layers employed to form on-chip inductor 106 (hereinafter, simply inductor), and FBAR 102 and 104.

[0013] Resultantly, the FBAR filter may be responsive to signals over a wider bandwidth, without the needs of disposing long line inductors on a circuit board on which component 100 is to be mounted, and coupling the long line inductors to FBARs 102 and 104.

[0014] As illustrated, for the embodiment, inductor 106 is formed on a portion of metal layer 112, which is exposed by via 122. Further, for the embodiment, inductor 106 is of a coil type (see also FIG. 2 which illustrates an exposed top view of inductor 106 formed on top of passivation layer 144a, without the higher layers). In alternate embodiments, inductor 106 may have a different form factor.

[0015] Series FBAR 102, more specifically, its bottom electrode, is formed on a portion of metal layer 116. Its top electrode is formed by metal 132. Shunt FBAR 104, more specifically, its bottom electrode, on the other hand, is formed with corresponding portions of metal layer 114 and 116. Its top electrode is formed by metal 134. The portion of metal layer 116 contributing in the forming of shunt FBAR 104 has a thickness that is thicker than the thickness of the portion of metal layer 116 contributing in the forming of series FBAR 102.

[0016] For the embodiment, metal layer 116 is electrically coupled to metal layer 114, which except for the portion disposed in via 122, is generally separated from metal layer 112 by inter-layer dielectric layer 124. By virtue of metal layer 114 being electrically coupled to via 122, metal layer 116 is also in electrical contact with metal layer 112. Further, top electrode 132 of series FBAR 102 is also in electrical contact with metal layer 112. [Note that these electrical connections are circuit dependent. In other applications or embodiments, series FBAR 102 and shunt FBAR 104 may be electrically coupled to each other and other circuit elements in other manners.]

[0017] In various embodiments, each of metal layers 112, 114 and 116 may be formed employing a metal such as aluminum (Al), molybdenum (Mo), platinum (PI), or other materials with like properties.

[0018] In various embodiments, metal layer 112 is a relatively thick metal layer, with a thickness greater than 0.7 μm.

[0019] In various embodiments, the inter-layer dielectric layer may be formed employing dielectric material such as silicon oxide (SiO₂) or other dielectic materials of like properties.

[0020] It should be noted that while for ease of understanding, only two FBAR 102-104 and one inductor 106 are shown in FIG. 1, in alternate embodiments, component 100 may include more or less FBAR and/or inductors.

[0021] FIGS. 3a-3f illustrate a method of making component 100 in accordance with one embodiment. The method reflects the desired electrical connections between the top and bottom electrodes of series FBAR 102 and shunt FBAR 104 and other circuit elements of the embodiment. In alternate embodiments, the method may be modified to accommodate other desired electrical connections between the top and bottom electrodes of series FBAR 102 and shunt FBAR 104 and other circuit elements.

[0022] For the embodiment, passivation layer 144a and hard mask 144b are first deposited on a top side and a bottom side of substrate 142 respectively, op 302. In various embodiments, substrate 142 may be a silicon (Si) substrate, and passivation layer and hard mask 144a-144b may be formed employing silicon nitride (SiN), deposited through low pressure chemical vapor deposition (LPCVD).

[0023] Next, metal layer 112, including inductor 106, may be formed by deposition and patterning, op 304. In various embodiments, portions of metal layer 112 are also patterned to form bonding pads of component 100.

[0024] Then, inter-layer dielectric layer 124 is formed on top of metal layer 112 by deposition (and optionally, chemical mechanical polishing (CMP)), and via 122 is formed by etching, op 306.

[0025] Thereafter, metal layer 114 is formed on top of a portion of inter-layer dielectric layer 124, including via 122, op 308, by deposition, patterning and etching. Thus, metal layer 114 is electrically coupled to metal layer 112 through via 122.

[0026] Next, metal layer 116 is formed on top of metal layer 114 and inter-layer dielectric layer 124 by deposition and patterning, op 310. Thus, metal layers 114 and 116 are in electrical contact with each other. Further, metal layer 116 is also in electrical contact with metal layer 112 through metal layer 114. As described earlier, the “thinner” portion of metal layer 116 forms a part of series FBAR 102 (bottom electrode), and the corresponding portions of metal layers 114 and 116 form a part of shunt FBAR 104 (bottom electrode). Further, the portion of metal layer 116 contributing in the forming of shunt FBAR filter 104 is thicker than the portion contributing in the forming of series FBAR 102.

[0027] Next, another dielectric layer 126 is deposited on top of metal layer 116, op 312. The dielectric layer 126 is etched to create the pad areas 120, op 312, and the top electrodes are deposited, op 312. In various embodiments, dielectric layer 126 may be an aluminum nitride (AIN) layer.

[0028] Finally, a series of etching are performed to create the underside cavity 108 (see FIG. 1). In various embodiments, the etching may be performed employing potassium hydroxide (KOH).

[0029] FIG. 4 illustrates a system in accordance with one embodiment. As illustrated, for the embodiment, system 400 includes a communication interface 402 for receiving and sending RF signals. Communication interface 402 includes a number of components, in particular, a RF transceiver 406 having front end 408. More specifically, for the embodiment, front end 408 is component 100 endowed with a FBAR filter, formed with FBAR 102-104 and complemented by inductor 106 as earlier described.

[0030] Further, system 400 includes digital signal processor 404 coupled to communication interface 402 for processing the signals received, and providing communication interface 402 with the signals to be transmitted.

[0031] Depending on the applications, system 400 may include other components, including but are not limited to volatile and non-volatile memory, mass storage (such as hard disk, compact disk (CD), digital versatile disk (DVD) and so forth), and so forth.

[0032] In various embodiments, system 400 may be a personal digital assistant (PDA), a wireless mobile phone, a tablet computing device, a laptop computing device, a desktop computing device, a set-top box, an entertainment control unit, a digital camera, a digital video recorder, a CD player, a DVD player, or other digital device of the like.

[0033] Thus, it can be seen from the above descriptions, a novel component having a FBAR filter with FBAR and on-chip inductor, method for making such a component, and a system having such a component have been described. While the present invention has been described in terms of the foregoing embodiments, those skilled in the art will recognize that the invention is not limited to the embodiments described. The present invention can be practiced with modification and alteration within the spirit and scope of the appended claims.

[0034] Thus, the description is to be regarded as illustrative instead of restrictive on the present invention.