Obviousness

Obviousness Analysis of US Patent 8114697 under 35 U.S.C. § 103

This analysis identifies combinations of prior art references that would render the claims of US patent 8114697 obvious to a person having ordinary skill in the art (POSITA) at the time of the invention (priority date: December 18, 2007). A POSITA in this field would possess knowledge of MEMS fabrication, piezoelectric materials, acoustic transducer design, and basic electrical and mechanical engineering principles.

Independent Claims 1 and 4: Piezoelectric Microphone with Series-Patterned Mating Electrode

Claims 1 (method) and 4 (apparatus) describe a piezoelectric microphone comprising a silicon substrate, an insulating layer, a piezoelectric plate, and a mating electrode formed on the piezoelectric plate, where the mating electrode includes cathode and anode mat patterns coupled to each other in series. Claim 9 further specifies that the mating electrode may be more dense at an outer portion or a center portion of the piezoelectric plate.

Combination of Prior Art: KR20080052230A (ETRI, 2008) in view of the general knowledge of piezoelectric device design, particularly regarding electrode patterns for voltage enhancement, and references disclosing piezoelectric microphones.

Reasoning for Obviousness:

1. Basic Piezoelectric Microphone Structure: The fundamental components of a piezoelectric microphone, including a silicon substrate, an insulating layer, and a piezoelectric layer with electrodes for converting physical vibrations into electrical signals, were well-known in the prior art. For example, Cai et al. (2005) describe the packaging of a PZT MEMS microphone, including fabrication of a silicon circular diaphragm. KR20030062899A (Lee, 2003) also discusses a piezoelectric bimorph microphone.
2. Series Electrode Pattern: The patent US8114697 explicitly states that "the conventional mating electrode layer 109 has a parallel pattern" and highlights the disadvantage of parallel patterns in producing a lower voltage level compared to a series pattern under the same pressure (US8114697, Description,). The patent further demonstrates that a series mating pattern can transfer a higher voltage (US8114697, Description,).
   • KR20080052230A (ETRI, 2008), titled "Interlocking electrode structure for electronic device and electronic device using same," discloses advanced electrode structures from the same assignee, with a priority date predating US8114697. Although specific details of its "interlocking" pattern are not fully elaborated in the provided snippets, the title itself suggests non-conventional, potentially series-arranged patterns to optimize electrical output.
   • Furthermore, prior art in related fields, such as Surface Acoustic Wave (SAW) devices, commonly employed interdigitated electrodes (IDTs) which are patterned arrangements of positive and negative electrodes. JPH11186867A (Kyocera Corp, 1999) discloses such a "Surface acoustic wave device". Another patent, US8552618B2, which pertains to SAW devices, explicitly describes "IDT electrodes having a serially divided structure". This demonstrates that the concept of serially coupling patterned electrodes in piezoelectric devices to achieve specific electrical characteristics was known in the art.
3. Motivation to Combine: A POSITA would be motivated to modify the electrode patterns of a known piezoelectric microphone (e.g., as described in Cai et al. or KR20030062899A) by incorporating a series electrode arrangement. This motivation stems directly from the recognized problem of low voltage output from conventional parallel electrode patterns and the well-understood electrical principle that connecting capacitors in series increases the total voltage output (US8114697, Description,). Optimizing the placement of these patterns, such as at the outer circumference or center where strain is greatest, as indicated in US8114697's FIG. 3 (US8114697, Description,-), would be a routine design choice for a POSITA seeking to maximize microphone sensitivity.

Therefore, the microphone apparatus and method of claims 1, 4, and 9 would have been obvious to a POSITA.

Independent Claims 2 and 10: Piezoelectric Speaker with Differentially Etched Piezoelectric Plate

Claims 2 (method) and 10 (apparatus) describe a piezoelectric speaker comprising a silicon substrate, an insulating layer, a piezoelectric plate including a piezoelectric strain region and a vibration region, and a mating electrode formed in the piezoelectric strain region, where the piezoelectric plate is thinner in the vibration region than in the piezoelectric strain region. Claims 3 and 11 specify the vibration region is at an outer portion. Claim 16 details etching methods.

Combination of Prior Art: KR20060127013A (Lee, 2006) in combination with widely known MEMS fabrication techniques, particularly dry etching, and general acoustical engineering principles.

Reasoning for Obviousness:

1. Basic Piezoelectric Micro Speaker Structure: KR20060127013A (Lee, 2006) explicitly discloses a "Piezoelectric micro speaker and manufacturing method thereof," which would include the fundamental components of a piezoelectric speaker on a silicon substrate, an insulating layer, a piezoelectric plate, and electrodes.
2. Differential Etching for Thinner Vibration Region: The core inventive step is making the vibration region thinner than the piezoelectric strain region. The patent US8114697 acknowledges that "the micro-speaker has a low output" as a problem with piezoelectric-type acoustic transducers (US8114697, Description,). It proposes that a thinner outer circumferential portion (vibration region) "vibrates depending on the strain generated... thereby generating sound. Accordingly, the more thinly the outer circumferential portion 603 is etched, the more easily it vibrates with even small strain" (US8114697, Description,). This principle that a thinner diaphragm is more flexible and therefore vibrates more readily with less input is a fundamental concept in mechanical and acoustic engineering.
   • Cai et al. (2005) describe the fabrication of silicon circular diaphragms for PZT MEMS microphones with thicknesses of 15-25 μm using deep reactive ion etching (DRIE). They emphasize that "dry etching, reactive ion etching (RIE), is the most suited process for realizing the piezoelectric MEMS structure due to its higher etching resolution". These advanced etching techniques are capable of precise material removal and creating diaphragms of desired thicknesses. General semiconductor manufacturing guides also detail dry etching as a method for precise material removal and pattern formation.
3. Motivation to Combine: A POSITA seeking to improve the acoustic output and efficiency of a piezoelectric micro speaker (as taught by KR20060127013A) would be motivated to increase the flexibility of the vibrating membrane. Differentially etching the piezoelectric plate to create a thinner vibration region, particularly at the outer portion where significant vibration occurs, would be an obvious solution to achieve this enhanced flexibility and improve sound generation. The selection of dry etching methods (e.g., ICP etching as mentioned in claim 16) would be an obvious choice due to their known precision and ability to create smooth surfaces in MEMS fabrication.

Therefore, the speaker apparatus and method of claims 2, 3, 10, 11, and 16 would have been obvious to a POSITA.

Independent Claim 18: Piezoelectric Speaker-Microphone Integrated Device

Claim 18 describes a piezoelectric speaker-microphone integrated device in which the piezoelectric microphone of claim 1 and the piezoelectric speaker of claim 10 are provided over the same silicon substrate.

Combination of Prior Art: KR20030075906A (Samsung, 2003) or KR20040003096A (Mazeltelcom, 2004) in combination with the obvious modifications to the microphone (as in claims 1/4) and speaker (as in claims 2/10) as discussed above.

Reasoning for Obviousness:

1. Integration of Microphone and Speaker: The concept of integrating a microphone and a speaker onto a single silicon substrate was explicitly known in the prior art. KR20030075906A (Samsung, 2003) discloses a "MEMS device used as microphone and speaker and method of fabricating the same." Similarly, KR20040003096A (Mazeltelcom, 2004) describes an "Earmicrophone wherein speaker and mike are combined with each other." The patent US8114697 itself acknowledges the benefits of such integration, stating that manufacturing on a silicon wafer "reduces costs since the manufacture can be performed by batch processing, and miniaturizes the device because a plurality of transducers and amplifiers can be integrated on a single chip" (US8114697, Description,).
2. Motivation to Combine: Given the well-established advantages of miniaturization and cost reduction through MEMS integration, a POSITA would be highly motivated to combine the improved piezoelectric microphone (with series-patterned electrodes) and the improved piezoelectric speaker (with a differentially etched piezoelectric plate) onto a single silicon substrate. The integration of such functionalities into a single chip was a known trend and a desirable goal in the field of MEMS acoustic transducers. The manufacturing process for integrating these devices would involve applying known MEMS techniques for sequential deposition, patterning, and etching on a common substrate (US8114697, Description,-).

Therefore, the integrated device of claim 18 would have been obvious to a POSITA.

Dependent Claims (General Obviousness)

Many dependent claims recite features that are well-established in MEMS fabrication or represent obvious optimizations:

• Suspended Diaphragms (Claims 5, 12): Etching the silicon substrate from the rear to suspend the piezoelectric plate (or regions thereof) is a standard MEMS technique for creating vibrating diaphragms, as evidenced by Cai et al. (2005) discussing silicon diaphragm fabrication via DRIE.
• Insulating Layers (Claims 6, 13): The use of silicon oxide or silicon nitride as insulating layers is conventional in semiconductor and MEMS manufacturing (US8114697, Description,,).
• Piezoelectric Plate Formation (Claims 7, 14): Adhering a piezoelectric plate using an epoxy adhesive or depositing it via a sol-gel method are known techniques for forming piezoelectric layers in MEMS devices.
• Piezoelectric Materials (Claims 8, 15): The recited piezoelectric materials (PZT, PMN-PT, PVDF, ZnO, AlN, or lead-free piezoelectric material) are standard choices for piezoelectric transducers. PZT is explicitly mentioned in Cai et al.'s work on MEMS microphones.
• Insulating Layer Etched and Filled (Claim 17): While specific, modifying the insulating layer with etched patterns filled with a rubber or highly elastic resin film to affect resonance frequency (US8114697, Description,) would be an obvious engineering choice for a POSITA seeking to tune the acoustic performance of a speaker. Such material choices for modifying mechanical properties and acoustic response are part of routine design optimization.

In conclusion, the claimed inventions in US8114697, individually and in combination, would have been obvious to a person having ordinary skill in the art in light of the cited prior art and the general knowledge in the field of MEMS acoustic transducers.