Egg-Shaped BAW Resonators for Spurious Mode Suppression

The patent applies asymmetry by transitioning from conventional symmetric resonator shapes (circular, rectangular, elliptical) to asymmetric egg-shaped resonators. The egg-shaped geometry features a distinct asymmetry where one end is more rounded while the other is more pointed, breaking the rotational symmetry of traditional designs. This asymmetric shape distribution modifies the acoustic mode patterns, effectively suppressing spurious modes and reducing noise below the resonant frequency, thereby resolving the contradiction between reducing harmful factors and maintaining manufacturing simplicity.

The patent utilizes spheroidality by employing the egg-shaped curved geometry instead of straight-edged rectangular or uniformly curved circular designs. The egg-shaped resonator features smooth continuous curvature transitions from the rounded end to the pointed end, creating a specific stress and acoustic field distribution that minimizes spurious mode generation. This curved geometric approach effectively reduces noise while the egg-shape remains manufacturable using standard semiconductor fabrication techniques, balancing curvature benefits with manufacturing feasibility.

The patent employs an intermediary approach by combining single crystal piezoelectric thin films with egg-shaped resonator structures. The egg-shaped geometry serves as an intermediary design that optimizes the performance-thickness relationship, allowing the thin single crystal films to achieve their full potential while the specific shape compensates for manufacturing difficulties. The asymmetric egg-shape creates favorable stress distributions that enhance the piezoelectric effect, enabling high performance at reduced thicknesses without requiring complex transfer processes.

The patent applies parameter changes by optimizing the resonator shape parameters (aspect ratio, curvature radii, symmetry breaking) to match the characteristics of thin single crystal piezoelectric films. By carefully selecting the egg-shaped geometry parameters, the design maximizes the piezoelectric performance of thin films while maintaining manufacturability. The specific egg-shape parameters are chosen to create optimal stress and electric field distributions that enhance the piezoelectric effect at reduced film thicknesses, resolving the contradiction between reliability and ease of manufacture.