# US 12,009,330 B2 · RF devices with enhanced performance and methods of forming the same > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,009,330 B2 - Document ID: US12009330B2 - Status: Granted - Kind: B2 - Application number: 16/678,551 - Filed: 2019-11-08 - Published: 2020-07-23 - Granted: 2024-06-11 - Earliest claimed: 2019-01-23 - Assignees: Qorvo US, Inc. - Applicants: Qorvo US, Inc. - Inventors: Julio C. Costa; Michael Carroll - Web page: https://patentgrep.com/patent/US12009330B2 ## CPC - H01L 24/20 - H01L 21/565 - H01L 23/3171 - H01L 23/66 - H01L 24/03 - H01L 24/11 - H01L 24/13 - H01L 24/19 - H01L 23/3135 - H01L 2224/131 - H01L ## Abstract The present disclosure relates to a radio frequency (RF) device that includes a mold device die and a multilayer redistribution structure underneath the mold device die. The mold device die includes a device region with a back-end-of-line (BEOL) portion and a front-end-of-line (FEOL) portion over the BEOL portion, and a first mold compound. The FEOL portion includes an active layer formed from a strained silicon epitaxial layer, in which a lattice constant is greater than 5.461 at a temperature of 300K. The first mold compound resides over the active layer. Herein, silicon crystal does not exist between the first mold compound and the active layer. The multilayer redistribution structure includes a number of bump structures, which are at a bottom of the multilayer redistribution structure and electrically coupled to the FEOL portion of the mold device die. ## Claims ### Claim 1 An apparatus comprising: a mold device die comprising a device region, a passivation layer, and a first mold compound, wherein: the device region includes a front-end-of-line (FEOL) portion and a back-end-of-line (BEOL) portion, wherein the FEOL portion comprises an active layer, a contact layer, and isolation sections; a bottom surface of the active layer and a bottom surface of each isolation section are substantially coplanar and are in contact with a top surface of the contact layer, and the BEOL portion is underneath a bottom surface of the contact layer; the isolation sections surround the active layer and extend vertically beyond a top surface of the active layer to define an opening within the isolation sections and over the active layer; the active layer is formed from a strained silicon epitaxial layer, wherein a lattice constant of silicon is greater than 5.461 in the strained silicon epitaxial layer at a temperature of 300K; the isolation sections consist of silicon dioxide; the passivation layer resides over the top surface of the active layer and within the opening, wherein the passivation layer is formed of silicon dioxide, silicon nitride, or a combination of both; and the first mold compound fills the opening and is in contact with the passivation layer, wherein silicon crystal, which has no germanium, nitrogen, or oxygen content, does not exist between the first mold compound and the active layer; and a multilayer redistribution structure formed underneath the BEOL portion of the mold device die, wherein the multilayer redistribution structure comprises a plurality of bump structures, wherein the plurality of bump structures is on a bottom surface of the multilayer redistribution structure and electrically coupled to the FEOL portion of the mold device die. ### Claim 2 (depends on 1) The apparatus of claim 1 wherein: the BEOL portion comprises connecting layers; and the multilayer redistribution structure further comprises redistribution interconnections, wherein the plurality of bump structures is electrically coupled to the FEOL portion of the mold device die via the redistribution interconnections within the multilayer redistribution structure and the connecting layers within the BEOL portion. ### Claim 3 (depends on 1) The apparatus of claim 1 wherein a portion of the first mold compound resides over the isolation sections. ### Claim 4 (depends on 1) The apparatus of claim 1 wherein the first mold compound has a thermal conductivity between 1 W/m·K and 100 W/m·K. ### Claim 5 (depends on 1) The apparatus of claim 1 wherein the first mold compound has a dielectric constant less than 8. ### Claim 6 (depends on 1) The apparatus of claim 1 wherein the first mold compound has a dielectric constant between 3 and 5. ### Claim 7 (depends on 1) The apparatus of claim 1 wherein the FEOL portion is configured to provide at least one of a switch field-effect transistor (FET), a diode, a capacitor, a resistor, or an inductor. ### Claim 8 (depends on 1) The apparatus of claim 1 wherein the active layer of the FEOL portion includes a source, a drain, and a channel between the source and the drain, while the contact layer of the FEOL portion includes a gate structure that extends horizontally underneath the channel. ### Claim 9 An apparatus comprising: a mold device die comprising a device region, a passivation layer, and a first mold compound, wherein: the device region includes a front-end-of-line (FEOL) portion and a back-end-of-line (BEOL) portion, wherein the FEOL portion comprises an active layer, a contact layer, and isolation sections; a bottom surface of the active layer and a bottom surface of each isolation section are substantially coplanar and are in contact with a top surface of the contact layer, and the BEOL portion is underneath a bottom surface of the contact layer; the isolation sections surround the active layer and extend vertically beyond a top surface of the active layer to define an opening within the isolation sections and over the active layer; the active layer is formed from a strained silicon epitaxial layer, wherein a lattice constant of silicon is greater than 5.461 in the strained silicon epitaxial layer at a temperature of 300K; the isolation sections consist of silicon dioxide; the passivation layer resides over the top surface of the active layer and within the opening, wherein the passivation layer is formed of silicon dioxide, silicon nitride, or a combination of both; and the first mold compound fills the opening and is in contact with the passivation layer, wherein silicon crystal, which has no germanium, nitrogen, or oxygen content, does not exist between the first mold compound and the active layer; a multilayer redistribution structure formed underneath the BEOL portion of the mold device die, wherein: the multilayer redistribution structure extends horizontally beyond the mold device die; and the multilayer redistribution structure comprises a plurality of bump structures, wherein the plurality of bump structures on a bottom surface of the multilayer redistribution structure, and electrically coupled to the FEOL portion of the mold device die; and a second mold compound residing over the multilayer redistribution structure to encapsulate the mold device die. ### Claim 10 (depends on 9) The apparatus of claim 9 wherein the first mold compound is formed from a same material as the second mold compound. ### Claim 11 (depends on 9) The apparatus of claim 9 wherein the first mold compound and the second mold compound are formed from different materials. ### Claim 12 (depends on 9) The apparatus of claim 9 wherein: the BEOL portion comprises connecting layers; and the multilayer redistribution structure further comprises redistribution interconnections, wherein the plurality of bump structures is electrically coupled to the FEOL portion of the mold device die via the redistribution interconnections within the multilayer redistribution structure and the connecting layers within the BEOL portion. ### Claim 13 (depends on 9) The apparatus of claim 9 wherein a portion of the first mold compound resides over the isolation sections. ### Claim 14 (depends on 9) The apparatus of claim 9 wherein the first mold compound has a thermal conductivity between 1 W/m·K and 100 W/m·K. ### Claim 15 (depends on 9) The apparatus of claim 9 wherein the first mold compound has a dielectric constant less than 8. ### Claim 16 (depends on 9) The apparatus of claim 9 wherein the first mold compound has a dielectric constant between 3 and 5. ### Claim 17 (depends on 9) The apparatus of claim 9 wherein the FEOL portion is configured to provide at least one of a switch field-effect transistor (FET), a diode, a capacitor, a resistor, or an inductor. ### Claim 18 (depends on 9) The apparatus of claim 9 wherein the active layer of the FEOL portion includes a source, a drain, and a channel between the source and the drain, while the contact layer of the FEOL portion includes a gate structure that extends horizontally underneath the channel.