Capacitive pressure sensor in an overmolded package
An overmolded pressure sensor package is provided. The pressure sensor die (Pcell) is capped so that the Pcell has enhanced rigidity to withstand stress effects produced by the molding encapsulant. The Pcell cap includes a hole located away from the Pcell diaphragm, so that external gas pressure can be experienced by the Pcell, while at the same time directing moisture away from the diaphragm. Gel does not need to be used, and instead a soft film can be deposited on the Pcell to protect the Pcell diaphragm from excess moisture, if needed. The Pcell cap can take the form of, for example, a dummy silicon wafer or a functional ASIC.
1. A semiconductor device package comprising:
a pressure sensor die comprising a pressure deformable diaphragm disposed at a region of a first major surface of the pressure sensor die;
a shaped cap wafer attached to the first major surface of the pressure sensor die, wherein
a cavity is formed between a portion of the shaped cap wafer and a portion of the first major surface of the pressure sensor die,
the portion of the first major surface of the pressure sensor die comprises the region where the pressure deformable diaphragm is disposed, and
the shaped cap wafer includes a pressure inlet port configured to admit gasses external to the cavity into the cavity;
a package substrate;
an active semiconductor device adhesively coupled to the package substrate at a first major surface of the active semiconductor device, wherein
the pressure sensor die is adhesively coupled to a second major surface of the active semiconductor device, and
the second major surface of the active semiconductor device opposes the first major surface of the active semiconductor device;
an encapsulant over and around the package substrate, over and around the active semiconductor device, over and around the pressure sensor die, and around the shaped cap wafer.
2. The semiconductor device package of claim 1 wherein the pressure inlet port is located in a region of the shaped cap wafer opposing the portion of the first major surface of the pressure sensor die that is not the region including the pressure deformable diaphragm.
3. The semiconductor device package of claim 1 wherein the shaped cap wafer comprises a silicon wafer shaped to form the cavity.
4. The semiconductor device package of claim 1 wherein the shaped cap wafer comprises an active semiconductor device having an external shape configured to form the cavity.
5. The semiconductor device package of claim 1 further comprising:
encapsulant over the shaped cap wafer, wherein the encapsulant is formed to provide a package inlet port over the pressure inlet port of the shaped cap wafer.
6. The semiconductor device package of claim 1 , wherein
the active semiconductor device comprises a control die,
the pressure sensor die is electrically coupled to the control die, and
the control die is configured to receive and process signals generated by the pressure sensor die.
7. A semiconductor device package comprising:
a pressure sensor die comprising a pressure deformable diaphragm disposed at a region of a first major surface of the pressure sensor die;
a shaped cap wafer attached to the first major surface of the pressure sensor die, wherein
a cavity is formed between a portion of the shaped cap wafer and a portion of the first major surface of the pressure sensor die,
the portion of the first major surface of the pressure sensor die comprises the region where the pressure deformable diaphragm is disposed, and
the shaped cap wafer includes a pressure inlet port configured to admit gasses external to the cavity into the cavity;
a package substrate, wherein
the pressure sensor die is adhesively coupled to the package substrate at a second major surface of the pressure sensor die that opposes the first major surface of the pressure sensor die; and
an encapsulant over and around the package substrate, over and around the pressure sensor die, and around the shaped cap wafer.
8. The semiconductor device package of claim 7 further comprising:
an active semiconductor device electrically coupled to the pressure sensor die, wherein
the active semiconductor device is configured to receive and process signals generated by the pressure sensor die, and
at least a portion of the active semiconductor device is encapsulated by the encapsulant.
9. The semiconductor device package of claim 8 wherein the active semiconductor device comprises the shaped cap wafer.
10. The semiconductor device package of claim 9 further comprising:
encapsulant over the shaped cap wafer, wherein the encapsulant is formed to provide a package inlet port over the pressure inlet port of the shaped cap wafer.
11. A semiconductor device package comprising:
a pressure sensor die comprising a pressure deformable diaphragm disposed at a region of a first major surface of the pressure sensor die;
a shaped cap wafer attached to the first major surface of the pressure sensor die, wherein
a cavity is formed between a portion of the shaped cap wafer and a portion of the first major surface of the pressure sensor die,
the portion of the first major surface of the pressure sensor die comprises the region where the pressure deformable diaphragm is disposed, and
the shaped cap wafer includes a pressure inlet port configured to admit gasses external to the cavity into the cavity;
a package substrate, wherein
the package substrate comprises a substrate pressure inlet, and
the shaped cap wafer is adhesively attached to the package substrate such that the substrate pressure inlet and the shaped cap wafer pressure inlet are aligned; and
an encapsulant over and around the package substrate, over and around the shaped cap wafer, and around at least a portion of the pressure sensor die.
12. The semiconductor device package of claim 11 further comprising:
an active semiconductor device electrically coupled to the pressure sensor die, wherein
the active semiconductor device is configured to receive and process signals generated by the pressure sensor die, and
at least a portion of the active semiconductor device is encapsulated by the encapsulant.
13. The semiconductor device package of claim 12 wherein the active semiconductor device is adhesively attached to a second major surface of the pressure sensor die that opposes the first major surface of the pressure sensor die.
14. The semiconductor device package of claim 12 wherein the active semiconductor device comprises the shaped cap wafer.
15. A method for forming a packaged semiconductor device assembly, the method comprising:
providing a surface embodied within the packaged semiconductor device assembly;
affixing a pressure sensor die to a portion of the surface, wherein
the pressure sensor die is affixed to the surface at a first major surface of the pressure sensor die, and
a second major surface of the pressure sensor die, opposing the first major surface, comprises a pressure deformable diaphragm;
affixing a shaped cap wafer to the second major surface of the pressure sensor die, wherein
a cavity is formed between a portion of the shaped cap wafer and a portion of the second major surface of the pressure sensor die and the portion of the second major surface comprises the pressure deformable diaphragm, and
the shaped cap wafer includes a pressure inlet port configured to admit gasses external to the cavity into the cavity; and
forming an encapsulated region over and around the pressure sensor die and the shaped cap wafer, wherein
said forming is performed to provide a package inlet port over the pressure inlet port of the shaped cap wafer, and
the package inlet port is configured to admit gasses external to the encapsulant into the cavity through the pressure inlet port of the shaped cap wafer.
16. The method of claim 15 further comprising:
performing said forming the encapsulated region using a film-assisted molding technique to form the package inlet port.
17. A tire pressure monitoring system comprising:
a wheel module, configured to be mounted in a vehicle tire, comprising
a process controller configured to process signals from one or more sensors,
a pressure sensor die, coupled to the process controller, and comprising a pressure deformable diaphragm disposed at a region of a first major surface of the pressure sensor die,
a shaped cap wafer adhesively coupled to the first major surface of the pressure sensor die, wherein
a cavity is formed between a portion of the shaped cap wafer and a portion of the first major surface of the pressure sensor die,
the portion of the first major surface of the pressure sensor die comprises the region where the pressure deformable diaphragm is disposed, and
the shaped cap wafer includes a pressure inlet port configured to admit gasses external to the cavity into the cavity, and
a package substrate, wherein the pressure sensor die is adhesively coupled to the package substrate at a second major surface of the pressure sensor die that opposes the first major surface of the pressure sensor die, and
an encapsulant over and around the package substrate, over and around the pressure sensor die, and around the shaped cap wafer, and
a radio-frequency (RF) transmitter, coupled to the process controller, configured to transmit sensor information provided by the process controller.
18. The tire pressure monitoring system of claim 17 wherein the shaped cap wafer comprises a silicon wafer shaped to form the cavity.