Hermetically sealed molecular spectroscopy cell with dual wafer bonding
A method includes forming a plurality of layers of an oxide and a metal on a substrate. For example, the layers may include a metal layer sandwiched between silicon oxide layers. A non-conductive structure such as glass is then bonded to one of the oxide layers. An antenna can then be patterned on the non-conductive structure, and a cavity can be created in the substrate. Another metal layer is deposited on the surface of the cavity, and an iris is patterned in the metal layer to expose the one of the oxide layers. Another metal layer is formed on a second substrate and the two substrates are bonded together to thereby seal the cavity.
1. A device, comprising:
a first substrate having opposite first and second sides, a cavity extending from the second side of the first substrate through the first substrate to the first side of the first substrate;
a first oxide layer on the first side of the first substrate;
a metal layer on the first oxide layer;
a second oxide layer on the metal layer, the cavity extending from the first side of the first substrate through the first oxide layer and through the metal layer to the second oxide layer;
an insulative layer on the second oxide layer;
an antenna on the insulative layer;
a second substrate; and
a structure that seals the cavity by bonding the second substrate to the first substrate.
2. The device of claim 1 , further comprising an electronic bandgap structure on the insulative layer.
3. The device of claim 1 , wherein the cavity contains dipolar molecules.
4. The device of claim 3 , wherein the dipolar molecules are water molecules, and the cavity has a pressure of less than 0.15 mbars.
5. The device of claim 1 , wherein the insulative layer includes at least one of glass, ceramic or, silicon.
6. The device of claim 1 , wherein: the first substrate includes at least one of a semiconductor wafer, a ceramic or a metal; and the second substrate includes at least one of a semiconductor wafer, a ceramic or a metal.
7. The device of claim 1 , wherein the insulative layer includes glass, the first substrate includes a first semiconductor wafer, and the second substrate includes a second semiconductor wafer.
8. The device of claim 1 , wherein:
the antenna is a first antenna;
the device includes an amplifier, a filter, a signal generator, and a second antenna on the insulative layer;
the signal generator is coupled to the first antenna and is configured to generate a transmit signal to the first antenna;
the amplifier is coupled to the second antenna and is configured to generate an error signal based on a receive signal from the second antenna and the transmit signal; and
the filter is coupled to the amplifier and to the signal generator, and is configured to generate a control output signal, based on the error signal, to adjust a frequency of the transmit signal generated by the signal generator.
9. The device of claim 1 , wherein the metal layer is a first metal layer, and the bonding structure includes a second metal layer.
10. A device, comprising:
a first semiconductor substrate having opposite first and second sides, a cavity extending from the second side of the first semiconductor substrate through the first semiconductor substrate to the first side of the first semiconductor substrate;
a first oxide layer on the first side of the first semiconductor substrate;
a metal layer on the first oxide layer;
a second oxide layer on the metal layer, the cavity extending from the first side of the first semiconductor substrate through the first oxide layer and through the metal layer to the second oxide layer;
a glass sheet on the second oxide layer;
first and second antennas on the glass sheet;
a second semiconductor substrate;
a structure that seals the cavity by bonding the second semiconductor substrate to the first semiconductor substrate; and
a transceiver electrically coupled to the first and second antennas, the transceiver configured to inject a transmit signal into the cavity through the first antenna, generate an error signal based on a receive signal from the second antenna and the transmit signal, and dynamically adjust a frequency of the transmit signal based on the error signal;
the cavity containing dipolar molecules and having an internal pressure of less than 0.15 mbars.
11. The device of claim 10 , wherein the transceiver includes:
a signal generator coupled to the first antenna, the signal generator configured to generate the transmit signal;
an amplifier coupled to the second antenna, the amplifier configured to generate the error signal; and
a loop filter coupled to the amplifier and to the signal generator, the loop filter configured to generate a control output signal to the signal generator based on the error signal.
12. The device of claim 10 , wherein the metal layer is a first metal layer, and the bonding structure includes a second metal layer.