Silicon germanium mask for deep silicon etching
Polycrystalline silicon germanium (SiGe) can offer excellent etch selectivity to silicon during cryogenic deep reactive ion etching in an SF 6 /O 2 plasma. Etch selectivity of over 800:1 (Si:SiGe) may be achieved at etch temperatures from −80 degrees Celsius to −140 degrees Celsius. High aspect ratio structures with high resolution may be patterned into Si substrates using SiGe as a hard mask layer for construction of microelectromechanical systems (MEMS) devices and semiconductor devices.
1. A method, comprising:
depositing an etch mask on a semiconductor material, wherein the etch mask comprises silicon germanium and the semiconductor material is not silicon germanium;
patterning the etch mask with a plurality of features;
transferring the plurality of features in the etch mask to the semiconductor material at a first temperature by deep reactive ion etching in an SF 6 /O 2 plasma, and
removing the etch mask at a second temperature by reactive ion etching in an SF 6 /O 2 plasma, where the second temperature is higher than the first temperature.
2. The method of claim 1 , wherein the semiconductor material comprises silicon.
3. The method of claim 2 , wherein the semiconductor material comprises a silicon substrate.
4. The method of claim 1 , wherein the step of depositing a etch mask comprises performing chemical vapor deposition of silicon germanium.
5. The method of claim 1 , wherein the step of performing the reactive ion etch comprises applying inductively coupled plasma and the SF 6 /O 2 plasma sufficient to remove the silicon germanium and not the semiconductor material.
6. The method of claim 1 , wherein the step of performing the deep reactive ion etch comprises cryogenic etching the semiconductor material with the SF 6 /O 2 plasma.
7. The method of claim 1 , further comprising cooling the semiconductor material to a temperature between −80 degrees Celsius and −140 degrees Celsius before transferring.
8. The method of claim 1 , wherein patterning the etch mask comprises: forming a transfer material on the etch mask;
patterning the plurality of features into the transfer material; and
transferring the plurality of features into the etch mask.
9. The method of claim 8 , wherein the step of forming a transfer material comprises forming a photoresist film on the etch mask.
10. The method of claim 8 , wherein patterning the plurality of features into the transfer material comprises patterning with at least one of photolithography, ion beam lithography, or electron beam lithography.
11. The method of claim 8 , wherein the step of transferring the plurality of features comprises transferring high aspect ratio features.
12. The method of claim 1 , wherein the plurality of features comprises components of at least one of a microprocessor, a micro electro-mechanical system (MEMS) rotational rate sensor, a MEMS accelerometer, a micro-fluidic mixing device, a micro-mirror, a micro-pillar, a deep trench capacitor, an isolation for high frequency circuitry, or a power device.
13. The method of claim 1 , further comprising integrating the plurality of features into at least one of a mobile phone, a hand-held personal communication systems (PCS) unit, a portable data unit, a personal data assistant, a GPS enabled device, a navigation device, a set top box, a music player, a video player, an entertainment unit, or a fixed location data unit.
14. The method of claim 1 , further comprising removing the etch mask after transferring the plurality of features in the etch mask to the semiconductor material.
15. The method of claim 1 , further comprising maintaining the etch mask at a temperature between 10 degrees Celsius and −110 degrees Celsius before removing the etch mask.
16. The method of claim 1 , wherein the etch mask comprises boron.
17. The method of claim 1 , wherein the etch mask comprises polycrystalline silicon germanium.
18. The method of claim 7 , wherein transferring the plurality of features into the etch mask comprises etching the etch mask with an SF 6 /O 2 plasma at a temperature between 10 degrees Celsius and −110 degrees Celsius.
19. A method, comprising:
depositing an etch mask layer on a semiconductor material, wherein the etch mask layer comprises silicon germanium and the semiconductor material is not silicon germanium;
forming a transfer material on the etch mask layer;
patterning the plurality of features into the transfer material;
transferring the plurality of features into the etch mask layer;
transferring the plurality of features in the etch mask layer to the semiconductor material at a first temperature by deep reactive ion etching in an SF 6 /O 2 plasma; and
removing the etch mask layer at a second temperature by reactive ion etching in an SF 6 /O 2 plasma, where the second temperature is higher than the first temperature.
20. A method, comprising:
forming a transfer material on a semiconductor material;
patterning the plurality of features into the transfer material, wherein at least a portion of transfer material is removed from the semiconductor material;
depositing an etch mask layer, wherein the etch mask layer comprises silicon germanium and the semiconductor material is not silicon germanium, and at least a portion of the etch mask layer is in direct contact with the semiconductor material, and at least a portion of the etch mask layer is on top of the transfer material;
removing the transfer material from the semiconductor material, wherein the plurality of features are transferred to the etch mask layer;
transferring the plurality of features in the etch mask layer to the semiconductor material at a first temperature by deep reactive ion etching in an SF 6 /O 2 plasma; and
removing the etch mask layer at a second temperature by reactive ion etching in an SF 6 /O 2 plasma, where the second temperature is higher than the first temperature.