ScAIN etch mask for highly selective etching
A fabrication process employing the use of ScAlN as an etch mask is disclosed. The ScAlN etch mask is chemically nonvolatile in fluorine-based etch chemistries and has a low sputter yield, resulting in greater etch mask selectivity and reduced surface roughness for silicon and other semiconductor materials. The ScAlN etch mask has an etch mask selectivity of greater than 200,000:1 relative to silicon compared to an etch mask selectivity of less than 40,000:1 for a prior art AlN etch mask relative to silicon. Further, due to reduced sputtering of the ScAlN etch mask, and thus reduced micromasking, the ScAlN etch mask yielded a surface roughness of 0.6 μm compared to a surface roughness of 2.8 μm for an AlN etch mask.
1. A method for etching, the method comprising the steps of:
providing a substrate;
forming a layer of ScAlN etch mask material on a surface of the substrate;
forming a ScAlN etch mask from the layer of ScAlN etch mask material, the ScAlN etch mask including at least one opening therethrough;
etching the substrate through the at least one opening in the ScAlN etch mask using a fluorine-based etch chemistry; and
removing the ScAlN etch mask from the surface of the substrate.
2. The method of claim 1 , wherein the substrate is one of a semiconductor wafer, a processed semiconductor wafer, and a composite wafer.
3. The method of claim 1 , wherein the step of forming the layer of ScAlN etch mask material includes a step of depositing ScAlN by physical vapor deposition or metal organic chemical vapor deposition.
4. The method of claim 1 , wherein the step of forming the layer of ScAlN etch mask material includes a step of depositing ScAlN by sputtering a single ScAl target or co-sputtering separate Sc and Al targets.
5. The method of claim 1 , wherein the step of forming the layer of ScAlN etch mask material includes the steps of:
depositing a high compressive stress layer of ScAlN; and
depositing a low compressive stress layer of ScAlN on the high compressive stress layer of ScAlN.
6. The method of claim 1 , wherein the layer of ScAlN etch mask material includes at least approximately 12.5% Sc.
7. The method of claim 1 , wherein a thickness of the layer of ScAlN etch mask material is between approximately 3 nm and approximately 10 μm.
8. The method of claim 1 , wherein a thickness of the layer of ScAlN etch mask material is at least approximately 3 nm.
9. The method of claim 1 , wherein the step of forming the ScAlN etch mask includes the steps of:
spinning a layer of photoresist onto the layer of ScAlN etch mask material;
exposing the layer of photoresist;
developing the thus exposed layer of photoresist, thereby exposing at least a portion of the layer of ScAlN etch mask material; and
removing the thus exposed at least a portion of the layer of ScAlN etch mask material, thereby creating the at least one opening in the ScAlN etch mask.
10. The method of claim 9 , wherein the step of removing the thus exposed at least a portion of the layer of ScAlN etch mask material includes a step of at least one of reactive ion etching, tetramethylammonium hydroxide-based wet chemistry etching, and KOH-based wet chemistry etching of the thus exposed at least a portion of the layer of ScAlN etch mask material.
11. The method of claim 10 , wherein if the step of removing the thus exposed at least a portion of the layer of ScAlN etch mask material includes the step of reactive ion etching, the step of reactive ion etching employs at least one of a chlorine-based chemistry process, a gas switching time multiplexed mode process, and a Bosch process.
12. The method of claim 1 , wherein the step of etching the substrate includes a step of reactive ion etching the substrate through the at least one opening in the ScAlN etch mask.
13. The method of claim 12 , wherein the step of reactive ion etching the substrate employs at least one of a deep reactive ion etching process, a gas switching time multiplexed mode process, and a Bosch process.
14. The method of claim 12 , wherein the step of reactive ion etching the substrate employs backside He cooling of the substrate.
15. The method of claim 1 , wherein the step of etching the substrate forms at least one physical feature or at least one physical element in the substrate.
16. The method of claim 1 , wherein the step of etching the substrate etches completely through the substrate.
17. The method of claim 1 , wherein the step of removing the ScAlN etch mask employs a tetramethylammonium hydroxide-based chemistry or a KOH-based chemistry.