Mask forming and implanting methods using implant stopping layer
View Patent ↗Methods of forming a mask for implanting a substrate and implanting using an implant stopping layer with a photoresist provide lower aspect ratio masks that cause minimal damage to trench isolations in the substrate during removal of the mask. In one embodiment, a method of forming a mask includes: depositing an implant stopping layer over the substrate; depositing a photoresist over the implant stopping layer, the implant stopping layer having a density greater than the photoresist; forming a pattern in the photoresist by removing a portion of the photoresist to expose the implant stopping layer; and transferring the pattern into the implant stopping layer by etching to form the mask. The implant stopping layer may include: hydrogenated germanium carbide, nitrogenated germanium carbide, fluorinated germanium carbide, and/or amorphous germanium carbon hydride (GeHX), where X includes carbon. The methods/mask reduce scattering during implanting because the mask has higher density than conventional masks.
1. A method of forming a mask for implanting a substrate, the method comprising the steps of:
depositing an implant stopping layer over the substrate, wherein the substrate includes at least one trench isolation;
depositing a photoresist over the implant stopping layer, the implant stopping layer having a density and a vertical depth greater than a density and a vertical depth of the photoresist;
forming a pattern in the photoresist by wet etching to remove a portion of the photoresist to expose portions of the implant stopping layer; and
transferring the pattern into the exposed portions of the implant stopping layer by reactive ion etching using the patterned photomask to form the mask, wherein a portion of the implant stopping layer remains over and abutting the at least one trench isolation after the transferring.
2. The method of claim 1 , wherein the implant stopping layer depositing includes depositing from germane in the presence of at least one of the following: ethylene and acetylene, in a reactor at a pressure of approximately 0.1 Torr to approximately 50 Torr, and the substrate at a temperature of approximately 200° C. to approximately 500° C.
3. The method of claim 1 , wherein the patterned photoresist and the patterned implant stopping layer collectively have an aspect ratio of less than approximately 4.0.
4. The method of claim 1 , wherein the implant stopping layer includes at least one of: hydrogenated germanium carbide, itrogenated germanium carbide, fluorinated germanium carbide, and amorphous germanium carbon hydride (GeHX), where X includes carbon.
5. The method of claim 1 , further comprising implanting the substrate, wherein the substrate further includes a plurality of trench isolations, the implanting of the substrate including ion implanting in at least one region of the substrate between the plurality of trench isolations.
6. The method of claim 5 , wherein the implant stopping layer pattern prevents the ion implanting in at least one region of the substrate below at least one of the plurality of trench isolations.
7. A method of implanting a substrate, the method comprising the steps of:
depositing an implant stopping layer over the substrate, wherein the implant stopping layer includes at least one of: hydrogenated germanium carbide, nitrogenated germanium carbide, fluorinated germanium carbide, and amorphous germanium carbon hydride (GeHX), where X includes carbon, and wherein the substrate includes at least one trench isolation;
depositing a photoresist over the implant stopping layer, the implant stopping layer having a density greater than the photoresist;
forming a pattern in the photoresist by wet etching to remove a portion of the photoresist to expose portions of the implant stopping layer;
transferring the pattern into the exposed portions of the implant stopping layer by etching using the patterned photomask to form the mask, wherein a portion of the implant stopping layer remains over and abutting the at least one trench isolation after the transferring; and
implanting the substrate.
8. The method of claim 7 , wherein the implant stopping layer depositing includes depositing from germane in the presence of at least one of the following: ethylene and acetylene, in a reactor at a pressure of approximately 0.1 Torr to approximately 50 Torr, and the substrate at a temperature of approximately 200° C. to approximately 500° C.
9. The method of claim 7 , wherein the patterned photoresist and the patterned implant stopping layer collectively have an aspect ratio of less than approximately 4.0.
10. The method of claim 7 , further comprising implanting the substrate, wherein the substrate further includes a plurality of trench isolations, the implanting of the substrate including ion implanting in at least one region of the substrate between the plurality of trench isolations.
11. The method of claim 10 , wherein the implant stopping layer pattern prevents the ion implanting in at least one region of the substrate below at least one of the plurality of trench isolations.