Method of reducing roughness of a thick insulating layer
View Patent ↗A method for reducing roughness of an exposed surface of an insulator layer on a substrate, by depositing an insulator layer on a substrate wherein the insulator layer includes an exposed rough surface opposite the substrate; treating the first substrate to form a zone of weakness beneath the insulator layer; and smoothing the exposed rough surface of the insulator layer by exposure to a gas plasma in a chamber. The chamber contains therein a gas at a pressure of greater than 0.25 Pa but less than 30 Pa, and the gas plasma is created using a radio frequency generator applying to the insulator layer a power density greater than 0.6 W/cm 2 but less than 10 W/cm 2 for at least 10 seconds to less than 200 seconds. Substrate bonding and layer transfer may be carried out subsequently to transfer the thin layer of substrate to the insulator layer and to a second substrate.
1. A method for reducing roughness of an exposed surface of an insulator layer on a substrate, which comprises:
depositing an insulator layer on a first substrate wherein the insulator layer comprises an exposed rough surface opposite the substrate;
treating the first substrate to form a zone of weakness beneath the insulator layer; and
smoothing the exposed rough surface of the insulator layer by exposure to a gas plasma in a chamber, wherein the chamber contains therein a gas at a pressure of greater than 0.25 Pa but less than 30 Pa, with the gas plasma created using a radiofrequency generator applying to the insulator layer a power density greater than 0.6 W/cm 2 but less than 10 W/cm 2 for at least 10 seconds to less than 200 seconds.
2. The method of claim 1 wherein the gas pressure inside the chamber is in the range of 3Pa to 13 Pa.
3. The method of claim 1 , wherein the gas plasma is created by the radiofrequency generator applying power for between 30 to 120 seconds.
4. The method of claim 1 wherein the gas plasma is formed from a gas selected from the group consisting of oxygen, argon, and nitrogen.
5. The method of claim 1 , wherein the insulator layer is a nitride, oxynitride or oxide having a thickness that is between about 20 nm to several micrometers.
6. The method of claim 1 wherein the insulator layer is an oxide deposited on the substrate using low pressure chemical vapor deposition.
7. A method for reducing roughness of an exposed surface of an insulator layer on a substrate, which comprises:
depositing an insulator layer on a first substrate wherein the insulator layer comprises an exposed rough surface opposite the substrate;
treating the first substrate to form a zone of weakness beneath the insulator layer; and
smoothing the exposed rough surface of the insulator layer by exposure to a gas plasma in a chamber, wherein the chamber contains therein a gas at a pressure of greater than 0.25 Pa but less than 30 Pa, with the gas plasma created using a radiofrequency generator applying to the insulator layer a power density greater than 0.6 W/cm 2 but less than 10 W/cm 2 for at least 10 seconds to less than 200 seconds,
wherein the insulator layer is silicon dioxide formed from tetraethylorthosilicate using low pressure chemical vapor deposition at a pressure in the range of 40 Pa to 200 Pa.
8. The method of claim 1 which further comprises treating the insulator layer to a densification anneal at a temperature in the range from 600° C. to 800° C.
9. The method of claim 1 wherein the zone of weakness is formed inside the first substrate to define a layer of substrate material beneath the insulator layer.
10. The method of claim 9 wherein the zone of weakness is formed by implantation of atomic species and the smoothing is conducted prior to implantation of the atomic species.
11. The method of claim 9 wherein the exposed surface is sufficiently smooth to facilitate bonding to another substrate, and the method further comprises:
bonding a second substrate to the insulator layer; and
detaching the useful layer from the first substrate to transfer that layer and the insulator layer to the second substrate.
12. The method of claim 11 which further comprises:
cleaning the exposed surface of the insulator layer; and
treating the exposed surface of the insulator layer to an activation plasma.
13. The method of claim 12 wherein the activation plasma is formed in a chamber that contains a gas at a pressure of about 5 Pa to 10 Pa.
14. The method of claim 13 wherein the activation plasma is created using a radiofrequency generator applying to the insulator layer a power density of about 0.2W/cm 2 to about 3W/cm 2 for about 5 to 60 seconds.
15. The method of claim 12 wherein the cleaning of the exposed surface of the insulator layer comprises a chemical cleaning.
16. The method of claim 15 wherein the chemical cleaning of the exposed surface comprises treatment of the surface by an SC1 solution followed by treatment of the surface with an SC2 solution.
17. A method for reducing roughness of an exposed surface of an insulator layer on a substrate, which comprises:
depositing an insulator layer on a substrate wherein the insulator layer comprises an exposed rough surface opposite the substrate;
treating the first substrate to form a zone of weakness beneath the insulator layer; and
smoothing the exposed rough surface of the insulator layer by exposure to a gas plasma in a chamber, wherein the chamber contains therein a gas at a pressure of greater than 0.25 Pa but less than 30 Pa, with the gas plasma created using a radiofrequency generator applying to the insulator layer a power density greater than 0.6 W/cm 2 but less than 10 W/cm 2 for at least 10 seconds to less than 200 seconds,
wherein the exposed surface of the insulator layer is about 3 Å rms to 20 Å rms.