Non-conformal oxide liner and manufacturing methods thereof

1. A method comprising:

forming a fin protruding over a substrate;

forming a conformal oxide layer over an upper surface and along sidewalls of the fin;

forming a non-conformal oxide layer over the upper surface and along the sidewalls of the fin, wherein forming the non-conformal oxide layer comprises performing an anisotropic oxide deposition process, wherein the anisotropic oxide deposition process is a plasma process, wherein the plasma process is performed using a precursor comprising silicon and using a gas source comprising an oxygen gas, wherein a first portion of the conformal oxide layer along the sidewalls of the fin physically contacts a second portion of the non-conformal oxide layer along the sidewalls of the fin; and

forming a gate electrode over the fin, wherein the conformal oxide layer and the non-conformal oxide layer are between the fin and the gate electrode.

2. The method of claim 1 , wherein the plasma process is an anisotropic plasma-enhanced atomic layer deposition (PEALD) process having a plurality of cycles, wherein the oxygen gas is activated into a plasma by a radio frequency (RF) power supply, wherein the RF power supply is turned on for a continuous period of time in each cycle of the PEALD process.

3. The method of claim 1 , wherein the plasma process is an anisotropic plasma-enhanced atomic layer deposition (PEALD) process having a plurality of cycles, wherein the oxygen gas is activated into a plasma by a radio frequency (RF) power supply, wherein the RF power supply is turned on and off repeatedly in each cycle of the PEALD process.

4. The method of claim 1 , wherein the non-conformal oxide layer is formed to be thicker over the upper surface of the fin than along the sidewalls of the fin.

5. The method of claim 1 , wherein the conformal oxide layer is formed over the upper surface and along the sidewalls of the fin before the non-conformal oxide layer is formed.

6. The method of claim 1 , wherein the non-conformal oxide layer is formed over the upper surface and along the sidewalls of the fin before the conformal oxide layer is formed.

7. A method comprising:

forming a fin protruding over a substrate;

forming a conformal oxide layer over an upper surface and along sidewalls of the fin;

forming a non-conformal oxide layer over the upper surface and along the sidewalls of the fin, wherein forming the non-conformal oxide layer comprises performing an anisotropic plasma treatment, wherein the anisotropic plasma treatment converts an exterior portion of the fin into the non-conformal oxide layer, wherein a first portion of the conformal oxide layer along the sidewalls of the fin physically contacts a second portion of the non-conformal oxide layer along the sidewalls of the fin; and

forming a gate electrode over the fin, wherein the conformal oxide layer and the non-conformal oxide layer are between the fin and the gate electrode.

8. The method of claim 7 , wherein performing the anisotropic plasma treatment comprises:

supplying a gas source comprising an oxygen gas to a process chamber for the anisotropic plasma treatment;

after supplying the gas source to the process chamber for a first period of time, activating the oxygen gas into a plasma by turning on a radio frequency (RF) power source for a pre-determined period of time;

turning off the RF power source after the pre-determined period of time elapses;

after turning off the RF power source, continuing supplying the gas source to the process chamber for a second period of time; and

stop supplying the gas source after the second period of time elapses.

9. A method comprising:

forming a fin;

forming isolation regions on opposing sides of the fin;

forming a first oxide layer over a top surface and along sidewalls of the fin, wherein the first oxide layer is non-conformal and extends from the top surface of the fin to the isolation regions, wherein the first oxide layer has different thicknesses over the top surface of the fin and along the sidewalls of the fin, wherein the first oxide layer has a first thickness over the top surface of the fin, and has a second thickness along the sidewalls of the fin, wherein the first thickness is greater than the second thickness, wherein forming the first oxide layer comprises performing an anisotropic plasma-enhanced atomic layer deposition (PEALD) process, wherein the anisotropic PEALD process comprises a plurality of cycles and is performed using a precursor comprising silicon and using a gas source comprising an oxygen gas; and

forming a second oxide layer over the top surface and along the sidewalls of the fin, wherein the second oxide layer is conformal, wherein the second oxide layer comprises a first portion that extends along the sidewalls of the fin, wherein the first portion of the second oxide layer is in contact with the first oxide layer.

10. The method of claim 9 , further comprising forming a gate electrode over the fin, over the first oxide layer, and over the second oxide layer.

11. A method comprising:

forming a fin protruding above a substrate;

forming a non-conformal gate dielectric layer and a conformal oxide layer over a top surface of the fin and along sidewalls of the fin, wherein forming the non-conformal gate dielectric layer comprises performing an anisotropic plasma-enhanced atomic layer deposition (PEALD) process, wherein the anisotropic PEALD process comprises a plurality of cycles and is performed using a precursor comprising silicon and using a gas source comprising an oxygen gas, wherein the non-conformal gate dielectric layer has a first thickness over the top surface of the fin and has a second thickness along the sidewalls of the fin, the first thickness being different from the second thickness; and

forming a gate electrode over the fin and over the non-conformal gate dielectric layer.

12. The method of claim 11 , wherein performing the anisotropic PEALD process comprises, for each of the plurality of cycles of the anisotropic PEALD process:

supplying the precursor to a process chamber of the anisotropic PEALD process between a first time instant and a second time instant;

supplying the gas source to the process chamber between the first time instant and a third time instant, wherein the second time instant is between the first time instant and the third time instant; and

activating the oxygen gas into a plasma by turning on a radio frequency (RF) power source during a fourth time instant and a fifth time instant, wherein the fourth time instant and the fifth time instant are between the second time instant and the third time instant.

13. The method of claim 12 , wherein the RF power source is turned on and off alternately between the fourth time instant and the fifth time instant.