Oxidizing treatment of aluminum nitride films in semiconductor device manufacturing
Thin AlN films are oxidatively treated in a plasma to form AlO and AlON films without causing damage to underlying layers of a partially fabricated semiconductor device (e.g., to underlying metal and/or dielectric layers). The resulting AlO and AlON films are characterized by improved leakage current compared to the AlN film and are suitable for use as etch stop layers. The oxidative treatment involves contacting the substrate having an exposed AlN layer with a plasma formed in a process gas comprising an oxygen-containing gas and a hydrogen-containing gas. In some implementations oxidative treatment is performed with a plasma formed in a process gas including CO 2 as an oxygen-containing gas, H 2 as a hydrogen-containing gas, and further including a diluent gas. The use of a hydrogen-containing gas in the plasma eliminates the oxidative damage to the underlying layers.
1. A method for treating a layer of material on a semiconductor substrate, the method comprising:
(a) depositing a layer of aluminum nitride on a semiconductor substrate; and
(b) after the deposition of the aluminum nitride layer has been completed, contacting the semiconductor substrate in a process chamber with a plasma formed from a process gas comprising an oxygen-containing gas and H 2 to modify the aluminum nitride layer, wherein the plasma treatment in (b) comprises:
(i) generating high frequency (HF) radio frequency (RF) plasma from the process gas comprising H 2 and the oxygen-containing gas, using a frequency of between 1.8 MHz and 2.45 GHz; and
(ii) contacting the semiconductor substrate positioned on a support in the process chamber with a plasma that comprises the HF RF plasma and chemically modifying aluminum nitride in the deposited aluminum nitride layer to form a layer comprising Al and O, and thereby decreasing leakage current of the aluminum nitride layer, wherein the process chamber comprises an inlet for introducing the process gas or the plasma into the process chamber, and wherein the plasma is formed in the process chamber or outside of the process chamber housing the semiconductor substrate.
2. The method of claim 1 , wherein the oxygen-containing gas comprises a gas selected from a group consisting of CO 2 , N 2 O, and O 2 .
3. The method of claim 1 , wherein the modified layer obtained after plasma treatment in (b) is an AlO layer or an AlON layer.
4. The method of claim 1 , wherein the leakage current of the treated layer is less than about 2×10 −6 A/cm 2 at 4 MV/cm.
5. The method of claim 1 , wherein the aluminum nitride layer resides over and in contact with a metal layer and a dielectric layer.
6. The method of claim 5 , wherein the metal layer is a copper layer.
7. The method of claim 6 , wherein the plasma treatment in (b) does not cause oxidation of the underlying copper layer that is detectable by reflectometry.
8. The method of claim 5 , wherein the metal layer is a tungsten layer.
9. The method of claim 1 , wherein the process gas further comprises a diluent gas.
10. The method of claim 1 , wherein the process gas further comprises a diluent gas selected from the group consisting of He, Ar, Ne, N 2 , and mixtures thereof.
11. The method of claim 1 , wherein the aluminum nitride layer has a thickness of less than about 50 Å.
12. The method of claim 1 , wherein the aluminum nitride layer has a thickness of between about 10-30 Å.
13. The method of claim 1 , wherein the oxygen-containing gas is CO 2 and wherein the plasma treatment in (b) modifies the aluminum nitride layer to form an AlO or AlON layer.
14. The method of claim 1 , wherein the process chamber is a plasma-enhanced atomic layer deposition (PEALD) or a plasma-enhanced chemical vapor deposition (PECVD) process chamber.
15. The method of claim 1 , wherein (b) further comprises forming low frequency (LF) radio frequency (RF) plasma.
16. The method of claim 1 , wherein (b) comprises treating the substrate with a plasma at a pressure of between about 0.5-10 Torr and at a process temperature of between about 300-400° C.
17. The method of claim 1 , further comprising:
applying photoresist to the semiconductor substrate;
exposing the photoresist to light;
patterning the photoresist and transferring the pattern to the semiconductor substrate; and
selectively removing the photoresist from the semiconductor substrate.