Hardmask materials
Hardmask films having high hardness and low stress are provided. In some embodiments a film has a stress of between about −600 MPa and 600 MPa and hardness of at least about 12 GPa. In some embodiments, a hardmask film is prepared by depositing multiple sub-layers of doped or undoped silicon carbide using multiple densifying plasma post-treatments in a PECVD process chamber. In some embodiments, a hardmask film includes a high-hardness boron-containing film selected from the group consisting of Si x B y C z , Si x B y N z , Si x B y C z N w , B x C y , and B x N y . In some embodiments, a hardmask film includes a germanium-rich GeN x material comprising at least about 60 atomic % of germanium. These hardmasks can be used in a number of back-end and front-end processing schemes in integrated circuit fabrication.
1. A method of forming a hardmask film on a semiconductor substrate, the method comprising:
receiving the semiconductor substrate in a plasma-enhanced chemical vapor deposition (PECVD) process chamber; and
forming a hardmask film having a hardness of greater than about 12 GPa, and a stress of between about −600 MPa and 600 MPa by PECVD on the semiconductor substrate, wherein the PECVD hardmask deposition process comprises:
depositing doped or undoped multi-layer silicon carbide film using multiple densifying plasma treatments, the process comprising;
(a) introducing a process gas comprising tetramethylsilane and an inert gas into the process chamber and forming a dual frequency plasma to deposit a first sublayer of the silicon carbide hardmask film, wherein the power level for high frequency plasma is between about 0.04-0.2 W/cm 2 and the power level for low-frequency plasma is between about 0.17-0.6 W/cm 2 ;
(b) removing the tetramethylsilane from the process chamber, wherein said removing comprises purging the process chamber with a gas selected from the group consisting of Ar, He, H 2 , and mixtures thereof;
(c) introducing a plasma treatment gas into the process chamber and treating the substrate with plasma to densify the deposited sublayer, wherein densifying the deposited sublayer comprises flowing a process gas selected from the group consisting of Ar, He, H 2 , and mixtures thereof and forming a dual frequency plasma, wherein LF/HF power ratio is at least about 1.5; and
(d) repeating (a)-(c) to form and densify additional sublayers of silicon carbide.
2. The method of claim 1 , wherein the film has a stress of between about −300 MPa and 300 MPa.
3. The method of claim 1 , wherein the film has a stress of between about 0 MPa and 600 MPa.
4. The method of claim 1 , wherein the film has a hardness of at least about 16 GPa.
5. The method of claim 1 , wherein the film has a modulus of at least about 100 GPa.
6. The method of claim 1 , wherein the process gas used during deposition further comprises a carrier gas selected from the group consisting of He, Ne, Ar, Kr, and Xe.
7. The method of claim 1 , wherein the thickness of each sublayer is less than about 100 Å.
8. The method of claim 7 , wherein the method comprises depositing at least 10 sublayers.
9. The method of claim 1 , wherein in the formed silicon carbide film the ratio of areas of SiC peak in the IR spectrum relative to SiH is at least about 20 and the ratio of areas of SiC peak in the IR spectrum relative to CH is at least about 50.
10. The method of claim 1 , wherein the formed silicon carbide film has a density of at least about 2 g/cm 3 .
11. The method of claim 1 , wherein the formed hardmask layer is deposited over a layer of dielectric having a dielectric constant of less than about 2.8, and wherein the formed hardmask film has an etch selectivity of at least about 8:1 versus the dielectric in a dry plasma etch.
12. The method of claim 1 , wherein the formed hardmask layer is deposited over a layer of polysilicon.
13. The method of claim 1 , wherein the hardmask is formed at a temperature of less than about 400° C.