Semiconductor devices with copper interconnects and composite silicon nitride capping layers
View Patent ↗Cu interconnects are formed with composite capping layers for reduced electromigration, improved adhesion between Cu and the capping layer, and reduced charge loss in associated non-volatile transistors. Embodiments include depositing a first relatively thin silicon nitride layer having a relatively high concentration of Si—H bonds on the upper surface of a layer of Cu for improved adhesion and reduced electromigration, and depositing a second relatively thick silicon nitride layer having a relatively low concentration of Si—H bonds on the first silicon nitride layer for reduced charge loss.
1. A method of fabricating a semiconductor device, the method comprising:
depositing a layer of copper (Cu);
depositing a first silicon nitride layer having a first Si—H concentration, on the layer of Cu at a first SiH 4 flow rate of about 120 to about 180 sccm, and a first total RF power of about 640 watts to about 960 watts; and
depositing the second silicon nitride layer having a second Si—H concentration at a second SiH 4 flow rate of about 14 to about 24 sccm and the second total RF power of about 1,280 watts to about 1,920 watts.
2. The method according to claim 1 , comprising depositing the second silicon nitride layer at the second Si—H concentration of about 0.02% to about 0.06%.
3. The method according to claim 2 , comprising depositing the first silicon nitride layer at the first Si—H concentration of about 0.30% to about 0.90%.
4. The method according to claim 3 , comprising:
depositing the first silicon nitride layer at a first thickness; and
depositing the second silicon nitride layer at a second thickness greater than the first thickness.
5. The method according to claim 1 , wherein the semiconductor device includes a mirrorbit device comprising an oxide/nitride/oxide (ONO) gate dielectric stack on a substrate and a gate electrode on the gate dielectric stack.
6. The method according to claim 1 , comprising depositing the silicon nitride layer as one graded film by;
modifying the Si—H concentration throughout deposition; or
modifying the Si—H concentration at various discreet points during deposition.
7. The method according to claim 1 , wherein
said first silicon nitride layer is deposited by plasma enhanced chemical vapor deposition (PECVD) using ammonia and SiH 4 ; and
said second silicon nitride layer is deposited by PECVD using nitrogen and SiH 4 .