Methods for fabricating integrated circuits utilizing silicon nitride layers

A method of fabricating an integrated circuit comprising the steps of:

• providing a semiconductor substrate comprising first and second semiconductor devices disposed thereon;
• depositing a first silicon nitride layer over the semiconductor substrate and over the first and second semiconductor device using a first deposition process, wherein the first deposition process is a plasma-enhance chemical vapor deposition (PECVD) process that comprises the steps of:
• generating a plasma with a power source during a first time interval, the plasma comprising reactive ionic and radical species of a silicon-providing gas and a nitrogen-providing gas, wherein the generating the plasma causes etching via sputtering of the first silicon nitride layer at an upper portion of the first silicon nitride layer over the semiconductor devices at a first rate, wherein the generating the plasma causes etching via sputtering of the first silicon nitride layer an a lower portion of the first silicon nitride layer over the semiconductor substrate at a second rate, the first rate being relatively faster than the second rate;
• and
• discontinuing generating the plasma during a second time interval immediately subsequent to the first time interval, wherein, during the second time interval, the first silicon nitride layer forms at a substantially equal rate at the upper portion of the first silicon nitride layer over the semiconductor devices and at the lower portion of the first silicon nitride layer over the semiconductor substrate, wherein operating the PECVD process over the plurality of cycles causes the first silicon nitride layer to form at a greater thickness at the lower portion of the first silicon nitride layer over the semiconductor substrate as compared to the upper portion of the first silicon nitride layer over the semiconductor devices,
• wherein the steps of generating the plasma and discontinuing generating the plasma are performed in a cyclic manner until the first silicon nitride layer is at least about 50 Å thick as measured from an upper surface of the first and second semiconductor;
• and
• depositing a second silicon nitride layer over the first silicon nitride layer and in direct and abutting contact with the first silicon nitride layer so as to form a continuous silicon nitride layer.

A method of fabricating an integrated circuit comprising the steps of:

• providing a semiconductor substrate comprising a semiconductor device disposed thereon;
• depositing a first silicon nitride layer over the semiconductor substrate and over the semiconductor device using a first deposition process, wherein the first deposition process is a plasma-enhance chemical vapor deposition (PECVD) process that comprises the steps of:
• generating a plasma by applying radio frequency power source to a mixture of silicon-providing gas and a nitrogen-providing gasses during a first time interval, the plasma comprising reactive ionic and radical species of the silicon-providing gas and the nitrogen-providing gas, wherein a flowrate of the silicon-providing gas is between about 150 standard cubic centimeters per minute (sccm) and about 250 sccm, and wherein a flowrate of the nitrogen-providing gas is between about 1500 sccm and about 2150 sccm, wherein the generating the plasma causes etching via sputtering of the first silicon nitride layer at an upper portion of the first silicon nitride layer over the semiconductor device at a first rate, wherein the generating the plasma causes etching via sputtering of the first silicon nitride layer an a lower portion of the first silicon nitride layer over the semiconductor substrate at a second rate, the first rate being relatively faster than the second rate;
• discontinuing generating the plasma by ceasing application of the radio frequency power source during a second time interval immediately subsequent to the first time interval, wherein, during the second time interval, the first silicon nitride layer forms at a substantially equal rate at the upper portion of the first silicon nitride layer over the semiconductor device and at the lower portion of the first silicon nitride layer over the semiconductor substrate, wherein operating the PECVD process over the plurality of cycles causes the first silicon nitride layer to form at a greater thickness at the lower portion of the first silicon nitride layer over the semiconductor substrate as compared to the upper portion of the first silicon nitride layer over the semiconductor device;
• generating a plasma by re-applying the radio frequency power source during a third time interval immediately subsequent to the second time interval,
• wherein the flowrate of the silicon-providing gas and the flowrate of the nitrogen-providing gas are both maintained constant during the first, second, and third time intervals;
• and
• depositing a second silicon nitride layer over the first silicon nitride layer and in direct and abutting contact with the first silicon nitride layer so as to form a continuous silicon nitride layer.