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Method for a chuck in a high-density plasma CVD chamber

IP.com Disclosure Number: IPCOM000042253D
Publication Date: 2005-Feb-03
Document File: 4 page(s) / 141K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for a chuck in a high-density plasma chemical vapor deposition (CVD) chamber. Benefits include improved functionality and improved performance.

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Method for a chuck in a high-density plasma CVD chamber

Disclosed is a method for a chuck in a high-density plasma chemical vapor deposition (CVD) chamber. Benefits include improved functionality and improved performance.

Background

      High-density plasma chemical vapor deposition (HDP-CVD) processing is used for dielectric gap filling for shallow trench isolation (STI) and interlayer dielectric (ILD) layers in 180-nm, 130-nm, and 90-nm technologies.  The process is expected to be continuously used in 65-nm and 45-nm technologies.

      Filling the structures at the wafer edge is difficult. STI and ILD gap fill is demonstrated to be more severe at 65 nm. This problem is expected to be even worse at 45 nm.

              Conventionally, edge gap filling is addressed by tuning other parameters, including increasing the plasma density, raising the wafer temperature, and lowering the deposition pressure. However, 65 nm is apparently the limit of this optimization. It is not functional for 45 nm technology.

      For higher plasma density, tool vendors have introduced higher power generation for their new tools. This approach has created temperature control and thermal budget management problems for the design and materials of the chamber. Additionally, power efficiency for inductive plasma is expected to eventually drop. Increasing the power does not continue to increase the plasma density.

      A high wafer temperature is confined by the device fabrication thermal budget. The conventional range is maximized and does not have expansion capability.

      For low-deposition pressure, tool vendors have upgraded the turbomolecular pump for the advanced gap-fill HDP tool sets. However, low pressure can cause arcing in HDP-CVD chambers.

      A typical HDP chamber consists of at least two radio frequency (RF) sources. One is inductively coupled, and the other is capacitively coupled to the plasma. The plasma density is controlled by the inductive RF. The physical bombardment of ions to the wafer (gap fill) is controlled by the capacitive RF. The wafer chuck is the powered electrode. All surrounding chamber walls or chuck bodies are grounded. Although the chuck is powered by an RF source, the frequency is too fast for ions to follow the instantaneous change of the electromagnetic field. Instead, the movement of ions follows a time-averaged electrostatic field. It accelerates the ions to bombard the wafer surface. In an ideal case, the ions bombard the wafer with a trajectory perpendicular to the wafer surface. This case occurs at or near the wafer center. However, at the wafer edge, the electrostatic field is distorted by the surrounding grounded chamber and chuck walls. The ions obliquely accelerate towards the wafer at the edge locations. As a result, the gap fill performance is compromised.

      The electrostatic field caused by the bias RF through a conventional chuck can be plotted. Only the horizontal chuck sur...