3DI Through-Silicon Via Hybrid Fill
Publication Date: 2014-May-02
The IP.com Prior Art Database
Disclosed is a method to fill a Through-Silicon-Via (TSV) while keeping reasonable wafer bow. The method uses both insulation fill and metal fill, which comprises two processes to fill the TSV.
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Approaches are needed to completely fill a Through -Silicon-Via (TSV) while keeping reasonable wafer bow.
The solution demonstrates approaches to fill TSV with low stress , low bow, while good conformity.
Due to the high aspect ratio of 3D interconnect (3DI) TSV, filling TSV is a major issue for 3DI consequent processes. In the TSV process, thermal oxide is used as isolation material due to its good conformity. Tungsten (W) is used as the metallic material due to its ability to fill deep trench.
However, TSV has a huge feature size (1um~10um); moreover, TSV is not an ideal vertical shape, and the mouth-like opening is often observed on top of TSV . The amount of W needed to seal the top TSV is much larger than that needed to fill the bottom TSV. Overall, in order to seal 3DI TSV, a W film of thickness of at least 1um is needed.
However, W is a high stress material; therefore, wafer bow limits the maximum amount of W can be deposited onto wafer for TSV fill . The maximum W thickness is about
0.4um, which increases the wafer bow 300um in tensile direction for 300mm wafers.
It is desirable to have a process that can completely fill the TSV while keeping a reasonable wafer bow.
The solution comprises:
• Insulation fill: Thermal Oxide + High Density Plasma (HDP) hybrid fill. HDP is combined with thermal oxide to alter the shape of TSV in order to close the top TSV mouth.
• Metal fill:
- 2X W process: W fill->W CMP->W fill-> W Chemical M...