Semiconductor devices are manufactured on semiconductor
wafers through a number of thermal, chemical, and physical processes. One such
process is known as chemical mechanical planarization or polish (CMP). The CMP
process uses chemical reactions and mechanical polishing to remove excess
material. As the critical dimensions of the transistors built on the wafer die
have decreased in size, the importance of the CMP has increased. Manufacturers
must address a significant concern of particles contamination on semiconductor
wafers and integrated circuits.
The CMP process removes the excess material but leaves
behind surplus particles. These unwanted particles will cause defects, reducing
production yield. The particles stick to the surface of the semiconductor wafer
primarily by one of four methods: chemical bonds, nature of being suspended in
cleaning solution that remains on the wafer surface, Van Der Waals forces and
electrostatic forces. The Van Der Walls force works on particles that are 30nm
or less from the surface. Electrostatic forces are induced by charges on the
particles and the wafer surface and cause the particle to either adhere to the
semiconductor wafer or repel from the semiconductor wafer.
This invention modifies the shape of the abrasive particles
used in the CMP process. The result is a reduction in the strength of the Van
Der Waals force on the CMP particles. Also, by changing the pH of the slurry
containing the particles, the electrostatic forces can be reduced. Therefore the
particles are easier to remove from the semiconductor wafer surface. The
invention involves making improved abrasive particles used in the slurry
solutions for chemical mechanical polishing (CMP). Said particles are designed
to allow Van der Waals (VDW) forces to predominate at the surface to be polished
and electrostatic forces on other regions of the particle. By changing the ionic
strength and pH of post-polish rinsing solutions, electrostatic forces can be
reduced, hence making the removal of abrasive particles from the polished
surface considerably more effective.
Potential Applications
Benefits and Advantages
- Increased yield
- Lower die cost
- Cleaner wafers
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