How does CMP Technology Reshape the Landscape of Chip Manufacturing

Over the past few years, the center stage of packaging technology has gradually been ceded to a seemingly "old technology" - CMP (Chemical Mechanical Polishing). When Hybrid Bonding becomes the leading role of the new generation of advanced packaging, CMP is gradually moving from behind the scenes to the spotlight.

This is not a resurgence of technology, but a return to industrial logic: behind every generational leap, there is a collective evolution of detailed capabilities. And CMP is that most understated yet extremely crucial "King of Details".

From traditional flattening to key processes

The existence of CMP has never been for "innovation" from the very beginning, but for "solving problems".

Do you still remember the multi-metal interconnection structures during the 0.8μm, 0.5μm, and 0.35μm node periods? Back then, the complexity of chip design was far less than it is today. But even for the most basic interconnection layer, without the surface planarization brought by CMP, insufficient depth of focus for photolithography, uneven etching thickness, and failed interlayer connections would all be fatal problems.

Entering the post-Moore's Law era, we no longer merely pursue the reduction of chip size, but pay more attention to the stacking and integration at the system level. Hybrid Bonding, 3D DRAM, CUA (CMOS under array), COA (CMOS over array)... More and more complex three-dimensional structures have made a "smooth interface" no longer an ideal but a necessity.

However, CMP is no longer a simple planarization step; it has become a decisive factor for the success or failure of the manufacturing process.

Hybrid Bonding is essentially a metal-metal + dielectric layer bonding process at the interface level. It seems like a "fit", but in fact, it is one of the most demanding coupling points in the entire advanced packaging industry route:

• The surface roughness must not exceed 0.2nm
• Copper Dishing must be controlled within 5nm (especially in the scenario of low-temperature annealing)
• The size, distribution density and geometric morphology of Cu pad directly affect the cavity rate and yield
• Wafer stress, Bow, Warpage, and thickness non-uniformity will all be magnified as "fatal variables"
• The generation of oxide layers and Void during the Annealing process must also rely on the "pre-buried controllability" of CMP in advance.

And the CMP here takes on the role of the closing move before the "grand finale move"

Whether the surface is flat enough, whether the copper is bright enough and whether the roughness is small enough determine the "starting line" of all subsequent packaging processes.

Process challenges: Not just uniformity, but also "predictability"

From the solution path of Applied Materials, the challenges of CMP go far beyond uniformity:

• Lot-to-Lot (Between batches)
• Wafer-to-Wafer (between wafers
• Within Wafer
• Within Die

Meanwhile, as the process nodes advance, every indicator of Rs (sheet resistance) control, dishing/recess accuracy, and roughness Ra is required to be at the "nanometer level" precision. This is no longer a problem that can be solved by device parameter adjustment, but rather system-level collaborative control:

• CMP has evolved from a single-point device process to a system-level action that requires perception, feedback, and closed-loop control.
• From the RTPC-XE real-time monitoring system to the Multi-Zone Head partition pressure control, from the Slurry formula to the Pad compression ratio, every variable can be precisely modeled just to achieve one goal: to make the surface "uniform and controllable" like a mirror.

The "Black Swan" of Metal Interconnections: Opportunities and Challenges for Small Copper Particles

Another little-known detail is that Small Grain Cu is becoming an important material path for low-temperature Hybrid Bonding.

Why? Because small-grained copper is more likely to form reliable Cu-Cu connections at low temperatures.

However, the problem is that small-grained copper is more prone to Dishing during the CMP process, which directly leads to a contraction of the process window and a sharp increase in the difficulty of process control. Solution? Only a more precise CMP parameter modeling and feedback control system can ensure that the polishing curves under different Cu morphology conditions are predictable and adjustable.

This is not a single-point process challenge, but a challenge to the capabilities of the process platform.

Vetek company specializes in production CMP polishing slurry ,Its core function is to achieve fine flatness and polishing of the material surface under the synergistic effect of chemical corrosion and mechanical grinding to meet the flatness and surface quality requirements at the nano level.