Thermal Management in Advanced Semiconductor Manufacturing: Double-Side Polishers as Core Equipment for Wafer Global Planarization
In advanced semiconductor manufacturing, double-side polishers serve as core equipment for achieving global wafer planarization. Their continuous processing under high pressure generates significant heat due to sustained friction and equipment operation, leading to internal temperature rise. Thermal stability directly determines the surface figure accuracy of polishing plates, equipment operational reliability, and ultimately affects wafer processing yield. This article systematically elaborates on the impact of temperature rise on process results and, combined with typical wafer morphology, illustrates quality issues caused by inadequate thermal management.
01 Thermal Challenges in Double-Side Polisher Operation
Double-side polishers perform double-sided wafer polishing through the relative motion of upper and lower polishing plates under stable pressure. During continuous processing, friction between plate surfaces and operation of core components such as motors and spindles generate substantial heat. If heat dissipation is not timely, internal equipment temperature will continue to rise.
Under conventional pressure (e.g., 250kg), relying on the equipment's own heat dissipation, internal temperature can be maintained at approximately 35°C. However, as processing pressure increases and continuous operation time extends, the risk of temperature rise significantly increases, posing a direct threat to equipment precision and stability.
02 Core Impacts of Temperature Rise: Precision Degradation and Operational Deterioration
Internal temperature rise in equipment triggers a series of chain reactions, primarily manifested in two major aspects:
Direct Impact: Mechanical Thermal Deformation Leading to Processing Precision Degradation
Various metal structural components (such as polishing plate support frames, plate surfaces) and sealing elements will undergo deformation due to thermal expansion, directly causing the flatness and parallelism of polishing plates to deviate from set values. This not only increases operating resistance but also reduces the uniformity and surface figure accuracy of wafer polishing.
Professional thermodynamic simulations can clearly show the temperature distribution and its impact on key components. As shown in the figure below, under high-load continuous operation conditions, heat accumulates inside the equipment, causing localized high temperatures and subsequently triggering structural deformation.
Figure 1: Double-Side Polisher Thermodynamic Steady-State Simulation
The specific impact of thermal deformation on processing precision is intuitively reflected in the displacement changes of polishing plates. Simulation comparative analysis shows that after considering thermal effects, the displacement and tilt of polishing plates will significantly increase, directly affecting the carrier trajectory and polishing consistency of wafers being processed.
Figure 2: Double-Side Polisher Thermodynamic Steady-State Simulation (with Temperature Consideration)
Indirect Impact: Operational Stability Entering a Vicious Cycle
Temperature rise causes lubrication effectiveness to decrease and friction coefficients to increase, thereby raising motor load rates. Increased load rates lead to higher motor current, generating more heat, forming a vicious cycle of "temperature rise - load increase - further temperature rise," which seriously threatens the long-term operational stability of the equipment.
03 From Equipment Issues to Wafer Defects: Typical Process Results Caused by Temperature Rise
The decline in equipment precision and operational deterioration mentioned above will directly transfer to the wafer surface, forming various observable defects.
Surface Figure Uniformity Deterioration and Regional Shifts
Thermal deformation of polishing plates causes uneven pressure distribution, leading to systematic shifts in material removal rates in specific wafer regions (such as edges or center), forming global surface figure problems like "edge slow polishing" or "center over-polishing," severely affecting planarization results.
Increased Surface Roughness and Microscopic Damage
Temperature fluctuations affect the physical state of polishing pads, potentially causing surface roughness (Ra) to exceed specifications, and even generating dense microscopic scratches, posing risks to subsequent lithography and other processes.
Loss of Intra-Wafer and Inter-Wafer Consistency
Under the "temperature rise - load" vicious cycle, process conditions continuously drift, causing the removal rate differences between different regions within the same wafer to expand, while key parameters (such as film thickness) repeatability between wafers in batch production deteriorates, leading to significant yield fluctuations.
1. Siplus achieves perfect convex profiles and stably controls TTV around 1μm.
2. For applications requiring original surface figure preservation, we can highly replicate incoming material surface figures and optimize TTV to <1μm.
The realization of the above high-precision processing fundamentally relies on Siplus's double-side polisher's comprehensive and precise lower plate temperature control system, which provides critical assurance for process stability.
04 Thermal Control Strategy
To suppress temperature rise and ensure process stability, thermal management must be implemented at the system level. In engineering practice, air cooling, critical component liquid cooling, or combined strategies are typically adopted based on actual heat dissipation requirements and cost-effectiveness. Effective thermal control is a prerequisite for breaking the aforementioned vicious cycle and ensuring equipment precision and process result consistency.
Summary
The thermal stability of double-side polishers in high-pressure processing directly relates to equipment precision and wafer quality. Temperature rise causes equipment thermal deformation and operational vicious cycles, ultimately leading to wafer surface non-uniformity, excessive roughness, and other defects.
As advanced processes like 3D NAND push flatness requirements to their limits, thermal management has evolved from an equipment engineering issue to a core process control element affecting chip performance. This requires equipment and process engineers to collaborate, ensuring manufacturing yield through precise thermal design, monitoring, and control.