In semiconductor wafer manufacturing, grinding is a fundamental yet critical process. From backside thinning after slicing silicon ingots to removing surface damage layers from substrate materials, every instance of material removal and thickness control relies on a class of easily overlooked yet essential ceramic components-ceramic grinding plates. They may not command the spotlight like lithography machines, nor are they as well-known as etchers, yet they serve as the core platform that carries wafers during grinding. Their precision, stability, and cleanliness directly determine the machining quality and final yield of the wafers.
I. Why Do Grinding Plates Need to Be "Ceramified"?
The core tasks of the grinding process are: removing saw marks and damage layers from the sliced wafer surface, controlling wafer thickness uniformity, and repairing deformation caused by cutting. As chip process nodes continue to shrink, the requirements for wafer surface flatness have entered the nanometer range; simultaneously, the industry-wide transition from 8-inch to 12-inch wafers has significantly increased processing difficulty.
Traditional grinding plates are mostly made of cast iron or metallic materials. During the grinding process, they are prone to releasing free metal ions, causing surface contamination of the wafers. Moreover, metal plates have high wear rates and poor precision retention, making them incapable of meeting the ultra-precision machining requirements of large-diameter wafers. Compared to metallic grinding plates, ceramic grinding plates offer significant advantages:
01 Ultra-high Hardness and Wear Resistance
The hardness of ceramics far exceeds that of traditional metallic materials. This high hardness ensures extremely low plate surface loss during prolonged operation, allowing the plate to stably maintain its surface condition and machining precision, effectively extending the replacement cycle of consumables.
02 No Free Metal Ion Contamination
High-purity alumina, silicon nitride, and other ceramics are based on oxide or nitride matrices. During the grinding process, they do not release free metal ions, effectively avoiding wafer contamination issues associated with metal plates. This not only simplifies subsequent cleaning steps but also contributes to improved product yield.
03 Excellent Thermal Dimensional Stability
Grinding operations generate considerable frictional heat. Ceramic materials have low coefficients of thermal expansion and high elastic moduli, making them resistant to thermal deformation under high-speed grinding conditions. They can maintain high plate flatness over extended periods, ensuring wafer thickness uniformity.
04 Enables Extremely High Machining Flatness
Leveraging the high rigidity of ceramic materials and advanced precision machining technologies, the flatness of high-end ceramic grinding plates can be controlled at the micron or even sub-micron level-a crucial guarantee for achieving excellent surface planarity after wafer thinning.
II. Main Ceramic Materials for Grinding Plates and Their Application Scenarios
Different grinding conditions (wafer size, substrate material, machining precision, etc.) impose varying requirements on grinding plate materials. Currently, four types of ceramic materials are predominantly used in the semiconductor field:
01 Alumina Ceramics
Offering balanced overall performance and controllable cost, alumina is the most widely used grinding plate material, mainly suited for rough and fine grinding processes on most 8-inch and smaller silicon wafers. Its Vickers hardness is approximately 15–18 GPa, flexural strength 300–450 MPa, and coefficient of thermal expansion about 7×10⁻⁶/K.
02 Silicon Nitride Ceramics
With flexural strength reaching 700–1000 MPa and fracture toughness of 6–8 MPa·m¹/², silicon nitride is resistant to crack propagation under stress and exhibits excellent wear resistance. Its coefficient of thermal expansion, approximately 3.5×10⁻⁶/K, closely matches that of silicon wafers, making it especially suitable for precision thinning of 12-inch large-diameter silicon wafers, as well as hard grinding processes for third-generation semiconductor substrates such as silicon carbide and gallium nitride.
03 Zirconia Ceramics
With fracture toughness reaching 7–10 MPa·m¹/² and excellent chemical stability, zirconia has slightly lower hardness than alumina and silicon carbide. It is commonly used in auxiliary components such as retaining rings and pressure rings within grinding equipment. These components are in prolonged contact with grinding slurry and may be subjected to impact; zirconia's high toughness and chemical stability effectively prevent fracturing and avoid wafer contamination.
04 Silicon Carbide Ceramics
Among the four materials, silicon carbide has the highest hardness, with a Vickers hardness of 23–28 GPa and outstanding wear resistance. Its coefficient of thermal expansion is approximately 4×10⁻⁶/K, essentially matching that of silicon wafers, ensuring no thermal mismatch stress during high-speed grinding, making it the material of choice for high-speed grinding applications. In self-grinding processes for silicon carbide substrates, grinding plates of the same material offer hardness matching and chemical compatibility that avoid contamination risks potentially introduced by dissimilar materials, providing unique process compatibility.
III. Core Technical Challenges
In practical applications, ceramic grinding plates often feature structures such as vacuum suction holes, grooves, and positioning steps, which demand extremely high machining precision. Their manufacturing involves multiple core technical bottlenecks:
01 Uniformity Control for Large Diameters
Grinding plates for 12-inch wafers typically exceed 300 mm in diameter, with some specifications reaching 800 mm. During forming and high-temperature sintering, ceramic powder compacts experience non-uniform shrinkage across different regions, leading to warpage, deformation, or even cracking. Current mainstream solutions include: using cold isostatic pressing to obtain high-density uniform compacts (which apply pressure uniformly from all directions to avoid density gradients that cause differential shrinkage), combined with segmented temperature-controlled sintering and the introduction of sintering aids to promote uniform grain growth.
02 Ultra-Precision Machining
The flatness, parallelism, and surface roughness of grinding plates directly determine wafer machining quality. Given the high hardness of ceramics, specialized super-abrasive tools and precision machine tools are required to control flatness at the micron or sub-micron level. The general processing flow is: rough grinding → fine grinding → lapping → polishing, with core equipment including high-precision surface grinders and double-side lapping/polishing machines.
03 Material Purity Control
Trace metallic impurities can transfer to the wafer surface during grinding, causing defects. Powder purity is generally required to be above 99.99%. The sintering process uses high-purity crucibles, the machining stage employs diamond tools and deionized water coolant, and metal residue on the plate surface is regularly inspected.
In addition to manufacturing processes, proper maintenance during actual use of ceramic grinding plates is equally critical. After prolonged operation, plates are prone to surface glazing and groove clogging. According to industry experience, regular dressing of the plate surface with diamond dressers, combined with high-pressure deionized water or ultrasonic cleaning of grooves, can extend the service life of ceramic plates by 30%–50%.