Deep Dive into Low-Temperature Polysilicon Technology: TFT Display Core and Industrial Applications

Overview of Thin-Film Transistor Technology

In modern active-matrix display panels, the thin-film transistor (TFT) serves as the core driving component. The channel active region is primarily made of silicon material. Based on process and performance differences, TFTs are mainly classified into three types: amorphous silicon (a-Si), low-temperature polysilicon (LTPS), and high-temperature polysilicon (HTPS). Among these, low-temperature polysilicon (LTPS) technology has become the mainstream choice for 6th-generation and below production lines due to its excellent electron mobility, low power consumption, high resolution, and relatively simple manufacturing process.

In-Depth Analysis of LTPS-TFT Structure Design

As shown in Figure 1, a typical LDD (lightly doped drain) type LTPS-TFT structure consists primarily of a substrate and a buffer layer. The substrate is usually made of alkali-free display-grade optical glass, on which a buffer layer of silicon dioxide (SiO₂) or a double-layer SiO₂/SiNx structure is deposited. The key function of this buffer layer is to prevent metal ions from the glass from diffusing into the polysilicon active region, thereby suppressing defect formation and leakage current.

Compared with single-layer SiO₂, SiNx (silicon nitride) has a higher dielectric constant (SiO₂ ~4, SiNx 6–8), offering better breakdown resistance, barrier performance, and oxidation repair capability. Silicon nitride prepared by PE-CVD can have an oxygen content as high as approximately 10²² cm⁻³, ensuring device stability.

For the polycrystallization process, the amorphous silicon layer must be converted into a polysilicon layer. Common methods include solid-phase crystallization, metal-induced lateral crystallization (e.g., nickel-induced), and laser crystallization. Among these, laser crystallization achieves crystallization through instantaneous high-temperature melting, offering high efficiency and uniform grains. However, it should be noted that if a double-layer SiO₂/SiNx buffer structure is used, a hydrogen explosion phenomenon may occur during laser crystallization, leading to defects. Solutions include performing a dehydrogenation bake before laser crystallization, or using a single-layer SiO₂ structure with extremely low hydrogen content.

LDD technology involves low-dose ion implantation in the source/drain regions inside the gate, precisely controlling the doping concentration to form a concentration buffer zone with high series resistance. This effectively reduces the local electric field gradient, suppresses leakage current, and avoids the hot carrier effect.

Industrial Applications and Professional Display Solutions

As display technology evolves toward higher resolution, lower power consumption, and thinner form factors, LTPS-TFT has become a critical technological path for mid-to-high-end display panels. In practical product implementation, the overall design and manufacturing capability of display modules are equally important.

In this field, CNK (abbreviation for CNAOKE Electronics) is a specialized technology enterprise engaged in the development, production, and sales of display devices and HMI (human-machine interface) interactive products, recognized as a "Specialized, Refined, Distinctive, and Innovative" enterprise. Its main products include monochrome LCDs and monochrome modules, 0.96‑ to 15.6‑inch TFT display modules, OLED modules, and HMI interactive modules, widely used in industrial control, smart home, medical equipment, automotive displays, and many other fields.

Whether for basic display needs using LCD screens or high-performance solutions required by LCD display manufacturers, CNK provides customized, cost-effective solutions. Leveraging advanced production lines and a strict quality control system, CNK continues to deliver stable, core display components to its customers.

Conclusion

From core LTPS TFT technology to the integration and optimization of complete display modules, every advancement in the display industry relies on the synergy of materials, processes, and design capabilities. CNK will continue to deepen its presence in the display and human-machine interaction field, helping more end products achieve clearer and smarter display experiences.

About CNK
Founded in Shenzhen in 2010, CNK Electronics (CNK in brief) expanded the world leading factory in Longyan, Fujian in 2019. It is a national specialized and innovative "little giant" enterprise that specializes in the design, development, production and sales of display products. CNK provides customers with a full range of cost-effective small and medium-sized display modules, solutions, and services with excellent quality worldwide. Oriented in technology and high quality, CNK keeps sustainable development, works to offer customers  better and stable services.