Improvement Of PMD Process For Lam HDP Machine

When the structure of the transistor device is completed,a layer of Pre-metal Dielectric(PMD)deposit is required before entering the post-section copper process.The uneven gate and source leakage zone on the surface of the transistor are filled and the surface is ground down,laying the foundation for leveling the post-section copper process.In the line width of 110nm/90 nm technical process,the High density plasma(HDP)Phosphorus silicon glass(PSG)process is often the PMD core making process.The HDP process itself has excellent porosity.PSG film is often used in PMD,mainly because the phosphorus in PSG has a certain function of attracting impurities,which can effectively control the impurity content of transistor devices and ensure the working range and stability of devices.But at the same time,many problems are brought by the process characteristics and the defect of equipment.In this paper,we focus on the problems generated by HDP PMD process: particles,fragmentation,thickness uniformity and phosphorus concentration range(the difference between the maximum and the minimum).Through studying the phenomenon of the defect itself and the formation mechanism,the experiment is designed and verified,and the process steps are optimized starting from the pre-coating,so as to solve the problem of particles generated during the process.The problem of phosphorus release was solved by adding PMD process.The problem of fragmentation is solved by optimizing the adsorption voltage,cooling time and electrostatic discharge about Electrostatic Chuck(ESC).Carefully analyze each step and details of the pre-cleaning,optimize the cleaning steps,and then change the position of Protective ESC(PEC)when the cavity is idle,effectively solving the problem of thickness uniformity and phosphorus concentration.What's more,solving these problems without any new interference ensures the reproducibility of the process and the stability of the product.With the solution of the technical problem,the operating time of the equipment increased from 75% to 85%,the production cost of each piece of the process decreased by 45%,and the product yield remained above 97%.