Study On The Cleaning Process After CMP Of Aluminum Gate

With the development of integrated circuit technology,the characteristic size of the device is reduced to 45nm.The traditional structure of SiO2 medium/polysilicon gate is gradually replaced by a new structure named high K medium/metal gate.Aluminum is the most common gate metal material in CMOS devices.As the aluminum gate device has a high degree of integration,a bit of pollution about trace impurities or surface scratches can affect device performance seriously.Chemical mechanical polishing(CMP)is the only technology to achieve global flattening at present.With the further reduction of device size,some issues such as polishing process and residue of polishing liquid make the surface roughness of aluminum gate becomes larger and cause device noise.Which could have a great harm to the stability of the device.One of the most serious problem is the residue of silica sol particles in the polishing process.Therefore,it is very important to study the cleaning process after CMP of aluminum gate.The mechanism of adsorption about colloidal silica particles is studied through experiment in this paper.And the desorption principle of particles is explored basing on the experiment.A new type of cleaning solution named FA/O is developed whose main composition is chelating agent and active agent.Chelating agent can not only chelate metal ions,but also remove colloidal silica particles.It cause non-uniform corrosion as well.The active agent could lift speed of the removal about silica particles with high permeability.And it could suppress the non-uniform corrosion caused by chelating agent at the same time.A series of single-factor experiments is carried out by changing the volume fraction of chelating agent and active agent.It can achieve the best cleaning level when the volume fraction of FA/OII chelating agent is about 0.015%,and the volume fraction of O-20 active agent is about 0.15%.Two kinds of water-based cleaning process is studied basing on the new cleaning solution:PVA scrub by hand and polishing replaced by cleaning.The experimental results show that the effect of polishing cleaning is better than PVA scrub by hand.When the rotate speed is 55/55r/min,the pressure is 103/103madN/cm~2,and the rate of flow is 200ml/min,the best surface roughness is 3.12nm which washed by polishing cleaning process.Ultrasonic cleaning experiment is carried out after the polishing cleaning process,and a series of single-factor experiment is carried out to find the best process parameters.It is concluded that the most suitable ultrasonic cleaning parameters for aluminum gate after CMP is 40?of temperature,2 kw of power,5 min of cleaning time.The lowest surface roughness is 2.04nm when the cleaning process is carried out by polishing replaced by cleaning and ultrasonic cleaning,the particles on the surface is almost removed as well.