Research on Slicing Mechanism and Constant Wire Wear Loss Process of Multi-wire Sawing for Mono-crystalline Silicon Wafers Used for Integrated Circuit

Author:Li Zhen

Supervisor:wang min jie


Degree Year:2019





Integrated circuit(IC)is the cornerstone of modern information society.Its manufacturing capability and level determine the strength and level of a country’s industry.In its manufacturing process,slicing process is an important step in the production of mono-crystalline wafers.At present,multi-wire sawing technology has become the mainstream way of slicing due to its better processing efficiency,higher yield and the easiness of adapting to the trend of large diameters.In production,there are some problems in the slicing process,such as unstable slicing quality and high incidence of wire breakage because the material removal mechanism is not completely understood and the process is truly complex.Therefore,how to improve the processing quality and reliability of the working process becomes an urgent technological problem to be solved.This doctoral dissertation,based on the study of the mechanism of free abrasive multi-wire sawing,abrasion and strength distribution of saw wire,feedback rate of wire and so on,focuses on the constant wire wear loss process and the ways to assess the reliability of wire net.A brief introduction is given below.1、Through analysis of the material removal process of multi-wire sawing with free abrasive,the wave-like removal feature of the materials is found.And a mechanism model for partition material removal of cutting zone is constructed with the combination of the difference of cutting conditions.Based on the model,the researcher analyzed the impact of differences in abrasive force,crack extension process,distribution of cutting fluid,temperature distribution,abrasion of saw wire of each area upon the slicing quality and the stability of cutting process.The hydraulic pressure of cutting fluid,temperature distribution and surface characteristics,obtained through experiments,verified the wave-like removal feature of the materials of cutting zone,the relevant analysis of cutting fluid pressure and the characteristics of temperature fields.And the methods for improving cutting quality,reducing wire wear damage,and enhancing the reliability of process are put forward.2、In the process of multi-wire sawing,the damage and wear loss of the wire weaken the wire strength and increase the risk of wire breakage.The damage depth and distribution of wire surface are evaluated by observing the surface morphology of wire samples with different wear loss.The cross section of wire with different wear loss are observed,and the wear law of the wire during continuous processing is summarized.The fracture strength of worn wire is studied experimentally,the fracture process of wire under different wear quantity is analyzed,and the distribution law of tension-displacement curve of the wire with different wear loss is discussed.At the same time,the fracture surface of the wire strength test sample is observed.Based on the fracture characteristics of steel wire with different wear loss,a theoretical model of the wire maximum safe wear loss is established and the calculation method is proposed.This method lays a theoretical foundation for the confirmation of reasonable wire wearing capacity and preventing the wire break incidents from happening.3、As for the problem that the wire wearing capacity of wire net varies with the sawing parameters and conditions,thus influencing the slicing quality,the idea and method of constant wire wear loss were proposed.The constaint wire wear loss model was established so as to deduce the respective calculating method.Due to this method analyzing the relations between different slicing conditions,parameters and feedback ratio of wire,a cutting experiment was conducted to testify the effectiveness of the constant wire wear loss process.This method has been popularized,and achieved good economic and social benefits.4、As to the problem of wire breakage in multi-wire sawing process,the assessment method for the reliability of wire net was established,based on the theory of reliability.Through the analysis of the breakage intensity of worn wire,the Weibull parameters of each sample were obtained and the evaluative method for the reliability of wire was constructed.Based on the assessment method of wire reliability and wire net discrete series model,the assessment method of reliability for wire net of multi-wire sawing was set up.Through analysis of the dynamic force of wire in cutting process,the cutting parameters,technological condition,and the dynamic reliability of wire net,the reliability of wire net can be evaluated in accordance with different processing condition and parameters,so as to provide theoretical foundation for setting a reasonable technical parameters and ensuring the reliability of the slicing process.