Influence of etching on the side wall of plasma cleaning equipment on devices

• Categories:Company Dynamics
• Author:plasma cleaning machine-surface treatment equipment-CRF plasma machine-Sing Fung Intelligent Manufacturing
• Origin:
• Time of issue:2020-12-12
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(Summary description)The width of offset side wall of plasma cleaning equipment has an important effect on device performance. The direct effect is that the source leakage resistor (RSD) under the sidewall is closely related to the width of the sidewall. When the channel resistance decreases greatly due to the reduction of the gate length, the parasitic resistance of the source leakage zone becomes an important part of the overall resistance of the device. Too narrow offset side wall will result in high overlapped capacitance and worsen short channel effect. Too wide offset side wall, will make the overlap capacitance is small, will cause the drive current drop. At the same time, the time delay decreases with the increase of the offset side wall width, but deteriorates after reaching a certain scale. Therefore, the width of the offset side wall should be carefully optimized to ensure the optimal device performance.   In the previous technology process of 90nm, the Capacity Coupled Plasma (CCP) medium etching machine was mainly used to etching the offset side wall. This kind of equipment belongs to the low density plasma equipment working under high pressure, and the etching uniformity and process stability are relatively poor. At the same time, due to the directivity of ion divergence, the consistency of sidewall Angle is difficult to control. Thus, the Inductively Coupled Plasma (ICP) high-density Plasma devices previously used for silicon etching are increasingly being used for silicon nitride side wall etching. Because the inductively coupled plasma device can work in the low pressure range, ion directivity is good, less scattering. At the same time, the gas retention time in the cavity is short and the etching uniformity is good. In addition, the cavity predeposition function is used in the etching process, that is, a thin film is deposited on the cavity before each chip is etched, and the thin film on the wall of the cavity is removed after etching. This ensures the consistency of the cavity environment and greatly improves the stability of etching process. Inductively coupled plasma cleaning equipment has better control over the shape of offset side wall.   The evenness of offset wall width of inductively coupled devices is much better than that of capacitive coupled devices. It is found that the difference of the width of the side wall of the inductively coupled etching equipment is much smaller than that of the capacitance-coupled etching equipment by evaluating the side wall with the difference of the width of the middle wall and the width of the bottom wall in the tem photographs. It can be seen that the etch uniformity and the control ability to the side wall shape of inductively coupled plasma cleaning equipment are far better than that of capacitive coupling equipment. It is because of good offset wall width uniformity and lateral wall shape control; This results in good transistor uniformity. This point can be clearly verified by the yield loss from the ring oscillator. The yield loss of the ring oscillator is greatly reduced by inductively coupled etching in plasma cleaning equipment, and the yield is greatly increased.   In the process of plasma cleaning equipment side wall etching, in addition to uniformity, Top Loss is also an important parameter of side wall etching. Less top height loss will affect the metallization thickness of polysilicon gate and increase the resistance value of metal gate. More top height loss will affect the protection of polysilicon pseudo-gate in the post-metal gate process.