AVS 50th International Symposium
    Plasma Science and Technology Monday Sessions
       Session PS-MoM

Paper PS-MoM4
Aspect Ratio Dependent Etching in the Si-Treatment Process of the Source and Drain Area of sub 90 nm Devices

Monday, November 3, 2003, 9:20 am, Room 315

Session: Critical Dimension Etching
Presenter: K.H. Bai, Samsung Electronics Co., Korea
Authors: K.H. Bai, Samsung Electronics Co., Korea
M.C. Kim, Samsung Electronics Co., Korea
B.Y. Nam, Samsung Electronics Co., Korea
K.K. Chi, Samsung Electronics Co., Korea
C.J. Kang, Samsung Electronics Co., Korea
W.S. Han, Samsung Electronics Co., Korea
J.T. Moon, Samsung Electronics Co., Korea
Correspondent: Click to Email
As feature dimension shrinks down to nano scale of sub 90 nm, the aspect ratio increases up to more than 10 even at the source/drain area of the self-aligned contact (SAC) sturcture of the DRAM devices. The small open areas of the contact holes for the sub 90 nm devices require enough Si-treatment at the source/drain area to get a reliable contact resistance. However, usually the low-biased etching condition of the soft etch plasma has severe aspect ratio dependent etching (ARDE) phenomena, leading a lot of Si3N4 loss at the shoulder of SAC sturcture. To overcome the severe ARDE in the high aspect ratio structure, we investigated the ratio of radical to ion flux at the top and bottom surface of the contact holes. Because the low bias of the soft etching condition, the radicals collide to the side wall surface multiple times before reaching the hole bottom. Therefore, the radical flux at the bottom of the hole is affected by the sticking coefficient controlled by the surface temperature. However, another important key factor controlling the ARDE is the radical density in the plasma. We found that the surface coverage of the contact hole is greater than 1, the temperature becomes a less important factor in controlling the ARDE. In this work, we investigated the ARDE of our Si-treating plasma in our sub 90 nm scale devices as functions of the radical density and temperature, finding a condition nearly free from ARDE. As a result, the loss of Si3N4 at the shoulder of the gate electrode was reduced by 70%, also improving contact resistances at the source/drain more than 10%.