Introduction to GSS-TechSim


GSS-TechSim is built on the base of GSS 0.46-p11 for the purpose of two-demensional semiconductor process simulation. Following is a quite simple introduction to the basic functions of GSS-TechSim. More detailed information is avaiable at GSS-TechSim User's Guide (Chinese) and GSS-TechSim input card description.

GSS 0.47 is integrated with GSS-TechSim and it can be used for the simulation of:

1.Thermal Diffusion
2.Thermal Oxidation
3.Ion Implantation
4.High-k Material

Fig.A and Fig.B are VDMOS and Parasitic MOS in LOCOS simulated by GSS-0.47 with TechSim.


Fig.B Parasitic MOS

Thermal Diffusion

GSS 0.47 can take the advantage of analytical solution and numerical differetial equation solution for solving the diffusion equation. Fig.1 demonstrates the doping profile of As at 1200 C for 20 min, where the left one is calculated by analytical solution and the right one by numerical solution. The probe of doping concentration in the center of the well is shown in Fig.2 (where DIFF indicated analytical solution and ODE indicated numerical solution)

Fig.1 Doping profile of thermal diffusion

Fig.2 Doping probe in the center of n well

Another important feature of GSS-TechSim is its ability in solving diffusion equation where the diffusion constant is related to the carrier density in the substrate. For instance, in As doped n-type region, B ion diffuse slower than in intrinsic region. This would result in a kink of B doping profile in As stepped doping substrate. As demonstrated in Fig.3 and Fig.4.

Fig.3 Doping profile of B in substrate where As pre-doped in step manner

Fig.4 Doping probe of B ion

Thermal Oxidation

GSS-TechSim uses Deal-Grove model for predicting the thickness of oxidation layer in different reaction condition. It also includes models for predicting the shape of the bird's beak (Fig.5 and Fig.6). GSS-TechSim support multipule masking(Fig.7).

Fig.5 Bird's beak with shape 1

Fig.6 Bird's beak with shape 2

Fig.7 Multiple masking

Ion Implantation

Ion implantation mainly follows LSS theory and more accurate Monte Carlo method is planned to be introduced in. Fig.8 and Fig.9 is an example result of ion implantation simulation (B, 80 keV, 1e15#/cm^2).

Fig.8 Ion implantation profile

Fig.9 Ion implantation probe

High-k Material

High-k material normally refers to materials with dielectric constant larger than 12, often between 25 and 30 (as there is a trade off between the energy gap and dielectric coefficent).TechSim added three High-k material into the material library: HfO2,ZrO2 and SrTiO3. Fig.10 shows a tft with HfO2 as gate spacer.

Fig.10 TFT with HfO2 as gate spacer

GSS: open source TCAD software.