8.26 Sspd_chapter 6_part 7_introduction to athena 7_process simulator

SSPD_Chapter 6_Part 7_Introduction to ATHENA 7_Process Simulator

7.7 Background of ATHENA.

7.7.9 Simulating the Epitaxy Process.

ATHENA/SSUPREM4 can simulate a high temperature silicon epitaxial processes. The epitaxy process is considered as a combination of deposit and diffuse processes. Therefore, processes such as autodoping from a highly doped buried layer into a lightly doped epitaxial layer can be simulated. Diffusion parameters for epitaxial silicon, however, are considered the same as for single crystal silicon.

The epitaxy process is defined in the ATHENA Epitaxy Menu (Figure 7-39). To open this menu, select Process→Epitaxy in the Commands menu. The ATHENA Epitaxy Menu consists of five sections:

• The Time/temperature section selects temperature step parameters in the same way as in the DIFFUSE statement.

• The Thickness/rate section selects either the total thickness of the epitaxial layer, or the deposit rate in microns/minute. In the latter case, the total thickness will be determined by the rate and time.

• The Grid Specification section specifies the vertical grid structure within the grown epitaxial layer. All grid parameters are equivalent to those of the ATHENA Deposit Menu

• The Ambient section is where the gas pressure can be modified to the value used in the Epitaxial Chamber.

• The Impurity Concentrations section specifies the growing epitaxial layer in the same way as in the DIFFUSE statement.

All parameters in the last three groups are optional. If the parameters of an epitaxial step are set exactly as shown in Figure 7.39, the following statement will appear in the input file:

# EPI-LAYER

EPITAXY TIME=30 TEMP=900 T.FINAL=1000 THICKNESS=5 DIVISIONS=20 \ DY=0.05 YDY=0.00

Note: The diffusion during the epitaxy process will use the Diffusion Model Set in the most recent METHOD statement. If you need another METHOD statement, include it before the EPITAXY statement.

Figure 7.39. ATHENA Epitaxy Menu