Elite 2D Typography Advanced 2D Deposition and Etch Simulator - PowerPoint PPT Presentation

Elite 2D Typography Advanced 2D Deposition and Etch Simulator

Introduction  Elite is an advanced 2-D topography simulator for modeling physical etch, deposition, reflow and CMP planarization processes for modern IC technologies  Elite provides physics-based, easy to use, and extensible platform and seamless integrates with SSuprem4 and  Optolith process simulators within the ATHENA framework - 2 - Elite

Key Benefits  Predicts the topology evolution during complex processes  Provides effective alternative for solving processes with aggressive topographical design rules  Accurately simulate of critical process issues such as step coverage, voids, microstructure cracks, etc  Seamless interface with layout editor MaskViews  CMP and reflow models provide capabilities to analyze critical planarization processes  Additional MC Deposit/Etch module provides several accurate Monte Carlo based models  Seamless integrates with SSuprem4 - 3 - Elite

Application Examples  Multi-Level Interconnect  Metal Step Coverage After Reflow  Inter-metal Dielectric Void Formation  Chemical Mechanical Polish  Microlaoding Effect - 4 - Elite

Multi-Level Interconnect  Accurate descriptions of multilevel interconnect structures can be simulated with Elite  Capability to evaluate the tightly spaced interconnect lines and dielectric film uniformity of complicated interconnect structures  The interface with SSuprem4 allows doping and oxidation profiles to be included in the structure - 5 - Elite

Metal Step Coverage After Reflow  Ability of Elite to model metal step coverage in a contact via after reflow  Topographical descriptions such as this are useful for analyzing and avoiding failure mechanisms during multi-level deposits and patterning steps  The final structure can be evaluated in ATLAS - 6 - Elite

Inter-Metal Dielectric Void Formation  Elite can optimize a process to avoid formation of superfluous voids during deposition  Use of two conductors (poly and aluminum) that come close together  The narrow gap between them can form a void as demonstrated in this example  The type of inter-metal dielectric material, the thickness of this dielectric, the method of insulation as well as design rules may affect integrity of multi-level metalization - 7 - Elite

Chemical Mechanical Polish  Elite includes a module for evaluating effects of CMP processes  Resulting surface evolution during a CMP of an inter-metal dielectric layer - 8 - Elite

Microlaoding Effect  The etch models in Elite incorporate advanced physical effects such as micro-loading  Variation in trench depth with mask window size - 9 - Elite

Elite Models  Topography processes are modeled by  Defining a machine in the RATE.DEPO or RATE.ETCH statement  Running the machine for a specified period of time  Wet (Isotropic) Etching  WET and ISOTROPIC parameters in the RATE.ETCH statement  Reactive Ion Etching (RIE)  RIE flag and combination of ISOTROPIC, DIRECTIONAL, CHEMICAL and DIVERGENCE parameters in the RATE.ETCH Statements - 10 - Elite

Elite Models (con’t)  Deposition with different geometry of material sources  Unidirectional, Dual Directional, Hemispheric, Planetary, Conical  ANGLE1[ANGLE,ANGLE3], DEP.RATE, SIGMA.DEP parameters  Chemical Vapor Deposition (CVD)  CVD and STEP.COV parameters in the RATE.DEPO statement - 11 - Elite

Elite Models (con’t)  Monte Carlo Deposition  To estimate step coverage and film density  MONTE1/2, ANGLE, SIGMA.DEP, Sticking Coeff. Parameters  Chemical Mechanical Polishing (CMP)  Parameters in the RATE.POLISH statement  REFLOW of glassy silica (oxide, BPSG,etc.)  Takes place simultaneously with impurity diffusion  When REFLOW flag set on the DIFFUSE and MATERIAL statements - 12 - Elite

Interaction of String and Gridding Algorithms  In Elite, exposed surface is considered as a string of joined points  During etching or deposition each point of the string advances  New positions of each point are defined by local etch/deposition rate  In contrast to other topography simulators, Elite links the string with a simulation grid - 13 - Elite

Interaction of String and Gridding Algorithms (con’t)  During etching, the string cuts through into the grid  Special regridding algorithm is applied to the area under new surface  During deposition, the string advances outside the simulation grid  Special gridding algorithm is applied to cover newly deposited area - 14 - Elite

Complex Trench Formation Example  Some of discussed Elite capabilities are demonstrated in the following example  The example consists of a complex process sequence in order to show that ATHENA allows to easy transition from in wafer to topography processes and back  Demonstration is focused on Elite/SSuprem4 interface and on gridding issues - 15 - Elite

Complex Trench Formation Example (con’t)  First, an oxide/nitride/oxide stack is formed by oxidation and conformal deposition  Then the stack is patterned using simplified mask process (see figure on page 17)  After that a nitride spacer is formed by combination of  conformal deposition and etch-back using RIE (see figure on page 18)  ISOTROP and DIRECT parameters are used to control shape and width of the spacer - 16 - Elite

Patterned Structure  Stack is patterned using simplified mask process - 17 - Elite

Spacer Structure  Nitride spacer is formed by combination of conformal deposition and etch-back using RIE - 18 - Elite

Complex Trench Formation Example (con’t)  The thick spacer is used to reduce length of LOCOS with short Bird’s Beak  Viscous stress-dependent oxidation gives accurate LOCOS  (see Figure on page 22)  The grown LOCOS serves as a mask for subsequent Trench etching  So far a very coarse grid in substrate was used. This saved a lot of simulation time.  Much finer grid is needed for trench formation and doping. This is achieved by DevEdit remeshing (see Figure on page 21) - 19 - Elite

LOCOS Structure  Viscous stress-dependent oxidation gives accurate LOCOS - 20 - Elite

Grid After DevEdit  Much finer grid is needed for trench formation and doping - 21 - Elite

Complex Trench Formation Example (con’t)  Next step opens a window for subsequent trench etching  It uses a selective nitride etching simulated by RIE model with high directional etch rate for nitride (see Figure on page 23)  Deep trench is formed using high directional component of silicon etch rate (see Figure on page 24)  Tuning of the trench shape could be done by varying isotropic rate - 22 - Elite

After Selecting Etching of Nitride Plug  Much Selective nitride etching simulated by RIE model with high directional etch rate for nitride - 23 - Elite

Structure After Trench Etching  Much Deep trench is formed using high directional component of silicon etch rate - 24 - Elite

Complex Trench Formation Example (con’t)  Next step is to dope walls and bottom of the trench  It is done by CVD deposition of phosphorus doped poly-layer and subsequent diffusion (see Figure on page 26).  It should be mentioned that substrate is not doped because  thin oxide layer is left after trench etching  Then polysilicon is etched completely (see Figure on page 27) - 25 - Elite

Structure After Trench Doping  Dope walls and bottom of the trench by CVD deposition - 26 - Elite

Structure After Polysilicon Removal  Polysilicon is etched completely - 27 - Elite

Complex Trench Formation Example (con’t)  However, some residual polysilicon islands could remain after etching  Slight reoxidation is used to consume these residuals (See Figure on page 28)  After that the trench is filled using oxide CVD deposition residuals (See Figure on page 28)  A void could be formed in the process. Next release of  ATHENA will predict formation of such voids - 28 - Elite

Structure After Trench Reoxidation  Slight reoxidation is used to consume residual polysilicon - 29 - Elite

Structure After Trench Filling  Trench is filled using oxide CVD deposition - 30 - Elite

Complex Trench Formation Example (con’t)  After the trench is filled the outer oxide surface is always non- planar  There are several methods of surface planarization  One of them is viscous reflow which removes the step formed previously (see Figure on page 32)  Impurity redistribution takes place simultaneously with reflow  The final step of the process etches all excessive material layers and leaves only filled trench (see Figure on page 32) - 31 - Elite

Structure After Oxide Reflow  The final step etches all excessive material layers - 32 - Elite

Structure After Final Planarization  The final step etches all excessive material layers - 33 - Elite

Conclusion  Elite is seamlessly integrated within the ATHENA framework with SSuprem4 and Optolith  Elite allows simulation of a wide variety of deposition and etching processes as well as material reflow and CMP characterization  Allows to analyze individual process steps and couples multilevel interconnect structure formation - 34 - Elite