Computer-aided design and analysis of circuits and semiconductor – Nanotechnology related integrated circuit design
Reexamination Certificate
2001-04-13
2002-10-15
Mai, Son (Department: 2818)
Computer-aided design and analysis of circuits and semiconductor
Nanotechnology related integrated circuit design
C716S030000, C716S030000
Reexamination Certificate
active
06467066
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATIONS
This application claims benefit of priority under 35 USC 119 to Japanese Patent Application No. P2000-112928 filed on Apr. 14, 2000, the entire contents of which are incorporated by refer herein.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a technique of two- or three-dimensionally simulating conditions for manufacturing a semiconductor device, and a method of manufacturing a semiconductor device based on data provided by the simulation. In particular, the present invention relates to a semiconductor device simulation method for handling changes in the geometries of silicide reactive areas, a simulator for achieving the simulation method, and a simulation program for specifying various functions achieved by the simulator.
2. Description of the Related Art
A self-aligned silicide (SALICIDE) process is a semiconductor processing technique to reduce the gate resistance and source/drain resistance of a semiconductor device. The SALICIDE process forms a silicide film on gate electrodes and source/drain diffusion layers in a self-aligning manner. The SALICIDE process employs, for example, cobalt (Co) and involves two step anneal. The first beat treatment uses a relatively low temperature to form a cobalt monosilicide film, i.e., a CoSi film between a Co film and a silicon (Si) material such as a silicon substrate. The second beat treatment uses a relatively high temperature to form a cobalt disilicide film, i.e., a CoSi
2
film on the Si material. In this way, the cobalt SALICIDE process forms two silicide films, i.e., CoSi and CoSi
2
films having different states and compositions on a silicon material.
A related art simulates the cobalt SALICIDE process by considering only the formation of CoSi
2
without paying attention to the formation of CoSi.
This type of related art is described in “Modeling of Local Reduction in TiSi
2
and CoSi
2
Growth Near Spacers in MOS Technologies: Influence of Mechanical Stress and Main Diffusing Species” by P. Fomara, A. Poncet et. al in IEDM, 1996, pp. 73-76.
FIG. 1
is a flowchart showing the related art of simulating the cobalt SALICIDE process.
Step S
51
determines whether or not a cobalt disilicide (CoSi
2
) film is in contact with the silicon (Si) material, and step S
52
determines whether or not the CoSi
2
film is in contact with the cobalt (Co) film. If the CoSi
2
film is in contact with both the Si material and Co film, step S
53
computes a diffusion equation of Co diffusing through CoSi
2
and geometry changing equations expressing the geometric changes of the Co film, CoSi
2
film, and Si material, and changes the geometries of the Co film, CoSi
2
film, and Si material accordingly.
Step S
54
increments time by &Dgr;t. Step S
55
determines whether or not a predetermined heat treatment time has passed. If not, the flow returns to step S
51
, and steps S
51
to S
53
are repeated at intervals of &Dgr;t. If step S
55
determines that the predetermined heat treatment time has passed, the simulation provides final element geometries.
As mentioned above, the actual SALICIDE process involves a first heat treatment of forming CoSi and a second heat treatment of forming CoSi
2
. However, the related art simulates only the formation of CoSi
2
based on one of the first and second heat treatments. CoSi and CoSi
2
are formed through different physical phenomena, and if the CoSi forming stage is ignored, silicide reactions will incorrectly be simulated. In particular, the related art involves inaccuracy when simulating silicide film thicknesses and element geometries in the SALICIDE process by using different heat treatment conditions.
The related art also involves inaccuracy when calculating interface movements caused by silicide reactions. This leads to inaccurate calculations of stress and point defects caused in a silicon material due to the interface movements.
BRIEF SUMMARY OF THE INVENTION
An object of the present invention is to provide a simulation method capable of correctly simulating silicide film thicknesses and element geometries, allowing the speedy selection of proper process parameters, reducing the numbers of prototypes and tests, shortening a development period, and improving development efficiency. Also provided are a simulator for executing the simulation method, a simulation program for realizing functions of the simulation method, and a semiconductor manufacturing method employing the simulation method.
In order to accomplish the objects, a first aspect of the present invention provides a simulation method comprising a first step of determining whether or not a silicide region (which may be in the form of a film and is made of a metal and silicon) is in contact with a silicon region (which is made of silicon) and a metal region (which may be in the form of a film and is made of this metal); a second step of determining, if the silicide region is in contact with the metal and silicon regions, the species diffusing through the silicide region according to a temperature heating the silicide, metal, and silicon regions and the composition of the silicide region; a third step of finding, if the species diffusing rough the silicide region is silicon, it's positional relationships among the metal, silicide, and silicon regions according to a first diffusion equation expressing diffusion of silicon through the silicide region and geometry changing equations expressing geometric changes of the metal, silicide, and silicon regions; and a fourth step of finding, if the species diffusing through the silicide region is the metal, positional relationships among the metal, silicide, and silicon regions according to a second diffusion equation expressing diffusion of the metal through the silicide region and geometry changing equations expressing geometric changes of the metal, silicide, and silicon regions.
The composition of the silicide region is expressed as M
y
Si
x
where x and y indicate a coupling state of metal M and silicon Si that form the silicide.
The first aspect of the present invention simulates the SALICIDE process by separately considering silicide reactions caused by first and second heat treatments. This reduces the number of process parameters, prototypes and tests, shortens the development period, and improves development efficiency.
A second aspect of the present invention provides a simulator having first means for determining whether or not a silicide region (which may be in the form of a film and is made of a metal and silicon) is in contact with a silicon region (which is made of silicon) and a metal region (which may be in the form of a film and is made of this metal); second means for determining, if the silicide region is in contact with the metal region and the silicon region, the species diffusing through the silicide region according to a temperature heating the silicide, metal and silicon regions and the composition of the silicide region; third means for finding, if the species diffusing through the silicide region is silicon, it's positional relationships among the silicide, metal, and silicon regions according to a first diffusion equation expressing diffusion of silicon through the silicide region and geometry changing equations expressing geometric changes of the silicide, metal, and silicon regions; and fourth means for finding, if the species diffusing through the silicide region is the metal, it's positional relationships among the silicide, metal, and silicon regions according to a second diffusion equation expressing the diffusion of the metal through the silicide region and geometry changing equations expressing geometric changes of the silicide, metal, and silicon regions.
The simulator of the second aspect accurately calculates silicide region thicknesses and element geometries, reduces the number of pros parameters, prototypes, and tests, shortens a development period, and increases development efficiency.
A third aspect of the present invention provides a simulation program having a first c
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Kabushiki Kaisha Toshiba
Mai Son
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