JPH1012610A - Semiconductor process simulation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide semiconductor simulation capable of executing high accuracy simulation in a short time without requiring high knowledge concerning the simulation. SOLUTION: Semiconductor process simulation of a fabrication process of a semiconductor device including a semiconductor substrate having a junction includes a mesh formation step of determining position of the junction on the basis of one dimensional impurity concentration obtained by predetermined one dimensional simulation, and finely dividing meshes located in the vicinity of the junction and roughly dividing meshes other than the neighbourhood of the junction to form basic meshes, and an at least one calculation step of executing simulation of each fabrication process using set conditions of each fabrication process and each fabrication process model of a semiconductor device prepared beforehand on the basis of the base meshes.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a semiconductor process simulation method for simulating the structure of a semiconductor device by using modeled manufacturing steps and manufacturing conditions.

[0002]

2. Description of the Related Art In recent years, as the scale of integrated circuits has increased, the time and labor required from specification determination to design and manufacture in the development of integrated circuits has become enormous. In order to deal with this, in the domain of process, device, and circuit design, simulations using computers have been actively performed. The process simulation, which is one of these, is to obtain, using a computer, the impurity distribution and the device shape after each manufacturing process set under predetermined conditions. The ion implantation, oxidation, diffusion, epitaxial growth, and the like are modeled based on the physical and chemical properties of the substrate material and the like, and the simulation is performed using the set conditions of the process. In this process simulation, the actual calculation on the computer is
The semiconductor element structure is discretized by mesh division, and is executed based on the divided mesh.

In order to improve the calculation accuracy in the process simulation, it is only necessary to make the mesh to be divided finer, but there is a problem that the calculation time becomes longer with the finer size. In particular, when performing a two-dimensional or three-dimensional multidimensional simulation, the amount of calculation becomes enormous due to the refinement of the mesh, and it is actually impossible to perform the computation with the refinement of the mesh of all parts. Therefore, by executing a simple simulation in advance, for example, the bonding position and the Si / SiO ₂ interface position are obtained, and only the portion where the physical or stoichiometric amount to be calculated such as the position and the surface is large is divided into fine meshes. However, the division of the meshes of the other parts is roughened to reduce the amount of calculation and improve the calculation accuracy (hereinafter referred to as a first conventional example). Japanese Patent Application Laid-Open No. 5-114569 proposes a method of subdividing a mesh in accordance with an impurity concentration gradient at each time step in which a calculation is repeated in a heat treatment process (hereinafter referred to as a second conventional example).

[0004]

However, in the first conventional example, it is necessary to judge how finely the mesh should be cut to reduce the numerical calculation error. There is a problem that it requires a high knowledge of the operation and is a difficult task for general users. Also, in order to improve the calculation accuracy, Si / SiO for which the mesh should be fined
_{(2) Since} the positions of interfaces and surfaces change in the course of the simulation, it is necessary to refine the mesh over a wide range in advance, and there has been a problem that the calculation efficiency is deteriorated. Further, the second conventional example has a problem that it takes a long calculation time because the mesh is re-carved every time step.

An object of the present invention is to solve the above-mentioned problems and to provide a semiconductor process simulation method capable of executing a highly accurate simulation in a short time without requiring high knowledge about the simulation.

[0006]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention simulates each manufacturing process of a semiconductor device. A first step is to generate a basic mesh obtained by finely chopping a mesh near the joint, and then to execute a simulation of each manufacturing process.
That is, the present invention is a semiconductor process simulation for simulating a manufacturing process of a semiconductor device having a semiconductor substrate having a junction formed such that regions of different conductivity types are in contact with each other, and includes a predetermined process. Determining the position of the junction of the semiconductor substrate based on the one-dimensional impurity concentration of the semiconductor substrate obtained by the simulation in the one-dimensional direction, finely dividing the mesh near the junction, and A mesh generation step of generating a basic mesh by coarsely chopping a mesh other than the above, based on each of the manufacturing process models of the semiconductor device created in advance and the setting conditions of each of the manufacturing processes based on the basic mesh, At least one calculation step for performing a simulation of each manufacturing process. And wherein the door.

Further, in the present invention, in the case where the calculation step includes an oxidation step calculation step of executing a simulation of the oxidation step, in order to improve the accuracy of the simulation of the oxidation step, in the oxidation step calculation step, The oxide film thickness is determined by a one-dimensional simulation in the thickness direction of the oxide film, and a mesh from the surface of the semiconductor substrate of the basic mesh to a predetermined depth of the basic mesh is further finely divided based on the oxide film thickness. It is preferable to simulate the oxidation process using the divided meshes.

In order to efficiently execute a simulation of another process calculated after the completion of the oxidation calculation, the oxidation step calculation step further includes the step of: It is preferable to include roughening the mesh other than the boundary with the film and the vicinity of each of the joints.

In the case where the calculation step includes a diffusion step calculation step of executing a diffusion step simulation, the diffusion step calculation step includes the steps of: It is determined whether an oxide film is formed on the base mesh, and if no oxide film is formed, the mesh from the surface of the semiconductor substrate of the basic mesh to a predetermined depth is further finely divided, and the division is performed. It is preferable to simulate the diffusion process using the set mesh.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a flowchart of a semiconductor process simulation method according to one embodiment of the present invention. In the semiconductor process simulation method according to the embodiment, the oxidation step shown in step S2, the step S2
7 including the diffusion process shown in FIG. 7 and the simulation of other processes shown in step S11. Prior to the simulation in each of the processes, a one-dimensional simulation was performed in step S1 to determine the bonding position of the semiconductor device. Finely chop the mesh near the joint position,
It is characterized in that a basic mesh is created so that other parts are roughly carved. Here, as other processes of step S11, for example, there are processes such as lithography, deposition, and ion implantation. Further, the basic mesh to be cut may be any of a grid-like mesh, a triangular mesh, and the like.

More specifically, in the semiconductor process simulation method of the embodiment, step S
In the first method, first, for example, when ion implantation is performed from the surface of a semiconductor substrate, the concentration distribution of impurities in the thickness direction is obtained by simulation, and the bonding position in the thickness direction (surface of the substrate Depth x
_j ). Next, for example, the distance y _j from the mask end to the bonding position in a portion where the surface of the substrate is covered with, for example, a mask or the like and ions are not directly implanted.
Is determined by multiplying the depth x _j by a predetermined constant r to determine the bonding position in the width direction of the semiconductor substrate. The constant r for obtaining the bonding position in the width direction will be described in detail in the description of the embodiment. Then, the meshes near the joining position in the thickness direction and the joining position in the width direction obtained as described above are finely cut, and the meshes other than the respective joining positions are coarsely cut. Create a mesh.

Next, the oxidation process simulation in step S2 will be described. When the oxidation step in step S2 is selected, the basic mesh has already been created in step S1. First, in step S3,
A one-dimensional simulation is performed to obtain an oxide film thickness t,
By multiplying the oxide film thickness t by the variable a, a depth t × a at which the mesh is to be finely cut from the substrate surface is obtained. Further, in the basic mesh, a region from the substrate surface to the depth t × a is further finely cut. The variable a will be described in detail in the description of the embodiment. Thereby, an optimal mesh for the oxidation step in the oxidation step simulation is created.

In step S4, an oxidation process simulation is performed based on the mesh for the oxidation process created in step S3, and in the process, the transport of impurities at the interface between the semiconductor substrate and the oxide film is accurately simulated. In order to do so, one mesh is created in the oxide film for each oxide film thickness dox as the oxide film thickness increases. Next, in step S5, it is determined whether or not the oxidation time has ended. If the oxidation time has ended, the process proceeds to step S6, and if not, step S4 is repeated.

In step S6, meshes other than the interface between the semiconductor substrate and the oxide film and the vicinity of the bonding position are roughened, and the process proceeds to step S12. In step S12, it is determined whether or not the simulation of all the processes has been completed. If the simulation has not been completed, the process proceeds to the next process. If the simulation has been completed, the simulation ends.

Next, a simulation of the diffusion process in step S7 will be described. Here, first, step S
In step 8, it is determined whether or not an oxide film is formed on the surface of the semiconductor substrate. If an oxide film is formed, the process proceeds to step S10. If the oxide film is not formed, the process proceeds to step S10.
Proceed to step S9. In step S9, the mesh from the surface of the semiconductor substrate to the depth dsi is finely cut, and the process proceeds to step S10. Here, the depth dsi is set based on simulation results executed under various process conditions so as to improve the accuracy of the simulation. In step S10, a diffusion simulation is performed according to a predetermined diffusion equation, and the process proceeds to step S12. That is, in the simulation of the diffusion step, if an oxide film is formed, step S3 of the oxidation step is performed.
Since the mesh near the interface between the semiconductor substrate and the oxide film is already finely cut, diffusion calculation is performed using the mesh as it is, and when the oxide film is not formed, the semiconductor substrate and the Since the mesh is not finely cut in the vicinity of the interface with the film, the diffusion calculation is executed after finely cutting the mesh in the vicinity of the interface in step S9. In this case, in any case, the diffusion calculation is performed using a finely cut mesh in the vicinity of the interface between the semiconductor substrate and the oxide film, so that the transport of impurities between the semiconductor substrate and the atmosphere can be accurately performed. Can be calculated.

In step S12, it is determined whether or not the simulation has been completed for all the processes. If the simulation has not been completed, the process proceeds to the next process. If the simulation has been completed, the simulation ends.

As described above, in the semiconductor process simulation method according to the present embodiment, before the simulation of each step, the bonding position in the thickness direction and the width direction of the semiconductor substrate is obtained by executing the one-dimensional simulation. Then, an appropriate mesh is created based on the joining position, and a simulation of each manufacturing process is executed. As a result, a basic mesh suitable for the simulation of each process can be easily generated, and an accurate simulation can be executed at high speed using the mesh.

In the oxidation process simulation in step S2 of the present embodiment, prior to the oxidation calculation, in step S3, a one-dimensional simulation is performed to obtain an oxide film thickness t, and a mesh should be finely cut from the substrate surface. Since the mesh is formed so as to finely cut the region up to the depth t × a, it is possible to form an optimal oxidation step mesh in the oxidation step simulation.

Further, in the oxidation process simulation in step S2 of the present embodiment, in step S4, an oxidation process simulation is executed based on the oxidation process mesh created in step S3, and in the process, the oxide film thickness is reduced. With the increase, one mesh is created for each oxide film thickness dox, so that the transport of impurities at the interface between the semiconductor substrate and the oxide film can be accurately simulated.

In the oxidation process simulation of the present embodiment, the mesh other than the interface between the semiconductor substrate and the oxide film and the vicinity of the bonding position is coarsened in step S6 after the calculation is completed. , Unnecessary calculations can be eliminated, and the calculation time in the next step can be shortened.

In the diffusion process simulation of the present embodiment, if the mesh at a predetermined depth from the surface of the semiconductor substrate is not finely cut in step S9, the process proceeds to step S9 until the predetermined depth dsi is reached. Since the mesh is finely cut, the transport of impurities between the semiconductor substrate and the atmosphere can be accurately calculated.

As described above, in this embodiment, prior to the simulation of each manufacturing process, a basic mesh suitable for each process is created, and in the simulation of each manufacturing process, if necessary, the basic mesh is further added to the basic mesh. Since a new fine mesh is newly created only for a necessary part and the simulation of each manufacturing process is executed, the simulation of each process can be efficiently executed.

[0023]

Next, an embodiment of a semiconductor process simulation method according to the present invention will be described using a MOS field effect transistor shown in FIG. MO of FIG. 2 (a)
In the S field effect transistor, a gate electrode 3 is formed at a predetermined position on an upper surface of a p-type silicon substrate 1 via a gate oxide film 2, and As ions are compared on both sides of the gate electrode 3 of the p-type silicon substrate 1. 2 (a), which has an NMOS type structure in which an n ⁺ region (a source and a drain region) is formed at a very high concentration. Here, FIG. 2 (a) shows a part on the source region side. In brief, the method of manufacturing a MOS field-effect transistor described in ( ₁ ) will be described. First, a silicon oxide film (SiO ₂ ) having a predetermined thickness is formed on the surface of a p-type silicon substrate 1. Next, a gate oxide film 2 For example, a film made of poly-Si is formed, and a film such as P
The gate electrode 3 is formed by doping a large amount of (phosphorus) to lower the sheet resistance. And the gate electrode 3
Is formed, As ions are implanted using the gate electrode 3 and the gate oxide film 2 as a mask, and the n ⁺ source region 1 is formed.
a and n ⁺ drain regions are formed.

The MO of FIG. 2A formed as described above
An embodiment in which the semiconductor process simulation method of the present invention is applied to an S field effect transistor,
This will be described with reference to the flowchart of FIG. Step S1 (S1-1) First, the p-type silicon semiconductor substrate 1
The impurity concentration distribution is obtained by performing a one-dimensional simulation in the thickness direction (x direction). FIG. 2 (b)
Is obtained by the above-described one-dimensional simulation,
FIG. 6 is a conceptual diagram of a graph showing a net dopant concentration with respect to a depth x in a p-type silicon substrate 1, and FIG. 6 is a graph showing an example of an actual simulation of a net dopant concentration with respect to a depth.

Here, in the graph shown in FIG. 6, a simulation is performed by setting a one-dimensional analysis region to a portion from the surface to a depth of 4 μm and uniformly meshing the portion so that the mesh width becomes 50 °. , Substrate B (boron)
The concentration was set to 7 × 10 ¹⁴ / cm ³ and As (arsenic)
Is a net dopant profile after implanting at 90 keV and 5 × 10 ¹⁵ / cm ² and then diffusing at a temperature of 950 ° C. for 50 minutes.

(S1-2) Next, a junction position xj in the depth direction (x direction) of the junction 4 is determined based on the determined impurity concentration distribution. Here, the junction position xj can be obtained as the value of x corresponding to the minimum value of the dopant concentration in the graph of FIG. (S1-3) Next, the junction position xj in the depth direction is multiplied by a coefficient r to obtain a p-type silicon semiconductor substrate 1 in the width direction (y direction).
The joining position yj of the joining portion 4 is determined. Here, the bonding position yj indicates a bonding position formed immediately below the gate oxide film 2 serving as a mask, and is represented by a distance from an end of the gate oxide film 2 to the bonding position. The coefficient r is set based on the results of simulations performed under various process conditions so that the simulation accuracy is improved.

(S1-4) Then, the p-type silicon substrate 1
3A, the joining positions xj, y
Engrave in a grid-like mesh so that the vicinity of j becomes fine. Here, as to how finely the mesh up and down or left and right of the joining positions xj and yj is carved,
Based on the simulation results executed under various process conditions, settings are made to improve the accuracy of the simulation.

As described above, in step S1, the mesh near the joining positions xj and yj can be cut so as to be fine. In step S1, (S1-
1) to (S1-4) are programmed in advance, and a mesh is automatically created by inputting each condition that is a predetermined initial value.

Next, it is assumed that the oxidation step of step S2 is selected. Here, first, in step S3, the oxide film thickness t is calculated by one-dimensional simulation, and a mesh near the surface from the surface of the p-type silicon substrate 1 to a depth t × a is finely cut. Here, the coefficient a is set based on the simulation results executed under various process conditions so that the simulation accuracy is improved. Thus, a mesh optimal for the calculation of the oxidation step as shown in FIG. 3B is generated. Next, in step S4, a calculation of an oxidation process is performed, and every time an oxide film having an oxide film thickness dox is formed, a mesh is formed, and the process proceeds to step S5 to repeat step S4 until the oxidation time ends. . As a result, one oxide film thickness dox
The mesh of the book is formed, so that the transport of impurities at the Si / SiO ₂ interface can be accurately solved. Here, the unit oxide film thickness dox is set based on simulation results executed under various process conditions so as to improve the accuracy of the simulation. As described above, since one mesh is formed for each unit oxide film thickness dox, the mesh after the oxidation time is completed is as shown in FIG.

Next, after the oxidation time is over, step S
6, as shown in FIG.
/ Make the mesh other than the vicinity of the SiO ₂ interface coarse and delete the extra mesh. As described above, since the mesh optimal for the oxidation calculation is generated immediately before the oxidation calculation, the oxidation calculation can be performed in a short time and with high accuracy. In addition, since unnecessary meshes are eliminated when performing calculations in other steps after the oxidation calculation, calculations in other steps can be performed efficiently.

Next, the case where the diffusion step of step S7 is selected will be described. Here, first, step S8
It is determined whether or not the surface of the p-type silicon substrate 1 is exposed. If the surface is exposed, the mesh is finely cut in step S9, and then diffusion calculation is executed in step S10.
If it is not exposed, the diffusion calculation is performed without cutting the mesh more finely. That is, the case where the surface of the p-type silicon substrate 1 is not exposed is, for example, the case where the calculation of the oxidation step has been performed first, and in this case, as described above, / Si
Since the mesh in the vicinity of the O ₂ interface is finely cut, the calculation can be performed with high accuracy even if the calculation of the diffusion step is performed using the mesh as it is. However, p
When the surface of the mold silicon substrate 1 is exposed, only the mesh in the vicinity of the joint 4 is the mesh shown in FIG. Therefore, in step S9, the mesh from the surface of the p-type silicon substrate 1 to the predetermined depth dsi is finely chopped to generate the mesh shown in FIG.
In step S10, a diffusion calculation is performed. by this,
In any case, since the mesh near the joint 4 and near the surface of the substrate 1 or near the Si / SiO ₂ interface is finely cut, the diffusion process can be simulated with high accuracy. As described above, in the diffusion step of step S7, a new mesh is generated only when the substrate surface is exposed, so that simulation can be performed efficiently.

[0032]

As is apparent from the above description, according to the present invention, the position of the junction of the semiconductor substrate is determined based on the impurity concentration obtained by a predetermined one-dimensional simulation. Since the method includes a mesh generation step of generating the basic mesh based on the position of the joint, each manufacturing process can be accurately simulated. Further, since the mesh generation step can be easily programmed, it can be automatically calculated using a computer, and a simulation can be executed without requiring deep knowledge of simulation.

In the present invention, when the calculation step includes an oxidation step calculation step of executing a simulation of an oxidation step, the oxidation step calculation step is performed by a one-dimensional simulation in the thickness direction of the oxide film. The oxide film thickness is determined, the mesh from the surface of the semiconductor substrate of the basic mesh to a predetermined depth is further finely divided based on the oxide film thickness, and the oxidation process is simulated using the divided mesh. This can improve the accuracy of the simulation of the oxidation process. In addition, since the one-dimensional simulation for determining the oxide film thickness can be easily programmed, the one-dimensional simulation can be automatically calculated using a computer, and the simulation can be executed without requiring deep knowledge about the simulation.

Further, in the present invention, the oxidizing step calculation step includes simulating the oxidizing step while carving a mesh in the oxide film for each predetermined oxide film thickness in the course of the oxidation calculation. Simulation accuracy can be further improved. In addition, in the process of oxidation calculation, a mesh is cut for each predetermined oxide film thickness, so the mesh can be created automatically in the calculation process, and simulation can be performed without requiring deep knowledge of simulation it can.

In the present invention, in order to efficiently execute a simulation of another process calculated after the completion of the oxidation calculation, the oxidation process calculation step further includes the step of: By including the roughening of the mesh other than the boundary between the surface and the oxide film and the vicinity of each of the above-mentioned joints, it is possible to efficiently perform calculations in other steps performed after the oxidation step calculation step. Further, the step of roughening the mesh other than the surface of the semiconductor substrate, the boundary between the surface and the oxide film, and the vicinity of each of the bonding portions can be easily programmed, and can be automatically executed by using a computer. Perform simulations without the need for in-depth knowledge of migration.

Further, in the present invention, when the calculation step includes a diffusion step calculation step of executing a simulation of the diffusion step, in order to improve the accuracy of the simulation of the diffusion step, in the diffusion step calculation step, Judge whether or not an oxide film is formed on the surface of the semiconductor substrate, and when the oxide film is not formed, further divide the mesh of the basic mesh from the surface of the semiconductor substrate to a predetermined depth into finer meshes. By simulating the diffusion process using the divided meshes, the simulation accuracy of the diffusion process can be improved. Further, since the division of the mesh from the surface of the semiconductor substrate of the basic mesh to a predetermined depth into smaller pieces can be easily programmed, it can be automatically executed by using a computer, and deep knowledge on simulation can be obtained. Can be performed without need.

[Brief description of the drawings]

FIG. 1 is a flowchart of a semiconductor process simulation according to an embodiment of the present invention.

FIG. 2A is a schematic diagram of a MOS field effect transistor used in a semiconductor process simulation of an embodiment, and FIG. 2B is a graph showing a net dopant concentration in a depth direction x of a p-type silicon substrate 1 in FIG. It is a graph shown.

FIG. 3A is a diagram showing an initial mesh structure in which the vicinity of a joint is finely cut in a step S1, and FIG. 3B is a diagram showing a predetermined depth t × a from the surface in the initial mesh structure in a step S3. FIG. 4 is a diagram showing a mesh structure immediately before an oxidation step in which a portion is finely cut.

FIG. 4A is a diagram showing a mesh structure in an oxidation step in which one mesh is formed for each oxide film thickness dox in step S4, and FIG. 4B is a diagram showing Si / Si in step S6.
FIG. 3 is a diagram showing a mesh structure after an oxidation step in which a portion other than the vicinity of the O ₂ interface and the vicinity of the joint is roughened.

FIG. 5 is a diagram showing a mesh structure immediately before the diffusion step in which a portion having a predetermined depth dsi from the surface is further finely cut in the initial mesh structure in step S9 of the diffusion step.

FIG. 6 is a graph showing a simulation result of a net dopant concentration in a depth direction of a substrate.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... p-type silicon substrate, 1a ... n ⁺ source region, 2 ... gate oxide film, 3 ... gate electrode, 4 ... junction

Claims (5)

[Claims] 1. A semiconductor process simulation for simulating a manufacturing process of a semiconductor device having a semiconductor substrate having a junction formed such that regions of different conductivity types are in contact with each other, the semiconductor device comprising: Determining the position of the junction of the semiconductor substrate based on the one-dimensional impurity concentration of the semiconductor substrate obtained by the simulation of the direction, finely dividing the mesh near the junction, and excluding the portion near the junction. A mesh generation step of generating a basic mesh by coarsely chopping the mesh of each of the above, based on the above-mentioned basic mesh, using each manufacturing process model of a semiconductor device created in advance and setting conditions of each of the manufacturing processes, At least one calculation step for performing a simulation of the manufacturing process. Semiconductor process simulation method and butterflies. 2. The method according to claim 1, wherein the calculating step determines the oxide film thickness by one-dimensional simulation in a thickness direction of the oxide film, and based on the oxide film thickness, extends from a surface of the semiconductor substrate of the basic mesh to a predetermined depth. 2. The semiconductor process simulation method according to claim 1, further comprising an oxidizing step calculating step of further dividing the mesh into smaller pieces and simulating an oxidizing step using the divided mesh. 3. The semiconductor process simulation method according to claim 2, wherein said oxidation step calculation step further includes carving a mesh in the oxide film for each predetermined unit oxide film thickness in the course of the oxidation calculation. 4. The method according to claim 1, wherein the step of calculating the oxidation step further includes roughening a mesh other than the surface of the semiconductor substrate, a boundary between the surface and the oxide film, and the vicinity of each of the joints after the completion of the oxidation calculation. 4. The semiconductor process simulation method according to 3. 5. The method according to claim 1, wherein the calculating step determines whether an oxide film is formed on the surface of the semiconductor substrate. If the oxide film is not formed, the calculation step starts from the surface of the semiconductor substrate of the basic mesh. 2. The semiconductor process simulation method according to claim 1, further comprising: a diffusion step calculation step of further dividing a mesh up to a predetermined depth into smaller parts and simulating a diffusion step using the divided mesh.