JP4350817B2 - Semiconductor process simulation method and apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a semiconductor process simulation method and apparatus, and more particularly, a semiconductor process simulation method and apparatus for performing simulation in consideration of the influence of a diffusion state due to heat treatment of a region in which a silicon crystal is amorphized after high concentration ion implantation. About.
[0002]
[Prior art]
In today's semiconductor device development, semiconductor process simulation equipment that simulates the semiconductor manufacturing process occupies an important position, and semiconductor process simulation equipment developed as a product is becoming widespread. It's being used.
[0003]
However, the models built in commercially available semiconductor process simulation equipment are still physically insufficient, so when manufacturing semiconductor devices, the simulation parameters used for each process must be adjusted. There were many.
[0004]
In particular, in the heat treatment step in the manufacturing process, the heat treatment temperature is decreasing year by year, and in such a low temperature heat treatment, a heat treatment after high concentration ion implantation, which has not been a problem in the manufacturing process using the conventional high temperature heat treatment, is performed. However, transient accelerated diffusion is appearing.
[0005]
Therefore, in order to simulate this transient enhanced diffusion, an attempt has been made to model a crystal defect introduced into a silicon crystal by ion implantation and incorporate it into a semiconductor process simulation apparatus. Examples of such a crystal defect model include a dislocation ring model and a {311} cluster (interstitial silicon atom cluster) model.
[0006]
In the transient enhanced diffusion based on the crystal defect model described above, first, when damage is introduced into the silicon crystal by ion implantation, crystal defects such as interstitial silicon atom clusters and transition rings are formed along with this damage. The Such crystal defects act as trap sites or supply sources of interstitial silicon atoms, and therefore, impurity diffusion is affected according to the image of the point defect diffusion model. Since such crystal defects such as interstitial silicon atom clusters and transition rings are formed at different locations and decomposition times, transient enhanced diffusion can be explained for each.
[0007]
In addition, it is preferable to use numerical values based on experimental data observed by a transmission electron microscope or the like as the above-mentioned crystal defect parameters, but in practice, they are often handled as simple parameters in simulation and are not necessarily accurate. The simulation was not always performed.
[0008]
[Problems to be solved by the invention]
However, in such a conventional semiconductor process simulation apparatus, in the transient accelerated diffusion simulation based on the point defect diffusion model or the crystal defect model, the initial state when starting the diffusion calculation immediately after the ion implantation is very high. Although it is considered to be important, the activation concentration of impurities, the amount of damage caused by ion implantation, or the diffusion coefficient are used without considering the amorphization phenomenon of silicon crystal that occurs immediately after high concentration ion implantation. Since the simulation was adjusted to the actual data, there was a problem that the diffusion state by the heat treatment after the silicon crystal was made amorphous could not be simulated accurately by calculation.
[0009]
Furthermore, the inventors of the present application searched a known document for a semiconductor process simulation apparatus that performs a simulation in consideration of a diffusion calculation of a heat treatment after a silicon crystal is amorphized by high-concentration ion implantation. could not.
[0010]
The present invention has been made in view of the above, and a semiconductor process simulation method capable of performing a more accurate simulation by incorporating the effect of the silicon crystal becoming amorphous during high concentration ion implantation into the process simulation. And an object to provide an apparatus.
[0011]
[Means for Solving the Problems]
In order to achieve the above object, according to a first aspect of the present invention, there is provided a semiconductor process simulation method for simulating a semiconductor manufacturing process, wherein interstitial silicon introduced into a silicon substrate by ion implantation at the time of ion implantation. In consideration of atoms, using a point defect diffusion model that solves a continuous equation of point defects of impurity atoms, interstitial silicon atoms, and silicon atomic vacancies in impurity diffusion calculation in the heat treatment step after the ion implantation step, When the impurity diffusion calculation is performed using the point defect diffusion model, the region in which the impurity concentration introduced into the silicon substrate in the ion implantation step is higher than the specified concentration is an impurity atom, an interstitial silicon atom, and a silicon atomic space. As a non-moving area where no holes are diffused, it does not contribute to the diffusion continuity equation. It is obtained by the lost by reducing in things diffusion calculation.
[0012]
According to this, when performing the impurity diffusion calculation by the heat treatment after the ion implantation, in the amorphous region where the implanted impurity concentration is equal to or higher than the specified concentration, impurity atoms, interstitial silicon atoms, and silicon atom vacancies are obtained. As a non-diffusion region that does not diffuse, and the amorphous region disappears due to recrystallization during the heat treatment process, because the non-moving region disappears during impurity diffusion calculation, the semiconductor manufacturing process is more accurate. Can be simulated.
[0013]
The invention according to claim 2 is the semiconductor process simulation method according to claim 1, wherein the impurity atoms on the boundary between the diffusion region in the silicon substrate where diffusion is performed and the immobile region where diffusion is not performed, Interstitial silicon atoms and silicon atom vacancies are calculated for impurity diffusion assuming that there is no movement between the two regions.
[0014]
According to this, since the impurity atoms, interstitial silicon atoms, and silicon atom vacancies on the boundary between the diffusion region and the non-moving region are handled as not moving between the two regions, the silicon substrate is defined as the diffusion region. When divided into immobile regions, the total amount of impurity atoms, interstitial silicon atoms, and silicon atom vacancies can be preserved.
[0015]
According to a third aspect of the present invention, in the semiconductor process simulation method according to the first aspect, lattice points are formed on a boundary between a diffusion region in the silicon substrate where diffusion is performed and a stationary region where diffusion is not performed. The mesh generated so as to exist is used for impurity diffusion calculation, and remeshing is performed so that a lattice point exists on the boundary between the diffusion region and the non-moving region as the non-moving region is reduced during the impurity diffusion calculation. To do.
[0016]
According to this, since the lattice points exist on the boundary between the diffusion region and the non-moving region, the diffusion region and the non-moving region can be handled as different material regions. In addition, as the immobile area shrinks during the impurity diffusion calculation, lattice points exist on the boundary between the diffusion area and the immobile area when the calculation target area is remeshed. Even in the middle, the diffusion region and the non-moving region can be handled as different material regions.
[0017]
Further, the invention according to claim 4 is the invention according to claim 1. Or 4. The semiconductor process simulation method according to claim 3, wherein a boundary between a diffusion region where diffusion is performed in the silicon substrate and a non-diffusion region where diffusion is not performed is perpendicular to the boundary surface during impurity diffusion calculation, and , Moving in the direction of the immobile area as a function of time.
[0018]
According to this, since the boundary between the diffusion region and the immobile region is perpendicular to the boundary during the impurity diffusion calculation and moves in the immobility region direction as a function of time, the amorphous region is reduced during the heat treatment, It is possible to perform a process simulation expressing the characteristics of the amorphous region that disappears.
[0019]
According to a fifth aspect of the present invention, there is provided the semiconductor process simulation method according to the first aspect, wherein interstitial silicon atoms and silicon atomic vacancies in a stationary region in which no diffusion is performed in the initial state of the impurity diffusion calculation. The concentration of the pores is the equilibrium concentration.
[0020]
According to this, since the concentration of interstitial silicon atoms and silicon atomic vacancies in the immobile region in which the diffusion is not performed in the initial state of the impurity diffusion calculation is an equilibrium concentration, when the amorphous region is recrystallized, It is possible to perform a process simulation expressing that damage due to ion implantation in the recrystallization region is eliminated.
[0021]
According to a sixth aspect of the present invention, in the semiconductor process simulation apparatus for simulating a semiconductor manufacturing process, an impurity concentration profile after ion implantation into a silicon substrate and an impurity for determining whether diffusion is performed or not are performed. First boundary calculating means for calculating a boundary between a diffusion region where diffusion is performed and a non-diffusion non-moving region based on a specified concentration of silicon, interstitial silicon atom concentration in the non-moving region, and silicon atomic vacancies A point defect initial profile calculation means for calculating an interstitial silicon atom concentration profile and a silicon atom vacancy concentration profile with the concentration as an equilibrium concentration, and lattice points are arranged on the boundary between the diffusion region and the immobile region. A mesh generating means for generating a mesh and the above-mentioned series for each step of impurity diffusion calculation. A second boundary is calculated by assuming that the boundary between the diffusion region and the non-moving region in the silicon substrate moves perpendicularly to the boundary surface during the impurity diffusion calculation and moves in the direction of the non-moving region as a function of time. Boundary calculation means, physical quantity projection calculation means for projecting physical quantities on the lattice of the old mesh onto the new mesh when performing remeshing during the diffusion process; A point defect diffusion model calculation means for performing impurity diffusion calculation using a point defect diffusion model that solves a continuous equation of point defects of impurity atoms, interstitial silicon atoms, and silicon atomic vacancies; It is equipped with.
[0022]
According to this, the boundary between the diffusion region and the non-moving region is calculated based on the specified impurity concentration with respect to the impurity concentration profile after the ion implantation by the first boundary calculating unit, and the non-moving region by the point defect initial profile calculating unit. Calculate the interstitial silicon atom concentration profile and silicon atom vacancy concentration profile, which are the initial states of the diffusion calculation, using the interstitial silicon atom concentration and silicon atom vacancy concentration as the equilibrium concentration. The mesh is generated so that the lattice points are arranged on the boundary of the substrate, and the boundary between the diffusion region and the stationary region in the silicon substrate is calculated for the impurity diffusion at each step of the impurity diffusion calculation by the second boundary calculation means. New boundary is calculated as moving in the direction perpendicular to the boundary surface and in the direction of the immobile area. And, when performing the remeshing during the diffusion process by a physical quantity projection calculation unit, and adapted to project a physical quantity on the grid of the old mesh to the new mesh. For this reason, by performing the semiconductor process simulation method according to the first to fifth aspects, the simulation of the semiconductor manufacturing process can be performed closer to the actual manufacturing process.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of a semiconductor process simulation method and apparatus according to the present invention will be described below in detail with reference to the accompanying drawings.
[0024]
[Embodiment 1]
FIG. 1 is a diagram for explaining a method of determining a non-moving region where diffusion is not performed based on an impurity concentration profile after ion implantation into a silicon substrate and a predetermined designated concentration. The horizontal axis in the impurity concentration profile 10 in FIG. 1 indicates the depth from the surface of the silicon substrate, and the vertical axis indicates the impurity concentration.
[0025]
As shown in FIG. 1, the user of the semiconductor process simulation apparatus designates the impurity concentration that does not move the diffusion as the designated concentration 12 with respect to the impurity concentration profile 10 in the silicon substrate after the ion implantation. A region having a high impurity concentration is defined as a region that does not move with respect to diffusion, that is, a fixed region 14.
[0026]
In general, an impurity used as a dopant in a semiconductor process is a substitutional impurity atom that can be substituted into a site of a silicon crystal lattice. Such diffusion of substitutional impurity atoms is thought to progress as impurity atoms form pairs with interstitial silicon atoms or interstitial silicon vacancies. It is a defect diffusion model.
[0027]
On the other hand, in the region where the silicon crystal in the silicon substrate is amorphized by high-concentration ion implantation as described above, the crystal lattice is broken, so interstitial silicon atoms and silicon atom vacancies Concentration cannot be defined. Therefore, the diffusion of impurities means that the above diffusion mechanism by making a pair with interstitial silicon atoms and silicon interstitial vacancies does not work, and the impurity atoms move through the sites where silicon bonds are vacant. Another diffusion mechanism is considered to be the main. In such a diffusion mechanism, the diffusion rate is considerably slower than the diffusion mechanism paired with interstitial silicon atoms and interstitial silicon vacancies, and can be almost ignored in the process simulation.
[0028]
As described above, in the first embodiment, since the silicon crystal is amorphous in the region (immobility region 14) having the impurity concentration of 12 or more, the impurity atom, interstitial silicon atom, or inter-silicon atom Treated as a region where no diffusion of holes occurs.
[0029]
FIG. 2 is a diagram for explaining the movement of the boundary 20 between the diffusion region 16 where diffusion is performed and the immovable region 14 where diffusion is not performed.
[0030]
In FIG. 2, the boundary 20 between the diffusion region 16 and the non-moving region 14 moves in the direction of arrow A where the non-moving region 14 becomes smaller due to diffusion, and disappears during the impurity diffusion calculation. This is because the amorphous region disappears due to recrystallization during the heat treatment step in an actual semiconductor manufacturing process.
[0031]
In the example of FIG. 2, when viewed in the impurity concentration profile in the depth direction, there are two boundaries 20 between the diffusion region 16 where diffusion is performed and the non-diffusion region 14 where diffusion is not performed. The two boundaries 20 are moved in the direction of reducing the immovable region 14, that is, in the direction of arrow A.
[0032]
FIG. 3 is a diagram for explaining the movement of the boundary 30 between the diffusion region 16 and the immobile region 14. In FIG. 3, when viewed from the impurity concentration profile 10 in the depth direction, there is one boundary 30 between the diffusion region 16 and the immobile region 14 depending on the ion implantation conditions. In this case, the boundary 30 between the diffusion region 16 and the non-moving region 14 moves in the direction of reducing the non-moving region 14 as in the case of FIG. 2, but since there is only one boundary 30, It moves in the surface direction, that is, in the direction of arrow B.
[0033]
Furthermore, in the first embodiment described above, in the region where the silicon crystal in the silicon substrate is made amorphous by ion implantation (immobilized region 14), the crystal lattice is broken. Although it has been explained that the concentration of vacancies cannot be defined, as described above, the boundary between the crystalline region (diffusion region 16) and the amorphous region (immobilized region 14) moves, and the impurity diffusion calculation in the crystalline region In addition, since the concentration of interstitial silicon atoms and interstitial silicon vacancies is required, it is left as a variable even in a stationary region where diffusion is stationary.
[0034]
As described above, according to the first embodiment, when the impurity diffusion calculation is performed by the heat treatment after the ion implantation, the region in which the implanted impurity concentration is equal to or higher than the specified concentration is defined as an impurity atom, an interstitial silicon atom, In addition, an amorphous region is taken into consideration when the impurity diffusion calculation is performed as a non-moving region where silicon atomic vacancies do not diffuse. As described above, the non-moving region disappears during the impurity diffusion calculation in consideration of the property that the amorphous region disappears due to recrystallization during the heat treatment process, thereby more accurately simulating the semiconductor manufacturing process. can do.
[0035]
In particular, in the first embodiment, a silicon crystal region and an amorphous region are used when simulating a semiconductor manufacturing process using a point defect diffusion model method in which a continuous equation is solved simultaneously for impurity diffusion calculation. By treating as a different material having different physical properties, the impurity diffusion calculation can be performed in a state closer to the actual impurity diffusion state, so that an accurate simulation can be performed.
[0036]
[Embodiment 2]
The second embodiment relates to boundary conditions on the boundary between the diffusion region and the non-moving region. FIG. 4 is a diagram for explaining an initial state of impurity diffusion calculation. As shown in FIG. 4, a semiconductor process simulation apparatus for an impurity concentration profile 40 after ion implantation into a silicon substrate for process simulation is performed. A region having an impurity concentration higher than the specified concentration 42 designated by the user is defined as a non-diffusion region 44 where diffusion is not performed, and a region having a lower impurity concentration is defined as a diffusion region 46 where diffusion is performed. The boundary between 44 and the diffusion region 46 is defined as a boundary 48.
[0037]
In the second embodiment, there is no movement of impurity atoms, interstitial silicon atoms, and silicon atom vacancies between the two regions on the boundary 48 between the stationary region 44 and the diffusion region 46 described above. It was made to process.
[0038]
As a result, as shown in FIG. 5 showing the impurity concentration profile after the impurity diffusion calculation at one time step, a difference in the impurity concentration occurs on the boundary 58 between the two regions after the diffusion calculation at one time step. On the boundary 58 between the non-moving region 54 and the diffusion region 56, since there is no movement of the impurity atoms, the interstitial silicon atoms, and the silicon atom vacancies between the two regions, the impurities are impurities in the region where diffusion is performed. While the total amount of is preserved, it diffuses from the higher impurity concentration to the lower impurity concentration.
[0039]
Further, since the impurities in the immovable region 54 where diffusion is not performed are not diffused, the total amount of impurities is also preserved.
[0040]
As described above, according to the second embodiment, the impurity diffusion calculation can be performed in a state where the total amount of impurities is preserved in all the regions to be calculated in the process simulation.
[0041]
In the second embodiment, the description is mainly made on the impurity atoms, but the same applies to the case of interstitial silicon atoms and silicon atom vacancies.
[0042]
[Embodiment 3]
The third embodiment relates to the handling of meshes and lattice points in the actual calculation using the finite element method or the like according to the first and second embodiments. FIG. 6 shows a cross-sectional view of a semiconductor device for explaining generation of a mesh by two-dimensional calculation. In FIG. 6, a large number of lattice points 62 exist in the silicon substrate 60, and when ion implantation is performed in the silicon substrate 60, diffusion is performed and diffusion is performed in accordance with the impurity concentration. The mesh generated so that the lattice point 62 exists on the boundary 64 is used for the impurity diffusion calculation. The non-moving region where the diffusion inside the boundary 64 is not performed is reduced as the impurity diffusion calculation proceeds. Accordingly, as shown in FIG. 6, a new boundary between the diffusion region and the non-moving region ( Also for (not shown), remeshing is performed so that the lattice point 62 exists on the boundary.
[0043]
Further, since the above-described boundary 64 is formed by ion implantation, it is not formed below the gate 66 serving as an ion implantation mask formed on the surface of the silicon substrate 60.
[0044]
As described above, according to the third embodiment, since the lattice points exist on the boundary between the diffusion region and the immobile region, the diffusion region and the immobile region can be handled as different material regions. It becomes. In addition, as the fixed region is reduced during the impurity diffusion calculation, lattice points exist on the boundary between the diffusion region and the fixed region when the calculation target region is remeshed. Even inside, the diffusion region and the immobile region can be handled as separate material regions.
[0045]
[Embodiment 4]
The fourth embodiment relates to the handling of movement during calculation of impurity diffusion at the boundary between the diffusion region and the non-moving region in the first and third embodiments. FIG. 7 is a cross-sectional view of a semiconductor device for explaining a moving direction of a boundary between a diffusion region where diffusion is performed and a non-diffusion region where diffusion is not performed by two-dimensional calculation. In FIG. 7, the boundary 72 between the diffusion region and the non-moving region in the silicon substrate 70 is perpendicular to the boundary surface, and in the direction of the non-diffusion region (direction of arrow C in the drawing). Let's move with a function of time.
[0046]
The movement function of the boundary 72 between the two regions may be such that the movement speed in the direction of the arrow C perpendicular to the boundary 72 is constant, so that the user of the semiconductor process simulation apparatus can reproduce the amorphous region. If more detailed data on the crystallization speed is possessed, the data may be used as a function depending on the moving time of the boundary 72 described above.
[0047]
In the fourth embodiment, how the remeshing of the third embodiment is performed when the boundary 72 between the two regions is moved will be described with a depth profile.
[0048]
First, in order to simplify the description, the case where there is one boundary between the diffusion region and the non-moving region will be described. For example, as shown in FIG. 5, when the impurity concentration profile after the impurity diffusion calculation in one time step is used, a step difference in impurity concentration occurs on the boundary 58 between the two regions 54 and 56. In such a case, as shown in FIG. 8 for explaining the state after the old time step calculation, the lattice point 86 exists on the boundary 88b in the old time step.
[0049]
Then, the position of the boundary 88a in the new time step can be known from the moving speed of the boundary 88b.
[0050]
FIG. 9 is a diagram for explaining mesh generation and physical quantity projection for new time step calculation. As shown in FIG. 9, a mesh used for calculation of the new time step is generated so that a lattice point 96 exists on the position of the boundary 98a. At this time, physical quantities such as impurity concentration, interstitial silicon atom concentration, and interstitial void concentration on the lattice point of the old mesh are projected onto the lattice point of the new mesh. Also, the physical quantity of the lattice point on the boundary of the new mesh is obtained by the same process as described above.
[0051]
As described above, according to the fourth embodiment, the boundary between the diffusion region and the non-moving region is perpendicular to the boundary during the impurity diffusion calculation, and moves in the non-moving region direction as a function of time. It becomes possible to perform a process simulation expressing the characteristics of the amorphous region in which the amorphous region shrinks and disappears during the heat treatment.
[0052]
[Embodiment 5]
FIG. 10 is a diagram for explaining a point defect initial density profile setting method according to the fifth embodiment. As shown in FIG. 10, in the fifth embodiment, immediately after the high-concentration ion implantation step, that is, in the initial state of the impurity diffusion calculation, interstitial silicon atoms 102 and silicon atoms in the immobile region 108 where diffusion is not performed. The concentration with the holes 104 was set to the equilibrium concentration.
[0053]
Thus, in the amorphous region, it can be incorporated into the process simulation that the damage caused by the ion implantation is eliminated by the silicon crystal becoming amorphous.
[0054]
Of course, depending on the process conditions for the simulation, a source of interstitial silicon atoms may be required near the surface of the silicon substrate. Processing is performed assuming that silicon atoms are supplied. This is because, when actually observed with a transmission electron microscope, it is known that a dislocation ring may be observed near the boundary between the crystalline region and the amorphous region immediately after ion implantation. .
[0055]
As described above, according to the fifth embodiment, in the initial state of the impurity diffusion calculation, the concentration of interstitial silicon atoms and silicon atomic vacancies in the immobile region is set to the equilibrium concentration, so that the amorphous region is recrystallized. In the process, the process simulation expressing that the damage due to the ion implantation in the recrystallization region is eliminated can be performed.
[0056]
[Embodiment 6]
In the sixth embodiment, a semiconductor process simulation apparatus capable of implementing the semiconductor process simulation method described in the first to fifth embodiments will be described.
[0057]
FIG. 11 is a block diagram showing a configuration of the impurity diffusion calculation unit 110 in the semiconductor process simulation apparatus according to the present invention. The impurity diffusion calculation unit 110 shown in FIG. 11 includes a first boundary calculation unit 112 as a first boundary calculation unit, a point defect initial profile calculation unit 114 as a point defect initial profile calculation unit, and a mesh as a mesh generation unit. The generation unit 116, a second boundary calculation unit 118 as a second boundary calculation unit, a physical quantity projection calculation unit 120 as a physical quantity projection calculation unit, a point defect diffusion model calculation unit 122, and the like.
[0058]
The first boundary calculation unit 112 calculates the impurity concentration profile in the silicon substrate after the ion implantation, and compared with the designated concentration that does not move the diffusion, the diffusion region where the diffusion is performed and the stationary region where the diffusion is not performed And the boundary between the two regions is calculated. The first boundary calculation unit 112 calculates the boundary between the diffusion region and the non-moving region according to the method described in the first embodiment, and assumes that the diffusion region and the non-moving region are different materials in calculation. Each area is allocated within the area.
[0059]
The point defect initial profile calculator 114 calculates the interstitial silicon atom concentration profile and the silicon atom vacancy concentration profile, which are the initial states of the impurity diffusion calculation, in the immobile region where diffusion is not performed. The vacancy concentration is assumed to be an equilibrium concentration, and calculation is performed using an interstitial silicon atom concentration profile or a silicon atom vacancy concentration profile due to ion implantation damage in a diffusion region where diffusion is performed.
[0060]
The mesh generation unit 116 generates the mesh so that lattice points are arranged on the boundary between the diffusion region where diffusion is performed and the non-diffusion region where diffusion is not performed. The mesh generation unit 116 uses the calculation result of the first boundary calculation unit 112 in the first step of the impurity diffusion calculation, and uses the calculation result of the second boundary calculation unit 118 during the impurity diffusion calculation. Then, mesh generation is performed.
[0061]
The second boundary calculation unit 118 calculates the boundary for each time step in consideration of the movement of the boundary between the diffusion region where diffusion is performed and the non-diffusion region where diffusion is not performed during the diffusion process. It is.
[0062]
The physical quantity projection calculation unit 120 projects the physical quantity on the lattice of the old mesh onto the new mesh when performing remeshing during impurity diffusion calculation. That is, the physical quantity projection calculation unit 120 calculates impurity diffusion calculation results such as impurity atoms, interstitial silicon atoms, and silicon interatomic vacancies in the old time step in the new time step during the impurity diffusion calculation. Are projected onto the grid points of the new mesh generated by the mesh generation unit 116.
[0063]
The point defect diffusion model calculation unit 122 is a basic component for performing the impurity diffusion calculation in the impurity diffusion calculation unit 110 described above, and is a conventional component.
[0064]
FIG. 12 is a diagram for explaining the processing order of each part when simulating a semiconductor manufacturing process in the semiconductor process simulation apparatus of the present invention. First, as shown in FIG. 12, as a pre-process of impurity diffusion calculation in the impurity diffusion calculation unit 110 surrounded by a broken line, an impurity concentration profile indicating an impurity concentration distribution in the substrate is obtained by ion implantation into the silicon substrate. The calculation is performed by the ion implantation calculation unit 130.
[0065]
Next, the impurity diffusion calculation process in the impurity diffusion calculation unit 110 is executed in response to the calculation result of the ion implantation calculation unit 130 described above. As shown in FIG. 12, in the impurity diffusion calculation unit 110, an initial process in the impurity diffusion calculation is performed by the first boundary calculation unit 112 and the point defect initial profile calculation unit 114.
[0066]
Further, the mesh generation unit 116, the second boundary calculation unit 118, the physical quantity projection calculation unit 120, and the point defect diffusion model calculation unit 122 are used in repetition of the time step of the impurity diffusion calculation.
[0067]
Then, the calculation result in the impurity diffusion calculation unit 110 is taken over by the next process calculation unit 132 and sequentially processed, thereby simulating the semiconductor manufacturing process.
[0068]
As described above, according to the sixth embodiment, as the impurity diffusion calculation unit of the semiconductor process simulation apparatus, the first boundary calculation unit, the point defect initial profile calculation unit, the mesh generation unit, and the second boundary calculation unit In addition, since the physical quantity projection calculation unit is provided and the point defect diffusion model calculation unit is used for the calculation processing, the simulation of the semiconductor manufacturing process can be performed in a state closer to the actual manufacturing process.
[0069]
【The invention's effect】
As described above, according to the first aspect of the present invention, the non-diffusion region that is amorphized and is not diffused is considered in the impurity diffusion calculation, and the amorphous region is not recrystallized during the heat treatment step. Considering that the fixed region disappears during the impurity diffusion calculation, a more accurate simulation can be performed.
[0070]
According to the second aspect of the present invention, when the silicon substrate is divided into a diffusion region and a non-moving region, diffusion is performed while preserving the total amount of impurity atoms, interstitial silicon atoms, and silicon atomic vacancies. Calculations can be made.
[0071]
According to the third aspect of the present invention, the boundary between the diffusion region and the fixed region is always obtained even when the calculation target region is remeshed before the impurity diffusion calculation or with the reduction of the fixed region during the impurity diffusion calculation. Since the lattice point exists above, the two regions can be handled as different material regions.
[0072]
According to the invention described in claim 4, it is assumed that the movement of the boundary between the diffusion region and the non-moving region during the impurity diffusion calculation moves as a function of time in the direction of the non-moving region perpendicular to the boundary. Since the area is reduced and disappears, the characteristics of the amorphous area can be expressed by simulation.
[0073]
According to the invention described in claim 5, when the amorphous region is recrystallized in the initial state of the impurity diffusion calculation, the concentration of interstitial silicon atoms and silicon atomic vacancies in the immobile region is set as the equilibrium concentration. It can be expressed by simulation that damage caused by ion implantation in the recrystallization region is eliminated.
[0074]
Furthermore, according to the invention described in claim 6, it is possible to obtain a semiconductor process simulation apparatus capable of suitably executing the semiconductor process simulation method described in claims 1-5.
[Brief description of the drawings]
FIG. 1 is a diagram for explaining a method for determining a non-moving region based on an impurity concentration profile after ion implantation into a silicon substrate and a predetermined designated concentration.
FIG. 2 is a diagram illustrating movement of a boundary between a diffusion region where diffusion is performed and a non-diffusion region where diffusion is not performed;
FIG. 3 is a diagram for explaining a movement of a boundary between a diffusion region and a non-moving region.
FIG. 4 is a diagram illustrating an initial state of impurity diffusion calculation.
FIG. 5 is a diagram for explaining an impurity concentration profile after diffusion calculation in one time step.
FIG. 6 is a cross-sectional view of a semiconductor device for explaining generation of a mesh by two-dimensional calculation.
FIG. 7 is a cross-sectional view of a semiconductor device for explaining a moving direction of a boundary between a diffusion region and a non-moving region by two-dimensional calculation.
FIG. 8 is a diagram illustrating a state after calculation of an old time step.
FIG. 9 is a diagram for explaining mesh generation and physical quantity projection for new time step calculation;
10 is a diagram illustrating a method for setting a point defect initial density profile according to a fifth embodiment. FIG.
FIG. 11 is a block diagram showing a configuration of an impurity diffusion calculation unit of the semiconductor process simulation apparatus according to the present invention.
FIG. 12 is a diagram for explaining the processing order of each part when simulating a semiconductor manufacturing process in the semiconductor process simulation apparatus of the present invention.
[Explanation of symbols]
10 Impurity concentration profile
12 Specified concentration
14 Immovable area
16 Diffusion region
20 border
30 border
40 Impurity concentration profile
42 Specified concentration
44 Immovable area
46 Diffusion region
48 border
50 Impurity concentration profile
54 Immovable area
56 Diffusion region
58 boundary
60 Silicon substrate
62 lattice points
64 boundaries
66 Gate (mask)
70 Silicon substrate
72 boundary
76 Gate (mask)
80 Impurity concentration profile
82 Immovable area
84 Diffusion region
86 lattice points
88a, 88b boundary
90 Impurity concentration profile
92 Immovable area
94 Diffusion area
96 grid points
98a, 98b boundary
100 impurities
102 interstitial silicon atoms
104 Silicon interatomic vacancies
106 Specified concentration
108 Immovable area
110 Impurity diffusion calculator
112 First boundary calculation unit
114 point defect initial profile calculator
116 Mesh generator
118 Second boundary calculation unit
120 Physical quantity projection calculator
122 Point defect diffusion model calculator
130 Ion implantation calculator
132 Next process calculator

Claims (6)

In a semiconductor process simulation method for simulating a semiconductor manufacturing process,
When ion implantation is performed, interstitial silicon atoms introduced into the silicon substrate by ion implantation are taken into account, and impurity diffusion calculation in the heat treatment process after the ion implantation process is performed for impurity atoms, interstitial silicon atoms, and silicon atom vacancies. Using a point defect diffusion model that solves the continuous equation of point defects simultaneously,
When the impurity diffusion calculation is performed using the point defect diffusion model, the region where the impurity concentration introduced into the silicon substrate in the ion implantation step is a specified concentration or more is an impurity atom, an interstitial silicon atom, and a silicon atom. Suppose that it does not contribute to the diffusion continuity equation as a stationary region where no diffusion of vacancies takes place,
A semiconductor process simulation method characterized in that the non-moving region is reduced and disappears during impurity diffusion calculation.   Impurity diffusion on the boundary between the diffusion region in which diffusion is performed in the silicon substrate and the immobile region in which diffusion is not performed, assuming that impurity atoms, interstitial silicon atoms, and silicon atom vacancies do not move between the two regions The semiconductor process simulation method according to claim 1, wherein calculation is performed. Using the mesh generated so that lattice points exist on the boundary between the diffusion region where diffusion is performed in the silicon substrate and the non-diffusion region where diffusion is not performed, for impurity diffusion calculation,
2. The semiconductor process simulation according to claim 1, wherein remeshing is performed so that a lattice point exists on a boundary between the diffusion region and the non-moving region as the non-moving region is reduced during the impurity diffusion calculation. Method. The boundary between the diffusion region in the silicon substrate where diffusion is performed and the non-diffusion stationary region moves perpendicular to the boundary surface and in the direction of the stationary region as a function of time during the impurity diffusion calculation. semiconductor process simulation method according to claim 1 or claim 3, characterized in that the go.   2. The semiconductor process simulation method according to claim 1, wherein the concentration of interstitial silicon atoms and silicon atom vacancies in the immobile region in which no diffusion is performed in the initial state of the impurity diffusion calculation is set as an equilibrium concentration. . In a semiconductor process simulation apparatus for simulating a semiconductor manufacturing process,
The boundary between the diffusion region where diffusion is performed and the non-diffusion region where diffusion is not performed is determined based on the impurity concentration profile after ion implantation into the silicon substrate and the specified concentration of the impurity that determines whether diffusion is performed or not. First boundary calculating means for calculating;
Point defect initial profile calculation means for calculating the interstitial silicon atom concentration profile and the silicon atom vacancy concentration profile with the interstitial silicon atom concentration in the immobile region and the silicon atom vacancy concentration as the equilibrium concentration, and
Mesh generating means for generating a mesh so that lattice points are arranged on the boundary between the diffusion region and the immobile region;
At each step of the impurity diffusion calculation, the boundary between the diffusion region and the stationary region in the silicon substrate moves in the direction perpendicular to the boundary surface and toward the stationary region as a function of time during the impurity diffusion calculation. Second boundary calculation means for calculating a new boundary as
Physical quantity projection calculation means for projecting physical quantities on the lattice of the old mesh to the new mesh when performing remeshing during the diffusion process;
A point defect diffusion model calculation means for performing impurity diffusion calculation using a point defect diffusion model that solves a continuous equation of point defects of impurity atoms, interstitial silicon atoms, and silicon atomic vacancies;
A semiconductor process simulation apparatus comprising:

Images