Arsenic ion implantation method in polycrystalline silicon
By ion implantation of arsenic ions and carbon ions in the polycrystalline silicon layer, and combined with heat treatment, the carbon-silicon bonds are used to prevent the diffusion of arsenic ions, the problem of arsenic ions diffusion in polycrystalline silicon materials is solved, and the stability of the doped layer and device performance are improved.
Patent Information
- Application Number
- CN202311516881.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-11-14
- Publication Date
- 2025-05-16
AI Technical Summary
In the prior art, arsenic ions are problem that diffusion occurs after ion implantation in polycrystalline silicon materials.
The polycrystalline silicon layer is ion implanted, and combined with the heat treatment process, carbon ions reduce the distance between lattice points by forming carbon-silicon bonds and preventing the diffusion of arsenic ions.
Effectively reduce the diffusion of arsenic ions in silicon materials, improve the stability of arsenic ions in polycrystalline silicon, and prevent the reduction of device performance caused by uneven doping.
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Figure CN120015614A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of manufacturing semiconductor components, and in particular to a method for implanting arsenic ions into polysilicon. Background Art
[0002] Ion implantation is a material surface improvement technology that has flourished and been widely used internationally in recent years. Its principle is: an ion beam with an energy of, for example, 100 KeV is injected into the material, causing a series of physical and chemical interactions between the ion beam and the atoms or molecules in the material. The incident ions gradually lose energy and finally stay in the material, causing changes in the surface composition, structure and properties of the material, thereby optimizing the performance of the material surface or obtaining some new excellent properties.
[0003] In the current manufacturing technology of silicon-based semiconductor components, since the conductivity of silicon is very poor in a pure state, only by adding a small amount of impurities to silicon to change its structure and conductivity can silicon become a useful semiconductor. The process of adding a small amount of impurities to silicon is called doping. Silicon doping technology is the basis for the preparation of semiconductor components, and ion implantation technology is one of the most commonly used doping methods. This process is to introduce a controllable amount of impurities into the silicon substrate to change its electrical properties. Since the ion implantation technology of semiconductors can repeatedly control the concentration and depth of the doped impurities, almost all doping processes in the existing semiconductor component manufacturing technology are implemented using ion implantation technology.
[0004] Transient enhanced diffusion (TED) in semiconductor ion implantation processes is a well-known problem. When a doped layer or region is formed in a semiconductor substrate by ion implantation, the junction depth depends not only on the ion implantation energy, but also on the TED phenomenon as the implanted ions migrate through the crystal lattice during subsequent thermal treatment. TED increases the diffusion rate of the dopant in the doped layer, thereby increasing the depth of the shallowly doped layer.
[0005] Regarding the TED problem, the current research focuses on the use of carbon co-implantation to suppress the boron ions and phosphorus ions injected into the single crystal silicon substrate. The TED of boron and phosphorus is caused by the interstitial diffusion mechanism. During the annealing process of ion implantation, some carbon can be positioned on the lattice points at the early stage of regrowth and capture interstitial silicon, thereby effectively suppressing the diffusion of boron and phosphorus. In addition, the suppression of TED in the single crystal silicon substrate belongs to vertical suppression. However, in the preparation process of silicon-based semiconductor devices, it is often necessary to dope the polycrystalline silicon substrate with arsenic ions. Arsenic ions are vacancy-type doping ions, which are achieved through the vacancy diffusion mechanism during the diffusion or activation process. At present, there has not been much research on the diffusion problem caused by the doping, diffusion or activation process of arsenic ions in polycrystalline silicon materials. Summary of the invention
[0006] In view of the above-mentioned shortcomings of the prior art, an object of the present invention is to provide a method for implanting arsenic ions into polysilicon, so as to solve the problem of diffusion of arsenic ions after ion implantation into polysilicon material in the prior art.
[0007] To achieve the above object and other related objects, the present invention provides a method for implanting arsenic ions into polycrystalline silicon, the method comprising:
[0008] Providing a semiconductor substrate, on which a polycrystalline silicon layer is formed;
[0009] Performing ion implantation of arsenic ions and carbon ions in a predetermined area of the polysilicon layer;
[0010] A heat treatment process is performed on the polysilicon layer after the ion implantation.
[0011] Optionally, arsenic ions are implanted into the polysilicon first, and then carbon ions are implanted into the polysilicon; or carbon ions are implanted into the polysilicon first, and then arsenic ions are implanted into the polysilicon.
[0012] Optionally, the ion implantation depth of the carbon ions is not less than the ion implantation depth of the arsenic ions.
[0013] Furthermore, the ion implantation depth of the carbon ions is consistent with the ion implantation depth of the arsenic ions.
[0014] Optionally, the ion implantation angle of the carbon ions is not less than the ion implantation angle of the arsenic ions, and the ion implantation angle is the angle between the ion implantation direction and the surface normal of the polysilicon layer.
[0015] Furthermore, the ion implantation angle of the carbon ions is not greater than 60°.
[0016] Optionally, the heat treatment is performed on the polysilicon layer after ion implantation through a rapid thermal annealing process.
[0017] Furthermore, the rapid thermal annealing process includes laser annealing and / or spike annealing.
[0018] Optionally, when performing ion implantation of arsenic ions and carbon ions, a photoresist layer is provided in non-preset areas of the polysilicon layer for blocking.
[0019] Optionally, the method for implanting arsenic ions into polycrystalline silicon is applicable to the preparation process of CMOS devices.
[0020] As described above, the method for implanting arsenic ions into polycrystalline silicon of the present invention adds a step of implanting carbon ions when implanting arsenic ions into the polycrystalline silicon layer. When carbon atoms enter the polycrystalline silicon layer, they replace silicon atoms to form carbon-silicon bonds. Since the radius of carbon atoms is smaller than the radius of silicon atoms and the radius of arsenic atoms, the distance between lattice points is reduced, and the silicon-silicon bonds around the arsenic atoms are replaced by carbon-silicon bonds. The bond length of carbon-silicon bonds is small, which causes the shrinkage and distortion of the surrounding lattices, making the vacancies for the migration of arsenic atoms smaller, thereby preventing arsenic ions with larger atomic radius from passing through, which is equivalent to the closing of a fishing net. The arsenic ions are trapped and cannot pass through. At the same time, since the bond energy of the carbon-silicon bond is greater than the bond energy of the silicon-silicon bond, the barrier to the vacancy migration of the arsenic ions is further increased, and the difficulty of the vacancy migration of the arsenic ions is increased, and finally the diffusion of the arsenic ions in the silicon material is effectively reduced. Furthermore, since the main body of the ion implantation is polycrystalline silicon, its crystal orientation is different in various directions. Therefore, the carbon ions in the arsenic ion implantation method in polycrystalline silicon can produce an equivalent diffusion inhibition effect on the arsenic ions in various directions in the polycrystalline silicon, that is, the diffusion inhibition effect can be produced in the longitudinal direction as well as in the lateral direction. BRIEF DESCRIPTION OF THE DRAWINGS
[0021] Figure 1 Shown is a schematic diagram explaining the principle of arsenic ion vacancy migration in the silicon lattice.
[0022] Figure 2 A schematic diagram showing the principle of arsenic ion migration through vacancies in the silicon lattice after carbon ion implantation into silicon material.
[0023] Figure 3 It is a schematic diagram of the cross-sectional structure when the method for implanting arsenic ions into polycrystalline silicon of the present invention is applied in the ion implantation process of the NMOS source / drain region in a CMOS device.
[0024] Figure 4 It is a schematic cross-sectional structure diagram showing that after the ion implantation process of the NMOS source / drain region of the existing CMOS device, the arsenic ions in the NMOS gate polysilicon layer diffuse into the PMOS gate polysilicon layer.
[0025] Figure 5 It is a schematic diagram showing the cross-sectional structure in which the arsenic ions in the NMOS gate polysilicon layer have not diffused into the PMOS gate polysilicon layer after the arsenic ion implantation method in polysilicon of the present embodiment is applied to the NMOS source / drain region ion implantation process of the CMOS device.
[0026] Figure 6 It shows the distribution of arsenic ions in the polysilicon layer after ion implantation of arsenic ions into the polysilicon layer on the NMOS region only in the preparation of the CMOS device and combined with heat treatment.
[0027] Figure 7It shows the distribution of arsenic ions in the polysilicon layer after ion implantation of arsenic ions and carbon ions at an implantation angle of 45° into the polysilicon layer on the NMOS region during the preparation of the CMOS device, combined with heat treatment.
[0028] Figure 8 It shows the distribution of arsenic ions in the polysilicon layer after ion implantation of arsenic ions and carbon ions at an implantation angle of 25° into the polysilicon layer on the NMOS region during the preparation of the CMOS device, combined with heat treatment.
[0029] Component number description
[0030] 10 Semiconductor substrate
[0031] 100 NMOS area
[0032] 101 PMOS area
[0033] 11 Polysilicon layer
[0034] 12 Gate sidewall
[0035] 13 Source / Drain Region
[0036] 14 Photoresist
[0037] 15 Isolation Structure
[0038] 16. Gate dielectric layer
[0039] 17 Silicon Atom
[0040] 18 Arsenic Atom
[0041] 19 Carbon atoms
[0042] 20 Diffusion Zone DETAILED DESCRIPTION
[0043] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention.
[0044] See also Figures 1 to 5 It should be noted that the illustrations provided in this embodiment are only used to illustrate the basic concept of the present invention in a schematic manner, and the illustrations only show components related to the present invention rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout may also be more complicated.
[0045] This embodiment provides a method for implanting arsenic ions into polycrystalline silicon, the method comprising:
[0046] S1. providing a semiconductor substrate, on which a polycrystalline silicon layer is formed;
[0047] S2, performing ion implantation of arsenic ions and carbon ions in a predetermined area of the polysilicon layer;
[0048] S3, performing a heat treatment process on the polysilicon layer after ion implantation.
[0049] It should be noted that the area in the polysilicon layer that needs to be implanted with arsenic ions and carbon ions is defined as a preset area, and the area that does not need to be implanted with arsenic ions and carbon ions is defined as a non-preset area. The specific location of the preset area is designed according to actual needs and is not excessively restricted here.
[0050] like Figure 1 and Figure 2 As shown, in the method for implanting arsenic ions into polycrystalline silicon of this embodiment, when implanting arsenic ions into the polycrystalline silicon layer, an implantation step of carbon ions is added. When the carbon atom 19 enters the polycrystalline silicon layer, the carbon atom 19 replaces the silicon atom 17 to form a carbon-silicon bond. Since the radius of the carbon atom 19 is smaller than the radius of the silicon atom 17 and the radius of the arsenic atom 18, the distance between the lattice points is reduced. Figure 1 The silicon-silicon bonds around the arsenic atom 18 are Figure 2 The carbon-silicon bond in the arsenic atom is replaced by a small carbon-silicon bond length, which causes the surrounding lattice to shrink and distort, making the vacancy for the migration of arsenic atoms smaller, such as Figure 2 As shown in , arsenic ions with larger atomic radius cannot pass through, which is equivalent to the effect of closing the mouth of a fishing net, trapping the arsenic ions and preventing them from passing through. At the same time, since the bond energy of the carbon-silicon bond is greater than the bond energy of the silicon-silicon bond, the barrier to the vacancy migration of arsenic ions is further increased, and the difficulty of vacancy migration of arsenic ions is increased, and finally the diffusion of arsenic ions in the silicon material is effectively reduced; furthermore, since the main body of the ion implantation is polycrystalline silicon, its crystal orientation is different in all directions, so the carbon ions in the present method of arsenic ion implantation in polycrystalline silicon can produce an equivalent diffusion inhibition effect on the arsenic ions in all directions in the polycrystalline silicon, that is, it can produce a diffusion inhibition effect in both the longitudinal direction and the lateral direction.
[0051] There is no restriction on the order of ion implantation of arsenic ions and carbon ions in the polysilicon layer, that is, arsenic ions may be implanted into the polysilicon layer first, and then carbon ions may be implanted into the polysilicon layer; or carbon ions may be implanted into the polysilicon layer first, and then arsenic ions may be implanted into the polysilicon layer.
[0052] As a preferred example, the ion implantation depth of carbon ions is not less than the ion implantation depth of arsenic ions, so that the ion implantation range of carbon ions in the polysilicon layer completely covers the ion implantation range of arsenic ions, which can effectively inhibit the diffusion of arsenic ions in all directions in the polysilicon layer. Optimally, the ion implantation depth of carbon ions is consistent with the ion implantation depth of arsenic ions, which facilitates process control while achieving complete coverage of the ion implantation range of carbon ions with the arsenic ions, and does not introduce carbon atoms into other areas of the polysilicon layer.
[0053] As a specific example, during the ion implantation process, the ion implantation angle of carbon ions can be selected to be not less than the ion implantation angle of arsenic ions, where the ion implantation angle is defined as the angle between the ion implantation direction and the surface normal of the polysilicon layer. A carbon ion implantation shape similar to a pocket structure will be formed at both ends of the interval where the arsenic ions are implanted to effectively block the diffusion of arsenic ions. Generally, the ion implantation angle of carbon ions is selected to be not greater than 60°, for example, the ion implantation angle of carbon ions can be selected to be 10°, 25°, 40°, 50°, 60°, etc.; the ion implantation angle of arsenic ions is 0°, that is, ion implantation is performed perpendicular to the surface of the polysilicon layer, but it is not limited to this, and it can also be other implantation angles that are not greater than the ion implantation angle of carbon ions, and it is selected according to actual needs.
[0054] The polysilicon layer is heat treated to activate the implanted ions and repair lattice damage. For example, a common rapid thermal annealing process (RTA) can be selected for the heat treatment. Preferably, laser annealing and / or spike annealing in the rapid thermal annealing process are selected, that is, laser annealing or spike annealing can be selected alone, or laser annealing and spike annealing can be selected together.
[0055] When arsenic ions and carbon ions are implanted into a preset region of the polysilicon layer, non-preset regions of the polysilicon layer may be shielded, for example, by using photoresist.
[0056] The method for implanting arsenic ions into polycrystalline silicon of the present embodiment can be applied to any semiconductor device that requires implanting arsenic ions into polycrystalline silicon material, for example, in the preparation process of CMOS devices, the preparation process of SGT devices, the preparation process of super junction devices, the preparation process of trench gate MOS devices, the preparation process of BCD devices, the preparation process of memory devices, and the like.
[0057] The effect of the method for implanting arsenic ions into polysilicon of this embodiment will be described below by taking the preparation process of a CMOS device as an example.
[0058] When manufacturing CMOS devices, a gate first process is generally used to first prepare the gate (including the gate dielectric layer and the gate polysilicon layer), and then form the source and drain. Figure 3 As shown, an NMOS region 100 and a PMOS region 101 are formed on a semiconductor substrate 10, and respective gates are formed on the NMOS region 100 and the PMOS region 101, respectively, including a gate dielectric layer 16, a polysilicon layer 11, and a gate sidewall 12. In the process of performing ion implantation on the source / drain region 13 of the NMOS region 100 to form a source / drain, there is generally an arsenic ion implantation process. When performing arsenic ion implantation on the source / drain region 13 of the NMOS region 100, arsenic ion implantation is also performed on the polysilicon layer 11 of the gate of the NMOS region 100. Performing the pre-doping process on the polysilicon layer 11 of the gate of the NMOS region 100 can reduce the polycrystalline depletion effect of the NMOS tube. In the process of the arsenic ion implantation, a photoresist 14 is used to shield the surface of the PMOS region 101, including the gate on the PMOS region 101, to prevent the arsenic ions from being implanted into the region.
[0059] like Figure 4 As shown, only arsenic ions are used to perform ion implantation on the polysilicon layer 11 on the NMOS region 100. It is found that the arsenic ions implanted into the polysilicon layer 11 on the NMOS region 100 will diffuse into the polysilicon layer 11 on the adjacent PMOS region 101 to form a diffusion region 20, and this phenomenon is more serious after heat treatment, which will cause the polysilicon layer 11 on the PMOS region 101 to be unevenly doped after the corresponding P-type doping is completed, and the doping concentration of part of the polysilicon layer 11 (i.e., the diffusion region 20) is reduced, which will further cause the performance of the device to be reduced.
[0060] like Figure 5 The figure shows an ideal state after arsenic ions are implanted into the polysilicon layer 11 on the NMOS region 100 and heat treated. The arsenic ions in the polysilicon layer 11 on the NMOS region 100 will not diffuse into the polysilicon layer 11 on the PMOS region 101.
[0061] Here, 1. Arsenic ions are used alone to perform ion implantation on the polysilicon layer 11 on the NMOS region 100; 2. Arsenic ions and carbon ions with an ion implantation angle of 45° are used to perform ion implantation on the polysilicon layer 11 on the NMOS region 100; 3. Arsenic ions and carbon ions with an ion implantation angle of 25° are used to perform ion implantation on the polysilicon layer 11 on the NMOS region 100. Here, the energy of carbon ion implantation is 9 KeV, and the concentration of carbon ion implantation is 1E14. After heat treatment, Figures 6 to 8As shown, the measurement found that the width of the polysilicon layer 11 where the arsenic ions diffused to the adjacent PMOS region 101 was 66nm-50nm-48nm, respectively. This shows that the ion implantation method of carbon co-implantation in this embodiment can effectively inhibit the diffusion of arsenic ions.
[0062] In summary, the method for implanting arsenic ions into polycrystalline silicon of the present invention adds a step of implanting carbon ions when implanting arsenic ions into the polycrystalline silicon layer. When carbon atoms enter the polycrystalline silicon layer, they replace silicon atoms to form carbon-silicon bonds. Since the radius of carbon atoms is smaller than the radius of silicon atoms and the radius of arsenic atoms, the distance between lattice points is reduced, and the silicon-silicon bonds around the arsenic atoms are replaced by carbon-silicon bonds. The bond length of carbon-silicon bonds is small, which causes the shrinkage and distortion of the surrounding lattices, making the vacancies for the migration of arsenic atoms smaller, thereby preventing arsenic ions with larger atomic radius from passing through, which is equivalent to the closing of a fishing net. The effect is to trap the arsenic ions and prevent them from passing through. At the same time, since the bond energy of the carbon-silicon bond is greater than the bond energy of the silicon-silicon bond, the potential barrier of the arsenic ion vacancy migration is further increased, and the difficulty of the arsenic ion vacancy migration is increased, and finally the diffusion of the arsenic ions in the silicon material is effectively reduced; furthermore, since the main body of the ion implantation is polycrystalline silicon, its crystal orientation is different in various directions, so the carbon ions in the arsenic ion implantation method in polycrystalline silicon can produce an equivalent diffusion inhibition effect on the arsenic ions in various directions in the polycrystalline silicon, that is, it can produce a diffusion inhibition effect in both the longitudinal direction and the lateral direction. Therefore, the present invention effectively overcomes various shortcomings in the prior art and has a high industrial utilization value.
[0063] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.
Claims
1. A method for implanting arsenic ions into polycrystalline silicon, characterized in that: The method comprises: Providing a semiconductor substrate, on which a polycrystalline silicon layer is formed; Performing ion implantation of arsenic ions and carbon ions in a predetermined area of the polysilicon layer; A heat treatment process is performed on the polysilicon layer after the ion implantation.
2. The method for implanting arsenic ions into polycrystalline silicon according to claim 1, characterized in that: Arsenic ions are implanted into the polysilicon first, and then carbon ions are implanted into the polysilicon; or carbon ions are implanted into the polysilicon first, and then arsenic ions are implanted into the polysilicon.
3. The method for implanting arsenic ions into polycrystalline silicon according to claim 1, characterized in that: The ion implantation depth of carbon ions is not less than the ion implantation depth of arsenic ions.
4. The method for implanting arsenic ions into polycrystalline silicon according to claim 3, characterized in that: The ion implantation depth of carbon ions is consistent with the ion implantation depth of arsenic ions.
5. The method for implanting arsenic ions into polycrystalline silicon according to claim 1, characterized in that: The ion implantation angle of carbon ions is not less than that of arsenic ions, and the ion implantation angle is the angle between the ion implantation direction and the surface normal of the polysilicon layer.
6. The method for implanting arsenic ions into polycrystalline silicon according to claim 5, characterized in that: The ion implantation angle of carbon ions is not greater than 60°.
7. The method for implanting arsenic ions into polycrystalline silicon according to claim 1, characterized in that: The heat treatment is performed on the polysilicon layer after ion implantation through a rapid thermal annealing process.
8. The method for implanting arsenic ions into polycrystalline silicon according to claim 7, characterized in that: The rapid thermal annealing process includes laser annealing and / or spike annealing.
9. The method for implanting arsenic ions into polycrystalline silicon according to claim 1, characterized in that: When arsenic ions and carbon ions are implanted, a photoresist layer is provided in non-preset areas of the polysilicon layer for blocking.
10. The method for implanting arsenic ions into polycrystalline silicon according to claim 1, characterized in that: The method for implanting arsenic ions into polysilicon is suitable for the preparation process of CMOS devices.