CN108091565B - Rapid thermal annealing method - Google Patents
Rapid thermal annealing method Download PDFInfo
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- CN108091565B CN108091565B CN201711329238.9A CN201711329238A CN108091565B CN 108091565 B CN108091565 B CN 108091565B CN 201711329238 A CN201711329238 A CN 201711329238A CN 108091565 B CN108091565 B CN 108091565B
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
- H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having at least one potential-jump barrier or surface barrier, e.g. PN junction, depletion layer or carrier concentration layer
- H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having at least one potential-jump barrier or surface barrier, e.g. PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic System or AIIIBV compounds with or without impurities, e.g. doping materials
- H01L21/30—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26
- H01L21/324—Thermal treatment for modifying the properties of semiconductor bodies, e.g. annealing, sintering
Abstract
The invention provides a rapid thermal annealing method, which comprises the following steps: providing a substrate, wherein impurity ions are injected into the substrate, the surface of the substrate is provided with a naturally formed growth layer, and when a rapid thermal annealing process is performed on the substrate, a preset gas is introduced into a rapid thermal processing machine to enable the gas to react with the substrate so as to increase the thickness of the growth layer, so that the increased growth layer is used for preventing the impurity ions in the substrate from overflowing, and the condition that the injected impurity ions overflow from the surface of the substrate during rapid thermal annealing due to the fact that the thickness of the growth layer is too small is avoided; and the situation that operators need to stop due to the overflow of injected ions and perform problem analysis and troubleshooting on a machine or a process is reduced by adopting the rapid thermal annealing method, and the production efficiency is improved.
Description
Technical Field
The invention relates to the field of semiconductor manufacturing, in particular to a rapid thermal annealing method.
Background
The annealing process is an indispensable process in the field of semiconductor manufacturing, and mainly aims to repair damage to the surface of a silicon wafer after ion implantation due to high-energy ion bombardment and simultaneously enable implanted impurity ions to enter lattice positions so as to activate the implanted impurity ions. With the progress of the annealing process, the rapid thermal annealing technology gradually replaces the traditional furnace tube annealing technology, and has the advantages of small thermal budget, less contamination and short annealing time.
Generally, before ion implantation, a masking layer is often formed on the substrate surface, which can prevent channel effect during ion implantation and prevent implanted ions from overflowing from the substrate surface during annealing, however, some substrate materials, such as monocrystalline silicon, have a natural growth layer, such as a silicon oxide layer, formed on the surface thereof under natural conditions, which can also have the effect of the masking layer, but the thickness of the naturally grown growth layer is not controllable, so the masking layer is usually regrown after the naturally grown growth layer is removed, and in this application, in order to simplify the process steps, the growth layer is tried to be used as the masking layer, so that when the thickness is too small, the implanted impurity ions are likely to overflow during high-temperature annealing, and thus the actual concentration standard of the implanted impurity ions is not met. Meanwhile, in the subsequent process, when the sheet resistance of the substrate is measured, ions overflow the surface of the substrate, the sheet resistance becomes large and exceeds the original standard value, and further an engineer may misjudge that the machine has a problem, and the machine needs to be stopped to check the problem, thereby bringing unnecessary trouble.
Disclosure of Invention
The invention provides a rapid thermal annealing method, which aims to solve the problems that in the prior art, when a growth layer naturally formed on the surface of a substrate is used as a masking layer, the thickness is uncontrollable, and when the thickness is too small, ions overflow can be caused, and is characterized by comprising the following steps:
providing a substrate, wherein impurity ions are implanted into the substrate, and the surface of the substrate is provided with a naturally formed growth layer;
performing a rapid thermal annealing process on the substrate by using a rapid thermal processing machine; wherein the content of the first and second substances,
and in the process of executing the rapid thermal annealing process, introducing preset gas, wherein the gas can react with the substrate to increase the thickness of the growth layer, so that the added growth layer is used for preventing the impurity ions in the substrate from overflowing.
Optionally, the material of the substrate is monocrystalline silicon.
Optionally, the growth layer is a silicon oxide layer.
Optionally, the gas is oxygen.
Optionally, the flow rate of the predetermined gas is 0.3cm3/s～1cm3/s。
Optionally, the rapid thermal annealing method further includes:
the sheet resistance measurements were taken of the substrates after the rapid thermal annealing process.
According to the rapid thermal annealing method provided by the invention, when the rapid thermal annealing process is carried out on the substrate with the naturally formed growth layer, the preset gas is introduced so that the gas can react with the substrate to increase the thickness of the growth layer, and the condition that impurity ions injected during the rapid thermal annealing overflow from the surface of the substrate due to the fact that the thickness of the growth layer is too small is avoided. And the rapid thermal annealing method provided by the invention can avoid the condition that operators misjudge due to ion overflow, and effectively improves the production efficiency.
Drawings
Fig. 1 is a schematic flow chart of a rapid thermal annealing method according to an embodiment of the present invention.
Detailed Description
The rapid thermal annealing method and the semiconductor substrate forming method according to the present invention will be described in further detail with reference to the accompanying drawings and specific embodiments. The advantages and features of the present invention will become more apparent from the following description. It is to be noted that the drawings are in a very simplified form and are not to precise scale, which is merely for the purpose of facilitating and distinctly claiming the embodiments of the present invention.
Fig. 1 is a schematic flow chart of an annealing method provided in an embodiment of the present invention, and specifically referring to fig. 1, the embodiment provides a rapid thermal annealing method, including the following steps:
firstly, step S1 is executed to provide a substrate, wherein the substrate is implanted with impurity ions, and the surface of the substrate has a naturally formed growth layer;
in this embodiment, as a preferable mode, the material of the substrate is, for example, monocrystalline silicon, a growth layer grows on the surface of the monocrystalline silicon under natural conditions, and specifically, when the monocrystalline silicon is exposed to air at room temperature, that is, in an atmosphere containing oxygen, a natural oxide film, that is, a silicon oxide layer, is immediately formed on the surface of the monocrystalline silicon. Furthermore, the growth layer can be used as a masking layer in the rapid thermal annealing process, and the function of inhibiting the overflow of the implanted impurity ions is achieved. Meanwhile, in the ion implantation process, the oxide layer can also reduce the situation that the junction depth is too large due to too deep ion implantation caused by the channel effect. However, since the thickness of the growth layer grown under natural conditions is not controllable, there is a possibility that the diffusion of the implanted impurity ions is not blocked due to an excessively small thickness of the growth layer during high-temperature thermal annealing, so that the implanted ions overflow from the substrate surface, and the concentration and junction depth of the implanted impurity ions are also affected.
Next, step S2 is performed to perform a rapid thermal annealing process on the substrate by using a rapid thermal processing tool;
it should be noted that, in the prior art, when performing a rapid thermal annealing process on a substrate, such as a monocrystalline silicon substrate, besides introducing oxygen in a preparation process for preparing an oxide layer, in other cases, a gas such as nitrogen is generally selected to be introduced to remove oxygen in the atmosphere, so as to prevent the substrate from undergoing an oxidation reaction in an oxygen atmosphere, and the introduced gas such as nitrogen can make the surface of the substrate heated more uniformly.
Then, step S3 is performed, during the rapid thermal annealing process, a predetermined gas is introduced, and the gas can react with the substrate to increase the thickness of the growth layer, so as to prevent the impurity ions in the substrate from overflowing by the increased growth layer.
In the embodiment, aiming at the problem that the thickness of a growth layer naturally formed on a substrate, such as a monocrystalline silicon substrate, is too small, so that implanted impurity ions diffuse and penetrate through the growth layer in a high-temperature environment of rapid thermal annealing, and then implanted ions overflow from the surface of the substrate, in the process of rapid thermal annealing, a predetermined gas is introduced into a reaction furnace, and the gas can react with the substrate to increase the thickness of the growth layer, so that the condition that the implanted ions overflow due to the insufficient thickness of the growth layer is reduced.
As a preferable scheme in this embodiment, the predetermined gas is introduced, including but not limited to oxygen. The oxygen can react with the silicon single crystal substrate in the embodiment at a high temperature, so that a silicon oxide film layer is formed on the surface of the silicon single crystal substrate, the problem that the thickness of an oxide layer naturally formed by the silicon single crystal is too small is solved, and the effect of preventing injected ions from overflowing by the growth layer can be improved during high-temperature thermal annealing.
It should be noted that, in the prior art, it is determined whether the thickness of the growth layer is enough to prevent most of the impurity ions from overflowing, for example, by aiming at the implantation conditions required under the process, including: the implantation concentration, the implantation junction depth, the type of the implanted ions, and the like are tested and measured for a plurality of times, so that the optimal thickness of the masking layer capable of preventing the ions from overflowing under the required implantation conditions is obtained, that is, the increased growth layer in the embodiment needs to reach the optimal thickness to obtain a better effect of preventing the impurity ions from overflowing.
And, combining the specific conditions in this example, through many experiments and sensitivity analysis, it was found that the flow rate was 0.3cm during the rapid thermal annealing3/s～1cm3The oxygen/s can ensure that the thickness of the growth layer after the silicon single crystal substrate is increased in the embodiment can achieve the effect of effectively inhibiting the overflow of implanted ions, and simultaneously, the situation of inaccurate measurement and erroneous judgment caused by overlarge thickness of the growth layer during the subsequent square resistance measurement can be prevented.
As another preferred embodiment, the rapid thermal annealing method provided by the present invention further includes: the sheet resistance measurements were taken of the substrates after the rapid thermal annealing process.
It should be noted that, in the prior art, to determine whether the thickness of the growth layer reaches a level that can prevent the impurity ions from overflowing, a more direct method is to measure the sheet resistance value of the growth layer. The known calculation formula Rs of the sheet resistance is ρ/t, where Rs represents the sheet resistance, ρ represents the resistivity of the film to be measured, and t represents the thickness of the film to be measured, it is understood that the sheet resistance is proportional to the resistivity of the film to be measured and inversely proportional to the thickness of the film to be measured. Furthermore, under the condition that the resistivity of the measured film layer is determined, the larger the sheet resistance is, the smaller the thickness of the measured film layer is, and further, in this embodiment, whether the thickness of the growth layer reaches a degree that can prevent most impurity ions from overflowing can be determined, and whether the sheet resistance is smaller than the sheet resistance required by the process can be further determined.
And after the rapid thermal annealing method provided by the invention is adopted, the problem of ion overflow in the rapid thermal annealing process caused by the over-small thickness of the growth layer can be avoided, and further, when the square resistance of the substrate after the rapid thermal annealing is measured, the condition that the square resistance is too large caused by the above problem can be eliminated, so that the condition that an operator stops to check due to the generation of the above problem is avoided, and the effect of improving the production efficiency is achieved.
In addition, in order to more intuitively and specifically embody the advantages and features of the rapid thermal annealing method provided by the present invention, the present embodiment also exemplifies 2 process conditions and test results in the actual production process.
First, for example, when arsenic ion implantation is performed on the silicon substrate, the implantation process conditions are set, for example, the implantation energy is 50keV, and the implantation dose is 1 × 1015atoms/cm3Table 1 shows the test results of arsenic ion implantation without the rapid thermal annealing method provided in the present invention, and referring to table 1, the ooc (out of control) in the test results column indicates that the product quality is out of control.
TABLE 1
As can be seen from table 1, for example, when the sheet resistance of the growth layer exceeds 125 Ω, i.e., exceeds the regulatory range of 125 Ω in the actual process, it cannot be guaranteed that no ion overflow occurs. And, it can also be seen from Table 1 that the thickness of the grown layer formed under natural conditions is not controllable when the grown layer is smaller than
In the case of (3), an abnormal situation in which ion overflow occurs easily occurs.
Aiming at the situation, the rapid thermal annealing method provided by the invention is adopted, and the flow of the introduced preset gas is properly adjusted, so that the substrate reacts with the gas to increase the thickness of the growth layer, and the thickness of the growth layer is ensured to be larger than that of the growth layer
For example control at
On the other hand, specifically, when the substrate is a single crystal silicon substrate, the flow rate of the introduced oxygen gas is controlled to be 0.6cm3S, the thickness of the growth layer can be controlled to increase
And the abnormal situation of ion overflow can be avoided.
Similarly, for example, when fluorine ion implantation is performed on the silicon substrate, the implantation process conditions are set, for example, the implantation energy is 50keV, and the implantation dose is 1 × 1015atoms/cm3Table 2 shows the test results of implanting fluorine ions without using the rapid thermal annealing method provided in the present invention, and referring to table 2, ooc (out of control) in the test result column indicates that the product quality is out of control, and oos (out of specification) indicates that the data is out of standard.
TABLE 2
As can be seen from table 2, for example, when the sheet resistance of the growth layer exceeds 137 Ω, for example, i.e., exceeds the regulatory range of 137 Ω in the actual process, it cannot be guaranteed that no ion overflow occurs. And, when the growth layer is smaller than
In this case, ion overflow is likely to occur.
Correspondingly, a similar approach can be used, when the substrate is a monocrystalline silicon substrate, for example by controlling the flow of oxygen gas introduced to be 0.6cm3S, controlling the thickness of the growth layer to increase
And the abnormal situation of ion overflow can be avoided.
It should be noted that, according to different implantation conditions in the actual process, one skilled in the art can change and adjust the predetermined gas type and flow rate to change and control the thickness of the growth layer after the growth layer is increased, so as to achieve the purpose of preventing ion overflow.
Finally, after the rapid thermal annealing method provided by the invention is adopted, the problem of ion overflow in the rapid thermal annealing process caused by the over-small thickness of the growth layer can be avoided, and further, when the square resistance of the substrate after the rapid thermal annealing is measured, the condition that the square resistance is too large caused by the above problem can be eliminated, so that the condition that an operator stops to perform troubleshooting due to the generation of the above problem is avoided, and the effect of improving the production efficiency is achieved.
In summary, the present invention provides a rapid thermal annealing method, wherein when a rapid thermal annealing process is performed on a substrate, a predetermined gas is introduced into a rapid thermal processing machine to react with the substrate to increase the thickness of the growth layer, thereby avoiding the situation that impurity ions injected during the rapid thermal annealing overflow from the surface of the substrate due to an excessively small thickness of the growth layer, so that the doping concentration of the substrate is within a controllable range; and by adopting the rapid thermal annealing method, the problem of overlarge square resistance on the surface of the substrate caused by the overflow of the injected ions can be solved, the conditions that operators need to stop the machine and analyze and troubleshoot the machine or the process due to the overflow of the injected ions are reduced, and the production efficiency is improved.
It will be apparent to those skilled in the art that various changes and modifications may be made in the invention without departing from the spirit and scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.
Claims (4)
1. A rapid thermal annealing method, comprising:
providing a substrate, wherein impurity ions are implanted into the substrate, and the surface of the substrate is provided with a naturally formed growth layer;
performing a rapid thermal annealing process on the substrate by using a rapid thermal processing machine; wherein the content of the first and second substances,
introducing oxygen in the process of performing the rapid thermal annealing process, wherein the flow of the oxygen is 0.3cm3/s～1cm3(ii)/s, said oxygen being capable of reacting with said substrate to augment said growth layerA thickness to prevent the impurity ions in the substrate from overflowing with the increased growth layer.
2. The rapid thermal annealing method according to claim 1, wherein the material of the substrate is single crystal silicon.
3. The rapid thermal annealing method according to claim 2, wherein the growth layer is a silicon oxide layer.
4. The rapid thermal annealing method according to any one of claims 1 to 3, further comprising:
the sheet resistance measurements were taken of the substrates after the rapid thermal annealing process.
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| US7579654B2 (en) * | 2006-05-31 | 2009-08-25 | Corning Incorporated | Semiconductor on insulator structure made using radiation annealing |
| CN100585805C (en) * | 2008-10-10 | 2010-01-27 | 上海新傲科技有限公司 | The preparation method of the silicon substrate on the insulator |
| CN101789384B (en) * | 2009-01-23 | 2011-12-07 | 中芯国际集成电路制造(上海)有限公司 | Method for detecting annealing |
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