JP3769444B2 - Ion implanter - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an ion implantation apparatus and an ion implantation method. In particular, the present invention relates to an ion implantation apparatus and an ion implantation method in which the apparatus operating rate is improved by suppressing the adhesion of dirt to a path for extracting ions from an ion generation source.
[0002]
[Prior art]
FIG. 5 is a schematic diagram showing a conventional ion implantation apparatus. The ion implantation apparatus includes an ion source 31 where ionization is performed, a cylinder box 35, and the like. An arc chamber 32 and a vaporizer 33 are provided inside the ion source 31, and an inert gas cylinder 82 such as Ar and a source gas cylinder 81 are installed inside a cylinder box 35 outside the ion source 31.
[0003]
Next, the operation will be described.
[0004]
Two methods are mainly used as a method of supplying the gas into the arc chamber 32. One is a method in which a solid material filled in a vaporizer 33 installed in the ion source 31 is vaporized by a heater (not shown) and supplied to the arc chamber 32. In the other one, a raw material gas cylinder 81 installed in an external cylinder box 35 is supplied into the arc chamber 32 through electromagnetic valves 63 and 64 connected to the gas introduction pipe 34 and a mass flow controller (flow rate controller) 72. It is a method to do.
[0005]
The ion source gas thus supplied into the arc chamber 32 is ionized by collision of electrons generated from a filament (not shown) in the arc chamber 32. The ions are extracted by an extraction electrode (not shown), accelerated by an acceleration electrode (not shown), and then a desired ion is selected by a mass analyzer (not shown), and the ions are applied to the wafer. Injected.
[0006]
By the way, in the ion implantation apparatus, it is necessary to periodically remove the inner wall of the vacuum chamber of the ion beam orbit inside the ion implantation apparatus including the arc chamber 32 to remove the conductive solid (dirt) inside the apparatus. As a specific method, the ion implantation production work is temporarily stopped, and argon gas is supplied to the ion generation source from a dedicated argon gas introduction system (inert gas cylinder 82, electromagnetic valves 61 and 62, mass flow controller 71). There is a method of introducing, ionizing it, and removing deposits by sputtering. As another method, there is a method in which the vacuum of the ion implantation apparatus is broken and the material is removed by decomposition cleaning over a long period of time.
[0007]
The reason why the cleaning must be performed in this way is as follows.
[0008]
This is for preventing discharge at a high voltage application site in the ion implantation apparatus and preventing apparatus failure in advance. Further, this is because it is easy to generate an arc in the arc chamber 32 when the solid material is vaporized by the vaporizer 33 and used. In addition, the conductive film adheres to the arc chamber 32, the filament in the arc chamber, and the insulator for floating the extraction electrode. Then, the filament causes dielectric breakdown, becomes unstable, and further causes abnormal discharge, so that the desired ions cannot be accelerated. As a result, the characteristics of the semiconductor device are changed by interrupting ion implantation or not performing appropriate ion implantation. Therefore, it is necessary to periodically clean the inner wall of the vacuum chamber of the ion beam trajectory inside the ion implantation apparatus.
[0009]
[Problems to be solved by the invention]
In the conventional ion implantation apparatus, as described above, it is necessary to temporarily stop the operation between production operations of ion implantation and perform cleaning with inert gas ions as a maintenance operation. For this reason, there is a problem that the apparatus operating rate is lowered due to the cleaning work time, and the production efficiency is remarkably lowered.
[0010]
On the other hand, as disclosed in JP-A-3-163735, in order to prevent the inner wall of the ion introduction path from being oxidized or contaminated with carbon by the ion source gas of O, C, CO, There is a method of cleaning the inside of the apparatus while performing ion implantation by mixing 20 to 80% by volume of inert argon. However, the method of mixing argon described in JP-A-3-163735 cannot be applied to the conventional ion implantation method for the following reason.
[0011]
In the conventional ion implantation method, a gas obtained by diluting boron trifluoride BF ₃ , phosphine PH ₃ , arsine AsH ₃ or the like with an active gas such as hydrogen is used as an ion source gas for impurities. In the case of ion implantation using this gas, 20 to 80 vol% argon is mixed with the gas because the mixing ratio of argon is too large. For this reason, in the ion implantation of boron trifluoride, phosphine, arsine, etc., the concentration of the target ions is reduced, and the processing capability of the ion implantation is remarkably lowered.
[0012]
Under such circumstances, it is possible to perform ion implantation of desired impurities such as boron, phosphine, and arsine, and at the same time, it is possible to prevent and remove the conductive film from adhering to the inner wall of the ion implantation path. There is a need for an ion implantation method that can improve current collection. In addition, the quality of the semiconductor device can be improved by stabilizing the characteristics of the semiconductor device by reducing the discharge factor at the site where the high voltage is applied, and by reducing the frequency of the conductive deposit removal work performed by stopping the ion implantation. Realization of stability and productivity improvement is required.
[0013]
The present invention has been made in consideration of the above-described circumstances, and its purpose is to improve the device operation rate by suppressing contamination from adhering to the path for extracting ions from the ion source. An apparatus and an ion implantation method are provided.
[0014]
[Means for Solving the Problems]
An ion implantation apparatus according to the present invention includes an ion generation source that generates ions to be implanted into a substrate of a semiconductor device, source gas supply means that supplies a source gas to the ion generation source, and ions generated by the ion generation source. A mass analyzer that separates predetermined ions , and the source gas containing any one of BF ₃ , PH ₃ , AsH ₃ , GeF ₄ , and SiF ₄ is greater than 0 Vol% and equal to or less than 10 Vol% The inert gas is a mixed gas to which is added in advance.
[0015]
In the above ion implantation apparatus, by using a mixed gas in which an inert gas of more than 0 Vol% and not more than 10 Vol% is previously added to the source gas, the inert gas is also plasma by collision of thermoelectrons in the ion generation source. In this state, ions are generated together with the raw material gas. As a result, deposits (conductive solids) adhering to the ion path for injecting ions generated from the ion generation source into the substrate can be removed and suppressed by the cleaning effect by sputtering.
[0016]
Moreover, the introduction path | route which introduces gas into an ion generation source can be simplified by using mixed gas to which inert gas of more than 0 Vol% and 10 Vol% or less is added beforehand as source gas. .
[0017]
The ion implantation apparatus of the present invention includes an ion generation source that generates ions to be implanted into a substrate of a semiconductor device, source gas supply means that supplies a source gas to the ion generation source, and ions generated by the ion generation source. A mass analyzer that separates predetermined ions, and an inert gas supply means that supplies the ion generation source with an inert gas that is greater than 0 Vol% and less than or equal to 10 Vol% with respect to the source gas. The predetermined ions are ions of the inert gas, and the source gas includes any of BF ₃ , PH ₃ , AsH ₃ , GeF ₄ , and SiF ₄ .
[0018]
In the above ion implantation apparatus, it is possible to reduce the frequency of cleaning with argon gas and the decomposition cleaning around the ion generation source and the extraction electrode, which are performed individually by frequently stopping the apparatus. For this reason, the production capacity of the semiconductor device can be easily and dramatically improved.
[0019]
In addition, by mixing the raw material gas and the inert gas from different systems, the amount of the raw material gas or the inert gas can be adjusted to adjust the mixing concentration within the range of more than 0 vol% and less than 10 vol%. It becomes possible to change to.
[0020]
The ion implantation apparatus according to the present invention is characterized in that the source gas supply means has a source gas cylinder filled with source gas.
[0021]
The ion implantation apparatus according to the present invention is characterized in that the source gas supply means has a plurality of types of source gas cylinders.
[0022]
The ion implantation apparatus according to the present invention is characterized in that the source gas supply means includes a vaporizer filled with a solid source for generating source gas.
[0023]
In the ion implantation apparatus, a predetermined amount of inert gas is introduced into the arc chamber together with the vaporized gas from the solid material in order to obtain the same effect even when the solid material is vaporized. .
[0024]
In any of the above ion implantation apparatuses, the inert gas is an argon gas.
[0026]
Further, in order to obtain the same effect even when the solid material is vaporized, a predetermined amount of inert gas is introduced into the arc chamber together with the vaporized gas from the solid material.
[0027]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
[0028]
FIG. 1 is a schematic diagram showing an ion implantation apparatus according to a first embodiment of the present invention.
[0029]
As shown in FIG. 1, this ion implantation apparatus applies an electric field and a magnetic field in an arc chamber 5 and generates plasma by thermoelectrons generated from a filament 7 and an ion source gas introduced from a gas introduction tube 4. .
[0030]
An inert gas cylinder 2 such as argon is connected to a gas introduction pipe 4 via a solenoid valve 16 and a mass flow controller 3. A boron trifluoride (BF ₃ ) ion source gas cylinder 1 a is connected to a gas introduction pipe 4 through a solenoid valve 16 and a mass flow controller 3. A hydrogen-based phosphine ion source gas cylinder (PH ₃ / H ₂ ) 1 b is connected to a gas introduction pipe 4 via a solenoid valve 16 and a mass flow controller 3. At this time, the mixing ratio of PH ₃ in the ion source gas cylinder 1b is 15 to 50%. The arsine ion source gas cylinder (AsH ₃ / H ₂ ) 1 c is connected to the gas introduction pipe 4 through the electromagnetic valve 16 and the mass flow controller 3. The mixing ratio of AsH ₃ in the ion source gas cylinder 1c at this time is about 15%. The gas introduction pipe 4 is connected to the arc chamber 5. In other words, a mixed gas in which boron trifluoride is mixed with argon of 20 Vo1% or less, a mixed gas in which phosphine is mixed with argon of 20 Vo1% or less, or a mixed gas in which arsine is mixed with argon of 20 Vo1% or less are introduced into the gas. It is configured to be introduced into the arc chamber 5 through the tube 4. Further, when argon is mixed with boron trifluoride, phosphine, or arsine in the gas introduction tube 4, the mass flow controller 16 adjusts the flow rate of argon to be 20 Vo1% or less.
[0031]
A filament 7 is disposed in the arc chamber 5, and an electromagnet 6 is disposed outside the arc chamber 5. Therefore, the ion source gas introduced into the arc chamber 5 is in a plasma state due to the thermoelectrons generated from the filament 7 that has flowed current in a vacuum, the magnetic field of the electromagnet 6, and the electric field applied to the arc chamber 5 and the filament 7. It becomes 8 and is ionized.
[0032]
An extraction electrode 9, a mass analyzer 11, an ion accelerator 13, an ion scanning unit 14, and a semiconductor substrate 15 are arranged in this order along a trajectory through which an ion current 10 from which ions generated from the arc chamber 5 have been extracted passes.
[0033]
That is, the extraction electrode 9 for extracting the generated ions is installed at a position facing the slit of the arc chamber 5. By applying a negative potential to the extraction electrode 9, all the ionic current 10 generated through the slit is extracted.
[0034]
A mass analyzer 11 using a magnetic field for extracting only predetermined ions from the ion current 10 thus extracted is installed at a position facing the extraction electrode 9. When the ion current 10 passes through the mass analyzer 11, only predetermined ions are extracted, and other separated ions 12 including argon ions disappear in the mass analyzer 11.
[0035]
An ion acceleration unit 13 is arranged at a position facing the outlet of the extracted ions in the mass analyzer 11, and an ion scanning unit 14 is arranged next to the ion acceleration unit 13. A semiconductor substrate 15 is placed at a position facing the ion outlet in the ion scanning unit 14. Accordingly, ions extracted by the mass analyzer 11 are given predetermined acceleration energy in the ion acceleration unit 13 and are uniformly injected into the semiconductor substrate 15 through the ion scanning unit 14.
[0036]
According to the first embodiment, the mass flow controller is controlled so that the volume ratio of argon to any one of boron trifluoride, phosphine, and arsine is 20 Vo1% or less, and the resulting mixed gas is arced. Ion is introduced into the chamber 5 for ion implantation. Therefore, the argon mixed with the ion source gas in this way is ionized simultaneously with predetermined ions and other ions in the ion generation source, and is extracted by the extraction electrode 9. In the process, the ion source gas or ions ionized from the ion source gas are deposited, and the conductive film attached to the slits and insulators around the arc chamber 5 and the extraction electrode 9 is sputtered with argon while other ions are sputtered. Prevention and removal of deposits. As described above, since cleaning with inert gas ions can be performed at the same time as ion implantation, it is possible to extract ions without stopping the ion implantation work and performing the cleaning work as in the conventional ion implantation apparatus. Abnormal discharge does not occur at the electrode 9, and ions can be supplied at a stable voltage. Furthermore, since the acceleration energy of ions is stabilized, the characteristics of the semiconductor device can also be stabilized. As a result, the quality of the semiconductor device can be improved. Therefore, it is possible to prevent a reduction in the apparatus operation rate due to the cleaning work time, and it is possible to improve the production efficiency as compared with the conventional ion implantation apparatus. Since argon ions generated in the arc chamber 5 are then separated in the mass analyzer 11, only predetermined ions are introduced into the semiconductor substrate 15, and argon does not reach the substrate of the semiconductor device. Therefore, the same characteristics can be maintained without changing the characteristics of the conventional semiconductor device.
[0037]
The reason why the ratio of the inert gas such as argon mixed with the ion source gas such as boron trifluoride is set to 20 Vo1% or less is that it has been confirmed that the cleaning effect is sufficiently obtained at 20 Vo1% or less.
[0038]
2 shows a case where a mixed gas obtained by mixing boron trifluoride BF ₃ with argon is used as an ion source gas in the ion implantation apparatus shown in FIG. 1, and a mixed gas obtained by mixing phosphine with argon is used as an ion source gas. 2 is a graph showing the relationship between the argon mixing ratio and the amount of ion current when used in the ion implantation apparatus shown in FIG. In this figure, the vertical axis represents the ratio of the amount of current obtained by the mixed gas compared with the amount of ion current obtained by using the ion source gas not containing argon as 1.
[0039]
As shown in FIG. 2, in a mixed gas having an argon mixing ratio exceeding 20 Vo1%, the concentration of predetermined ions is about half or less compared to the case where the predetermined ion concentration is not mixed (mixing ratio 0 Vo1%). For this reason, if a mixed gas with an argon mixing ratio exceeding 20 Vo1% is used, cleaning with argon ions can be performed, but the ion implantation time increases, and conversely, the production efficiency decreases. Therefore, when the argon mixing ratio is 20 Vo1% or less, the argon cleaning effect can be exhibited while sufficiently securing the concentration of the predetermined ions. More preferably, the mixing ratio of argon is 10 Vo1% or less.
[0040]
In the first embodiment, an inert gas such as argon is used. However, the present invention is not necessarily limited to the inert gas, and other elements can be used as long as the sputtering effect can be expected. .
[0041]
Further, although BF ₃ , PH ₃ or AsH ₃ is used as the ion source gas, other ion source gases can be used, for example, GeF ₄ or SiF ₄ can be used.
[0042]
In the present embodiment, an inert gas cylinder 2 such as argon and ion source gas cylinders 1 a to 1 c are separately prepared in the ion implantation apparatus, and the flow rate of single argon gas from the inert gas cylinder 2 is controlled by the mass flow controller 3. The ion source gas is extracted from the ion source gas cylinder while controlling the flow rate by the mass flow controller 3, and both are mixed in the gas introduction pipe 4 immediately before the arc chamber 5. However, the present invention is not limited to this. It is also possible to mix by a mixing method. For example, it is possible to prepare a gas cylinder containing an ion source gas in which argon gas is mixed at 20 Vo1% or less in advance and arrange this gas cylinder in an ion implantation apparatus. In this case, the gas path can be simplified without requiring a single inert gas introduction system as in the present embodiment, so that an ion source gas with a stable mixing ratio can be provided easily. On the other hand, when argon gas is mixed from another system as in this embodiment, it is easy to arbitrarily change the argon concentration at 20 Vo1% or less, so that the ion current concentration and the cleaning effect can be appropriately controlled. It is possible to easily select an optimum argon mixing ratio corresponding to the ion implantation conditions and the state of the apparatus.
[0043]
FIG. 3 is a schematic diagram showing an ion implantation apparatus according to the second embodiment of the present invention, and is a configuration diagram mainly showing an ion source and a cylinder box. This ion implantation apparatus has a structure in which a source gas cylinder 83 to which a predetermined amount of an inert gas (argon gas) having a cleaning effect is added is installed in the cylinder box 35 instead of the source gas cylinder 81 shown in FIG.
[0044]
In the ion implantation apparatus configured as described above, ion implantation can be performed in the same manner as in the past, and a predetermined amount of gas from the inert gas addition source gas cylinder 83 is introduced into the gas via the electromagnetic valves 63 and 64 and the mass flow controller 72. A tube 34 supplies the arc chamber 32. In the arc chamber 32, both the desired source gas for ion implantation and the cleaning inert gas (argon gas) previously added to 20 Vol% or less are generated from electrons generated from a filament (not shown). It is ionized by collision.
[0045]
These ions are accelerated by an extraction electrode (not shown), and then separated and selected only to the desired ions by a mass analyzer (not shown). For this reason, ions by the gas added for cleaning are separated and removed here, and are not implanted into the wafer (semiconductor substrate). Therefore, the argon ions exhibit only an ion beam trajectory cleaning effect from the arc chamber 32 to the mass analyzer. Then, desired ions selected by the mass analyzer are implanted into the wafer.
[0046]
FIG. 4 is a diagram illustrating an example of an ion beam spectrum of an inert gas-added source gas separated by a mass analyzer. Here, an example in which a predetermined amount of inert gas Ar is added to the source gas PH ₃ is shown, but the desired ions ³¹ P ⁺ and the cleaning ions ⁴⁰ Ar ⁺ are separated by a magnetic field. ⁴⁰ Ar ^+, which is a cleaning ion, is never implanted into the wafer.
[0047]
Similarly, when a vaporized gas from a solid material is used, a predetermined amount of inert gas together with the vaporized gas from the vaporizer 33 is put into the arc chamber 32 shown in FIG. 61 and 62, the mass flow controller 71, and the gas introduction pipe 4 are supplied. For this reason, the same action is performed in this case.
[0048]
In addition, in any use of the gas cylinder and the vaporizer, the example in which the inert gas Ar is added has an effect of easily generating an arc in the arc chamber 32.
[0049]
As described above, according to the present embodiment, by using the inert gas-added source gas cylinder 83, the inside of the apparatus is cleaned simultaneously with the ion implantation operation with desired ions, which has been performed separately from the production operation so far. In addition, the cleaning operation time by the inert ions becomes unnecessary, and the apparatus operating rate can be improved.
[0050]
When a solid material such as the vaporizer 33 is used, the same effect can be obtained by supplying a predetermined amount of argon gas from the inert gas cylinder 82 into the arc chamber 32. In addition, when Ar is used as the inert gas in both the gas cylinder and the solid raw material, there is an effect that an arc is easily generated in the arc chamber.
[0051]
【The invention's effect】
As described above, according to the present invention, a gas mixture obtained by mixing an ion source gas with an argon gas of 20 Vo1% or less is supplied to the ion generation source. Therefore, it is possible to provide an ion implantation apparatus and an ion implantation method in which the apparatus operating rate is improved by suppressing the adhesion of dirt to the path for drawing ions from the ion generation source.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing an ion implantation apparatus according to a first embodiment of the present invention.
2 is a graph showing the argon mixing ratio of ion source gas used in the ion implantation apparatus shown in FIG. 1 and the concentration of ion current.
FIG. 3 is a schematic diagram showing an ion implantation apparatus according to a second embodiment of the present invention.
FIG. 4 is a diagram showing an example of an ion beam spectrum of an inert gas-added source gas separated by a mass analyzer.
FIG. 5 is a schematic view showing a conventional ion implantation apparatus.
[Explanation of symbols]
1a to 1c ion source gas cylinder 2 inert gas cylinder such as argon 3 mass flow controller 4 gas introduction pipe 5 arc chamber 6 electromagnet 7 filament 8 plasma region 9 extraction electrode 10 extracted ion current 11 mass analyzer 12 separated containing argon ions Other ions 13 Ion accelerator 14 Ion scanning unit 15 Semiconductor substrate 16 Electromagnetic valve 31 Ion source 32 Arc chamber 33 Vaporizer 34 Gas introduction pipe 35 Cylinder box 61-64 Electromagnetic valve 71, 72 Mass flow controller 81 Raw material gas cylinder 82 Inert gas cylinder 83 Inert gas addition source gas cylinder

Claims (6)

An ion generation source for generating ions to be implanted into a substrate of a semiconductor device;
Source gas supply means for supplying source gas to the ion generation source;
A mass analyzer for separating predetermined ions among the ions generated by the ion generation source,
The source gas containing any one of BF ₃ , PH ₃ , AsH ₃ , GeF ₄ , and SiF ₄ is preliminarily added with an inert gas of more than 0 Vol% and not more than 10 Vol%, and the predetermined ions Is an ion of the inert gas. An ion generation source for generating ions to be implanted into a substrate of a semiconductor device;
Source gas supply means for supplying source gas to the ion generation source;
A mass analyzer for separating predetermined ions out of ions generated by the ion generation source;
The ion generation source includes an inert gas supply means for supplying an inert gas of more than 0 Vol% and 10 Vol% or less with respect to the source gas,
The predetermined ion is an ion of the inert gas, and the source gas includes any one of BF ₃ , PH ₃ , AsH ₃ , GeF ₄ , and SiF ₄ . 3. The ion implantation apparatus according to claim 2, wherein the source gas supply means includes a source gas cylinder filled with the source gas. 4. The ion implantation apparatus according to claim 3, wherein the source gas supply means has a plurality of types of source gas cylinders. 3. The ion implantation apparatus according to claim 2, wherein the source gas supply means includes a vaporizer filled with a solid source for generating source gas. 6. The ion implantation apparatus according to claim 1, wherein the inert gas is an argon gas.

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