JPH07211279A - Ion implantation - Google Patents

Abstract

PURPOSE:To restrict the spread of a beam without lowering the beam current, and to even the characteristic inside of a target surface by setting a target at an electrical potential higher than the grounding electrical potential and lower than the electrical potential of a drawing electrode part. CONSTITUTION:Plasma is generated in an ion source 1 by the gas and various power source supplied from a high voltage unit power source.gas supplying unit 4, and dopant ion is generated. The dopant ion is accelerated and drawn by the high voltage applied from a drawing power source 5 to the source 1, namely, the extracting voltage(EXT voltage), and enters an analyzing magnet unit 6. The only required ion is selected in the analyzing magnet unit 6, and input to a scanning electrode unit 9 at a grounding electrical potential from an acceleration tube 8, and passes through it, holding the high kinetic energy. In the deceleration tube 13, the ion is decelerated by the external power source voltage (decelerating voltage), and enters an end station 10. Since the drawing voltage can be thereby raised, a large beam current is obtained, and spread of the beam can be restricted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ion implantation apparatus used for manufacturing a semiconductor device.

[0002]

2. Description of the Related Art In a semiconductor device manufacturing process, an ion implantation technique for implanting ions such as arsenic is used to form impurity regions such as source and drain electrodes of a transistor inside a semiconductor substrate. This ion implantation is performed by applying a high voltage (for example, about 30 kV) as an extraction voltage to extract ions from the ion source, and scanning the beam of the ions to inject the ions into a predetermined portion of the fixed target, or On the contrary, it is carried out by fixing the ion beam and scanning the target to inject it into a predetermined portion.

Incidentally, with the miniaturization of elements, it has become necessary to form fine source / drain patterns on a semiconductor substrate. A shallow diffusion layer is required to form such a fine pattern (electrode), but it is difficult to form a beam with high energy accelerated by a high voltage because ions are implanted in the deep portion of the semiconductor substrate. . Therefore, the ions are accelerated by an acceleration voltage lower than that of the conventional ion implantation device, and the shallow impurity region is formed by the ions having the low energy.

Conventionally, there have been the following two types of methods for implanting ions having such low energy. The first method is a variable method, in which a relatively low voltage (for example, about 3 kV) is applied by an extraction power source, and a required low energy is applied to extract ions. The second method is called a deceleration method, in which a high voltage is applied by an extraction power source, ions having a larger energy than required are extracted, and then the deceleration power source decelerates to a predetermined required energy by an accelerating tube. Is the way. Hereinafter, each method will be described.

FIG. 4 shows a schematic configuration of a conventional variable ion implantation apparatus. FIG. 4 shows between the portion of the ion implantation apparatus to which the extraction voltage is applied and the portion of the target (wafer) to which the ions are implanted.

In the figure, 1 is an ion source for supplying dopant ions such as arsenic, phosphorus and boron, 2 is an insulator (bushing) for insulating the ion source 1 to which an extraction voltage is applied, and 3 is from the ion source 1. Extraction electrode part for efficiently extracting ions, 4 is a high voltage part power / gas supply part for making gas or solid vapor in the ion source into a high-density plasma state by discharging, and 5 is a high voltage for extracting ions in plasma Is an extraction power source, 6 is an analysis magnet section for selecting only desired impurity ions by setting the strength of the magnetic field with an electromagnet, and 7 is a housing for accommodating the ion source 1 to the analysis magnet section 6 and at the same time a high potential. It is a high voltage pedestal that keeps. Reference numeral 8 denotes an accelerating tube for further accelerating ions as necessary, and 9 denotes a scanning electrode for scanning the ion beam accelerated by the accelerating tube 8 by electrostatic scanning in order to uniformly irradiate the fixed target with the ion beam. Reference numerals 10 and 10 denote end stations for accommodating and holding a target (wafer) (not shown) therein in order to irradiate the target with the ion beam from the scanning electrode unit 9. Reference numeral 15 is an insulator (insulator) that insulates the high-voltage pedestal 7, 16a and 16b are ground wires for setting the scanning electrode unit 9 and the end station 10 to a ground potential (GND potential), and 22 is an accelerating voltage to the accelerating tube 8. It is an acceleration power supply.

Next, the operation will be described. Plasma is generated in the ion source 1 by the gas and high voltage supplied from the high-voltage unit power supply / gas supply unit 4, and dopant ions such as arsenic, phosphorus, and boron are generated. These dopant ions are accelerated and extracted with energy of, for example, 30 keV by the high voltage applied to the ion source 1 from the extraction power source 5, and enter the analysis magnet unit 6. In the analysis magnet unit 6, only the necessary ions are selected by changing the strength of the magnetic field according to the extraction voltage and changing the orbital radius of the ions, and the ions are injected into the acceleration tube 8. And 30ke
When a high energy of V or more (for example, 100 keV) is required, the accelerating power source 22 further accelerates the accelerating tube 8 to have the required energy, and then the scan electrode unit 9 performs a predetermined scan to end the station 10. It is injected into a target (not shown) inside.

However, when low-energy implantation is performed by the variable-type ion implantation apparatus shown in FIG. 4, the extraction voltage must be low, but if this is done, the number of ions extracted from the ion source 1 will decrease and the ion will advance in space. The ion speed also decreases and the effective beam current value decreases. This is because the ion beams repel each other to spread the ion beam and reduce the number of ions passing through per unit time. Due to the small beam current, the throughput is deteriorated, the production efficiency is reduced, and further, the spread of the ion beam makes it impossible to uniformly irradiate the target surface, which causes a problem that characteristics are varied and deteriorated.

Therefore, a deceleration system is used to solve such a problem. Next, the deceleration method will be described. When performing low-energy injection in this method, the desired voltage (eg 3kV) is directly applied to the ion source by the deceleration power supply, and the normal acceleration power supply is separated from the high-voltage pedestal and the extraction power supply (eg 30kV) is used as the ion source. Apply. FIG. 5 shows an outline of the configuration of a conventional ion implanter using this deceleration method. Similar to FIG. 4, FIG. 5 shows a portion of the ion implanter between the portion to which the extraction voltage is applied and the portion of the target to which the ions are to be implanted.

In FIG. 5, an ion source 1, an insulating material 2, an extraction electrode section 3, a high voltage section power source / gas supply section 4, an extraction power source 5, an analysis magnet section 6, a high voltage pedestal 7, an acceleration tube 8, a scanning electrode. The section 9, the end station 10, the insulator 15, the ground wires 16a and 16b, and the acceleration power supply 22 are the same as those in FIG. Reference numeral 21 is a deceleration power supply for generating desired ion implantation energy.

FIG. 6 is a schematic view showing the arrangement of electrodes inside the deceleration type ion implanter shown in FIG.
1 is an electrode of the ion source 1, 72 and 73 are electrodes of the high-voltage pedestal 7, 81 is an electrode of the accelerating tube 8, and the electrodes 73 and 81 have the same potential as the high-voltage pedestal 7. Reference numeral 101 is a target held inside the end station 10.

FIG. 7 is a diagram for explaining the potential inside the deceleration type ion implanter. In the figure, as an example, a specific potential is entered, and the ion implantation energy is 3 keV and the extraction voltage (EXT) is 30 kV. With reference to the ground potential (GND), the potential of the electrode 71 is 3 kV,
The potential of the electrode 72 is -29 kV and the potential of the electrode 73 is -27 kV. The scan electrode unit 9, the end station 10 and the target 101 are grounded.

The voltage between the ground and the electrode 71 is the voltage finally given to the ions irradiated on the target, and is called the deceleration power supply voltage. In addition, the electrode 81 and the ground (GN
The voltage between D) is a voltage for further accelerating the extracted ions, and is called an acceleration voltage. in this case,
It will slow down here. Also, the electrode 71 and the electrode 7
The voltage between 3 (high voltage pedestal 7) is a voltage for extracting ions and is called an EXT (Extraction) voltage.
Further, the voltage applied to the electrode 72 is a voltage for efficiently extracting ions from the ion source 1, and the SUP (Sup
(pression) voltage.

Next, the operation will be described with reference to FIGS. Plasma is generated in the ion source 1 by the gas supplied from the high-voltage unit power supply / gas supply unit 4 and various power supplies, and dopant ions such as arsenic, phosphorus, and boron are generated. These dopant ions are generated by a high voltage applied from the extraction power source 5 to the ion source 1, that is, EXT (30 k
It is accelerated and pulled out by V) and is incident on the analysis magnet unit 6. At this point, the ion has an energy equivalent to 30 keV.

In the analysis magnet section 6, only the necessary ions are selected by changing the strength of the magnetic field according to the extraction voltage and changing the orbital radius of the ions, and thereafter, they are made incident on the acceleration tube 8. If necessary, the voltage of the acceleration power source 22 is further accelerated between the electrode 81 of the acceleration tube 8 and the point A at the ground potential (in the example of FIG. 7, the acceleration power source 2 is used).
2 will be cut off and slowed down here).

That is, the energy of the ions with which the target 101 is irradiated must be much lower than the extraction voltage, and must correspond to the energy of the implantation. Therefore, it is necessary to decelerate the acceleration tube 8 without accelerating it. That is, as shown in FIG. 7, the ions lose energy equivalent to 27 kV between the electrode 81 and the boundary A. The scan electrode unit 9, the end station 10, and the target 101 are at the ground potential, and the ions are neither accelerated nor decelerated after the acceleration tube 8.
After being adjusted to have the required energy (corresponding to 3 kV) in this way, a predetermined scan is performed in the scan electrode unit 9 and the target electrode 101 in the end station 10 is injected.

According to this deceleration method, since it is possible to extract ions at a high voltage EXT voltage (30 kV), more ions can be extracted and more ions than the variable method described above. Can be irradiated. However, in the deceleration method, since the ion beam is decelerated in the accelerating tube 8, the width of the ion beam is widened, ions that do not reach the boundary A are generated, and the beam current is reduced.
On the other hand, at the same time, some of the ions are neutralized, and an energy contamination phenomenon occurs in which the neutralized particles irradiate the target with the energy equivalent to the EXT voltage. When this phenomenon occurs, particles are driven into the deep part of the target and it becomes impossible to form a desired shallow electrode. Further, the ions decelerated by the deceleration voltage must pass through the scan electrode unit 8 and the inside of the end station 10.
Since this distance is relatively long, there is a problem that the beam spreads to some extent, as in the case of the variable system described above.

[0018]

The conventional ion implanter has the above-mentioned problems. That is, (1) In the variable system, only a small amount of ion beam is obtained and the beam spreads, so that the in-plane characteristics of the target cannot be made uniform. (2) In the deceleration method, although more ion beams can be obtained than in the variable method of (1), it is not sufficient, and the in-plane characteristics of the target cannot be made uniform due to the spread of the beam. Furthermore, the desired implantation distribution cannot be obtained due to energy contamination.

The present invention has been made to solve the above-mentioned problems, and suppresses the spread of the ion beam to improve the in-plane uniformity, and at the same time, does not lower the ion current and reduces the energy. It is an object to provide an ion implantation device that reduces contamination.

[0020]

An ion implantation apparatus according to a first aspect of the present invention is an ion source for producing ions, an extraction electrode section for applying an extraction voltage to the ion source to accelerate and extract the ions, and the extraction electrode section. Analysis magnet section for selecting only desired ions from the ions extracted from the deceleration electrode section for decelerating the ions selected by the analysis magnet section, higher than ground potential, and higher than the potential of the extraction electrode section. Is also set to a low potential and is provided with a target on which the ions decelerated by the deceleration electrode section are irradiated, and an end station which holds the target.

[0021]

In the invention according to claim 1, the ions are decelerated in the vicinity of the target by setting the target to a potential higher than the ground potential and lower than the potential of the extraction electrode portion.

[0022]

【Example】

Example 1. An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a configuration between a portion of an ion implantation apparatus to which an extraction voltage is applied and a portion of a target which is a target of ion implantation.

In the figure, 1 is an ion source for supplying toppanto ions such as arsenic, phosphorus, and boron, 2 is an insulator (bushing) for insulating the ion source 1 from the high-voltage pedestal 7,
Reference numeral 3 is an extraction electrode portion to which a high voltage is applied in order to efficiently extract ions from the ion source 1, 4 is a high voltage portion power supply / gas supply portion which uses gas or solid vapor as an ion source in a high density plasma state by discharge, and 5 Is an extraction power source that generates a high voltage for extracting ions in plasma, 6 is an analysis magnet unit that selects only desired impurity ions by setting the magnetic field strength by an electromagnet, and 7 is an ion source 1 to 1.
It is a high-voltage pedestal that houses the analysis magnet unit 6 and keeps them at a high potential. Reference numeral 8 is an accelerating tube for further accelerating the ions as necessary, and normally, it is not necessary to accelerate, and is therefore at the ground potential (GND). 9 is a scanning electrode unit for scanning the ion beam that has passed through the accelerating tube 8 by electrostatic deflection to uniformly irradiate the fixed target with the ion beam. 10 is the target with the ion beam from the scanning electrode unit 9. An end station that houses and holds a target (not shown) for irradiation, 11 is an external power source for giving a positive potential to the end station 10, 12 is an insulator for separating the end station 10 from the GND potential, 13 is a speed reducer for decelerating ions,
Reference numeral 14 is an end station, a pedestal for accommodating the insulator 12, 15 is an insulator for insulating the high-voltage pedestal 7, 16 is a ground wire for setting the pedestal 14 to the GND potential, and 17 is a scanning electrode section 9 for applying a scanning potential. It is an external power supply.

FIG. 2 is a view showing the outline of the electrode arrangement inside the ion implantation apparatus of the first embodiment, where 71 is the electrode of the ion source 1, 72 and 73 are the electrodes of the high voltage pedestal 7, and 81.
Is an electrode of the accelerating tube 8, and the electrodes 73 and 81 have the same potential as the high-voltage pedestal 7. Reference numeral 101 is a target held inside the end station 10, and 132 is an electrode of the speed reducer 13.

FIG. 3 is a diagram for explaining the internal potential of the ion implanter of the first embodiment. In the figure, as an example, the concrete potential is entered, and the ground potential (GN
With reference to D), the potential of the electrode 71 is 30 kV, the potential of the electrode 72 is -2 kV, the potential of the electrode 73 and the electrode 81, the boundary A between the acceleration tube 8 and the scan electrode section 9, and the scan electrode section 9 and the deceleration tube. The potential of the boundary C with 13 is the ground potential (GND), the electrode 1
The potential of 32 is 27 kV.

The voltage between the target 101 and the electrode 71 is the voltage finally given to the ions with which the target is irradiated, and is called the implantation voltage. The voltage applied to the electrode 71 is a voltage for extracting ions, and
(Extraction) voltage. Further, the voltage between the electrode 73 and the like and the electrode 72 is a voltage for efficiently extracting ions from the ion source 1, and is called a SUP (Suppression) voltage.

By the way, the voltage φ ₁ applied to the end station 10 from the external power source 11 is
It is assumed that the energy of the ions implanted into is equivalent to the above-mentioned implantation voltage. That is, the potential φ _{2 of the} ion source 1
Is given by the following formula. φ ₁ = φ ₂ − (implantation voltage) For example, when the potential φ ₂ of the ion source 1 is 30 kV and the energy required by the ions is 3 kV, φ ₁ = 30 KV−3 KV = 27 KV.

Next, the operation will be described with reference to FIGS. 1 to 3. Plasma is generated in the ion source 1 by the gas supplied from the high-voltage unit power supply / gas supply unit 4 and various power supplies, and dopant ions such as arsenic, phosphorus, and boron are generated. These dopant ions are generated by a high voltage applied from the extraction power source 5 to the ion source 1, that is, EXT (30 k
V) The voltage is accelerated / extracted by the voltage and is incident on the analysis magnet unit 6. At this point, the ion has an energy equivalent to 30 kV.

In the analyzing magnet unit 6, only the necessary ions are selected by changing the magnetic field strength according to the extraction voltage and changing the orbital radius of the ions, and the ions are incident on the accelerating tube 8. Normally, the ions are not accelerated in the accelerating tube 8 and the ions maintain the energy of 30 keV. That is, when the ions pass through the accelerating tube 8, they have energy equivalent to 30 keV due to the EXT voltage.

Next, the ions enter the scanning electrode portion 9 and are subjected to a predetermined scanning so as to uniformly irradiate the surface of the target based on the voltage from the external power source 17. Since the potential of the scan electrode portion 9 is the ground potential (GND), the ions are neither accelerated nor decelerated in the scan electrode portion 9, but the scan electrode portion is kept at a very high kinetic energy of 30 kV as compared with the conventional example. Pass 9

By the way, the energy of the ions irradiating the target 101 must be much lower than this, and must correspond to the implantation energy = 10 kV. Therefore, the deceleration pipe 13 decelerates. That is, the electrode 132 of the deceleration pipe 13 is supplied with the same electric potential as that of the end station 10, φ ₁ = 20 kV, from the external power supply 11. Therefore, in the deceleration tube 13, the ions are decelerated by the external power supply voltage (deceleration voltage) from the external power supply 11. Then, in this state, the ions enter the end station 10.

That is, in the deceleration tube 13, the ions are φ
_It loses ₁ kinetic energy and is decelerated, losing 27 kV kinetic energy. Therefore, the ions with which the target 101 is irradiated have energy corresponding to the implantation voltage.
(φ ₂ −φ ₁ = 3 keV).

With such a structure, the extraction voltage (EXT) can be increased, the number of ions is large, the beam current can be large, and the scanning electrode section 9 is passed in a high energy state. , The spread of the beam can be suppressed.

Further, since the deceleration tube 13 decelerates near the end station 10, a large amount of ion beam can be obtained. Therefore, as a result, the energy contamination phenomenon is reduced and is hardly affected. Therefore, the target can be stably doped and the yield is improved.

In the description of this embodiment, the target 101 is fixed and the scanning electrode section 9 deflects the ion beam to perform uniform doping. However, the present invention is not limited to this. Needless to say, the target 101 may be scanned instead.

[0036]

As described above, according to the present invention, the potential of the target is higher than the ground potential and the potential of the extraction electrode portion is higher than the potential of the target. As the number increases and the ions are decelerated near the target, the spread of the beam can be suppressed without lowering the beam current, and the in-plane characteristics of the target can be made uniform.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an ion implantation apparatus according to a first embodiment of the present invention.

FIG. 2 is a layout view of electrodes of the ion implantation apparatus according to the first embodiment of the present invention.

FIG. 3 is a diagram for explaining the operation principle of the ion implantation apparatus according to the first embodiment of the present invention.

FIG. 4 is a configuration diagram of a conventional variable-type ion implantation apparatus.

FIG. 5 is a configuration diagram of a conventional deceleration type ion implantation apparatus.

FIG. 6 is a layout view of electrodes of a conventional deceleration type ion implantation apparatus.

FIG. 7 is a diagram for explaining the operating principle of a conventional deceleration type ion implantation apparatus.

[Explanation of symbols]

 1 Ion source 2 Insulator (bushing) 3 Extraction electrode part 4 High voltage part power supply / gas supply part 5 Extraction power supply part 6 Analysis magnet part 7 High voltage mount 8 Accelerator tube 9 Scan electrode part 10 End station 11 External power supply 12 Insulator ( Insulator) 13 Speed reducer 14 Frame 15 Insulator (insulator) 16 Ground wire 17 External power supply

Claims (1)

[Claims] 1. An analysis for selecting only a desired ion from an ion source that generates ions, an extraction electrode section that applies an extraction voltage to the ion source to accelerate and extract the ions, and ions extracted from the extraction electrode section. A magnet unit, a deceleration electrode unit for decelerating the ions selected by the analysis magnet unit, and a potential higher than the ground potential and lower than the potential of the extraction electrode unit, and decelerated by the deceleration electrode unit. And an end station that holds the target.