JP2001312974A - Ion extraction electrode system and ion implantation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ion extraction electrode system and an ion implantation device for ensuring prevention of contamination during implanting impurities in a semiconductor substrate, even if it is used for a long time, permitting precise implantation of the impurities in a desired amount, and facilitating maintenance. SOLUTION: The ion extraction electrode system 3 comprises an ion generating chamber, a drawing electrode located adjacent to the ion-generating chamber, and a ground electrode adjacent to the extraction electrode, at least the extraction electrode 3b and the ground electrode 3c formed of semiconductive materials. For example, when the impurities are implanted into a silicon substrate, at least the extraction electrode and the ground electrode are made of silicon.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an ion beam processing apparatus using an ion beam, and more particularly to an ion implantation apparatus for a semiconductor device and an ion extraction electrode system used in the ion implantation apparatus.

[0002]

2. Description of the Related Art In manufacturing a semiconductor device, an ion implantation method is known as a technique for doping a semiconductor substrate with impurities. The ion implantation method is a method in which a substance to be doped is implanted into a substrate as an ion beam.Compared with the thermal diffusion method in which impurities are diffused from the surface of the substrate, precise control of the impurity implantation amount and the accuracy of a circuit pattern are improved. Due to its advantages, the technology required for semiconductor devices has become a central technology as the characteristics thereof have become more advanced year by year.

FIG. 1 schematically shows an example of an ion implantation apparatus. As shown in FIG. 1, ions extracted from the ion source 2 by the ion extraction electrode system 3 are guided to the mass spectrometer 4 inside the apparatus in a vacuum state. Get. The analyzed ions enter the acceleration tube 6, are shaped into a sharp beam 20 by the focusing lens 7, and are scanned vertically and horizontally by the scanning electrode 8. Thus, the ion beam 20
When traveling through the apparatus 1, neutral particles are generated by colliding with the residual gas inside the apparatus, and the uniformity of ion implantation is deteriorated. It is bent several times, and further reaches the substrate 11 through the mask 9 and the Faraday cup 10.

There are various types of ion sources for generating an ion beam. In this type of apparatus, a method is generally used in which a substance to be implanted is made into a plasma state by arc discharge or the like, and ions are electrostatically extracted therefrom. Used.

The ion extraction electrode system for electrostatically extracting ions as described above generally comprises three electrodes as shown in FIG. The first electrode also serves as an ion generation chamber (arc chamber) 3a, and the second electrode is provided at a predetermined interval.
Electrode (lead electrode) 3b, third electrode (ground electrode) 3c
Are sequentially installed. For example, the extraction electrode 3b and the ground electrode 3c are usually provided with a through hole 14 at the center through which the extracted ions pass as shown in FIG. 3, or a plurality of holes as shown in FIG. Through holes 14 are provided at predetermined intervals.

When impurities are implanted into the substrate, a positive voltage is applied to the arc chamber 3a and a negative voltage is applied to the extraction electrode 3b, and the potential difference becomes the extraction voltage to accelerate ions. Further, the potential difference between the ground electrode 3c and the extraction electrode 3b becomes a deceleration voltage, and the ions are decelerated here. The reason why the ions are decelerated is to prevent electrons from flowing back to the arc chamber side from beam plasma or the like generated by the ion beam.

The ions thus extracted are implanted into the substrate under predetermined conditions. By precisely controlling the ions to be implanted, a semiconductor element having desired characteristics can be manufactured.

[0008]

In many ion beam processing apparatuses such as the ion implantation apparatus, the arc chamber is generally made of stainless steel (SUS) or molybdenum, and the extraction electrode and the ground electrode are often made of graphite. However, when ions converted into plasma in the ion generation chamber are extracted to form an ion beam, each electrode constituting the ion extraction electrode system is damaged by the beam, and thereby, unnecessary metal ions such as Fe and Cr, There is a problem that graphite is generated and mixed into the substrate 11 to cause metal contamination (contamination).

Conventionally, when each electrode is damaged or contaminated by an ion beam as described above, maintenance such as cleaning or replacement of parts is required, and operation of the apparatus is required. This was a factor that reduced the rate.

To solve such a problem, Japanese Patent Application Laid-Open No. 9-259
No. 779 discloses that the inner wall of a plasma chamber (ion generation chamber) is covered with a coating material made of silicon or carbon,
An electrode system in which at least the plasma side surface of the extraction electrode (second electrode) is made of silicon or carbon is disclosed.

In the electrode system disclosed in JP-A-9-259779, since a part of the first electrode is made of silicon or carbon, heavy metal ions are hardly generated. Even if the silicon film is coated, if used for a long time, the silicon film may be peeled off, and the graphite may be damaged, and the fine particles may adhere to other parts of the apparatus or the substrate, thereby causing contamination. In addition, the ion extraction electrode system is easily damaged by the ion beam and damages not only the extraction electrode but also the ground electrode. Therefore, as the number of times of use increases, the contamination of the substrate increases, and desired characteristics can be obtained. There is also a problem that it cannot be done.

When carbon caused by graphite is injected into a silicon substrate together with a target impurity,
Although there are few problems compared to heavy metal implantation, prevention of contamination or precise control of impurity implantation amount may not be sufficient for recent ion implantation processes that require particularly precise control. With
This will also adversely affect device characteristics. further,
There is also a problem that no consideration is given to the case of performing ion implantation on another semiconductor substrate made of germanium, GaP, or the like.

Therefore, according to the present invention, when implanting impurities into a semiconductor substrate, contamination can be reliably prevented even when used for a long period of time, and impurities can be implanted precisely in a desired amount. An object is to provide an extraction electrode system and an ion implantation apparatus.

[0014]

According to the present invention, there is provided, in accordance with the present invention, an ion generating chamber, an extraction electrode adjacent to the ion generation chamber, and a ground electrode adjacent to the extraction electrode. In an ion extraction electrode system, at least the material of the extraction electrode and the ground electrode,
There is provided an ion extraction electrode system comprising a semiconductor material (claim 1). Specifically, as the semiconductor material, silicon, germanium, GaP, In
It can be P or GaAs (claim 2).

When ions are extracted by an ion extraction electrode system and a desired amount of impurities are implanted into a semiconductor substrate made of silicon or GaP, at least the extraction electrode and the ground electrode are made of an ion extraction electrode system made of the same material as the semiconductor substrate to be processed. If these electrodes are used, even if these electrodes are damaged, ions of the same type as the semiconductor substrate will be generated, so that contamination can be reliably prevented even when used for a long time, and the desired amount of impurities can be precisely controlled. Can be driven.

In this case, it is preferable that the semiconductor material is doped with impurities (claim 3). Specifically, the semiconductor material may be O, P,
As, Sb, B or Al is mentioned (claim 4).

With the extraction electrode and the ground electrode made of the semiconductor material doped with the impurities as described above,
Even if these electrodes are damaged, only ions of the same type as the impurities implanted into the substrate are generated together with ions of the same type as the material of the substrate, so contamination at a fine level can be prevented. While you can
The desired amount of impurities can be implanted with very strict control.

For example, when boron (B) is implanted into a silicon substrate, an extraction electrode and a ground electrode made of silicon doped with boron, that is, an electrode made of the same material as the substrate to be processed are selected and ion implantation is performed. For example, even if a part of the ion beam from the ion source damages these electrodes, the ions generated therefrom become silicon and a trace amount of boron. Therefore, there is no contamination, and the amount of boron implanted can be strictly adjusted.

When silicon is used as the material of the electrode, the electrode may have an oxygen concentration in the range of 5 to 30 ppma. Silicon having an oxygen concentration within the above range particularly has a gettering effect of heavy metals, so even if heavy metal ions are generated from the ion generation chamber or the like, they are trapped in the extraction electrode or the ground electrode to prevent contamination. It can be more effectively reduced.

When silicon is used as the material of the electrode, the specific resistance of the silicon is 0.001 to 50.
It is preferably in the range of Ω · cm (claim 6). Many of the silicon substrates to be subjected to the ion implantation treatment are preferable because they have a specific resistance in the above range, so that they are easily available and have the same properties as many silicon substrates to be subjected to the ion implantation treatment.

Further, according to the present invention, there is also provided an ion implantation apparatus provided with the ion extraction electrode system. An ion implantation apparatus for generating an ion beam and implanting impurities into a semiconductor substrate by an ion extraction electrode system including an ion generation chamber, an extraction electrode adjacent to the ion generation chamber, and a ground electrode adjacent to the extraction electrode. An ion implantation apparatus is also provided, wherein at least the extraction electrode and the ground electrode are made of the same material as the semiconductor substrate (claim 8).

If the extraction electrode and the ground electrode constituting the ion extraction electrode system of the ion implantation apparatus are made of the same material as the substrate to be ion-implanted, these electrodes are damaged by the ion beam. However, since only ions of the same type as the material of the substrate are generated, contamination to the substrate to be processed can be reliably prevented, and the amount of implanted impurities can be accurately controlled.

[0023]

Embodiments of the present invention will be specifically described below with reference to the drawings, but the present invention is not limited to these embodiments.

The ion extraction electrode system according to the present invention comprises an ion generation chamber, an extraction electrode adjacent to the ion generation chamber, and a ground electrode adjacent to the extraction electrode, and at least the extraction electrode and the ground electrode. Is characterized by comprising a semiconductor material. Specific semiconductor materials include the most common silicon, elemental semiconductors such as germanium, and Ga.
Compound semiconductors such as P, InP or GaAs can be used, but are not limited thereto.

The ion extraction electrode system according to the present invention as described above can be suitably used when impurities are implanted into a substrate made of the same kind of material as the semiconductor material constituting the electrode. For example, when boron is implanted into a silicon substrate, an ion extraction electrode system including an extraction electrode made of silicon and a ground electrode can be used. In this case, even if the extraction electrode and the ground electrode are damaged by the ion beam extracted from the ion generation chamber, substances other than silicon do not enter the ion beam, so that contamination can be reliably prevented for a long period of time. Can be. Further, in the present invention, since both the extraction electrode and the ground electrode are made of a semiconductor material, there is no problem such as peeling as in the case of covering with a silicon film.

Further, the semiconductor material may be doped with an impurity, if necessary. The impurities to be doped include, but are not limited to, O, P, As, Sb, B or Al.

When an extraction electrode and a ground electrode made of a semiconductor material doped with an impurity as described above are used in an ion implantation apparatus, for example, when boron is implanted into a silicon substrate, the same material as the semiconductor substrate to be ion-implanted is used. By using a lead electrode and a ground electrode obtained by doping boron into silicon, contamination can be effectively prevented and a desired amount of impurities can be accurately implanted into the silicon substrate.

When a silicon electrode is used, the oxygen concentration in silicon is preferably 5 to 30 ppma. If oxygen is doped in silicon, for example, heavy metal ions such as Fe and Cr are generated from an ion generation chamber or the like, or even if heavy metals are generated from other contamination sources,
It is gettered by oxygen in the electrode, and has the effect of further reducing contamination. When the oxygen concentration is 5
If it is less than ppma, a sufficient gettering effect cannot be obtained, and if it exceeds 30 ppma, oxygen precipitation defects are excessively generated, and particles resulting therefrom may increase. Therefore, the oxygen concentration is within the above range. Is preferred.

Further, when silicon is used as the material of the electrode according to the present invention, its specific resistance is 0.001 to 50.
Ω · cm, preferably 0.001
It is preferably from 10 to 10 Ω · cm. Many of the silicon substrates subjected to the ion implantation treatment have a specific resistance in the above range, and in particular, a silicon substrate in a range of 0.001 to 10 Ω · cm can be easily obtained, which is advantageous in cost. In addition, if the electrode is made of not only the same material as most of the silicon substrate to be subjected to the ion implantation process but also has the same electrical properties, contamination can be prevented more effectively, and the electrical conductivity of the silicon substrate can be reduced. Effects can be minimized.

With respect to the method of manufacturing the extraction electrode and the ground electrode according to the present invention, a single crystal is manufactured by a general semiconductor single crystal manufacturing method such as the Czochralski method (CZ method) or the floating zone method (FZ method). Then, this is cut into a desired shape, and further, for example, as shown in FIG. 3 or FIG. 4, by providing a through hole 14 at a predetermined position as shown in FIG.

In the case of manufacturing electrodes from semiconductor materials doped with impurities, a usual method of doping impurities at the time of growing a semiconductor single crystal constituting these electrodes can be applied. That is, the Czochralski method (CZ)
When a single crystal is pulled by a method, etc., a desired amount of impurities are added to the melt to produce a single crystal rod, which can be cut into a desired shape to form an electrode. As another manufacturing method, an impurity can be doped after growing a semiconductor single crystal. Note that the semiconductor material forming the electrode according to the present invention is not limited to a single crystal, and a polycrystal may be used.

Here, when oxygen is selected as an impurity to be doped into the electrode, it is preferable to produce a single crystal by the CZ method. Since the quartz crucible is usually used in the CZ method, oxygen can be easily doped into the semiconductor single crystal to be manufactured, and the oxygen concentration accurately doped by controlling the number of rotations of the quartz crucible during the manufacturing can be improved. Is adjusted.

Further, in the present invention, an ion beam is generated by an ion extraction electrode system including an ion generation chamber, an extraction electrode adjacent to the ion generation chamber, and a ground electrode adjacent to the extraction electrode, and the ion beam is generated on the semiconductor substrate. An ion implantation apparatus for implanting impurities, wherein at least the extraction electrode and the ground electrode are made of the same material as the semiconductor substrate.

If the impurity is implanted by using the extraction electrode and the ground electrode made of the same material as the semiconductor substrate into which the impurity is implanted, not only the extraction electrode but also the ground electrode conventionally made of graphite is ionized. Even if sputtered by a beam, only particles of the same material as the substrate are generated, and contamination can be reliably prevented. Further, even if the electrode surface is damaged due to long-term use, the electrode itself is made of the same material as the substrate, so that contamination hardly occurs and the ion implantation process can be precisely controlled. Further, since no heavy metal or the like adheres to the electrode, cleaning is hardly required, and maintenance is easy. As a result, the yield is improved and the maintenance time can be shortened, so that the operation rate is improved and the cost of replacing parts can be reduced.

As described above, in the ion implantation apparatus according to the present invention, at least the extraction electrode and the ground electrode of the ion extraction electrode system are made of the same semiconductor material as the substrate on which the impurity is implanted, and preferably, the semiconductor material doped with the impurity. Therefore, contamination can be prevented at a fine level, and a desired amount of impurities can be accurately implanted into a substrate over a long period of time, and impurities can be implanted into a large number of semiconductor substrates with a uniform implantation amount. it can. In addition to the extraction electrode and the ground electrode, the ion generation chamber is made of the same material as the substrate, and if the entire ion extraction electrode system is made of the same material as the substrate, the effect of preventing contamination etc. is further improved. Can be done.

[0036]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples. (Examples and Comparative Examples) A lead electrode 3b and a ground electrode 3c are P-type doped with boron and have a specific resistance of 5Ω · cm.
An ion implantation apparatus having an ion extraction electrode system composed of three electrodes as shown in FIG. 2 including a silicon extraction electrode and a ground electrode, and a conventional graphite electrode. Ion implantation into the substrate using an ion implantation apparatus equipped with both electrodes of, respectively,
The uniformity of the impurity implantation amount was compared.

More specifically, for each variation (%) of the impurity injection amount with respect to the target value, one sample was inspected for every 100 samples processed. The amount of impurity implantation was converted by measuring the resistance of the substrate. The implanted impurity was boron, and a silicon substrate having a diameter of 5 inches was used as a substrate to be processed. The result is shown in FIG.

According to FIG. 5, when a conventional lead electrode and ground electrode made of graphite are used, the amount of impurity implanted into the substrate has a large variation with respect to a target value. The variation became large and was about 14% when 3000 sheets were processed. This is presumably because the graphite electrode was gradually damaged and the graphite was mixed into the silicon substrate.

On the other hand, when the extraction electrode and the ground electrode according to the present invention made of boron-doped silicon are used, the impurity implantation amount is almost constant at a value close to the target value, and varies even after 3,000 sheets are processed. Did not fluctuate significantly. Therefore, it can be seen that even if the number of processed wafers increases, uniform impurity implantation is possible.

The present invention is not limited to the above embodiment. The above embodiment is merely an example, and has substantially the same configuration as the technical idea described in the claims of the present invention, and has the same function and effect,
Anything is included in the technical scope of the present invention.

For example, in the above, the present invention has been described mainly for the case of ion implantation into a silicon substrate. However, the present invention is not limited to this, and at least according to the semiconductor substrate to be ion-implanted, and preferably to the impurities to be implanted into the substrate. By selecting the materials of the extraction electrode and the ground electrode, it is possible to prevent contamination and strictly control the impurity injection amount.

[0042]

According to the present invention, there is provided an ion extraction electrode system provided with an extraction electrode made of a semiconductor material such as silicon and a ground electrode. By performing the ion implantation described above, even if these electrodes are damaged, only the same semiconductor material as that of the substrate is mixed, so that it is possible to prevent contamination and strictly control the amount of impurity implantation. As a result, the yield is improved, and the maintenance time can be shortened, so that the operation rate is improved, the productivity is improved, and the cost of component replacement can be reduced.

[Brief description of the drawings]

FIG. 1 is a schematic view of an example of a general ion implantation apparatus.

FIG. 2 is a partially enlarged cross-sectional view of an ion extraction electrode system.

FIG. 3 is a schematic front view of an example of an extraction electrode (second electrode).

FIG. 4 is a schematic front view of another example of the extraction electrode (second electrode).

FIG. 5 is a graph showing a variation in an impurity implantation amount in a silicon substrate.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Ion implantation apparatus, 2 ... Ion source, 3 ... Ion extraction electrode system, 3a ... Ion generation chamber (arc chamber, 1st electrode) 3b ... Extraction electrode (2nd electrode)
3c: ground electrode (third electrode) 4: mass spectrometer
5: analysis slit, 6: acceleration tube, 7: focusing lens,
Reference numeral 8 denotes a scanning electrode, 9 denotes a mask, 10 denotes a Faraday cup, 11 denotes a substrate, 14 denotes a through hole, and 20 denotes an ion beam.

Continued on the front page (72) Inventor Kazuyoshi Tamura 2-13-1, Isobe, Annaka-shi, Gunma F-term (reference) 4G029 AA06 BD01 CA10 DE04 5C030 DD10 DE04 DG09 5C034 CC01

Claims (8)

[Claims] 1. An ion extraction electrode system comprising an ion generation chamber, an extraction electrode adjacent to the ion generation chamber, and a ground electrode adjacent to the extraction electrode, wherein at least a material of the extraction electrode and the ground electrode Wherein the electrode is made of a semiconductor material. 2. The ion extraction electrode system according to claim 1, wherein the semiconductor material is silicon, germanium, GaP, InP or GaAs. 3. The ion extraction electrode system according to claim 1, wherein the semiconductor material is doped with an impurity. 4. The method according to claim 1, wherein the doped impurities are:
The ion extraction electrode system according to claim 3, wherein the ion extraction electrode system is O, P, As, Sb, B or Al. 5. The semiconductor device according to claim 1, wherein the semiconductor material is silicon, and the oxygen concentration of the silicon is in a range of 5 to 30 ppma.
Item 14. An ion extraction electrode system according to Item. 6. The semiconductor device according to claim 1, wherein the semiconductor material is silicon, and a specific resistance of the silicon is in a range of 0.001 to 50 Ω · cm. An ion extraction electrode system as described. 7. An ion implantation apparatus comprising the ion extraction electrode system according to any one of claims 1 to 6. 8. An ion beam is generated by an ion extraction electrode system including an ion generation chamber, an extraction electrode adjacent to the ion generation chamber, and a ground electrode adjacent to the extraction electrode, and the semiconductor substrate is implanted with impurities. An ion implantation apparatus, wherein at least the extraction electrode and the ground electrode are made of the same material as the semiconductor substrate.