JPH05314945A - Negative ion implantation method - Google Patents

Abstract

(57) [Summary] [Purpose] To reduce the occurrence of charge-up phenomenon. [Structure] In a vacuum chamber 12 of a plasma sputtering negative ion source 11, a sputtering target 15 made of a material containing a target element (B, As, etc.) is arranged. Negative dimer ions such as two atoms such as B ₂ ⁻ and As ₂ ^{− which} are combined into one negative ion are generated from the ion source, and the dimer ions are separated and extracted by the mass analysis electromagnet 2.
Pour into the wafer 5. When secondary electrons are emitted from the wafer, the charge amount of the wafer becomes a difference in charge amount between the injected negative ions and the secondary electrons, which is smaller than that during the positive ion injection. The amount of charge per atom of dimer ions is half that of monatomic ions, charge-up is reduced, and beam transportation and low-energy injection are facilitated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a negative ion implantation method for implanting ions with a negative ion dimer beam.

[0002]

2. Description of the Related Art Currently, a high current type ion implanter used in a semiconductor device manufacturing process is 10 to 80 keV.
Ions are implanted into the semiconductor wafer with a beam current of about 1 to 10 mA in the energy range. FIG. 2 is a schematic configuration diagram of such an injection device. Ions extracted from the ion source 1 are passed through the magnetic field of the mass analysis electromagnet 2 to separate and extract ions of a desired mass. The extracted ion beam is introduced into the end station 3 in a vacuum state and injected into the wafer 6 held by the wafer disk 4.

In the ion implantation apparatus, a positive ion source is used as an ion source including the above-mentioned large current type machine to implant desired positive ions into the wafer. For example, in the large current type machine, Freeman type ion is used. The source is often used.

[0004]

By the way, when the beam current is in the mA class as in the case of a large current type machine, a charge is accumulated in the wafer due to ion implantation, and when it is discharged in an irregular state, the wafer on the wafer is discharged. The phenomenon that the element is destroyed and the charge-up phenomenon occur, which is the biggest problem.

It is an object of the present invention to provide an ion implantation method in which the charge-up phenomenon in a high current type ion implantation apparatus is less likely to occur.

[0006]

In order to achieve the above object, the present invention aims to implant the same type of diatomic ion from a negative ion source into an implant object in an ion implanter equipped with a mass analysis electromagnet. It is a feature.

[0007]

When the ions are injected into the body to be injected, secondary electrons are emitted. The charge amount of the injected body due to the injection of the negative ions is the difference between the charge amount of the injected negative ions and the charge amount of the emitted secondary electrons, so that the charge-up effect is reduced. Also, by using a diatomic ion in which two atoms of the same kind are combined as an ion as a negative ion, the amount of charge converted per atom is half that in the case of a monoatomic ion. In the case of the amount, the amount of charge by the implanted ions is halved.

[0008]

1 is a block diagram showing an embodiment of the ion implantation apparatus according to the present invention, in which the same reference numerals as those in FIG. 2 designate the same parts. A negative ion source 11 is used as the ion source, and the one shown in the figure is a plasma sputter type negative ion source that uses cesium to increase the negative ion generation efficiency. A gas inlet 13 is provided in the vacuum chamber 12 of the ion source.
Xenon gas is introduced from the filament 14 to collide with the thermoelectrons emitted from the filament 14 to generate xenon plasma,
It is confined in the vacuum chamber by the magnetic field of permanent magnets arranged around the vacuum chamber. Vacuum chamber 12
A sputtering target 15 made of a material containing a target element to be generated, for example, boron B and arsenic As, is supported and arranged by a backing plate 16 and a cooling shaft 17, and the target 15 is sputtered by a sputtering power source 18 in a vacuum chamber. By biasing 12 to a negative potential, the xenon plasma sputters the target 15. At this time, if cesium is attached to the surface of the target 15, the probability of negative ions being generated due to the sputtering increases. Therefore, cesium vapor is supplied from the cesium reservoir 19 into the vacuum chamber 12 and adhered to the target 15. The extraction electrode 20 is arranged at the ion outlet of the vacuum chamber 12, and the extraction power source 2
The negative ion generated in the vacuum chamber is extracted as a beam by setting the vacuum chamber 12 to a negative high potential (up to several tens of kV) with respect to the same electrode by 1.

In the plasma sputtering type negative ion source 11,
Negative dimer ions in which two atoms such as boron B such as B ₂ ⁻ and As ₂ ⁻ and arsenic As are combined to form one negative ion are often generated. The mass analysis electromagnet 2 separates and extracts the negative dimer ions from the extracted negative ion beam, and injects this dimer ion beam into the wafer 5.

By implanting negative ions, the charge-up phenomenon is reduced. When the ion hits the injected body, secondary electrons and atoms or molecules of the injected body are emitted in the form of neutral or ions from the injected body. The largest. If ions are injected and negatively charged secondary electrons are emitted from the wafer 5 to be injected, when the ions are positive ions, the charge amount of the wafer 5 is the charge amount of the injected positive ions and the emitted secondary electrons. Is the sum of the electric charges. On the other hand, as shown in the above-mentioned embodiment, when the ions are negative ions, the charge amount of the wafer 5 is the difference between the charge amounts of the injected ions and the emitted electrons, so that the charge amounts of the ions and the electrons are the same. Therefore, charge-up will not occur, and even if they do not match, the amount of charge on the wafer 5 is reduced by implanting negative ions, and the occurrence of charge-up phenomenon is reduced.

By using a dimer ion in which two atoms are combined to form an ion as the negative ion, the effect of reducing charge-up is further exhibited. For dimer ions, the amount of charge per atom is half that of conventional ions, and if the amount of atoms injected into the wafer 5 is the same as before, the beam current will be half, and the beam current will be twice as high as before. At the same time, a similar charge-up phenomenon will occur.

The dimer ions are effective in suppressing space charge and injecting low energy. When attempting to transport a high-current beam with low energy, the charges in the beam repel each other and the beam spreads, making it difficult to handle the beam, but it is easy to handle because the charge amount is half.

Implantation energy tends to decrease more and more, as seen in shallow junctions and surface amorphization. When the energy is lowered, the amount of the beam extracted from the ion source is reduced, and the space charge phenomenon appears more conspicuously, which makes it difficult for the implanter to sufficiently exhibit its operation and function. However, according to the dimer ion, when implanted with twice the energy, the target energy per single atom is obtained, which is effective for low energy implantation.

[0014]

As described above, according to the present invention, since negative ions are implanted, the charge amount of the injected object due to the ion implantation is the difference between the charge amount of the injected negative ions and the charge amount of the emitted secondary electrons. , The charge-up phenomenon is reduced. And
By using dimer ions and dimer ions in which two atoms of the same kind are combined as the negative ions, the charge amount converted per atom is half that in the case of monatomic ions, so the charge It is possible to reduce the occurrence of the up phenomenon.

Further, according to the negative dimer ion, the charge amount per atom is half that in the case of the monoatomic ion, and the charge amount of the transport beam can be reduced, so that the influence of space charge is reduced and the beam is easy to handle. Become. Further, the implantation energy per single atom is half of the implantation energy of ions, and since the implantation energy of ions can be increased, the amount of the extraction beam from the ion source is not reduced and the space charge is reduced. In the state where the influence of the above is reduced, low energy implantation for shallow junction, amorphization of the surface layer, etc. can be performed.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention.

FIG. 2 is a configuration diagram of a conventional example.

[Explanation of symbols]

 2 Mass spec electromagnet 4 Wafer disk 5 Wafer 11 Plasma sputter type negative ion source 12 Vacuum chamber 13 Xenon gas inlet 14 Filament 15 Sputter target 19 Cesium reservoir

Claims (1)

[Claims] 1. A method for implanting negative ions, which comprises implanting the same type of diatomic negative ions from a negative ion source into an implant object in an ion implanter equipped with a mass analysis electromagnet.