JP2706478B2 - Ion implantation method and apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Summary] The present invention relates to an ion implantation method and apparatus for implanting ions into a semiconductor wafer, with the object of always accurately measuring the beam current, and the secondary generated when an ion beam is implanted into the wafer. A negative ring is applied to a side of the Faraday cup into which the ions are implanted, and a bias ring to which a negative voltage is applied is provided. In the ion implantation method for preventing the secondary electrons from jumping out, the bias ring is connected to the ions. The beam is divided into a plurality in the traveling direction, and a negative voltage is applied to each.

[Industrial applications]

The present invention relates to an ion implantation method and apparatus, and more particularly, to an ion implantation method and apparatus for performing ion implantation on a semiconductor wafer.

As a method for doping impurities in a semiconductor wafer, there are a thermal diffusion method and an ion implantation method, and the ion implantation method is widely used because it has features such as accurate determination of an impurity amount and low-temperature doping.

 FIG. 2 shows a conceptual diagram of the ion implantation apparatus.

In the figure, impurity ions generated by an ion source 10 are extracted by an extraction lens 11 and are analyzed by an analyzer magnet 12.
, And mass analysis is performed to select only desired impurity ions. The ion beam of the selected impurity ions is accelerated by the acceleration tube 13 and is passed through the Faraday cup 14 and is injected into the wafer 16 mounted on the disk 15.

[Conventional technology]

FIG. 3 shows a partial structural view of a conventional ion implantation apparatus.

In the figure, reference numeral 20 denotes a cylindrical Faraday cup, and a bias ring 21 is provided in front of the Faraday cup (incoming direction of the ion beam).

When the positive ion beam strikes the wafer 16, electrons are supplied in the opposite direction, that is, from the rotating shaft 22 of the disk 15, to neutralize the wafer. The electrons are read by the ammeter 23 to be used as a beam current, and the amount of impurities injected by the beam current can be known.

The Faraday cup 20 takes in secondary electrons that have jumped out from the impact of the ion beam injected into the wafer 16 and
The disk is returned from the disk 15 to the wafer 16 without passing through, thereby preventing secondary electrons from being read as a beam current.

As the beam current increases in order to improve the ion implantation throughput, the number of secondary electrons that jump out of the Faraday cup 20 increases. To prevent this, a bias ring 21 is provided, and a large negative voltage is applied by a power supply 24. Then, the secondary electrons are returned into the Faraday cup 20.

[Problems to be solved by the invention]

As the beam current increases to improve the throughput, the negative voltage applied to the bias ring 21 also increases.

For this reason, the voltage may concentrate on the sharp corner 21 a of the bias ring 21 and cause a discharge in the Faraday cup 20. In such a case, since the electric field of the bias ring 21 temporarily decreases, the secondary electrons jump out of the Faraday cup 20 and the bias ring 21 and pass through the ammeter 23, and the measured value of the beam current becomes inaccurate. There was a problem.

The present invention has been made in view of the above points, and an object of the present invention is to provide an ion implantation method and apparatus for constantly and accurately measuring a beam current.

[Means for solving the problem]

According to the ion implantation method of the present invention, a bias in which a negative voltage is applied to a side of the Faraday cup (38) into which an ion beam is implanted, which captures secondary electrons generated when the ion beam is implanted into the semiconductor wafer (16), is applied. In an ion implantation method in which a ring is provided to prevent secondary electrons from jumping out, an isling is divided into a plurality in the traveling direction of an ion beam, and a negative voltage is applied to each.

Further, in the ion implantation apparatus of the present invention, the secondary electrons are emitted to the side of the Faraday cup (38) into which the ion beam is implanted, which captures the secondary electrons generated when the ion beam is implanted into the semiconductor wafer (16). An ion implantation apparatus having a bias ring to which a negative voltage is applied to prevent the ion beam from jumping out, comprising: a bias ring (32 to 34) divided into a plurality in the traveling direction of the ion beam; and a bias ring (32 to 34). It has a plurality of power supplies (35 to 37) each of which applies a negative voltage.

[Action]

In the present invention, a plurality of divided bias rings (32 to 34) are provided, and a negative voltage is applied to each of the divided bias rings. This negative voltage is a high voltage and any one of the bias rings (32 to 34) is used. Even if a discharge occurs in the Faraday cup (38), the secondary voltage is prevented from jumping out of the Faraday cup (38) because a negative voltage is applied to the remaining bias ring, and the beam current is measured. The value is accurate.

〔Example〕

FIG. 1 shows a structural view of one embodiment of a part of the apparatus of the present invention. 3, the same parts as those in FIG. 3 are denoted by the same reference numerals, and the description thereof will be omitted.

In FIG. 1, reference numeral 30 denotes a test beam gate, and reference numeral 31 denotes a test front Faraday. During the test, the beam gate 30 is moved in the direction of arrow A, and the switches SW1 and SW2 are connected to the ammeter 23. In this state, an ion beam is injected into the surface 30a of the beam gate 30, and the beam current is measured by the ammeter 23.

At the time of actual ion implantation, the beam gate 30 is lowered so that the ion beam passes through the opening 30b of the beam gate 30 as shown. The switches SW1 and SW2 are switched to ground the beam gate 30 and the front Faraday 31.

Behind the beam gate 30 (on the side of the wafer 16), bias rings 32, 33, and 34 are arranged along a beam passing direction indicated by an arrow B direction. Bias rings 32, 33, 34 are power supply 35, 3
A large negative voltage (for example, -1600 V) is applied from each of 6,37. Each of the bias rings 32, 33, and 34 has a structure in which the cross section is substantially circular and has no corners, and is arranged to be apart from each other by a certain length.

The cylindrical Faraday cup 38 has a peripheral edge on the bias ring side.
38a is rounded and has no corners.

As described above, the bias rings 32 to 34 and the Faraday cup 38 have rounded portions facing each other and do not have sharp corners, so that there is no voltage concentration, and the bias ring 32
To 34 to the Faraday cup 38.

Also, since a plurality of bias rings 32 to 34 are provided, even if a discharge occurs from the closest bias ring 34 to the Faraday cup 38, a large negative voltage is applied to each of the bias rings 33 and 34, Secondary electrons are prevented from jumping out of the bias ring 33.34, and the ammeter 2
The measurement of the beam current by 3 is accurate.

In FIG. 1, the periphery 38 of the Faraday cup 38
Although a is notched obliquely with respect to the Y axis, it is determined according to the moving direction (arrow A direction) of the beam gate 30, and may be notched in the Y axis direction. It is not limited to the embodiment.

〔The invention's effect〕

As described above, according to the ion implantation method and apparatus of the present invention, even if a discharge to the Faraday cup occurs, secondary electrons can be prevented from jumping out of the Faraday cup, the beam current can always be measured accurately, and Above is very useful.

[Brief description of the drawings]

FIG. 1 is a structural view of an embodiment of the apparatus of the present invention, FIG. 2 is a conceptual view of an ion implantation apparatus, and FIG. 3 is a structural view of an example of a conventional apparatus. In the figure, 16 is a wafer, 23 is an ammeter, 32-34 are bias rings, 35
37 indicates a power source, and 38 indicates a Faraday cup.

Claims (2)

(57) [Claims] A Faraday cup (38) for capturing secondary electrons generated when an ion beam is implanted into a wafer (16).
Providing a bias ring to which a negative voltage is applied on the side where the ion beam is implanted, and preventing the secondary electrons from jumping out. An ion implantation method characterized by dividing into a plurality (32 to 34) and applying a voltage to each of them. 2. A Faraday cup (3) for capturing secondary electrons generated when an ion beam is implanted into a wafer (16).
8) In the ion implantation apparatus having a bias ring to which a negative voltage is applied to prevent the secondary electrons from jumping out to the side where the ion beam is implanted, An ion implantation apparatus comprising: divided bias rings (32 to 34); and a plurality of power supplies (35 to 37) for applying a negative voltage to each of the bias rings (32 to 34).