JPH0251837A - Ion implantation method and device - Google Patents

Abstract

PURPOSE:To prevent secondary electrons from jumping out from a Faraday cup even if a discharge occurs to the Faraday cup and invariably correctly measure the beam current by providing multiple split bias rings and applying the negative voltage to them respectively. CONSTITUTION:An ion implanter has bias rings applied with the negative voltage to prevent secondary electrons from jumping out on the side implanted with an ion beam of a Faraday cup 38 taking in the secondary electrons generated when the ion beam is implanted into a semiconductor wafer 16, multiple split bias rings 32-34 in the advance direction of the ion beam and multiple power sources 35-37 applying the negative voltage to the bias rings respectively are provided. Even if a discharge occurs from the nearest bias ring 34 to the Faraday cup 38, the negative voltage is applied to the bias rings 33 and 34 respectively, secondary electrons are prevented from jumping out to the outside of the bias rings 33 and 34, the measured value of the beam current by an ammeter 23 is correct.

Description

[Detailed Description of the Invention] (Summary) Regarding an ion implantation method and apparatus for implanting ions into a 4'W non-wafer, the purpose is to constantly and accurately measure the beam current, and when an ion beam is implanted into the wafer. In an ion implantation method in which a bias ring to which a negative voltage is applied is provided on the side of a Faraday cup into which the ion beam is implanted to take in generated secondary electrons, and to prevent the secondary electrons from jumping out, the bias ring The ring is divided into a plurality of parts in the traveling direction of the ion beam, and a negative voltage is applied to each part.

[Industrial application field]

The present invention relates to an ion implantation method and apparatus, and
C. The present invention relates to an ion implantation method and apparatus for performing ion implantation.

As a method for doping semiconductor wafers with impurities,
There are thermal diffusion methods and ion implantation methods, and the ion implantation method is widely used because it has the advantage of accurately determining the amount of impurities and being able to perform doping at low temperatures.

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

In the figure, impurity ions generated by an ion source 10 are extracted by an extraction lens 11 and guided to an analyzer magnet 12, where they are subjected to mass analysis to select only desired impurity ions. An ion beam of selected impurity ions is accelerated by an accelerating tube 13, passes through a Faraday cup 14, and is implanted into a wafer 16 attached to a disk 15.

[Conventional technology]

FIG. 3 shows a structural diagram of a part of a conventional ion implanter.

In the figure, 20 is a cylindrical Faraday cup, and a bias ring 21 is provided in front of it (in the direction in which the ion beam enters).

When the positive ion beam hits the wafer 16, electrons are supplied in the opposite direction, that is, from the rotating shaft 22 of the disk 15, to neutralize it. this'! ? is read with an ammeter 23 as a beam current, and the amount of impurity implanted can be determined from this beam current.

The Faraday cup 20 captures the secondary electrons ejected by the wJv4 injected into the ion beam 16 and returns them from the disk 15 to the wafer 16 without passing through the ammeter 23, whereby the secondary electrons are read as beam current. This prevents it from happening.

In order to improve the throughput of ion implantation, as the beam current increases, more of the secondary electrons jump out of the Faraday cup 20. To prevent this, a bias ring 21 is provided and a large negative voltage is applied by the power supply 24. The secondary electrons are then returned to the Faraday cup 2o.

(Problems to be Solved by the Invention) As the beam current increases in order to improve throughput, the negative voltage applied to the bias ring 21 also increases.

Therefore, the voltage may concentrate on the sharp corner 21a of the bias ring 21, causing discharge in the Faraday cup 20. In such a case - the bias ring 21
As the electric field decreases, the secondary electrons move into Faraday cup 2
0 and the ammeter 23 jumps out of the bias ring 21.
There was a problem that the beam current measurement box became inaccurate.

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 K1ff1 that constantly and accurately measure beam current.

[Means to solve the problem]

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

Further, in the ion implantation apparatus of the present invention, secondary electrons are placed outside the Faraday cup (38) on the side where the ion beam is implanted, which takes in the secondary electrons generated when the ion beam is implanted into the semiconductor wafer (16). In an ion implanter that has a bias ring to which a constant voltage is applied to prevent the ion beam from jumping out, the ion beam is divided into multiple parts υ1 in the traveling direction.
bias rings (32-34), and a plurality of power supplies (35-37) that apply negative voltages to each of the bias rings (32-34).

[Function] In the present invention, a bias ring divided into a plurality of parts (
32 to 34) are provided and a negative voltage is applied to each,
This negative voltage is a high voltage and the bias ring (32-34)
Even if a discharge occurs in the Faraday cup (38) from one of the bias rings, a negative voltage is applied to the remaining bias rings, so secondary electrons are prevented from jumping out of the Faraday cup (38). The beam current measurement value is accurate.

〔Example〕

FIG. 1 shows a structural diagram of an embodiment of a part of the apparatus of the present invention.

In the figure, the same parts as in FIG. 3 are given the same reference numerals, and their explanations will be omitted.

In FIG. 1, 30 is a beam gate for testing, and 31 is a front Faraday for testing. During testing, the beam gate 30 is moved in the six directions of the arrows, and the switches SW1.
3W2 are each connected to the ammeter 23. In this state, an ion beam is implanted into the surface 30a of the beam gate 30,
The beam current is measured with an ammeter 23.

During actual ion implantation, the beam gate 30 is lowered and the ion beam is directed to the opening 30b of the beam gate 30 as shown in the figure.
Let the state pass through. Also, the beam goo 1-30 and the front Faraday 31 are grounded by switching the switches SW1, 8W2, respectively.

Behind the beam gate 30 (on the wafer 16 side), bias rings 32, 33, and 34 are arranged along the dome passing direction shown in the arrow 8 direction. bias ring 32.3
3.34 is a large negative voltage (
For example, ~1600V) is applied. Each of the bias rings 32, 33, and 34 has a substantially circular cross section and no corner, and is spaced apart from each other by a certain length.

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

In this way, the bias rings 32 to 34 and the Faraday cup 38 have rounded portions that face each other and do not have sharp corners, so there is no concentration of voltage and discharge from the bias rings 32 to 34 to the Faraday cup 38. There is a low risk of

Further, since a plurality of bias rings 32 to 34 are provided, even if discharge occurs from the nearest bias ring 34h1 to the Faraday cup 38, the bias ring 33.
A large negative voltage is applied to each of the bias rings 33 and 34, preventing secondary electrons from jumping out of the bias rings 33 and 34, and the beam current measured by the ammeter 23 is accurate.

In addition, in FIG. 1, the periphery 3 of the Faraday cup 38
8a is notched diagonally with respect to the Y axis, but this is determined by the direction of movement of the beam gate 30 (six arrow directions), and this may also be a notch cut in the Y@ force direction, as described above It is not limited to the examples.

According to this method, even if a discharge occurs to the Faraday cup, secondary electrons can be prevented from flying out from the Faraday cup, and the beam current g1 can be measured accurately at all times, which is extremely useful in practice.

[Brief explanation of the drawing]

FIG. 1 is a structural diagram of an embodiment of the device of the present invention, FIG. 2 is a conceptual diagram of an ion implantation device, and FIG. 3 is a structural diagram of an example of a conventional device. In the figure, 16 is a wafer, 23 is an ammeter, 32 to 34 are bias rings, 35 to 37 are power supplies, and 38 is a Faraday cup. 〔Effect of the invention〕

Claims (2)

[Claims] (1) A bias ring to which a negative voltage is applied is provided on 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 wafer (16). In an ion implantation method that prevents secondary electrons from jumping out, the bias ring is arranged in a plurality of directions in the traveling direction of the ion beam.
32 to 34), and applying a negative voltage to each ion implantation method. (2) To prevent the secondary electrons from jumping out 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 wafer (16). In an ion implantation apparatus having a bias ring to which a negative voltage of An ion implantation apparatus characterized by having a plurality of power supplies (35 to 37) that apply .