JPH02201856A - Impurity injection device - Google Patents

Abstract

PURPOSE:To prevent wafer charge-up during impurity injection by installing, between an acceleration tube and an end station, a neutralizer that neutralizes ions and a separator that separates charged particles. CONSTITUTION:A neutralizer 7 is installed behind a scanner 4. The neutralizer 7 converts ions into neutral particles which are potentially neutral by discharging electrons in case of positive ions or by acquiring electrons in case of negative ions. Particles leaving the neutralizer 7 are then passed through a magnetic field of a separator, e.g. separating magnet 8, where those charged particles that have not been neutralized by the neutralizer 7 are separated. Separated charged particles are absorbed by a damper 9. Almost all the particles that have passed through the separator 8 become neutral particles. Therefore, injecting these particles into a wafer 5 does not result in a charge-up of the wafer 5.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to an impurity implantation device.

(Prior Art) As is well known, impurities are implanted in order to form diffusion regions in semiconductor wafers. Conventionally, ions from an ion source are accelerated by an acceleration tube, and then
It is common practice to implant it into a wafer.

(Problem to be Solved by the Invention) According to such an impurity implantation device, there is not much problem when the ion beam current is a small current of about several tens of μA, but when it becomes a large current of about several tens of mA,
Charge-up caused by the ion beam being implanted into the wafer may cause dielectric breakdown.

An object of the present invention is to avoid the occurrence of a wafer charge-up phenomenon when implanting impurities into a wafer.

(Means for Solving the Problems) This invention is characterized in that a neutralizer for neutralizing ions and a separator for separating charged particles are installed between the acceleration tube and the end station. shall be.

(Operation) The ion beam accelerated by the accelerator tube is neutralized by the neutralizer and is no longer in a charged state. Subsequently, charged particles that have not been neutralized are separated and removed by a separation magnet. Only the beams that are no longer charged will reach the end station. Here, it is injected into the wafer, but this injection also prevents the wafer charge-up phenomenon from occurring.

(Example) An example of the present invention will be described with reference to the drawings. 1 is an ion source, for example, a source that generates negative ions; 2 is an analysis magnet; 3 is an acceleration tube; 4 is a scanner that utilizes electrostatic or electromagnetic phenomena; and 5 is a wafer installed at an end station 6.

The above configuration is not particularly different from the conventional configuration,
One of the ions from the ion source 1 is analyzed by the magnet 2
Only the desired ions are analyzed. This is then accelerated by the accelerating tube 3.

It is scanned by a scanner 4 and implanted onto a wafer 5.

In this case, since the implanted ions are charged, as the beam current increases, the wafer 5 is charged up, as described at the beginning.

According to the invention, a neutralizer 7 is installed after the scanner 4. The neutralizer 7 collects accelerated ions (charged particles)
By passing the ions through a low-pressure gas (for example, argon gas) or through a thin metal foil, the ions are neutralized or charged.

The neutralizer 7 emits electrons for positive ions, and acquires electrons for negative ions, thereby converting them into neutral particles that are neutral in potential. It is convenient to use a negative ion source as the ion source 1 because the efficiency of producing neutral particles increases.

The particles that have passed through the neutralizer 7 are then subjected to a magnetic field of a separator, such as a separating magnet 8 (the direction of the magnetic field is shown in the paper).

(at right angles) to pass through. Then, the charged particles that have not been neutralized are separated by the neutralizer 7.

The separated charged particles are absorbed by the damper 9.

The separator 8 may separate by an electric field.

Most of the particles that have passed through the separator 8 become neutral particles. Therefore, even if this is injected into the wafer 5, the wafer 5 will not be charged up. Then, required impurities can be implanted as desired.

Note that neutral particles cannot be scanned by a magnetic field or an electric field, so it is necessary to install a scanner 4 upstream of the neutralizer 7 as shown in the figure. In step 6, the wafer 5 may be mechanically scanned.

In the configuration described above, the ion source is at a high potential and the end station is at ground potential, but if necessary, a charged drift tube may be installed between the neutralizer 7 and the separator 8 to The end station may be at ground potential and the neutralizer may be at high potential.

(Effects of the Invention) As detailed above, according to the present invention, even when a large current beam is implanted when implanting impurities into a wafer, it is possible to avoid the charge-up phenomenon of the wafer. play.

[Brief explanation of the drawing]

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

Claims (1)

[Claims] an acceleration tube that accelerates ions from an ion source; a neutralizer that neutralizes the ions accelerated by the acceleration tube to produce neutral particles; and a neutralizer that converts charged particles from among the particles that have passed through the neutralizer. An impurity injection device comprising: a separator for separating neutral particles; and an end station for installing a wafer into which neutral particles that have passed through the separator are injected.