JPH04225222A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To neutralize electric charge which is charged on the surface of a wafer completely by controlling the supplied amount of electrons only for the amount of ions which are implanted into the wafer when the electrons are supplied into the wafer supported on a disk and the ions are implanted into the wafer. CONSTITUTION:A disk 2 and a wafer 1 are electrically insulated. Positive ions are supplied into both the disk and the wafer in ordinary ion implantation. A current Idisc and a current Iwafer flow to GND from the disk 2 and the wafer 1. At this time, when the ions are implanted into the wafer 1 with electrons being supplied, the electrons are supplied into the disk 2 and the wafer 1, and the values of the currents Idisc and Iwafer become small by the amount of the supplied electrons. In some cases, the values become the negative values. Then, negative feedback is applied on a power supply 8 for a filament 4 so that the value can be maintained at the preset value (O) of the current Iwafer, and the supply of the electrons is controlled. Thus, the electric charge on the wafer 1 is completely neutralized.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing semiconductor devices, and more particularly to a method for preventing wafer charge-up during an ion implantation process.

As the gate insulating film becomes thinner due to the miniaturization of MOS devices, the gate insulating film frequently deteriorates due to the charge-up of the wafer due to ion implantation.This is a major problem in terms of device reliability, and countermeasures are desired. There is.

For this reason, the positive charges generated on the wafer during ion implantation are neutralized by supplying electrons, but conversely, the oversupply of electrons causes negative charges to build up on the gate insulating film. This may cause deterioration, so the amount of electrons supplied must be controlled so that it is always appropriate.

The present invention can be used as a method for controlling the amount of electron supply that meets this need.

[0005]

2. Description of the Related Art FIG. 3 is a block diagram illustrating a conventional example. In the figure, 1 is a wafer, 2 is a disk, 3 is an ion beam, 4 is a filament for supplying electrons for an electron shower, and 5 is a disk ammeter.

In the conventional ion implantation apparatus, since the ion beam 3 is irradiated onto the disk 2 holding the wafer 1, positive charges are accumulated on the disk 2, and the disk 2 and GND are irradiated with the ion beam 3.
A current Idisc flows between them. Therefore, Idi
It is thought that by supplying electrons from the filament 4 to the disk 2 at the same time as the ion beam 3 so that sc = 0, the charge on the entire disk 2 is neutralized, and the charge on the wafer is also neutralized accordingly. was.

However, in reality, the disk surface and the wafer surface have different insulating properties, resulting in a difference in the amount of charge on the surface, so even if the entire disk is neutralized, the charge on the wafer is not necessarily neutralized.

[0008]

[Problem to be solved by the invention] In the conventional example, only the charge on the entire disk was controlled, so depending on the surface conditions of the disk and wafer, the charge on the wafer surface could not be completely neutralized and could become positively or negatively charged. This caused deterioration of the gate insulating film.

An object of the present invention is to completely neutralize the charges that are accumulated on the wafer surface during ion implantation.

0010

[Means for Solving the Problem] The above problem is solved by electrically insulating the wafer from the disk when ion implantation is performed on the wafer held by the disk while supplying electrons to the wafer. Measure the current between the wafer and ground potential,
This is achieved by a semiconductor device manufacturing method that controls the amount of electron supply by feeding back the current value to the electron supply means to prevent the wafer from being charged.

[0011]

[Operation] The present invention completely neutralizes the charges on the wafer surface by controlling the amount of electrons supplied only with respect to the amount of ions implanted into the wafer.

FIG. 1 is a diagram explaining the principle of the present invention. In the figure, 5 is a disk ammeter and 6 is a wafer ammeter. The disk 2 and the wafer 1 are electrically insulated, and a current I is generated between the disk 2 and GND for the positive ions implanted.
disc flows, and a current Iwafer flows between the wafer 1 and GND. Therefore, in the present invention, Iw
By controlling the supply of electrons by applying feedback to the current supplied to the filament 4 so that afer =0, the charges on the wafer are completely neutralized.

[0013]

Embodiment FIG. 2 is a block diagram illustrating an embodiment of the present invention. In the figure, 1 is a wafer, 2 is a disk, 3 is an ion beam, 4 is a filament, 5 is a disk ammeter,
6 is a wafer ammeter, 7 is a wafer clamp, 8 is a filament variable power source, 9 is an electron acceleration power source, 10 is a Faraday cup, 11 is a bias ring, and 12 is a beam ammeter.

The figure shows the end station portion of the ion implanter. Approximately ten wafers 1 are held on the circumference of the surface of a disk 2, and ions are sequentially implanted into the wafers by rotating the disk 2.

In conventional ion implantation, positive ions are supplied to both the disk and the wafer. Therefore, if there is no electron supply, the disk and wafer will go to GND.
Idisc and Iwafer flow. On the other hand, when electrons are supplied, electrons are supplied to the disk and wafer, and the values of Idisc and Iwafer become smaller by the amount of supplied electrons, or in some cases become negative values.

[0016] In the embodiment, the preset Iwafe
The electric charge on the wafer is completely neutralized by applying feedback to the power supply 8 of the filament 4 and controlling the supply of electrons so that the value of r (generally 0) can be maintained.

[0017]

[Effects of the Invention] It has become possible to completely neutralize the electric charge that is accumulated on the wafer surface during ion implantation.

As a result, deterioration of the device due to charging could be suppressed, contributing to improved reliability.

[Brief explanation of the drawing]

[Figure 1] Diagram explaining the principle of the present invention

[Figure 2] Block diagram illustrating one embodiment of the present invention

[Figure 3
] Configuration diagram explaining a conventional example

[Explanation of symbols]

1 Wafer 2 Disc 3 Ion beam 4 Filament 5 Disc ammeter 6 Wafer ammeter 7 Wafer clamp 8. Variable power supply for filament 9　Electron acceleration power source 10 Faraday Cup 11 Bias ring 12 Beam current meter

Claims (1)

[Claims] Claim 1: When ion implantation is performed on a wafer held by a disk while supplying electrons to the wafer, the wafer is electrically insulated from the disk and the current between the wafer and the ground potential is measured. A method for manufacturing a semiconductor device, characterized in that the current value is fed back to the electron supply means to control the amount of electron supply to prevent the wafer from being charged.