JPH0787087B2 - Ion implanter - Google Patents

Description

The present invention relates to an apparatus for implanting impurity ions into a semiconductor wafer.

[Conventional technology]

There is an ion implantation method as a method of forming an impurity layer on a semiconductor wafer. FIG. 3 is a schematic view showing an ion implantation apparatus used for ion implantation, for example, a mechanical scan type ion implantation apparatus. FIG. 4 is a partial plan view showing a disk of an essential part of this ion implantation apparatus, and FIG. 5 is a sectional view taken along line VV of FIG.

In FIGS. 3 to 5, 1 is an ion source for generating ions, 2 is arranged in front of the ion source 1, and a mass analysis magnet 3 for extracting necessary ions is arranged in front of the mass analysis magnet 2. A disk made of a rotatable and translatable conductor, 4 is an ion beam emitted from the ion source 1, and 5 is a semiconductor wafer (hereinafter, simply referred to as a "wafer") to be processed, which is placed on the disk 3. Reference numeral 6 is a clamp which is attached to the disk 3 and which can be opened and closed freely and which fixes the wafer 5.

The wafer 5 is manufactured by using the ion implantation apparatus configured as described above.
Then, ion implantation is performed as follows. First, the ion beam 4 set in a predetermined state is emitted from the ion source 1. At this time, the ion beam 4 is shielded by a beam stopper provided between the mass analysis magnet 2 and the disk 3. Next, the wafer 5 is transferred to the disk 3 and placed at a predetermined position. Then, the clamp 6 which has been in the open state is brought into the closed state, and each wafer 5 is fixed. Next, the disk 3 in the initial position rotates at a predetermined rotation speed, and translational movement is performed. Here, the beam stopper is opened, and the ion beam 4 is incident on the wafer 5. The ion beam 4 is extracted from the ion source 1, desired impurity ions are extracted by the mass analysis magnet 2, and are incident on the wafer 5. Disk 3
While simultaneously rotating, the translational motion is simultaneously performed, and the ion implantation is performed on the entire surfaces of the plurality of wafers 5. At this time, the inside of the ion implanter is kept in a high vacuum state of the order of 10 ⁻⁷ Torr.

By the way, in many cases, elements are formed when the ion implantation is performed, that is, on the wafer 5. An example thereof is shown in FIG. In the figure, the wafer 5 is a P-type substrate, a thick field oxide film 7 is formed on the surface of the substrate, and a gate oxide film is formed in a part of the active region sandwiched by these field oxide films 7. A thin oxide film 8 is formed, and a gate electrode 9 is formed thereon. An oxide film 10 is formed on the back surface of the wafer 5, and a side surface oxide film 11 is formed on the side surface. In this state, the ion beam 4 is placed on the wafer 5.
Are implanted to form N-type source / drain.

[Problems to be Solved by the Invention]

Since the ion implantation process in the conventional semiconductor device manufacturing process is performed as described above, the wafer 5 is in a state of being covered with an insulating film, and there is no escape route for ion charges (plus charge). The injection is performed. As a result, the ionic charges are accumulated in the field oxide film 7, the gate oxide film 8, etc., and the surface potential of the insulating film gradually increases,
Eventually, there was a problem of causing electrostatic breakdown, resulting in device destruction.

The present invention has been made in view of the above points, and an object thereof is ionic charge (plus charge).
The purpose of the present invention is to obtain an ion implanter capable of preventing the dielectric breakdown by eliminating the charge-up due to.

[Means for Solving the Problems]

In order to solve such a problem, the present invention provides a vacuum chamber for implanting impurity ions into a semiconductor wafer,
A tip metal electrode and a gas supply means for feeding gas to the tip of the tip metal electrode are provided, a negative high voltage is applied to the tip metal electrode to locally generate corona discharge, and gas molecules generated by this corona discharge The negative ions are sent to the vicinity of the semiconductor wafer by the gas supply means.

[Operation] In the ion implantation apparatus according to the present invention, negative ions of gas molecules locally generated by corona discharge are blown into the positively charged semiconductor wafer to neutralize the surface of the semiconductor wafer.

〔Example〕

 Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the ion implantation apparatus according to the present invention. In the figure, 1 is an ion source, 2 is arranged in front of the ion source, a mass analysis magnet for extracting necessary ions, 3 is arranged in front of the mass analysis magnet 2, and is a disk made of a conductor that can rotate and translate. Reference numeral 4 denotes an ion beam emitted from the ion source 1, 5 denotes a semiconductor wafer to be processed which is placed on the disk 3, 6 is attached to the disk 3 and can be freely opened and closed, and the wafer 5 is fixed. It is a clamp.

Further, 12 is a box kept in a vacuum chamber containing the wafer 5 at a degree of vacuum capable of corona discharge, and 13 is a box 12
A metal electrode inside (eg, an electrode made of W), 14 is a high-voltage DC power source connected to the metal electrode 13, 15 is a gas pipe made of SUS extending to the vicinity of the tip of the metal electrode 13, 16 Is a gas such as O ₂ flowing in the gas pipe 15.

At the time of ion implantation, first, the ion beam 4 set to a predetermined state is emitted from the ion source 1. At this time, the ion beam 4 is shielded by a beam stopper provided between the mass analysis magnet 2 and the disk. Next, the wafer 5 is transferred to the disk 3 and placed at a predetermined position. Then, the clamp 6 which has been in the open state is brought into the closed state, and each wafer 5 is fixed. Next, the disk 3 in the initial position rotates at a predetermined rotation speed, and translational movement is performed. Here, the beam stopper is opened, and the ion beam 4 is incident on the wafer 5. At this time, at the same time, a negative high voltage is applied to the tip metal electrode 13 in the box 12 having a low degree of vacuum, and a gas (for example, F ₂ gas) 16 is caused to flow there through the gas pipe 15 so that the tip of the electrode 13 A corona discharge 17 (see FIG. 2) is locally generated, and negative ions 18 of gas molecules such as F ⁻ (see FIG. 2) are generated there and blown onto the wafer 5 on which the ion beam 4 is incident,
The surface of the positively charged wafer 5 is neutralized. Figure 2 shows
FIG. 3 is a detailed view showing a part of FIG. 1 in detail for explaining the above operation.

Although F ₂ gas is shown as an example of gas in the above-mentioned embodiment, gas such as O ₂ is also considered, and O ₃ ⁻ and O ⁻ are generated by corona discharge.

〔The invention's effect〕

INDUSTRIAL APPLICABILITY As described above, according to the present invention, a corona discharge is locally generated, and negative ions of gas molecules generated there are sent to a wafer in a chamber to neutralize a positively charged wafer by an ion beam and generate an electrostatic charge. It has the effect of preventing destruction.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of the ion implantation apparatus according to the present invention, FIG. 2 is a detailed view showing a part of FIG. 1 in detail, and FIG. 3 is a conventional ion. Schematic diagram showing an outline of the injection device, fourth
FIG. 7 is a partial plan view showing a disk of the apparatus of FIG. 3, FIG. 5 is a sectional view taken along line VV of FIG. 4, and FIG. 6 is an explanatory view showing an example of an element portion of the device at the time of ion implantation. . 1 ... Ion source, 2 ... Mass analysis magnet, 3 ... Disk, 4 ... Ion beam, 5 ... Wafer, 6 ... Clamp, 12 ... Box, 13 ... Tip metal electrode, 14 ...
DC high-voltage power supply, 15 …… gas piping, 16 …… gas, 17 ……
Corona discharge, 18 ... Negative ions of gas molecules.

Claims (1)

[Claims] 1. A vacuum chamber for injecting impurity ions into a semiconductor wafer is provided with a tip metal electrode and a gas supply means for feeding gas to the tip of the tip metal electrode, and the tip metal electrode has a negative height. An ion implanter characterized in that a voltage is applied to locally generate corona discharge, and negative ions of gas molecules generated by this corona discharge are sent to the vicinity of a semiconductor wafer by the gas supply means.