JPS63299043A - Ion implantation device - Google Patents

Abstract

PURPOSE:To prevent electrostatic destruction by charge of an objective by forming an electric field returning a secondary electron generated when ion is implanted into the objective to the objective. CONSTITUTION:A periphery of an objective 13 such as a semiconductor wafer etc., is wrapped with an insulation material 14 in constitution. Consequently, a negative electric field is formed on the material 14 surface with a negative secondary electron 16 emitted when ion is implanted accumulated on the material 14 surface, and the electron 16 further emitted is repulsed and returned to the objective 13. This enables electrostatic destruction by charge of the objective to be prevented with deflection of an ion beam 11 by an accumulated positive charge on the objective 13 prevented and an accurate ion implantation quantity measuring possible.

Description

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

(Prior Art) Generally, in order to form a semiconductor integrated circuit, an ion implantation process is performed in which impurity ions generated in an ion source are accelerated with a high electric field and implanted into a semiconductor substrate to determine the characteristics of the semiconductor. In such an ion implantation apparatus, positively charged ions are accelerated and collided with a target object such as a semiconductor sea urchin, thereby doping the target object with an impurity. For this reason, when accelerated positive ions collide, electrons are ejected from the target object, causing the target object to become positively charged and the amount of ions implanted to be uneven.This positive charge may accumulate on the insulator part of the target object, causing it to become static. Electrical breakdown may occur, or the amount of ions implanted may not be able to be captured by the number of ejected electrons.

Therefore, some conventional ion implantation devices are configured to supply electrons to the target object using the electronic Java method or the like to prevent the target object from being charged. There is one disclosed in Japanese Unexamined Patent Publication No. 61-227357.

According to this, an ion beam ω emitted from an ion beam generator (not shown) is accelerated to final energy by an accelerating electrode (not shown), and only desired positive ions are selected by a magnetic field controlled by a mass analyzer (not shown).
It is scanned by a magnetic field of a deflection system (not shown), passes through a Faraday cup (2), and is irradiated onto a target object such as a semiconductor wafer held on a mounting table (2). Then, the negative secondary muntin (2) generated from the semiconductor wafer (1) by the positive ion beam (2) implantation is returned into the Faraday cup (3) made of a conductive material by the action of the magnetic field of the electromagnet (2) equipped with a power source (0). As a result, the secondary muntin (■) does not fly out of the Faraday cup (■) and is returned to the semiconductor wafer () or taken into the Faraday cup (■), so the amount of ions implanted can be accurately measured using an ammeter (■). can be applied to semiconductor wafers) to 2
A part of the next electron 0 is returned to the semiconductor wafer)
electrification is alleviated to some extent.

(Problems to be Solved by the Invention) However, in the conventional ion implantation apparatus described above, since the ion beam ω passes through the magnetic field of the secondary electron (c) suppressing electromagnet ■, it is selected by a mass analyzer (not shown). Some of the implanted ions are lost or diverged, and the scanning speed and ion implantation angle, which are controlled by a deflection system (not shown), change slightly. As a result, there have been problems such as non-uniform ion implantation amount and implant depth, insufficient ions, and undesired ion quality.

In addition, simply returning the secondary muntin ■ to the Faraday cup ■ made of conductive material will not allow the two to be taken into the Faraday cup ■.
There are many cases where the positive charge accumulated on the semiconductor wafer (A) is not sufficiently neutralized, and electrostatic damage occurs due to the charging of the semiconductor wafer (A). Moreover, the ion beam ω is applied to the wafer (A). There was a problem of deflection due to accumulated positive charges.

Furthermore, since an electromagnet (2) or the like is used to return the secondary muntin (2), there is a problem that the device becomes large and expensive.The present invention was made to address the above-mentioned problems.

The present invention provides an ion implantation apparatus capable of uniformly and accurately implanting desired ions into a target object such as a semiconductor wafer, and performing ion implantation processing that prevents electrostatic damage due to charging of the target object.

[Structure of the invention]

(Means for Solving the Problems) The present invention is characterized in that an electric field is formed to return secondary electrons generated during ion implantation into a target object to the target object.

(Function) In the ion implantation apparatus of the present invention, the periphery of a target such as a semiconductor sea urchin is wrapped in an insulating material, so that negative secondary electrons emitted during ion implantation are accumulated on the surface of the insulating material. A negative electric field is formed on the surface of the insulating material, and the emitted negative secondary electrons are repelled and returned to the target object.As a result, the ion beam is not affected by the ion beam and is caused by the accumulated positive charges on the target object. It is possible to prevent deflection of the target object, accurately measure the amount of ion implantation, and sufficiently prevent electrostatic damage due to charging of the target object.

(Example) Hereinafter, an example of the ion implantation angle of the present invention will be described with reference to the drawings.

An ion beam (11) of impurities such as boron or arsenic is ejected from an ion beam generator (not shown).
The desired positive ions are accelerated to the final energy by an accelerating electrode (not shown) at a voltage of, for example, 80 KV, and then only the desired positive ions are extracted using the magnetic field of a mass analyzer (not shown), such as an analyzer magnet. Set the desired scan speed and injection angle.

Then, on the mounting table (12), for example, an aluminum disk,
A target such as a semiconductor wafer (13) is provided so as to be irradiated with the ion beam (11).

Further, a rectangular cylindrical channel tube (15) having an insulating material (14) such as an insulating film of silicon or aluminum oxide formed on the inner wall is provided to surround the periphery of the semiconductor wafer (13). ing. An electrode (17) is set at the ion beam (11) input end of the Faraday cup (15) so as to return secondary electrons (16) generated during ion implantation into the Faraday cup (15).

Note that an ammeter (18) is connected and installed so as to measure the amount of ion implantation flowing into the semiconductor wafer (13) as an ion current.

Next, a method for implanting ions into a semiconductor wafer using the above-mentioned ion implantation apparatus will be described.

A positive ion beam (11) selected and accelerated as desired passes through a Faraday cup (15) and is injected into a semiconductor wafer (13) held on a mounting table (12). In this process, the ion beam (11) is attached to the semiconductor wafer (13).
By colliding with the secondary electrons (16), the semiconductor wafer (13) generates secondary electrons (16). And this secondary electron (16
) lands on the surface of the insulating material (14) provided on the inner wall surface of the Faraday cup (15). In the initial state where there is no charge, the secondary electrons (16) accumulate and increase negative charges on the surface of the insulating material (14). However, when the negative voltage on the surface of the insulating material (14) rises to the maximum energy of the secondary electrons (16) generated, that is, the same potential as the wafer substrate surface potential, for example, 100 aV, the insulating material (14)
4) Repulsed by the negative electric field on the surface, as shown in Figure 2, 2
The secondary electrons (14) return to the semiconductor wafer (13). Then, the positive ion charges (21) accumulated on the semiconductor wafer (13) during ion implantation are neutralized by the returned secondary electrons, and the charge accumulation on the semiconductor wafer (13) is reduced.

As a result, electrostatic damage to targets such as semiconductor wafers (13) can be prevented.

Deflection of the ion beam (11) due to positive ion charges (21) accumulated on the wafer (13) can be prevented, and accurate and uniform ion implantation can be performed.

Further, the secondary electrons that are about to jump out of the Faraday cup (15) can also be removed by applying a pressure of, for example, about -1000 V to the electrode (17) with respect to the Faraday cup (15).

The semiconductor wafer (1) passes through the Faraday cup (15).
3), the positive ion charge (21) of the wafer (13) is
) and neutralize it.

Furthermore, the secondary electron (16) is the Faraday cup (15)
Because the ion beam (13) returns to the target object, the semiconductor wafer (13), without being absorbed by the ion beam (1
Since the ion current (1) can be measured accurately, the amount of ion implantation can also be accurately determined.

As described above, accurate ion implantation can be performed, electrostatic damage to the target semiconductor wafer (13) is prevented, and uniform ion implantation is completed.

In the above embodiment, the electrode (17) to which a high voltage was applied was used as a means for returning the secondary electrons (16) ejected from the Faraday cup (15), but as shown in FIG. The incident end of the ion beam (11) is closed with the inner insulating material (31) of the cup (15), and a slit hole (32) for the ion beam (11) is provided there. Secondary electrons (16
) may be returned to the semiconductor wafer (13).

Furthermore, although silicon or aluminum oxide was used as the material of the insulating material (14) in the above embodiment, any insulating material that does not contain impurities may be used, and it goes without saying that the material is not limited to the above embodiment. According to this embodiment, negative secondary electrons generated during ion implantation are returned to the semiconductor wafer by a negative electric field accumulated on the surface of the insulating material by configuring the periphery of the semiconductor wafer with an insulating material. By neutralizing the positive charges on the wafer caused by the positive ion beam, the ion implantation amount can be measured accurately, and electrostatic damage caused by positive charges accumulated on the wafer and deflection of the ion beam can be prevented. Uniform ion implantation can be performed.

〔Effect of the invention〕

As explained above, according to the present invention, by forming an electric field that returns the secondary electrons generated during ion implantation to the target object, the scanning speed of the ion beam, the implantation angle, and the ion It improves the uniformity of implantation depth and implantation depth without changing the quantity or quality of ion implantation, and allows accurate measurement of ion implantation amount.

Electrostatic damage due to charging of the target object and deflection of the ion beam can be prevented, and a small and inexpensive ion implantation device can be realized.

[Brief explanation of drawings]

Fig. 1 is a block diagram of the ion implantation apparatus of the present invention, Fig. 2 is a diagram showing the movement of charges in Fig. 1, Fig. 3 is a block diagram of another embodiment of Fig. FIG. 1 is a configuration diagram of an ion implantation device. In the figure,

Claims (2)

[Claims] (1) An ion implantation apparatus that implants ions by irradiating an ion beam onto a target object, characterized in that an electric field is formed to return secondary electrons generated during ion implantation into the target object to the target object. Ion implanter. (2) The means for forming an electric field for returning secondary electrons to the target object is characterized in that a path tube is provided in the ion beam incident path, and the inner wall surface of this path tube is formed of an insulating material. The ion implantation device according to item 1.