JPH03216945A - Ion implanter - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application in Industry 1] The present invention relates to an ion implantation device used for forming an impurity layer on a semiconductor substrate. [Prior Art] Fig. 4 is a schematic side view of a conventional ion implantation device. It consists of an ion source (2) that generates ions, and an extraction electrode (3) that electrostatically extracts and accelerates the ion source (2). (4) is a magnetic field deflection type mass analyzer that analyzes the mass of the necessary dopant ions in the ion beam (5) emitted from the ion source section (1), and (6) is a purchase quantity analysis H (4).
A shaping slit (7) is used to adjust the shape of the ion beam (5) analyzed by the shaping slit (6), and an analysis slit (7) is used to select the required dopant ions from the ion beam (5) shaped by the shaping slit (6). (8) is the analytical slit (7
) is a charge neutralizer that neutralizes the charge of the ion beam (5) analyzed by the electron gun (9). It consists of a Faraday gauge (10) for measurement. (11
) is the ion beam (5) passing through the charge neutralizer (8)
(12) is a disk interposed between the charge neutralizer (8) and the beam catcher (1l), and (13) is a semiconductor substrate placed on the disk (12). When ion implantation is performed on this semiconductor substrate (13), a pattern is usually formed. An example of a patterned semiconductor substrate (13) is shown in Fig. 5. In Fig. 5, the semiconductor substrate (13) is For example, the thin insulating film (21) is of P conductivity type and is formed on the main surface of this semiconductor substrate (13).
) is formed on the gate electrode (22), and a thick insulating film (2o) is formed with a thin insulating film (2l) in between, and in this state, ions are formed on both sides of the gate electrode (22). The idea is to use implantation to form an impurity region that will become a source train.

A conventional ion implantation apparatus is constructed horizontally as described above, and the semiconductor substrate (13) is placed on the disk (12), and the disk (12) moves in what is commonly called a mechanical scan method, as shown by the arrow in FIG. Ion implantation is performed by rotating at a predetermined rotational speed as shown at A and parallel movement as shown by arrow B in Figure 4. That is, the ion beam (5) emitted from the ion source (1) is extracted with a desired acceleration energy by the extraction electrode (3). Accelerated ion beam (
5) Selects necessary dopant ions using mass spectrometry 3 (4), shaping slit (6), and analysis slits (7), and prepares the shape of the target semiconductor substrate (13).
You will be guided to. In this case, the ion beam (5) is, for example, an ion beam of boron, phosphorus, arsenic, etc. in order to form the source/drain to be of N conductivity type. This ion beam (5) is guided to the semiconductor substrate (13),
When ions are directly implanted with a beam current of 1 mA or more, charge-up causes breakdown of the thin insulating film of the semiconductor substrate (13) (commonly known as dielectric breakdown) and electrostatic breakdown. ) is provided with a charge neutralizer (8) immediately before it hits.

The operating principle of this charge neutralizer (8) is shown in FIG.

As shown in Figure 6, the action of the charge neutralizer (8) is to accelerate the primary electrons emitted from the electron gun (9) with an electric field of about 300V, and to (
10》 to generate secondary electrons (23), and supply the secondary electrons (23) to the semiconductor substrate (13) to generate positive charges accumulated on the gate electrode (22) of the semiconductor substrate (13). This prevents dielectric breakdown of the thin insulating film (21) serving as the gate insulating film and electrostatic breakdown of the gate electrode.

[Problem to be solved by the invention]

In the conventional ion implanter as described above, an electron gun (9)
The positive charge accumulated on the gate electrode (22) is neutralized by the secondary electrons (23) generated from the surface of the Faraday gauge (10) by the irradiation of the primary electrons emitted from the Faraday gauge (10). Some of them are Faraday gauge (10
) to reach the semiconductor substrate (13) by reflection of
There was a point where the semiconductor substrate (13) was negatively charged up, causing dielectric breakdown due to the negative charge, and even though dielectric breakdown did not occur, the gate insulation 11Q (22) was deteriorated.

This invention was made to solve the above-mentioned problems, and aims to provide an ion implantation device that prevents dielectric breakdown and deterioration of the gate insulating film. [Means for Solving the Problems] An ion implantation apparatus according to the present invention is equipped with a charge neutralizer having a confinement means for trapping secondary electrons generated by irradiation with an ion beam.

[For production]

In this invention, secondary electrons generated by ion beam irradiation are trapped by a charge trapping means, and the trapped secondary electrons are returned to the semiconductor substrate.

〔Example〕

Examples of the present invention will be described below. FIG. 1 is a schematic side view showing an embodiment of the present invention, and FIG.
Figure 3 is an enlarged perspective view of the charge neutralizer in Figure 2, and Figure 3 is an explanatory diagram of the operation of the charge neutralizer in Figure 2. The same or equivalent parts as in Figures 4 to 6 described above are designated by the same reference numerals. and the explanation thereof will be omitted.

In the figure, (30) indicates a charge neutralizer, which is provided on the outer periphery of the Faraday gauge (lO). Charge neutralization H
(30) has a plurality of permanent magnets (3l) serving as charge confinement means arranged at predetermined intervals around the path of the ion beam (5), that is, around the outer circumference of the Faraday gauge (10), as shown in FIG. They are arranged in parallel in order to generate a magnetic multipolar magnetic field (32) around the inner periphery of the Faraday gauge (10) without adversely affecting the course of the ion beam (5).

”. In the ion implantation apparatus as described above, an ion beam containing dopant ions such as poron, arsenic, phosphorous, etc. ions necessary for forming an impurity layer is emitted from the ion source (1) at an acceleration voltage of 80 KV. (5), and select only the necessary douband ions using the mass spectrometer (4) and analysis slit I/(6). The ion beam (5) of selected douband ions is directed to a disk (12) in which the rotation of arrow A and the parallel movement of arrow B are performed, and a semiconductor substrate (13) placed on this disk (12).
), charge neutralizer (:+0) and 7 Allade gauge (1
0), and ions are implanted into the semiconductor substrate (13). In this step, as shown in FIG. 3, secondary electrons (40) are generated in the semiconductor substrate (13) and the disk (12) by irradiation with the ion beam (5). The generated secondary electrons (40) are measured by a Faraday gauge (10
) to be jumped into. The injected secondary electron (40) is moved by a Faraday gauge (10
) you can jump inside. Trapped secondary electron (40
) is a sublessor? ! It is returned to the interior of the Faraday gauge (10) by the CF & (not shown), and is confined therein by the confinement effect of the magnetic multipolar magnetic field (32) within the Faraday gauge (10), and is returned to the semiconductor substrate (
Returning to step 13), the positive charges on the semiconductor substrate (13) are neutralized.

In this embodiment, the charge neutralizer (30) is 12
An example is shown in which 12 permanent magnets (31) are used around the outer circumference of the Faraday gauge (10) in order to generate a magnetic multipolar magnetic field (32), but the number is not limited to this number. The permanent magnet (31) may be replaced with an electromagnet or the magnetic multipolar field (32) may be formed by other means.

〔Effect of the invention〕

As described above, according to the ion implantation apparatus of the present invention, secondary electrons generated from a semiconductor substrate or a disk during ion implantation are trapped in a Faraday gauge that forms a magnetic multipolar magnetic field and returned to the semiconductor substrate again. The provision of the charge neutralizer has the effect of preventing dielectric breakdown and electrostatic breakdown of the gate insulating film without requiring a conventional electron gun for generating secondary electrons.

[Brief explanation of drawings]

Fig. 1 is a schematic side view of an ion implanter showing an embodiment of the present invention, Fig. 2 is an enlarged perspective view of the charge neutralizer shown in Fig. 1, and Fig. 3 is a charge neutralizer shown in Fig. 2. FIG. 4 is a schematic side view showing an example of a conventional ion implantation device, FIG. 5 is an explanatory diagram for explaining the semiconductor substrate shown in FIG. 4, and FIG. This is a diagram explaining the operation of the charge neutralizer. In the figure, (5) is an ion beam, (13) is a soil conductor substrate, (30) is a charge neutralizer, (31) is a permanent magnet,
(32) indicates a magnetic multipolar magnetic field, and (40) indicates a secondary electron. In each figure, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Claims] In an ion implantation apparatus that forms an impurity layer by irradiating a semiconductor substrate with an ion beam, a charge neutralizer is provided on the front surface of the semiconductor substrate and has a charge confinement means for confining secondary electrons generated by the ion beam irradiation. An ion implantation apparatus, wherein the charge confinement means surrounds the ion beam path with a plurality of magnets to form a multipole magnetic field in a range that does not affect the ion beam path.