JPH04188824A - Ion-implantation method - Google Patents

Abstract

PURPOSE:To restrain the emission of the secondary electrons from the capacitor structure part for restraining the accumulation of positive charge and further avoiding the electrostatic breakdown in the capacitor part by a method wherein the whole surface of the structure part, after being covered with an insulator, is implanted with ions. CONSTITUTION:The whole surface of a capacitor structure formed of a polycrystalline silicon film 3, an insulating film 4 and another polycrystal silicon film 5 is covered with a photoresist 6 as an insulator to be ion-implanted later. At this time, the film 5 is also irradiated with ion beams 7 through the intermediary of the first resist 6 but the emission of the secondary electrons from the film 5 is restrained by the resist 6 comprising insulator so as to restrain the accumulation of positive charge. Furthermore, the surface of the resist 6 is carbonized by the irradiation with the ion beams 7 to make the resist 6 conductive. Resultantly, the positive charge is relieved from the resist 6 further restraining the positive charging. Through these procedures, the electrostatic breakdown in the capacitor structure part can be avoided.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an ion implantation method for implanting ions into a semiconductor device having a capacitor structure on a semiconductor substrate.

[Conventional technology]

FIG. 2 is a diagram for explaining a conventional ion implantation method when implanting ions into a semiconductor device having a capacitor structure on a semiconductor substrate.

An oxide film 2 is provided on the semiconductor substrate 1, a first polycrystalline silicon film 3 is provided on the oxide film 2, and an insulating film (oxide film, etc.) 4 for a capacitor is provided on the first polycrystalline silicon film 3. , a second polycrystalline silicon film 5 is formed on the insulating film 4, respectively.

First polycrystalline silicon film 3. The insulating film 4 and the second polycrystalline silicon film 5 constitute a capacitor structure.

Ions (A) are used to form, for example, source/drain regions in semiconductor devices having such capacitor structures.
When implanting s, B), the affected regions where the conductivity type changes unfavorably or the impurity concentration changes unfavorably due to the ion implantation are covered with a resist, and other regions, such as those shown above, are covered with resist. The exposed capacitor structure was not covered with resist. The reason why the capacitor structure shown above is not affected by the ion implantation is as follows. That is, the impurity concentration of the polycrystalline silicon film 5 is generally higher than the impurity concentration obtained by ion implantation, and the conductivity type of the ions implanted by ion implantation is often the same as that of the polycrystalline silicon film 5.

[Problem to be solved by the invention]

Since the conventional ion implantation is performed without covering the capacitor structure with resist as described above, the polycrystalline silicon film 5 is directly irradiated with the ion beam 7. However, although the properties of the second polycrystalline silicon film 5 do not change, the ion beam 7 is applied directly onto the second polycrystalline silicon film 5.
In addition to accumulating positive charges, secondary electrons generated from the second polycrystalline silicon film 5 by irradiation with the ion beam 7 further promote the accumulation of positive charges in the second polycrystalline silicon film 5. There is a problem in that the insulating film 4 that insulates the first and second polycrystalline silicon films 3.5 is damaged by electrostatic discharge.

The present invention was made to solve the above-mentioned problems, and an object of the present invention is to provide an ion implantation method that does not cause electrostatic damage to the capacitor structure.

[Means to solve the problem]

The present invention is applied to ions and an implantation method for implanting ions into a semiconductor device having a capacitor structure on a semiconductor substrate.

The ion implantation method according to the present invention is characterized in that ions are implanted after the entire surface of the capacitor structure is covered with an insulator.

[Effect]

In this invention, since ions are implanted after the entire surface of the capacitor structure is covered with an insulator, the emission of secondary electrons from the capacitor structure is suppressed.

〔Example〕

FIG. 1 is a diagram for explaining an embodiment of the ion implantation method according to the present invention. In the figure, the difference from the conventional ion implantation method is that, as shown in FIG. The entire surface is covered with a photoresist 6, which is an insulator, and then the source
Ion implantation is performed to form a drain region and the like. At this time, the ion beam 7 is also applied to the polycrystalline silicon film 5 through the photoresist 6, but since the photoresist 6 is an insulator, the emission of secondary electrons from the polycrystalline silicon film 5 is suppressed. Accumulation of positive charges in the polycrystalline silicon film 5 is suppressed compared to the prior art.

As a result, the insulating film 4 will not be damaged by electrostatic discharge.

Further, if the photoresist 6 contains carbon, the surface of the photoresist is carbonized by irradiation with the ion beam 7, and the surface becomes conductive. As a result, the positive charges generated by the irradiation with the ion beam 7 escape along the surface of the photoresist 6, and in combination with the above-mentioned suppression of the emission of secondary electrons, it is possible to further suppress the charging of the polycrystalline silicon film 5 with positive charges. .

Note that in the above embodiment, polycrystalline silicon film 3 - insulating film 4 -
Although the capacitor structure is made of the polycrystalline silicon film 5, the capacitor structure may have another structure, for example, a semiconductor substrate-insulating film-polycrystalline silicon film structure.

Further, in the above embodiment, the entire surface of the capacitor structure was covered with the photoresist 6, but the photoresist is not limited to any insulating material.

〔Effect of the invention〕

As described above, according to the present invention, since ions are implanted after the entire surface of the capacitor structure is covered with an insulator, the emission of secondary electrons from the capacitor structure is suppressed. As a result, accumulation of positive charges in the capacitor structure is suppressed, and electrostatic damage to the capacitor structure can be prevented.

[Brief explanation of drawings]

FIG. 1 is a diagram for explaining an embodiment of the ion implantation method according to the present invention, and FIG. 2 is a diagram for explaining a conventional ion implantation method. In the figure, 3 and 5 are polycrystalline silicon films, 4 is an insulating film, and 6 is a photoresist. Note that the same reference numerals in each figure indicate the same or corresponding parts.

Claims (1)

[Claims] (1) In an ion implantation method for implanting ions into a semiconductor device having a capacitor structure on a semiconductor substrate, after covering the entire surface of the capacitor structure with an insulator,
An ion implantation method characterized by ion implantation.