JPS5985858A - Ion implantation device - Google Patents

Abstract

PURPOSE:To prevent insulation breakdown in ion implantation to a silicon wafer by irradiating UV light having a wavelength of specific angstrom or below to the SiO2 constituting a gate insulation film. CONSTITUTION:An ion is implanted to a silicon wafer 11 produced by providing a gate insulation film consisting of SiO2 on the surface and providing a gate electrode on the gate insulation film thereby forming a source region and drain region. An opening 21 is provided to a process chamber in the end station part of the device and an UV generator 22 is provided on the outside thereof. UV light having a wavelength of <=1,400 angstrom is applied through the opening 21 to the silicon wafer 11 while the ion is implanted.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a manufacturing process of a semiconductor device, and relates to a manufacturing process of a semiconductor device. MO to
Regarding ion implantation equipment for forming source and drain regions of FET (field effect transistor) in 8 integrated circuits [Technical background of the invention] In recent years, in the manufacture of MO8 integrated circuit devices, donor or acceptor Ion implantation is widely used to implant impurities into semiconductor wafers.

FIG. 1 is a diagram illustrating ion implantation Y into a semiconductor wafer. A field insulating film 2 and a gate insulating film 3 are provided on a silicon wafer 1, and a conductive gate pentode 4 is provided on the gate insulating film 3. Here, the field insulating film 2 and the gate insulating film 3 are It could be made of silicon dioxide. Then, an ion beam 6 is irradiated f7-+ to form a source region and a drain region 5 on the silicon wafer 1. At that time, the ion beam 6 is applied to the gate electrode 4
Since the gate electrode 4 is also irradiated with ions, the gate electrode 4 is given an ion charge. accumulate.

In the past, the beam current for this ion implantation was about a few μA, but due to factors such as shortening the time of the 2nd I detection process, the beam current has gradually become larger and has recently ranged from several mA to several tens of mA. It has become.

For this reason, the amount of charge accumulated in the gate electrode during the manufacturing process increases significantly. Further, as integrated circuit devices become more highly integrated, the voltage resistance of gate insulating films tends to become thinner.

Increasing the beam current and making the gate insulating film thinner increases the risk of dielectric breakdown of the gate insulating film. because,
This is because an increase in the beam current results in an increase in the charge stored in the gate electrode, and a thinner two-gate insulating film results in a decrease in dielectric breakdown voltage.

For example, assuming that the thickness of the gate insulation (jα) is 740 OA and the breakdown electric field is 10'v/cm, dielectric breakdown will occur if there are 2X10 positive charges/cIIL- in the gate electrode.

In order to prevent such dielectric breakdown of the gate insulating film,
Conventionally, a method of irradiating a silicon wafer with negative electrons has been used. The ions implanted into the silicon wafer 11 are generated by the ion generator 12 and sent to the ion beam 13.
Be ejected as. The ion beam 13 is applied to the silicon wafer 11 provided on the disk 15 via an analyzing magnet 14%'. A rotary motor 16 is provided on the disk 15, and a Faraday cage 17 and an electron gun 18 are provided on the end station. This is an enlarged view of the part, and the same elements as in Fig. 2 are indicated by the same symbols. The electron beam emitted from the first electron beam 18 hits the Faraday cage 171C, where it generates secondary electrons 19. -AIS of secondary electrons is applied to the silicon wafer 11 on the disk 15 to neutralize the positive charge on the gate electrode. 'f nawachi 4 ion beam 13
The positive charges accumulated on the gate electrode are neutralized by secondary electrons from the Farah day cage 17. In this way, dielectric breakdown in the gate insulating film can be prevented.

[Problems with background technology]

As mentioned above, the conventional device prevents dielectric breakdown of the gate insulating film by neutralizing the positive charge of the gate electrode with the negative charge of the secondary electrons, and the pupil of ion implantation, that is, the beam current There are problems such as the need to change the supply threat of secondary electrons depending on the size.

[Purpose of the invention]

The present invention has been made in view of the above points, and is based on data on silicon wafers. It is an object of the present invention to provide an ion implantation device that does not prevent dielectric breakdown by neutralizing positive charges accumulated in a pole with negative electrons.

[Summary of the invention]

In order to achieve the above object, the present invention provides an ultraviolet irradiation device in a conventional device, thereby irradiating ultraviolet rays during ion implantation into a silicon wafer to increase the conductivity of silicon dioxide forming the gate insulating film. The present invention provides an ion implantation device that removes positive charges on a gate electrode.

[Embodiments of the invention]

An embodiment of the present invention will be described with reference to FIG. 4 and FIG. 5. FIG. 4 is a block diagram of an ion implantation apparatus according to one embodiment, and the same elements as in FIG. 2 are designated by the same reference numerals. Opening 21 in the process chamber of the end station part of the ion implanter #? Installed and an ultraviolet generator on the outside! 22
will be established. Then, the generated ultraviolet rays are applied to the silicon wafer 1 through the opening 21. Note that the inside of the process chamber is kept in a vacuum of about 1.times.16-5 Torr or less.

Figure 5 shows silicon (Si) and silicon dioxide (SiOx).
) As is clear from Figure 1 in the energy band diagram of the junction, the energy gap of 8101 is about 8.9 eV. In order to give 5ins ultraviolet light and photoconductivity, the wavelength of ultraviolet light:

It is required that λ=hxC 8°ri (1) or less. Here, a blank constant:
h = 6.624XIOJ-see Speed of light: c
= 3. OX10'm/sec electronic port: 1
Since eV = 1.602 XIOJ, %3i02
Assuming that the energy gap is 8.9 eV, the wavelength of ultraviolet light: λ is (6) # 1.394 Xl0-' = 1394 A (angstroms) from equation (1).

Waves Jk approx. 14 on the silicon wafer during ion implantation work
When irradiated with ultraviolet rays of 00A or less, the conductivity of 5i(h) forming the gate insulation II increases, and the charges accumulated in the gate electrode are transferred to the silicon wafer 11 through the S10! film.
It will flow to Note that during ion implantation, the disk 15 is rotated uniformly by the rotary motor 16.
Since the process chamber is arranged vertically, the silicon wafer 1 is uniformly implanted with ions and irradiated with ultraviolet rays. Further, the ultraviolet ray generator 22 may be constructed from a deuterium lamp, for example.

〔Effect of the invention〕

As described above, according to the present invention, during ion implantation into a silicon wafer, the electrical conductivity of the gate insulating film can be increased by irradiating ultraviolet rays with an energy of 8.9 eVl to 51 (h) forming the gate insulating film. Because it is possible,
It is possible to provide an ion implantation device that allows the positive charges accumulated by ion implantation to be absorbed by flowing them into the silicon wafer body. This can be realized by a relatively simple means of installation, and a great effect can be achieved, so it is economically more efficient than conventional devices.

[Brief explanation of drawings]

Fig. 1 is a diagram explaining ion implantation into a silicon wafer, Fig. 2 is a block diagram of an example of the configuration of a conventional device, and Fig. 3 is a diagram illustrating ion implantation into a silicon wafer.
4 is a block diagram of an embodiment of the present invention, and FIG. 5 is an energy band diagram of S ball and Sing. C1...Silicon wafer, 3...Gate Insulating film, 4
...day) K pole, 21...opening, 22...ultraviolet irradiation device. Applicant's agent Kiyoshi Inomata Figure 1 Figure 2 Figure 4

Claims (1)

[Claims] Ion implantation in which ions are implanted into a silicon wafer having a gate insulating film made of silicon dioxide on the surface and a gate electrode formed on the gate insulating film to form a source region and a drain region. In the device. An ion implantation apparatus characterized in that an ultraviolet irradiation device is provided for irradiating the gate insulating film with ultraviolet rays having a wavelength of 1400 angstroms or less during the ion implantation.