JPS63304563A - Ion implantation - Google Patents

Abstract

PURPOSE:To eliminate charging and have precision injecting in an injection device, consisting of an ion source, a magnet for separation of ion beam mass, and a treatment chamber for ion injection into a base, by furnishing an ion neutralizing means between the magnet and treatment chamber, and by controlling the ion amount upstream the magnet. CONSTITUTION:Ion beams 2 from an ion source 1 are selected by the use of a separator magnet 3, to provide selected ions 4, which are separated perfectly by a separating slit 5 installed at the convergent point, followed by passage through a neutralizing means 16 which supplies secondary electrons, and it is injected in the form of an ion beam 6 to a plurality of wafers 7 affixed to a disc 8 to be rotated by a motor 9. An injection control device 15 is connected with the ion source 1 through a power supply 13, and an ion motor electrode 17 is furnished between the ion source 1 and magnet 3. The monitor current 13 therefrom is put into this device 15 through a current sensing part 19, and the magnet 3 is also connected with the device 15 through a magnetic field power supply 14. Thus the injection current 11 to the wafer 7 is controlled by the device 15, and a scanning control part 10 is also controlled.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an ion implantation device used for implanting impurities in the manufacturing process of semiconductor devices such as LSIs and for modifying the surface of metals and ceramics, and particularly relates to an ion implantation device used for improving the surface of metals and ceramics. The present invention relates to an ion implantation apparatus suitable for accurately controlling the implantation amount even with respect to charging phenomena of the base material to be implanted.

[Conventional technology]

In the conventional apparatus, as described in Japanese Patent Application Laid-Open No. 61-39356, a detector is installed at a position of the ion beam before or after the separating magnet, which is different from the implanted ion beam. This detector accurately detects the ion current proportional to the amount of ion implantation.

[Problem that the invention seeks to solve]

The above-mentioned conventional techniques are mainly aimed at controlling the amount of ion implantation, and no consideration is given to reducing the charging phenomenon of the base material, resulting in the problem of deterioration of the base material due to charging.

Here, an example of injection into a semiconductor device will be explained.

In the ion implantation process accompanying the recent miniaturization of LSI, etc., the insulating layer on the wafer surface has become thinner and finer, and wafers with photoresist have become more diverse, so the charge of the ions implanted into the wafer is constantly stored in the B layer. , leading to dielectric breakdown of the device, deterioration of performance, and impairing the uniformity and reproducibility of the implanted amount.
This has an adverse effect on the quality of the element.

In contrast, for example, rMethod of Irra
diatingDielectriccoatedS
em1conductor Bodies WithL
ow Energy Electrons, U, S
, P. 3507705J and [Method and apparatus for strengthening the neutralization of positively charged ion beams, Japanese Patent Publication No. 5
Publication No. 7-87056 J and the like provide an electron supply device as a means for preventing charging of the wafer surface. However, this method has problems due to electron leakage, instability of secondary electrons, etc.
It is nearly impossible to accurately detect the amount of ions implanted into a wafer.

SUMMARY OF THE INVENTION An object of the present invention is to provide an ion implantation apparatus that can reduce charging phenomena and at the same time accurately control the implantation amount.

[Means for solving problems]

The above object is to provide a means for neutralizing ions of an ion beam, and a detector for detecting another ion beam that does not pass through the neutralizing means and is proportional to the implanted ion beam,
This is achieved by independently controlling charging phenomenon mitigation and injection amount detection.

That is, the ion implantation apparatus according to the first invention of the present application is an ion implantation device that includes an ion source that generates ions, a separation magnet that separates the ion beam by mass, and a processing chamber that implants specific mass-separated ions into a base material. In the apparatus, a means for neutralizing ions is provided between the separation magnet and the processing chamber, and
A portion of the periphery of the ion beam on the upstream side of the separation magnet is detected, and the amount of ions injected into the base material is controlled based on this detected value.

Further, an ion implantation apparatus according to a second invention is an ion implantation apparatus comprising an ion source that generates ions, a separation magnet that separates the ion beam by mass, and a processing chamber that implants specific mass-separated ions into a base material. In addition, a means for neutralizing ions is provided between the separation magnet and the processing chamber, and the mass is removed by the separation magnet.

Of the ion beams that have been mass-separated according to the charge ratio, the amount of ions implanted into the base material can be determined by detecting the ion beam that is of a different ion type from the implanted ion beam and is proportional to the implanted ion beam. It is something to control.

[Effect]

As an ion beam neutralization method often used in ion implantation equipment, Holmes (A. J., Holmes: Ra
d.

Eff, 44.47 (1979)) states: (1) Electrons are supplied from outside the ion beam.

(2) Supplying electrons from the emitter in the ion beam.

(3) Supply electrons from the plasma bridge.

(4) Secondary electrons are supplied by ionizing the residual gas at a low vacuum of 10-3 to 10-'Torr.

etc., and (1) and (4) are often used.

The negative electrons thus supplied are trapped in the positive ion beam and neutralize the ion beam. When the positive ion beam reaches the insulating layer on the surface of the substrate to be implanted and positive charges are accumulated, negative electrons are carried to the substrate surface and neutralize the positively charged charges on the substrate surface. do. In this way,
Although the charging phenomenon can be alleviated, the highly accurate electrical controllability of the implantation amount, which is a feature of the ion implanter, is impaired.

The substance injected into the base material may be ions or neutral particles, but it is the amount of ions that can be measured and limited as the amount of current. However, when ions or neutral particles are incident, secondary electrons are generated. Also, the neutralization rate of secondary electrons and ions generated by collision with residual gas or gas generated from the base material, the neutralization rate due to neutralization means, the leakage of secondary electrons from the measurement system, and the rate of neutralization of secondary electrons and ions generated by collision with residual gas or gas generated from the base material. Errors in measurement of ion amount, such as charge rate, have large fluctuation factors.

For example, the uniformity of the implantation amount for semiconductor devices must be maintained within 1 to 2%, and although this is possible with ion implanters, wafers with insulating films or photoresists may be damaged due to charging phenomena, outgas, etc. For the above reasons, it is difficult to accurately measure the amount of electricity flowing in and out.

In the present invention, the charge on the base material (wafer, etc.) is alleviated by neutralizing means, and the amount of electricity is separated from the base material (wafer, etc.) by using an ion beam that is proportional to the implantation amount. The electrical quantity is accurately measured using a partial ion monitor electrode with a Faraday cage structure (with a suppressor electrode to suppress secondary electrons) made of a heat-resistant material (heat-resistant material).

As a result, the electrical charge on the base material (wafer, etc.) is neutralized by supplying electrons, and the amount of ion implantation can be accurately measured using another ion beam proportional to the implanted ion beam. Destruction can be prevented, and the injection amount can be controlled uniformly and with good reproducibility.

〔Example〕

Hereinafter, an embodiment of the present invention (first invention) will be described with reference to FIG. There are two types of ion implantation devices: those with an ion current of μA class and those with an ion current of mA class. In terms of charging phenomena, uniformity of injection amount, reproducibility, temperature rise of the base material (wafer), etc., what is involved in the present invention is a so-called mA class high current machine, and for convenience of explanation, it is Here, a high current ion implantation apparatus for manufacturing semiconductor devices will be explained as an example. However, it goes without saying that the same concept as described below can be applied to other types of devices or surface modification devices in principle.

A gas of the substance to be ionized is generally introduced into the ion source 1 . Plasma is generated by superimposing a thermoelectron or microwave electric field and a magnetic field.

The ion source 1 is normally at a high potential of 10 to 20 kV, and is emitted as a total ion beam 2 with a large current by an electric field. The ion beam 2 incident on the separation magnet 3 is subjected to ion acceleration voltage and the strength of the magnetic field produced by the separation magnet 3, so that ion species flying in a fixed orbit are selected according to the mass-to-charge ratio of the ions. This is similar to the principle of mass spectrometry. The thus mass-separated sorting ion beam 4 is completely sorted and separated by the separation slit 5 installed at the convergence point, and reaches the wafer 7 as an implanted ion beam 6. mA
In order to prevent the temperature of the wafers 7 from increasing due to high-power ion implantation, the wafers 7 are arranged around a circular plate 8 and rotated at high speed in a high-current ion implantation apparatus such as the above. In order to uniformly implant ions over the entire surface of the unihaf, the disk 8 is rotated at a constant high speed, and the disk 8 is scanned in a transverse direction with respect to the implantation ion beam 6, or the implantation ion beam 6 is scanned in the same direction. ing. This embodiment is a case of a configuration in which the disk 8 is scanned, and there is a scanning mechanism 9 and a scan control section 10, and the disk 8 is
Considering that the rotation speed on the outer circumference side is faster than the inner circumference side, the rotation speed is inversely proportional to the radial direction. An example of uniform injection using scan control was shown. Ion source power supply 13. The entire system is controlled by a magnetic field power source 14 and an injection control device 15 that performs centralized control using a CPU. The system including the ion beam line, wafer 7, and disk 8 is maintained at a high vacuum by an exhaust system.

If there is an insulating layer on the surface of the wafer 7, the implanted ion beam 6
remains in the insulating layer without losing charge and is therefore not detected as the implanted ion current 11 flowing through the wafer 7 and disk 8 as a charge.

Since positive ions that can be stably obtained in large quantities are usually used, the insulating layer becomes positively charged, eventually destroying the insulating layer. Furthermore, the convergence of the implanted ion beam 6 is also disturbed, which adversely affects uniform ion implantation.

Therefore, in order to cancel this positive charge, a neutralizing means 16 for supplying electrons from the filament or a gas reaction chamber is provided in front of the wafer 7 and after the separating magnet 3. Install. Electrons from the neutralizing means] 6 are supplied to the positively charged wafer 7 to cancel the accumulation of positive charges, or the implanted ion beam 6 itself is neutralized to prevent charging. However, simply providing this neutralizing means 16 is not sufficient to realize injection with good uniformity and reproducibility. That is, (1) the neutralization rate of the implanted ion beam 6 itself changes depending on the gas pressure (degree of vacuum). (2
) The amount of secondary electrons generated varies depending on gas pressure, accelerating voltage (energy), beam convergence, degree of impact with walls, wafers, disks, etc., dirt, etc.

(3) Existing secondary electrons leak from the measurement system.

Due to the above reasons, problems arise such that the amount of charge detected as the implanted ion current 11 does not match the amount of the implanted substance or varies.

The present invention focuses on this point, and the electrification of the wafer 7 is reduced by the neutralizing means 1.
6, the ion implantation amount is controlled by detecting an ion current proportional to the implanted ion beam 6 and unrelated to the neutralizing means 16, without using the implanted ion beam 6 and the implanted ion current 11, which have many errors and fluctuations. This is what we do.

The entire ion beam 2 emitted from the ion source 1 generally advances to the separation magnet 3 while being slightly divergent. Since this total ion beam 2 has a high density at the center, an aperture is provided at the center of the beam to allow more than 90% of the beam to pass through, and a partial ion monitor electrode 17 is installed to detect a part of the circumference. The monitor current 18 is converted into a partial ion monitor current detector 19.
to measure accurately. Of course, the partial ion monitor current 18 is
Since it is proportional to the implanted ion beam 6 and the implanted ion current 11, the proportional constant must be actually measured and calibrated in advance, or stored in the memory of the CPU of the implant control device 15.
It is used to control the amount of ion implantation, if necessary. It goes without saying that the shape of the partial ion monitor electrode 17 does not necessarily have to have an opening, and may have a structure in which a simple flat plate electrode is inserted into a small portion of the entire ion beam 2. Furthermore, it is even more convenient to have a variable structure that allows the relative position with respect to the beam to be changed.

Next, an embodiment of the second invention will be described based on FIGS. 2 and 3. It is premised on the fact that many ion species are generated when the gas normally used for implantation is ionized.

FIG. 2 shows a mass spectrum of ionized boron difluoride (BF3) gas. The number on the upper left of the letter indicating the element indicates the mass number, and in the case of boron (B), the mass number is 10.
and 11, and 11B is often used for implanting ' into semiconductor devices. In FIG. 3, by keeping the ion acceleration voltage constant and changing the magnetic field strength of the separation magnet 3,
The ion species that converge on the slit 5 are selected, and a mass spectrum as shown in FIG. 2 is obtained. If 11B (mass number 11) is selected as the implantation ion beam 4, a heavier ion beam, such as 11 B 19 F 2 (mass number 49)
is not bent that much and enters the heavy ion detection electrode 25 as a heavy ion beam 24, and the ion current is accurately detected as a heavy ion beam current 26 by the heavy ion detection section 27. In addition, since 10B (mass number 10) as an isotope is light, it bends greatly and enters the light ion detection electrode 21 as a light ion beam 20, and the light ion detector 23 accurately detects the ion current as a light ion beam current 22. is detected.

For detection of ion current, partial ion monitor electrode 17
Generally, it is difficult to apply a secondary electron prevention voltage to the monitor electrode 17 because it disturbs the trajectory of the ion beam itself, but as in the present invention, the heavy and light ion detection electrode 25 In the case of .21, a so-called Faraday cup structure can be adopted in which a secondary electron prevention voltage can be applied with an arrangement that allows measurement of all incident ions 24.20, and the measurement accuracy of the ion current is high. Also, these ion beams 24°20 are proportional to the implanted ion beam 6, but if an isotope ion beam is used, the isotope ratio is constant, so it can be detected as an ion current that is more proportional to the implanted ion beam 6. , it becomes possible to control the ion implantation amount more accurately.

In any of the inventions described above, it is of course possible to measure and calibrate the proportionality constant with respect to the implanted ion beam 6 in advance, store these in a storage device, and automatically set and control by the CPU.

Note that the heavy ion beam detection electrode 25. The position of the light ion beam detector 21 changes depending on the ion type to be detected, so it is convenient to have a variable position mechanism that allows the light ion beam detector 21 to adjust its position to the optimum position. Of course, it is technically possible to set it to .

Furthermore, instead of the wafer 7 and disk 8 in FIGS. 1 and 3, metals and ceramics are used as other base materials.

When placing a plastic etc. and forming a thin film on the surface for the purpose of surface modification etc., at the same time as the implanted ion beam 6,
It is also possible to form a thin film by injecting ions or neutral particles from another ion source, vapor deposition device, or sputtering device and co-implanting the ions and neutral particles into the substrate. The detection and injection amount control of the implanted ion beam 6 tends to be inaccurate due to other ion species, electrons, etc. However, according to the present invention, the amount of implanted ions can be accurately detected and controlled, and a high-quality thin film can be formed. Become.

(Effects of the Invention) According to the present invention, by neutralizing the charge on the base material (wafer, etc.) to be implanted and by individually detecting and controlling the amount of ions to be implanted, it is possible to eliminate the charge and at the same time accurately control the amount of ions to be implanted. Since it can be controlled, dielectric breakdown of the base material can be prevented and uniform ion implantation with good reproducibility can be performed, which has the effect of improving the quality and yield of implanted products (semiconductor devices, etc.).

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the first invention, FIG. 2 is a diagram showing a mass spectrum of boron trifluoride, and FIG. 3 is a block diagram showing an embodiment of the second invention. DESCRIPTION OF SYMBOLS 1... Ion source, 2... Total ion beam, 3... Separating magnet, 4... Selecting ion beam, 5... Separating slit, 6... Implanting ion beam, 7-... Wafer, 8
. . . Disk, 9 . . . Scanning mechanism, 10 . . . Scanning control unit, 11 . Magnetic field power supply, 15... Injection control device, 16... Neutralization means, 17.
- Partial ion monitor electrode, 18... Partial ion monitor current, 19... Partial ion monitor current detection section, 20...
-Light ion beam, 21.-Light ion detection electrode, 22.
・・Light ion current, 23・−・Light ion detection section, 24・
・Heavy ion beam, 25...Heavy ion detection electrode, 26
...Heavy ion current, 27...East ion detection section.

Claims (1)

[Claims] 1. An ion implantation device comprising an ion source that generates ions, a separation magnet that mass-separates the ion beam, and a processing chamber that implants mass-separated specific ions into a base material,
A means for neutralizing ions is provided between the separation magnet and the processing chamber, and a portion of the periphery of the ion beam upstream of the separation magnet is detected, and the amount of ions implanted into the base material is controlled based on this detected value. An ion implantation device characterized by: 2. In the statement of claim 1, ion implantation in which another ion source, an electron beam evaporation device, or a sputter evaporation device is provided in the processing chamber, and other ions are co-injected with the mass-separated ion beam. Device. 3. In the statement of claim 1 or 2,
The proportionality constant between the implanted ion beam amount and another detected ion beam amount that is proportional to the implanted ion beam amount is measured in advance and stored in the computer memory, and the implanted ion beam amount is compared to the detected ion beam amount. Ion implantation equipment automatically controlled by 4. In an ion implantation device consisting of an ion source that generates ions, a separation magnet that mass-separates the ion beam, and a processing chamber that implants mass-separated specific ions into a base material,
A means for neutralizing ions is provided between the separation magnet and the processing chamber, and a means for neutralizing ions is provided between the separation magnet and the processing chamber. An ion implantation apparatus characterized in that the amount of ions implanted into a base material is controlled by detecting an ion beam proportional to the implanted ion beam. 5. The ion implantation apparatus according to claim 4, wherein the ion beam to be detected is an isotope of the implanted ion beam. 6. In the statement of claim 4 or 5,
An ion implantation device that includes other ion sources, an electron beam evaporation device, and a sputter evaporation device in a processing chamber, and co-injects other ions with a mass-separated ion beam. 7. In the statement of claim 4, 5, or 6, the proportionality constant between the implanted ion beam amount and another detected ion beam amount that is proportional to the implanted ion beam amount is measured in advance. , an ion implanter that stores information in a computer's memory and automatically controls the amount of implanted ion beams based on the amount of detected ion beams.