JPH0414456B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a field emission type liquid metal ion source used in ion processing equipment, ion implantation equipment, etc.
More specifically, the present invention relates to alloy metal ion seed materials for liquid metal ion sources.

When forming optical devices such as lasers, light emitting diodes, and photodetectors, and electronic devices such as various transistors and diodes on semiconductor substrate crystals such as gallium arsenide, it is necessary to implant p-type, n-type, or both impurity ions. As a matter of course, in the ion implantation process, complicated operations such as replacing the ion source of the ion implanter and creating a resist mask are repeatedly performed. On the other hand, in the recently proposed maskless ion implantation method using an ion beam focused on the order of submicrons, it is considered possible to eliminate changes in hardware and control the process entirely by software. However, even in this maskless ion implantation method,
When performing a second ion implantation on top of an area that has already been implanted, replacing the ion source requires strict alignment between the ion generator, ion beam focusing system, and ion deflection electrode system, which can be very difficult. It will take time.

Therefore, if impurity ions for p-type, n-type, and isolation can be selectively generated from a single ion generation unit without replacing the ion source, hardware changes can be made during most integrated circuit device fabrication processes. , it becomes possible to easily manufacture highly reliable opto-electronic devices that are highly integrated on the same substrate using only software control without making any adjustments.

Until now, p-type ion species have been used for ion implantation into − group compound semiconductor substrate crystals.
It is known that si is a typical Be and n type, and these ion species are used in ion implantation and have shown good activation rates.

However, when Be and Si are used as alloy metal ion seed materials in a liquid metal ion source, both have high melting points and high vapor pressures, so it is necessary to lower the melting point.
It is generally used in the form of a eutectic alloy with Au.
Maskless ion implantation has already been performed using these eutectic alloys, Au-Be and Au-Si. Furthermore, the present applicant has proposed that as an extension of this Au-Be and Au-Si eutectic alloy type ion seed material, it contains both ions.
proposed a ternary alloy of Au-Si-Be (patent application 1983-
No. 105398 (Special Publication No. 59-48795)).

However, with further technological advances, not only p-type and n-type impurity elements but also B
There has been an increasing demand for alloy metal ion seed materials containing impurity elements for isolation. In response to this request, the applicant
proposed a quaternary alloy consisting of -Si-Be-B (Japanese Patent Application No. 59-4752 (Japanese Unexamined Patent Publication No. 60-150534)).

FIG. 1 shows an example of a schematic structure of a field emission type liquid metal ion source, in which an emitter electrode 1 is supported at the tip of an electrode base 2, and a body of the emitter electrode 1 has a ring-shaped member 3 projecting from the electrode base 2. The annular space formed by both is a reservoir.
Therefore, the above-mentioned alloy metal ion seed material 4 is loaded.

The emitter electrode 1 is heated to a predetermined temperature via the electrode base 2, and when the ion type 4 reaches the melting temperature, it flows through the body of the electrode 4 toward the tip, and the electrode 4 is made of molten alloy metal. It is now covered with the ionic seed material. When this state is reached, applying a voltage of several kV to the emitter electrode 1 and the ion extraction electrode 5 placed in front of it will cause field evaporation.
An ion beam 6 is emitted from the tip of the emitter electrode 1 due to electric field ionization or the like. When the ion seed material 4 and the emitter electrode 1 are well wetted, the molten ion seed material flows smoothly to the tip of the electrode as the ion beam is emitted, and the ion beam emission continues stably. will be carried out.

The emitter electrode 1 of this liquid metal ion source is usually made of tungsten, and is made of the above-mentioned Pd-Si.
When a -Be-B quaternary alloy is used as an ion seed material, the wetting with the emitter electrode is not very good, so ion beam emission is sometimes intermittent, and stable ion beam emission cannot be obtained continuously. Ta. This is a fatal drawback in maskless ion implantation in which ions are implanted under precise control using a finely focused ion beam.

In view of the above, this invention has been made through intensive research to develop an alloy metal ion seed material for a liquid metal ion source that contains p-type, n-type and isolation impurity elements and has excellent wettability with a tungsten emitter electrode. As a result, wetting with tungsten was improved by adding Ni as a base metal to the Pd used as the base metal in the previously proposed quaternary alloy consisting of Pd-Si-Be-B to form a quinary alloy. discovered that stable ion beam emission could be achieved continuously and completed this invention.

Hereinafter, this invention will be explained based on FIG. 2.
Figure 2a is a graph showing the relationship between the composition ratio and melting point of a Pd-Be alloy.When Pd and Be are used alone, the melting point is around 1500℃, but in an alloy containing about 2% by weight of Be, the melting point is around 1500℃. Its melting point drops to about 930°C. on the other hand,
In the case of Pd-Si alloy, as shown in Figure 2b, Si
The alloy in which 4 to 5% by weight of Pd is added has a melting point of 800
The temperature drops to close to ℃. Further, in the case of a Be-Si alloy, as shown in FIG. 2c, the melting point of the alloy becomes 1000 DEG C. or less when Si is contained in an amount of about 60% by weight. Further, the melting point of B alone is 1500°C or higher, but the melting point of a Pd-B alloy containing about 3.5% by weight of B is 850°C or lower, as shown in Figure 2d. Further, in the case of a B--Ni alloy, the melting point of an alloy containing about 13% by weight of B is about 1000 DEG C., as shown in FIG. 2e.

Based on the above facts, as a result of repeated studies and experiments,
An alloy in which Ni is added to Pd as the base metal and the composition ratio is in the range of 70 to 80:20 to 30% by weight has good wettability with tungsten. In addition, the base metal with the above composition ratio and Si, which becomes an n-type impurity element of the − group compound semiconductor, and Si, which becomes a p-type impurity element.
Be, B becomes an impurity element for isolation
The total impurity is 93.0~96.5: 3.5~7.0% by weight
The melting point of a quinary alloy composed of proportions in the range of 900
When melted, it exhibits good wetting with tungsten at temperatures below 0.degree. C., and can be suitably used as an alloy metal ion seed material for field emission type liquid metal ion sources.

Addition ratio of the above three types of Si-Be-B impurity elements
Details of 3.5-7.0 wt% are Si 1.5-2.5 wt%, Be
is 0.5 to 2.0% by weight, and B is 1.5 to 2.5% by weight.

When the addition ratio of impurity elements to the base metals Pd and Ni is within the above range, the melting point of the obtained alloy is
It will be within the range of about 800 to 900°C, but if the addition ratio exceeds the above range, especially if the amount of B added is large,
The melting point rises rapidly, and when it exceeds 1000°C, it becomes unsuitable as an alloy metal ion seed material.

Next, an example of the manufacturing method of this five-element alloy is as follows.
A predetermined amount of weighed five elements is placed in a vacuum container, then Ar gas is introduced and heated at approximately 1500℃ in an Ar gas atmosphere to melt it. Once each element is evenly dispersed, heating is stopped. By doing so, a five-element alloy suitable for use as an alloy metal ion seed material can be obtained.

As mentioned above, although the cause has not yet been elucidated, by composing the alloy metal ion seed material using a binary alloy of Pd and Ni as the base metal, wetting of tungsten, which is used as the emitter electrode of the liquid metal ion source, is reduced. As the ion beam has been improved and stable ion beam emission can be performed continuously, it can be used for maskless ion implantation using a focused ion beam on the order of submicrons, which has recently been proposed, and can be used for highly integrated electron beams. Devices and optical devices can be formed efficiently.

Next, the present invention will be explained with reference to examples. Pd7.45
Weigh 2.1 g of Ni, 0.18 g of Si, 0.07 g of Be, and 0.19 g of B, put them into a BN crucible, create a vacuum, introduce Ar gas, and heat the crucible at a temperature of about 1600°C in an Ar gas atmosphere. and melted to obtain a five-element alloy. The melting point of this alloy was approximately 800°C.

This alloy is loaded as an ion seed material into the reservoir of the emitter electrode of a liquid metal ion source, and by applying 6kV to the emitter electrode and extraction electrode, an ion beam is emitted from the electrode tip, and this ion beam emission continues for 10 minutes. However, there was no visible interruption and it was extremely stable.

By controlling the mass separator, this emitted mixed ion beam could be selectively separated into only the ion beam of the desired ion species and guided to the semiconductor substrate.

[Brief explanation of drawings]

Figure 1 is a schematic diagram of the field emission type liquid metal ion source, and Figures 2 a to e are Pd-Be and Pd-
It is a graph showing the relationship between composition ratio and melting point of Si, Be-Si, Pd-B, and Ni-B alloys. 1... Emitter electrode, 2... Electrode base, 4...
Alloy metal ion seed material, 5... ion extraction electrode.

Claims (1)

[Scope of Claims] 1. A field emission liquid metal ion source comprising an emitter electrode, an alloy metal ion seed material loaded into a reservoir of the emitter electrode, and an ion extraction electrode provided in front of the emitter electrode, comprising: The alloy metal ion seed material contains a base metal, an n-type impurity element, a p-type impurity element, and an isolation impurity element, and the base metal has Pd and Ni in a ratio of 70 to 80:
A field emission type liquid metal ion source characterized by comprising a proportion of 20 to 30% by weight. 2 The total of the base metal and three impurity elements is 93~
97: 3 to 7% by weight of the liquid metal ion source according to claim 1. 3 The n-type impurity element is Si, the p-type impurity element is Be,
The liquid metal ion source according to claim 1, wherein the impurity element for isolation is B. 4 Si: 1.5 to 2.5% by weight, Be: 0.5 to 2.0% by weight,
A liquid metal ion source according to any one of claims 1 to 3, wherein B is in the range of 1.5 to 2.5% by weight.