JPH0135459B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a liquid metal ion source for a field emission type ion beam generator used in an ion processing device, an ion implantation device, or the like.

Field emission type liquid metal ion sources have high brightness and can provide many ion species, so they are expected to be applied to maskless ion implantation devices using finely focused ion beams.

Ion implantation is performed in - group compound semiconductor substrate crystals such as gallium arsenide (GaAs) to form optical devices such as lasers, light emitting diodes, and photodetectors, bipolar transistors, and field effect transistors. Typical examples include Be for p-type and Si for n-type, and are actively applied in conventional ion implantation techniques, showing good activation rates.

On the other hand, when these ion species are used in a liquid metal ion source, they are generally used in the form of a eutectic alloy with Au to lower the melting point, since both Be and Si have high melting points and high vapor pressures. Maskless ion implantation has already been performed using these eutectic alloys, Au-Be, and Au-Si. However, when doping p-type and n-type impurities at arbitrary positions in the same semiconductor substrate crystal using a maskless ion implantation device in the form of a focused ion beam, single ion implantation is required due to the complexity of ion source exchange. It is desirable that both p-type and n-type ions be emitted from the source. If such an alloy containing both types of ions is realized, a single ion acceleration, focusing, and deflection column with an ion mass separator can be used to produce an ion beam containing both p-type and n-type impurities. Ion species serving as n-type and p-type impurities can be optionally selectively implanted into desired positions of the substrate crystal simply by controlling the mass separator.

As an extension of the conventional Au-Be and Au-Si eutectic alloy type ion sources, the applicant filed a patent application for a ternary alloy composition Au-Si-Be containing both ions.
Although disclosed in No. 105398, the present invention relates to a method for manufacturing the above-mentioned ternary alloy, and the present invention relates to a method for manufacturing the above-mentioned ternary alloy, and the present invention relates to a method for manufacturing the above-mentioned ternary alloy.
The purpose is to provide a method for manufacturing Si-Be.

The melting point of the alloy used as a liquid metal ion source is around 700℃, considering that it is difficult to use in a vacuum because the vapor pressure increases at high temperatures, and that Be easily reacts with the tungsten used as the emitter electrode. is preferably lower than that.

As already mentioned, Au and Si are known to form a eutectic alloy, and as shown in Figure 1A,
When the weight ratio of Au and Si is about 94:6, the alloy has the lowest melting point of about 370°C, and when Si is in the range of 5 to 8% by weight, the melting point is 600°C or lower, forming a eutectic alloy. On the other hand, Au and Be are 97:3 to 97:3 as shown in Figure 1B.
An alloy with a weight ratio of 99:1 forms a eutectic alloy with a melting point of about 600℃, and the melting point of the alloy when the weight ratio is 97:3 is
The temperature is 600°C or less, and both can be suitably used as liquid metal ion sources. But Si and Be
As shown in Figure 1C, does not react up to about 1100°C, but forms a eutectic alloy at a weight ratio of about 60:40. However, the melting point at this time is approximately 1100°C, which cannot be used as a liquid metal ion source, but the melting point is lower than the melting point of each individual substance.

From the above facts, adding Be to a low melting point eutectic alloy of Au-Si increases the melting point, but Be
It is predicted that a Si-Be-Au alloy with a melting point of about 700°C or less will be created if the amount of addition is in a certain ratio.
As a result of further investigation and experiments, we found that the weight ratio was 94:6.
The Si-Be-Au ternary alloy created by adding Be in the weight range of 0.4 to 1.0 to 100% of the Au-Si alloy has a melting point of
It was found that the temperature was about 700℃ or lower.

As shown in FIG. 1A, the addition ratio of the basic Au--Si alloy may be a weight ratio of around 94:6, which forms a low melting point eutectic alloy, and the lower the melting point of the alloy, the more preferable it is. The amount of Be added to the above Au-Si alloy is
100: If it is a ternary alloy with a weight range of 0.4 to 1.0 and the amount of Be added is about 1 g to 100 g of Au-Si alloy, its melting point will be about 600 to 700 °C, If the amount added exceeds the above range, the melting point will rise.

To explain the actual method of manufacturing the above-mentioned ternary alloy, first, a low melting point Au-Si alloy is created, this alloy is kept in a molten state, a predetermined amount of Be is added, and the alloy is melted and stirred to form a homogeneous material. It is a ternary alloy. By forming the Au-Si alloy into a ternary alloy in this manner, the addition ratio of the composition can be easily adjusted, and a ternary alloy with good uniformity can be obtained.

The Au-Si-Be alloy thus obtained can be used in the same way as a conventional liquid metal ion source. That is, as shown in FIG.
The above metal ion source 3 is placed in a reservoir provided near the tip of the emitter electrode 1 with a diameter of about 1 μm.
Load the Au-Si-Be alloy, place the ion extraction electrode 4 in front of the tip of the emitter electrode, raise the temperature of the emitter electrode 1 to melt the ternary alloy, and melt up to the radiation part 2 at the tip of the emitter electrode. When a voltage of several kilovolts is applied between the emitter electrode 1 and the ion extraction electrode 4 while the alloy 6 is coated with the alloy 6, an ion beam containing a mixture of three elements is produced from the electrode emitting part through mechanisms such as field evaporation and field ionization. 5 will be released and a mass separator (not shown)
Only necessary ions are selectively separated and implanted into the substrate crystal.

As described above, according to the present invention, the melting point is 700°C.
It is possible to easily produce a Au-Si-Be ternary alloy of a certain degree or less, and the Au-Si-Be ternary alloy can be practically used as a liquid metal ion source. The ion source can generate p-type impurity ions and n-type impurity ions,
There is no need to replace the ion source during the ion implantation process, and highly integrated electronic devices and optical devices can be easily formed on the same substrate crystal.

Next, embodiments of this invention will be described.

Example 100 g of Au-Si alloy was obtained by adding 6 g of Si to 94 g of Au and heating at 400°C. this
Au-Si alloy was heated at 800℃ and Be
0.5g was added and mixed uniformly to form an Au-Si-Be ternary alloy. The melting point of this alloy was 620°C.

This ternary alloy was used as a liquid metal ion source in an ion beam generator, and the mass spectrum of the emitted ions was measured, and the results were as shown in FIG. It can be seen from FIG. 3 that a considerable amount of monovalent and divalent ions of Be and Si are released. These spectral shapes remained stable even after 50 hours of emission, indicating that this ternary alloy could be used practically as a liquid metal ion source.

[Brief explanation of drawings]

Figure 1A is a graph showing the relationship between composition ratio and melting point of Au-Si alloy, Figure 1B is a graph showing the relationship between composition ratio and melting point of Au-Be alloy, and Figure 1C is a graph showing the relationship between composition ratio and melting point of Au-Si alloy.
A graph showing the relationship between alloy composition ratio and melting point. Figure 2 is a schematic cross-sectional view of the main parts of the ion beam generator. Figure 3 is a graph showing the relationship between alloy composition ratio and melting point.
The figure is a mass spectrum diagram of ions emitted from a Si-Be-Au alloy liquid metal ion source. 1... Emitter electrode, 3... Liquid metal ion source, 4... Ion extraction electrode, 5... Ion beam.

Claims (1)

[Claims] 1 Au-Si alloy 100 in a molten state with a weight ratio of 94:6
1. A method for manufacturing a Si-Be-Au ternary alloy liquid metal ion source for a field emission type ion beam generator, which comprises adding Be in a weight range of 0.4 to 1.0 to homogeneously dissolving the Si-Be-Au ternary alloy liquid metal ion source.