JPH0360140B2 - - Google Patents

Description

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

When forming optical devices such as lasers, light emitting diodes, and photodetectors, or electronic devices such as various transistors and diodes on semiconductor substrate crystals such as gallium arsenide, it is necessary to implant p-type and n-type impurity ions. Naturally, in the ion implantation process, complicated operations such as replacing the ion source of the ion implantation apparatus and aligning the 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 control the process entirely by software without making any changes to the hardware.

However, in any of the ion implantation methods, if the ion source is replaced during the process, it is necessary to align the axes between the ion generation section, the ion acceleration and focusing system, and the ion deflection electrode system with strict accuracy. Furthermore,
When implanting ions of a different conductivity type over a pattern that has already been implanted with sub-micron precision, if the position of the ion generating part shifts even slightly when replacing the ion source, it will take a lot of effort to adjust the position. I will take it.

Therefore, if p-type and n-type impurity ions can be selectively generated from one ion generation unit without replacing the ion source, it will be possible to generate most of the integrated circuit device without changing or adjusting the hardware during the manufacturing process. It becomes possible to easily manufacture highly reliable opto-electronic devices that are highly integrated on the same substrate using only software control.

Until now, p-type ion species have been used for crystal ion implantation of − group compound semiconductor substrates.
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 liquid metal ion sources, both have high melting points and high vapor pressures, so
It is generally used in the form of eutectic alloys with Au to lower the melting point, and these eutectic alloys, Au-
Maskless ion implantation has already been performed using Be and Au-Si. Furthermore, the present applicant claims that this Au-Be
and as an extension of the Au-Si eutectic alloy type ion source,
A ternary alloy of Au-Si-Be containing both ions was proposed in Japanese Patent Application No. 105398/1983.

However, Si and Be alone are not necessarily sufficient as ion sources for maskless ion implantation.
Depending on how technology develops in the future, it may become necessary to develop other ion species. Actually, Se is n-type,
Mg is an important p-type ion source, and Se in particular is an n-type ion source.
It is attracting attention as an ion species with extremely high activity rate.

An object of the present invention is to provide a liquid metal ion source for a field emission type ion beam generator using Tl, which has a low melting point of around 200° C. or lower and is inexpensive, as a base metal.

That is, the liquid metal ion source according to the present invention has Tl
-A ternary alloy of Mg-Se with a composition ratio of 50
~55:8~12:35~40 atomic%.

The present invention will now be explained based on the attached drawings. Figure 1a is a graph showing the relationship between the composition ratio and melting point of Tl-Mg alloy, and the melting point of Tl alone is approximately
300℃, and the melting point of Mg alone is about 650℃.
However, when the Tl:Mg ratio is around 80:20 atomic percent, the alloy has a eutectic point, and the melting point drops to about 200°C. Furthermore, the melting point of Se alone is approximately 220°C, but when it forms an alloy with Tl, as shown in Figure 1b,
When the atomic percent of Tl:Se is 27:73, it has a eutectic point,
Its melting point is approximately 170℃.

Based on the above facts, we continued to study and found that Tl-Mg with a melting point near or below 200℃.
- To obtain a Se alloy, Tl50-55 atomic%, Mg8-
It was found that Se was in the range of 12 atomic % and Se35 to 40 atomic %. If the composition ratio of the ternary alloy is outside the above range, the melting point will be 200° C. or higher, and the vapor pressure of Se will be high, making it useless as an ion source.

Among the above ternary alloys, Se serves as an n-type impurity for the - group compound semiconductor, and Mg serves as a p-type impurity. Tl also plays a role as a base metal for lowering the melting point of the alloy.

Next, the method for manufacturing this ternary alloy will be described. First, predetermined amounts of Tl and Se are placed in a crucible made of carbon, boron nitride, etc., and the temperature is raised to 180 to 190°C. As a result, a Tl-Se alloy liquid is formed. Mg in this melt
When a predetermined amount of is added and left at a temperature of 200 to 220°C for about 1 hour, a ternary alloy with a uniform composition is formed, molded into a predetermined shape, and cooled.

FIG. 2 shows an example of implanting impurity ions into a - group compound semiconductor substrate crystal using the ternary alloy of the present invention as a liquid metal ion source. 2
The ternary alloy 3 is loaded into a reservoir near the tip of the liquid metal ion source. When the emitter electrode 2 is heated to a predetermined temperature and the alloy 3 is melted, the emitter electrode 2 and the ion extraction electrode 4 disposed in front of it
When a voltage of several KV is applied to the ion beam 5, an ion beam 5 containing a mixture of three elements is emitted from the ion generator 1 due to field evaporation, field ionization, etc. Leads to 7. The mass separator 7 selectively separates and releases only target ions from the mixed ions. A beam 9 of emitted target ions is passed through an ion focusing system 1
0, ions are implanted into a predetermined position of the semiconductor substrate crystal 8 by the deflection electrode 11, and a pattern is drawn. When the injection of the target ions is completed, a command signal is sent to the mass separator 7 to selectively separate and release only the next target ions, and a predetermined pattern is drawn in the same manner as described above.

As mentioned above, by using the ternary alloy according to the present invention as a liquid metal ion source in a field emission ion beam generator, any n-type or p-type impurity ions can be removed during the ion implantation operation without replacing the ion source. It can be implanted continuously onto the same substrate crystal, and therefore it can be used for maskless ion implantation using a focused ion beam on the order of submicrons, which has been proposed recently, for highly integrated electronic devices, optical The device will be easily formed. In particular, when Se is implanted at a high concentration,
Since the alloy of the present invention is known to exhibit a high activation rate and has a low melting point as described above, it is easy and convenient to use it for high-concentration p-type ion implantation as described above.

Next, the present invention will be explained with reference to examples. Tl and Se were placed in a crucible made of boron nitride at a ratio of 10 g and 2.7 g, and the temperature was raised to approximately 190°C, resulting in the formation of a Tl-Se alloy liquid. Next, add 0.22g of Mg to this binary composite liquid.
When the mixture was added at a certain ratio and left at about 210° C. for about 1 hour, it became an evenly dispersed Tl-Se-Mg ternary alloy, which was molded into a predetermined shape as an ion source and cooled. The melting point of this ternary alloy was about 190°C.

This ternary alloy was loaded as a liquid metal ion source into the reservoir of the ion generation section equipped with a tungsten emitter electrode of a maskless ion beam implanter having the structure shown in FIG.
By heating to around 200°C, the ternary alloy melted and the surface of the emitter electrode began to get wet. In this state, there is a
When a high voltage of ~6KV was applied, a mixed ion beam of Tl-Mg-Se was emitted from the electrode tip.

As a result of ion separation of this ejected mating ion beam with an EXB mass separator, Mg, Se, Tl
ions were present in a ratio of approximately 2:7:10.

[Brief explanation of drawings]

Figure 1a is a graph showing the relationship between the composition ratio and melting point of Tl-Mg alloy, Figure 1b is a graph showing the relationship between composition ratio and melting point of Tl-Se alloy, and Figure 2 is a graph showing the relationship between the composition ratio and melting point of Tl-Se alloy. FIG. 1 is a schematic configuration diagram showing an example. DESCRIPTION OF SYMBOLS 1... Field emission type ion generator, 2... Emitter electrode, 3... Ternary alloy, 5... Mixed ion beam, 7... Mass separator, 8... Substrate crystal, 9...
Selective ion beam.

Claims (1)

[Claims] 1. A liquid for a field emission type ion beam generator, which is a ternary alloy of Tl-Mg-Se and has a composition ratio of 50 to 55:8 to 12:35 to 40 atomic percent. Metal ion source.