JPS5837691B2 - Method for manufacturing compound semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention improves a method for manufacturing a compound semiconductor device, particularly a heat treatment method for activating implanted atoms in an ion implantation layer formed from the surface of a compound semiconductor crystal substrate containing arsenic to the inside of the substrate. The present invention relates to a method of manufacturing a compound semiconductor device.

With the demand for ultra-high speed and ultra-high frequency semiconductor devices, semiconductor devices using compound semiconductors such as gallium arsenide GaAs, which have higher mobility compared to silicon semiconductor crystals that have already been used as semiconductor device materials, are becoming more and more popular. It is attracting attention.

However, from the standpoint of manufacturing these semiconductor devices, since compound semiconductors are compounds, they are more difficult to perform various reaction treatments on than single element semiconductors such as silicon semiconductors.

Ion implantation technology, which is attracting attention today as a method for manufacturing semiconductor devices, has one structure when applied to compound semiconductors. There is no established method to stabilize heat treatment by preventing elements from evaporating.

A heat treatment process performed to activate an ion-implanted layer formed on the surface of a compound semiconductor containing arsenic As, such as a gallium arsenide crystal substrate, as a method of preventing arsenic from evaporating from the surface of the gallium arsenide substrate during this heat treatment. , various methods are used to deposit various protective films on the surface of the substrate, usually thermal decomposition method,
Or silicon nitride Si3 formed by the Subatsuta method
A N4 film is used as a protective film.

The surface-protected gallium arsenide substrate is then exposed to hydrogen H2 or, for example, E. K. K Rao et al. Apple.
Phys. 4 9A 7.3898 (1978), heat treatment is performed in an argon gas atmosphere.

However, in this case, the deposited protective film often alters the surface of the gallium arsenide substrate (and the extent of the alteration is
It is significantly influenced by the type of protective film and deposition conditions.

In this method, since the gallium arsenide substrate is not in direct contact with the atmospheric gas, the properties of the ion-implanted layer are hardly affected by the type of atmospheric gas, and are solely influenced by the type of protective film and deposition conditions. Become.

In order to eliminate such drawbacks, a method for preventing arsenic evaporation from the surface of a gallium arsenide substrate without using a surface protective film is as follows.
For example, Arai Kasahara is J. Electrochemsoc,
126A11.19 (1979), hydrogen arsenide gas is heated at a molar partial pressure of 0.2 to 10 Torr in an open tube.
There is a method of heat treatment at a temperature of about 750 to 900° C. in a hydrogen gas atmosphere containing a certain degree of hydrogen gas.

However, when hydrogen is used as the atmospheric gas in this way, the atmosphere during the heat treatment becomes strongly reducing at the high heat treatment temperature as described above, and exerts a reducing action on the reaction vessel etc., causing alteration and deterioration of the vessel etc.

Moreover, since hydrogen is a very light gas, there is a large density difference between it and hydrogen arsenide gas (it is difficult to mix hydrogen and hydrogen arsenide uniformly, and under the high temperature conditions mentioned above, gas convection is difficult). It is intense and the atmosphere tends to become uneven.

Due to this reason as well, in the method using hydrogen, the activation rate of the ion-implanted layer varies greatly within the substrate surface, and the reproducibility for each annealing is not good.

Furthermore, in order to obtain a high activation rate of the ion-implanted atoms, as shown in the cross-sectional view of FIG. It is necessary to place the substrate and another gallium arsenide substrate 13' (not shown) on top of each other with the surface on which the injection layer 11 is formed facing inside, and to install the substrate in the heat treatment tube.

However, even in this case, the activation rate is affected by the adhesion to the overlapping substrate 13 and the 130 types of substrates, so the activation rate is not uniform within the substrate surface, and the reproducibility for each heat treatment is also good. do not become.

This invention was made to eliminate the above-mentioned drawbacks, and it is possible to uniformly and reproducibly implant atoms in an ion-implanted layer formed into a compound semiconductor substrate containing arsenic as a crystal structure element with a high activation rate. <The purpose is to provide a method for heat treatment.

That is, the present invention includes a step of forming an ion implantation layer from the surface of a compound semiconductor crystal substrate containing arsenic as at least one constituent element into the interior of the substrate, and a step of forming an ion implantation layer into the inside of the compound semiconductor crystal substrate containing arsenic as at least one constituent element, and adding hydrogen arsenide gas to argon gas, which is essentially the main ingredient. a step of activating implanted atoms in the ion implantation layer by heat-treating 1S in which the ion implantation layer surface of the substrate on which the implantation layer is formed is exposed in a mixed atmospheric gas. It's in the manufacturing method.

In this invention, when an ion-implanted layer of a compound semiconductor containing arsenic as one of the constituent elements is activated by heat treatment without using a protective film, the activation rate and its reproducibility depend on the type of atmospheric gas. This was done after discovering the fact that

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 is a schematic diagram of a heat treatment system used when heat treating gallium arsenide by the method of this example.

A boat 22 made of quartz or the like is inserted into an electric furnace 21 having a wide constant temperature range, and a gallium arsenide substrate 12 including an ion-implanted layer 11 is placed thereon.

In this manner, heat treatment is performed while inert argon gas containing hydrogen arsenide at a molar partial pressure of ITorr is flowed from the inlet 24 of the open quartz tube 23.

In this example, the temperature of the electric furnace 21 was set at 850'C.

This temperature is appropriately changed depending on the type of atoms to be implanted and the amount implanted.

In addition, the vapor pressure of arsenic, which makes up gallium arsenide crystals, increases when the heat treatment temperature is increased, so in order to prevent gallium arsenide from decomposing during heat treatment, the hydrogen arsenide partial pressure in the atmosphere must also be increased by increasing the heat treatment temperature. It must be increased accordingly.

The feature of this example is that an inert argon gas containing hydrogen arsenide is used as the atmospheric gas, and the surface of the gallium arsenide substrate 12 including the ion-implanted layer 11 is exposed to this atmospheric gas flow to perform the heat treatment. .

FIG. 3A shows the carrier concentration distribution in the depth direction and the carrier profile after the substrate is heat-treated by this method.

The ion implantation layer was formed by directly implanting silicon ions into a chrome-doped semi-insulating gallium arsenide substrate at an acceleration energy of 250 KeV and a dose of 2 x 101210 nS/crA.

The carrier profile obtained when heat treated by conventional methods is shown in Figures 8 and 8.

C is the IT of hydrogen arsenide gas at molar partial pressure on the substrate containing the injection layer.
As shown in FIG. 1, the substrate containing the injection layer and another gallium arsenide substrate are stacked together and heated in the atmosphere of 8. Pertains to heat-treated items.

A protective film is not used even in the case of a fall.

As is clear from FIG. 3, according to the method of the present invention, the electrical activation rate of implanted ions can be improved by 30 to 50% compared to the conventional method.

As can be seen from FIG. 3, the method of overlapping the substrates related to the opening results in a higher activation rate than the method of exposing the substrate surface to the atmosphere.

Hereinafter, when comparing the method according to this example with the conventional method, the conventional method related to the mouth will be cited as a comparative example method.

Ion implantation technology is attracting attention because of its good controllability and uniformity of impurity doping, so ensuring uniformity and reproducibility in heat treatment is an important point.

Therefore, the distribution of the activation rate of implanted ions in the substrate plane is compared between the method of this embodiment and the method of a comparative example, and is shown in the fourth column.

A relates to the example method, and ink mark relates to the comparative example method.

It can be seen that the method of the example provides results with much better uniformity than the method of the comparative example.

Furthermore, as shown in FIG. 5, the reproducibility of the activation rate for each heat treatment is also higher than that in the example method compared to the comparative example method.
It is recognized that all 11 treatment examples are excellent.

In this embodiment, one substrate is placed on a boat 22, as shown in FIG.

However, even if a plurality of substrates 131 to 139 are heat-treated in a furnace as shown in FIG. , nothing changes.

FIG. 7 compares the activation rate of each substrate when the substrates were heat-treated in the furnace arrangement shown in FIG. 6.

The numbers given to the substrates are the same as in FIG. 6.

It can be seen that the variation between each board is very small.

As described above, according to the method of the present invention, activation heat treatment can be performed stably, uniformly, and with excellent reproducibility at a higher activation rate than with conventional methods.

In addition, there is no need to cover the substrate containing the injection layer with a protective film or to overlap the substrates, which simplifies the heat treatment process and makes it easier to heat treat a large number of substrates at once.

In the example, gallium arsenide is used as a semi-insulating substrate. Although the explanation has been given using a substrate as an example, the same effect can be obtained even if a substrate formed by elongating a crystal substrate by an epitaxial method is used as the substrate.

Argon gas, which is the main ingredient in the heat treatment atmosphere, may be used as a mixture of two or three gases, such as helium or neon, by mixing argon with helium or neon, taking into account the specific gravity of the gas in order to control the gas flow.

Furthermore, the method of the present invention does not cause any trouble even if there is an insulating film such as an oxide film such as silicon oxide SiO2 or a nitride film such as silicon nitride on a part or the entire surface of the compound semiconductor substrate including the injection layer. Instead, it is possible to pattern the above film and selectively form an injection layer on the substrate, expose the surface of the injection layer, and then perform heat treatment. This is effective when using ion implantation technology in IC fabrication.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view of a substrate in the conventional method of stacking the substrates and heat treating them, Figure 2 is a schematic diagram of a heat treatment furnace used in an embodiment of this invention, and Figure 3 is a diagram showing the carrier profile after substrate annealing in the conventional method. Fig. 4 shows a comparison of uniformity within the substrate surface, Fig. 5 shows a comparison of reproducibility for each annealing, and Fig. 6 shows a comparison of the method and the embodiment method of the present invention. FIG. 7 is a diagram showing the arrangement of substrates in a furnace according to another embodiment of the invention, which shows variations in activation rate among substrates when the furnace arrangement is as shown in FIG. 6. In each figure, 11... ion implantation layer, 12.13-13,
... Gallium arsenide substrate containing an injection layer, 21 ... Electric furnace, 22 ... Substrate support stand (boat), 23 ... Quartz open tube.

Claims (1)

[Claims] 1. Forming an ion implantation layer from the surface of a compound semiconductor crystal substrate containing arsenic as at least one constituent element into the interior of the substrate, and mixing hydrogen arsenide gas with argon gas, which is essentially the main component. A compound characterized by the step of activating the implanted atoms of the ion implanted layer by heat treating the substrate on which the ion implanted layer is formed in an atmospheric gas with the surface of the ion implanted layer exposed. A method for manufacturing a semiconductor device.