JP2537296B2 - <II>-<VI> Intergroup compound semiconductor device manufacturing method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for manufacturing a II-VI intergroup compound semiconductor device, and more particularly to efficiently manufacturing a low resistance II-VI intergroup compound semiconductor device. The present invention relates to a method for manufacturing an II-IV intergroup compound semiconductor device.

[Prior Art] FIGS. 7A to 7C show cross-sectional structures of a conventional semiconductor device using zinc selenide (ZnSe), which is an II-VI intergroup compound. Such a semiconductor device is often used as a constituent element of a light emitting diode. Only the n-type region is shown,
A diode structure is formed by growing a p-type region on this or by forming a p-type region in the uppermost n-type region.

The semiconductor device shown in FIG. 7A is manufactured by the following manufacturing method, for example. A gallium arsenide (GaAs) substrate crystal having a lattice constant relatively close to that of ZnSe as a substitute for the ZnSe substrate 10
Used as 1. Zn is formed on the n-type GaAs substrate crystal 101.
The n-type ZnSe crystal 102 is epitaxially grown using the temperature difference method using a solvent.

The semiconductor device shown in FIG. 7B is manufactured by the following manufacturing method, for example. First, the n-type Zn is placed on the heat sink under the solvent (low temperature side) by the temperature difference method using the Zn solvent.
Se111 crystal is grown. An n-type ZnSe crystal 112 is epitaxially grown on this n-type ZnSe crystal 111 by the temperature difference method using a Zn solvent.

The solubility of ZnSe in a Zn solvent is not sufficiently high, and it is not easy to obtain a high growth rate. When the solvent is Se,
The solubility is considerably improved. When the solvent is Te, the solubility is significantly improved. Intermediate solubilities are obtained with Se-Te mixed solvents. On the other hand, the vapor pressures of these solvents are lowest in Te, slightly higher in Zn, and extremely higher in Se.

The semiconductor device in FIG. 7C is manufactured by the following manufacturing method, for example. A solution prepared by mixing Te and Se at an arbitrary ratio is used as a solvent, and an appropriate amount of a source crystal and a Group III to VII element are added to the solvent, and the lower part of the solvent (low temperature side)
Crystal growth of n-type ZnSe 121 is performed on the heat sink by the temperature difference method.

[Problems to be Solved by the Invention] In the above-described method for manufacturing a semiconductor device of FIG. 7A, since crystals having different constituent elements are used as the substrate, lattice defects due to lattice mismatch and from the substrate to the growth layer are caused. There is alteration of the crystal layer due to the diffusion of.

In the method of manufacturing a semiconductor device shown in FIG. 7 (B) described above, since the growth rate of ZnSe that becomes a substrate crystal is slow (0.5 μm / hour or less), a substrate crystal having an appropriate thickness is used. It takes time to get.

In the method of manufacturing the semiconductor device shown in FIG.
The composition of the grown crystal deviates from the stoichiometric composition ratio (stoichiometry) because it is grown in a solvent containing a considerable amount of. Therefore, the grown crystal does not have low resistance.

An object of the present invention is to provide a method for efficiently producing a II-VI inter-group compound semiconductor device having a low resistance without lattice defects or alteration of the crystal layer.

[Means for Solving the Problems] According to the present invention, a Group III or Group VII element is added to a solvent in which Te and Se are mixed at an arbitrary ratio, and a source crystal is arranged at a high temperature portion to obtain a temperature difference. Of II-VI group compound semiconductors containing Zn as a constituent element in the low temperature region by the first method
Step, a second step of forming the II-VI group compound semiconductor crystal prepared in the first step into a flat plate shape, a suitable source crystal and a group III or VII element are added to a Zn solvent, A third step of epitaxially growing a II-VI group compound semiconductor containing Zn as a constituent element on the tabular crystal formed in the second step by a difference method. A method of manufacturing a semiconductor device is provided.

In the crystal growth containing S such as ZnS and SnSS, S may be mixed with Se and Te in the solvent.

[Operation] The Se-Te solvent has a higher solubility of ZnSe and the like than the Zn solvent, and a high growth rate can be obtained. Further, as the mixing ratio of Te increases, the solubility increases and the vapor pressure decreases, but the amount of Te mixed into the crystal also increases.

According to the first step described above, a II-VI group compound semiconductor crystal having Zn as a constituent element to which a Group III or VII element is added can be obtained at a relatively high growth rate. A plurality of substrate crystals can be obtained by forming the II-VI group compound semiconductor crystal into a flat plate shape in the second step. In the third step, an appropriate source crystal and Group III or Group VII element are added to the Zn solvent,
II-VI group compound semiconductors having Zn as a constituent element are epitaxially grown on the flat crystal formed in the step. Therefore, the substrate crystal, which is still high in resistance after the second step, is subjected to heat treatment in Zn to improve the stoichiometry of the crystal and lower in resistance.

[Example] As a specific example of the present invention, description will be given below by taking ZnSe which is a II-VI group compound semiconductor as an example. The present invention is a method for manufacturing a II-VI intergroup compound semiconductor device comprising three steps.

First, the first step is a step of forming an n-type crystal to be a substrate. Referring to FIG. 1, a heat sink 6 made of a material having a high thermal conductivity such as carbon is housed and fixed to the bottom of a quartz crystal growth ampoule 1. On the heat sink 6, a solution prepared by mixing Se-Te as the solvent 2 in an arbitrary ratio is stored. Group III or VII in solvent 2
An appropriate amount of group element is added. Further, a ZnSe crystal 3 as a growth raw material (source crystal) is housed. After accommodating the solvent 2 and the source crystal 3 in the growth ampoule 1, the inside of the ampoule is evacuated and sealed. The ampoule having such a configuration is placed in an electric furnace having a temperature gradient (for example, ΔT−5 to 15 ° C./cm) as shown on the right side of the drawing. Then, the source crystal 3 in the upper high temperature portion is dissolved and diffused in the solvent 2 until the saturated solubility is reached. The melted source crystal 3 is transported in the temperature gradient and reaches the vicinity of the upper surface 7 of the heat sink 6. Since the temperature in the vicinity of the upper surface 7 of the lower heat sink 6 is lower than that in the upper portion, the solution becomes a supersaturated solution and grows a bulb-shaped crystal on the upper surface 7 of the heat sink 6. Carbon heat sink 6 for growing crystals
The upper surface 7 is flat and mirror-finished.

The growth rate by the temperature difference method varies depending on the mixing ratio of Se: Te, the growth temperature Tg (the temperature near the upper surface 7 of the heat sink 6 on which the crystal grows), the temperature gradient, and the like. As an example, FIG. 2 shows the growth rate dependence on the temperature gradient ΔT when Se: Te = 30: 70 and the growth temperature Tg = 950 ° C. As the heat sink, a carbon rod having a diameter of 8 mm and a length of 100 mm was used. In the figure, the graph indicated by ○ is the growth rate near the center of the crystal growing in bulk, and the graph indicated by △ is the growth rate near the peripheral edge of the crystal growing in bulk. Indicates. It can be seen that the growth rate of about 10 times or more can be easily obtained compared with the growth rate of about 0.5 μm / hour or less when the Zn solvent is used.

When the Se-Te mixing ratio is changed, the growth rate changes with the Te amount as follows, for example. Se: Te growth rate (μm / hr) 10:90 6.0 30:70 5.0 45:55 3.8 As the amount of Te increases, the pressure inside the ampoule decreases and the growth rate increases, but Te is mixed into the crystal. The amount of Se can be decreased by increasing the amount of Se, but the pressure in the ampoule increases and the growth rate decreases. For the growth of II-VI intergroup compound semiconductors containing Zn as a constituent element such as ZnSe and ZnS, a solvent in which Se-Te is appropriately mixed is preferable. In the case of a crystal containing S, S may be further mixed.

The second step is a step of slicing the bulk crystal formed by the above-described growth method into a wafer by a slicing machine or the like. In FIG. 3, 11 is the first
A bulk crystal formed by the method shown in the figure, and 12 is a wafer crystal substrate obtained by slicing the crystal. The slicing thickness was set to 0.6 to 1.5 mm so as to be easily handled in the step of epitaxially growing the substrate and the device manufacturing step. Further, an n-type ohmic electrode was attached to the wafer-shaped crystal obtained by slicing in this way, and electrical characteristics were examined, but no current flowed due to high resistance.

The final third step is a step of epitaxially growing an n-type crystal using the n-type wafer as a substrate. Referring to FIG. 4, a heat sink 26 similar to that shown in FIG. 1 is housed and fixed to the bottom of a quartz crystal growth ampoule 21. The substrate crystal 12 is arranged on the heat sink 26, and the substrate crystal 12 is fixed by the substrate stopper 25. The substrate crystal 12 is the second
Wafer-like n-type ZnSe sliced by process
It is a crystal. The substrate stopper 25 is a ring made of quartz or the like similar to the growth ampoule 21. A solution 22 using Zn as a solvent is accommodated on the substrate crystal 12. solution
An appropriate amount of Group III or Group VII element is added as an n-type impurity in 22. In addition, ZnSe crystal 23 as a growth raw material
Is housed. Since the diameter of the source crystal 23 is larger than the inner diameter of the substrate stopper 25, the source crystal 23 is fixed to the substrate stopper.
Held by 25. Substrate crystal 1 in growth ampoule 21
2. After containing the substrate stopper 25, the solvent 22 and the source crystal 23, the ampoule 21 is evacuated to a vacuum and sealed. The ampoule having such a configuration is placed in an electric furnace having a temperature gradient (eg, ΔT = 5 to 15 ° C./cm) as shown on the right side of FIG. Then, the source crystal 23 in the upper high temperature portion is dissolved and diffused in the solvent 22 until the saturated solubility is reached. The melted source crystal 23 is transported in the temperature gradient and epitaxially grows on the upper surface of the substrate crystal 12.

Fig. 5 shows II of the two-layer structure manufactured through the following steps.
FIG. 7 is a cross-sectional view of an n-type II-VI group compound semiconductor to which a group I or group VII element is added. In the figure, 31 is a substrate layer of a II-VI group compound crystal grown by using a Se-Te solvent (Fig. 1), and 32 is II-VI grown by a growth method using a Zn solvent (Fig. 4).
3 shows a layer of group compound crystals.

FIG. 6 shows the n-type II-VI having the two-layer structure manufactured as described above.
It is a graph which shows the electric characteristic (impurity density) of each layer of a group compound semiconductor. The electrical characteristics differ depending on the growth conditions (addition amount of impurities, growth temperature Tg, growth rate, etc.) of each layer, but typical examples are shown in the figure. The growth condition of the crystal layer 31 by the growth method using a Se-Te solvent (FIG. 1) is a growth temperature Tg = 950.
C., temperature gradient .DELTA.T = 10.degree. C./cm, iodine VII of the Group VII element was used as an additive impurity, and the concentration of the solution was 0.3 mol%. The growth conditions of the crystal layer 32 by the growth method using a Zn solvent (FIG. 4) are as follows: growth temperature Tg = 1025 ° C., temperature gradient ΔT = 7.5
C./cm, the added impurity was iodine I of Group VII element, and the concentration of the solution was 1 × 10 ⁻⁴ mol%.

As can be seen from FIG. 6, the resistance of the crystal layer 31 grown in the Se—Te solvent is lower than that before the crystal layer 32 is epitaxially grown in the Zn solvent.
It can be seen that it has a shape structure.

Although the present invention has been described above with reference to the embodiments, the present invention is not limited thereto. For example, various changes,
It will be apparent to those skilled in the art that modifications and combinations can be made.

[Effects of the Invention] As described above, according to the present invention, in the first step,
Zn as a constituent element by the temperature difference method using Se-Te solvent
In the second step, bulk crystals of II-VI inter-group compound semiconductors are obtained and sliced into a substrate in the second step.
Since the epitaxial growth was performed on this substrate by the temperature difference method using a Zn solvent, the substrate crystal, which had a high resistance in the step of the second step, was subjected to heat treatment in the Zn solvent and the deviation from the stoichiometry of the crystal was observed. Is improved and the resistance of the substrate itself is lowered. Further, since the substrate is grown by the temperature difference method using Se-Te multiplication, a bulk crystal can be obtained efficiently. Since these two layers are the same II-VI inter-group compound semiconductor, there are no lattice defects due to lattice mismatch or alteration due to diffusion from the substrate to the growth layer.

[Brief description of drawings]

FIG. 1 is a graph showing a cross-sectional view and a temperature gradient of a crystal growth apparatus used in the first step in the example of the present invention, and FIG. 2 is a growth rate temperature in a growth method using a Se—Te solvent. 3 is a graph showing the gradient dependence, FIG. 3 is a sectional view of a crystal for explaining the second step in the above-mentioned embodiment, and FIG. 4 is a crystal growth apparatus used in the third step in the above-mentioned embodiment. Sectional views, FIG. 5 is a sectional view of a two-layer semiconductor device manufactured by the manufacturing method of the above embodiment, and FIG. 6 is an electrical characteristic of a two-layer semiconductor device manufactured by the manufacturing method of the above embodiment. FIG. 7 is a cross-sectional view of a semiconductor device manufactured by a conventional manufacturing method. In the figure, 1,21 …… Growth ampoule 2,22 …… Zn solvent 3,23 …… Source crystal 6,26 …… Heat sink 11 …… Bulk crystal 12 …… Substrate crystal 25 …… Substrate stop

Claims (1)

(57) [Claims] 1. A solvent containing Te and Se mixed in an arbitrary ratio.
A first step of adding a group III or group VII element, arranging a source crystal in a high temperature portion, and depositing a II-VI group compound semiconductor having Zn as a constituent element in the low temperature portion by a temperature difference method; The second step of forming the II-VI group compound semiconductor crystal prepared in the first step into a flat plate shape, and adding a suitable source crystal and a group III or VII element to the Zn solvent, and performing the above-mentioned step by the temperature difference method. And a third step of epitaxially growing a II-VI group compound semiconductor having Zn as a constituent element on the flat crystal formed in the second step. .