JPS6249618A - Vessel for diffusion of impurity - Google Patents

Abstract

PURPOSE:To prevent the occurrence of disturbance of a surface after diffusion, by providing a vessel with a space which communicates with a wafer accomodating space through slender holes and in which a fitting portion is held when a cover vessel is put on. CONSTITUTION:A vessel 1 and a cover vessel 12 are disposed separately in a reaction tube 20, and then the inside of the tube 20 is replaced by H2. Thereafter the vessel 11 is heated. On the occasion, the temperature of the cover vessel 12 is controlled, and the vessel is kept separated from the vessel 11 so as to prevent the thermal decomposition of a GaAs substrate 16 and the vaporization of impurity Zn101. After a Ga solution 14 is saturated with As, a sealing pipe 22 is removed and the cover vessel 12 is put on the vessel 11. At that time, an atmosphere surrounding the GaAs substrate disposed in a space closed up by the vessel 11 and the cover vessel 12 is filled up rapidly with a vapor phase containing Zn vapor which is thermally equilibrated with the Ga solution 14. Since the GaAs substrate 16 is set in the thermally- equilibrated atmosphere in a sealing vessel which is determined only by temperature, the state of the surface thereof is not varied, and thus the diffusion of Zn free from the occurrence of a stoichiometric defect can be effected.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an impurity diffusion container, and more particularly to the structure of an impurity diffusion container used when diffusing impurities into a compound semiconductor.

[Prior art and its problems]

Thermal diffusion of impurities is an essential process when manufacturing semiconductor devices. In many cases, thermal diffusion of impurities is also the highest temperature heat treatment step in the process of fabricating semiconductor devices. The higher the temperature of most materials, the weaker their mechanical properties, so careful consideration must be given to the materials during the heat treatment process. In particular, in compound semiconductors, stoichiometric defects are likely to occur during the heat treatment process.

In many cases, stoichiometric defects generated in these processes significantly impair carrier mobility, lifetime, etc., which are the basic properties of semiconductors, and therefore the performance of devices manufactured with stoichiometric defects will be low. In addition, stoichiometric defects are considered to impair the reliability of manufactured devices, and when diffusing impurities into compound semiconductors, consideration must be given to preventing the occurrence of stoichiometric defects. No.

Problems in impurity diffusion will be explained using the diffusion of p-type impurity Zn into GaAs as an example. The introduction of Zn into GaAs is an indispensable technology in the manufacturing process of GaAs light emitting diodes and double heterojunction lasers. When thermally diffusing Zn into GaAs, the atmosphere surrounding the base material GaAs is changed to Ga, A
If thermal diffusion is not performed as a gas phase consisting of S and Zn and in thermal equilibrium with GaAS, Ga and ΔS, which are constituent elements of the base material, will scatter from the surface of the GaAs base material, resulting in a large number of stoichiometric defects on the surface. Occur. As mentioned above, when Zn is diffused into GaAs in a system largely deviated from thermal equilibrium, surface disturbances even occur that can be easily seen by visual or microscopic observation.

H C Cathay Geninia (HoC).

Ca5ey Jr) and M B Pani7shi5 (M
,B.

Pan1sh) is a member of the Transactions of Metaradical Society A.I.M.E.
nsactions of Metalurgica
l 5ociety of A I ME) Volume 242,
G on pages 406-412 (March 1968)
The diffusion method in a closed tube using a diffusion source with a composition of 5% A, 50% As, and 45% Zn (hereinafter referred to as 5150/45 diffusion source) does not create defects on the surface and improves diffusion properties such as the effective diffusion coefficient and the concentration distribution of the diffusion layer. It was shown that the reproducibility regarding the parameters was extremely high↓As stated in this paper by Cathay et al., in order to perform diffusion with high reproducibility, it is necessary to consider it on the ternary phase diagram consisting of Ga, As, and Zn. , there must be thermal equilibrium between the diffusion source and the diffused material (there is no true thermal equilibrium while diffusion is occurring.To be more precise, the diffusion source and the diffused material must be in thermal equilibrium until the impurity concentration distribution disappears). This means that there is thermal equilibrium between

However, Zn was diffused until the impurity concentration distribution disappeared.
Thermochemically, GaAs is extremely close to GaAs, so there is a restriction that even if diffusion is occurring, it will be referred to as thermal equilibrium from now on. 5150/
45 The advantage of the diffusion source is that a thermal equilibrium condition is established between the diffusion source and the material to be diffused, so if only the diffusion temperature is determined, the diffusion parameters such as the effective diffusion coefficient and the concentration distribution of the diffusion layer are uniquely determined. be. However, this also means that it is difficult to select the diffusion parameters. Furthermore, diffusion using a 5150/45 diffusion source is carried out in a quartz ampoule, a so-called closed tube method, and is therefore not productive.

As an impurity diffusion technique, it is desirable to be able to freely select diffusion parameters and to be able to perform an open tube method. An example of open tube diffusion is usually A s H.

This method is carried out by flowing a quartz tube into a quartz tube to prevent thermal decomposition of the surface, but the controllability of diffusion parameters is poor.

For this reason, it is strongly desired to diffuse impurities by the open tube method, which allows the concentration of the diffusion layer for the compound semiconductor to be freely selected and which does not cause disturbances on the surface after diffusion.

[Purpose of the invention]

The present invention has been made in response to the above-mentioned needs, and its purpose is to diffuse impurities into compound semiconductors, which allows the concentration of the diffusion layer to be freely selected and which enables the realization of an open-tube method that does not cause surface disturbances after diffusion. The purpose of this invention is to provide a structure for a container for use.

[Structure of the invention]

The impurity diffusion container of the present invention includes a first open chamber that can accommodate a compound semiconductor wafer and a second open chamber that can accommodate an impurity to be diffused or a compound or mixture containing the impurity. A lid container having a fitting portion formed over the entire outer periphery; and a first space formed to accommodate at least the first open chamber when the lid container is placed on the lid container. and a second space that communicates with the first space through a pore and is formed to accommodate the fitting part when the lid container is placed on the container. .

[Function and principle of the invention]

Here, we will discuss GaA, which is attracting the most attention among compound semiconductors.
The operation and principle of the structure of the impurity diffusion container of the present invention will be explained with reference to FIGS. 1 and 2, using an example in which s is used as the material to be diffused and Zn is used as the impurity to be diffused. Generally, in the process of impurity diffusion into a compound semiconductor, the compound semiconductor and the diffusion atmosphere are thermodynamically non-equilibrium, so stoichiometric defects occur near the sample surface and it is difficult to control the diffusion parameters. becomes. A method intended for diffusion using an open tube method under thermodynamically equilibrium conditions involves introducing As H3 into the system to create an As atmosphere with controlled vapor pressure, and attempting to diffuse impurities within this atmosphere. However, since the As atmosphere is artificially controlled, it cannot be said to be extremely close to thermodynamic equilibrium conditions, and its control is not easy. Basically, it is ideal that thermodynamic equilibrium conditions can be automatically established as long as the temperature is determined, and that impurity diffusion can be performed. An example of the structure of the impurity diffusion container of the present invention is shown in FIG. By diffusing impurities in such a container, it is possible to automatically create impurity diffusion under conditions as close to thermodynamic equilibrium as possible by setting the temperature.

FIG. 1 shows a cross-sectional structure of a cylindrical container used for impurity diffusion according to the present invention.A container 11 and a lid container 12 are made of carbon, and a mud-like groove 13 dug in the container 11 allows a second A space is formed, and Ga 131 and GaAs 132 are prepared in this groove 13, which becomes a Ga solution 14 (FIG. 2) saturated with As at the impurity diffusion temperature. Furthermore, B20315 is placed in the groove 13, and this B20315 also melts at the impurity diffusion temperature and covers the Ga solution 14 due to the difference in specific gravity. The lid container 12 has a susceptor part 17 serving as a first open chamber in which a GaAs substrate 16 to be heat-treated is placed, and an impurity (in this case, Zn) to be diffused or a compound containing the impurity (ZTIA).
92 etc.) or a second open chamber 10 for containing the mixture. In this case, Zn1O
1 is stored. The temperature of the container 11 is now raised to a certain temperature of 500° C. or higher, and a cross-sectional view of the container 11 covered with the lid container 12 is shown in FIG. Ga in groove 13
131 contains GaAs whose solubility is determined only by temperature.
132 melts and becomes a Ga solution 14, with B20.15 covering it. When the lid container 12 is placed over the container 11, the tapered fitting portion 18 formed over the entire outer periphery of the lid container 12 is configured to at least touch the molten BzOi 15. . By creating the state ' shown in FIG.
It becomes sealed with B20315. The space inside the container is in contact with the Ga solution, which is a saturated solution of ΔS, through the many pores 19 made in the inner wall of the groove 13 of the container 11, so it is filled with a gas phase in thermal equilibrium. is also in thermal equilibrium with the GaAs substrate 16. This can be easily inferred from the liquid phase epitaxial crystal growth method.
Since the a solution 14 achieves a thermal equilibrium condition with the GaAs substrate 16, the gas phase which is in thermal equilibrium with the Ga solution 14 is in thermal equilibrium with the GaAS substrate 16, and does not damage the surface of the GaAs substrate 16. In addition, since the Ga solution 14 is isolated from the atmosphere outside the enclosure via 820315, the Ga solution 14 is
Dissociation and scattering of As and impurity Zn from the solution into the gas phase outside the container is also extremely small.

That is, in this state, the GaAs substrate 16 is placed in a gas phase containing Zn vapor and in thermal equilibrium.

In addition, B2O3 is a very famous material as a melting material for sealing the solution surface to prevent the dissociation and scattering of As from the solution into the gas phase during GaAs crystal pulling, and B20315
This extremely effectively prevents the dissociation and scattering of the constituent elements of the base material. That is, the gas phase inside the enclosure surrounding the GaAs substrate 16 is in thermal equilibrium with the GaAs substrate 16, and the composition of the gas phase is automatically determined only by the temperature, so the stoichiometric ratio on the surface is also always dependent on the temperature. It is possible to perform stable heat treatment.

〔Example〕

An embodiment of the present invention will be described in detail below with reference to the drawings. As shown in FIG. 3, a bottomed cylindrical container 11 made of carbon is placed on the bottom surface of the reaction tube 20. This container 11
has a cylindrical outer wall 11Δ with a tapered inner surface, and is formed concentrically with the outer wall 11A and has a height equal to that of the outer wall 1.
It has a cylindrical inner wall 11B that is lower than 1A. A plurality of pores 19 are bored at equal intervals along the circumferential direction of the cylindrical inner wall 11B, and the pores 19 communicate with the inner space of the inner wall 11B and the space between the inner wall 11B and the outer wall 11A. has been done.

The lid container 12 is housed in the reaction tube 20 while being connected to one end of a sealed quartz tube 22 that is movable in the axial direction. A fitting part 18 whose outer surface is tapered like the outer wall 11A of the container 11 is formed on the outer periphery of the bottom side of the lid container 12. The cylindrical part surrounded by the fitting part 18 includes an open susceptor part 17 that accommodates the compound semiconductor wafer, and an open susceptor part 17 that accommodates the impurity to be diffused, a compound containing this impurity, or a mixture containing this impurity. A storage section 10 is formed. A high frequency coil 21 for heat treatment is arranged on the outer periphery of the bottom surface of the reaction tube 20.

The operation of the impurity diffusion container of this embodiment will be described below using Zn impurity diffusion into GaAs as an example.

To actually perform heat treatment, first place the container 11 and lid container 12 separately in the reaction tube 20 as shown in Figure 3, and then flow H2 gas into the reaction tube 20 at a rate of 100 ml/min to ensure sufficient flow. Then, the inside of the reaction tube 20 is replaced with H2.

After that, a current is passed through the high frequency coil 21, and the container 11 is
Heat to 00°C. At this time, the lid container 12 keeps the temperature of the GaAs substrate 16 below 100.degree. C. and sufficiently removes the GaAs substrate 16 from the container 11 to prevent thermal decomposition of the GaAs substrate 16 installed in the lid container 12 and evaporation of the impurity Zn101.

By heating the container 11 to 800°C and keeping it for 30 minutes, Ga
Solution 14 is fully saturated with As. Thereafter, the current of the high frequency coil 21 is reduced to lower the temperature of the container 11 to 800°C. Thereafter, the quartz piece sealing tube 22 is moved from the outside of the reaction tube to quickly cover the container 11 with the lid container 12. This state is shown in FIG. At this time, the atmosphere surrounding the GaAs substrate placed in the space closed by the container 11 and the lid container 12 is quickly filled with a gas phase containing Zn vapor in thermal equilibrium with the Ga solution 14. As explained in the operation and principle of the invention, the GaAs substrate 16 is placed in a thermal equilibrium atmosphere inside the enclosure determined only by the temperature, so the surface condition does not change and stable Zn diffusion is possible without the occurrence of stoichiometric defects. can be done. The Zn concentration is determined by changing the amount of Zn101, and a diffusion layer having a surface concentration of 10'7 to 16 Iscm-3 can be obtained with good reproducibility. This concentration region corresponds to the surface concentration obtained with the 5150/45 diffusion source ~10
This is clearly a different area from 20cIl-3, and diffusion into compound semiconductors in which diffusion parameters can be freely selected with excellent reproducibility and controllability has been established by adopting the structure of the impurity diffusion container of the present invention. Ru.

As an alternative to the Ga solution 14, it is natural to use a Sn solvent saturated with As, considering that the liquid phase epitaxial method of GaA'S can also be performed using a Sn solvent, A molten liquid (
The material is not limited as long as it is (referred to as the first molten liquid). Also,
It is natural that CaF2 is an alternative to B20315, considering that it is a molten material for sealing the surface of a solution to prevent the dissociation and scattering of As from the solution into the gas phase during GaAs crystal pulling. Any melt (referred to as second melt) that melts like 820315 under heat treatment conditions, covers the melt, and has the ability to prevent the permeation of constituent elements of the base compound good. Further, the structures of the container 11 and the lid container 12 are not limited to those shown in the embodiments, and may have any shape. The requirement is to have a structure that can be sealed with the first melt between the container 11 and the lid container 12, and with the second melt that covers the first melt under heat treatment conditions. . Further, although carbon is shown as an example of the material of the container 11 and the lid container 12, BN etc. can also be used.
The material is not essentially limited. Furthermore, as is clear from the above description, this does not limit the types of heat-diffusing base material compound semiconductors, and is applicable not only to binary materials such as GaP and InP, but also to mixed crystal groups such as InGaAsP. Needless to say, this is the structure of the container for impurity diffusion. Furthermore, the type of impurity is not limited, such as Cd'PS.

〔Effect of the invention〕

By applying the impurity diffusion container of the present invention, the surface condition of the compound semiconductor wafer does not change, no stoichiometric defects occur, and stable impurity diffusion with excellent controllability of diffusion parameters can be performed. As a result, device manufacturing reproducibility is significantly improved, troubles in the process are drastically reduced, and man-hours can be reduced.
The effect is that the reliability of the obtained device is also extremely high.

[Brief explanation of the drawing]

1 and 2 are cross-sectional views for explaining the principle of operation of the present invention, and FIGS. 3 and 4 are cross-sectional views showing one embodiment of the present invention. 10 ...... Diffusion impurity storage section 101
・・・・・・・・・ Diffusion impurity Zn11 ・・・・
...... Container 12 ...... Lid container 13 ...... Groove 14 ...... Ga solution 15 ...
・・・・・・ B20316 ・・・・・・・・・
GaAs substrate 17 ...... Susceptor part 18 ...... Fitting part 19 ...... Pore agent Patent attorney Yoshiyuki Iwasa 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] (1) A first open chamber capable of storing a compound semiconductor wafer and a second open chamber capable of storing an impurity to be diffused, or a compound or mixture containing the impurity, and fitted over the entire outer periphery. and a first space formed to accommodate at least the first open chamber when the lid container is covered, and the first space and the pore. an impurity diffusion container, the container having a second space that communicates with the second space and is formed so as to accommodate the fitting portion when the lid container is placed on the container.