JPS634934B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a method for precisely controlling the transformation of a semiconductor surface accompanying thermal annealing of a semiconductor, which is a material to be annealed. Semiconductor crystals into which impurity atoms have been implanted through ion implantation are generally exposed to large extrusions, crystal defects occur, and atoms are placed in unstable positions. Thermal annealing of a semiconductor, which is the material to be annealed, involves keeping a semiconductor with such crystal defects at a high temperature for a certain period of time, allowing the atoms in the crystal to settle into stable positions and removing the crystal defects. , a semiconductor processing process performed to restore the functions necessary for device operation. (Prior Art) In such a thermal annealing process, if the semiconductor surface is exposed to high temperatures without any attachment, the easily volatile component elements in the semiconductor will evaporate and the atomic composition of the semiconductor surface will change significantly. The original properties required for device operation cannot be obtained. In particular, in semiconductors with many defects created by ion implantation, the atomic composition of the surface changes significantly. For this reason, conventionally,
For ease of operation and reproducibility, thermal annealing is generally performed using a horizontal furnace, and as shown in Figure 1, the surface of the semiconductor 1 is coated with an oxide film, nitride film, etc. A protective film 2 was applied to prevent volatile elements from evaporating from the semiconductor surface. By attaching this protective film on top of the semiconductor, the cap
However, in this method called annealing, since the thermal expansion coefficients of the protective film and the semiconductor are generally different, strain tends to occur near the interface between the protective film and the semiconductor at high temperatures. This often causes crystal defects and impairs electrical and optical properties. For this reason, a method called capsule annealing, which does not attach solid substances to the semiconductor surface, was devised. In this case, it is necessary to take measures to increase the vapor pressure of the volatile element in order to prevent it from evaporating. Figure 2 is an explanatory diagram of the principle of conventional capsule annealing using gallium arsenide (GaAs), a typical compound. (AsH ₃ )・Gas 6 is flowed through the introduction pipe 7,
Send it onto the gallium arsenic sample 1 placed under high temperature,
The arsenic vapor pressure on the semiconductor surface is increased. This conventional method requires the handling of large quantities of highly toxic arsenic and highly dangerous arsine, which is both toxic and flammable, complicating gas exhaust and treatment issues. In addition, when metallic arsenic is used, as shown in FIG.
Since it is necessary to divide the arsenic evaporation region 9 into two, the device becomes complicated and there are drawbacks such as an increase in the number of control parameters. This is particularly difficult for multi-compound semiconductors with three or more elements, and there are almost no examples. A similar heat treatment using a vertical furnace is available, but when a vertical furnace is used, the height is inevitably high, making it difficult to perform operations such as sample exchange. Furthermore, the temperature varies widely in the vertical direction due to changes in the sample position, gas flow rate, temperature changes on the outer wall, etc., and the vapor pressure on the surface of the sample 1 is usually not controlled. However, in thermal annealing, control of this vapor pressure is an essential condition, and whether the vapor pressure is high or low, the annealing effect is small. Also, when using a vertical furnace, due to temperature unevenness,
This may result in sealing points where the As pressure is too high, resulting in solid
There are many cases where the seal is not complete because of GaAs, etc. Attention is focused solely on suppressing volatile elements from the material being annealed, not controlling them; the volatile elements for suppression and the metal for sealing are separate. Therefore, precise steam pressure control is impossible.
Ion implantation has some drawbacks, such as the fact that it is nearly impossible to perform thermal annealing to activate carriers in only the surface layer, but thermal annealing of the surface layer performed by ion implantation requires A high level of control is required. (Problems to be Solved by the Invention) In view of the above points, the present invention provides that the vapor pressure of the volatile element (for example, arsenic) at a constant temperature is determined by the amount of the volatile element (for example, arsenic) dissolved in the liquid metal. By taking advantage of the changes shown, there is no need to supply metallic arsenic or dangerous arsine gas, which is highly toxic and flammable, from outside the reaction tube, and the furnace can be kept in a single temperature range. In addition, highly accurate vapor pressure control is possible by using a sliding type horizontal furnace, which allows the annealing process to be performed without attaching anything to the surface of the semiconductor sample, which is the material to be annealed, and increases reproducibility, stability, and reliability. The purpose of this work was to provide a horizontal furnace cat press annealing method that has high performance and can also ensure mass production. A further object of the present invention is to provide an annealing method that provides accurate vapor pressure control even for multi-component compound semiconductors during thermal annealing. (Means for solving the problem) Using an annealing method using a horizontal furnace, volatile elements contained in the material to be annealed are impregnated into the metal, which is solid at room temperature and liquid at the annealing temperature, and the metal is mixed with the material to be annealed. The metal is arranged vertically, the metal is poured into the opening of the container containing the material to be annealed at an annealing temperature, the space containing the material to be annealed is sealed, and the metal is poured from the material to be annealed at the annealing temperature. A cap press annealing method using a horizontal furnace metal solution seal, which is characterized by controlling the volatile elements released. Using an annealing method using a horizontal furnace, two or more different volatile elements contained in the material to be annealed are separately included in a metal that is solid at room temperature and liquid at the annealing temperature, and each is added to the material to be annealed. A cat press annealing method using a horizontal furnace metal solution seal, which is characterized in that the material is placed in each independent reservoir having a small hole communicating with the container containing the material, and the reservoir and the material to be annealed are arranged vertically. (Function) Next, the function of the present invention will be explained. first,
The vapor pressure of a volatile element (for example, arsenic in the case of gallium arsenide) at the annealing temperature is determined from known data, and the volatile element (for example, arsenic) is adjusted to the vapor pressure as shown in Figure 3 to obtain a corresponding vapor pressure. Put the amount calculated from the curve into the metal solution reservoir above the groove 11 of the top lid 10 in FIG. 4a, along with a metal that solidifies at room temperature (for example, tin), and place the top lid 10 containing the metal in the boat shown in FIG. 4b. Place the entire sample storage chamber into a horizontal furnace. The reason why we chose a horizontal furnace is because the temperature is uniform in the vertical direction, and by arranging each furnace vertically, we can make the temperature of the metal solution reservoir containing volatile elements the same as the temperature of the sample, allowing for highly accurate vapor pressure control. be able to. FIG. 4c shows the entire sample storage chamber. Evacuate the air in the furnace using a vacuum,
By replacing the metal solution with a gas such as nitrogen, hydrogen, argon, etc. and heating it, the metal solution in which volatile elements are dissolved flows, and the groove 11 is filled with the metal solution. Next, the sample storage chamber is held for a certain period of time until the metal solution has a sufficiently uniform composition, and then the temperature is lowered to room temperature, and after the metal solution is solidified, it is taken out from the furnace. This step is carried out without the sample 1 shown in FIG. Next, the semiconductor sample 1 to be annealed at room temperature is placed in the depression 1 of FIG. 4b.
3, cover with the top lid 10 containing the solidified metal solution prepared above, place it in a furnace, and heat it with nitrogen,
Completely replace the air in the furnace with gas such as hydrogen or argon. For this purpose, it is better to once evacuate the furnace and then fill it with the above-mentioned gas, and to further replace the gas more completely, it is better to repeat this process several times. Thereafter, the temperature of the furnace is raised to the annealing temperature and kept constant. Until this time, the sample storage chamber is kept at room temperature at the position indicated by 17 in FIG. After the temperature of the furnace has stabilized, the entire sample storage chamber is moved to the high temperature section using operating rods 14 and 15. As a result, the entire sample storage chamber reaches the annealing temperature,
The metal solution liquefies and flows into the groove, and the space (13 in FIG. 4b) in the depression containing the semiconductor sample is completely sealed with the metal solution. In addition, due to the evaporation of volatile elements from the metal solution, the vapor pressure of the volatile elements in this sealed chamber increases and can be made almost equal to the vapor pressure of the volatile elements from the semiconductor surface. Evaporation of volatile elements from the semiconductor surface can be precisely controlled. After the time required for annealing has elapsed, the entire sample storage chamber is moved again using the operating rods 14 and 15.
The metal solution is drawn out to room temperature portion 17 to solidify. Finally, the temperature of the furnace is lowered to room temperature, the storage chamber is taken out of the reaction tube, the upper lid 10 is removed, and the semiconductor sample is taken out. When thermally annealing a multi-component compound semiconductor, it is necessary to create many reservoirs of metal solution, and their functions and effects will be described in the following examples. (Example) FIG. 4 shows a configuration example of the present invention. The sample storage chamber used for the annealing of the present invention is the fourth
It consists of an upper lid shown in Figure a and a boat shown in Figure 4b, and used together with a, b and the top lid 25 as shown in Figure 4c. This sample storage chamber is pushed into a horizontal furnace. FIG. 4a is a view seen from the surface in contact with the boat 12, and the upper lid 10 has a groove 11 cut in the surface in contact with the boat, and the inside thereof is shown in FIG.
Fill with metal solution 16 as shown. The groove 11 of the upper lid 10 serves as a reservoir for the metal solution at the upper part of the upper lid 10;
The metal solution is connected through a small hole through which the metal solution passes, and when viewed in a longitudinal section through the small hole, the shape is as shown in FIG. 4c. A metal solidified at room temperature and a volatile element are simultaneously put into this upper metal solution reservoir, and then the whole is heated above the annealing temperature to melt the metal and pour it into the groove 11.
1 with this metal solution and seal the sample storage chamber.
It has a structure in which the reservoir for controlling vapor pressure and the material to be annealed are arranged vertically. Therefore, if the amount of metal solution is small, it is easy to remove the lid 25 and add the metal solidified at room temperature and the volatile element to the metal solution reservoir in the upper part. The reason why the metal solution reservoir and the sample position are located in a vertical relationship is that a horizontal furnace is used to maintain uniform temperature both above and below, and the vapor pressure of volatile elements in the metal solution in the metal solution reservoir can be precisely controlled by temperature. This is to do so. Semiconductor sample 1, which is the material to be annealed, is placed in boat 1.
The specimen is placed in a recess 13 cut into the specimen 2, and the upper lid 10 is positioned directly above the specimen, and can be moved using the operating rod 14 so that the groove of the upper lid completely surrounds the specimen. By using a horizontal furnace as an annealing furnace, the sample and the metal solution can be kept at the same temperature due to their vertical structure, and as shown in FIG. By sliding the top cover 10 with respect to the top cover 10, the top cover 10 can be placed directly above the sample. Furthermore, when taking out the sample after annealing, it is necessary to remove the top lid 10, but with metals that do not solidify at room temperature, there is a risk that the metal solution will leak and flow from the top lid, contaminating the sample with the metal solution, so removing the top lid 10 is not necessary. become unable to do so. Therefore, in order to easily remove the top cover 10 at room temperature, the metal solution must solidify at room temperature. Such measures are necessary in a horizontal furnace, and as long as the slide method is used, it is necessary to use a metal that is liquid at the annealing temperature and solid at room temperature. Suitable metals that solidify at room temperature include gallium, indium, tin, lead, bismuth, gold, silver, etc., and mixtures of two or more of these in appropriate proportions to solidify at room temperature. FIG. 5 shows a case where the sample storage chamber shown in FIG. 4 is attached to a horizontal furnace used for annealing. Operating rods 14 and 15 are connected to the heater 8 that heats the inside of the reaction tube 4.
The structure is such that the entire sample storage chamber can be moved from outside the reaction tube 4 using the . During and before and after annealing, hydrogen or an inert gas is allowed to flow in the directions shown in FIGS. 19 and 20 in order to keep the inside of the reaction tube clean. As a result of thermal annealing of a gallium arsenide crystal implanted with tellurium ions using the method described above, no thermal transformation occurred near the surface, the electrical activation rate of the tellurium impurity was over 80%, and the electron Very good results were obtained with a transfer rate of 6000 cm ² /V.sec or higher. This proves the effectiveness of this process as a fabrication process for high-speed integrated devices using gallium arsenide. Further, the following table shows an example of annealing conditions and annealing results. Even at a constant temperature, the surface resistance varies greatly depending on the mol% of the volatile element solution composition. On the contrary, this shows that when there is even a slight change in temperature, the annealing result changes greatly even if the solution composition is constant, as can be seen from FIG. That is, it is essential to use a horizontal furnace and to vertically arrange the metal solution and the material to be annealed.

[Table] In the above example, arsenic was cited as an element that is easily volatile, but similar elements include nitrogen, phosphorus, antimony, sulfur, selenium, tellurium, zinc, cadmium, mercury, etc. For example, gallium, phosphorous,
It can be applied to thermal annealing of compounds such as mercury, lead, tellurium, indium, phosphorus, gallium, and antimony, as well as elemental semiconductors such as silicon and germanium containing phosphorus, arsenic, and antimony. Although one type of element has been considered as the volatile element above, the present method can also be applied to thermal annealing of a multi-component compound semiconductor containing two or more types of volatile elements. For example, when sulfur is contained in gallium arsenide, by using a metal solution containing both arsenic and sulfur in tin as 16 in Figure 4c, the vapor pressure of arsenic and sulfur can be It is possible to control both at the same time. In addition, independently using two or more types of metal solutions,
It is also possible to control the vapor pressure of many volatile elements. In particular, multi-compound semiconductors (e.g.
This is essential when annealing (InGaAsP, InAsP, etc.). For example, the central portion 21 of the upper lid in FIG. 4a is modified to create two or more reservoirs as shown in FIG. 6, aligned perpendicularly to the material to be annealed, and a large number of small holes 24 are drilled in their lower portions. As shown in FIGS. 22 and 23 in FIG. 6, two or more types of metals that become solid at room temperature and the volatile elements required for each are placed in these reservoirs based on the data shown in FIG. 3. This is liquefied at the annealing temperature, and these metal solutions are poured into the small hole 24, and the surroundings are similar to those shown in Fig. 4, with the purpose of sealing the sample storage chamber and controlling the vapor pressure through the small hole. This is what I did. In this case, the diameter of the small hole is determined so that when the metal solution is poured, it will not leak due to surface tension and only the volatile element gas in the metal solution will enter and exit. Such a control method using two or more types of metal solutions becomes even more important when the sample is a multicomponent compound such as a ternary compound (for example, a compound such as GaAsP or GaAsSb) or a quaternary compound (for example, InGaAsP). In these multi-element compounds, As, P, Sb, etc. are volatile elements. For example, in InGaAsP, As and P are volatile elements.
have different vapor pressures, and it becomes necessary to control each volatile element independently and accurately. Therefore, for example, in the case of InGaAsPSb, in FIG. 6, 16 has Ga and As, 22 has In and Sb, and 2
In No. 3, annealing can be performed using a metal solution containing a combination of Sn and P. At this time, the amount of volatile elements As, Sb, and P that dissolve into Ga, In, and Sn metals, which are solid at room temperature, can be determined for each combination from the vapor pressure curve shown in Figure 3. In this way, by pouring a metal solution containing a volatile element that becomes solid at room temperature into the opening surrounding the sample, the sample is sealed and the vapor pressure is precisely controlled. This is possible by vertically arranging the wafers and performing thermal annealing. Furthermore, unless the furnace is of a horizontal type, it is quite difficult to equalize the temperature of the metal solution and the sample in a vertical arrangement, making it difficult to control the vapor pressure. (Effects) As described above, the present invention is to use a horizontal furnace to control the evaporation of volatile elements in the thermal annealing process of semiconductors by the pressure of the vapor from the volatile elements dissolved in the metal. , an annealing method that enables cat press annealing at high temperatures by arranging the material to be annealed and the metal perpendicularly to achieve a uniform temperature, and by adopting a structure that allows the metal solution to be poured into the opening around the sample. It's a method. With this invention, when using a horizontal furnace, there is no need to control the gas pressure from the outside, create two or more temperature regions, and there is no need to use highly toxic or flammable dangerous gases. This makes it possible to perform cat press annealing, which not only simplifies the processing process but also improves operability, safety, reliability, and reproducibility, making a major contribution to the semiconductor industry. Furthermore, by using a horizontal furnace, the material to be annealed and the metal solution containing volatile elements are placed at the same temperature due to their vertical arrangement, making it easy to control the vapor pressure at the surface of the material to be annealed. Also, the use of metals that are solid at room temperature and fluid at annealing temperatures allows the use of horizontal furnaces, which is not possible with vertical furnaces.
It became possible to bring the surface of the material to be annealed and the metal solution to the same temperature, improving controllability of the vapor pressure of volatile elements.

[Brief explanation of the drawing]

Figure 1 is a block diagram of the conventional cap annealing method. Figure 2 is a block diagram of the conventional cap press annealing method. Figure 3 is a diagram of the principle of the present invention. Figure 4 is a diagram of the configuration of the present invention. Figure 5. 6 is an operational example of the annealing method of the present invention, and FIG. 6 is a block diagram of another embodiment of the present invention. In the figure, 1 is a semiconductor sample, 2 is a protective film, 3, 3'
is a furnace heater, 4 is a reaction tube, 5 is a volatile element, 6
is the inflow direction of the gas containing volatile elements, 7 is the gas introduction pipe, 8 is the high temperature part for annealing, 9 is the volatile element evaporation control part, 10 is the upper lid, 11 is the groove, 12 is the boat, and 13 is the sample storage Chamber recess, 14 is a top lid operation rod, 15 is a boat operation rod, 16 is a metal solution,
17 is a room temperature position, 18 is an annealing position, 19 is a carrier gas inflow direction, 20 is a carrier gas outflow direction, 21 is a central part of the upper lid, 22 and 23 are metal solutions of different compositions, 24 is a small hole, and 25 is the top lid .

Claims (1)

[Claims] 1. In an annealing method using a horizontal furnace, volatile elements contained in the material to be annealed are impregnated into a metal that is solid at room temperature and liquid at the annealing temperature, and the material to be annealed and the metal are vertically aligned. The metal is poured into the opening of a container containing the material to be annealed at an annealing temperature, the space containing the material to be annealed is sealed, and volatile elements released from the material to be annealed are removed at the annealing temperature. A cat press annealing method using a horizontal furnace metal solution seal that is characterized by control. 2 In an annealing method using a horizontal furnace, two or more different volatile elements contained in the material to be annealed are separately contained in a metal that is solid at room temperature and liquid at the annealing temperature, and each of the materials to be annealed is housed. A cat press annealing method using a horizontal furnace metal solution seal, which is characterized by placing the material in each independent reservoir having a small hole communicating with the container, and arranging the reservoir and the material to be annealed vertically.