DE1521956C2 - Process for producing clean surfaces of semiconductor bodies with the aid of a gas mixture containing hydrogen halide - Google Patents

Description

1 2

The invention relates to a method for feeding. A flawless, planar removal is Manufacture of pure surfaces of semiconductor bodies is not possible with this etching process either, with the aid of a gas containing hydrogen halide. The disadvantages of wet etching processes mentioned are

mixed. by the gas etching process according to the invention

The invention is characterized in that 5 avoided; it can advantageously be used in the Aufdas Gas mixture in addition to the hydrogen halide wax cell itself shortly before the growth process Hydrogen and a halogen compound of the half- can be made. It is not required here contains, on the semiconductor body at borrowed, the geeiner by sawing the semiconductor rod To lap a temperature of about 50 to 500 ° C below the wafers before the gas etching its melting temperature for the duration of 1 to io or polish. Through the gas etching, the after . 60 minutes is conducted in such a way that an etching the sawing contaminated, rough and crystallographic reaction in the sense of a controllable removal of the disturbed surface layer of the carrier crystals of the semiconductor body takes place. cleans and smoothes. It is easy to do layers In the method according to the invention, it is a question of completely removing a defined thickness, so that it is a gas etching process. Especially in »5 there is no problem with the disturbed crystal connection can be completely removed from the half-layer using manufacturing processes.

Suitable conductor components that are produced by monocrystalline The method according to the invention can be used for

Deposition from the gas phase on etched carrier semiconductor bodies from the semiconducting elements, crystals are produced. Such semiconductor construction such. B. silicon or germanium, as well as for half elements preferably consist of a single crystal ao conductive compounds, z. B. of type A ^m B ^v , lined basic body with several zones differently turn. The geometric shape of the carrier has no borrowed conductivity type or different doping significance. It can e.g. B. rod-shaped or any approximate concentration. An essential prerequisite for differently shaped semiconductor bodies equally well gas-etched is the production of such technically useful structures.

One of the elements here is that the carrier crystal, in particular in the following the process according to the earth's surface, is pure and completely free of defects on the basis of the drawing and the construction errors. The carrier crystals are obtained, described in more detail. It shows
z. B. by sawing a single crystal semiconductor F i g. 1 a schematic representation of a pre-rod of the desired diameter. Radiochemical device for carrying out the investigations according to the invention have shown that when sawing 30 method,

of the semiconductor rod impurities relatively deep, F i g. 2 shows an enlarged illustration of the etching cell,

30 μ and more, are pressed into the crystal. Fin- F i g. 3 the dependency of the removal

However, semiconductor technology requires extremely flat growth) rates from the concentration of hydrogen chloride in the wax layers; therefore it is polished to a high gloss. Be in the reaction gas with silicon,
especially when sawing, but also when lapping and 35 In the F i g. 1 with 1 is a quartz tube with the polishing, the surface layer of the carrier gas inlet 2, with 3 a closure cap, with 4 a crystal due to the high mechanical stress gas outlet. The quartz tube 1 and the verchung badly damaged and disturbed. Such a closure cap 3 is formed by the etching cell, which can also be used as a disruptive and contaminated crystal as a completely wax cell carrier. Unsuitable in the closure. 40 cap 3 is a quartz tube 5 with the planar Ab-Man has tried to melt down the aforementioned disturbances by closing 6 and then to eliminate the holder 7 wet etching of the carrier disk. For that is appropriate. The holder 7 is used to hold a large number of different etching solutions in front of a heating rod 8, for. B. a silicon rod. Been hit on; z. B. Mixtures of hydrofluoric acid these is the semiconductor wafer 9 to be etched and nitric acid in varying proportions 45 placed as a carrier. In the quartz tube 5 a graphite coating, potassium hydroxide solution or sodium hydroxide solution of different stamps 10 is inserted, at 11 a high frequency concentration, etc., is adjustable. With 12 there is a quartz window, with 13, however, none of the proposed etching solutions fully evaporate for the halogen compound of half-satisfying. Most frequently, uneven conductor material, with 14.15 and 16 through taps, with attack by the caustic agent is observed. The disks show the inlet port for the hydrogen gas and have etched holes or are at least wavy. The inlet port for the hydrogen halide particularly denotes the uniform removal of thicker surfaces.

surface layers around the damaged upper crystal. The high-frequency coil 11 is first converted into a

to remove it is met with great difficulty. 55 placed in such a position that both the graphite-over In addition, it is hardly possible that the support stamp 10 and the lower part of the heating rod 8 crystal adhering impurities are completely in the high-frequency field. The graphite stamp remove. In addition, there is enough pure etching solution - it gets hot quickly. You wait until the heating element 8 gen not available in practice, so that the lower part glows; then the high frequency becomes general the etched crystal surface through the coil 11 and thus the heated zone in the heating rod Etching procedure also transported upwards as a result of cementation of impurities, namely in the position as The Fig. shows the effects of the etching solution on the crystal. 1 is shown. The temperature of the becomes impure. Another disadvantage of the wet-etched semiconductor wafer 9 can be caused by the quartz window The problem is that it is difficult for a 12 to be observed and monitored. The measurement precisely defined, predetermined thickness of the carrier temperature is carried out pyrometrically. To remove the flow crystal. velocities for each gas are means of not . It is already known to set the etching procedure with the help of drawn gas flow meters and of a gas mixture containing hydrogen halide.

Example 1 ° ^ ^{he emem} compound semiconductor, such as. B. Indhnn-

^v ■ arsenide, can exist, represents in a certain way over-

Production of clean surfaces of a carrier crystal, disc-shaped carrier crystals stacked on top of each other,

made of silicon, melting temperature 1420 ° C

5 Example 3

£? F, ^r. Evaporator 13, which uses silicon tetrachloride to produce clean surfaces of several

is filled, is kept at 0 ° C by a cold bath ... - “. _, ". . . ., ".,. .

and the apparatus is flushed with hydrogen. The SU- disk-shaped carrier plastic made of silicon

Ziumträgerkristall 9 is carried out by means of the high-frequency The heating of the rod 25 is carried out in the same coil 11 to a temperature of 1150 to 1250 ° C. as described in Example 1. This is followed by evaporation. Only now the upper, slotted half fer a gas mixture consisting of 1 mol of hydrogen from the rod, if the high-frequency gas is in a suitable position, and 0.16 mol of hydrogen chloride gas, is passed. This gas coil on one ISO to 1250 ⁰ C. Then, the mixture takes 0.04MoI of gaseous form as already described in Example 1, gas-etched. One silicon tetrachloride on. This gas mixture represents the smooth, shiny surfaces on the heated etching gas that is fed into the etching cell for gas etching of the rod end; all panes are etched at the top and bottom, transferred to a carrier crystal heated to 1150 ° C. Etch for 3 minutes. In this case, from the carrier position of the desired semicrystalline semiconductor arrangements, a 45 μ thick surface layer of monocrystalline conductive material is deposited on this carrier. The etched surface is smooth and shiny, ao beat. After the etching, the supply of hydrogen chloride is deposited on top and bottom of similar semiconductor layers. blocked by closing the valve 19. You can then let it cool down in the hydrogen stream, now in the same cell, after switching to and then separating the panes. Gas mixture hydrogen and silicon tetrachloride, which each constituent of the etching gas has an important, desired, single-crystalline silicon layer to fulfill its function during the etching process. The water wax and finally the finished semiconductor device serves both as a carrier gas and for cross-linking in the hydrogen stream. thinning, especially of the hydrogen halide content.

As a heating pad for the carrier crystal, he can also take part in the etching process, which z. B. also pure graphite and other materials that have become known by monocrystalline deposition from the gas phase in the process of silicon and chlorine water as hydrogen halide technology for the production of semiconductor devices are used. Si + 4HCl = # = SiCl ₄ + 2H ₁ .

_B. · 1 2 expires. One might assume that it is sufficient to use chlorine-

ueispi _{35 wassers} t _o ffg _as for gas etching only

Production of clean surfaces of a carrier crystal However, detailed investigations have shown

from indium arsenide, melting temperature 946 ° C that hydrogen chloride gas alone or with hydrogen

diluted hydrogen chloride no smooth, shiny

The evaporator 13, which is filled with arsenic chloride gives the surfaces. Rather, you get rough ones

^{is, is kept at 50 0} C by a water bath 40 surfaces with many more or less deep

and the apparatus is flushed with hydrogen. The holes. Such surfaces are, however, used as a carrier

Carrier crystal 9 made of InAs is made by means of the high for the deposition of semiconductor material from the

frequency coil 11 to a temperature of 800 ° C gas phase in monocrystalline form completely unsuitable,

heated. Then the evaporator mixes the hydrogen-halogen

a gas mixture consisting of 1 mol of hydrogen 45 hydrogen mixture little of a gaseous halo

and 0.16 mol of hydrogen chloride. The gas gene connection of the corresponding semiconductor material,

mixture takes about 0.04 mole of gas. B. SiCl ₄ , so you get smooth, shiny etching

moderate arsenic chloride. This gas mixture creates surfaces.

The etching gas is used for gas etching the InAs carrier crystal heated to -800 ° C by changing the proportion of halogen water into the reactant or the halogen compound of the semiconductor material tion cell forwarded. You etch for 15 minutes. The one in the etching gas can be the removal rate etched surface is smooth and shiny. One can vary within wide limits; it gets bigger through then, according to known methods, increasing the proportion of hydrogen halide or reducing the proportion of the halogen compound of the desired monocrystalline InAs layers to let something grow. 55 semiconductor material; conversely, it becomes smaller through

A great advantage of the inventive reduction in the hydrogen halide content or driving is that disc-shaped carrier increase in the proportion of the halogen compound of the Crystals even without any actual heating base of semiconductor material. The removal rate is can be etched and coated. This also depends on the etching temperature, Driving-wise, the further exemplary embodiment of the invention is explained with reference to FIG. 2 and a 60. appropriate etching process to a specific etching problem

In Fig. 2 a quartz tube can be set with 21, and one with 22 can be set precisely. Bracket, with 23 a graphite stamp, with 24 an In F i g. 3 is the dependence of the removal rate High-frequency coil and with 25 a rod from half or growth rate for silicon carrier crystals of

denotes conductor material, which in its upper half 63 of the hydrogen chloride concentration in a constant

in the way as held in the German patent mixture of 1 mol of hydrogen and

1138 481 described, is provided with slots 26. 0.04 moles of silicon tetrachloride at one temperature

This upper part of the rod, the z. B. made of silicon of 1150 ° C shown graphically. On the abscissa

the molar hydrogen chloride concentration is plotted in relation to a mixture of 1 mol of hydrogen and 0.04 mol of silicon tetrachloride. The ablation rate is plotted upwards on the ordinate and the growth rate in μ per minute downwards. The course of the erosion rate or growth rate is shown by curve 31. The erosion rate decreases with decreasing hydrogen chloride concentration. It will be zero at the. Concentration 0.0125 mol HCl / (1 mol H ₁ + 0.04 mol StClJ. With this gas composition, the reaction goes through a state in which it is ideally reversible. In this state, silicon is neither removed nor grows A reduction in the hydrogen chloride concentration leads to a region in which the reaction proceeds in the opposite direction, i.e. in which silicon grows.

According to these statements, the presence of the halogen compound of the semiconductor is only guaranteed Substance in the etching gas the desired, largely reversible course of the etching reaction, which is the prerequisite is for the perfect, planar removal of the semiconductor material. In the examples given, it becomes the hydrogen-hydrogen halide mixture before it enters the Atzzellc from a suitable Container added. However, procedures are also possible in which the halogen compound of the semiconductor material during the process execution ■ formed by a reaction of the semiconductor material with the 3% hydrogen halide of the hydrogen-hydrogen halide mixture and only thereby the etching gas composition is completed. In the case of the Silicon comes here z. B. the reaction

Si + 4HCl _(Terd . ", Η" = SiQ ₄ + 2H ₁

35

into consideration. Of course, the reaction conditions must be chosen so that one for the subsequent etching process sufficient amount of hydrogen halide remains in the etching gas;

The reaction which leads to the formation of the halogen compound of the semiconductor material can either be carried out before the etching gas enters the etching cell or let it run off in the etching cell itself. The last-mentioned reaction procedure is particularly recommended for etching semiconductor materials that are based on a heatable base made of the same semiconductor material are arranged. You can z. B. over Silicon bodies which are made of silicon or a heatable siliconized material Underlay are arranged at a temperature of about 1050 to 1350 ° C a gas mixture of hydrogen and hydrogen chloride for a period of 1 to Conduct 60 minutes. As a base is z. B. a siliconized graphite board.

Claims (7)

Patent claims: 1. Method for producing clean surfaces of semiconductor bodies with the aid of a Gas mixture containing hydrogen halide, characterized in that the gas mixture which, in addition to the hydrogen halide Contains water and a halogen compound of the semiconductor material, via the semiconductor body a temperature of about 50 to 500 ° C below its melting temperature for the duration of 1 to 60 minutes is passed, in such a way that an etching reaction in the sense of a controllable removal the surface of the semiconductor body takes place. 2. The method according to claim 1, characterized in that the for controlling the The course of the etching reaction required halogen compound of the semiconductor is added to the hydrogen-hydrogen halide mixture from a suitable container. 3. The method according to claim 1, characterized in that the halogen compound des Semiconductor material before the gas mixture enters the etching cell by a reaction of the semiconductor material with the hydrogen halide Formed hydrogen-hydrogen halide mixture and thereby the composition of the etching gas is completed. 4. The method according to claim 1, characterized in that the halogen compound des Semiconductor material in the etching cell itself is formed by a reaction of the semiconductor material with the hydrogen halide of the hydrogen-hydrogen halide mixture and thereby the composition of the etching gas is completed. 5. The method according to claim 1 and 2 for producing pure, flat silicon surfaces, characterized in that a gas mixture consisting of 1 mol of hydrogen, 0.16 mol of hydrogen chloride and 0.04 mol of silicon tetrachloride ^{via silicon bodies at a temperature of 1150 to 1250 0 C} , Is conducted for 3 minutes. 6. The method according to claim 1 and 4, characterized in that silicon bodies on which a base made of silicon or a heatable, siliconized material are arranged at a temperature of about 1050 up to 1350 ° C a gas mixture of hydrogen and hydrogen chloride is passed for a period of 1 to 60 minutes. 7. The method according to claim 1 for producing pure InAs surfaces, characterized in that that over an InAs body at a temperature of 800 ° C a gas mixture consisting of 1 mol Hydrogen, 0.16 mol of hydrogen chloride and 0.04 mol of arsenic chloride, passed for 15 minutes will. 1 sheet of drawings