DE1119625B - Method for etching the surface of a semiconductor body - Google Patents

Description

The invention relates to a method for etching the surface of a semiconductor body Semiconductor device with a new etchant.

So far, electrochemical or purely chemical processes have been used to etch the surface of Semiconductor bodies, ζ. B. of germanium crystals applied. The automatic implementation of these procedures However, it has the following disadvantages: The known, purely chemical processes work with etching agents, which contain hydrofluoric acid, nitric acid or similar highly corrosive substances and therefore on the one hand endanger the operating personnel, on the other hand also other metal parts of the semiconductor arrangement attack on which no corrosive effect should be exerted. To avoid this disadvantage it was customary up to now to pass the semiconductor arrangement through at the points that are not to be etched Applying wax to protect or a fine stream of the corrosive etchant just on the too Pour corrosive surfaces. However, these measures are too cumbersome for mass production. at the use of an electrochemical process does not run the risk of undesirable etching Places, however, an even etching only of the areas to be etched is to be considered the uneven distribution of current in arrangements with complex geometrical shapes or of larger dimensions difficult. In order to avoid this disadvantage, one has gone over to Cathodes of a special shape should be used, but here, too, laborious manipulations are again involved necessary.

The method according to the invention avoids these disadvantages by making it possible for the first time at hand, with the help of a purely chemical etching process, only the semiconductor surfaces of a semiconductor arrangement to be etched, even if the arrangement contains other metals such as copper, lead, etc., contains, which are also immersed in the etching solution.

The inventive method for etching the surface of a semiconductor body, for example from Germanium, a semiconductor device, is characterized in that the surface to be etched with treated with an etching solution consisting of hydrogen peroxide, caustic alkali and a complexing agent will.

Although it is already known, semiconductor bodies made of germanium with a mixture of hydrogen peroxide and caustic soda to etch. However, this known etching liquid did not contain a complexing agent and as a result was unsuitable for treatment

Method of etching the surface
a semiconductor body

Applicant:

Sony Kabushiki Kaisha,
Shinagawa, Tokyo (Japan)

Representative: Dr.-Ing. E. Maier, patent attorney,
Munich 22, Widenmayerstr. 4th

Claimed priority:
Japan August 25, 1956 (No. 22 027)

Mikio Yamamoto and Akio Amaya, Tokyo,
have been named as inventors

entire semiconductor arrangements that contain other metal parts besides germanium, ζ. B. made of copper, lead, etc., contain. If the etching liquid does not contain a complexing agent, so separate into in these cases small amounts of foreign metal, such as copper, which are dissolved by the etching liquid, in the form of a sparingly soluble compound, e.g. B. the hydroxide, on the semiconductor surface and affect the electrical properties of the semiconductor considerably. This is indicated by the addition of the complexing agent completely prevented. In addition, the complexing agent prevents also the decomposition of hydrogen peroxide through the catalytic action of heavy metal hone, such as B. copper ions because it converts these ions into complex ions. The invention is therefore suitable excellent for the mass production of semiconductor devices because it enables the entire device immerse in the etching bath regardless of their other metal components.

As complexing agents come according to the invention, for. B. potassium cyanide, sodium cyanide, ethylenediaminetetraacetic acid, Polyphosphoric acids or the like.

The etching solution is preferably made by mixing 0.01 to 20% caustic alkali, such as caustic soda, caustic potash or the like, 0.1 to 30% hydrogen peroxide and 0.01

109 749/515

Claims (1)

3 4 up to 10% of the complexing agent produced. The reverse current each of forty-two pieces Within these general limits, under fifty test pieces is 5 μΑιηρ at 25 V. Interest of easy washing after etching, these results are the same as those of that Etching speed, the durability of the solution, the usual electrolytic polishing achieved. Safety and the non-toxicity of the etchant as well as 5 (c) The case of the power transistor: From an economic point of view, the following alloyed npn- Proven to be the most favorable area: germanium power transistors with a collector Hydrogen peroxide 0.5 to 20% gate diameter of 2 to 2.2 mm and a specific x + ™ ii ™ i; ^{r J} _n * -! _ · _{<ϋ /} scnem resistance of 2 to 4 ohms will be 1 hour Ethylenediamine tetra- ¹⁰ . ^{35 C under Runren m} ™ ^e described above acetic acid 0 01 to 0 5% etching solution dipped to remove the surface of the ^{Etch s} '' letters, whereupon the transistors with water According to the invention, the etching is preferably washed at. The reverse current each of seven a temperature between 15 and 50 ⁰ C through- pieces under ten test pieces is under leads. 15 20 μΑηιρ at 25 V. The following description is based on a (d) A reduction in the concentration of the etching manium crystal turned off. The hydrogen peroxide occurs by means of decomposition of the hydrogen peroxide the germanium oxidizes to germanium oxide, the corrosive not even after 50 hours of standing at 45 ° C. alkali dissolves the germanium oxide to alkali germanate, (e) When etching a single crystal germanium half- and the complexing agent, on the one hand, prevents p-type conductors in the etching solution at 35 ° C the decomposition of the hydrogen peroxide by the constant stirring is the etching speed catalytic effect of heavy metal ions and, for example, on a (III) surface of the crystal on the other hand, the deposition of metal on the device 0.6 μ / min. manium surface showing a deterioration in (f) when etching a made of a semiconductor and electrical properties of the semiconductor cause 25 copper wires to exist in electrical device would. by the etchant according to the invention have the For the construction of semiconductor devices, copper wires will not have any adverse effects on the mainly nickel, cobalt, lead, tin, copper device. and the like used. These metals are weak against when using the caustic alkaline according to the invention Liquids are very resistant and there are no dangers to the operation by them, even if they are immersed for a long period of time, and the process is very negligible or attacked in traces. moderately in front of you, without the other metals . are attacked, so that the handling and the examples etching process are very simple. Furthermore, the Ober-Das Process using an etch surface of the etched semiconductor does not destroy itself by means of the following composition through when other metals together with the semiconductor leads: are present. 50/0 - ⁰ ^ invention is also used to treat Jj 0 1% Semiconductor devices of various types, both Ethylenediammetraacetic acid '.'. '.''.'.'.'. 0, '1% ° « ^{0 of} the drawn type and such complicated con jj Q j ^ _{est for} example of the pnp type, of the alloyed npn type, ² structure, suitable. The following results are achieved: (a) p-germanium of 3 ohms / cm is according to the patent claims: Lapping its surface with emery from the 45 1. Method of etching the surface of a fineness 304 for 30 minutes at 35 ° C in the above etching semiconductor body, for example made of germanium, immersed in the solution, the solution for etching characterized in that the to The corrosive surface of germanium is kept in motion with a surface made of hydrogen peroxide. Then the germanium is washed with water, caustic alkali and a complexing agent. The surface recombination velocity is treated 50 standing etching solution,
speed of the electron of the treated surface is 2. The method according to claim 1, thereby ge about 250 to 350 cm / s and is very stable. One indicates that the etching solution by mixing n-germanium surface is approximately the same from 0.01 to 20% caustic alkali, such as caustic soda, the etching result is achieved. Potash or the like, 0.1 to 30% hydrogen peroxide On the other hand, the recombination speed is 55 and 0.01 to 10% of a complexing agent, if the same surface area with a solution such as potassium cyanide, sodium cyanide, ethylene of bromine in a mixture of nitric acid , Acetic diamine tetraacetic acid, polyphosphoric acid or the like, acid and hydrofluoric acid is etched, for example, is produced.
200 to 250 cm / s. 3. The method according to claim 1 and 2, characterized (b) In the usual manner prepared alloyed npn 60 characterized in that the etching temperature at a Tempe-germanium transistors having a Kollektordurch- is carried out between 15 and 50 ⁰ C, diameter of 1 to 1.2 mm and a specific Resistance of the base material of each of the transistors Documents considered: from 2 to 4 ohms are 30 minutes at 35 ° C under German Auslegeschrift No. 1 000 533; Stir immersed in the etching solution described above, 65 German patent application W 2733 VIII c / 21 g (loading to etch the surface of the semiconductor, which was announced on December 11th, 1952); the transistors washed thoroughly with water "Journal of applied physics", 25 (1954), no. 5, will. The results are as follows: pp. 634 to 641. © 109 749/515 12.61