DD153938A1 - APPLICATION FOR THE CHEMICAL AATING OF CONNECTING SEMICONDUCTORS - Google Patents

Abstract

The invention relates to an etching solution for the chemical etching of compound semiconductors, in particular of GaAs and Ga (AsP) crystals, with which it is possible to remove very thin layers of defined thickness, as required, for example, in the structuring of semiconductor crystals for producing electronic components. The power solution is composed of a salt of peroxodisulfuric acid and concentrated sulfuric acid and stable over a longer period of time. The stationary removal rate is dependent on the peroxodisulfate concentration and can be reproducibly adjusted to technologically relevant values on the order of 5. 10 -2 mym.min high -1. Due to the isotropy of the dissolution rate of the GaAs and the low anisotropy of the dissolution rate of the Ga (AsP), masking gives rise to broadly rounded substructures of shallow depth.

Description

Etching solution for the chemical etching of compound semiconductors

Field of application of the invention

The invention relates to an etching solution for the chemical etching of compound semiconductors, in particular GaAs and Ga (AsP) crystals, and is used for the removal of very thin semiconductor layers of defined thickness, wherein the undercutting during etching by masks is minimal.

Characteristic of the known technical solutions For the etching of GaAs, a whole series of reaction mixtures on the basis of hydrogen peroxide (eg SCHELL, H _e A, Z. Metallkde 48 (1957) 158) and on the basis of nitric acid (eg B. BERKSTEIH I., J. Electrochem, Soc., 109 (1962) 270). In addition, solutions of bromine or chlorine in methanol (FULLER CS, ALLISON HW, J. Slectrochem, Soc 109 (1962) 880) and alkaline hypochlorite solutions (LOOF K., ZACH D., KALIMA H .; DD-WP 112 669 and BASI JS, BRD-OS 2 249 142). For the chemical removal of Ga (AsP) crystal layers, only a sulfuric acid-hydrogen peroxide-water mixture (PANCHOLY RK, GRANNEMAM, J. Electrochera, Soc., J_24 (1977) 430) and hot phosphoric acid have hitherto been known (GOTTSCHALCH V., HEllig W , BUTTER E., ROSIN H., FREYDANK G .; Kristall and Technik H (1979) 563).

All these solutions proved to be reproducible removal of very thin crystal layers, which requires very low etching speeds, as little suitable. This is mainly because of the difficulty, exactly reproducible reaction conditions when using very low and thus

- 2 - 22 ^ 85 2

difficult to adjust concentration of some components of the solution, as for example in. Bromine-methanol and hydrogen peroxide-containing solutions is the case. In addition, solutions with hydrogen peroxide are highly prone to self-decomposition.

A further drawback, in particular the solution of hydrogen peroxide and sulfuric acid known for Ga (AsP) etching, is that as the phosphorus content increases, the rate of dissolution becomes increasingly anisotropic, so that when etching through masks, strong undercuts with faceted boundary surfaces occur Manufacture of Electronic Components Zo B. may adversely affect the quality of subsequent vapor-deposited metal contact layers. The hot phosphoric acid used to visualize structural defects in Ga (AsP) crystals is also to be avoided because of its anisotropic dissolution rate for etching device structures.

Object of the invention

The aim of the invention is to remove crystal layers of defined thickness by chemical etching of compound semiconductors, in particular of GaAs and Ga (AsP), wherein the etching should be low during the etching of component structures in order to avoid contact interruptions in the subsequently deposited metal layer.

Explanation of the essence of the invention

The invention is based on the object to develop an etching solution for the chemical etching of component structures in compound semiconductors, especially in GaAs and Ga (AsP) crystals, which is stable over a long time and the semiconductor with lower, reproducible stationary and of the Crystal orientation dissolves largely independent speed. The desired isotropy of the dissolution rate is intended to meet the requirement for low undercutting with a rounded boundary surface.

Erfindungsgeraäß the object is achieved in that as etching solution, a reaction mixture of a salt of the peroxides

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Sulfuric acid and concentrated sulfuric acid is used. The peroxodisulfate serves to oxidize the semiconductor components, which are subsequently solvated during the detachment from the crystal structure and diffused into the interior of the solution. Due to the high viscosity and the low water content of the etching solution, the dissolution mechanism is so influenced by the use of high concentration of sulfuric acid that the rate of removal of the lattice units does not or only slightly depends on the surface orientation of the single crystal. The etching solution is stable for a long time. The removal of GaAs and Ga (AsP) crystal layers takes place at steady-state speed. Their value can be varied by the content of peroxodisulfate in the solution and is in the technical

-2 -1 nologically relevant order of magnitude of 5 · 10 / μm.min * Compared with previously used Atslösungen when etching through masks is less undercutting, wherein the resolution of GaAs isotropic and that of Ga (AsP) is almost isotropic.

embodiments

The invention will be explained below with two examples:

Example 1: GaAs is etched through a Si-JT ^ mask. The etching solution consists of 100 g of 96% sulfuric acid and 6 g of sodium peroxodisulfate.

-2 -1 speed is 7 · 10 / min.min · The

Undercuts are rounded and of shallow depth

Example 2: GaAs _n , -P _n "is etched through an SiO 2 mask.

The etching solution is composed of 100 g of 96% excess sulfuric acid and 4 g of ammonium peroxodisulfate.

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The removal rate is 7 · 10, um.min The undercuts are largely rounded and of shallow depth.

Claims (5)

Fulfillment claims A solution for the chemical etching of compound semiconductors, in particular of GaAs and Ga (AsP) crystals, characterized in that the etching solution is composed of concentrated sulfuric acid and a salt of peroxydisulphuric acid. -2 -1 2. Ätslösung according to item 1, characterized in that the Sal-3 ammonium peroxodisulfate. is. Solution according to item 1, characterized in that the SaIs is an alkali metal peroxodisulfate. 4 «detachment according to pt. 1 - 3, characterized in that the- removal rate, on the order of 5 .-. 10 / Ummin can be varied over the Peroxodisulfatkonzentratl'iü.