DD250955A1 - LOW TEMPERATURE PROCESS FOR PREPARING AN OXID DOUBLE LAYER ON METAL OR SEMICONDUCTOR SUBSTRATES - Google Patents

Abstract

The invention relates to a low-temperature oxidation process for producing an oxide double layer on metal or semiconductor substrates, which can serve as corrosion protection, diffusion barrier against diffusing ions, as a dielectric in capacitors and as a passivation layer in electronic components. The object of the invention is to produce adherent oxide bilayers on a metal or semiconductor substrate having a low mobile ion density (1011), low solid oxide charge density (1011), low interface state density (1011) and high breakdown field strength (106 V / cm). The invention has for its object to provide an uncomplicated method for the production of oxide bilayers of high mechanical and electrophysical properties (comparable to thermal gate oxide quality) on semiconductor or metal substrates based on vacuum-free low-temperature processes. According to the invention, this object is achieved by covering the metal or semiconductor substrate with an anodic oxide layer whose thickness is sufficient so that charge carriers no longer tunnel through it. Thereafter, a metal or semiconductor layer is deposited on the oxide layer and then completely anodized in the electrolyte, wherein the power supply for the anodization of the deposited metal or semiconductor layer through the oxide layer is carried out and the required current density is as high as in the oxide at the dielectric breakdown is observed.

Description

Field of application of the invention

The invention relates to a low-temperature oxidation process for producing an oxide double layer on metal or semiconductor substrates, which can serve as corrosion protection, diffusion barrier against diffusing ions, as a dielectric in capacitors and as a passivation layer in electronic components.

Characteristic of the known technical solutions

The production of Al ₂ O ₃ layers z is known. B. on oxide-covered Si substrates by chemical vapor deposition or by plasma anodization thin, vapor-deposited Al films.

Both the CVD method and the plasma anodization require considerable vacuum equipment and precise control of the gas components for the production of insulating layers (A. Saad and IGSwanson, Thin Solid Films 61 [1979] 355), in particular due to the high-temperature processes, the electrophysical Quality of the achievable layers does not correspond to the requirements resulting from the intended use.

Al ₂ O ₃ / SiO ₂ layers can also be prepared by overanodization of ΑΙ-coated Si layers (Zs Nenyli, Metalloberfläche 31 [1977] 3). However, it comes either during the anodization to the formation of holes in Al ₂ O ₃ as a result of dielectric breakthroughs and flaking of Al ₂ O ₃ layers or Al islanding at the interface Si / Al ₂ O ₃ , if the anodization not long enough he follows. The quality of the layers produced is insufficient for the described purpose. ·

Object of the invention

The object of the invention is the production of adherent oxide bilayers on a metal or semiconductor substrate with a low mobile ion density (<10 ¹¹ ), low solid oxide charge density (<10 ¹¹ ), low interface state density KIO ¹¹ ), and high breakdown field strength (> 10 ⁶ V / cm).

Explanation of the essence of the invention

The invention has for its object to provide an uncomplicated method for the production of oxide double layers of high mechanical and electrophysical quality (comparable to thermal gate oxide quality), on semiconductor or metal substrates based on vacuum-free low-temperature processes.

According to the invention, this object is achieved in that the metal or semiconductor substrate is covered with an anodic oxide layer whose thickness is sufficient to be no longer durchtunnelt of charge carriers.

Thereafter, a metal or semiconductor layer is deposited on the oxide layer and then completely anodized in the electrolyte, wherein the power supply for the anodization of the deposited metal or semiconductor layer through the oxide layer is carried out and the required current density is as high as in the oxide at the dielectric breakdown observed

It is very advantageous in this connection to sputter off a small part of the oxide layer thickness on the metal or semiconductor substrate before the deposition of the metal or semiconductor layer, because this can reduce the surface contamination and thus result in a further improvement of the electrophysical properties.

In addition, sputtering on the metal or semiconductor substrate layer results in increased adhesion to the substrate over vapor deposited layers.

embodiment

An Si sample (η-Si <100>, 4 ohm cm) is prepared by anodic oxidation in a 0.04 molar KNO ₃ solution in ethylene glycol containing 0.35 % by volume H ₂ O with a 17, Covered 5 nm thick oxide layer, then cleaned with deionized 'water and annealed at 400 ⁰ C for 20min in N2 stream. This is followed by the deposition of a 50 nm thick Al layer. It is particularly advantageous to sputter from the oxide layer before the coating 5 nm with a 0.6 keV Ar ⁺ beam and then aufzusputtern in the same apparatus, the Al layer.

This sample is anodized in a 10% solution of NH ₄ B ₅ OeIn ethylene glycol at a current density of 0.25mA / cm ² , wherein the power supply via a metal stamp to Si and over the oxide to Al takes place. In this case, the cell voltage initially increases in proportion to the anodization time (2V in 30 s), as long as the Al layer has not yet been completely converted into aluminum oxide.

The end of Al-anodization is revealed by a sudden increase in cell voltage (45V within 30s). Thereafter, the sample is cleaned with deionized H ₂ O, annealed at 500 ⁰ C for 20min in N ₂ stream and evaporated with An-Dots. RF CV measurements result in a Oxidladungsdichte <10 ^1l cm ~ ² and a density <10 ¹¹ ev ~ ¹ cm ~ ² only. The density of the mobile ion charges is 2 10 ¹⁰ cm " ² , the breakdown field strength 8 10 ⁶ V / cm.

Claims (2)

1. A process for producing an oxide double layer on HL or metal substrates on the surface of a metal I or semiconductor film deposited and this is oxidized anodically, characterized in that the substrate surface is anodically oxidized by their coating to such a layer thickness, that of the charge carriers can not be tunneled through, then the coating is carried out and the anodization of this film by means of power supply to the substrate via the oxide layer, wherein the current density is set at least as high as occurs in the oxide at the dielectric breakthrough. 2. The method according to item 1, characterized in that the deposition of the metal film is carried out by sputtering after a small portion of the oxide layer formed was sputtered.