DD145348A1 - PROCESS FOR REACTIVELY ION-AMBER CARTRIDGE OF SILICON AND SILICON COMPOUNDS - Google Patents

Abstract

The invention relates to a method for the reactive ion beam etching of silicon and its compounds, wherein parts of the surface can be covered by masks. The goal was to reduce the etch time and increase the selectivity to mask and support materials. The etching takes place with a beam of ions or their neutralization products which react reactively with the silicon or the silicic acid compound. The ions are generated from fluorocarbons or from their mixtures with oxygen or inert gases. The particle energy is chosen so that the chemical etch rate significantly exceeds the sputtering rate. The process is compatible with other high vacuum process steps »

Description

A-

Inventor: Dr. Helmstreit, Wilfried dr. Bigl, Frieder

Process for the reactive ion etching of silicon and

Silicon compounds

App endungs area o f the invention

The invention relates to a method for the reactive ion beam of silicon and its compounds, wherein parts of the surface hit by the beam can be covered by suitable masks. The material to be etched may be compact material or layers on suitable substrates. The main field of application of the invention is the semi-ferritic component technique

Characteristic of the known technical solutions

Ion beam etching is carried out both for the large-area removal of layers of silicon or silicon compounds (eg for surface cleaning processes) and for the structuring of such layers using masks with beams of inert gas ions (mostly argon ions) or inert gas atoms.

The main disadvantages of the process are the low etching rates for the materials mentioned and the low selectivities with respect to masking materials and support materials. These properties cause low productivity of the etching processes mentioned above and lead to large structural widening in structuring processes (in particular) -

-2-1S4ill

particularly undesirable in the production of / um and SuTd / Um structures) *

To mitigate these disadvantages has been proposed (DE-OS 2,258,297) to use for the etching mask a metal (titanium), which has a low dependence of the sputtering rate (sputtering rate) of the direction of incidence of the ions, so that by oblique ion injection reaches an increase in selectivity can be. In addition, it has been proposed to achieve a reduction of the sputtering rate (sputtering rate) of the mask and thus likewise an increase in the selectivity of silisium / mask or silicon compound / mask by adding a reactive gas (oxygen or CuV) into the ambient atmosphere. Another proposal (DE-OS 2,536,718) provides for the reduction of structural broadening the use of a mask consisting of layers of different material with different sputtering rate (metal-organic material or metal-metal), wherein the layer with the larger sputtering rate on the side of the mask facing the surface of the plague «

A disadvantage of the proposed solutions is the use of metals for the etching mask, since their production is more complicated than the application of organic paints. The strong dependence of the removal rate on the direction of incidence of the ions also necessitates complicated technical systems for setting the angle of incidence.

Object of the invention

The aim of the invention is to reduce _s during ion beam etching of silicon and silicon compounds, the etching time for a given layer thickness considerably and to increase the selectivity substantially opposite mask and carrier materials "Furthermore, the method should compatible respectively with previous * subsequent high vacuum process steps his

Explanation of the nature of the invention

The object of the invention is a method for the reactive ion beam etching of silicon and silicon compounds, in which the etching rate for silicon or silicon compounds is selectively greatly increased.

The method according to the invention for the reactive ion beam etching of silicon and silicon compounds is characterized in that the etching is carried out with a jet of ions or their neutralization products which react reactively with the silicon, in particular polysilicon, or with the silicon compound. The silicon compounds are in particular to silica and Siliziuimaitrid, in pure form, in the form of layer sequences or in admixture with other compounds, for. B. be used as passivation layers in the albleitertechnik *

The ions required for reactive ion beam etching are extracted from the ion source in an ion source of plurified hydrocarbons, in particular CF.sub.F, CF.sub.2, CF.sub.2H, or mixtures of such hydrocarbons or their mixtures with oxygen or inert gases, if required neutralized and directed to the material to be etched «The pressure in the etching chamber is below 10 Pa; the particle current density can be varied within wide limits (current densities z _e B. between OjOp and 1.5 mA / cm) «

An essential parameter of the method according to the invention is the Tellehenenergle * At low energies (i.a. 0.5 to 1j5 keVy depending on the Iviaterial to be etched and the reactive particles used), the reactive portion greatly outweighs the sputtering portion, so that a high etch rate and a high selectivity with respect to etching masks (eg organic photo-, electron beam or X-ray resists) or support materials (eg Si, GaAs o * ä ») can be achieved" Due to this increase in selectivity and the fact that the Abtragsgeschwincingkeit reactive ion beam etching independent of. On-*

If the angles of the particles are, then organic resists for ion beam structuring processes can also be used, if high transfer accuracy of the structures is required (structure sizes inyuin- and sub- / um-range). The elaborate production of multi-layer masks or metal intermediate masks can be dispensed with ·

If the particle energy is increased, the proportion of material removal by sputtering increases, so that the selectivity is reduced while the etching rate is maintained or increased, and the influence of the particle incidence direction on the etching process increases. By appropriate choice Consequently, the ratio of sputtering rate to chemical Ätzgesohwindigkeit can be varied within wide limits of the particle energy in the inventive method and thus z. B ₉ the edge steepness of the generated structures are changed ·

At constant ion energy, a variation of the proportion of reactive etching / sputtering shares is also possible by changing the etching gas composition. In this Pail, however, increasing the sputtering rate (at constant particle current density) means a decrease in the total etch rate.

embodiment

1. In a silicon dioxide layer (thickness 300 nm), which is located on a silicon substrate, a certain structure should be etched. For this purpose, a layer of photosensitive lacquer is first applied, exposed and developed. The etching is carried out with an ion beam, which results from ionization of CF-H in an ion source. The resulting ions CS ^ H *, ClP ⁺ and CI ^ ⁺ react selectively with the silicon dioxide at the sites not covered by the etching mask. "The energy of the ionon is in the range of 1 keY, the current density is 0.25 mA / cm. The etching is finished after 3 minutes

2. On a substrate of GaAsP is a "jl ^ _a ". Layer (thickness 300 microns), in which a given pattern is to be etched. The entire layer is "exposed" covered with an electron-beam-sensitive resist (thickness 300 nm) and with an electron · Each developing is carried out with an ion beam, etching, which is produced by ionization of CP ^ OJ ¹ in an ion source, ions generated which selectively react with the Si ^ H while the paint and the substrate are not attacked. The energy of the ions is

1.5 keV, the current density 0.25 mA / cm _β The treatment with the ion beam takes 4 minutes «

Claims (5)

invention claim A method for the reactive ion beam etching of silicon and silicon compounds, characterized in that the etching is carried out with a beam of ions or their neutralization products which react reactively with the silicon or the silicon compounds. Method according to item 1, characterized in that the non-corrosive materials were polysilicon, silicon dioxide or silicon nitride 3. The method according to item 1, characterized in that ions or neutral particles are used which arise from the gases CP-Oi ¹ , CP, CP ^ H, their mixtures or mixtures with oxygen or inert gases. 4 · Method according to items 1 and 3, characterized in that the particle energy is chosen so that the ohmic etching rate significantly exceeds the sputtering rate (sputtering rate). 5 «method according to item 1 and 3, characterized in that for influencing the edge steepness of the structures produced the particle energy or the gas composition is chosen so that in addition to the reactive loneiistrahlätzen still a Zerstäubungsanteil (sputtering) occurs«