DD212992A1 - METHOD AND DEVICE FOR PLASMACHEMICAL MULTI-STEP APPLICATION - Google Patents

Abstract

The solution according to the invention is suitable for multi-step etching by means of identical or different process gases, preferably of Al layers on electronic components. The aim of the invention is to reduce the pollution of the recipient and the toxic exhaust gases produced during the plasma process in the plasma-chemical multi-step etching. D. Invention is characterized in that the etching process takes place in a cycle of etching process steps, each with a stationary Aetzgasfuellung. The plasma zone is limited only in part in the recipient. The rest of the recipient's room is designed as a ballast volume. For the different stationary etching steps, which are carried out successively, the process gas composition, the pressure and the applied power are adapted to the materials and material volume to be etched.

Description

Method and apparatus for plaamachetnic More very it t-etching -

Field of application of the invention

The solution is suitable for erfindungsgetnäße Mehrsehritt-etching using the same or different process gases '· preferably of aluminum layers on electronic (' · devices.

, , Characteristic of the known technical solutions

^The plasma-chemical etching, for example, for patterning of microelectronic circuits has found an extraordinary proliferation in recent years, which is due to the over wet chemical processes improved pattern transfer. In connection with this, the number of process and device solutions secured by intellectual property rights has risen sharply, with the gas mixtures used, the design of the etch process and reactor design being the focus of intellectual property work. The variety of process and device variants is particularly easy to solve in a number of reviews -. (Reinberg: VISI Electron Microstructs Sei, (1981), 2, 1; E. Kay, J. Goburn, A. Dilks: Top Curr.Chem. (1980), 94, 1; CJ Iffogab: Conf. Ser. Inst. Phys. (1980), 53 »37). A characteristic feature of all previously known variants is the etching in a reactor system, which is traversed by the etching gas, usually halocarbon compounds. By choosing a suitable pressure and a suitable flow rate, a certain degree of decomposition of the reaction gas is achieved, which is intended to ensure a maximum in the concentration of atoms and radicals necessary for etching. This previously known and used method has two disadvantages.

First, within the reactor, in which the residence time of the gas at different locations is of different lengths, a spatially inhomogeneous degree of decomposition is produced, which can lead to inhomogeneities in the etching behavior at different locations in the reactor or above the disk. This problem is attempted by a ..geeignete arrangement of gas inlet and suction (Radial Flow Reactor UV S. 3,757,733), by separation of plasma space and reaction chamber (US 4,151,034) or by overflowing the plasma and Ätzraumes to solve (reactor TEGAL 702). ~

Secondly, in the course of reactor operation, decomposition products of the etching gas and reaction products of the etching process in the reactor and in the vacuum system are deposited or get into the pump and the exhaust air. Some of these products are highly toxic, others highly corrosive. The formation of these products naturally depends on the amount of deacidified etching gas. The occurring reactor pollution forces periodic cleaning and thus productivity reduction, the toxic exhaust gases make additional protection measures required. The contamination of the Rsaktore trying to suppress by optimizing the potential conditions in the reactor or by changing potentials (US 3,598,710), the pollution is usually relocated only in other parts of the vacuum system. The problem of contamination occurs particularly in the etching process of Al with CC1, since CCl. non-volatile decomposition products forms (eg, C ₂ Clg and glow polymer) and in the Al-etching process with AlCl 3, and Al-oxide chlorides also form nonvolatile reaction products. In particular, the Al etching process is complicated by the fact that first an AlpO - layer must be etched and formed in the course of the Al-etching process, a surface layer, which is to be eliminated as Restkontermination after through etching of the Al layer, with a high selectivity of the etching process must be ensured by AL over SiO_. These different demands on the etching regime occurring in time sequence of the etching process are in

Therefore, it is also proposed in US Pat. No. 4,256,534 to vary the power and the gas composition in the course of the etching processes beiapielaweiae. In order to achieve an exact etching of the individual layers, complex process control and regulating devices for the individual etching process steps with different process gases are required.

Object of the invention

The aim of the invention is to reduce the contamination of the recipient tube and the toxic exhaust gases produced during the plasma process during plasma-chemical multi-step etching. '

Explanation of the essence of the invention

The object of the invention is to specify a method and a device for plasma-chemical multi-layer etching, with which it is possible to achieve high etch rates with low etching gas consumption and low power density, in particular when etching aluminum layers on semiconductor substrates, and exact etching allow individual layers with the same or different process gases without complex process control and -regeleinrichtungen. The invention is characterized in that the etching process is carried out in a cycle of Ätzprozeßschritten each with a stationary Ätzgasfüllung in the recipient, wherein the plasma zone is formed only on a part of the recipient. The remaining volume of the recipient is designed as a ballast volume, from which the respective etching gas or etching gas mixture is supplied to the plasma zone during the course of the etching process that is carried out by a controllable diffusion barrier. Purely the different etching steps that are performed sequentially, the process gas composition, the pressure and the power used are adapted to the materials and material volumes to be etched. That for the respective etching process step

suitable etching gas or etching gas mixture is fed to the bailast volume of the recipient from individually switchable gas reservoirs in the respectively required quantity. Thus, a strongly reducing gas mixture is necessary for the Al ₂ O. etching process, which always represents the starting phase of the Al etching process. Such an etching medium provides CCl, but also excellent BCLo, SiCl. and PCI, -. The latter compounds are very aggressive and make the inventive application of a process step that requires a minimum of such compounds, particularly advantageous.

Purely the further etching sequence of the Al-etching is theoretically sufficient for Cl-1, since this is very reactive towards aluminum. For reasons of a most anisotropic Ätzangriffes, but also to remove oxide particles that are formed by reaction with HO and O ₂ - impurities, is a mixture of CCl. and Cl_ advantageous. Another possibility is the realization of a high degree of CCl.-decomposition, which leads to an increased Cl ₂ content in the etching gas plasma. This is possible, for example, by a lower CCl. pressure (P _CG1 ) and an increased _output (U), since the degree of decomposition is determined by the ratio q qqi ./^ . A reduced proportion of carbon in the reaction plasma also reduces the contamination of the surface during the etching process.

The last phase of the etching process is characterized by the requirement to ensure both contamination-free Si0 ₂ surfaces, insofar as this is present as a surface under the Al, as well as to guarantee the lowest possible SiO ₂ attack. Both requirements are also to be met with an increased Cl ₂ content in the reaction gas. In many cases, it is necessary to stabilize the Al structure against kach corrosion, for which purpose a stationary plasma containing Op is sufficient according to the invention.

The erfindungagemäße device is characterized in that the upper electrode plate is designed as Diffuaionabarriere, which divides the recipient into a Piaamazone and in a ballast volume, wherein the ballast volume are assigned a plurality of Ätzgasreservoire. According to the invention, the distance between the electrode plate and the recipient wall is between 0.5 mm and 3 mm. Daa Volume of the plasma zone to the ballast volume is divided by the diffusion barrier in the ratio of 1: 2 to Λ% 10. By virtue of the inventive multi-stage stationary injection with defined amounts of itzgas and etching gas, corresponding to the material and material volume to be etched, precise etching in the structuring of microelectronic components is possible without expensive process control and regulating devices. Due to the low Ätzgasver-. only slight contamination of the recipient and the environment (toxic gases) occur

Auafuhrungabeiapie1

The solution according to the invention will be explained in more detail in the following embodiment. For the sake of simplicity, the method according to the invention will be explained on the mode of operation of the device.

The drawing shows a basic arrangement of a device for carrying out the multi-step etching according to the invention.

In the recipient 1 are two electrode plates 2; 3 arranged. On the lower electrode plate 2, the substrate is arranged. The upper electrode plate 3 is formed as a diffusion barrier and divides the Rezip. ients 1 into a plasma zone 5 and in a ballast volume 9. The ballast volume 9 is assigned a plurality of etching gas reservoirs 4, which can be selectively switched on via valves 8. The valves are used to groove the gas reservoir. 4

The mode of operation of the device is as follows: after the substrate 6 "has been applied to the lower electrode plate 2, the recipient 1 is evacuated, then the required etching gas is introduced from one of the gas reservoirs 4 into the recipient 1 by opening one of the valves 8, after switching on HP voltage forms a plasma between the electrode plates 2 and 3 to a limited plasma zone 5 in the recipient 1. During the etching process diffuses from the ballast volume 9 according to the decomposition process in the plasma zone via the diffusion barrier 3 undecomposed etching gas in the plasma zone 5 after The gas fillings are dimensioned in the gas reservoir 4 of pressure and volume so that, after opening the respective valve 8 in the recipient 1 (in the plasma and ballast space), the optimum gas pressure for the respective etching step is established 1 evacuated, where a pressure of 10 * ~ ^J Torr has been found to be sufficient.

The method according to the invention in the case of multi-step etching of an Al layer with concrete parameters is described below. '"

The etching of a 4 ^f 'disk with 0.7 / μm thick Al layer, with a 40 cm ^ surface to be etched, was achieved with the following steps.

1st step: "Etching the Al ^ O ^ layer

Etching gas CCl. 0.3 torr

Ballast volume -4 dm

-2 r. f. power 0.2 W cm

Frequency 2 MHz etching time 10 s

2nd step: Al-etching.

Etching gas CCl. 0.3 Torr ballast volume 16 dm rf power 0.2? / Cm " ² frequency 2 HHz etching time 20 s

3 × step: etching the boundary layer Al / SiO 2,

Etching gas Cl ₀ 0.1 Torr Ballast volume 4 cLtrr r »f» power 0.2 W cm Frequency 2 MHz Etching time 10, s ·

-2

4 · Step:

Qp plasma stationary

Gas O ₀ 0.1 torr

3 ballast volume 4 cir

r · f. power 0.2 W cm 'frequency 2MHz treatment time 10 s

-2

Claims (5)

invention claim 1. A method for plasmachemischen'Mehrschritt etching using different etching gases or etching gas mixtures in a recipient, which has two spaced apart electrodes, characterized in that the etching process is carried out in a cycle of Ätzprozeßschritten each with a stationary Ätzgasfüllung in the recipient, wherein the Plasma zone is formed only on a part of the recipient and the remaining volume of the recipient is designed as a ballast volume from which is supplied through a controllable diffusion barrier, the respective etching gas or etching gas mixture during the ongoing Ätzprozeßschritt the plasma zone, and that the ballast volume suitable for the respective Ätzprozeßschritt , Etching gas or etching gas mixture is supplied in the required for the Ätzprozeßschritt amount of correspondingly individually switchable gas reservoirs. 2. The method according to item 1, characterized in that. Aluminum in several steps with single CCl. or CCl. /Inertgas- gas fillingöfiim in the recipient is etched so that a gas filling for etching the AIpO., - Layer, a gas filling for etching the Al is used, with pressure and power in the individual steps are adapted to the materials and material to be etched. 3. The method according to item 1 and 2, characterized in that different etching gases are used for the etching of aluminum for the individual steps, wherein the 'elimination of the AlpO ^ coating on Al layers a yl, SiCl or PCl_-containing gas mixture is used and for etching of Al Cl ₂ or CIp- containing gas mixture is used as the process gas and the conclusion of the Al-ltzprozesses an Op- or Og-containing gas mixture is used, 4 · Apparatus for plasma-chemical multi-step etching, consisting essentially of a provided with two spaced electrode plates recipient, wherein the electrode to be etched, substrate is mounted on an electrode plate, for carrying out the method according to item 1, characterized in that the upper Electrode plate (3) is designed as a diffusion barrier, which divides the Hezipienten (1) in a plasma zone (5) and in a ballast volume (9) and that the ballast volume (9) are assigned a plurality of Ätzgasreservoire (4). 5. Device according to item 4, characterized in that the distance of the electrode plate (3) to the recipient wall (1) is between 0.5 to 3 mm and the volume of the plasma zone (5) to the ballast volume (9) 1: 2 to 1 : 10. For this 1 page drawing