DD298975A5 - PROCESS FOR PRODUCING DEEP GRAVES IN A CRYSTALLINE SILICON SUBSTRATE - Google Patents

Abstract

The invention relates to a method for producing deep trenches in a monocrystalline silicon substrate for the production of isolation regions or capacitor arrangements in the production of microelectronic semiconductor devices in VLSI technology. The process according to the invention is characterized in that, after forming an AEtz mask, a pretreatment of the substrate surface by a reactive ion etching process is carried out at a pressure of * Pa with a reaction mixture of trifluoromethane with oxygen content and then the deep trenches by a reactive ion etching process at a pressure of * Pa with a reaction gas mixture consisting of chlorine, boron chloride and silicon tetrachloride. {Dig; Isolation region; Capacitor arrangement; Ionenaetzprozesz; Reaction gas mixture; Boron; boron chloride; Silicon tetrachloride}

Description

Field of application of the invention,

The invention relates to a method for producing deep trenches in an oinkristallinon silicon substrate for the preparation of isolation regions or capacitor arrangements in the production of microelectronic Halbloiteranordnungon in VLSI technology.

Characteristic of the known state of the art

In order to produce the deep trenches necessary in the fabrication of highly intrinsic semiconductor devices for isolation regions or capacitor arrays in an o-crystalline silicon substrate, a large number of anisotropic dry etching processes are known.

Thus, it is known to produce an anisotropic dry etching with a reaction gas mixture of fluorine- or bromine-containing gases and an addition of a passivating gas, for example BCl, SiCu or CCl ₄ , after producing an etching mask (Hardmasko) usually consisting of silicon dioxide and / or silicon nitride (cf. EP-PS 200951, US-PS 4589952, EP-PS 272143).

These etching processes are negatively characterized by a low selectivity to the etch mask, which is less than or equal to 10.

Methods in which reactive ion etching is carried out to produce trenches in a reaction gas atmosphere consisting of trifluoromethane (cf., DE-PS 3613181) are disadvantageously characterized not only by low selectivity but also by a low etch rate.

EP-PS 101828 discloses an etching selectivity enhancing plasma etching process in which the anisotropic etching of the silicon substrate is carried out in a reaction gas mixture consisting essentially of boron chloride and bromine.

A disadvantage of this method is the relatively low etching rate.

G. K. Herb u. a. (Solid State Technology 30/1987/10, p. 109ff.) Describe a process for the formation of trenches, in which after formation of an etching mask, first the surface by a F-unification process with a consisting of boron chloride and Argon gleichTeilen Resorptionsgasgemisch, at a pressure of 2.7 Pa and a Überätzdauer of 5min is cleaned.

In this case, the oxide layers located on the silicon substrate are removed.

Subsequently, the deep trenches are introduced by a reactive ion etching with an etching gas mixture of chlorine, silicon tetrachloride and boron chloride or from chlorine, silicon tetrachloride, boron chloride and helium at a pressure of less than 5Pa in the monocrystalline silicon substrate. The occurring relatively low etching rate is approx.

82,5nmmin ~ '.

Furthermore, a method for the manufacture of a trench capacitor is known (DE-PS 3812621), in which the trenches are produced by an etching process with an etching gas mixture consisting of boron chloride and chlorine. A disadvantage of this method is the undercut etched profile produced thereby, which is compensated by complicated partial steps in the further production process of the trench capacitor.

The known methods make it impossible to produce deep trenches in monocrystalline silicon substrates, in particular in a single-disk system, with a high quality of the generated trench structure and high productivity and reproducibility.

Object of the invention

The aim of the invention is to provide a method for producing deep trenches in a monocrystalline silicon substrate, which guarantees a good quality of the trench structure produced and ensures high productivity and reproducibility.

-2- 298 Presentation of the essence of the invention

The invention is based on the object of specifying a method for forming an inorganic silicon substrate in which undercut etching profiles are avoided, a high silicon etching rate is ensured and an etching selectivity of the crystalline silicon substrate to the etching mask of magnitude 12 is possible.

According to the invention, the object is achieved by forming, after formation of an etching mask for cleaning the silicon substrate surface, a pretreatment by electron-etching process at a pressure of 3 to 8 Pa and an energy density of 3 to 4 W cm ^-1 with an inert gas mixture of trifluoromethane with 5 ... 20% Sauerstoffantoil and then oin reactive Iononätzprozoß without interruption with a Reaktionsgasgomisch from chlorine with a share of 2 ... 10% Borohlorid and oinom Antoll of 10 ... 30% Sillziumtotrachloridbo! is carried out at a pressure of 8 ... 15 Pa and a power density of 1 ... 1.5W cm ^"2 for generating the tlofon Qrttbon. In one embodiment dos orfindungsgemäßen method dom Ronklionsgasgomisch is a noble gas, in particular helium for Grabenätzon, zugesotzt as a diluent gas The proportion of diluting gas in the mixture of roughening gas is 2 to 10% .The silicon substrate is introduced into a single-rotor disk system, in particular a ninon single-disk diode reactor, for pretreatment and subsequent generation of deep trenches.

Ausführungsbelsplel The method according to the invention will be explained in more detail below with reference to an exemplary embodiment.

If an oycrystalline silicon substrate (wafer) with a diameter of 125 mm is applied, a thermal O.layer approximately 40 nm thick is applied. Subsequently, by an LP-CVD process oino silicon nitride layer with oinor thickness of 40 ... 150nm and aoca. Deposited 600ηm thick silicon dioxide layer.

After the subsequent application of a photoresist mask, the silicon dioxide and silicon nitride layers are patterned, the photoresist mask is removed, and a fine cleaning process is performed. Subsequent to this etching mask (hard mask) generation, the silicon substrate is introduced into the reaction space of a single-plate diode reactor. In order to clean the silicon substrate surface, in particular to remove the residual silicon dioxide layers, a pretreatment is then carried out at a pressure of 5 Pa and a power density of 4 W cm -1. The reactive gas stream of this reactive ion etching process is composed of 60 sccm of trifluoromethane and oxygen of oxygen Interruption in the same reaction space produces the deep gravel, in which at a pressure of 10Pa and a power density of 1.25W cm ' ¹ oin reactive Iononätzprozoß with a reaction gas stream, which is composed of 20 seem of chlorine, 1 sccm boron chloride and 6 sccm silicon tetrachloride is performed ,

The inventive method is characterized by the good quality of the orzougten trenches and high productivity and reproducibility.

Claims (3)

1. A method for producing deep trenches in a single-crystal silicon substrate, in which after forming an etching mask for cleaning the substrate surface is carried out a pretreatment and then the deep trenches are produced by a reactive Lonenätzprozeß with a boron trichloride and chlorine-containing reaction gas mixture, characterized in that the pretreatment the substrate surface by a reactive ion etching process at a pressure of 3 .. .8 Pa and a power density of 3 ... 4 Wem " ² with a reaction mixture of trifluoromethane 5-20% oxygen content performed and the subsequent reactive Iononätzprozeß for generating the deep Trenching without interruption with a reaction gas mixture of chlorine in a proportion of 2 ... 10% boron chloride and a proportion of 10 ... 30% silicon tetrachloride at a pressure of 8 ... 15Pa and a power density of 1 ... 1.5Wc (TT ^{2 are} executed. 2. The method according to claim 1, characterized in that the reaction gas mixture for generating deep trenches contains a noble gas as a diluent gas with a proportion of 2 ... 10%. 3. The method according to claim 2, characterized in that the reaction gas mixture for generating deep trenches contains helium as a diluent gas.