Semiconductor device manufacturing: process – Making field effect device having pair of active regions... – Having insulated gate
Reexamination Certificate
2001-08-24
2003-11-18
Le, Dung A (Department: 2818)
Semiconductor device manufacturing: process
Making field effect device having pair of active regions...
Having insulated gate
C438S396000, C438S003000, C438S240000, C438S241000, C438S250000, C257S295000
Reexamination Certificate
active
06649468
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to a method for fabricating a microelectronic component, in which a storage capacitor is formed on a substrate. A barrier, which affords protection against the passage of hydrogen is formed on the storage capacitor. The invention furthermore relates to a microelectronic component of this type.
Conventional microelectronic semiconductor memory components (DRAMs) essentially include a selection or switching transistor and a storage capacitor in which a dielectric material is inserted between two capacitor plates. Oxide or nitride layers having a relative permittivity of at most about are usually mostly used as a dielectric. In order to reduce the size of the storage capacitor and in order to fabricate non-volatile memories, “novel” capacitor materials (ferroelectrics or paraelectrics) with significantly higher relative permitivities are required. Examples of such materials are mentioned in the publication “Neue Dielektrika für Gbit-Speicherchips” [New dielectrics for Gbit memory chips] by W. Hönlein, Phys. Bl. 55 (1999). In order to fabricate ferroelectric capacitors for use in non-volatile semiconductor memory components having a high integration density, it is possible to use e.g. ferroelectric materials, such as SrBi
2
(Ta,Nb)
2
O
9
(SBT or SBTN), Pb(Zr,Ti)O
3
(PZT), or Bi
4
Ti
3
C
12
(BTO) as a dielectric between the capacitor plates. However, it is also possible to use a paraelectric material, such as (Ba,Sr)TiO
3
(BST), for example.
However, the use of these novel dielectrics presents the semiconductor process technology with new challenges. This is because, firstly, these novel materials can no longer be combined with polycrystalline silicon, the traditional electrode material. Therefore, it is necessary to use inert electrode materials such as, for example, platinum-group metals or their conductive oxides (e.g. RuO
2
). The reason for this is that after the deposition of the ferroelectric, the latter has to be subjected to heat treatment (“conditioned”) if appropriate a number of times in an oxygen-containing atmosphere at temperatures of about 550-800° C. In order to avoid undesirable chemical reactions between the ferroelectric and the electrodes, the latter are therefore mainly produced from platinum or another sufficiently thermostable and inert material, such as another platinum-group metal (Pd, Ir, Rh, Ru, Os).
For the integration of the storage capacitors, process steps are performed which take place in a hydrogen-containing environment. Thus, by way of example, the conditioning of the metallization and of the transistors requires a heat treatment in forming gas, which has a composition of 95% nitrogen (N
2
) and 5% hydrogen (H
2
). The penetration of hydrogen into the processed storage capacitor, i.e. into the dielectric, can, however, lead to degradation of the oxidic ceramics of the dielectric as a result of reduction reactions. Furthermore, the plasma-enhanced deposition (PECVD) of intermetal oxides or of the silicon nitride passivation layer can, on account of the high hydrogen content in the layers, cause reduction of the ferroelectric or paraelectric material of the dielectric. Hydrogen also appears during the deposition of electrically conductive materials, for instance refractory metals such as tungsten or titanium. The deposition serves, for example, to produce layers or to fill contact holes.
Furthermore, the penetration of hydrogen into the storage capacitor also adversely affects the structural properties. Thus, a peeling effect, for example, can occur.
It is already known to apply a silicon nitride layer to the storage capacitor as a barrier against the penetration of hydrogen. Silicon nitride is deposited, for example, according to the LPCVD (Low Pressure Chemical Vapor Deposition) process at about 750° C. The starting materials in the formation of silicon nitride are SiH
2
Cl
2
and NH
3
. During the deposition, however, hydrogen radicals are formed and the storage capacitor is thus damaged.
Furthermore, it is known to form hydrogen barriers made of materials, which can be deposited without hydrogen being present. Examples of such materials are AlO
x
, TiO
x
, TiO
x
N
y
. However, these oxidic materials are difficult to etch, with the result that, after the customary silicon oxide layer has been applied to the barrier, contact holes to the electrodes of the storage capacitors and/or through the barrier to the substrate material can be etched only in conjunction with a high outlay.
It has also already been proposed to omit the filling of contact holes with tungsten, which is done in the presence of hydrogen, and to use aluminum instead. Contemporary commercially available products with ferroelectric dielectrics are therefore embodied with aluminum as metallization material. However, a region to be filled can be filled significantly more reliably with tungsten than with aluminum. In any event, contemporary known methods for filling with aluminum must be dispensed with in the course of further miniaturization and further increasing of the storage densities of semiconductor memories.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a microelectronic component and a method of producing a microelectronic component which overcome the above-mentioned disadvantages of the heretofore-known methods and components of this general type and which allow contact holes to be etched in a simple manner after the application of an effective hydrogen barrier. At the same time, there should not be any considerable damage to the storage capacitor as a result of the application of the hydrogen barrier.
With the foregoing and other objects in view there is provided, in accordance with the invention, a method for fabricating a microelectronic component, the method includes the steps of:
forming a storage capacitor on a substrate by providing a first electrode and a second electrode and by providing a dielectric selected from the group consisting of a ferroelectric dielectric and a paraelectric dielectric disposed between the first electrode and the second electrode; and
forming a barrier by producing a silicon oxide layer on the storage capacitor, by subjecting the storage capacitor and at least part of the silicon oxide layer to a heat treatment, and by applying a barrier layer on the silicon oxide layer for protecting against a passage of hydrogen through the barrier.
An essential concept in the method according to the invention is that, during the barrier formation, firstly a silicon oxide layer is produced. The storage capacitor and at least part of the silicon oxide layer are subjected to heat treatment, i.e. are thermally treated in particular immediately after the deposition of the silicon oxide layer. By way of example, the storage capacitor and the silicon oxide layer are baked at a temperature of 500° C. or higher, preferably 650° C. or higher, in an oxygen atmosphere.
A barrier layer, which affords protection against the passage of hydrogen is applied to the heat-treated silicon oxide layer.
In particular if the electrodes of the storage capacitor contain platinum or a platinum-group metal, the silicon oxide layer takes from the platinum or platinum-group metal the catalytic activity, i.e. drastically reduces or substantially eliminates the catalytic activity, which, in the presence of hydrogen, can lead to particularly severe damage to the storage capacitor. Therefore, subsequent process steps in which hydrogen is present lead only to slight or even no damage to the storage capacitor. Therefore, the silicon oxide layer is preferably applied directly to the electrode material.
The heat treatment or the baking of the storage capacitor and at least part of the silicon oxide layer has the effect that hydrogen which, during the application of the silicon oxide layer, has penetrated into the vicinity of the storage capacitor or has penetrated into the latter is removed again. The heat treatment advantageously takes place in an oxygen-containing atmos
Gabric Zvonimir
Hartner Walter
Schindler Günther
Greenberg Laurence A.
Infineon - Technologies AG
Le Dung A
Locher Ralph E.
Stemer Werner H.
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