Semiconductor device manufacturing: process – Having magnetic or ferroelectric component
Reexamination Certificate
2001-02-26
2001-11-13
Tsai, Jey (Department: 2812)
Semiconductor device manufacturing: process
Having magnetic or ferroelectric component
C438S238000, C438S253000, C438S776000, C438S627000
Reexamination Certificate
active
06316275
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to a method for fabricating a semiconductor component having a first oxide layer above a substrate and a capacitor formed above the first oxide layer, in which the capacitor has a metal-oxide-containing capacitor material layer deposited between a bottom electrode and a top electrode.
Conventional microelectronic semiconductor memory components for example, Dynamic Random Access Memories (DRAMs) essentially include a switching transistor and a storage capacitor. In this case, the stored information is represented by the charge state of the storage capacitor. Because of discharge processes, the charge state of a (volatile) DRAM memory cell must be continually renewed.
Oxide or nitride layers having a dielectric constant of at most about 8 are usually used as capacitor dielectrics in DRAMs. In order to reduce the size of the storage capacitor and in order to fabricate non volatile memories, “novel”, metal-oxide-containing capacitor materials (paraelectrics or ferroelectrics) with significantly higher dielectric constants are required. Known examples of ferroelectric capacitor materials are SrBi
2
(Ta,Nb)
2
O
9
(SBT or SBTN), Pb (Zr,Ti)O
3
(PZT), Bi
4
Ti
3
O
12
(BTO), and a known example of a paraelectric high-epsilon capacitor material is (Ba,Sr)TiO
3
(BST).
The use of these novel capacitor materials poses technological difficulties. First, 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 (Pt) or conductive metal oxides (e.g. RuO
2
). The reason for this is that, after deposition, the novel capacitor materials have to be thermally treated (“conditioned”), if appropriate, a number of times in an oxygen-containing atmosphere at temperatures of about 550-800° C., and only the aforementioned inert electrode materials have a sufficient thermostability to avoid an undesirable chemical reaction between the electrode material and the capacitor material.
A further difficulty in the fabrication of such storage capacitors stems from the fact that metal-oxide-containing capacitor materials generally have a high sensitivity to hydrogen. However, after the formation of the storage capacitor, it is necessary to carry out process steps which take place in a hydrogen-containing environment. The disadvantage here is that the Pt electrodes are permeable to hydrogen and do not, therefore, form effective protection against hydrogen damage to the capacitor material.
In principle, there are various possibilities for solving the last-mentioned problem. From the standpoint of materials technology, attempts can be made to find an electrode material which is not permeable to hydrogen, or to find a dielectric material which is not sensitive to hydrogen. In terms of method technology, attempts can be made to avoid, after the formation of the storage capacitor, any process steps which proceed in a hydrogen-containing environment. In all of these solution variants, however, further serious difficulties arise in practice.
In the prior art, attempts have already been made to solve the problem by depositing a hydrogen barrier layer on the storage capacitor. U.S. Pat. No. 5,523,595, which is believed to be the most relevant prior art, describes a method for fabricating a semiconductor component with a ferroelectric storage capacitor. After the construction of the storage capacitor, a hydrogen barrier layer including TiON is produced above the capacitor by a chemical vapor deposition (CVD) process. The barrier layer prevents the penetration of hydrogen through the top Pt electrode of the storage capacitor. The disadvantage, however, is that hydrogen can still penetrate through the bottom Pt electrode and hydrogen can still penetrate laterally into the ferroelectric. Therefore, complete protection of the capacitor ferroelectric against degradation by hydrogen is not given.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a method for fabricating a semiconductor component having a storage capacitor with a ferroelectric or paraelectric capacitor material which overcomes the above-mentioned disadvantageous of the prior art apparatus and methods of this general type. In particular, it is an object to provide a method for fabricating a semiconductor component in which the ferroelectric or paraelectric capacitor material of the storage capacitor is adequately protected against the penetration of hydrogen.
With the foregoing and other objects in view there is provided, in accordance with the invention a method for fabricating a semiconductor component, that includes: providing a substrate; producing a first oxide layer above the substrate; with a plasma doping method, doping the first oxide layer with a barrier substance to form a hydrogen diffusion barrier in the first oxide layer; subsequent to performing the plasma doping method, producing a capacitor above the first oxide layer; and producing the capacitor to include a bottom electrode, a top electrode, and a metal-oxide-containing capacitor material layer deposited between the bottom electrode and the top electrode.
With the foregoing and other objects in view there is also provided, in accordance with the invention a method for fabricating a semiconductor component, that includes: providing a substrate; producing a first insulation layer above the substrate; producing a capacitor above the first insulation layer; producing the capacitor to include a bottom electrode, a top electrode, and a metal-oxide-containing capacitor material layer deposited between the bottom electrode and the top electrode; producing an oxide layer above the capacitor; and with a plasma doping method, doping the oxide layer above the capacitor with a barrier substance to form a hydrogen diffusion barrier in the oxide layer.
An essential standpoint of the invention is that, in order to afford protection against the penetration of hydrogen into the capacitor material, an oxide layer is doped with a barrier substance. By virtue of the barrier substance atoms that are introduced into the oxide layer, the doped oxide layer is made impermeable to hydrogen to the greatest possible extent.
In this case, therefore, the term “doping” does not mean the introduction of impurity atoms in order to alter the conductivity (so-called p- or n-doping) but rather the introduction of impurity atoms in order to reduce the diffusibility of hydrogen (in an oxide layer).
According to a first aspect of the invention, a (first) doped oxide layer is formed below the capacitor. Another possibility consists in depositing a thin (second) oxide layer above the capacitor and doping it—at least in sections.
These two aspects of the invention can be combined with one another. In this case, one method variant is characterized in that the first doped oxide layer and the second doped oxide layer enclose the capacitor on all sides.
In accordance with an added feature of the invention, the barrier substance is preferably nitrogen. In this case, the doping results in nitriding of the first or second oxide layer. In general, however, it is also possible to use other suitable substances, e.g. noble gases, as the barrier substance.
In accordance with an additional feature of the invention, the doping (or nitriding) of the oxide layers is effected with the aid of a plasma discharge containing the barrier substance. The plasma discharge makes it possible for a sufficiently high barrier substance concentration to be produced in the first and/or second oxide layer in a short time (for instance 60 s), without exceeding a maximum substrate temperature in the range of 50-120° C. in the process. The plasma doping is therefore compatible with conventional photoresist masking techniques. Accordingly, an advantageous method sequence is characterized in that, prior to the plasma doping, a mask is applied on the first and/or second oxide layer, which mask is used to pattern the doping o
Greenberg Laurence A.
Infineon - Technologies AG
Lerner Herbert L.
Stemer Werner H.
Tsai Jey
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