Dielectric cure for reducing oxygen vacancies

Details Dielectric cure for reducing oxygen vacancies Dielectric cure for reducing oxygen vacancies

2000-03-10

2003-07-08

Smith, Matthew (Department: 2825)

Semiconductor device manufacturing: process

Making field effect device having pair of active regions...

Having insulated gate

C438S221000, C438S296000, C438S402000, C438S771000, C257S068000

Reexamination Certificate

active

06589839

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates generally to integrated circuits. In particular, the invention relates to dielectrics with reduced oxygen vacancies and methods of providing the same.
BACKGROUND OF THE INVENTION
Manufacturers of integrated circuits are continually increasing circuit density in pursuit of faster processing speeds and lower power consumption. As the packing density of memory cells continues to increase, components such as capacitors must still maintain a certain minimum charge storage to ensure reliable operation of the memory cell. It is thus increasingly important that capacitors achieve a high stored charge per footprint or unit of chip area occupied.
Several techniques increase the total charge capacity of the cell capacitor without significantly affecting the chip area occupied by the cell. One technique is to use dielectric materials having higher dielectric constants (k). Such materials include tantalum pentoxide (Ta
2
O
5
), barium strontium titanate (BST), strontium titanate (ST), barium titanate (BT), lead zirconium titanate (PZT), and strontium bismuth tantalate (SBT). Using such materials enables the creation of much smaller and simpler capacitor structures for a given stored charge requirement, enabling the packing density dictated by future circuit design.
Manufacturers, however, have encountered difficulties in incorporating these materials into the fabrication process because materials with higher dielectric constants often develop defects associated with oxygen vacancies (missing oxygen atoms in the crystal lattice). For example, when depositing barium strontium titanate, the barium strontium titanate can have missing oxygen atoms that may deform its crystalline structure and yield poor dielectric properties.
To reduce the oxygen vacancies, manufacturers often subject dielectric materials to re-oxidation anneals after their depositions. Conventional re-oxidation anneals typically heat the integrated circuit in an oxidizing environment. Ordinarily, such a process is highly oxidizing and can thus degrade other substances in the integrated circuit. For example, a re-oxidation anneal can degrade materials used in capacitor plates, electrodes, conductive plugs, the silicon substrate and the like. Such degradation can reduce the reliability of these electrical elements, and has been viewed as a significant obstacle to incorporating high dielectric materials into integrated circuits. Indeed, in some instances, manufacturers have added protective barrier layers to reduce the degradation thereby further increasing costs and fabrication complexity. Such protective barrier layers may exist, for example, between a bottom electrode material and a polysilicon plug.
SUMMARY OF THE INVENTION
A unique electrochemical process fills oxygen vacancies in dielectrics while reducing oxidation of nearby electrodes and conductors. For example, in one embodiment, an electromagnetic field moves oxygen vacancies to the surface of a dielectric film. Annihilation of oxygen vacancies can then be realized by an oxidizing treatment while the electromagnetic field continues to be applied. That is, the oxygen treatment removes the oxygen vacancies as the electromagnetic field directs the oxygen vacancy towards the surface of the dielectric film. The oxygen treatment can include ozone (O
3
), nitrous oxide (N
2
O), oxygen (O
2
), or the like.
In one embodiment, a unique plasma treatment provides the oxygen ions that react with the oxygen vacancies. In another embodiment, a unique electrolysis treatment provides the oxygen ions that react with the oxygen vacancies.
Another embodiment of the invention relates to a method of reducing oxygen vacancies in a high dielectric constant capacitor. The method comprises depositing a first electrode on a semiconductor substrate and depositing a high constant dielectric above the first electrode. The high constant dielectric has a plurality of oxygen vacancies therein. The method further comprises applying an electrical bias to the high constant dielectric wherein the appropriate polarity of the electrical bias causes the oxygen vacancies to migrate towards the surface of the high constant dielectric. The method further comprises plasma treating the high constant dielectric with a plurality of oxygen ions at a temperature below 500° Celsius (C.) wherein the oxygen ions fill at least a portion of the oxygen vacancies from the high constant dielectric.
An additional embodiment of the invention relates to a method of reducing oxygen vacancies in a dielectric. The method comprises applying an electromagnetic field to a dielectric to cause oxygen vacancies in the dielectric to migrate towards the surface of the dielectric and plasma treating the dielectric with oxygen ions which react with at least a portion of the oxygen vacancies in the dielectric.
Yet another embodiment of the invention relates to a method of reducing oxygen vacancies in a memory cell. The method comprises depositing a first electrode over a portion of a poly plug and depositing a dielectric over the first electrode. The dielectric has a plurality of oxygen vacancies therein. The method further comprises applying an electromagnetic field that causes the oxygen vacancies in the dielectric to migrate. The method further comprises plasma treating the dielectric with a plurality of oxygen ions wherein at least a portion of the oxygen ions react with the oxygen vacancies in the dielectric. The method further comprises depositing a second electrode over at least a portion of the dielectric.
One embodiment relates to a method of reducing oxygen vacancies in a metal-insulator-metal structure. The method comprises depositing a first metal electrode over a substrate and depositing a dielectric over the first metal electrode. The dielectric has a plurality of oxygen vacancies therein. The method further comprises applying an electromagnetic field that causes the oxygen vacancies in the dielectric to migrate and plasma treating the dielectric with a plurality of oxygen ions wherein at least a portion of oxygen ions fill oxygen vacancies in the dielectric. The method further comprises depositing a second metal electrode over the dielectric.
Another embodiment relates to a method of reducing oxygen vacancies in a dielectric on a semiconductor surface. The method comprises depositing on a semiconductor substrate, a high constant dielectric. The high constant dielectric has a plurality of oxygen vacancies therein. The method further comprises applying an electromagnetic field to the dielectric wherein the electromagnetic field causes the oxygen vacancies in the high constant dielectric to migrate towards the surface of the high constant dielectric. The method further comprising applying an electrolytic solution to the high constant dielectric wherein the electrolytic solution comprises at least a portion of oxygen ions that react with the oxygen vacancies to thereby fill a portion of the oxygen vacancies from the high constant dielectric.
An additional embodiment relates to a method of reducing oxygen vacancies in a dielectric. The method comprises applying an electromagnetic field to a dielectric to cause oxygen vacancies in the dielectric to migrate towards the surface of the dielectric and applying an electrolytic solution to the dielectric wherein oxygen ions in the electrolytic solution react with at least a portion of the oxygen vacancies in the dielectric.
Yet another embodiment relates to a method of reducing oxygen vacancies in a memory cell. The method comprises depositing a first electrode over a portion of a semiconductor transistor structure and depositing a dielectric over the first electrode. The dielectric has a plurality of oxygen vacancies therein. The method further comprises applying an electromagnetic field that causes the oxygen vacancies in the dielectric to migrate and subjecting the dielectric to electrolysis wherein oxygen ions react with the oxygen vacancies in the dielectric. The method further comprises depositing a second electrode over the diel

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