Methods for forming capacitors on semiconductor substrates

Details Methods for forming capacitors on semiconductor substrates Methods for forming capacitors on semiconductor substrates

2002-11-15

2004-10-19

Lebentritt, Michael (Department: 2824)

Semiconductor device manufacturing: process

Coating with electrically or thermally conductive material

To form ohmic contact to semiconductive material

C438S643000, C438S648000, C438S653000, C438S656000

Reexamination Certificate

active

06806183

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to apparatus and methods for forming films on substrates, and more particularly, to apparatus having multiple-chambers for forming thin films on semiconductor substrates and methods of using such apparatus to form capacitors on semiconductor substrates.
BACKGROUND OF THE INVENTION
As the device density on semiconductor substrates increases resulting in highly integrated semiconductor devices, it may be desirable to increase capacitance in a restricted cell area. Various methods have been proposed, for example, decreasing the thickness of the dielectric layer, increasing the effective surface areas of electrodes, and/or using dielectric layers having large dielectric constants such as ferroelectric materials. As used herein, dielectric layers having large dielectric constants including ferroelectric films are referred to as high dielectric layers.
A ferroelectric material such as PbZrTiO
3
(PZT) or BaSrTiO
3
(BST) may be used as the high dielectric layer. Unlike a silicon oxide layer, a silicon nitride layer, or a tantalum oxide layer, the ferroelectric material may exhibit a spontaneous polarization phenomenon. The ferroelectric material also typically has a dielectric constant between several hundreds and several thousands. Therefore, since the equivalent oxide thickness of the high dielectric layer is equal to or less than 10 Å even though the high dielectric layer is formed to a thickness of 500 Å, it may be possible to significantly increase capacitance when the high dielectric layer is used for a capacitor.
When a capacitor of a highly integrated semiconductor device is formed, the high dielectric layer such as BST or PZT preferably has a high dielectric constant and an excellent step coverage. The resulting capacitor preferably has an excellent leakage current characteristic. To achieve this, a metal organic chemical vapor deposition (MOCVD) method is typically used to form the high dielectric layer.
However, when the high dielectric layer such as the BST layer formed by the MOCVD method is applied to the capacitor, the high dielectric layer is typically formed at a high temperature of more than about than 500° C. in order to improve the leakage current characteristic of the capacitor. While the leakage current characteristic of the resulting capacitor may be good, the step coverage of a high dielectric layer formed at the high temperature may be less than about 50%, which is generally considered to be poor. When the step coverage of the high dielectric layer is poor, the high dielectric layer may not be suitable for use in a highly integrated semiconductor device, which has a distance between storage electrodes (the lower electrodes of the capacitor) that is relatively narrow. Also, when the high dielectric layer is formed at the high temperature of more than about 500° C., a barrier metal layer may be oxidized.
To solve the above problems, the high dielectric layer may be deposited at a low temperature of less than about 500° C. where the step coverage of the high dielectric layer is good. However, when the high dielectric layer is deposited at the low temperature, post-annealing may be required because the high dielectric layer is deposited as an amorphous layer having a dielectric constant of less than about 50. Additionally, the leakage current characteristic of the capacitor may deteriorate since impurities may remain in the dielectric layer. These impurities may be, for example, a carbon component generated from an organic metal source that is used as the raw material of the high dielectric layer.
In order to remove the impurities which may remain in the high dielectric layer, a method of crystallization annealing the high dielectric layer at a high temperature of greater than about 600° C. may be provided after depositing the high dielectric layer at the low temperature of less than about 500° C. However, when the high dielectric layer is crystallization annealed at the high temperature of greater than about 600° C., the electrode of the semiconductor device capacitor and the barrier metal layer may be oxidized and the high dielectric layer may deteriorate. Also, the remaining impurities may not be removed even though the high dielectric layer deposited at the low temperature of less than about 500° C. is crystallization annealed at the high temperature of more than about 600° C.
SUMMARY OF THE INVENTION
According to embodiments of the present invention, methods and apparatus for oxygen radical annealing or plasma annealing various layers (e.g., a lower electrode, a dielectric layer, or an upper electrode) of a microelectronic capacitor on a substrate are provided. By oxygen radical or plasma annealing the lower electrode of the capacitor, the leakage current characteristic of the capacitor may be improved such that the leakage current is reduced, for example, by a factor of 100 or more. The amount of impurities on the lower electrode may also be reduced. Oxygen radical or plasma annealing the dielectric layer of the capacitor may improve the leakage current characteristics of the capacitor and may reduce the amount of impurities in the dielectric layer. By oxygen radical annealing the upper electrode, the leakage current characteristic of the capacitor may be improved and the number of oxygen vacancies formed in the dielectric layer may be reduced.
In a first aspect, embodiments of the present invention provide an apparatus for forming a thin film on a substrate having a multi-functional chamber for depositing a dielectric layer on the substrate and an oxygen radical or plasma annealing unit connected to the multi-functional chamber. The oxygen radical or plasma annealing unit provides oxygen radical or plasma gas to the multi-functional chamber to oxygen radical or plasma anneal one or more electrodes and/or dielectric layers on the substrate in the multi-functional chamber.
In other embodiments of the present invention, the oxygen radical or plasma annealing unit is an ozone generator or a plasma generator. The plasma generator is capable of generating a plasma gas selected from the group consisting of O
2
, NH
3
, Ar, N
2
, and N
2
O. The multi-functional chamber includes an ozone or plasma gas remover connected to an exhaust end of the multi-functional chamber.
In still other embodiments of the present invention, the multi-functional chamber includes a support plate configured to hold the substrate, a heater unit positioned under the support plate, a source dispersion device positioned above the support plate configured to uniformly disperse organic source liquid, and a source supplier in fluid communication with the source dispersion device. The source supplier includes a liquid mass flow controller configured to control a flow of organic source liquid, an evaporator in fluid communication with the flow controller configured to evaporate the source liquid, and a transfer gas source in fluid communication with the evaporator configured to transfer an organic source from the evaporator to the source dispersion device. The source supplier includes between 1 and 3 evaporators.
In yet other embodiments of the present invention, the apparatus includes a cleaning gas supplier in fluid communication with the multi-functional chamber configured to supply cleaning gas to remove dielectric material from a wall of the multi-functional chamber. The apparatus includes a transfer chamber configured to transfer the substrate from a first chamber to a second chamber. The multi-functional chamber is connected to the transfer chamber. The apparatus includes a loadlock chamber configured to introduce the substrate into the apparatus. The loadlock chamber is connected to the transfer chamber. The apparatus includes an electrode deposition chamber, a crystallization annealing chamber, an oxygen radical or plasma annealing chamber configured to pre-treat a lower electrode, and/or a cooling chamber and a pre-heating chamber, each of which is connected to the transfer chamber.
In another aspect, embodiments of the

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