Coating processes – Direct application of electrical – magnetic – wave – or... – Pretreatment of substrate or post-treatment of coated substrate
Reexamination Certificate
1998-12-22
2002-04-16
Chen, Bret (Department: 1762)
Coating processes
Direct application of electrical, magnetic, wave, or...
Pretreatment of substrate or post-treatment of coated substrate
C427S535000, C427S250000, C427S255391, C427S255394, C204S192100
Reexamination Certificate
active
06372301
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of tile Invention
The present invention generally relates to deposition of films onto a substrate. More particularly, the present invention relates to deposition of diffusion barriers and fluorinated silicon glass.
2. Background of the Related Art
As feature sizes have become smaller and multilevel metallization commonplace in, integrated circuits, low dielectric constant films have become increasingly important. Low dielectric constant films are particularly desirable for intermetal dielectric (IMD) layers to reduce the RC time delay of the interconnect metallization being covered to prevent crosstalk between the different levels of metallization, and to reduce device power consumption.
Many approaches to lower dielectric constants have been proposed. One of the more promising solutions is the incorporation of a halogen element, such as fluorine, chlorine or bromine into a silicon oxide layer. Fluorine, the preferred halogen dopant for silicon oxide, lowers the dielectric constant of the silicon oxide film because fluorine is an electronegative atom that decreases the solubility of the overall silicon oxide film. Fluorine-doped silicon oxide films are referred to as fluorosilicate glass films or FSG for short.
In addition to decreasing the dielectric constant, incorporating fluorine in silicon oxide layers also helps to solve common problems encountered in fabricating smaller geometry devices, such as filling closely spaced gaps between metal or polysilicon lines deposited over semiconductor structures. It is believed that because fluorine is an etching species, the introduction of fluorine during deposition of a silicon oxide film introduces an etching effect on the growing film. The simultaneous deposition/etching effect allows FSG films to have improved gap-filling capabilities such that the films are able to adequately cover adjacent metal layers having an aspect ratio of 1.8 or more. Thus, manufacturers desire to include fluorine in various dielectric layers and particularly in intermetal dielectric layers in multilevel structures.
Current integrated circuits generally include various formations of multilevel metal structures that form a high-conductivity, thin-film network fabricated above the silicon surface to connect various active devices through specific electrical paths. During the formation of metal-to-metal and metal-to-silicon contact structures in this thin-film network, openings are etched in the intermetal dielectric layer, such as the doped silicon dioxide film, that separates the substrate or underlying conductive thin film from the overlying conductive thin film. A conductive material, such as copper, aluminum or another metal, is then used to fill the opening and make a connection to the silicon substrate or underlying conductive thin film. Ideally, the impedance to current flow between the silicon and overlying connecting metal layer or between the underlying and overlying connecting metal layers should be as low as possible.
Diffusion barriers play a prominent role in the formation of multilevel metal structures which are present in many integrated circuits. Diffusion of materials between adjacent layers in semiconductor devices is a particular concern to those in the semiconductor industry. Such diffusion or intermixing may be prevented by sandwiching another material or stack of materials between the layers. The role of this third material or stack of materials is to prevent or retard the diffusion of the two materials into each other and hence the layer is often referred to as a diffusion barrier.
With the recent progress in sub-quarter-micron copper interconnect technology, tantalum and tantalum nitride have become popular barrier materials in addition to titanium and titanium nitride. Depending on the application, a diffusion barrier layer may comprise a tantalum layer, a tantalum nitride layer, a tantalum/tantalum nitride stack or other combinations of diffusion barrier materials. The diffusion barrier layer is commonly deposited over the doped silicon oxide film after openings for interconnect structures (contacts or vias) have been etched in the doped silicon oxide film. A metal, such as copper, is then deposited over the diffusion barrier to fill the interconnect feature.
During substrate processing, heat treatment steps in which a substrate is heated to a specified temperature for a specified time are employed for various reasons. For example, an anneal step may be used to repair damage to a substrate after a plasma processing step.
However, when a FSG film is subjected to a temperature greater than about 350° C., loosely-bonded (dangling bonds) fluorine atoms and residual fluorine atoms tend to be released from the FSG film. The released fluorine atoms from the FSG film react with the tantalum component of the tantalum nitride barrier layer and form volatile TaF
2
. TaF
2
formation increases the resistance of the interconnect structure and causes significant losses in the adhesion properties between the tantalum nitride layer and the FSG film. The loss in adhesion properties causes the tantalum nitride barrier layer to peel off during subsequent processing of the substrate, resulting in the formation of defects. Similarly, for a titanium based barrier layer, the released fluorine atoms react with the titanium to form TiF, which leads to defect formations on the substrate as TiF
2
.
From the discussion above, it can be seen that low dielectric constant films, such as FSG and other halogen-doped silicon oxides, are desirable to use as intermetal dielectric layers in multilevel metal structures. However, there is a need to prevent reactions between the halogen-doped silicon oxides and the adjacent diffusion barrier material.
U.S. Pat. No. 5,763,010, by Guo et al, hereby incorporated by reference, illustrates an attempt to stabilize a halogen-doped silicon oxide film and to reduce halogen atoms migration and reaction with adjacent films during subsequent processing. The deposited halogen-doped silicon oxide film is subjected to a degassing step in which the film is briefly heated to a temperature of between about 300° C. and about 500° C. for between about 35 seconds and about 50 seconds before deposition of the barrier layer. The heat degassing treatment removes loosely bonded halogen atoms. However, the heat degassing treatment may produce more loosely bonded halogen atoms in the halogen-doped silicon oxide film when the substrate has been heated for a longer period of time than the optimal heat degassing treatment time. Furthermore, when the substrate has been heated for a shorter period of time than the optimal heat degassing treatment time, the heat degassing treatment may remove an insufficient amount of loosely bonded halogen atoms in the halogen-doped silicon oxide film. Also, it is generally preferred to minimize the substrate's exposure to a heated environment.
Therefore, there remains a need for a method to stabilize a halogen-doped silicon oxide film and to prevent loosely bonded halogen atoms from reacting with components of the barrier layer during subsequent processing of the substrate without subjecting the substrate to a heated environment. It would be desirable for the method to improve the adhesion strength between the halogen-doped silicon oxide film and the barrier layer. It would be further desirable for the method to be practiced in an integrated process sequence with other substrate processing such that the method can be practiced in a variety of processing chambers, including both physical vapor deposition chambers as well as chemical vapor deposition chambers.
SUMMARY OF THE INVENTION
The present invention generally provides a method for stabilizing a halogen-doped silicon oxide film and preventing loosely bonded halogen atoms from reacting with components of the barrier layer during subsequent processing of the substrate. The invention provides a hydrogen plasma treatment of the halogen-doped silicon oxide film without subjecting the substrate to a heated environment that may
Li Xiangbing
Narasimhan Murali
Ngan Kenny King-Tai
Pavate Vikram
Applied Materials Inc.
Chen Bret
Moser Patterson & Sheridan LLP
LandOfFree
Method of improving adhesion of diffusion layers on... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method of improving adhesion of diffusion layers on..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method of improving adhesion of diffusion layers on... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2901971