Coating processes – Electrical product produced – Integrated circuit – printed circuit – or circuit board
Reexamination Certificate
1998-09-02
2003-04-08
Talbot, Brian K. (Department: 1762)
Coating processes
Electrical product produced
Integrated circuit, printed circuit, or circuit board
C427S294000, C427S304000, C427S437000, C427S443100
Reexamination Certificate
active
06544585
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates in general to next generation technology for fabricating electrical interconnects in integrated circuit devices, and relates in particular to a method and apparatus for filling micro-cavities formed on a surface of a substrate with metal plating.
2. Description of the Related Art
Aluminum is a typical material used for fabricating conductor circuit patterns in integrated semiconductor devices. An aluminum conductor line pattern is fabricated by first sputtering an aluminum film on a semiconductor wafer (wafer), followed by forming circuit patterns on the aluminum film by means of photolithography, and etching off unwanted regions to complete the conductor line pattern. As the devices become more highly integrated, there have been increasing demands for a finer conductor line pattern. Referring to
FIGS. 27A-27C
, to meet such demands for micro-fabrication, the width of grooves
303
and contact hole
301
for producing conductor line
311
and plug
313
must be made smaller, typically in a range of 0.13 to 0.18 &mgr;m. When the width of the conductor line becomes so narrow, aluminum begins to show problems due to its inferior properties.
To other types of metals than aluminum, the above-described conventional method of circuit fabrication is sometimes difficult to apply, and therefore, a damascene process has been performed by fabricating stud holes and wiring cavities on a circuit board first, and then filling the cavities with a suitable metal by using processes such as chemical vapor deposition (CVD), sputtering or plating, and finishing the circuit board by chemical mechanical polishing (CMP) to complete conductor line fabrication.
Plating has been used widely for forming metallic films and has many advantages.
FIG. 28
shows a setup for conventional plating. A plating chamber
1
contains a plating solution
9
in which are immersed a cathode
3
, having a substrate W, and an opposing anode
4
, and the plating solution
9
is stirred with a stirrer
11
during plating.
Compared to other processes, the plating cost is relatively low, high purity products can be produced, and processes can be done at a relatively low temperature to avoid degrading thermal effects. However, it is difficult to use plating to fill micro-cavities C such as grooves
303
and contact holes
301
without leaving some internal voids. When a substrate W having micro-cavities C is immersed in plating solution
9
, it is not unusual to have residual air remaining inside the cavities C, and it is not possible to infiltrate the cavities C completely with the plating solution
9
. This is considered to be due to the effects of wettability of the substrate W and the surface tension force of plating solution
9
, and, especially for such shapes as the contact hole
301
, which is deeper than it is wide (for example, an aspect ratio, depth/width, of about 5), air tends to remain in the cavity much more frequently. Similarly, it becomes much more difficult to displace spent liquid of plating solution
9
with fresh plating solution containing active metallic ions. This difficulty increases as the width of the cavities C becomes narrower.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a method and an apparatus for plating to enable a high quality metallic deposit to be produced inside the micro-cavities formed on a surface of a substrate, such as a semiconductor wafer, by completely infiltrating the micro-cavities with a plating solution and refreshing the plating solution in the micro-cavities during plating.
The present invention is to establish such an object by a method for producing a metal deposit inside micro-cavities fabricated on a substrate comprising: immersing the substrate in a liquid held in a processing chamber; evacuating the processing chamber so as to remove residual bubbles from the micro-cavities and to degas the liquid within the micro-cavities; and subjecting the liquid to boiling in at least those regions adjacent to the substrate.
Accordingly, after removing the gas dissolved in the liquid or residual bubbles from the micro-cavities utilizing a phenomenon of nucleate boiling, the plating solution is infiltrated into the cavities so that metal can be plated inside of the cavities to efficiently produce a high quality deposit which is free of internal defects. This process is basically applicable to both electro- and electroless-plating processes.
The liquid may comprise a plating solution so that plating can be readily performed. In another option, a preferred liquid other than a plating solutions which is more easily introducible to the micro-cavities is usable. Such liquid may include water, alcohol or another suitable liquid. In this case, replacing or diluting the liquid with a plating solution may be necessary prior to plating.
The processing chamber may be a plating chamber so that the plating process can be done without transferring the substrate. In another option, the processing chamber may be made as a pre-plating processing chamber only for the pre-plating process.
In the boiling step, interior chamber pressure may be reduced to a value less than a saturated vapor pressure of the liquid. This will lower the boiling point of the liquid so that there is no need to raise the temperature of the liquid to a high temperature, thus resulting in an energy efficient and productive plating process. In the boiling step, the substrate may be heated from a back surface of the substrate. This will promote selective heating of those regions close to the cavities so that expelling of bubbles from the cavities and boiling in the cavities are enhanced. In the boiling step, interior chamber pressure may be reduced and at the same time, the substrate may be heated from the back surface.
Between a degassing step and a boiling step, interior chamber pressure may be raised to a high pressure. Also, boiling and pressurizing may be repeatedly carried out. These steps will enable the solution to reliably infiltrate the cavities, and to replace the solution inside the cavities periodically with fresh solution, thereby realizing defect-free plating.
It is also permissible to perform a boiling step while plating. Boiling may be carried out intermittently or continuously. This will enable to carry out plating while exchanging old plating solution inside the cavities with fresh plating solution to efficiently carry out the process of depositing metal in the cavities.
In another aspect of the invention, an apparatus for producing a metal deposit inside micro-cavities fabricated on a substrate comprises a sealable processing chamber; an evacuating device for reducing interior chamber pressure; and a gas inlet device for pressurizing the chamber interior. The evacuating device is capable of selectively reducing interior chamber pressure to at least two pressure values, one being less than a saturated vapor pressure of the liquid, and the other being an intermediate value between the saturated vapor pressure and atmospheric pressure.
In this apparatus, liquid such as plating solution in the chamber, air, dissolved gas or gas bubbles in the plating solution, and bubbles attaching to the substrate can be made to undergo volume change or changes in their liquid state, so that liquid may be infiltrated into the cavities and/or the old solution may be refreshed with new solution. This will permit to form a metal deposit within the cavities efficiently by plating, without creating internal defects in the deposited metal. A heating device to heat the plating solution may be provided to facilitate the liquid filtration or to raise plating efficiency.
The evacuating device may have an exhaust pipe to connect a vacuum pump for reducing interior chamber pressure, and the exhaust pipe may be provided with a shutoff valve and a control valve for adjusting flow resistance. This will permit the system to be switched between two vacuum levels: a pressure intermediate between one atmosphere and the saturated va
Hongo Akihisa
Inoue Hiroaki
Kuriyama Fumio
Tokuoka Tsuyoshi
Ebara Corporation
Talbot Brian K.
Wenderoth , Lind & Ponack, L.L.P.
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