Electrolysis: processes – compositions used therein – and methods – Electrolytic coating – Treating process fluid by means other than agitation or...
Reexamination Certificate
1999-02-09
2001-01-23
Gorgos, Kathryn (Department: 1741)
Electrolysis: processes, compositions used therein, and methods
Electrolytic coating
Treating process fluid by means other than agitation or...
C205S099000, C205S109000
Reexamination Certificate
active
06176993
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a process for recycling a reaction system of electroplating passivation of wafer. More particularly, the present invention relates to a process for recycling a reaction system of electroplating passivation of wafer for improving the recycling efficiency and increasing the economic advantages thereof.
BACKGROUND OF THE INVENTION
Batch electroplating passivation reaction predominates the current electrical industry, particularly in the manufacture of wafers. To obtain the optimal stabilization of electrical properties and reliability of products, it is typical to manufacture products with stricter property requirement in a small production. For products in a mass production, electroplating solutions should be removed when a specific production is achieved.
For a general process for electroplating passivation of glasses, the electroplating solution used comprises isopropanol, water, lanthanum nitrate, and a glass powder, in which lanthanum ion is used as a carrier of the glass powder so that the glass powder is passivated on the object being deposited. Due to the collection of pollutants and the consumption of additives or uncompensible effect, the quality of the electroplating solution is getting worse and the efficiency of the electrolysis is poor, especially when the electrolysis is conducted in a batch system reactor. The poor efficiency of electrolysis will directly reduce the current reaction induced thereby. Even worse, the electrolysis will not take place.
To solve the problem of poor quality of the electroplating solution, the most common measure is to directly replenish reactants consumed during electrolysis, i.e., to replenish lanthanum nitrate. However, the above measure will result in a collection of NO
3
−
as a by-product so that the electrolysis is negatively influenced. Hence, the manufacture of wafers will be negatively influenced. Generally speaking, for an electroplating solution comprising a lanthanum ion of lanthanum nitrate as the carrier of the glass powder, when the concentration of the electroplating solution decreases to 70% of the original concentration, the electroplating solution should be removed to maintain the electroplating property. Thus, the cost of the manufacture will be highly increased. In considering a reasonable cost and a mass production satisfying the demand of market, it is worthwhile to search an economically recyclable electroplating solution.
U.S. Pat. No. 4,233,133 discloses a passivating bath for a semiconductive body and a process for protectively coating a semiconductive body by immersing the same in a bath having particles of a vitreous or ceramic passivating material suspended therein. The bath is formed by suspending passivating particles such as glass thereinto. The bath consists essentially of an organic solvent such as acetone, an amine and a hydrohalogenic acid in proportions yielding a preferable alkaline pH between 4 and 10. This patent uses a batch electroplating passivation reaction for a passivation process and no recycling of electroplating solution is disclosed .
U.S. Pat. No. 3,642,597 is directed to a process for passivating a junction containing semiconductive elements comprising applying an electrically insulative coating to selected surface areas of a junction containing semiconductive wafer, etching the semiconductive wafer through the exposed surface areas to form a depression extending to a depth below at least one junction, removing the portions of the insulative coating undercut in etching, and depositing a junction passivant within the etched depression of the semiconductive wafer. This patent uses a batch electroplating passivation reaction for a passivation process and the used electroplating solution cannot be recycled to extend the time for depositing.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a process for recycling a reaction system of electroplating passivation of wafers.
Another object of the present invention is to provide a process for recycling a reaction system of electroplating passivation of wafers, in which a semibatch (continuous) process is used to conduct a electroplating deposition reaction.
Yet another object of the invention is to provide a process for recycling a reaction system of electroplating passivation of wafers, in which a semibatch (continuous) process is used to conduct a electroplating deposition reaction and lanthanum hydroxide is added (when lanthanum nitrate is used to provide lanthanum ions acting as a carrier) or magnesium hydroxide is added (when lanthanum hydroxide is used to provide a lanthanum ion as a carrier) to supplement lanthanum ions or magnesium ions consumed in the electroplating solution during the electrolysis.
Yet another object of the present invention is to provide a process for recycling a reaction system of electroplating passivation of wafers, in which the yield of the manufacture of wafers is increased by a few times and an economical effect is achieved.
The above features and advantages of the present invention will be better understood with reference to the detailed description and examples. It should also be understood that the process for recycling a reaction system of electroplating passivation of wafers illustrating the present invention is exemplary only and not to be regarded as a limitation of the invention.
DETAILED DESCRIPTION OF THE INVENTION
By way of illustration and to provide a more complete appreciation of the present invention with many of the attendant advantages thereof, the following detailed description is given concerning the process for recycling a reaction system of electroplating passivation of wafers.
The present invention relates to a process for recycling a reaction system of electroplating passivation of wafer, in which lanthanum hydroxide (La(OH)
3
) is added (when lanthanum nitrate is used to provide lanthanum ions as a carrier) or magnesium hydroxide (Mg(OH)
2
) is added (when lanthanum hydroxide is used to provide a lanthanum ion as a carrier) to supplement the lanthanum ion or magnesium ion consumed in an electroplating solution when pH of the electroplating solution decreases to a range from 0.1 to 0.4, preferably when pH of the electroplating solution decrease to 0.4.
The additive dissolves in acid and supplements lanthanum ions or magnesium ions consumed in the electroplating solution. The amount of the additive is generally a half to one-fourth of the theoretical amount to avoid the negative influence on the electroplating solution caused by the additive which cannot quickly dissolve in time. After the additive is added, the pH of the electroplating solution is controlled within a range of the original pH and a value below 0.4 from the original pH by an automatic addition system.
The electroplating solution comprises a solvent, water, a carrier material, and a passivant material.
The solvent may be an alcohol, such as isopropanol, n-butanol, isobutanol, or a solvent having similar viscosity, dielectric constant, and molecular structure.
Water is preferably a de-ionized water.
The carrier material may be lanthanum nitrate or magnesium hydroxide. Lanthanum nitrate provides lanthanum ions for the carrier of the passivant material. Magnesium hydroxide provides magnesium ions for the carrier of the passivant material.
The passivant material can be dielectric material, preferably a glass powder.
In the electroplating solution, a chemically inert metal is used as an anode, preferably a platinum anode.
In the electroplating solution, an object which can be deposited, a wafer, is used as a cathode.
The electroplating solution of the present invention will be explained with respect to the components of the electroplating solution, initial effect and addition effect when an additive is added.
The components of the electroplating solution comprise isopropanol, de-ionized water, lanthanum nitrate, and a glass powder.
Total Reaction of the Electroplating Solution
La(NO
3
)
3
→La
3+
+3NO
3
−
La
3+
+
General Semiconductor of Taiwan, Ltd.
Gorgos Kathryn
Mayer Fortkort & Williams LLC
Nicolas Wesley A.
LandOfFree
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