Abstract:
CMOS processing is enhanced via a method and system that use a chemical bath purification process. According to an example embodiment of the present invention, solution from a CMOS wet chemical bath is passed over a powered circuit. The powered circuit plates out copper from the solution, and the solution is then returned to the bath. By removing copper from the chemical bath in this manner, cross-contamination of wet chemical equipment is reduced, and the need for redundant tool sets can be eliminated.

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to semiconductor devices and their fabrication and, more particularly, to semiconductor devices and their manufacture involving techniques for the purification of copper-contaminated chemical baths used in CMOS processing. 
     BACKGROUND OF THE INVENTION 
     The semiconductor industry has recently experienced technological advances that have permitted dramatic increases in circuit density and complexity, and equally dramatic decreases in power consumption and package sizes. Present semiconductor technology now permits single-chip microprocessors with many millions of transistors, operating at speeds of hundreds of millions of instructions per second, to be packaged in relatively small, air-cooled semiconductor device packages. Related to the technological advances in the semiconductor industry is a corresponding growth in the use of such technology in virtually every aspect of the economy. This widespread growth has led to a demand for heightened production of semiconductor devices having increasingly complex architecture, as well as a heightened demand for providing access to such technologies for a large portion of the general public at an affordable price. 
     The increasing demand for products utilizing semiconductor technology has resulted in increased competition among manufacturers of semiconductor products. One of the biggest challenges to semiconductor manufacturers includes the production of reliable, complex devices while keeping costs at a marketable or even reduced level. As technology advances and architecture becomes more complex, the manufacturing processes for semiconductor devices and integrated circuits increase in difficulty. The increase in difficulty is accompanied by increased time and value put into the manufacture of the devices. The ability to achieve the manufacture of such devices in an efficient and cost-effective manner is paramount to the success of any semiconductor device manufacturer and to the promulgation of products employing new technologies at an affordable price. 
     One semiconductor manufacturing system that is typically used in semiconductor processing, such as for CMOS devices, is a wet chemical bath. One problem associated with wet chemical baths is the copper cross-contamination of the wet chemical equipment. Copper existing in the wet chemical solution tends to contaminate the tools, often requiring redundant tool sets. The requirement of redundant tool sets increases the cost of the manufacturing process. The difficulty, cost, and destructive aspects of existing methods for CMOS wet chemical processing are impediments to the growth and improvement of semiconductor technologies. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a method and system for cleaning chemical baths used in semiconductor processing, and is exemplified in a number of implementations and applications, some of which are summarized below. 
     According to an example embodiment of the present invention, copper-contaminated wet chemical bath solution is cleaned by plating out the copper from the solution in an electrowinning arrangement. The solution is passed from the chemical bath over a powered cathode and anode. The powered cathode and anode plate out the copper from the solution, and the solution is returned to the chemical bath. In this manner, cross-contamination of equipment used in wet chemical baths is reduced or even eliminated, reducing or eliminating the need for redundant tool sets. 
     The above summary of the present invention is not intended to describe each illustrated embodiment or every implementation of the present invention. The figures and detailed description which follow more particularly exemplify these embodiments. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention may be more completely understood in consideration of the following detailed description of various embodiments of the invention in connection with the accompanying drawings, in which: 
     FIG. 1 is a wet chemical purification arrangement, according to an example embodiment of the present invention; and 
     FIG. 2 is another wet chemical purification arrangement, according to another example embodiment of the present invention. 
    
    
     While the invention is amenable to various modifications and alternative forms, specifics thereof have been shown by way of example in the drawings and will be described in detail. It should be understood, however, that the intention is not to limit the invention to the particular embodiments described. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims. 
     DETAILED DESCRIPTION 
     The present invention is believed to be applicable for a variety of different types of semiconductor wafers, and the invention has been found to be particularly suited for processing CMOS and other type wafers requiring or benefiting from wet chemical bath purification. While the present invention is not necessarily limited to such applications, various aspects of the invention may be appreciated through a discussion of various examples using this context. 
     Wet chemical processing is an integral part of CMOS wafer manufacturing. One aspect of the wet chemical manufacturing process that is particularly expensive is the replacement of tools and other related equipment due to copper cross-contamination. The present invention directly addresses the difficulties associated with copper cross-contamination in wet chemical processing. According to an example embodiment of the present invention, solution from a wet chemical bath is pumped from the bath and over a plating arrangement having an anode and a cathode. The anode and cathode are powered at about 0.5 volts, and copper is plated out of the solution. The solution is returned to the chemical bath and used in further processing. This purification process may take place during semiconductor processing, or may be performed when the chemical bath is not being used for processing. 
     FIG. 1 is an example system  100  for plating out copper from a wet chemical bath solution. The solution is delivered via a fluid supply line  130  to a plating arrangement  110  having an anode  120  and a cathode  125 . The anode  120  and cathode  125  are powered via a power supply  150  at a voltage of about 0.5 volts. Copper is plated out of the solution at the plating arrangement  110 , and the solution is returned to the chemical bath via fluid return line  140 . 
     In another example embodiment of the present invention, a separate plating loop is used in combination with a filter arrangement and a plating arrangement having an anode and a cathode. Chemical bath solution is pumped from a chemical bath to the filter arrangement. The filter arrangement is connected via fluid lines to a plating pump and the plating arrangement having an anode and a cathode. The solution passes into the filter arrangement, is pumped through the plating arrangement via the recycle pump, returned to the filter arrangement, and delivered back to the chemical bath. 
     FIG. 2 shows a chemical bath purification system  200  having such a plating loop  280 , according to an example embodiment of the present invention. FIG. 2 also shows an optional recycle loop  270 , according to another example embodiment of the present invention. First, the process not using the recycle loop  270  is described. Wet chemical processing solution is pumped from a wet chemical bath to a filter arrangement  260  via fluid supply line  230 . The solution enters the filter arrangement  260  and is pumped to a plating arrangement  210  via a plating pump  265 . The plating arrangement  210  has an anode  220  and a cathode  225  coupled to a power supply  250 . The power supply  250  is used to supply about 0.5 volts to the anode and cathode, and copper is plated out of the solution. The solution is then returned to the filter arrangement  260  via the plating loop  280 , and is returned to the chemical bath from the filter arrangement  260  via fluid return line  240 . 
     The optional recycle loop provides the ability to recycle the solution to the plating arrangement prior to returning it to the chemical bath. For example, this may be useful for achieving a greater reduction of copper in the solution. The optional recycle loop works as follows: Wet chemical solution is delivered to the filter arrangement  260  and the plating arrangement  210  as described in the above paragraph. Once the solution is pumped into the plating loop  280 , valve arrangements  271  and  272  are closed, bypassing the filter arrangement via the recycle loop  270 . Valve arrangements  271  and  272  may, for example, include three-way valves coupled to direct the solution either to the filter arrangement  260  or to the recycle loop  270 , or may include a combination of two-way valves. The plating pump  265  is used to recycle the solution through the plating arrangement  210 . The amount of time that the solution is recycled depends upon the desired amount of copper plating that is desired, and can he determined as a function of the wet chemical process and the amount of copper that is in the solution. After the solution has been sufficiently purified, the valves  271  and  272  are opened, and the solution returns to the filter arrangement  260 , and is delivered back to the wet chemical bath. 
     In another example embodiment, the purification system may include a programmable controller, such as a computer, adapted to control the function of the system. For example, a programmable controller can be programmed to turn on a pump to the purification system, deliver solution to the system, and activate the power supply to the anode and cathode arrangement. When a separate plating loop is controlled, or when a recycle loop is controlled, the controller is also coupled to control other functions of the process, such as the operation of the plating pump  265  and the valve arrangements  271  and  272 . 
     The programmable controller can also be used to control the amount of time that the solution is passed through the recycling loop. Such control of the recycling time can be pre-programmed into the controller, or can be a function of the process at hand, such as by detecting the amount of copper in the solution and determining when the amount is below a particular threshold. 
     While the present invention has been described with reference to several particular example embodiments, those skilled in the art will recognize that many changes may be made thereto without departing from the spirit and scope of the present invention, which is set forth in the following claims.