1. Field of the Invention
The present invention relates generally to the determination of additives in metal plating solutions, and more specifically, to a method and system for analysis of additives in electrochemical plating solutions using a flow management system that minimizes loss of plating solutions and decreases sampling time.
2. Description of the Related Art
The microelectronic manufacturing industry applies a wide range of thin film materials to form microelectronic structures. These thin film materials include metals and metal alloys such as, for example, nickel, tungsten, tantalum, solder platinum, copper, copper-zinc, as well as dielectric materials, including metal oxides, semiconductor oxides, and perovskite materials.
A wide range of processing techniques has been used to deposit such thin films, including chemical vapor deposition, electroplating and electroless plating. Of these techniques, electrochemical processing techniques, i.e., electroplating, and electroless plating are the most economical.
Electroless plating uses an electrolyte wherein suitable salts of the desired deposition metals are dissolved therein. The electrolyte can be water-based, organic-based or a molten salt, depending on the specific metal to be deposited.
Metal deposition from solution has been used for depositing copper during the production process of printed circuit boards in the microelectronics industry. Electrochemical deposition is the preferred method because of several advantages over chemical or physical vapor deposition that include the avoidance of using a vacuum system and overall reduced costs. However, when electrochemical techniques are employed, optimum process performance cannot be obtained without careful control of the plating bath chemistry. Notably, the quality and efficiency of the electrochemical plating process depend on the bath composition, pH and temperature.
Currently, most semiconductor manufacturers replenish plating baths based on time or energy consumption (e.g., amp hours). However, the use of such replenishment methods is based on the fact that the plating system always functions under ideal conditions, when in fact, human error and system malfunctions can affect the depletion rate of the components. To overcome the uncertainty of timed replenishing operations, in-line monitoring systems have been adapted for use in plating systems that monitor the metal levels in the plating baths and replenish the baths when needed. These systems minimize contamination, however, the sampling process can be time-consuming and any delay in determining analyte concentrations in the solutions can produce problems in maintaining the desired properties of the electrodeposited metals. Furthermore, these in-line sampling techniques can consume a considerable amount of sample thereby wasting expensive plating solutions and/or adversely affecting the economics of the semiconductor manufacturing operation.
Accordingly, there is a need in the art for a sampling method and system that overcome the shortcomings of the prior art, such as excessive wastage of plating solutions, slow reaction times from sampling to replenishing of plating baths, and contamination from previous testing samples.