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  Adjustable dosing algorithm for control of a copper electroplating bathUSPTO Application #: 20070089990Title: Adjustable dosing algorithm for control of a copper electroplating bath Abstract: A method and apparatus for supplying a dose to an electrolyte solution including measuring the time after adding fresh solution, measuring the Amp-hours after adding fresh solution, measuring the number of substrates processed by the solution, calculating the volume of a dose to supply to the solution based on the time, Amp-hours, and number of substrates processed, and adding the dose to the solution. (end of abstract)
Agent: Patterson & Sheridan, LLP - Houston, TX, US Inventors: Joseph F. Behnke, Timothy R. Webb, Yevgeniy Rabinovich, Bo Zheng, Thomas J. Fischenich USPTO Applicaton #: 20070089990 - Class: 205081000 (USPTO) Related Patent Categories: Electrolysis: Processes, Compositions Used Therein, And Methods Of Preparing The Compositions, Electrolytic Coating (process, Composition And Method Of Preparing Composition), Involving Measuring, Analyzing, Or Testing The Patent Description & Claims data below is from USPTO Patent Application 20070089990. Brief Patent Description - Full Patent Description - Patent Application Claims
BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] Embodiments of the present invention generally relate to semiconductor processing. More specifically, embodiments of the present invention generally relate to a control scheme for electroplating solutions. [0003] 2. Description of the Related Art [0004] Electroless and electroplating deposition techniques have become an attractive option for depositing copper and copper alloys onto semiconductor substrates and into high aspect ratio features. [0005] Conventional electroplating methods generally include positioning a substrate into an electrolytic solution. An electrical bias is then applied between the surface of the substrate and an anode positioned in the electrolytic solution which operates to urge copper ions to deposit on the substrate surface. During non-processing time periods, i.e., when substrates are not being plated, the electrolytic solution is generally circulated through a continual fluid path that includes a relatively small volume plating region and a substantially larger volume storage region. The storage region, for example, may hold approximately 15 liters of the electrolytic solution, while the plating region may hold approximately 2 liters of the electrolytic solution. Additionally, the continual fluid path may include an electrolyte replenishment device configured to replenish portions of the electrolytic solution that may be depleted through plating operations. [0006] Typical electrolyte solutions used for copper electroplating generally consist of copper sulfate solution having sulfuric acid and copper chloride added thereto. The sulfuric acid generally operates to modify the acidity and conductivity of the solution, while the copper chloride provides negative chlorine ions needed for nucleation of suppressor molecules and facilitates proper anode corrosion. The electrolytic solutions also generally contain various organic molecules which may be accelerators, suppressors, levelers, brighteners, etc. These organic molecules are generally added to the electrolytic solution in order to facilitate void-free fill of features and planar copper deposition. Accelerators may be sulfide-based molecules that locally accelerate electrical current at a given voltage where they absorb. Suppressors may be polymers of polyethylene glycol, mixtures of ethylene oxides and propylene oxides, or block copolymers of ethylene oxides and propylene oxides which tend to reduce electrical current at the sites where they absorb and slow plating at those locations. Levelers may be nitrogen containing long chain polymers which operate to facilitate planar copper deposition. [0007] During the plating process, copper ions are continually being removed from and replenished to the electrolytic solution. Thus, the copper concentration of the electrolytic solution may change or vary over time. This concentration change may further be affected by volume depletion of the electrolytic solution or dissolution of the anode. The volume of water within the electrolytic solution is also in flux as the electrolytic solution is consumed, evaporates, and is retained by the supply piping, volume storage region, or the plating region. [0008] Additionally, plating operations deplete the various organic molecules in the electrolyte solution and each organic concentration also varies over time. For example, levelers are known to deplete and breakdown upon exposure to oxygen containing elements such as ambient air, oxygen absorbed into the electrolytic solution, oxygen molecules contained in the anode metal, or oxidation encountered during plating by incorporation into a growing film. This breakdown process generates free radicals in the electrolytic solution, which are undesirable because the free radicals can deposit on a substrate and contaminate the metal layer. Further, levelers are known to break down upon exposure to copper, copper alloys, and platinum, all of which are typical anode materials for electroplating systems. Similarly, accelerators and suppressors may also suffer from depletion and breakdown characteristics as a result of oxygen or metal exposure. [0009] Depletion of organics is not limited to processing time periods because the electrolyte solution in an electroplating system is generally continually circulated through the plating region and the volume storage region during non-processing time periods. As a result of the circulation, the electrolyte solution may be continually exposed to both oxygen-containing elements and the metal anode. Thus, the organic molecules in the electrolyte solution are continually being depleted, even though the plating region is not in a plating or operational mode. [0010] Because the concentration of the organics in the electrolyte solution and the concentration of the radicals generated by the organic molecule degradation and depletion have a substantial effect upon the efficiency and controllability of plating operations, replenishment of depleted organics in the electrolyte solution to maintain specific organic concentrations is desired. Conventional plating systems generally provide a replenishment module configured to add fresh organics into the electrolyte solution in order to replenish depleted organic molecules. However, conventional organic replenishment processes generally require time consuming organic molecule measurement processes, which decrease the accuracy of conventional organic replenishment processes. This variance in organic concentration may detrimentally affect the ability to accurately control conventional electroplating apparatus. Therefore, there exists a need for a method for accurately replenishing organic molecules and water in an electroplating bath during plating operations. SUMMARY OF THE INVENTION [0011] The present invention generally provides method and apparatus for dosing an electrolyte solution including measuring the time after adding fresh solution, measuring the total Amp-hours used during electroplating after adding fresh solution, measuring the number of substrates processed after adding fresh solution, calculating the volume of a dose to supply to the electrolyte solution based on the time, the total Amp-hours, and the number of substrates processed, and adding the dose to the electrolyte solution. [0012] The present invention also generally provides method and apparatus for supplying a dose to an electrolyte solution including measuring the loss of a volume of fluid from a solution vessel, measuring the time after adding fresh solution, measuring the total Amp-hours used during electroplating after adding fresh solution, measuring the number of substrates processed by the electrolyte solution, calculating a dose to supply to the electrolyte solution based on the time, the total Amp-hours, and the number of substrates processed, and adding the dose to the electrolyte solution. [0013] The present invention also generally provides method and apparatus for dosing an electroplating bath including monitoring total Amp-hours used during electroplating, monitoring total evaporation loss during electroplating, dosing water and chemicals to the electroplating bath after either the total Amp-hours or the total evaporation loss exceed set targets, and then resetting both the total Amp-hours and the total evaporation loss to zero. BRIEF DESCRIPTION OF THE DRAWINGS [0014] So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments. [0015] FIG. 1 is a top plan view of one embodiment of an electrochemical plating system of the invention. [0016] FIG. 2 is a sectional view of one embodiment of an electrochemical process cell. [0017] FIG. 3 is a schematic diagram of one embodiment of a plating solution delivery system. [0018] FIG. 4 is a schematic diagram of one embodiment of components for a plating solution delivery system. [0019] FIG. 5 is a flow chart of a control scheme for an electroplating bath during plating operations. [0020] FIG. 6 is a flow chart of an alternative control scheme for an electroplating bath during plating operations. DETAILED DESCRIPTION Continue reading... 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