Dissolved oxygen sensor

#This disclosure relates generally to oxygen sensors. More particularly, this disclosure relates to dissolved oxygen (DO) sensors. Even more specifically, this disclosure relates to sensitive, miniaturized DO sensors suitable for ultra-high purity environments.

#An oxygen sensor refers to an electronic device that measures the concentration of oxygen in aqueous solutions in the field or in the laboratory. Currently, the most prevalent type of oxygen sensors are electrochemical sensors such as those used to measure oxygen concentration for determining environmental properties of large bodies of water to ensure appropriate environmental conditions for wildlife. These electrochemical sensors use a probe with electrodes to measure oxygen dissolved in a fluid. More specifically, a cathode and an anode are submersed in an electrolyte. Oxygen enters the probe through a permeable membrane by diffusion, and is reduced at the cathode, creating a measurable electrical current. The relationship between the electrical current and the oxygen concentration is a linear one and thus concentration can be determined from the current and calibration settings for the sensor.

#There is, however, a need for oxygen sensors in other environments. In particular, there is a need for oxygen sensors in ultra-high purity environments such as those defined by SEMI F57 standard, FDA standards in food and drug processing or the like. This need arises for a variety of reasons. For example, the presence of oxygen in semiconductor manufacturing processing may increase corrosion of materials involved in the process (e.g., copper used in a plating process) among other problems.

#A more complete understanding of the present invention and the advantages thereof may be acquired by referring to the following description, taken in conjunction with the accompanying drawings in which like reference numbers indicate like features and wherein:

#FIG. 1 is a diagrammatic representation of one embodiment of the functioning of a dissolved oxygen (DO) sensor;

#FIG. 2 is a diagrammatic representation of the use of a DO sensor in a semiconductor process;

#The disclosure and the various features and advantageous details thereof are explained more fully with reference to the non-limiting embodiments that are illustrated in the accompanying drawings and detailed in the following description. Descriptions of well-known starting materials, processing techniques, components and equipment are omitted so as not to unnecessarily obscure the disclosure in detail. Skilled artisans should understand, however, that the detailed description and the specific examples, while disclosing preferred embodiments, are given by way of illustration only and not by way of limitation. Various substitutions, modifications, additions or rearrangements within the scope of the underlying inventive concept(s) will become apparent to those skilled in the art after reading this disclosure. As an example, it should be noted that embodiments as described herein relate to a dissolved oxygen sensor, however, other embodiments may equally well be utilized to measure the concentration of other chemicals or elements, by for example, using a luminophor responsive to other elements or molecules (e.g., carbon dioxide).

#Before delving into more detail regarding particular embodiments of oxygen sensors, it will be helpful to give an overview of the general operation of embodiments and the context in which such embodiments may be utilized. Turning first to FIG. 1 then, the basic operation of embodiments of an optical dissolved oxygen (DO) sensor is illustrated. Optical sensors use fluorescence optical techniques to take optical measurements of the oxygen concentration. Specifically, a chemical film which has fluorescence properties that depend on the oxygen concentration of a fluid may be utilized. Unlike the measurable electrical current created by electrochemical sensors, the signal (fluorescence) to oxygen ratio for optical sensors may not be linear. Fluorescence is at a maximum when there is no oxygen present. When an oxygen molecule (O2) comes along, it collides with the film and this quenches the photoluminescence. Accordingly, the sensitivity decreases as oxygen concentration increases. This is known as a photophysical intermolecular deactivation (quenching) process. An intermolecular deactivation is where the presence of another chemical species can accelerate the decay rate of a chemical in its excited state. Processes such as fluorescence and phosphorescence are examples of excited state processes which can be quenched.

#DO monitor 100 includes luminophor 110 that is interfaced with fluid 112 (e.g., a liquid or gas) flowing through a fluid flow path 114. For example, DO sensor 100 may include a housing that includes a flow path 114 or may otherwise be interfaced with, or attached to, an existing fluid flow path, through for example a physical coupling. DO sensor 100 may serve to measure the concentration of oxygen present in the fluid 112 as it flows through the flow path 114 using luminophor 110.