Non-contact optical techniques for measuring surface conditions

A non-contact method of determining a characteristic of a surface, comprising the steps

• directing against said surface incident electromagnetic radiation having a time varying component, wherein a portion of said incident radiation is reflected from said surface with such a time varying component,
• generating a first electrical signal corresponding to a combined level of said reflected portion of the incident electromagnetic radiation and electromagnetic radiation that is emitted from said surface,
• generating a second electrical signal corresponding to a level of the incident electromagnetic radiation that is being directed against said surface,
• determining a mean value of each of the first and second electrical signals,
• integrating each of the first and second electrical signals with respect to their respective mean values, thereby to provide a value of a time varying component in each of said first and second signals, and
• combining at least the time varying component values of said first and second signals in a manner to obtain said surface characteristic.

In a system for forming a layer of material on a substrate surface that is positioned within a chamber having a substantially optically transparent window in a wall thereof, wherein said substrate is heated by directing continuous wave electromagnetic radiation of a given bandwidth against said substrate through said window from outside of said chamber from an electromagnetic radiation source that is characterized by having a time varying intensity component, an improvement adapted to monitor formation of said layer, comprising:

• a first photodetector that is characterized by generating an electrical signal proportional to a level of electromagnetic radiation incident thereon that includes said time varying intensity radiation component,
• means positioned with respect to the substrate surface for carrying to the first photodetector both a portion of source electromagnetic radiation after interaction with said substrate surface and electromagnetic radiation emitted by said substrate surface within the bandwidth of the source electromagnetic radiation, thereby to generate a first electrical signal that contains a first time varying component,
• means for generating a second electrical signal that contains a second time varying component corresponding to the time varying intensity component of the source of electromagnetic radiation and substantially without any component corresponding to the radiation emitted from the substrate surface, and
• means receiving said first and second electrical signals with their respective time varying components for determining a characteristic of the layer.

A method of monitoring one of a physical and chemical characteristic of a material surface, comprising the steps of:

• directing electromagnetic radiation toward the surface in a manner to be modified thereby, said radiation including a given wavelength range and having a periodic intensity variation,
• detecting a level of the intensity of the given wavelength range of the electromagnetic radiation modified by the surface to thereby generate a first electrical signal having a periodic intensity variation of a first magnitude,
• generating a second electrical signal having a periodic intensity variation of a second magnitude that corresponds to the intensity of the electromagnetic radiation within said given wavelength range that is being directed toward the layer and surface,
• determining from at least the magnitudes of the periodic intensity variations of the first and second electrical signals a quantity related to an emissivity of the surface, and
• using said emissivity related quantity to determine one of a physical and chemical characteristic of the surface.

A non-contact method of measuring the temperature of a surface, comprising:

• directing continuous electromagnetic radiation toward the surface in a manner to be modified thereby, said radiation including a given wavelength range and having a d.c. intensity level with a periodic a.c. intensity ripple superimposed thereon,
• detecting a combined level within the given wavelength range of the directed electromagnetic radiation after being modified by the surface and of electromagnetic radiation emitted from the surface to thereby to generate a first electrical signal having a first d.c. component with a periodic a.c. intensity ripple component of a first characteristic superimposed thereon,
• generating a second electrical signal corresponding to the directed electromagnetic radiation, said second electrical signal having a second d.c. component with a periodic a.c. ripple component of a second characteristic superimposed thereon, and
• combining the first and second d.c. components with the first and second a.c. component characteristics in a manner to determine the temperature of the surface.

A non-contact method of measuring the temperature of a surface, comprising:

• directing electromagnetic radiation toward the surface in a manner to be modified thereby, said electromagnetic radiation including a repetitive time varying component,
• generating a first electrical signal corresponding to the magnitude over time of the electromagnetic radiation within a given wavelength range that is so directed, said first signal thereby having a repetitive time varying component,
• generating a second electrical signal corresponding to a common optical signal over time which includes electromagnetic radiation within said given wavelength range that is emitted from the surface and the directed electromagnetic radiation within said given wavelength range after being modified by the surface, said second electrical signal thereby also having a repetitive time varying component, and
• calculating the temperature of the surface from the first and second electrical signals, the calculation using relative characteristics of the repetitive time varying components of the first and second electrical signals.