Apparatus and method for aligning a wafer's backside to a wafer's frontside

A method for aligning structures of a backside of a wafer to structures of a frontside of the wafer for a lithographic treatment of the backside, wherein the wafer is transparent for infra-red light of a specific wavelength, the method comprising:

• placing the wafer on a wafer stage such that the frontside faces the wafer stage and the backside faces alignment optics;
• illuminating the backside with infra-red light of the specific wavelength in a dark-field configuration, such that the infra-red light propagates through the wafer towards three-dimensional structures of individual three-dimensional alignment targets spaced apart from each other and located at the frontside or inside the wafer and is scattered at the three-dimensional structures towards the backside;
• capturing the scattered infra-red light with the alignment optics;
• and
• aligning the backside to the frontside of the wafer based on the scattered infra-red light,
• wherein an individual three-dimensional alignment target comprises a plurality of parallel trenches having a pitch larger than the specific wavelength, and
• wherein illuminating comprises illuminating the backside under an oblique angle relative to a plane defined by the wafer placed on the wafer stage and illuminating one of the individual three-dimensional alignment targets perpendicular to an orientation of trench walls of the plurality of parallel trenches.

An apparatus for aligning structures of a backside of a wafer to structures of a frontside of the wafer for a lithographic treatment of the backside, wherein the wafer is transparent for electromagnetic radiation of a specific wavelength, the apparatus comprising:

• alignment optics for capturing electromagnetic radiation from three-dimensional structures of individual three-dimensional alignment targets spaced apart from each other and located at the frontside or inside the wafer;
• a wafer stage for carrying the wafer such that the frontside is facing the wafer stage and the backside is facing the alignment optics;
• and
• a radiation source for illuminating the backside with electromagnetic radiation of the specific wavelength in a dark-field configuration, such that the electromagnetic radiation propagates through the wafer towards the three-dimensional structures of three-dimensional alignment targets located at the frontside or the inside the wafer and is scattered at the three-dimensional structures,
• wherein the structures of the backside can be aligned to the structures of the frontside of the wafer based on the scattered electromagnetic radiation captured with the alignment optics,
• wherein an individual three-dimensional alignment target comprise a plurality of parallel trenches having a pitch larger than the specific wavelength, and
• wherein the radiation source is configured to illuminate the backside under an oblique angle relative to a plane defined by the wafer placed on the wafer stage, and to illuminate one of the individual three-dimensional alignment targets perpendicular to an orientation of trench walls of the plurality of parallel trenches.

An apparatus for aligning structures of a backside of a wafer to structures of a frontside of the wafer for a lithographic treatment of the backside, wherein the wafer is transparent for infra-red light of a specific wavelength, the apparatus comprising:

• an infra-red camera for capturing infra-red light from three-dimensional structures of individual three-dimensional alignment targets spaced apart from each other and located at the frontside or inside the wafer;
• a wafer stage for carrying the wafer such that the frontside is facing the wafer stage and the backside is facing alignment optics;
• and
• an infra-red light source for illuminating the backside with infra-red light of the specific wavelength in a dark-field configuration, such that the infra-red light propagates through the wafer towards the three-dimensional structures of three-dimensional alignment targets located at the frontside or inside the wafer and is scattered at the three-dimensional alignment targets towards the infra-red camera,
• wherein the structures of the backside can be aligned to the structures of the frontside of the wafer based on the scattered infra-red light captured with the infra-red camera,
• wherein an individual three-dimensional alignment target comprise a plurality of parallel trenches having a pitch larger than the specific wavelength, and
• wherein the infra-red light source is configured to illuminate the backside under an oblique angle relative to a plane defined by the wafer placed on the wafer stage and to illuminate one of the individual three-dimensional alignment targets perpendicular to an orientation of trench walls of the plurality of parallel trenches.

A method for aligning structures of a backside of a wafer to structures of a frontside of the wafer, the method comprising:

• providing the wafer, the wafer having a backside facing alignment optics;
• illuminating the backside with electromagnetic radiation in a dark-field configuration, the wafer being transparent to the electromagnetic radiation, the electromagnetic radiation propagating through the wafer towards three-dimensional structures of individual three-dimensional alignment targets spaced apart from each other and located at the frontside or inside the wafer and scattering at the three-dimensional structures;
• and
• capturing the scattered electromagnetic radiation with the alignment optics,
• wherein an individual three-dimensional alignment target comprise a plurality of parallel trenches having a pitch larger than a wavelength of the electromagnetic radiation, and
• wherein illuminating comprises illuminating the backside under an oblique angle relative to a plane defined by the wafer and illuminating one of the individual three-dimensional alignment targets perpendicular to an orientation of trench walls of the plurality of parallel trenches.

A method for aligning structures of a backside of a wafer to structures of a frontside of the wafer, comprising:

• providing the wafer, the wafer having a backside facing alignment optics;
• illuminating the backside with infra-red light in a dark-field configuration, the wafer being transparent to the infra-red light, the infra-red light propagating through the wafer towards three-dimensional structures of individual three-dimensional alignment targets spaced apart from each other and located at the frontside or inside the wafer and scattering at the three-dimensional structures towards the backside;
• and
• capturing the scattered infra-red light with the alignment optics,
• wherein an individual three-dimensional alignment target comprise a plurality of parallel trenches having a pitch larger than a wavelength of the infra-red light, and
• wherein illuminating comprises illuminating the backside under an oblique angle relative to a plane defined by the wafer and illuminating one of the individual three-dimensional alignment targets perpendicular to an orientation of trench walls of the plurality of parallel trenches.

An apparatus for aligning structures of a backside of a wafer to structures of a frontside of the wafer, comprising:

• alignment optics for capturing electromagnetic radiation from three-dimensional structures of individual three-dimensional alignment target targets spaced apart from each other and located at the frontside or inside the wafer;
• a wafer stage for carrying the wafer such that the frontside is facing the wafer stage and the backside is facing the alignment optics;
• and
• a radiation source for illuminating the backside with electromagnetic radiation in a dark-field configuration, the wafer being transparent to the electromagnetic radiation, the electromagnetic radiation propagating through the wafer towards three-dimensional structures of a three-dimensional alignment target located at the frontside or inside the wafer and scattering at the three-dimensional structures,
• wherein the alignment optics is adapted to capture the scattered electromagnetic radiation,
• wherein an individual three-dimensional alignment target comprise a plurality of parallel trenches having a pitch larger than a wavelength of the electromagnetic radiation, and
• wherein the radiation source is configured to illuminate the backside under an oblique angle relative to a plane defined by the wafer placed on the wafer stage, and to illuminate one of the individual three-dimensional alignment targets perpendicular to an orientation of trench walls of the plurality of parallel trenches.

An apparatus for aligning structures of a backside of a wafer to structures of a frontside of the wafer, comprising:

• alignment optics for capturing infra-red light from three-dimensional structures of a three-dimensional alignment target located at the frontside or inside the wafer;
• a wafer stage for carrying the wafer such that the frontside is facing the wafer stage and the backside is facing the alignment optics;
• and
• a radiation source for illuminating the backside with infra-red light in a dark-field configuration, the wafer being transparent to the infra-red light, the infra-red light propagating through the wafer towards three-dimensional structures of individual three-dimensional alignment targets spaced apart from each other and located at the frontside or inside of the wafer and scattering at the three-dimensional structures towards the backside,
• wherein the alignment optics is adapted to capture the scattered infra-red light,
• wherein an individual three-dimensional alignment target comprise a plurality of parallel trenches having a pitch larger than a wavelength of the infra-red light, and
• wherein the radiation source is configured to illuminate the backside under an oblique angle relative to a plane defined by the wafer placed on the wafer stage, and to illuminate one of the individual three-dimensional alignment targets perpendicular to an orientation of trench walls of the plurality of parallel trenches.