Disco Corporation

Yoko Nishino

Kazuya Hirata

Kunimitsu Takahashi

Hiroshi Morikazu

Keiji Nomaru

Tomoki Yoshino

Karl Heinz Priewasser

A hexagonal single crystal wafer is produced from a hexagonal single crystal ingot. A wafer producing method includes a separation start point forming step of applying a laser beam to the ingot to form a modified layer parallel to the upper surface of the ingot and cracks extending from the modified layer, thus forming a separation start point. The focal point of the laser beam is relatively moved in a first direction perpendicular to a second direction where a c-axis in the ingot is inclined by an off angle with respect to a normal to the upper surface. The off angle is formed between the upper surface and a c-plane perpendicular to the c-axis, thereby linearly forming the modified layer extending in the first direction. The laser beam is applied to the ingot with the direction of the polarization plane of the laser beam set to the first direction.

Wafer producing method

A hexagonal single crystal wafer is produced from a hexagonal single crystal ingot. The wafer producing method includes a separation start point forming step of setting the focal point of a laser beam having a transmission wavelength to the ingot inside the ingot at a predetermined depth from the upper surface of the ingot. The separation start point forming step includes a first step of forming the separation start point with a first power and a second step of setting the focal point at the modified layer previously formed in the first step and then applying the laser beam to the ingot with a second power higher than the first power at an increased repetition frequency in the condition where the energy per pulse of the laser beam is the same as that in the first step, thereby separating the cracks from the modified layer.

A wafer producing method for producing an SiC wafer from a single crystal SiC ingot. The wafer producing method includes a separation surface forming step of forming a separation surface composed of modified layers, cracks, and connection layers inside the ingot and a wafer separating step of separating a part of the ingot along the separation surface as an interface to thereby produce the wafer. The separation surface forming step includes a modified layer forming step of forming the modified layers and the cracks extending from the modified layers along a c-plane, and a connection layer forming step of forming the connection layers each connecting the cracks formed adjacent to each other in the thickness direction of the ingot.

Disclosed herein is a wafer thinning method for thinning a wafer formed from an SiC substrate having a first surface and a second surface opposite to the first surface. The wafer thinning method includes an annular groove forming step of forming an annular groove on the second surface of the SiC substrate in an annular area corresponding to the boundary between a device area and a peripheral marginal area in the condition where a thickness corresponding to the finished thickness of the wafer after thinning is left, and a separation start point forming step of applying the laser beam to the second surface as relatively moving a focal point and the SiC substrate to thereby form a modified layer and cracks inside the SiC substrate at the predetermined depth.

Wafer thinning method

Disclosed herein is a wafer producing method for producing a hexagonal single crystal wafer from a hexagonal single crystal ingot. The wafer producing method includes a modified layer forming step of setting the focal point of a laser beam having a transmission wavelength to the ingot inside the ingot at a predetermined depth from the upper surface of the ingot, which depth corresponds to the thickness of the wafer to be produced, and next applying the laser beam to the upper surface of the ingot as relatively moving the focal point and the ingot to thereby form a modified layer parallel to the upper surface of the ingot and cracks extending from the modified layer. In the modified layer forming step, the focal point of the laser beam is relatively moved from a radially inside position inside the ingot toward the outer circumference of the ingot.

Water producing method

A wafer is produced from an ingot having an end surface. The method includes an end surface measuring step of measuring undulation present on the end surface, and a separation plane forming step of setting the focal point of a laser beam inside the ingot at a predetermined depth from the end surface, which depth corresponds to the thickness of the wafer to be produced, and next applying the laser beam to the end surface to thereby form a separation plane containing a modified layer and cracks extending from the modified layer. The height of an objective lens for forming the focal point of the laser beam is controlled so that the focal point is set in the same plane to form the separation plane, according to the numerical aperture NA of the lens, the refractive index N of the ingot, and the undulation present on the end surface.

A crystal wafer is produced from a hexagonal crystal ingot. A separation start point is formed by setting the focal point of a laser beam inside the ingot at a predetermined depth, which depth corresponds to the thickness of the wafer to be produced. The laser beam is applied to the upper surface of the ingot while relatively moving the focal point and the ingot to form a modified layer parallel to the upper surface of the ingot and cracks extending from the modified layer along a c-plane in the ingot, thus forming the separation start point. First the laser beam is scanned from a scanning start point to a scanning end point on the ingot. Then the laser beam is scanned from the scanning end point to the scanning start point. The first and second steps are alternately repeated to separate the cracks from the modified layer.

A hexagonal single crystal wafer is produced from a hexagonal single crystal ingot. A separation start point is formed by setting a focal point of a laser beam inside the ingot at a predetermined depth from the upper surface of the ingot, which depth corresponds to a thickness of the wafer to be produced. The laser beam is applied to the upper surface of the ingot while relatively moving the focal point and the ingot to thereby form a modified layer parallel to the upper surface of the ingot and form cracks extending from the modified layer along a c-plane, thus forming a separation start point. The wafer is separated by immersing the ingot in water and then applying ultrasonic vibration to the ingot, thereby separating a plate-shaped member having a thickness corresponding to the thickness of the wafer from the ingot.

A wafer formed from an SiC substrate having a first surface and a second surface is divided into individual device chips. A division start point formed by a laser has a depth corresponding to the finished thickness of each device chip along each division line formed on the first surface. The focal point of the laser beam is set inside the SiC substrate at a predetermined depth from the second surface, and the laser beam is applied to the second surface while relatively moving the focal point and the SiC substrate to thereby form a modified layer parallel to the first surface and cracks extending from the modified layer along a c-plane, thus forming a separation start point. An external force is applied to the wafer, thereby separating the wafer into a first wafer having the first surface and a second wafer having the second surface.

Wafer processing method

Disclosed herein is an SiC ingot slicing method including: an initial separation layer formation step for scanning a focal point of a laser beam parallel to an end face of the SiC ingot along a scheduled separation plane, and forming a separation layer at a position at a distance from the end face; a repetition step for sequentially moving, after the initial separation layer formation step, the focal point by the distance equal to the thickness of an SiC plate from the separation layer toward the end face, scanning the focal point parallel to the end face, repeating the formation of the separation layer, and forming the plurality of separation layers; and a separation step for applying an external force to the plurality of separation layers formed by the repetition step, peeling off the SiC plates starting from the separation layers, and acquiring the plurality of SiC plates.

SiC ingot slicing method

A hexagonal single crystal wafer is produced from a hexagonal single crystal ingot. The wafer producing method includes a separation start point forming step of setting the focal point of a laser beam to the inside of the ingot at a predetermined depth from the upper surface of the ingot, which depth corresponds to the thickness of the wafer to be produced, and next applying the laser beam to the upper surface of the ingot while relatively moving the focal point and the ingot to thereby form a modified layer parallel to the upper surface of the ingot and cracks extending from the modified layer, thus forming a separation start point. A plate-shaped member having a thickness corresponding to the thickness of the wafer is separated from the ingot at the separation start point after performing the separation start point forming step, thus producing the wafer from the ingot.

There is provided a polycrystalline SiC wafer producing method. In this method, in a modified layer forming step for forming an interface for producing a polycrystalline SiC wafer from a polycrystalline SiC ingot, the formed interface is a surface formed by linking of modified layers formed in such a manner that an initial modified layer is formed through splitting of polycrystalline SiC into amorphous silicon and amorphous carbon at the light focus point of a pulse laser beam and then polycrystalline SiC splits into amorphous silicon and amorphous carbon at a position at which the power density is constant with absorption of the continuously-emitted pulse laser beam by amorphous carbon formed in advance.

Polycrystalline SiC wafer producing method

A wafer producing method for producing a hexagonal single crystal wafer from a hexagonal single crystal ingot includes a separation start point forming step of setting the focal point of a laser beam inside the ingot at a predetermined depth from the upper surface of the ingot, which depth corresponds to the thickness of the wafer to be produced, and next applying the laser beam to the upper surface of the ingot while relatively moving the focal point and the ingot to thereby form a modified layer parallel to the upper surface of the ingot and cracks extending from the modified layer, thus forming a separation start point. In the separation start point forming step, the laser beam is applied to the ingot plural times with the focal point of the laser beam set at the modified layer previously formed, thereby separating the cracks from the modified layer.

A wafer producing method for producing a hexagonal single crystal wafer from a hexagonal single crystal ingot is disclosed. The wafer producing method includes a separation start point forming step of forming a modified layer parallel to the upper surface of the ingot and cracks extending from the modified layer to thereby form a separation start point in the ingot. The separation start point forming step includes a first separation start point forming step of setting the focal point of a laser beam at a first depth which is N times (N is an integer not less than 2) the depth corresponding to the thickness of the wafer from the upper surface of the ingot and next applying the laser beam to the ingot to thereby form a first separation start point composed of a first modified layer and first cracks extending therefrom.

A wafer producing method produces a hexagonal single crystal wafer from a hexagonal single crystal ingot. The method includes a separation start point forming step of setting the focal point of a laser beam to the inside of the ingot at a predetermined depth from the upper surface of the ingot, which depth corresponds to the thickness of the wafer to be produced, and next applying the laser beam to the upper surface of the ingot while relatively moving the focal point and the ingot to thereby form a modified layer parallel to the upper surface of the ingot and cracks extending from the modified layer, thus forming a separation start point. The separation start point forming step includes an indexing step of relatively moving the focal point in a direction of formation of an off angle to thereby index the focal point by a predetermined index amount.

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Tokyo, Japan

Yoko Nishino