Method of fabricating grayscale mask using smart cut® wafer bonding process

A method of fabricating a grayscale mask, comprising:

• preparing a silicon wafer;
• depositing a layer of Si3N4 directly on the silicon wafer;
• implanting H+ ions into the silicon wafer to form a defect layer;
• depositing a first layer of a transparent metal oxide directly on the Si3N4 layer;
• depositing a layer of SRO directly on the first layer of transparent metal oxide
• patterning a microlens array on the SRO layer;
• etching the SRO layer to form a microlens array in the SRO layer;
• photo reversing the microlens array;
• depositing a second layer of a transparent metal oxide on the SRO microlens array, wherein a refractive index of the second transparent metal oxide layer is matched to a refractive index of the SRO, so that the reflection at the transparent metal oxide/SRO interface is minimized;
• CMP to planarize the second layer of transparent metal oxide;
• bonding the planarized transparent metal oxide to a quartz plate to form a graymask reticle;
• cleaving the silicon wafer along the defect layer;
• etching to remove silicon from the bonded structure;
• etching to remove transparent metal oxide and Si3N4 from the bonded structure;
• and
• cleaning and drying the graymask reticle.

A method of fabricating a grayscale mask, comprising:

• preparing a silicon wafer;
• depositing a layer of Si3N4 directly on the silicon wafer;
• implanting H+ ions into the silicon wafer to form a defect layer;
• depositing a first layer of SiOxNy directly on the Si3N4 layer;
• depositing a layer of SRO directly on the first layer of SiOxNy, wherein refractive indices of the first SiOxNy layer and the SRO layer are matched so that reflection and refraction are minimized at the SRO/SiOxNy interface;
• patterning a microlens array on the SRO layer;
• etching the SRO layer to form a microlens array in the SRO layer;
• depositing a second layer of SiOxNy on the SRO microlens array;
• CMP to planarize the second layer of SiOxNy;
• bonding the planarized SiOxNy to a quartz plate to form a graymask reticle;
• cleaving the silicon wafer along the defect layer;
• etching to remove silicon from the bonded structure;
• etching to remove SiOxNy and Si3N4 from the bonded structure;
• and
• cleaning and drying the graymask reticle.