An apparatus for adhering two substrates to each other comprising a rotatable plate member having a side portion, a flat top portion and fitted with an axis of rotation, a side of the plate member turned toward a first of the two substrates has a radially outer plane portion in the form of a disk concentric to its axis of rotation, which defines a plane of application of the first substrate, and a radial inner portion adjacent to the outer plane portion where the face of this inner portion turned toward the substrate is formed by the outer face of a flat, straight frustum of a cone whose peak strikes the axis of rotation below the plane of application of the first substrate to thereby define a conical portion having a conical face,
- where in a transitional area from the outer plane portion to the conical portion an annular groove running coaxially to the axis of rotation is cut into the plate member which on one side of the plate member is connected to a pressure source via channels running in the plate member and on another side of the plate member, teardrop or finger shaped indentations or recesses are provided in the conical face extending from the annular groove radially inward,
- where the diameter and the depth of the annular groove are approximately dimensioned so that they correspond to an annular protuberance of the first substrate.