Surface PIN device

#1. Field of the Invention

#The invention relates to semiconductor devices and, more particularly, the invention relates to a surface PIN device and a method of manufacturing same.

#2. Description of the Related Art

#So that the manner in which the above recited features, of the present invention are attained and can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to the embodiments thereof which are illustrated in the appended drawings.

#It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.

#FIG. 1 depicts a perspective view of a SPIN device;

#FIG. 1 depicts a surface PIN (SPIN) device 100 comprising a silicon substrate 102, an oxide layer 104, and intrinsic layer 106, a P+ region 108, an N+ region 110, and metal contacts 112 and 114. The P+ region 108 is separated from the N+ region 110 by a portion 116 of intrinsic material having a length L. The length L of portion 116 is approximately the carrier diffusion length. By selecting the length L as approximately the carrier diffusion length, the carrier density in the intrinsic region will be at least 1018 carriers per cm3. This is sufficient to cause the surface 118 of portion 116 to become conductor-like.

#The carrier diffusion length is the square root of the carrier lifetime multiplied by the diffusion constant. For example, the carrier lifetime is approximately 5 microseconds and the diffusion constant is approximately 35 cm2/sec. As such, a conservative estimate of the length L is 100 micrometers. For higher carrier density, the diffusion length is lower. The thickness of the intrinsic layer is approximately 50 micrometers. Such a thickness confines the carriers to the surface of the intrinsic region. In a reconfigurable antenna application for the SPIN device that is described in detail in U.S. patent application Ser. No. 09/812,701, filed simultaneously herewith and incorporated herein by reference, the thickness T is approximately three times the skin depth for the frequency being received/radiated by the antenna.

#The metal contact pads 112 and 114 are relatively small, e.g., one-tenth of the length L. Such a small size for the contact pads makes the SPIN device electrically invisible when the device is not activated.