| 摘要 |
1283133 Semi-conductor devices TOKYO SHIBAURA ELECTRIC CO Ltd 19 June 1970 [19 June 1969] 29958/70 Heading HlK In an NPN transistor the emitter region is formed by diffusion of As and the base region is formed at least in part by ion implantation. This combination is said to eliminate the emitter dip effect. In a first embodiment, Fig. 1H, an N-type layer (11) is epitaxially deposited on an N+- type Si substrate (10) and covered with a layer (13) of 5i0 2 formed by reaction of SiH 4 with O 2 . The oxide layer is photomasked and etched and a layer of Si0 2 containing B is deposited and the wafer heated to diffuse-in the B to form part (17) of a base contact guard ring. The oxide layer within the outer periphery of the ring is removed and a second layer 19 of 5i0 2 containing B is deposited, an emitter stripe window is formed above the opening of the previously diffused ring, and the wafer is heated to diffuse-in the B to form a shallower extension of the base contact guard ring 21. The wafer is then sealed in a quartz tube together with Si crystals doped with As and heated to form the diffused emitter stripe 22. The thin active part 23 of the base region below the emitter region is formed by implanting B ions through the emitter diffusion window and the wafer is annealed. Base and emitter electrodes 25, 26 are applied through openings formed in the layer 19. Although only a single emitter region is shown, in a practical arrangement, Fig. 2 (not shown), a plurality of parallel emitter stripes are provided, the base contact guard ring being in the form of a grid. In a modification, Fig. 3 (not shown), the active part of the base region is formed by ion implantation through the emitter window and the wafer is annealed before the emitter diffusion is performed. It is stated that the emitter dip effect is avoided by the use of As for the emitter diffusion. The base contact guard ring may be formed by gas phase diffusion and the acceptor impurities may be Al or Ga instead of B. The masking material may also be Si 3 N 4 or a metal. In another embodiment, Fig. 4 (not shown), the base region is diffused completely across the openings in the base guard ring, an oxide layer is applied, As is diffused through a window to form the emitter region, and B ions are implanted through the emitter window to enhance the active part of the base region. The ion implantation may be performed before the emitter diffusion. In a further embodiment, after forming the base contact guard ring the surface is covered with an oxide layer which is processed to form the emitter window surrounded by a thin portion of the oxide layer. B ions are then implanted through the window and also through the thin portion of the layer to complete the base region. Reference has been directed by the Comptroller to Specification 1,228,754.
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