**5. The first DC ribbon-beam architecture**

Moore's Law predicted rapid scaling up of the number of devices on a single chip, and this required several developments: higher currents at lower energies (as devices became smaller), larger silicon wafers, moving to 200 mm diameter in the 1980s, better control of beam angles, and a strong preference for serial wafer processing to avoid the inefficiencies of processing in fixed-size batches. Serial processing was used in most semiconductor manufacturing processes, but high-current implantation still processed wafers in batches, resulting in higher costs. Applied Materials had acquired Lintott Engineering Ltd. In 1980, and in '85 was manufacturing a somewhat successful batch high current implanter, the PI 9000, but as larger wafer sizes were considered, the future looked uncertain. Applied's other semiconductor tools all used serial processing.

The ASM 220 medium-current ion implanter used a horizontally scanned beam which was rendered parallel by means of a non-uniform magnet bending on average about 10 degrees [8, 9]. A single wafer was scanned mechanically through this beam in the vertical direction, to achieve uniform doping. This technique provided unprecedented angle control between beam and the wafer, excellent uniformity, and high efficiency (**Figure 2**).

In conjunction with marketing and technical colleagues at Applied Materials, White in 1989 proposed (a) the acquisition of the ASM implanter division, and (b) the development of a serial-process high-current implanter using a wide DC ribbon beam [10], with a similar mechanical wafer scan mechanism to the ASM 220; and the two implanters would be complementary for medium and high-dose applications, at least on 200 mm wafers. We anticipated that the next silicon wafer size would be 300 mm, and we sized our high-current proposal for a 330 mm wide beam. Applied Materials did not agree to these plans, and as a result, Diamond Semiconductor Group (DSG) was founded in 1991, with a mission of developing such an implanter.

In that intervening two-year interval, as described above, White and Gray Morgan had experimentally confirmed the scaling laws of the beam instability problem [7]. DSG concluded that the use of a convergent slit on the front of the ion source raised the ion density within the analyzing magnet above the threshold for beam instability at those beam currents and energies which the market desired. DSG's goals now included
