The impact of the emitter polysilicon etching in Tetramethyl Ammonium Hydroxide (TMAH) on the characteristics of high-linearity mixers fabricated with the low-cost Horizontal Current Bipolar Transistor (HCBT) is analyzed. During emitter formation, the thick layer of α-Si is deposited over the whole wafer, which is then etched-back in the TMAH. The emitter thickness depends on the TMAH etching time and impacts the HCBT's electrical characteristics. Active down-converting mixers with open-collector topology based on Gilbert cell are fabricated with two types of HCBTs with different TMAH etching time using the lowest-cost HCBT technology with CMOS n-well region for n-collector. Measurements of mixers' characteristics are done on-wafer by using the multi-contact probes. The mixers achieve maximum IIP3 of 20.2 dBm and conversion gain of 4 dB. Differences in performance characteristics between two mixer types are small indicating that HCBT's circuit performance sensitivity on the emitter thickness variations is relatively small.