论文部分内容阅读
军事上主要考虑的三个辐照问题是:1)电离剂量极限;2)电离剂量率极限;3)中子通量极限。χ-射线与γ-射线产生从源到漏的光电流。剂量率达到10~8～10~8拉德/秒就足以改变MOS器件的逻辑状态。器件要辐照加固就必须承受10~8拉德/秒以上的剂量率。而χ-针线和γ-射线消失时,光电流立即停止。χ-射线和γ-射线除产生光电流外,还能使电荷波俘获在栅极氧化层中。射线连续轰击时,这种电荷是累积的。电荷的俘获引起MOS器件门槛电压变高。对多数MOS器件,大约10~4拉德的剂量就使门槛电压迅速变化。器件认为是真正加固时,其电离剂量极限要达到10~8拉德的量级,也就是说,除非总剂量超过10~8拉德,否则门槛电压不会有大幅度改变。这些辐照剂量数值是约略的,随着器件、材料与工艺结构的不同面有所变化。
The three major radiation issues considered in the military are: 1) the ionization dose limit; 2) the ionization dose rate limit; and 3) the neutron flux limit. X-rays and gamma rays produce photocurrent from source to drain. Dosage rate of 10 ~ 8 ~ 10 ~ 8 rad / sec is enough to change the logic state of MOS devices. Devices to be reinforced by radiation must withstand the dose rate of 10 ~ 8 rad / sec above. When χ-needle and γ-ray disappear, photocurrent stops immediately. In addition to generating photocurrents, x-rays and gamma rays trap charge waves in the gate oxide. This charge is cumulative when the beam is bombarded continuously. Charge trapping causes the MOS device threshold voltage to go high. For most MOS devices, a dose of about 10 to 4 rads causes the threshold voltage to change rapidly. The device is considered to be truly reinforced, the ionization dose limit to reach the level of 10 to 8 Ladd, that is, unless the total dose of more than 10 to 8 Ladd, or the threshold voltage will not have a significant change. These radiation dose values are approximate and vary depending on the device, material, and process structure.