| 摘要 |
PURPOSE:To prevent each grid electrode from being warped by providing a pair of implantation blocks which are deeply implanted into an insulating support body at the central part on both sides of the first or second grid electrode and a low step blocks which are shallowly retained in the insulating support body on both sides of the implantation blocks. CONSTITUTION:A pair of implantation blocks 44a and 44b implanted into an insulating support body are provided at the central part on both sides of the support body 43a of the first or second grid electrode 43 and low step blocks 45a, 45b, 45c, and 45d are provided on both sides of these implantation blocks 44a and 44b. When the implantation blocks 44a and 44b are implanted into the insulating support body, these low step blocks are retained more shollowly than these implantation blocks and the width of the insulating support body is made narrower than the outer width 46 of the low step blocks. For the expansion of the grid electrode dimensions by thermal expansion, this permits the low step blocks to slide along with the insulating support body centering around the implantation blocks and to escape in the width direction on the sides. As the result, the implantation blocks can hold only one fixed point and the grid electrode can be prevented from being warped. |
