Patent Number: 
Section: claims

1. A shielding assembly for a semiconductor device, comprising:a first shielding member disposed at an inner bottom surface of a chamber through which a high-energy ion beam passes, the bottom surface having a bottom magnetic area;a second shielding member disposed at a top surface of the chamber, the top surface having a top magnetic area, the second shielding member covering a portion of the top surface of the chamber, including the top magnetic area;a third shielding member disposed at a side surface in the chamber extending between the top and bottom surfaces of the chamber,wherein the first, second and third shielding members are jointed with one another in such a manner that an edge portion of the first shielding member contacts a bottom edge portion of the third shielding member and an edge portion of the second shielding member contacts a top edge portion of the third shielding member;a fourth shielding member for at least partially covering another portion of the top surface of the chamber in a side-by-side relationship with the second shielding member,wherein the second and fourth shielding members are jointed with one another in such a manner that an edge portion of the fourth shielding member contacts an adjacent edge portion of the second shielding member; anda support mechanism adapted for mounting in the chamber in a position such that the support mechanism supports the fourth shielding member in opposing relationship to the top surface of the chamber;wherein the support mechanism is configured to vary the tilt of the fourth shielding member relative to the top surface. 2. The assembly of claim 1, wherein the first, second, and third shielding members are assembled to cover respective surface areas of the chamber, so as to reduce accumulation of impurities on the surface areas while the chamber operates. 3. The assembly of claim 1, wherein the first, second, and third shielding members are made entirely of graphite or impregnated graphite. 4. The assembly of claim 1, wherein the first and second shielding members are substantially identical in size and shape. 5. The assembly of claim 1, wherein the support mechanism comprises a body and at least one adjusting bolt threadably received in the body, the bolt having an upper end positioned to support the fourth shielding member, the bolt being adjustable to vary the tilt of the fourth shielding member relative to the top surface. 6. The assembly of claim 1, wherein the edge portion of the fourth shielding member comprises a lip portion and the edge portion of the second shielding member comprises a lip portion, the lip portion of the fourth shielding member engaging the lip portion of the second shielding member such that the fourth shielding member is at least partially supported by the second shielding member. 7. The assembly of claim 6, wherein the lip portions of the second shielding member and the fourth shielding member define areas of reduced thickness of the second and fourth shielding members, the areas of reduced thickness being dimensioned such that the fourth shielding member is co-planar with the second shielding member when the shielding members are installed in the chamber. 8. The assembly of claim 1, wherein the body of the support mechanism is formed with a slot that is dimensioned to fit over a top edge of an existing plate in the chamber so as to support the support mechanism. 9. The assembly of claim 1, wherein the third shielding member is formed with an aperture that is sized and positioned to correspond with an ion-beam outlet in the chamber. 10. An ion implanting apparatus comprising the shielding assembly for a semiconductor device, as defined in claim 1.