Method of isolating active areas of a semiconductor substrate by shallow trenches and narrow trenches
AssigneeFrance Telecom
InventorsMaryse Paoli, Pierre Brouquet, Michel Haond
Life of this patent
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Abstract
The semiconductor device includes in a semiconductor substrate (1) at least one predetermined region (6) of the substrate intended subsequently to form an active area, uncovered on its upper surface and situated between lateral trenches (7) containing an insulative material including a layer (9) of a planarising first oxide and at least one underlying layer (8) of a conformal second oxide. The insulative material can form on either side of said uncovered predetermined region (6) of the substrate a boss (16) on the plane upper surface of the device (D) less than 1000 .ANG. high.
Claims14
Method of isolating active areas of a semiconductor substrate with lateral trenches, comprising:
- a) trenches are formed in the semiconductor substrate laterally of first regions of the substrate which subsequently form said active areas,
- b) a layered structure is deposited in the trenches and on said first regions of the substrate, comprising a layer of a planarising insulative first oxide between two layers of a conformal second oxide to form a semiconductor block,
- c) the semiconductor block formed in step b) is annealed, and
- d) the annealed semiconductor block is planarised to uncover the upper surface of said first regions of the substrate and to leave in the trenches the conformal oxide and the planarising oxide.
Method of isolating active areas of a semiconductor substrate with lateral trenches, comprising:
- a) trenches are formed in the semiconductor substrate laterally of first regions of the substrate which subsequently form said active areas,
- b) a layered structure is deposited in the trenches and on said first regions of the substrate, comprising a layer of a planarising insulative first oxide between two layers of a conformal second oxide to form a semiconductor block,
- c) the semiconductor block formed in step b) is annealed, and
- d) the annealed semiconductor block is planarised to uncover the upper surface of said first regions of the substrate and to leave in the trenches the conformal oxide and the planarising oxide, wherein said trenches have a lateral dimension (L) and a depth (P) and in step b), to form said layered structure, there are deposited a first conformal oxide layer having a thickness chosen according to the minimal lateral dimension (L) of the trenches, then the planarising insulative first oxide layer having a thickness chosen to obtain a relief variation less than a first threshold for the trenches of minimal lateral dimension, and finally a second conformal oxide layer having a thickness chosen according to the depth (P) of the trench.
Dependencies are inferred from the claim text.