Contact structure and forming method

• US 8,970,040 B1
• Filed: 09/26/2013
• Issued: 03/03/2015
• Est. Priority Date: 09/26/2013
• Status: Active Grant

• Current Assignee: Macronix International Co., Ltd.
• Original Assignee: Macronix International Co., Ltd.
• Inventors: Chen, Shih-Hung
• Primary Examiner(s): Pham, Hoai V
• Application Number:
  US14/038,526
• Publication Number:
  US 20150084203A1
• Time in Patent Office: 523 Days
• Field of Search: 257/211, 257/758, 257/759, 257/760, 257/E23.145
• US Class Current: 257/758
• CPC Class Codes: G11C 16/0483 comprising cells having several storage transistors connected in series
• CPC Class Codes: H01L 21/76805 the opening being a via or contact hole penetrating the underlying conductor
• CPC Class Codes: H01L 21/76816 Aspects relating to the layout of the pattern or to the size of vias or trenches layout of the interconnections per se H01L23/528; CAD of ICs G06F30/00
• CPC Class Codes: H01L 21/76831 in via holes or trenches, e.g. non-conductive sidewall liners
• CPC Class Codes: H01L 21/76838 characterised by the formation and the after-treatment of the conductors etching for patterning the conductors H01L21/3213
• CPC Class Codes: H10B 41/50 characterised by the boundary region between the core region and the peripheral circuit region
• CPC Class Codes: H10B 43/50 characterised by the boundary region between the core and peripheral circuit regions

Abstract

A method for forming a contact structure includes forming a stack of alternating active layers and insulating layers. The stack includes first and second sub stacks each with active layers separated by insulating layers. The active layers of each sub stack include an upper boundary active layer. A sub stack insulating layer is formed between the first and second sub stacks with an etching time different from the etching times of the insulating layers for a given etching process. The upper boundary active layers are accessed, after which the remainder of the active layers are accessed to create a stairstep structure of landing areas on the active layers. Interlayer conductors are formed to extend to the landing areas, the interlayer conductors separated from one another by insulating material.

Claims

1. A stairstep contact structure comprising:

a stack of alternating active layers and insulating layers having non-simple periods;

a stairstep structure of landing areas on the active layers; and

interlayer conductors extending to the landing areas, the interlayer conductors separated from one another by insulating material.

2. The stairstep contact structure according to claim 1, wherein the stack of alternating active layers and insulating layers comprises:

a first sub stack comprising N active layers separated by insulating layers, the N active layers comprising an upper boundary active layer;

a second sub stack over the first sub stack, the second sub stack comprising M active layers separated by insulating layers, the M active layers comprising an upper boundary active layer; and

a first sub stack insulating layer between the first and second sub stacks, the first sub stack insulating layer having an etching time different from the etching times of the insulating layers of the second sub stack for a given etching process.

3. The stairstep contact structure according to claim 2, wherein the stack comprises:

third and fourth sub stacks;

a second sub stack insulating layer between the second and third sub stacks;

a third sub stack insulating layer between the third and fourth sub stacks; and

wherein;

the insulating layers of the first, second, third and fourth sub stacks have substantially equal thicknesses and are made of a first insulating material;

the first, second and third sub stack insulating layers are made of a second, third and fourth insulating materials; and

at least two of the first, second, third and fourth insulating materials are of different insulating materials having different etching characteristics.

4. The stairstep contact structure according to claim 3, wherein:

the insulating layers of each of the first, second, third and fourth sub stacks have substantially equal etching times for a given etch process; and

each of the first, second and third sub stack insulating layers having an etching time different from the etching times of the insulating layers of the first, second, third and fourth sub stacks for the given etch process.

5. The stairstep contact structure according to claim 4, where the etching times for the first and third sub stack insulating layers are substantially equal for the given etch process.

6. The stairstep contact structure according to claim 1, wherein for the same etch process at least one of (1) the active layers have different etch times, or (2) the insulating layers have different etch times.