Chemically sensitive sensor with lightly doped drains

• US 9,960,253 B2
• Filed: 02/12/2014
• Issued: 05/01/2018
• Est. Priority Date: 07/03/2010
• Status: Active Grant

• Current Assignee: Life Technologies Corporation (Thermo Fisher Scientific Incorporated)
• Original Assignee: Life Technologies Corporation (Thermo Fisher Scientific Incorporated)
• Inventors: Fife, Keith G.
• Primary Examiner(s): YEUNG LOPEZ, FEIFEI
• Application Number:
  US14/179,453
• Publication Number:
  US 20140193938A1
• Time in Patent Office: 1,539 Days
• CPC Class Codes: G01N 27/414 Ion-sensitive or chemical field-effect transistors, i.e. ISFETS or CHEMFETS
• CPC Class Codes: G01N 27/4145 specially adapted for biomolecules, e.g. gate electrode with immobilised receptors
• CPC Class Codes: H01L 29/6659 with both lightly doped source and drain extensions and source and drain self-aligned to the sides of the gate, e.g. lightly doped drain [LDD] MOSFET, double diffused drain [DDD] MOSFET
• CPC Class Codes: H01L 29/788 with floating gate H01L29/78391 takes precedence
• CPC Class Codes: H10B 41/00 Electrically erasable-and-programmable ROM [EEPROM] devices comprising floating gates

Abstract

A chemically sensitive sensor with a lightly doped region that affects an overlap capacitance between a gate and an electrode of the chemical sensitive sensor. The lightly doped region extends beneath and adjacent to a gate region of the chemical sensitive sensor. Modifying the gain of the chemically sensitive sensor is achieved by manipulating the lightly doped region under the electrodes.

Claims

1. A method of making a chemically sensitive sensor, comprising:

forming a substrate with a first conductivity type of dopant;

building an epitaxial layer using the same conductivity type dopant used to form the substrate, but made less dense than the dopant on the substrate;

forming an electrode layer on the epitaxial layer formed from a different, second conductivity type of dopant than the first conductivity type of dopant used to form the substrate, wherein the density of dopant on both the electrode layer and the substrate are similar;

masking and etching the electrode layer to produce gates and corresponding electrode pairs;

creating a first lightly doped region adjacent to one electrode of each of the electrode pairs using a multidirectional implant technique, wherein the first lightly doped region is formed from a dopant of a conductivity type opposite the epitaxial layer dopant;

producing diffusion nodes that are self-aligned with the electrode pairs, a first of said diffusion nodes contiguous with the first lightly doped region, from a dopant of a conductivity type similar to the gates, electrode pairs, and lightly doped region; and

forming a floating gate electrode, and contacts for the electrode pairs by alternating layers of insulation, dielectric, conductive and metal layers.

2. The method of claim 1, further comprising:

creating a second lightly doped region adjacent to the other electrode of each of the electrode pairs using a multidirectional implant technique, wherein the second lightly doped region is formed from a dopant of a conductivity type opposite the epitaxial layer dopant.

3. The method of claim 1, wherein a second of said diffusion nodes is contiguous with a second lightly doped region.

4. The method of claim 1, further comprising:

forming an additional electrode on the diffusion nodes.

5. The method of claim 1, further comprising:

forming a microwell to hold a sample above the floating gate.