# US 2016/0252565 A1 · Non-contact method to monitor and quantify effective work function of metals

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- Number: US 2016/0252565 A1
- Document ID: US20160252565A1
- Status: Published application
- Kind: A1
- Application number: 15/055,062
- Filed: 2016-02-26
- Published: 2016-09-01
- Earliest claimed: 2015-02-27
- Assignees: Semilab SDI LLC
- Applicants: Semilab SDI LLC
- Inventors: Dmitriy Marinskiy; Thye Chong Loy; Jacek Lagowski; Sung-Li Wang; Lin-Jung Wu; Shyh-Shin Ferng; Yi-Hung Lin; Sheng-Shin Lin
- Web page: https://patentgrep.com/patent/US20160252565A1

## CPC

- H10P 74/207: {Electrical properties, e.g. testing or measuring of resistance, deep levels or capacitance-voltage characteristics}
- G01R 31/2621: {for testing field effect transistors, i.e. FET's}
- G01R 31/2623: {for measuring break-down voltage therefor}
- G01R 31/2625: {for measuring gain factor thereof}
- G01R 31/2626: {for measuring noise (measuring noise factor in general G01R29/26)}
- G01R 31/2628: {for measuring thermal properties thereof}
- G01R 31/2656: {using non-ionising electromagnetic radiation, e.g. optical radiation}
- G01R 31/2831: {Testing of materials or semi-finished products, e.g. semiconductor wafers or substrates (G01R31/318511 takes precedence; testing during manufacture H10P74/00)}
- G01N 17/00: Investigating resistance of materials to the weather, to corrosion, or to light
- H10P: GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10
- G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12)
- G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q)

## Abstract

An example semiconductor wafer includes a semiconductor layer, a dielectric layer disposed on the semiconductor layer, and a layer of the metal disposed on the dielectric layer. An example method of determining an effective work function of a metal on the semiconductor wafer includes determining a surface barrier voltage of the semiconductor wafer, and determining a metal effective work function of the semiconductor wafer based, at least in part, on the surface barrier voltage.

## Claims

### Claim 1

A method of determining an effective work function of a metal on a semiconductor wafer, the semiconductor wafer comprising a semiconductor layer, a dielectric layer disposed on the semiconductor layer, and a layer of the metal disposed on the dielectric layer, the method comprising:
determining a surface barrier voltage of the semiconductor wafer; and
determining a metal effective work function of the semiconductor wafer based, at least in part, on the surface barrier voltage.

### Claim 2 (depends on 2)

The method of claim 2, where determining the surface barrier voltage of the semiconductor wafer comprises:
measuring a first surface voltage of the metal layer while the metal layer is illuminated; and
measuring a second surface voltage of the metal layer while the metal layer is not illuminated.

### Claim 3 (depends on 2)

The method of claim 2, wherein the surface barrier voltage corresponds to the second surface voltage minus the first surface voltage.

### Claim 4 (depends on 2)

The method of claim 2, wherein the first and second surface voltages are measured using a Kelvin probe.

### Claim 5 (depends on 2)

The method of claim 2, wherein the first and second surface voltages are measured using a capacitor probe.

### Claim 6 (depends on 2)

The method of claim 2, wherein measuring a first surface voltage of the metal layer while the metal layer is illuminated comprises:
illuminating the metal layer with photon energy larger than an energy gap of the semiconductor layer.

### Claim 7 (depends on 2)

The method of claim 2, wherein the metal film is transparent to the illumination, and
wherein measuring a first surface voltage of the metal layer while the metal layer is illuminated comprises directing illumination upon the metal layer of the wafer.

### Claim 8 (depends on 2)

The method of claim 2, wherein the metal film is opaque to the illumination, and wherein measuring a first surface voltage of the metal layer while the metal layer is illuminated comprises directing illumination upon the substrate layer of the wafer.

### Claim 9 (depends on 1)

The method of claim 1, wherein the surface barrier voltage is proportional of the metal effective work function.

### Claim 10 (depends on 1)

The method of claim 1, wherein the metal effective work function of the semiconductor wafer is determined, based at least in part, on a bulk work function of the semiconductor layer.

### Claim 11 (depends on 10)

The method of claim 10, wherein the metal effective work function is determined using the relationship EWF=ΦS−qVSB, where EWF is the metal effective work function, ΦS is the bulk work function of the semiconductor layer, VSB is the surface barrier voltage of the wafer, and q is a charge of an electron.

### Claim 12 (depends on 11)

The method of claim 11, wherein determining the surface barrier voltage of the semiconductor wafer comprises determining a spatially dependent map of the surface barrier voltage along a surface of the semiconductor wafer; and
wherein determining a metal effective work function of the semiconductor wafer is based, at least in part, on the spatially dependent map.

### Claim 13

A system comprising:
a probe for determining a surface barrier voltage of a semiconductor wafer, the semiconductor wafer comprising a substrate layer, a dielectric layer, and a metal layer;
one or more processors; and
non-transitory memory storing instructions, which, when executed by the one or more processors, causes the one or more processors to determine a metal effective work function of the semiconductor wafer based, at least in part, on the surface barrier voltage.