Model for accurate photoresist profile prediction

Patent metadata

Field	Value
Publication number	US-9733576-B2
Application number	US-201414220446-A
Country	US
Kind code	B2
Filing date	Mar 20, 2014
Priority date	Mar 17, 2014
Publication date	Aug 15, 2017
Grant date	Aug 15, 2017

Abstract

A photoresist modelling system includes a mathematical model for a photolithography process. The mathematical model may be executable using a computer processor. The mathematical model may be used to model a photoresist as formed on a semiconductor wafer surface. A blocked polymer concentration gradient equation may be implemented into the mathematical model. The blocked polymer concentration gradient equation may describe an initial concentration gradient of a blocked polymer in the photoresist being modelled by the mathematical model.

First claim

What is claimed is:

1. A photoresist modelling system, comprising:
a computer comprising a processor;
a memory coupled to the processor and storing one or more program instructions executable by the processor to:
provide one or more process parameters for a photolithography process to a mathematical model stored in the program instructions, the photolithography process being used to form a photoresist on a semiconductor wafer surface, wherein the photoresist comprises at least one blocked polymer, and wherein at least one of the process parameters comprises a blocked polymer concentration in the photoresist;
implement the mathematical model for the photolithography process, wherein the mathematical model is used to model the photoresist formed on the semiconductor wafer surface using the photolithography process, wherein a blocked polymer concentration gradient equation is implemented into the mathematical model, and wherein the blocked polymer concentration gradient equation describes a concentration gradient of a blocked polymer in the photoresist being modelled by the mathematical model, the blocked polymer concentration gradient equation describing the concentration gradient of the blocked polymer as a function of distance from an interface of the photoresist and the semiconductor wafer surface, a fraction of concentration reduction, and a depth of the reduction; and
assess the modelled photoresist profile of the photoresist being formed on the semiconductor wafer surface; and
control a photoresist profile of the photoresist as it is being formed on the semiconductor wafer surface by adjusting one or more process parameters of the photolithography process based on the assessment of the modelled photoresist profile.

2. The system of claim 1 , wherein the blocked polymer concentration gradient equation describes an initial concentration gradient of the blocked polymer in the photoresist.

3. The system of claim 1 , wherein the blocked polymer concentration is adjusted to a selected value of a bulk concentration of the blocked polymer at an interface of the photoresist.

4. The system of claim 3 , wherein the selected value is between about 20 percent and about 40 percent below the bulk concentration of the blocked polymer.

5. The system of claim 1 , wherein the blocked polymer concentration gradient equation describes an increased blocked polymer concentration near a surface of the photoresist, and wherein the blocked polymer concentration decreases as concentration moves into the photoresist.

6. The system of claim 1 , wherein the blocked polymer concentration gradient equation describes the concentration gradient of a blocked polymer in the photoresist as an exponential function.

7. The system of claim 1 , wherein the blocked polymer concentration gradient equation comprises the equation:
M =( R− 1) e −z/σ +1;

wherein M is the blocked polymer concentration, R is the fraction of concentration reduction, σ the depth of the reduction, and z is the distance from the interface.

8. A method for modelling a photoresist cross-sectional profile, comprising:
providing one or more process parameters for a photolithography process to a mathematical model executed using a computer processor, the photolithography process being used to form a photoresist on a semiconductor wafer surface, wherein the photoresist comprises at least one blocked polymer, and wherein at least one of the process parameters comprises a blocked polymer concentration in the photoresist;
modelling, using the computer processor, a photoresist profile of the photoresist being formed on the semiconductor wafer surface using the mathematical model, wherein the mathematical model includes a blocked polymer concentration gradient equation, and wherein the blocked polymer concentration gradient equation describes a concentration gradient of a blocked polymer in the photoresist being modelled by the mathematical model, the blocked polymer concentration gradient equation describing the concentration gradient of the blocked polymer as a function of distance from an interface of the photoresist and the semiconductor wafer surface, a fraction of concentration reduction, and a depth of the reduction;
assessing, using a computer processor, the modelled photoresist profile of the photoresist being formed on the semiconductor wafer surface; and
controlling a photoresist profile of the photoresist as it is being formed on the semiconductor wafer surface by adjusting, using a computer processor, one or more process parameters of the photolithography process based on the assessment of the modelled photoresist profile.

9. The method of claim 8 , wherein the blocked polymer concentration gradient equation describes an initial concentration gradient of the blocked polymer in the photoresist.

10. The method of claim 8 , further comprising adjusting the blocked polymer concentration to a selected value of a bulk concentration of the blocked polymer at an interface of the photoresist.

11. The method of claim 10 , wherein the selected value is between about 20 percent and about 40 percent below the bulk concentration of the blocked polymer.

12. The method of claim 8 , wherein the blocked polymer concentration gradient equation describes the concentration gradient of a blocked polymer in the photoresist as an exponential function.

13. The method of claim 8 , wherein the blocked polymer concentration gradient equation comprises the equation:
M =( R− 1) e −z/σ +1;

wherein M is the blocked polymer concentration, R is the fraction of concentration reduction, σ is the depth of the reduction, and z is the distance from the interface.

14. A non-transitory computer readable storage medium including program instructions executable by a processor to:
provide one or more process parameters for a photolithography process to a mathematical model, the photolithography process being used to form a photoresist on a semiconductor wafer surface, wherein the photoresist comprises at least one blocked polymer, and wherein at least one of the process parameters comprises a blocked polymer concentration in the photoresist;
form a photoresist profile for the photoresist on the semiconductor wafer surface using the mathematical model for the photolithography process stored in the program instructions, wherein the mathematical model includes a blocked polymer concentration gradient equation, and wherein the blocked polymer concentration gradient equation describes a concentration gradient of a blocked polymer in the photoresist being modelled by the mathematical model, the blocked polymer concentration gradient equation describing the concentration gradient of the blocked polymer as a function of distance from an interface of the photoresist and the semiconductor wafer surface, a fraction of concentration reduction, and a depth of the reduction;
assessing the photoresist profile of the photoresist formed on the semiconductor wafer surface by the mathematical model; and
controlling a photoresist profile of the photoresist as it is being formed on the semiconductor wafer surface by adjusting one or more process parameters of the photolithography process based on the assessment of the photoresist profile formed on the semiconductor wafer surface by the mathematical model.

15. The computer readable storage medium of claim 14 , wherein the blocked polymer concentration gradient equation describes an initial concentration gradient of the blocked polymer in the photoresist.

16. The computer readable storage medium of claim 14 , further comprising adjusting the

Assignees

• Kla Tencor Corp

Inventors

• Smith Mark Davis
• Biafore John

Classifications

• G03F7/705 Primary

  Modelling or simulating from physical phenomena up to complete wafer processes or whole workflow in wafer productions · CPC title

• G03F7/0392

  the macromolecular compound being present in a chemically amplified positive photoresist composition · CPC title

• G03F7/70625

  Dimensions, e.g. line width, critical dimension [CD], profile, sidewall angle or edge roughness · CPC title

• G03F7/70525

  Controlling normal operating mode, e.g. matching different apparatus, remote control or prediction of failure · CPC title

• H10P74/203

  Structural properties, e.g. testing or measuring thicknesses, line widths, warpage, bond strengths or physical defects · CPC title