Backside Rapid Thermal Processing for Wafer Temperature Uniformity

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Solution Overview

Problem

Current rapid thermal processing (RTP) technologies face challenges in achieving uniform temperature distribution across semiconductor wafers due to variations in emissivity and absorption patterns on the wafer's front side, leading to non-uniform heating and potential defects in integrated circuits.

Innovation Solution

The approach involves positioning the wafer's unpatterned back side facing the radiant heat source and the patterned front side facing a reflector, forming a black-body cavity that redistributes heat and allows for dynamic thermal monitoring, thereby enhancing temperature uniformity across the substrate.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If the wafer's patterned front side faces the radiant heat source, then the heating process can be performed, but non-uniform temperature distribution occurs due to variations in emissivity and absorption patterns

Engineering Contradiction:

Improvetemperature uniformityVSAvoidtemperature distribution uniformity

Core Design Contradiction:

TemperatureVSManufacturing precision

Solution Approach 1:

The patent inverts the conventional RTP configuration by positioning the unpatterned back side of the wafer to face the radiant heat source instead of the patterned front side. This inversion eliminates emissivity variations caused by circuit patterns, resulting in uniform heat absorption across the entire wafer surface and resolving the temperature distribution non-uniformity problem.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent utilizes the different thermal properties of the wafer's back side compared to its front side. The unpatterned back side has uniform emissivity and absorption characteristics, making it ideally suited for radiant heating. By applying heat to this specific region with different local quality properties, uniform temperature distribution is achieved across the entire wafer.

Inventive Principle:

Principle #3Local quality

2Temperature

If the unpatterned back side faces the heat source, then temperature uniformity is improved, but the configuration complexity increases

Engineering Contradiction:

Improvetemperature uniformityVSAvoidprocessing configuration

Core Design Contradiction:

TemperatureVSDevice complexity

Solution Approach 1:

Inventive Principle:

Principle #13The other way round (Inversion)

3Measurement precision

If the front side faces the heat source, then thermal monitoring can be performed, but heat absorption uniformity decreases

Engineering Contradiction:

Improvethermal monitoring capabilityVSAvoidheat absorption uniformity

Core Design Contradiction:

Measurement precisionVSTemperature

Solution Approach 1:

The patent introduces a transparent window as an intermediary that allows thermal monitoring of the patterned front side while the unpatterned back side receives radiant heating. This mediator enables both functions to coexist: the front side can be monitored for temperature while the back side provides uniform heat absorption, resolving the contradiction between monitoring capability and heating uniformity.

Inventive Principle:

Principle #24Intermediary (Mediator)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This configuration ensures consistent heat absorption and distribution, reducing temperature variations and improving the yield of integrated circuits by maintaining uniformity and reducing the risk of defects, while also simplifying the matching of edge ring emissivity with the wafer's back side.

Implementation Method 1

rapid thermal processing, (RTP) has been increasingly used to satisfy the ever more stringent requirements for ever smaller circuit features. RTP is typically performed in single-wafer chambers by irradiating a wafer with light from an array of high-intensity lamps directed at the front face of the wafer

Methodology Applied

Scientific EffectThermal radiation: Thermal Radiation

Implementation Method 2

The radiation is at least partially absorbed by the wafer and quickly heats it to a desired high temperature

Methodology Applied

Scientific EffectAbsorption (EM radiation): Absorption (EM radiation)

Implementation Method 3

One passive means of improving the uniformity includes a reflector extending parallel to and over an area greater than the wafer and facing the back side of the wafer. The reflector efficiently reflects heat radiation emitted from the wafer back toward the wafer

Methodology Applied

Scientific EffectReflection: Reflection

Implementation Method 4

The reflector effectively forms a black-body cavity at the back of the wafer that tends to distribute heat from warmer portions of the wafer to cooler portions

Methodology Applied

Scientific EffectThermal radiation: Thermal Radiation

Data Source

PatentUS9431278B2Backside rapid thermal processing of patterned wafers

Publication Date: 2016.08.30 APPLIED MATERIALS INC

AI summary

Apparatus and methods of thermally treating a wafer or other substrate, such as rapid thermal processing (RTP) apparatus and methods are disclosed. An array of radiant lamps directs radiation to the back side of a wafer to heat the wafer. In one or more embodiments, the front side of the wafer on which the patterned integrated circuits are being formed faces a radiant reflector. In one or more embodiments, the wafer is thermally monitored for temperature and reflectivity from the side of the reflector.