Stealth Dicing Low-k Dielectric Wafer Separation
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Solution Overview
Problem
The separation of microelectronic devices from wafers often results in irregularities and damage due to the use of low k dielectric materials, leading to reduced yield and increased mortality rates, as these materials suffer from mechanical weakness, thermal instability, and coefficient of thermal expansion mismatches with other materials.
Innovation Solution
A stealth dicing method is employed, where a laser beam is used to form weakened regions within the wafer aligned with scribe lines, and the wafer is thinned while maintained at a cold temperature to render dielectric materials brittle, allowing for clean fractures along these lines without tears or delamination, using a process called Stealth Dicing Before Grind (SDBG).
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If low k dielectric materials are used to enhance scaling, then parasitic capacitance is reduced and switching speeds are improved, but mechanical strength and thermal stability deteriorate
Solution Approach 1:
The patent changes the physical state of the low k dielectric material by cooling it below its glass transition temperature, transforming it from a rubbery, mechanically weak state to a glassy, brittle state with improved mechanical strength and dimensional stability during separation
Solution Approach 2:
The patent utilizes the glass transition phase change of the low k dielectric material. By cooling the wafer below the glass transition temperature of the dielectric, the material transitions from a rubbery phase to a glassy phase, enabling clean fracture during separation while maintaining the electrical benefits of low k materials
2Reliability
If low k dielectric materials are used to eliminate crosstalk, then signal integrity is improved, but yield and mortality rates worsen due to irregularities during separation
Solution Approach 1:
The patent changes the temperature parameter of the low k dielectric material to below its glass transition temperature, transforming its mechanical properties from rubbery and irregular-fracturing to glassy and clean-fracturing, thereby improving yield during separation while maintaining signal integrity benefits
Solution Approach 2:
The patent performs preliminary cooling of the wafer below the glass transition temperature of the low k dielectric material before the separation process. This preliminary action ensures the dielectric material is in a brittle, clean-fracturing state when separation occurs, preventing irregularities that would reduce yield
3Strength
If conventional dielectric materials are used, then mechanical strength is maintained, but charge buildup and crosstalk increase
Solution Approach 1:
The patent changes the temperature parameter of low k dielectric materials to below their glass transition temperature, improving their mechanical strength and dimensional stability to levels comparable with conventional dielectrics, while retaining the electrical advantage of reduced charge buildup and crosstalk
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 method enables the production of thinner microelectronic devices with improved yield and reduced infant mortality by ensuring clean breaks and maintaining the integrity of the devices, thereby enhancing the reliability and performance of the microelectronic devices.
Implementation Method 1
focusing a laser beam within a wafer to form scribe lines including a modified layer of weakened semiconductor material
Implementation Method 2
cooling the wafer to a temperature below a glass transition temperature of the low k dielectric material
Implementation Method 3
cooling the wafer to a temperature below a glass transition temperature of the low k dielectric material
Implementation Method 4
fracturing the thinned wafer and the dielectric material along boundaries corresponding to the scribe lines
Data Source
AI summary
A method of manufacturing a microelectronic device may include forming a wiring layer on a first surface of a wafer. The method may also include forming a modified layer along separation regions for each microelectronic device of the wafer by focusing a laser on an inside portion of the wafer. The method may also include removing material from the second surface of the wafer. The wafer may be cooled to a temperature where a low dielectric constant layer extending across the separation regions is brittle while the material is removed from the second surface of the wafer. The method may further include separating the wafer along the separation region to form separate microelectronic devices.