TSV Formation Prior to Circuitry Using Polysilicon
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for forming through silicon vias (TSVs) in integrated circuit substrates often require high-temperature processing steps that can cause thermal stress and material diffusion, limiting the choice of materials and complicating the integration of microelectromechanical systems (MEMS) devices due to outgassing issues.
Innovation Solution
Forming TSVs prior to the creation of integrated circuitry using conductive materials like polysilicon, which can withstand high temperatures, and bonding the ASIC substrate with a MEMS device such that the ASIC circuitry faces away from the MEMS substrate to prevent outgassing contamination and enhance pressure control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If high-temperature processing steps are used to form TSVs, then conductive materials like polysilicon can be used which withstand high temperatures, but thermal stress and material diffusion occur that limit material choices and complicate MEMS integration
Solution Approach 1:
The TSVs are formed prior to the creation of integrated circuitry on the substrate. This preliminary formation allows high-temperature processing to be performed before temperature-sensitive components are present, enabling the use of high-temperature conductive materials like polysilicon without causing thermal stress or material diffusion to the circuitry.
2Ease of manufacture
If TSVs are formed after integrated circuitry is created, then circuitry is already present on the substrate, but high-temperature processing causes thermal stress and material diffusion that damage the circuitry
Solution Approach 1:
The TSV formation is performed as a preliminary step before integrated circuitry fabrication. This sequencing allows the substrate to undergo high-temperature processing while in a simpler state, avoiding damage to complex circuit structures that would be present if TSVs were formed afterward.
3Reliability
If MEMS substrate is bonded to ASIC substrate with circuitry facing the MEMS substrate, then electrical connection is provided, but outgassing from the cavity contaminates the MEMS device
Solution Approach 1:
Instead of bonding the MEMS substrate to the front side of the ASIC substrate (which would place circuitry facing the MEMS device), the invention inverts the bonding orientation by bonding to the backside of the ASIC substrate. This inversion positions the circuitry away from the MEMS device, allowing outgassing to occur without contamination while maintaining electrical connection through the TSVs.
4Productivity
If via diameters are reduced to increase component density, then component density increases, but fabrication becomes more difficult with conventional via materials
Solution Approach 1:
The invention changes the material parameter of the via fill material to polysilicon, which can be deposited using CVD or sputtering processes capable of forming small-diameter vias. This parameter change enables the fabrication of smaller via diameters to increase component density, as these materials can be precisely deposited in narrow features compared to conventional electroplated metals.
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 approach allows for the use of high-temperature processing without thermal stress, enables smaller via diameters for increased component density, and simplifies access to electrical contacts, while maintaining a controlled environment for MEMS devices by directing outgassing away from the cavity.
Implementation Method 1
The TSVs may be formed prior to formation of the integrated circuitry on the integrated circuit substrate, allowing the use of via materials which can be fabricated at relatively small sizes... forming a through silicon via (TSV) in a substrate prior to forming any metal features on the substrate... forming TSVs prior to the creation of integrated circuitry using conductive materials like polysilicon, which can withstand high temperatures
Implementation Method 2
The MEMS substrate and ASIC substrate are bonded at the backside of the ASIC substrate such that the device surface is distal the MEMS substrate
Implementation Method 3
bonding the ASIC substrate with a MEMS device such that the ASIC circuitry faces away from the MEMS substrate to prevent outgassing contamination and enhance pressure control... simplifies access to electrical contacts, while maintaining a controlled environment for MEMS devices by directing outgassing away from the cavity
Data Source
AI summary
Integrated circuit substrates having through silicon vias (TSVs) are described. The TSVs are vias extending through the silicon substrate in which the integrated circuitry is formed. The TSVs may be formed prior to formation of the integrated circuitry on the integrated circuit substrate, allowing the use of via materials which can be fabricated at relatively small sizes. The integrated circuit substrates may be bonded with a substrate having a microelectromechanical systems (MEMS) device. In some such situations, the circuitry of the integrated circuit substrate may face away from the MEMS substrate since the TSVs may provide electrical connection from the circuitry side of the integrated circuit substrate to the MEMS device.