R&D Project 3:
An ultra-thin monolithic pixel detector system for decay vertex identification

Research Objective

The object of the research task is a novel ultra-thin charged particle detection system for precision decay vertex identification, composed of thinned CMOS monolithic pixel detectors supported by a thin thermal conductor. The material budget of the system is of central concern, since conventional technologies based on carbon fibre supports will hardly meet the challenging CBM vertex detection requirements, taking into account the cooling needs of the detectors in a vacuum environment. Several materials, including thin-film polymers, allow for the integration of read-out and power lines, thus assuring minimum system thickness. This is culminated with the application of industrial CVD diamond, due to its excellent material properties regarding flexural stiffness and, in particular, heat conduction. For the assembly of such very thin devices, the mastering of novel processing techniques and advanced handling skills are key aspects of the challenge. In this activity, we focus on exploring 3D or vertical integration technologies that are currently vividly emerging in fore-front semiconductor research labs and industry. These technologies allow for stacking very thin layers of heterogeneous, micro-structured circuitry. We will explore how to condition and to manipulate thin CMOS sensors and how to fix and align them with high precision on thin support layers. A prototype module will be assembled and characterized in particular for thermal stability. The research will end with a decision on the way how to elaborate for the final deliverable, a high-precision ultra-thin vertex detection system with built-in thermal management and an overall material budget below the current record (which is between 0.3% and 0.4% radiation length in ambient atmosphere), in a possible extension of the research project beyond 2011.


CNRS Strasbourg (M. Winter, activity leader), GUF Frankfurt (J. Stroth), IMEC Leuven (P. De Moor)

Tasks (updated)

Task Nr. Task name Participants
P3/T1 Design check of CMOS sensors CNRS
P3/T12 Evaluation of a 3D-assembled module prototype,
incl. thermal stability in atmosphere and vacuum
P3/T2 Simulation of heat evacuation GUF
P3/T3 Fabrication of thin electrical support layers CNRS, IMEC
P3/T4 Fabrication of thin mechanical support layers CNRS, GUF
P3/T5 Fabrication of interface electronics CNRS, GUF
P3/T6 Fabrication of CMOS sensors CNRS, GUF
P3/T7 Test of interface electronics CNRS, GUF
P3/T8 Thinning of CMOS sensors CNRS, GUF
P3/T9 Validation, handling procedures for sensors & supports CNRS, IMEC
P3/T10 Validation of precision alignment procedures
for thin sensors on thin supports
P3/T11 Assembly tests of CMOS sensors on several supports CNRS, IMEC


Tasks 2009 2010 2011
Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4
Evaluation of 3D-assembly module prototype X X X X X X X X X 5    
Realization of support structures X X X X X 1            
Fabrication and thinning of CMOS detectors X X X X X 2            
Validation of handling and alignment procedures X X X X X X X 3        
3D assembly tests CMOS detectors on support X X X X X X X 4        

  1. Production of electrical and mechanical support layers
  2. Fabrication and thinning of CMOS detectors
  3. Validation of handling and precision alignment procedures
  4. 3D assembly test ofCMOS detectors on support
  5. Evaluation of a 3D-assembled module prototype


Prototype of an ultra-thin 3D-assembled CMOS pixel detector module.

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-- JohannMHeuser - 02 Feb 2012
Topic revision: r1 - 02 Feb 2012, JohannMHeuser
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