Erik Jan Marinissen

Testing 3D chips containing through-silicon vias

Todays miniaturization and performance requirements result in the usage of high-density integration and packaging technologies, such as 3D Stacked ICs (3D-SICs) based on Through-Silicon Vias (TSVs). Due to their advanced manufacturing processes and physical access limitations, the complexity and cost associated with testing this type of 3D-SICs are considered major challenges. This Embedded Tutorial provides an overview of the manufacturing steps of TSV-based 3D chips and their associated test challenges. It discusses the necessary flows for wafer-level and package-level tests, the challenges with respect to test contents and wafer-level probe access, and the on-chip DfT infrastructure required for 3D-SICs.

Scan chain design for test time reduction in core-based ICs

The size of the test vector set forms a significant factor in the overall production costs of ICs, as it defines the test application time and the required pin memory size of the test equipment. Large core-based ICs often require a very large test vector set for a high test coverage. This paper deals with the design of scan chains as transport mechanism for test patterns from IC pins to embedded cores and vice versa. The number of pins available to accommodate scan test is given, as well as the number of scan test patterns and scannable flip flops of each core. We present and analyze three scan chain architectures for core-based ICs, which aim at a minimum test vector set size. We give experimental results of the three architectures for an industrial IC. Furthermore we analyze the test time consequences of reusing cores with fixed internal scan chains in multiple ICs with varying design parameters.

Testing embedded-core-based system chips

Recently, designers have been embedding reusable modules to build on-chip systems that form rich libraries of predesigned, preverified building blocks. These embedded cores make it easier to import technology to a new system and differentiate the corresponding product by leveraging intellectual property advantages. Most importantly, design reuse shortens the time-to-market for new systems. The attributes that make system chips built with embedded IP cores an attractive methodology-design reuse, heterogeneity, reconfigurability, and customizability-also make testing and debugging these chips a complex challenge. The authors review the various alternatives for testing embedded cores and describe solutions and proposed standards that are expected to play a key role in developing the core based design paradigm.

A structured and scalable test access architecture for TSV-based 3D stacked ICs

New process technology developments enable the creation of three-dimensional stacked ICs (3D-SICs) interconnected by means of Through-Silicon Vias (TSVs). This paper presents a DfT test access architecture for such 3D-SICs that allows for both pre-bond die testing and post-bond stack testing. The DfT architecture is based on a modular test approach, in which the various dies, their embedded IP cores, the inter-die TSV-based interconnects, and the external I/Os can be tested as separate units to allow optimization of the 3D-SIC test flow. The architecture builds on and reuses existing DfT hardware at the core, die, and product level. It adds a die-level wrapper, which is based on IEEE 1500, with the following novel features: (1) dedicated probe pads on the non-bottom dies to facilitate pre-bond die testing, (2) TestElevators that transport test control and data signals up and down during post-bond stack testing, and (3) a hierarchical Wrapper Instruction Register (WIR) chain. The paper also hints at opportunities for optimization and standardization of this architecture.

Testing TSV-based three-dimensional stacked ICs

To meet customers product-quality expectations, each individual IC needs to be tested for manufacturing defects incurred during its many high-precision, and hence defect-prone manufacturing steps; these tests should be both effective and cost-efficient. The semiconductor industry is preparing itself now for three-dimensional stacked ICs (3D-SICs) based on Through-Silicon Vias (TSVs), which, due to their many compelling benefits, are quickly gaining ground. Test solutions need to be ready for this new generation of ‘super chips’. 3D-SICs are chips where all basic, as well as most advanced test technologies come together. In addition, they pose some truly new test challenges with respect to complexity and cost, due to their advanced manufacturing processes and physical access limitations. This presentation focuses on the available solutions and still open challenges for testing 3D-SICs. It discusses flows for wafer-level and package-level tests, the challenges with respect to test contents and wafer-level probe access, and the on-chip Design-for-Test (DfT) infrastructure required for 3D-SICs.

Impact of 3D design choices on manufacturing cost

The available options in 3D IC design and manufacturing have different impact on the cost of a 3D System-on-Chip. Using the 3D cost model developed at IMEC, the cost of different system integration options is analyzed and the cost effectiveness of different technology solutions is demonstrated. The cost model is based on the IMEC 3D integration process flows and includes the cost of manufacturing equipment, fabrication facilities, personnel, and materials. Using the IMEC 3D cost model, the cost of various 3D stacking strategies is compared to single die (i.e. 2D) integration. In addition, the effect on cost of different Through-Silicon-Via (TSV) manufacturing technologies is evaluated. The effectiveness of different 3D testing strategies and their impact on system cost is also investigated.

Challenges and emerging solutions in testing TSV-based 2 1 over 2D- and 3D-stacked ICs

Through-Silicon Vias (TSVs) provide high-density, low-latency, and low-power vertical interconnects through a thinned-down wafer substrate, thereby enabling the creation of 2.5D- and 3D-Stacked ICs. In 2.5D-SICs, multiple dies are stacked side-by-side on top of a passive silicon interposer base containing TSVs. 3D-SICs are towers of vertically stacked active dies, in which the vertical inter-die interconnects contain TSVs. Both 2.5D- and 3D-SICs are fraught with test challenges, for which solutions are only emerging. In this paper, we classify the test challenges as (1) test flows, (2) test contents, and (3) test access.

3D DfT architecture for pre-bond and post-bond testing

Process technology developments enable the creation of three-dimensional stacked ICs (3D-SICs) interconnected by means of Through-Silicon Vias (TSVs). This paper presents a 3D Design-for-Test (DfT) architecture for such 3D-SICs that allows pre-bond die testing as well as post-bond stack testing of both partial and complete stacks. The architecture enables on a modular test approach, in which the various dies, their embedded IP cores, the inter-die TSV-based interconnects, and the external I/Os can be tested as separate units to allow flexible optimization of the 3D-SIC test flow. The architecture builds on and reuses existing DfT hardware at the core, die, and product level. Its main new component is a die-level wrapper, which can be based on either IEEE Std 1500 or IEEE Std 1149.1. The paper presents a conceptual overview of the architecture, as well as implementation aspects. Experimental results show that the implementation costs are negligible for medium to large dies.

Test Cost Analysis for 3D Die-to-Wafer Stacking

The industry is preparing itself for three-dimensional stacked ICs (3D-SICs), a technology that promises heterogeneous integration with higher performance and lower power dissipation at a smaller footprint. Several 3D stacking approaches are under development. From a yield point of view, Die-to-Wafer (D2W) stacking seems the most favorable approach, due to the ability of Known Good Die stacking. Minimizing the test cost for such a stacking approach is a challenging task. Every manufactured chip has to be tested, and any tiny test saving per 3D-SIC impacts the overall cost, especially in high-volume production. This paper establishes a cost model for D2W SICs and investigates the impact of the test cost for different test flows. It first introduces a framework covering different test flows for 3D D2W ICs. Subsequently, it proposes a test cost model to estimate the impact of the test flow on the overall 3D-SIC cost. Our simulation results show that (a) test flows with pre-bond testing significantly reduce the overall cost, (b) a cheaper test flow does not necessary result in lower overall cost, (c) test flows with intermediate tests (performed during the stacking process) pay off, (d) the most cost-effective test flow consists of pre-bond tests and strongly depends on the stack yield, hence, adapting the test according the stack yield is the best approach to use.

Optimization methods for post-bond die-internal/external testing in 3D stacked ICs

Testing of three-dimensional (3D) stacked ICs (SICs) is starting to receive considerable attention in the semiconductor industry. Since the die-stacking steps of thinning, alignment, and bonding can introduce defects, there is a need to test multiple subsequent partial stacks during 3D assembly. We address the problem of test-architecture optimization for 3D stacked ICs to minimize overall test time when either the complete stack only, or the complete stack and multiple partial stacks, need to be tested. We show that optimal test-architecture solutions and test schedules for multiple test insertions are different from their counterparts for a single final stack test. In addition, we present optimization techniques for the testing of TSVs and die-external logic in combination with the dies in the stack.