With power density and hence cooling costs rising exponentially, processor packaging can no longer be designed for the worst case, and there is an urgent need for runtime processor-level techniques that can regulate operating temperature when the package’s capacity is exceeded. Evaluating such techniques, however, requires a thermal model that is practical for architectural studies. This paper describes HotSpot, an accurate yet fast model based on an equivalent circuit of thermal resistances and capacitances that correspond to microarchitecture blocks and essential aspects of the thermal package. Validation was performed using finiteelement simulation. The paper also introduces several effective methods for dynamic thermal management (DTM): “temperaturetracking” frequency scaling, localized toggling, and migrating computation to spare hardware units. Modeling temperature at the microarchitecture level also shows that power metrics are poor predictors of temperature, and that sensor imprecision has a substantial impact on the performance of DTM. 1.

Non-uniform temperature profiles along global interconnect lines in high-performance ICs can significantly impact the performance of these lines. This paper presents a detailed analysis and modeling of the interconnect performance degradation due to non-uniform temperature profiles that exist along their lengths, which in turn arise due to the thermal gradients in the underlying substrate. A nonuniform temperature-dependent distributed RC interconnect delay model is proposed for the first time. The model has been applied to a wide variety of interconnect layouts and temperature distributions to quantify the impact on signal integrity issues including clock skew fluctuations.

r distribution and signal transmission through the interconnects due to self-heating (or Joule heating) caused by the flow of current. Current flow in a VLSI interconnect causes a power dissipation of IR 2 , where I is the current through the interconnect and R is the line resistance. Since the interconnects, especially the global-tier interconnects, are far away from the substrate, which is attached to the heat sink, the heat generated due to this IR 2 power dissipation cannot be efficiently removed and therefore causes an increase in interconnect temperature. This phenomenon is referred to as Joule heating or self-heating. Even though this IR 2 power dissipation is not a major portion of the total chip power dissipation, since this power is dissipated by the interconnects, which are separated from the substrate by a dielectric that has very low thermal c

This paper presents both compact analytical models and fast SPICE based 3-D electro-thermal simulation methodology to characterize thermal effects due to Joule heating in high performance Cu/low-k interconnects under steady-state and transient stress conditions. The results demonstrate excellent agreement with experimental data and those using Finite Element (FE) thermal simulations (ANSYS). The effect of vias, as additional heat sinking paths to alleviate the temperature rise in the metal wires, is included in our analysis to provide more accurate and realistic thermal diagnosis. It shows that the effectiveness of vias in reducing the temperature rise in interconnects is highly dependent on the via separation and the dielectric materials used. The analytical model is then applied to estimate the temperature distribution in multi-level interconnects. In addition, we discuss the possibility that, under the impact of thermal effects, the performance improvement expected from the use of low-k dielectric materials may be degraded. Furthermore, thermal coupling between wires is evaluated and found to be significant. Finally, the impact of metal wire aspect ratio on interconnect thermal characteristics is discussed. 1.

This paper presents a compact analytical model for estimating the temperature rise of multilevel ULSI interconnects incorporating via effect. For the first time, an analytical expression is derived for the via correction factor, h, which quantifies the effect of via separation on the effective thermal conductivity of ILD (inter-layer dielectrics), k ILD,effective , with k ILD,effective = k ILD /h , where 0<h<1. Both the temperature profile along the metal lines and average temperature rise of the lines can be easily obtained using this analytical model. The predicted temperature profiles are shown to be in excellent agreement with the 3-D finite element thermal simulation results. The model is then applied to estimate the temperature distribution in multi-level interconnects. Significant difference in temperature distribution and maximum temperature rise is observed between the realistic situation of heat dissipation with vias and the overly simplified case that ignores via effect.

This paper presents a comprehensive analysis of the thermal ects in advanced high performance interconnect systems arising due to selfheating under various circuit conditions, including electrostatic discharge. Technology (Cu, low-k etc) and scaling effects on the thermal characteristics of the interconnects, and on their electromigration reliability has been analyzed simultaneously, which will have important implications for providing robust and aggressive deep sub-micron interconnect design guidelines. Furthermore, the impact of these thermal effects on the design (driver sizing) and optimization of the interconnect length between repeaters at the upperlevel signal lines are investigated.

This paper studies the effects of the substrate thermal gradients on the buffer insertion techniques. Using a non-uniform temperaturedependent distributed RC interconnect delay model, the buffer insertion problem is analyzed and design guidelines are provided to ensure the nearoptimality of the signal performance in the presence of the thermal gradients. In addition, the effect of temperature-dependent driver resistance on the buffer insertion is studied. Experimental results show that neglecting thermal gradients in the substrate and the interconnect lines can result in non-optimal solutions when using standard buffer insertion techniques and that these effects intensify with technology scaling.

A non-uniform temperature profile for the chip substrate in high-performance ICs can significantly impact the performance of the global on-chip interconnects. This paper presents a detailed modeling and analysis of the interconnect performance degradation due to the non-uniform temperature profiles that are encountered along the metal connections as a result of the thermal gradients in the underlying Silicon substrate. More precisely, a non-uniform temperature-dependent distributed RC interconnect delay model is proposed. The model is applied to a wide variety of interconnect layouts and substrate temperature distributions to quantify the impact of such thermal non-uniformities on signal integrity issues including speed degradation and clock skew fluctuations. Subsequently, a new thermally dependent zero-skew clock routing methodology is presented.