Large‐Area Uniform 1‐nm‐Level Amorphous Carbon Layers from 3D Conformal Polymer Brushes. A “Next‐Generation” Cu Diffusion Barrier?
Yun‐Ho KangSang‐Bong LeeYoungwoo ChoiWon Kyung SeongKyu Hyo HanJang Hwan KimHyun‐Mi KimSeungbum HongSun Hwa LeeRodney S. RuoffKi‐Bum KimSang Ouk Kim
13
Citation
88
Reference
10
Related Paper
Citation Trend
Abstract:
A reliable method for preparing a conformal amorphous carbon (a-C) layer with a thickness of 1-nm-level, is tested as a possible Cu diffusion barrier layer for next-generation ultrahigh-density semiconductor device miniaturization. A polystyrene brush of uniform thickness is grafted onto 4-inch SiO2 /Si wafer substrates with "self-limiting" chemistry favoring such a uniform layer. UV crosslinking and subsequent carbonization transforms this polymer film into an ultrathin a-C layer without pinholes or hillocks. The uniform coating of nonplanar regions or surfaces is also possible. The Cu diffusion "blocking ability" is evaluated by time-dependent dielectric breakdown (TDDB) tests using a metal-oxide-semiconductor (MOS) capacitor structure. A 0.82 nm-thick a-C barrier gives TDDB lifetimes 3.3× longer than that obtained using the conventional 1.0 nm-thick TaNx diffusion barrier. In addition, this exceptionally uniform ultrathin polymer and a-C film layers hold promise for selective ion permeable membranes, electrically and thermally insulating films in electronics, slits of angstrom-scale thickness, and, when appropriately functionalized, as a robust ultrathin coating with many other potential applications.Keywords:
Conformal coating
Diffusion barrier
Barrier layer
Polystyrene
Adhesion of copper with diffusion barrier layer has been studied for Cu interconnection. Ta-based barrier materials have been employed. The Cu adhesion property with these barrier materials was estimated by stress concept, and was experimentally examined. Higher and high stresses are attained in thin Cu layer (10 nm thick) when deposited on TaN and Ta diffusion barrier layers, which lead to poorer and poor adhesion strengths with Cu, respectively. On the other hand, much lower stress are attained in the thin Cu layer when deposited on TaSiN diffusion barrier, revealing much better adhesion strength of Cu with TaSiN layer. X-ray diffraction spectra and scanning electron microscopy measurement revealed that the highly stressed thin Cu layer on TaN barrier layer changes to a low stressed thin Cu layer as a result of agglomeration, which happened after annealing at 400 °C. The surface of thin Cu layer changes to rough surfaces with annealing at 400 °C in the layer deposited on TaN. However, a smooth surface is held in the low stress layer on the TaSiN barrier layer.
Diffusion barrier
Barrier layer
Cite
Citations (1)
Diffusion barrier
Barrier layer
Cite
Citations (1)
The concept of the diffusion barrier coating system (DBC system) is summarized and the latest results are presented. The DBC system is comprised of alloy substrate/diffusion barrier/Al-reservoir/an external scale. Diffusion flux ( J Al) of Al through the barrier layer will be given approximately by J Al = D Al x S Al x ( d C Al / d x), where D Al and S Al are the diffusion coefficient and solubility limit of Al in the barrier layer, respectively as well as d CAl / d x is driving force given by the concentration difference across the barrier ( d CAl) divided by the thickness of the barrier layer ( d x). A slow diffusion flux can be obtained by using low values of D Al, S Al, or ( d CAl / d x). Accordingly, a selection of a barrier layer with lower D Al and S Al is essential. A low driving force is also an important factor, and can be achieved by using lower C Al with a constant barrier layer thickness dx. At higher temperatures, however, the barrier layer can react with the alloy substrate and Al-reservoir layer, resulting in gradual degradation of the barrier layer. This means that the thickness dx of the barrier layer tends to decrease and may finally disappear. With decreasing thickness of the diffusion barrier layer, the driving force (dCAl/dx) will increase, and the effectiveness of the barrier layer will be eliminated. Therefore, it is essential to maintain a constant thickness of the barrier layer for long exposure time. Several types of the DBC system are proposed, a single barrier layer and triple-layers with g + g’ and g’ inserted among these barrier layers.
Diffusion barrier
Barrier layer
Cite
Citations (1)
We investigated the effects of tungsten silicon nitride/tungsten silicide (WSiN/WSix) barrier layer thickness on its barrier capability. WSiN was obtained by nitridizing the WSix surface with electron cyclotron resonance nitrogen plasma. The total thickness of the WSiN/WSix barrier layer was reduced by thinning the initial WSix layer. When 5-nm-thick WSix was nitridized, the N and Si contents in the WSiN/WSix layer became smaller than when WSix initial thickness was 20 nm. This barrier layer diffused into the copper (Cu) layer when annealed, and did not act as a barrier layer. On the contrary, a WSiN/WSix barrier layer formed by nitridizing 10-nm-thick WSix showed good barrier capability against Cu diffusion. We evaluated the leakage current between Cu damascene interconnections with this barrier layer and found that this barrier layer formed on the trench side wall prevents Cu diffusion when the thickness on the side wall is over 10 nm.
Diffusion barrier
Barrier layer
Cite
Citations (4)
As an extremely thin diffusion barrier applicable to Cu interconnects for the 45 nm technology nodes, we propose a barrier material without interface layers that can become a cause of barrier consumption owing to solid-phase reaction and/or intermixing. We examine the barrier properties of a reactively sputtered ZrN barrier as thin as 5 nm between Cu and SiOC. The ZrN barrier with a slightly N-rich composition tolerates annealing at 500 °C for 30 min. Transmission electron microscopy indicates the absence of interface layers adjoining the barrier. Using the ZrN barrier, we can demonstrate the effectiveness of the interface-layer-free characteristics for an extremely thin barrier of high performance.
Diffusion barrier
Barrier layer
Rectangular potential barrier
Cite
Citations (11)
Diffusion barrier
Barrier layer
Electromigration
Cite
Citations (7)
Diffusion barrier
Barrier layer
Cite
Citations (31)
SummaryTests have been carried out on copper and brass substrates which have been electroplated with a number of different barrier layers and then with an excess of matt tin. These samples have been heat treated to simulate accelerated storage and operation periods and observations made on the resulting intermetallic compound layers between the substrate and the tin coating. The results indicate the suitability of each barrier layer for altering the rate of growth of substrate-tin intermetallics and also the ability of the barrier to inhibit the diffusion of, specifically, zinc to the surface of the coating. On the basis of lowest barrier/coating reaction rates, iron appears by far the best choice for a barrier layer.
Diffusion barrier
Barrier layer
Brass
Cite
Citations (49)
A laterally segregated diffusion barrier was investigated for Cu metallization. In this scheme, the intended final structure is composed of two different barrier materials; one is the parent barrier layer (TiN, in our case) and the other (Al2O3, in this case) is segregated laterally along the grain boundaries of the parent barrier layer. As a result, the fast diffusion paths, the so-called grain boundaries of the parent diffusion barrier, are effectively passivated. To realize this type of barrier experimentally, the TiN(5 nm)/Al(2 nm)/TiN(5 nm) structure was fabricated by sequential sputtering and compared with TiN(10 nm) as a diffusion barrier against Cu. The etch pit test results indicated that the barrier with the Al interlayer prevented Cu diffusion into the Si up to 650 °C, which is 250 °C higher than achieved by a TiN(10 nm) barrier.
Diffusion barrier
Barrier layer
Rectangular potential barrier
Cite
Citations (44)
This study examines the possibility of employing an electroless-plated Ni(P) layer as a diffusion barrier between the Sn bonding layer and Cu bump for 3D integration applications. We bonded the samples at different bonding temperatures (200∼350°C) and probed into the bonding morphology to evaluate the effects of the addition of a Ni(P) barrier. Combination of scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analyses revealed that the Ni(P) barrier effectively suppressed Cu diffusion while an interaction between Ni(P) and Sn consumed the barrier in a gradual manner. The samples with a Ni(P) barrier were found mechanically much more reliable than those without a barrier, owing to suppressed IMC reaction and Cu diffusion. In addition, the insertion of a Ni(P) barrier did not affect the resistance much in comparison with the samples without a barrier.
Diffusion barrier
Barrier layer
Diffusion bonding
Cite
Citations (16)