Improvement of Wafer Edge Profile and Cmp Performance Through The Floating Head Design

2000 ◽  
Vol 613 ◽  
Author(s):  
Huey-Ming Wang ◽  
Gerry Moloney ◽  
Mario Stella ◽  
Sesinando Deguzman
Keyword(s):  
Chemical Mechanical Planarization ◽  
Pressure Chamber ◽  
Point Of View ◽  
Thickness Variation ◽  
Deformation Control ◽  
Edge Profile ◽  
Retaining Ring ◽  
Floating Type ◽  
Edge Exclusion ◽  
Wafer Edge

ABSTRACTThe dependence of IC fabrication on the Chemical Mechanical Planarization (CMP) process increases as the device features go down to 0.25 micron or beyond. Due to the tighter CMP process spec, it is very important to reduce the within wafer non-uniformity (WIWNU%) to achieve higher process yield. The symmetrical increment of linear velocity at wafer edge is not sufficient to change wafer edge profile by breaking the matched speed rule. A better solution is through the change of head design for a fixed platen from the polisher design point of view. This study demonstrates the improvement of the CMP process performance, especially at the wafer edge, from the modification of the floating type polish head. The best WIWNU% from a single air chamber head is about 5.12% at 6-mm edge exclusion (EE). In order to obtain better pad deformation control, the retaining-ring pressure chamber is separated from that of the sub-carrier. The average WIWNU% is about 4% for 3-mm and 5-mm EE from two-pressure-chamber head. Due to the limitation of retaining-ring pressure effect, a third pressure chamber is further added that can be extended the edge control up to 1 inch from the wafer edge. The WIWNU% is about 3.8% at 5-mm edge exclusion with low down forces. The slurry and insert types also show effect on the wafer edge profile. It has been also proven that this three-pressure-chamber head is able to reduce the post-CMP thickness variation from the ILD production wafer, especially at wafer edges. More detailed information and CMP mechanism will be discussed in this paper.

Effects of Wafer Carrier Design on Contact Stress Uniformity in CMP

2010 ◽  
Vol 126-128 ◽  
pp. 305-310 ◽  
Author(s):  
Ian Hu ◽  
Tian Shiang Yang ◽  
Kuo Shen Chen
Keyword(s):  
Contact Stress ◽  
Removal Rate ◽  
Ring Width ◽  
Pressure Profile ◽  
Back Pressure ◽  
Design Parameters ◽  
Wafer Surface ◽  
Retaining Ring ◽  
Floating Type ◽  
Stress Uniformity

Here we use 2-D models of fluid film lubrication and contact mechanics to calculate the contact stress and fluid (i.e., slurry) pressure distributions on the wafer–pad interface in CMP. In particular, the effective rigidity of the wafer (determined by the wafer carrier structure), the retaining ring width and its back pressure are taken to be the design parameters. The purpose is to study the synergetic effects of such parameters on the contact stress non-uniformity (NU), which directly affects the spatial non-uniformity of the material removal rate on the wafer surface. Our numerical results indicate that, for a given wafer rigidity, one may choose a particular combination of the retaining ring parameters to minimize NU. Also, the corresponding minimum NU decreases with the effective wafer rigidity, suggesting that it is beneficial to use a soft (e.g., floating-type) wafer carrier. Moreover, for a soft wafer carrier, the presence of the retaining ring also reduces NU to some extent, but the use of a multi-zone wafer-back pressure profile would be more effective in this regard.

A Multistep Process for Thinning Individual Die to sub-35 μm Thickness

2010 ◽  
Vol 7 (4) ◽  
pp. 189-196
Author(s):  
Jeffrey Thompson ◽  
Gary Tepolt ◽  
Livia Racz ◽  
C.B. Rogers ◽  
V.P. Manno ◽  
...  
Keyword(s):  
Glass Substrate ◽  
Chemical Mechanical Planarization ◽  
Thickness Variation ◽  
Total Thickness ◽  
Bulk Silicon ◽  
Wafer Level ◽  
Damage Layer ◽  
Die Stacking ◽  
Multistep Process ◽  
Total Thickness Variation

The drive toward increased packaging density relies on die stacking. In order to maximize functional density, die are generally thinned on the wafer level. However, high-cost low-volume applications may not have full wafers available. Therefore, a method to thin individual die must be developed. In this article, a detailed and reliable process for thinning die to sub35 μm is outlined. The process consists of four steps: pseudo-wafer lamination, mechanical lapping, chemical mechanical planarization (CMP), and die release. A pseudo-wafer is created by adhering die to a glass substrate. Mechanical lapping is used to remove the bulk silicon and reduce die thickness to approximately 50 μm. CMP is used to attain thicknesses of sub35 μm and remove the subsurface damage layer from the die. This process can reliably produce die thinned to sub35 μm with ± 1.5-μm total thickness variation (TTV). The die are then released from the glass substrate and are handled using a customized vacuum carrier.

CMP at the Wafer Edge – Modeling the Interaction between Wafer Edge Geometry and Polish Performance

2005 ◽  
Vol 867 ◽  
Author(s):  
Xiaolin Xie ◽  
Duane Boning
Keyword(s):  
Integrated Circuit ◽  
Material Properties ◽  
Geometry Optimization ◽  
Front Surface ◽  
Tool Geometry ◽  
Process Improvements ◽  
Edge Geometry ◽  
Retaining Ring ◽  
The Impact ◽  
Wafer Edge

AbstractAs the drive to improve integrated circuit manufacturing yield continues, renewed attention is being paid to the edge of the wafer. The industry is seeking to reduce the edge exclusion region and achieve good performance to within 2 mm or smaller. This creates substantial challenges, both for CMP and for the starting wafer. In this work, we consider two key elements that play a role in non-uniform polish near the edge of the wafer.First, we study the impact of localized pressure on the edge of the wafer as a function of the wafer and retaining ring pressures, gap separation between wafer and retaining ring, and pad material properties (pad Young's modulus). Simulations show that several millimeters into the wafer from the edge can polish either more quickly or more slowly than the center of the wafer, depending on the combination of these parameters. Second, we also consider the impact of wafer edge roll-off (the specific thickness or front surface elevation of the wafer geometry) on polishing uniformity. We again find that the polish uniformity can be affected dramatically, depending on the details of the starting wafer geometry.We believe that several innovations and optimizations are likely to arise in order to meet future wafer edge polish uniformity requirements. These include tool geometry and process improvements, tailoring of the pad material properties, and starting wafer edge geometry optimization and control.

Structured Abrasive CMP: Length Scales, Subpads, and Planarization

1999 ◽  
Vol 566 ◽  
Author(s):  
D. P. Goetz
Keyword(s):  
Contact Mechanics ◽  
Elastic Foundation ◽  
Chemical Mechanical Planarization ◽  
Minimum Length ◽  
Length Scale ◽  
Uniform Compression ◽  
Length Scales ◽  
Process Pressure ◽  
Edge Exclusion ◽  
Minimum Length Scale

Chemical-Mechanical Planarization with structured abrasive uses a subpad to manage the pressure variations due to loading over a range of length scales. The effect of subpad construction on pressure responses related to those scales is illustrated.A minimum length scale for the effect of the subpad is established via contact mechanics. Differences between one- and two-layer subpads are shown. Uniform compression, point loading, and edge exclusion are considered briefly. A model of the subpad as a plate on an elastic foundation is applied to the problem of die doming. The roles of process pressure, die size, and subpad construction are illustrated. Planarization at the intra-die, die, and wafer scales are related to the subpad construction.

Modeling and Analysis of Material Removal Characteristics in Silicon Wafer Double Side Polishing

2012 ◽  
Vol 516 ◽  
pp. 384-389
Author(s):  
Sang Jik Lee ◽  
Hyoung Jae Kim ◽  
Hae Do Jeong
Keyword(s):  
Integrated Circuits ◽  
Process Parameters ◽  
Material Removal Rate ◽  
Material Removal ◽  
Removal Rate ◽  
Thickness Variation ◽  
Modeling And Analysis ◽  
Profile Variation ◽  
Friction Energy ◽  
Wafer Edge

As advancing technologies increase the demand for yield and planarity in integrated circuits, wafers have become larger and their specifications more stringent. Flatness, thickness variation and nanotopography have emerged as important concerns in the wafering process. Double side polishing has been adopted as a solution to these problems. This paper focuses on the material removal characteristics and wafer profile variation during Si double side polishing. A polishing experiment to investigate Si removal characteristics according to process parameters was carried out in a single head rotary polisher equipped with a monitoring system for friction force. It was found that the material removal rate is related to friction energy rate, and the polishing state was transited and divided into three conditions according to pressure. On the basis of the experimental results, the wafer profile variation in double side polishing was modelled and simulated according to pressure. The friction energy was calculated to find the material removal amount across the wafer. With the conversion of calculated friction energy to the material removal amount, wafer profile variation was simulated. As a result, the wafer profile variation and its range were increased with a pressure increase, and originated from the position near the wafer edge.

Wafer Edge Profile Control for Improvement of Removal Uniformity in Oxide CMP

2012 ◽  
Vol 29 (3) ◽  
pp. 289-294
Author(s):  
Sung-Ha Choi ◽  
Ho-Bin Jeong ◽  
Young-Bong Park ◽  
Ho-Jun Lee ◽  
Hyoung-Jae Kim ◽  
...  
Keyword(s):  
Profile Control ◽  
Edge Profile ◽  
Wafer Edge

Numerical Analysis of Slurry Flow and Contact Pressure in CMP Considering the Effects of Retaining Ring

2016 ◽  
Vol 1136 ◽  
pp. 338-342
Author(s):  
Chao Li ◽  
Ping Zhou ◽  
Zhu Ji Jin ◽  
Bi Zhang ◽  
Shuang Ji Shi
Keyword(s):  
Contact Pressure ◽  
First Generation ◽  
Second Generation ◽  
Removal Rate ◽  
Elastohydrodynamic Lubrication ◽  
Contact Pressure Distribution ◽  
Slurry Flow ◽  
Retaining Ring ◽  
Edge Exclusion ◽  
Slurry Flow Rate

Retaining ring which keeps the wafer in place is an essential component in chemical mechanical polishing. Meanwhile, it helps to reduce the edge exclusion region where the material removal rate deviates significantly from that of the central region of the wafer. However, it may increase the slurry flow resistance and hence decrease the slurry flow rate. For properly designing a retaining ring of reasonable structure, the effects of retaining ring on slurry flow and contact pressure distribution in CMP process are analyzed by the mixed elastohydrodynamic lubrication model. It is found that the slurry flow is sensitive to the protrusion height of retaining ring used in the first generation carrier. The same as the first generation carrier, the slurry flow is obviously reduced with increasing pressure acting on the retaining ring in the second generation carrier. In addition, the floating retaining ring used in the second generation CMP carrier has better performance and is more controllable than the fixed retaining ring used in the first generation CMP carrier.

Sign in / Sign up

Export Citation Format

Share Document