Silicon Nitride Film Removal During Chemical Mechanical Polishing Using Ceria-Based Dispersions

Dandu, P.R. Veera; Peethala, B.; Amanapu, H. P.; Babu, S. V.

doi:10.1149/1.3596181

Cited by 27 publications

(25 citation statements)

References 36 publications

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“…The silicon nitride RR is suppressed when the reactivity of Ce 3+ on the ceria abrasive surface is blocked and/or the hydrolysis reaction of the nitride conversion to silicon dioxide is hindered due to the adsorption of different additives. 65 Using zirconia-and silica-based dispersions, high silicon nitride and low silicon dioxide removal rates were reported by Natarajan et al 66 Without any additives, zirconia gave a reverse selectivity of 78 at pH 4, while 2 wt% arginine in a 10 wt% silica slurry at pH 8 gave a reverse selectivity of 7. 66 The exact mechanism of silicon nitride polishing with these slurries was not explained.…”

Section: Reverse Selectivitymentioning

confidence: 91%

Shallow Trench Isolation Chemical Mechanical Planarization: A Review

Ramanathan

Dandu

Babu

2015

ECS J. Solid State Sci. Technol.

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Electrical isolation of the billion or so active components in each integrated device is achieved using shallow trench isolation (STI) which requires chemical mechanical planarization (CMP) involving silicon dioxide removal at a high rate and stopping on an underlying silicon nitride film. Several colloidal slurries with various additives can yield the desired high rate selectivity between the oxide and nitride films during CMP while maintaining an acceptably low nitride rate. Here, many of such high selectivity STI CMP slurries described in the literature are reviewed along with the characteristics of the colloidal dispersions like the abrasives, additives, the interactions between them and with the films being planarized and the associated pH range in which the high selectivity is observed. The mechanisms proposed to explain the high reactivity of ceria with oxide, the role of additives in suppressing the nitride removal rate and resulting high selectivity are discussed. Reduction of a multitude of defects in post-CMP processed STI structures still remains an important challenge, especially as the feature sizes continue to shrink. Chemical mechanical planarization (CMP) is one of the important enabling processes in facilitating multilevel metallization (in some cases reaching up to 14 levels) and incorporation of novel gate and channel materials at the component level in modern semiconductor device manufacturing where its use has become widespread and ubiquitous.1-6 Here, we review recent advances and remaining challenges in one specific application of CMP, the shallow trench isolation (STI) process. STI is a method of electrically isolating active areas using trenches created in the Si substrate around the active elements and filling it with an insulating dielectric, such as silicon dioxide or silicon oxy-nitride or silicon carbonitride.7-11 Process details of the STI structures are available in numerous publications. There are a multitude of techniques available for oxide deposition and even though the resulting oxides have very different properties, for simplicity we do not distinguish between them in this review. For completeness and ease of reference, a schematic representation of the STI process is given in Figure 1. While the trenches are being filled, silicon dioxide also deposits over unwanted areas on the entire wafer (since selective deposition in trenches only is not possible) creating an uneven topography. The excess and unwanted oxide has to be completely removed and CMP has proven to be the only viable and robust global and local planarization capable process technology.Here, as shown in Figure 1, presence of a very thin silicon nitride stop layer (deposited on another thin pad oxide layer to control film stress) is an essential and integral part of the process. This nitride stop layer prevents any damage during planarization to the all-important epitaxially grown surface underneath and is itself removed by a wet etch process subsequent to the overburden oxide removal. Since the integrity of the...

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Section: Reverse Selectivitymentioning

confidence: 91%

Shallow Trench Isolation Chemical Mechanical Planarization: A Review

Ramanathan

Dandu

Babu

2015

ECS J. Solid State Sci. Technol.

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“…One of the hypotheses proposed to explain the effect of amino acids in suppressing the nitride removal rate is that there is a formation of hydrogen bond between the silicon nitride surface and amino acids (4). This hypothesis was further extended by veera dandu et al (6). It was proposed that in presence of amino acids, the Ce 3+ sites on the abrasives were blocked and the hydrolysis of the nitride surface was prevented.…”

Section: Introductionmentioning

confidence: 99%

Effect of La Doping of Ceria Abrasives for STI CMP

2014

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The nitride removal rate by ceria abrasives in presence of amino acids is altered by the purity of ceria. Commercial ceria obtained from Sigma-Aldrich with low purity (<90%) and with high purity (99.95%) were employed in the study. Polishing experiments showed that in presence of lanthanum in the abrasive, proline does not suppress nitride removal. In order to verify that the effect is mainly due to presence of lanthanum, ceria particles were synthesized with and without lanthanum doping. Three types of amino acids viz. proline, alanine and glutamic acid were used with the ceria particles. The removal rate results show that proline is sensitive to presence of lanthanum impurity in abrasive, while alanine and glutamic acid suppress the nitride removal irrespective of the purity of the abrasives. The abrasives were characterized using XRD. The adsorption of amino acids on abrasive was characterized by differential thermal analysis.

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“…Since it is well known that commercial ceria particles are available in a variety of forms and colors due to various impurities, we have chosen recently published results [2][3][4][5][6][7][8][9][10][11][12] in silicon dioxide CMP obtained using two types of ceria, one (d m ~180 nm) from Ferro Material Systems (see Table 1 below) and the other (d m ~60 nm) from Rhodia Inc. (Table 2) and different additives -amino acids, amines, carboxylic acids, and polymers. Both the particle size and pH influence these rates, but our focus here is only on understanding the chemical reactivity (the 'C' in CMP) of ceria abrasives in the presence of different additives in determining the silicon dioxide RRs.…”

Section: Resultsmentioning

confidence: 99%

“…(b) Silicon nitride removal: General presumption is that the suboxide formed on the silicon nitride surface during hydrolysis [7,8] is removed by the ceria abrasives, most likely in a manner similar to the removal of silicon dioxide films and hence the nitride removal rate cannot be enhanced easily while the oxide rate is kept low.…”

Section: Current Modelsmentioning

confidence: 99%

“…There are also other applications [1] where both silicon dioxide and silicon nitride film removal rates need to be suppressed. To meet these variable requirements, several ceria-based formulations [2][3][4][5][6][7][8][9][10][11][12] containing a variety of additives (amino acids, amines, and polymers) were developed to selectively polish silicon dioxide and silicon nitride films and have been extensively used for many technologically important applications in silicon device manufacturing. Several of these dispersions suppress silicon nitride RRs to <2 nm/min [1][2][3][4]8] but not the oxide RR; a few do the reverse, [7] i.e., suppress silicon dioxide RRs to <2 nm/min, whereas others suppress both silicon dioxide and silicon nitride RRs to <2 nm/min [6].…”

Section: Introductionmentioning

confidence: 99%

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The Role of Ce3+ vs. Ce4+ during the Polishing of Silicon Dioxide and Silicon Nitride Films using Ceria Abrasives

Dandu

Babu

2012

Imaging and Applied Optics Technical Papers

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Removal rate mechanisms of silicon dioxide and silicon nitride films during chemical mechanical polishing using ceria particles-based dispersion in the presence and absence of different additives are discussed. Our results show that ceria particles give high silicon dioxide and silicon nitride removal rates due to the reactivity of the Ce 3+ species with silicon dioxide or the sub-oxide formed on the silicon nitride surface by hydrolysis. With several additives, complete blockage of the reactive species and the reduction of oxide and nitride removal rates to <2 nm/min occur when the amount of the additive adsorbed has reached a limiting value. Silicon nitride removal rates can also be suppressed to <2 nm/min when the conversion of the nitride surface to suboxide is hindered due to the adsorption of additives on the nitride surface.

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Silicon Nitride Film Removal During Chemical Mechanical Polishing Using Ceria-Based Dispersions

Cited by 27 publications

References 36 publications

Shallow Trench Isolation Chemical Mechanical Planarization: A Review

Shallow Trench Isolation Chemical Mechanical Planarization: A Review

Effect of La Doping of Ceria Abrasives for STI CMP

The Role of Ce3+ vs. Ce4+ during the Polishing of Silicon Dioxide and Silicon Nitride Films using Ceria Abrasives

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