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An additional ultrashallow boron-based plasma doping (PLAD) was carried out into the source/drain contacts for both pMOS and nMOS devices without masks. The PLAD using either B2H6 or BF3 gas in a mild energy to ultralow energy (ULE) regime, which are roughly equivalent to 1.5–0.2-keV energy and 1–3 $\times 10^{16}$ /cm $^{2}$ dose regime beam-line B implants, were utilized for this process. The pMOS devices exhibit significant performance improvements, including $\sim 80$ % lower contact resistances, similar threshold and subthreshold voltage characteristics, and $\sim 15$ %–30% higher drive currents, without degrading OFF current. Using ULE BF3 PLAD, the nMOS devices also show performance improvements, including $\sim 50$ % lower contact resistances, similar threshold and subthreshold voltage characteristics, and $\sim 4$ % higher drive currents without degrading OFF current. The mechanism of the nMOS device performance improvement can be attributed to the Schottky barrier height lowering effect and deactivation improvement. It significantly reduces cost because this one low-cost PLAD module eliminates two photo steps, one implant step, and two photo removing/cleaning steps.

This work demonstrates that the sequence of a Ge co-implant with a B 2 H 6 PLAD in the source/drain is very critical in order to improve advanced PMOS performance. Locating the Ge co-implant after the B 2 H 6 PLAD resulted in higher total retained B dose and less implant damage. PMOS performance was significantly improved compared to B 2 H 6 PLAD without the Ge co-implant or Ge co-implant before B 2 H 6 PLAD. The Ge implant energy was optimized to locate the Ge peak around the B deposition layer/Si substrate interface for a better knocking effect and less implant damage. With the optimized Ge implant conditions the source/drain contact resistance and sheet resistance were significantly reduced, while the junction leakage current was not degraded. As a result, PMOS I ds improved by 12%, transconductance KL improved by 14%, and I OFF variation improved by 33% without significant change in mean I OFF . This process helps overcome technical challenges of B 2 H 6 PLAD, providing a path for continued scaling of PMOS junction depth with improved device performance.

Comparison study of doping a 3-D trench transistor structure is carried out by beam-line (BL) implant and plasma doping (PLAD) methods. Electron holography (EH) is used as a powerful characterization method to study 2-D cross-sectional doping profiles of arsenic-based doping processes. Quantitative definitions of junction depths xj in both vertical and lateral directions can be obtained. Good correlations of 2-D EH dopant profiles, 1-D secondary ion mass spectrometry/angle-resolved X-ray electron spectroscopy impurity profiles, and device electrical parameters are demonstrated. The results reveal an advantage of PLAD over BL implant: a much larger effective implant area for 3-D trench bottom. It leads to a deeper vertical junction depth xj(V) with a larger lateral junction depth xj(L). It is due to the PLAD technology with less angle variation issues and no line of sight shadowing effect. Enhancing the dopant lateral straggle by PLAD at the trench bottom is particularly useful for nonplanar device structures with low resistance buried dopant layers.

The continuous anodic oxidation technique/differential Hall effect technique is used to study damage engineering of ultralow energy doping. It has been found that the scattering defect concentrations of the beam-line (BL) implants strongly correlate to the implant ion specie atomic mass unit and energy. Plasma doping (PLAD) seems to show a different mechanism for scatter defects. PLAD processes can have an in situ B-deposited film during implant and have less direct ion bombardment on the Si surface. The low scattering defect concentrations of PLAD implants (B2H6 and BF3) indicate that PLAD implants show an intrinsic advantage over BL counterparts in the current process regime.

New carrier drift mobility data for boron-, phosphorus-, and arsenic-doped Si in a low-energy high-dose implant regime are measured and studied using a continuous anodic oxidation technique/differential Hall effect technique. The data show that, when the doping concentration is >; 1020/cm3, both the hole and electron mobility values are lower than the conventional model predictions, and the electron mobility of the As-doped Si is lower than that of the P-doped ones. The data also show that, when the doping concentration is >; 1021/cm3 the hole mobility in the B-doped Si and the electron mobility in the P-doped Si are almost equal and reach as low as ~40 cm2/V · s, and the electron mobility of the As-doped Si is the lowest and reaches ~30 cm2/V · s. These mobility data are much lower than the conventional model predictions and are also lower than the previously published data. For the ULSI device and circuit analyses, simulations, and designs, these new mobility data need to be taken into consideration.

Angle-resolved X-ray photoelectron spectroscopy method was used to study self-sputtering effects of different n-type low-energy doping techniques, including conventional monoatomic 75As and 31P beam-line ion implants and AsH3 plasma doping (PLAD). It has been found that the self-sputtering effects of the beam-line implants correlate with the mass of ion species. As beam-line implant shows more serious self-sputtering effect than monoatomic P and B beam-line implants. Very low energy P implants show surface-swelling phenomena. PLAD process using AsH3 gas species has no sputtering effects but has slight deposition under current process condition.

Comparing with conventional spreading resistance profiling and differential Hall effect (DHE) methods, the continuous anodic oxidation technique/DHE (CAOT/DHE) technique may achieve more reasonable profiles of carrier concentration nh(x), mobility muh(x), and resistivity rho(x) and more reasonable carrier dose and xj in Si substrate. It has been successfully used to study ultralow energy doping techniques including B beam-line implant and B2H6 plasma doping (PLAD). CAOT/DHE data support the fact that the devices fabricated by PLAD achieve improvement to those fabricated by beam-line implant because PLAD offered higher surface carrier concentration and carrier dose. CAOT/DHE data quantitatively verify the so-called solid solubility limit activation theory - the carrier profiles and secondary ion mass spectrometry (SIMS) B impurity profiles under BSS are very well consistent on both beam-line and PLAD implants. As a cheaper and standard metrology, the SIMS/ARXPS method with the solid solubility limit activation theory may be used to quantitatively or semiquantitatively study the doping and activation processes.

We extensively investigate tool and recipe set-up dependence of the ultra-shallow junctions (USJ) doped by the boron-based ultra-low energy (ULE) beam-line (BL) implants. Recipes set-up includes different tools, energies, implant temperatures, and deceleration ratios. Channeling effect and energy contamination issues are de-coupled by drift and deceleration mode implants. A channeling effect factor (CEF) is defined and quantified. Channeling effect is found to be a major factor causing deeper profiles and long tails (x j ). Channeling effect gets worse when the implant energy is reduced due to less self-PAI effect (with less damage). Low temperature (−100 °C) implant does not effectively reduce channeling effect. Deceleration mode implant increases tail (x j ) due to energy contamination as a secondary order effect.

Plasma immersion ion implantation (PIII) technology is an alternative that overcomes the limitations of conventional beam line ion implantation for shallow, high dose and 3D doping on advanced memory and logic devices. This technique also delivers a better CoO as the result of higher productivity, smaller footprint and lower operating costs. With the requirements of new device architecture such as FINFET or FD-SOI for Logic, reduction of cell sizes for Memories, or 3D integration for “More than Moore” applications, a shallow profile is not the only critical objective. Amorphization and defects prevention become key points to allow good recrystallization and activation after annealing while reducing the thermal budget. IBS has developed and implemented the technique of high temperature implantation (up to 500°C) on the PIII system, PULSION®. In this paper, we present the impact of high temperature AsH3 Plasma doping in silicon. ARXPS (Angle Resolution X-ray Photoelectron Spectroscopy), SIMS (Secondary Ion Mass Spectrometry), and TEM (Transmission Electron Microscopy) analysis are used to study impact of the temperature on doping profiles and amorphization layer thickness. We show that when “high” acceleration voltage and high doses are used, thickness of the amorphization layer is drastically reduced (figure 1), and when lower acceleration voltage is used, amorphization layer can be totally suppressed.

Plasma immersion ion implantation (PIII) technology is known as an alternative to overcome the limitations of conventional beam line ion implantation for shallow, high dose and 3D doping on advanced memory and logic devices. This technique also shows a better CoO as the result of higher productivity, smaller footprint and lower operating costs. Implementation in production for P-type doping and development of N-type applications address issues from the challenges linked to the use of hydrides, especially in the case of AsH3 and PH3. Problems of excessive deposition lead to difficult process integration and possible safety issues such as wafer out-gassing. [1]. Higher priced gases coupled with higher gas consumption compared to beam line are often mentioned as limitations. In this paper we present a full characterization (done at Micron and at IBS) of AsH3 plasma implantation using PULSION® (PIII tool produced by IBS). Due to its unique remote source design, PULSION® allows a wider process window using lower gas flows [2]. These design advantages minimize the before mentioned drawbacks allowing easier process integration [3]. AES (Auger Electron Spectroscopy), ARXPS (Angle Resolution X-ray Photoelectron Spectroscopy), TOF-SIMS & D-SIMS (Secondary Ion Mass Spectrometry), and TEM (Transmission Electron Microscopy) analysis are used to study deposition, doping profiles, and amorphization as a function of acceleration voltage and dose. The effect of dose on sheet resistance after Spike anneal is discussed, as well as the effect of possible hydrogen dilution. Out-gassing measurements are also presented.

Conventional beam-line (BL) implant shows a poor scalability of profiles (x j ) versus energy at the ULE implant regime due to serious channeling effect and energy contamination issue. B 2 H 6 PLAD shows intrinsic channeling effect immunity with a totally different mechanism. An in-situ, build-in B deposition layer is formed during PLAD process as a screen amorphous layer to minimize channeling effect and reduce the surface damage residues as well. For above reasons, B 2 H 6 PLAD shows a good scalability of profiles (x j ) versus energy, and achieves better R S -x j characteristics and x j abruptness, and then better device performance including lower series and contact resistances, better I ON /I OFF ratio and less short channel effect (SCE), etc. than BL implant counterparts.

Toppling during clean process is a general structure issue when we scale down critical dimension (CD)/increase aspect ratio (AR) and density of the nano structures. In this paper, we demonstrated a novel process with CH 4 PLAD (plasma doping) conformal process to eliminate the toppling issue. A uniform C deposition layer from CH 4 PLAD process wrapped the whole structure on the top/bottom/sidewall and made structure more robust during clean process. As a result, the toppling issue could be eliminated. The PLAD condition should be chosen in the “highly collisional case” in order to maximize deposition and minimize implant. ARXPS (angle resolved X-ray photoelectron spectroscopy) and PDP1 (plasma device planar 1D) simulation were applied to define the “highly collisional case”. There was a strong correlation between implant dose and toppling reduction rate. Besides CH 4 PLAD, other neutral species such as GeH 4 PLAD may also be used for this process. The advantages of this process include no thermal Dt, fast throughput and low cost. It may help us to continue scaling down the structures with higher AR/smaller CD/higher density.

Plasma doping (PLAD) shows very different impurity profiles compared to the conventional beam-line-based ion implantations due to its non-mass separation property and plasma environment. There is no simulation for PLAD process so far due to a lack of a dopant profile model. Several factors determine impurity profiles of PLAD process. The most significant factors are: plasma chemistry and deposition/etching characteristics of multi-ion species plasmas. In this paper, we present plasma chemistry and deposition/etching characteristics of PLAD processes versus co-gas dilutions. Four dopant plasmas including B2H6, BF3, AsH3, and PH3, and two non-dopant plasmas including CH4 and GeH4 are studied and demonstrated.

The effects of self-amorphization thickness on boron (B) dopant depth profile in silicon (Si) were investigated by cold temperature implant, down to −100°C. Significant B junction depth (Xj) reduction can be achieved for as-implant and post anneal, when the self-amorphization thickness is comparable or deeper than the B implant projected range (implant peak position) and the implant is completed at sufficiently low temperature. There is a transition temperature regime before the appropriate temperature is reached. The Xj reduction is stagnated due to the thickness limitation and the degree of self-amorphization. Temperature dependent surface damage, self-amorphization thickness, diffusion, and activation were also studied. Improvement in carrier mobility is more significant in certain dose regimes at low temperatures. The findings of this study provide important insight in to the control of the junction profile for smaller atomic mass unit (AMU) species, like B, by using the self-amorphization effect at cold temperatures.