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Optimization of ISBD embedded SiGe layers to prevent delamination process for MOSFET applications
Solid-State Electronics 110 (2015) 23–28
Contents lists available at ScienceDirect
Solid-State Electronics journal homepage: www.elsevier.com/locate/sse
Optimization of ISBD embedded SiGe layers to prevent delamination process for MOSFET applications Joanna Wasyluk ⇑, Yang Ge, Kai Wurster, Markus Lenski, Carsten Reichel GLOBALFOUNDRIES Dresden Module One LLC & Co. KG, Wilschdorfer Landstrasse 101, 01109 Dresden, Germany
a r t i c l e
i n f o
Article history: Available online 30 March 2015 Keywords: CMOS processing in situ boron doped SiGe epitaxy Delamination HN3/O2 plasma strips
a b s t r a c t An interaction between in situ boron doped SiGe layers deposited by low pressure chemical vapor deposition and NH3 plasma treatments was studied in this work. It is shown that NH3 plasma strips introduce H atoms into SiGe layer which further leads to unwanted blistering and exfoliation of the SiGe layer. The SiGe layers with varied boron profiles were examined in this work in order to understand influence of B doping on H accumulation. It is shown that B peak at SiGe/Si interface can be modulated by the temperature and pressure changes between the layers’ deposition. It was found that less H atoms diffuse into ISBD SiGe layer with higher B peak at Si cap/main SiGe layer. The SiGe layer with removed B peak at buffer/main SiGe layer interface and increased B peak at Si cap was proven to be delamination free and robust for HN3 plasma strips. Ó 2015 Published by Elsevier Ltd.
1. Introduction Selective epitaxial growth of SiGe layers is well known and widely used technique for performance improvement of pMOSFET devices. Embedded strained SiGe (eSiGe) layers applied for source/ drain applications enhance hole mobility of the transistor by inducing uniaxial compressive strain into Si-channel [1,2]. One of the common SiGe techniques used for source/drain (S/D) formation is in situ boron doped (ISBD) SiGe epitaxy [3]. It is well known that ISBD eSiGe S/D device exhibits higher drive current than a boronimplanted eSiGe S/D device due to the fact that all B atoms locate into substitutional sites of SiGe lattice structure. One of the technology concerns in integrating eSiGe in pMOSFET processing is subsequence NH3 plasma treatments used for photoresist removal. The NH3 plasma strips introduce H atoms into SiGe layer and further lead to unwanted blistering and exfoliation of the SiGe layer which degrades yield performance of the devices. This unwanted layer damage is described in this work as SiGe delamination. Number of publications shows that B concentration and distribution in Si has an impact H accumulation/trapping effect [4,5]. The splitting of the Si layer after H implantation has been observed to occur near the location of the B peak [4]. Similar results were also observed for Ga implanted Si [6]. Höchbauer et al. has also shown that the boron atoms lead to the reduction of annealing ⇑ Corresponding author. Tel.: +49 (0)351 277 42 86. E-mail address: [email protected] (J. Wasyluk). http://dx.doi.org/10.1016/j.sse.2015.01.014 0038-1101/Ó 2015 Published by Elsevier Ltd.
temperature and annealing time required for layer splitting [5]. Similar correlation between incorporated H atoms during NH3 plasma strip and B profile is presented in this paper but for ISBD SiGe layers. In this work, we examine the effect of B doping in ISBD SiGe layers on delamination process after subsequence NH3 plasma treatments. 2. Experiment Recessed S/D SiGe have been fabricated on 300 mm Cz wafers. After active area definition by shallow trench isolation (STI), n- and p-well have been implanted. Extension/halo implants have been performed followed by subsequent dopant activation at around 1000 °C. S/D trenches were etched with a depth in the range of 50–60 nm and refilled with ISBD SiGe epitaxial layers using low pressure chemical vapor deposition (LPCVD). The trilayer stacks consist of buffer SiGe layer with low Ge content (in the range of 20–30%), main SiGe layer with high Ge content (in the range of 35–40%) and with varied B profile and Si cap layer on top of SiGe. The layers’ deposition was performed at pressure of 3 to 10 Torr and at temperature range of 620–780 °C using the reactive gases DCS, SiH4, GeH4, HCl and B2H6 in order to achieve SiGe layer with different B profiles. H incorporation into SiGe layer was achieved by two experiments. First experiment simulated a real process flow of MOSFET fabrication. After SiGe epitaxy wafers have been processed with the subsequent nFET implantations. During these multiple implantation steps pFET devices have been covered with photoresist.
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NH3/O2 plasma strip (in temperature range of 250–300 °C) was used for the photo resist removal after every nFET implantation and at this step H atoms were incorporated into SiGe layers which further caused delamination. In the second experiment wafers were exposed to multiple plasma strips directly after SiGe epitaxy. In this case, SiGe layers have not been covered with photoresist and therefore more H atoms could diffuse into the layers. Delamination of SiGe layers was evaluated by scanning electron (SEM) and tunneling electron (TEM) microscopes. Compositional layer analyses were performed by TOF-SIMS spectroscopy. Boron composition of SiGe layers was measured directly after SiGe deposition and H content after subsequent plasma treatment.
3. Results Fig. 1 presents the exemplary top view SEM and cross section TEM images from delaminating (a and b) and delamination-free SiGe layers (c and d). It is demonstrated (Fig. 1a and b) that NH3 plasma strips introduce H atoms into SiGe layer and further lead to unwanted blistering and exfoliation of the SiGe layer which degrades yield performance of the devices. This unwanted layer damage is described in this work as eSiGe delamination and occurs at low temperature regime (250–300 °C) in comparison to wellknown Smart CutÓ technology. As can be seen in Fig. 1(a) characteristic blisters and cracks are observed due to present of molecular H2 in the SiGe layer. Blistering and separation of the layer occur inside the main SiGe layer or at buffer/main layer interface (see Fig. 1b). The dissociation energy of the Ge–H bond (288 kJ/mol) is lower than the Si–H bond, which suggests that process involving dissociation of Ge–H bonds occur at lower temperatures than similar process for Si–H bonds (318 kJ/mol) [7].
3.1. Plasma treatments in a real process flow In this section, the effect of B doping in ISBD SiGe layers on delamination process is examined for a real process flow of MOSFET fabrication with resist coating and with subsequent nFET implantations. Fig. 2(a) presents B profile of ISBD SiGe layer from the wafer center and edge. Si cap and buffer SiGe layer have very low B content while the main SiGe layer is deposited with higher B concentration in range of 1–2 1020 atoms/cm3. As can be seen from Fig. 2(a) boron profile for main SiGe layer consists of two characteristic peaks at layer’s interfaces. These B pile ups are correlated to the temperature and pressure changes between layers’ deposition. In addition, detected amount of boron at wafer edge is higher than at wafer center, especially when considering B peak at Si Cap/main SiGe layer interface. High amount of H in a range of 1–3 1020 atoms/cm3 (two orders higher than H level in the Si substrate) was detected by TOF-SIMS after plasma strip treatment (Fig. 2b) and this SiGe layer showed delamination. It is demonstrated that by removing B peak at bottom and increasing B peak at top of the main layer (Fig. 3a) H level after plasma strip in main SiGe layer can be significantly reduced and well matched to the H level in the Si substrate (Fig. 3b). This can be achieved by optimizing the temperature and pressure transition between the buffer and main SiGe layer depositions. The SiGe layers deposited in such a way did not show delamination. Boron concentration and distribution in ISBD SiGe impact H accumulation/trapping effect, which is in agreement with previous studies done for Si [3,4]. Characteristic B pile ups at the SiGe layer interfaces attract H atoms which in higher temperature are transferred to molecular H2 and create voids (delamination) in SiGe layers. In addition, the presence of boron atoms lead to the reduction of annealing temperature and
Fig. 1. Top view SEM image and cross section TEM of delaminating (a and b) and delamination-free ISBD SiGe layer (c and d).
J. Wasyluk et al. / Solid-State Electronics 110 (2015) 23–28
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Fig. 2. Boron (a) and H profile (b) of delaminating ISBD SiGe layer measured by TOF-SIMS from center and edge.
Fig. 3. Boron (a) and H profile (b) of delamination-free ISBD SiGe layer measured by TOF-SIMS from center and edge.
time required for layer splitting [5]. This explains why delamination of SiGe layers was observed for resist strip already at T < 300 °C. Fig. 4(a and b) presents B profiles for SiGe layers deposited without B peaks at the bottom of the layers and corresponding H profile for these layers (see Fig. 4c and d). For these samples (sample I and sample II), two different levels of B peaks at the top of the SiGe layer were examined. H level in SiGe main layer measured from wafer edge after resist removal plasma treatment is very low – at the same level as in bulk Si. For both samples delamination was not observed. It is shown that B peak at level of 1.8 1020 atoms/ cm 3 and higher at Si cap/main SiGe layer prevents from H diffusion into ISBD SiGe layer in the real flow processing and therefore prevent from delamination. 3.2. Multiple plasma treatment directly after SiGe deposition In this section, the effect of B doping in ISBD SiGe layers on delamination process is examined by applying multiple NH3 plasma strips directly after SiGe epitaxy. Fig. 5 presents B profiles
and corresponding H profiles for delamination-free and delaminating SiGe layers. As already shown in Section 2.1 layer with removed B peak between buffer and main SiGe layer and increasing B peak at Si cap prevents hydrogen diffusion deep into SiGe layer and therefore prevents from delamination (see Fig. 5a). H profile for delamination free SiGe layer shows high H peak at Si cap (which is trapped by accumulated boron atoms) and low H level in SiGe main layer comparable to the one in Si substrate (see Fig. 5b). H profile for the delaminating layer (with two B peaks at bottom and top main SiGe layer’s interface) shows three strong H peaks: at Si cap interface, in main and in buffer SiGe layers. H profile for delaminating layer after direct multiple plasma treatment looks differently than after plasma treatments in a real process flow (see Fig. 5b in comparison to Fig. 2b). It is clear that more H atoms are diffused to SiGe layer during NH3 plasma treatment without protecting photoresist layer. H level for sample with direct multiple plasma treatment is almost an order higher and H projection range is deeper than for the sample which was processed in a real process flow and was covered with photoresist.
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Fig. 4. Boron profiles (a and b) and corresponding H profile (c and d) measured by TOF-SIMS for ISBD SiGe layers with different B peak at Si cap/main layer interface (a – sample I, b – sample II).
Fig. 5. Boron (a) and H profile (b) of delamination-free and delaminating ISBD SiGe layers measured by TOF-SIMS from wafer center.
J. Wasyluk et al. / Solid-State Electronics 110 (2015) 23–28
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Fig. 6. Boron profiles (a–c) and corresponding H profiles (d–f) measured by TOF-SIMS for ISBD SiGe layers with different B peak at Si cap/main layer interface (a – sample III, b – sample IV, c – sample V).
Fig. 6(a–c) presents B profiles for SiGe layers deposited without B peaks at the bottom of the layers and corresponding H profile for these layers (see Fig. 5a–c). Different levels of B peaks at the top of
the SiGe layer were examined in order to understand its correlation to H accumulation. It is shown that with higher B peak at Si cap/main SiGe layer less total H amount is detected in ISBD SiGe layer.
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J. Wasyluk et al. / Solid-State Electronics 110 (2015) 23–28
Therefore B peak at Si cap/main SiGe layer interface clearly acts as ‘‘screening’’ peak which attracts H atoms and block H from diffusion further into SiGe layer and prevent layer from the delamination. 4. Conclusions An interaction between ISBD SiGe layers deposited by LPCVD and NH3 plasma treatments is described in this paper. It is demonstrated that NH3 plasma strips introduce H atoms into SiGe layer which further lead to unwanted blistering and delamination of the SiGe layer during low temperature processing (250–300 °C). The SiGe layers with varied boron profiles are examined in details in order to understand its correlation to H accumulation. It is shown that B peaks at SiGe/Si interfaces can be modulated by the temperature and pressure changes between layers’ deposition. Less total H amount is observed in ISBD SiGe layer with higher B peak at Si cap/main SiGe layer. Delamination free SiGe deposition without B peak at buffer/main SiGe layer interface and increased B peak at Si cap was invented. It is shown that the B peak at Si cap/main SiGe layer interface clearly acts as ‘‘screening’’ peak which attracts H atoms and block H from diffusion further into SiGe layer and prevent layer from the delamination.
Acknowledgements Author would like to express sincere thanks to Christoph Klein, Stefan Nawka and Susanne Ohsiek from Center for Complex Analysis for TOF-SIMS measurements. References [1] Ghani T, Armstrong M, Auth C, et al. A 90-nm high volume manufacturing logic technology featuring novel 45-nm gate length strained silicon CMOS transistors. In: IEDM Tech Dig; 2003. p. 978–80. [2] Nouri F, Verheyen P, et al. A systematic study of trade-offs in engineering a locally strained pMOSFET. In: IEDM Tech Dig, vol. 107; 2004. p. 1055–8. [3] Hartmann JM, Gonzatti F, Barnes JP, Fillot F, Billon T. Growth kinetics and Bdoping of very high G content Si1 xGex for source and drain engineering. ECS Trans 2007;6(1):397–400. [4] Tong Q-Y, Scholz R, Gösele U, Lee T-H, Huang L-J, Chao Y-L, et al. A smarter-cut approach to low temperature silicon layer transfer. Appl Phys Lett 1998;72:49. [5] Höchbauer T, Walter KC, Schwarz RB, Nastasi M, Bower RW, Ensinger W. The influence of boron ion implantation on hydrogen blister formation in n-type silicon. J Appl Phys 1999;86:4176. [6] Marwick AD, Oehrlein GS, Wittmer M. High hydrogen concentrations produced by segregation into p+ layers in silicon. Appl Phys Lett 1991;59(2):198. [7] Cottrell TL. The strengths of chemical bonds. second ed. London: Butterworths; 1958.
Contents lists available at ScienceDirect
Solid-State Electronics journal homepage: www.elsevier.com/locate/sse
Optimization of ISBD embedded SiGe layers to prevent delamination process for MOSFET applications Joanna Wasyluk ⇑, Yang Ge, Kai Wurster, Markus Lenski, Carsten Reichel GLOBALFOUNDRIES Dresden Module One LLC & Co. KG, Wilschdorfer Landstrasse 101, 01109 Dresden, Germany
a r t i c l e
i n f o
Article history: Available online 30 March 2015 Keywords: CMOS processing in situ boron doped SiGe epitaxy Delamination HN3/O2 plasma strips
a b s t r a c t An interaction between in situ boron doped SiGe layers deposited by low pressure chemical vapor deposition and NH3 plasma treatments was studied in this work. It is shown that NH3 plasma strips introduce H atoms into SiGe layer which further leads to unwanted blistering and exfoliation of the SiGe layer. The SiGe layers with varied boron profiles were examined in this work in order to understand influence of B doping on H accumulation. It is shown that B peak at SiGe/Si interface can be modulated by the temperature and pressure changes between the layers’ deposition. It was found that less H atoms diffuse into ISBD SiGe layer with higher B peak at Si cap/main SiGe layer. The SiGe layer with removed B peak at buffer/main SiGe layer interface and increased B peak at Si cap was proven to be delamination free and robust for HN3 plasma strips. Ó 2015 Published by Elsevier Ltd.
1. Introduction Selective epitaxial growth of SiGe layers is well known and widely used technique for performance improvement of pMOSFET devices. Embedded strained SiGe (eSiGe) layers applied for source/ drain applications enhance hole mobility of the transistor by inducing uniaxial compressive strain into Si-channel [1,2]. One of the common SiGe techniques used for source/drain (S/D) formation is in situ boron doped (ISBD) SiGe epitaxy [3]. It is well known that ISBD eSiGe S/D device exhibits higher drive current than a boronimplanted eSiGe S/D device due to the fact that all B atoms locate into substitutional sites of SiGe lattice structure. One of the technology concerns in integrating eSiGe in pMOSFET processing is subsequence NH3 plasma treatments used for photoresist removal. The NH3 plasma strips introduce H atoms into SiGe layer and further lead to unwanted blistering and exfoliation of the SiGe layer which degrades yield performance of the devices. This unwanted layer damage is described in this work as SiGe delamination. Number of publications shows that B concentration and distribution in Si has an impact H accumulation/trapping effect [4,5]. The splitting of the Si layer after H implantation has been observed to occur near the location of the B peak [4]. Similar results were also observed for Ga implanted Si [6]. Höchbauer et al. has also shown that the boron atoms lead to the reduction of annealing ⇑ Corresponding author. Tel.: +49 (0)351 277 42 86. E-mail address: [email protected] (J. Wasyluk). http://dx.doi.org/10.1016/j.sse.2015.01.014 0038-1101/Ó 2015 Published by Elsevier Ltd.
temperature and annealing time required for layer splitting [5]. Similar correlation between incorporated H atoms during NH3 plasma strip and B profile is presented in this paper but for ISBD SiGe layers. In this work, we examine the effect of B doping in ISBD SiGe layers on delamination process after subsequence NH3 plasma treatments. 2. Experiment Recessed S/D SiGe have been fabricated on 300 mm Cz wafers. After active area definition by shallow trench isolation (STI), n- and p-well have been implanted. Extension/halo implants have been performed followed by subsequent dopant activation at around 1000 °C. S/D trenches were etched with a depth in the range of 50–60 nm and refilled with ISBD SiGe epitaxial layers using low pressure chemical vapor deposition (LPCVD). The trilayer stacks consist of buffer SiGe layer with low Ge content (in the range of 20–30%), main SiGe layer with high Ge content (in the range of 35–40%) and with varied B profile and Si cap layer on top of SiGe. The layers’ deposition was performed at pressure of 3 to 10 Torr and at temperature range of 620–780 °C using the reactive gases DCS, SiH4, GeH4, HCl and B2H6 in order to achieve SiGe layer with different B profiles. H incorporation into SiGe layer was achieved by two experiments. First experiment simulated a real process flow of MOSFET fabrication. After SiGe epitaxy wafers have been processed with the subsequent nFET implantations. During these multiple implantation steps pFET devices have been covered with photoresist.
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NH3/O2 plasma strip (in temperature range of 250–300 °C) was used for the photo resist removal after every nFET implantation and at this step H atoms were incorporated into SiGe layers which further caused delamination. In the second experiment wafers were exposed to multiple plasma strips directly after SiGe epitaxy. In this case, SiGe layers have not been covered with photoresist and therefore more H atoms could diffuse into the layers. Delamination of SiGe layers was evaluated by scanning electron (SEM) and tunneling electron (TEM) microscopes. Compositional layer analyses were performed by TOF-SIMS spectroscopy. Boron composition of SiGe layers was measured directly after SiGe deposition and H content after subsequent plasma treatment.
3. Results Fig. 1 presents the exemplary top view SEM and cross section TEM images from delaminating (a and b) and delamination-free SiGe layers (c and d). It is demonstrated (Fig. 1a and b) that NH3 plasma strips introduce H atoms into SiGe layer and further lead to unwanted blistering and exfoliation of the SiGe layer which degrades yield performance of the devices. This unwanted layer damage is described in this work as eSiGe delamination and occurs at low temperature regime (250–300 °C) in comparison to wellknown Smart CutÓ technology. As can be seen in Fig. 1(a) characteristic blisters and cracks are observed due to present of molecular H2 in the SiGe layer. Blistering and separation of the layer occur inside the main SiGe layer or at buffer/main layer interface (see Fig. 1b). The dissociation energy of the Ge–H bond (288 kJ/mol) is lower than the Si–H bond, which suggests that process involving dissociation of Ge–H bonds occur at lower temperatures than similar process for Si–H bonds (318 kJ/mol) [7].
3.1. Plasma treatments in a real process flow In this section, the effect of B doping in ISBD SiGe layers on delamination process is examined for a real process flow of MOSFET fabrication with resist coating and with subsequent nFET implantations. Fig. 2(a) presents B profile of ISBD SiGe layer from the wafer center and edge. Si cap and buffer SiGe layer have very low B content while the main SiGe layer is deposited with higher B concentration in range of 1–2 1020 atoms/cm3. As can be seen from Fig. 2(a) boron profile for main SiGe layer consists of two characteristic peaks at layer’s interfaces. These B pile ups are correlated to the temperature and pressure changes between layers’ deposition. In addition, detected amount of boron at wafer edge is higher than at wafer center, especially when considering B peak at Si Cap/main SiGe layer interface. High amount of H in a range of 1–3 1020 atoms/cm3 (two orders higher than H level in the Si substrate) was detected by TOF-SIMS after plasma strip treatment (Fig. 2b) and this SiGe layer showed delamination. It is demonstrated that by removing B peak at bottom and increasing B peak at top of the main layer (Fig. 3a) H level after plasma strip in main SiGe layer can be significantly reduced and well matched to the H level in the Si substrate (Fig. 3b). This can be achieved by optimizing the temperature and pressure transition between the buffer and main SiGe layer depositions. The SiGe layers deposited in such a way did not show delamination. Boron concentration and distribution in ISBD SiGe impact H accumulation/trapping effect, which is in agreement with previous studies done for Si [3,4]. Characteristic B pile ups at the SiGe layer interfaces attract H atoms which in higher temperature are transferred to molecular H2 and create voids (delamination) in SiGe layers. In addition, the presence of boron atoms lead to the reduction of annealing temperature and
Fig. 1. Top view SEM image and cross section TEM of delaminating (a and b) and delamination-free ISBD SiGe layer (c and d).
J. Wasyluk et al. / Solid-State Electronics 110 (2015) 23–28
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Fig. 2. Boron (a) and H profile (b) of delaminating ISBD SiGe layer measured by TOF-SIMS from center and edge.
Fig. 3. Boron (a) and H profile (b) of delamination-free ISBD SiGe layer measured by TOF-SIMS from center and edge.
time required for layer splitting [5]. This explains why delamination of SiGe layers was observed for resist strip already at T < 300 °C. Fig. 4(a and b) presents B profiles for SiGe layers deposited without B peaks at the bottom of the layers and corresponding H profile for these layers (see Fig. 4c and d). For these samples (sample I and sample II), two different levels of B peaks at the top of the SiGe layer were examined. H level in SiGe main layer measured from wafer edge after resist removal plasma treatment is very low – at the same level as in bulk Si. For both samples delamination was not observed. It is shown that B peak at level of 1.8 1020 atoms/ cm 3 and higher at Si cap/main SiGe layer prevents from H diffusion into ISBD SiGe layer in the real flow processing and therefore prevent from delamination. 3.2. Multiple plasma treatment directly after SiGe deposition In this section, the effect of B doping in ISBD SiGe layers on delamination process is examined by applying multiple NH3 plasma strips directly after SiGe epitaxy. Fig. 5 presents B profiles
and corresponding H profiles for delamination-free and delaminating SiGe layers. As already shown in Section 2.1 layer with removed B peak between buffer and main SiGe layer and increasing B peak at Si cap prevents hydrogen diffusion deep into SiGe layer and therefore prevents from delamination (see Fig. 5a). H profile for delamination free SiGe layer shows high H peak at Si cap (which is trapped by accumulated boron atoms) and low H level in SiGe main layer comparable to the one in Si substrate (see Fig. 5b). H profile for the delaminating layer (with two B peaks at bottom and top main SiGe layer’s interface) shows three strong H peaks: at Si cap interface, in main and in buffer SiGe layers. H profile for delaminating layer after direct multiple plasma treatment looks differently than after plasma treatments in a real process flow (see Fig. 5b in comparison to Fig. 2b). It is clear that more H atoms are diffused to SiGe layer during NH3 plasma treatment without protecting photoresist layer. H level for sample with direct multiple plasma treatment is almost an order higher and H projection range is deeper than for the sample which was processed in a real process flow and was covered with photoresist.
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Fig. 4. Boron profiles (a and b) and corresponding H profile (c and d) measured by TOF-SIMS for ISBD SiGe layers with different B peak at Si cap/main layer interface (a – sample I, b – sample II).
Fig. 5. Boron (a) and H profile (b) of delamination-free and delaminating ISBD SiGe layers measured by TOF-SIMS from wafer center.
J. Wasyluk et al. / Solid-State Electronics 110 (2015) 23–28
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Fig. 6. Boron profiles (a–c) and corresponding H profiles (d–f) measured by TOF-SIMS for ISBD SiGe layers with different B peak at Si cap/main layer interface (a – sample III, b – sample IV, c – sample V).
Fig. 6(a–c) presents B profiles for SiGe layers deposited without B peaks at the bottom of the layers and corresponding H profile for these layers (see Fig. 5a–c). Different levels of B peaks at the top of
the SiGe layer were examined in order to understand its correlation to H accumulation. It is shown that with higher B peak at Si cap/main SiGe layer less total H amount is detected in ISBD SiGe layer.
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Therefore B peak at Si cap/main SiGe layer interface clearly acts as ‘‘screening’’ peak which attracts H atoms and block H from diffusion further into SiGe layer and prevent layer from the delamination. 4. Conclusions An interaction between ISBD SiGe layers deposited by LPCVD and NH3 plasma treatments is described in this paper. It is demonstrated that NH3 plasma strips introduce H atoms into SiGe layer which further lead to unwanted blistering and delamination of the SiGe layer during low temperature processing (250–300 °C). The SiGe layers with varied boron profiles are examined in details in order to understand its correlation to H accumulation. It is shown that B peaks at SiGe/Si interfaces can be modulated by the temperature and pressure changes between layers’ deposition. Less total H amount is observed in ISBD SiGe layer with higher B peak at Si cap/main SiGe layer. Delamination free SiGe deposition without B peak at buffer/main SiGe layer interface and increased B peak at Si cap was invented. It is shown that the B peak at Si cap/main SiGe layer interface clearly acts as ‘‘screening’’ peak which attracts H atoms and block H from diffusion further into SiGe layer and prevent layer from the delamination.
Acknowledgements Author would like to express sincere thanks to Christoph Klein, Stefan Nawka and Susanne Ohsiek from Center for Complex Analysis for TOF-SIMS measurements. References [1] Ghani T, Armstrong M, Auth C, et al. A 90-nm high volume manufacturing logic technology featuring novel 45-nm gate length strained silicon CMOS transistors. In: IEDM Tech Dig; 2003. p. 978–80. [2] Nouri F, Verheyen P, et al. A systematic study of trade-offs in engineering a locally strained pMOSFET. In: IEDM Tech Dig, vol. 107; 2004. p. 1055–8. [3] Hartmann JM, Gonzatti F, Barnes JP, Fillot F, Billon T. Growth kinetics and Bdoping of very high G content Si1 xGex for source and drain engineering. ECS Trans 2007;6(1):397–400. [4] Tong Q-Y, Scholz R, Gösele U, Lee T-H, Huang L-J, Chao Y-L, et al. A smarter-cut approach to low temperature silicon layer transfer. Appl Phys Lett 1998;72:49. [5] Höchbauer T, Walter KC, Schwarz RB, Nastasi M, Bower RW, Ensinger W. The influence of boron ion implantation on hydrogen blister formation in n-type silicon. J Appl Phys 1999;86:4176. [6] Marwick AD, Oehrlein GS, Wittmer M. High hydrogen concentrations produced by segregation into p+ layers in silicon. Appl Phys Lett 1991;59(2):198. [7] Cottrell TL. The strengths of chemical bonds. second ed. London: Butterworths; 1958.