1 1 MM and MTM for Mobility One main purpose of this chapter is to introduce the hardware technology that delivers mobility. Before introducing the hardware technology, however, it is important to elaborate on the content and extent of mobility. Of course, mobility is not possible without communication networks, wired or the otherwise. Here we review the convergence of communications (wired with wireless, switched circuits with packeted circuits, voice with data, GERAN with UTRAN, wireless WAN with wireless LAN) first. The convergence of communications begins with a consolidation of circuit‐ and packet‐switched networks at low‐level physical layers (wired networks, including cop- per twisted pairs and optical fiber cables), then air interfaces with the wireless‐WAN (commonly known as 2G, 3G, and 4G) and wireless‐LAN (commony known as wifi). The tasks are done through 3GPP releases up to Rel 7 for 3G. Currently, 5G is under development, thus, 5G goals and key technologies to achieve the goals are discussed. Since mobility is actually achieved by combination of wired and wireless networks, we then review the key products employed in both networks. We found the communica- tion products encompass different industries; for example, optical fiber industry where silica glass is the main material used for optical links, cabling industry where copper and plastics are heavily used to form connectors and cables, and semiconductor and PCB (printed circuit board) industries where silicon and organic materials are employed for devices and components miniaturization. After reviewing the products employed in wired and wireless networks, it is time to take a look at hardware fabrication and integration technologies, from which commu- nication products are constructed. In this chapter, we discuss state‐of‐the‐art MM (more Moore approach) and MTM (more than Moore approach) processes. Both are planar processing technologies, and suitable for mass production, with MM employing semiconductors COPYRIGHTEDand MTM PCB (LTCC, too). MM MATERIAL takes place in wafer foundries and MTM in OSAT (outsourced semiconductor assembly and test) sites. MM and MTM are traditionally known as IC fabrication and packaging specialities. In Section 1.3, we review briefly the state of the art MM and MTM hardware tech- nologies in realizing transistors and a combo consisting of A‐series AP and its mobile memory, the most critical device and component in handheld mobiles. Transistor engineering is the most important achievement in MM in recent years, which can be represented by HKMG (high‐k metal gate) and TriGate developments. Figure 1.1 below shows device construction with HKMG. The combination of the high‐k 3D IC and RF SiPs: Advanced Stacking and Planar Solutions for 5G Mobility, First Edition. Lih-Tyng Hwang and Tzyy-Sheng Jason Horng. © 2018 John Wiley & Sons Singapore Pte. Ltd. Published 2018 by John Wiley & Sons Singapore Pte. Ltd. Companion website: www.wiley.com/go/hwangic 0003388903.INDD 1 3/12/2018 6:47:52 PM 2 3D IC and RF SiPs: Advanced Stacking and Planar Solutions for 5G Mobility High-k Metal gate Figure 1.1 HKMG, three sides are high‐k dielectric, and the gate is metalized at the top surface. D S Oxide Silicon TriGate Figure 1.2 A FinFET constructing from multiple TriGates; each ridge in a TriGate is covered on D three sides. Oxide S Silicon material (the darker layer) and metal gate gives the transistor much better performance (reduced leakage and enhanced transistor stability, respectively) than would be possible with a traditional silicon dioxide (dielectric) and polysilicon (non‐metal) gate. Figure 1.2 shows a 3D FinFET transistor constructed with multiple TriGates (triple- gates). It is named because each ridge in a TriGate is covered on three sides. The tech- nology, along with Intel’s gate last approach, extended Moore’s Law into 32 nm (technology node) and below; therefore, is considered an important MM contribution. In September of each year, the world, especially the electronics industry and business, are all watching the birth of a new iPhone, in which A‐series AP and its main mobile memory LPDDR are focused. It is because A‐series AP and its mobile memory are the heart, literally, of many Apple iPhones, and mass production of them (the A‐series AP device or the PoP combo of AP and the LPDDR memory) represents a yearly crowning achievement. A‐series AP (A4, A5, …) and its mobile memory, LPDDR, are packaged in an advanced package, the so‐called “PoP (packaged on a package),” shown in Figure 1.3. Note that the dual‐die memory in Figure 1.3 is not symmetrically placed with respect to the AP below. Wirebonding may be one of the factors. The dual‐LPDDR set is on the top, whereas the application processor is on the bottom. The configuration may enhance greatly the pro- cessor’s performance; however, heat dissipation by the AP is a concern. In later AP(A7)/ LPDDR3 PoP for iPhone 5S, there are three rows of TMVs (through molding vias, see Figures 3.24 and 3.25 in Chapter 3), whereas there are only two rows, as shown in Figure 1.3. The added row may be designed to assist heat removal. 0003388903.INDD 2 3/12/2018 6:47:53 PM MM and MTM for Mobility 3 Figure 1.3 A cross‐sectional view of AP(A4)/LPDDR combo in PoP for iPhone 4. Two rows of TMVs are conspicuous on each side. Source: Image courtesy of Chipworks Inc. A9 employs 14 nm and/or 16 nm, depending on the manufacturer Samsumg (14 nm) or TSMC (16 nm). Various sources have indicated A10, used by iPhone 7 and available in September 2016, may be still fabricated using TSMC’s 16 nm technology; neverthe- less, the most advanced 10 nm technology is likely to be used to produce Qualcom’s AP, Snapdragon 835 by Samsung.[1] Because both MM and MTM hardware are introduced in this chapter, it is important to understand the difference between them. Let’s use the following table to illustrate the differences (Table 1.1). Figures 1.50 and 1.51 (shown later in this chapter) are an important summary to this chapter. Figure 1.50 illustrates the state of the art packages empolyed; x‐axis indicates the level of integration, and y‐axis the level of monolithicity (versus hybrid approach). Figure 1.51 illustrates the business division between MM and MTM. MTM hardware technology will be important in meeting the demands of the future 5G mobility. The topic is discussed briefly at the end of the chapter; but, in Chapter 9 more details on future hardware technologies for 5G mobility are offered. Table 1.1 MM and MTM comparison. MM (Wafer foundry) MTM (OSAT) Processing Photo‐lithography, ion Molding, underfill, screen printing, electrolytic techniques implantation, CVD, sputtering, plating, electro‐less plating, wirebonding, etching flip‐chip bumping, reflow, SMT Substrates Silicon and GaAs (III‐V) MLO, MLC, Hi‐res silicon and glass Metallization W, Al, and Cu in Si; Au in III‐V Ti, Cr, W, Ni, Pd, Cu, Pb, Sn, Ag, etc.. 1.1 ­Convergence in Communications and the Future, 5G Here, we discuss the convergence of communications, which occurred during the development of 3G around 2000 to 2003, followed by later refinements (termed 3.5G, 3.9G, and B4G). Lastly, future wireless communications, 5G, for example, as well as its goals and the technologies needed to achieve the goals, will be discussed. 1.1.1 From 1980 (1G) to 2010 (4G) In the 1980s, the first cellular phones by Motorola were all analog ones. These analog phones used the AMPS (advanced mobile phone system) cellular system developed by 0003388903.INDD 3 3/12/2018 6:47:53 PM 4 3D IC and RF SiPs: Advanced Stacking and Planar Solutions for 5G Mobility AT&T; they consumed more power, had shorter utility hours, and thus, they could not compete with the later digital GSM phones developed by the European community, represented by Nokia. The GSM phones, being digital, consumed less power, and quickly dominated the market. Motorola had to alter their courses of phone develop- ment, and thus ditched analog phones, and soon after adopted GSM and UMTS stand- ards, later termed 2G and 3G, respectively. Motorola’s analog phones are considered as 1G, retrospectively. Key features of 1G include 1) being analog in nature, 2) having a bandwidth (BW) of 30 kHz; note that human voices have a highest pitch of 20 KHz; and 3) carrying voice only. The 2G devel- opment span lasted over the entire 1990s: first it added GPRS (2.5G) and then EDGE (2.75G) capability along the way. 2G is digital in nature, and it carries voice and data (e.g., short message service, SMS). It had a BW of 200 kHz (124 channels share 25 MHz); for example, GSM900 (band 8) downlink band is between 935 MHz and 960 MHz. The original 2G carries only voices over the circuit‐switched (CS) networks (e.g., PSTN and POTS). GPRS added packet capability, extending the circuit switched only 2G to 2.5G, which includes packet switched (PS) networks (e.g., ethernet). 2.5G had a digital data rate of 144 kbps. IMT‐2000 under ITU‐R began in 1999. It set out to integrate GSM and UTRA (UMTS terrestrial radio access) into one global standard, UMTS (Universal Mobile Telecommunications System). The tasks were accomplished by 3GPP (the Third Generation Partnership Project) in releases: Rel 99 and Rels 4, 5, 6, and 7 roughly cor- respond to the calendar years (e.g., Release 4 in 2004). Thus, Rel 99 on W‐CDMA (wideband CDMA, which employs 5 MHz bandwidth), development Release 4 on TDD, Release 5 on HSDPA, Release 6 on HSUPA, and Release 7 on HSPA+.