Package on package

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Package on package (PoP) is an integrated circuit packaging method to combine vertically discrete logic and memory ball grid array (BGA) packages. Two or more packages are installed atop each other, i.e. stacked, with a standard interface to route signals between them. This allows higher component density in devices, such as mobile phones, personal digital assistants (PDA), and digital cameras.

Integrated circuit packaging Final stage of semiconductor device fabrication

In electronics manufacturing, integrated circuit packaging is the final stage of semiconductor device fabrication, in which the block of semiconductor material is encapsulated in a supporting case that prevents physical damage and corrosion. The case, known as a "package", supports the electrical contacts which connect the device to a circuit board.

Ball grid array

A ball grid array (BGA) is a type of surface-mount packaging used for integrated circuits. BGA packages are used to permanently mount devices such as microprocessors. A BGA can provide more interconnection pins than can be put on a dual in-line or flat package. The whole bottom surface of the device can be used, instead of just the perimeter. The traces connecting the package's leads to the wires or balls which connect the die to package are also on average shorter than with a perimeter-only type, leading to better performance at high speeds.

Mobile phone Portable device to make telephone calls using a radio link

A mobile phone, cell phone, cellphone, or hand phone, sometimes shortened to simply mobile, cell or just phone, is a portable telephone that can make and receive calls over a radio frequency link while the user is moving within a telephone service area. The radio frequency link establishes a connection to the switching systems of a mobile phone operator, which provides access to the public switched telephone network (PSTN). Modern mobile telephone services use a cellular network architecture, and, therefore, mobile telephones are called cellular telephones or cell phones, in North America. In addition to telephony, 2000s-era mobile phones support a variety of other services, such as text messaging, MMS, email, Internet access, short-range wireless communications, business applications, video games, and digital photography. Mobile phones offering only those capabilities are known as feature phones; mobile phones which offer greatly advanced computing capabilities are referred to as smartphones.

Contents

Configuration

Two widely used configurations exist for PoP:

System on a chip type of integrated circuit

A system on a chip or system on chip is an integrated circuit that integrates all components of a computer or other electronic system. These components typically include a central processing unit (CPU), memory, input/output ports and secondary storage – all on a single substrate or microchip, the size of a coin. It may contain digital, analog, mixed-signal, and often radio frequency signal processing functions, depending on the application. As they are integrated on a single substrate, SoCs consume much less power and take up much less area than multi-chip designs with equivalent functionality. Because of this, SoCs are very common in the mobile computing and edge computing markets. Systems on chip are commonly used in embedded systems and the Internet of Things.

Typical logic plus memory PoP stack, common to mobile phone SoCs or baseband modems from 2005 onward ASIC + Memory PoP Schematic.JPG
Typical logic plus memory PoP stack, common to mobile phone SoCs or baseband modems from 2005 onward

During PCB assembly, the bottom package of a PoP stack is placed directly on the PCB, and the other package(s) of the stack are stacked on top. The packages of a PoP stack become attached to each other (and to the PCB) during reflow soldering.

Reflow soldering

Reflow soldering is a process in which a solder paste is used to temporarily attach one or thousands of tiny electrical components to their contact pads, after which the entire assembly is subjected to controlled heat. The solder paste reflows in a molten state, creating permanent solder joints. Heating may be accomplished by passing the assembly through a reflow oven or under an infrared lamp or by soldering individual joints [unconventionally] with a desoldering hot air pencil.

Benefits

The package on package technique tries to combine the benefits of traditional packaging with the benefits of die-stacking techniques, while avoiding their drawbacks.

In microelectronics, a three-dimensional integrated circuit is an integrated circuit (IC) manufactured by stacking silicon wafers or dies and interconnecting them vertically using, for instance, through-silicon vias (TSVs) or Cu-Cu connections, so that they behave as a single device to achieve performance improvements at reduced power and smaller footprint than conventional two dimensional processes. 3D IC is just one of a host of 3D integration schemes that exploit the z-direction to achieve electrical performance benefits.

Traditional packaging places each die in its own package, a package designed for normal PCB assembly techniques that place each package directly on the PCB side-by-side. The 3D die-stacking system in package (SiP) techniques stacks multiple die in a single package, which has several advantages and also some disadvantages compared to traditional PCB assembly.

A system in package (SiP) or system-in-a-package is a number of integrated circuits enclosed in a single chip carrier package. The SiP performs all or most of the functions of an electronic system, and is typically used inside a mobile phone, digital music player, etc. Dies containing integrated circuits may be stacked vertically on a substrate. They are internally connected by fine wires that are bonded to the package. Alternatively, with a flip chip technology, solder bumps are used to join stacked chips together. Systems-in-package are like systems-on-chip (SoC) but less tightly integrated and not on a single semiconductor die.

In embedded PoP techniques, chips are embedded in a substrate on the bottom of the package. This PoP technology enables smaller packages with shorter electrical connections and is supported by companies such as Advanced Semiconductor Engineering (ASE). [1]

Advantages over traditional isolated-chip packaging

The most obvious benefit is motherboard space savings. PoP uses much less PCB area, almost as little as stacked-die packages.

Electrically, PoP offers benefits by minimizing track length between different interoperating parts, such as a controller and memory. This yields better electrical performance of devices, since shorter routing of interconnections between circuits yields faster signal propagation and reduced noise and cross-talk.

Advantages over chip stacking

There are several key differences between stacked-die and stacked-package products.

The main financial benefit of package on package is that the memory device is decoupled from the logic device. Therefore this gives PoP all the same advantages that traditional packaging has over stacked-die products:

JEDEC standardization

Other names

Package on package is also known by other names:

History

In 2001, a Toshiba research team including T. Imoto, M. Matsui and C. Takubo developed a "System Block Module" wafer bonding process for manufacturing 3D integrated circuit (3D IC) packages. [4] [5] The earliest known commercial use of a 3D package-on-package chip was in Sony's PlayStation Portable (PSP) handheld game console, released in 2004. The PSP hardware includes eDRAM (embedded DRAM) memory manufactured by Toshiba in a 3D package chip with two dies stacked vertically. [6] Toshiba called it "semi-embedded DRAM" at the time, before later calling it a stacked "chip-on-chip" (CoC) solution. [6] [7]

In April 2007, Toshiba commercialized an eight-layer 3D chip package, the 16  GB THGAM embedded NAND flash memory chip, which was manufactured with eight stacked 2 GB NAND flash chips. [8] The same month, U.S. Patent 7,923,830 ("Package-on-package secure module having anti-tamper mesh in the substrate of the upper package") was filed by Steven M. Pope and Ruben C. Zeta of Maxim Integrated. [9] In September 2007, Hynix Semiconductor introduced 24-layer 3D packaging technology, with a 16 GB flash memory chip that was manufactured with 24 stacked NAND flash chips using a wafer bonding process. [10]

Related Research Articles

Computer memory physical device used to store information for immediate use in a digital electronic device

In computing, memory refers to the computer hardware integrated circuits that store information for immediate use in a computer; it is synonymous with the term "primary storage". Computer memory operates at a high speed, for example random-access memory (RAM), as a distinction from storage that provides slow-to-access information but offers higher capacities. If needed, contents of the computer memory can be transferred to secondary storage; a very common way of doing this is through a memory management technique called "virtual memory". An archaic synonym for memory is store.

Moores law heuristic law stating that the number of transistors on a circuit doubles every two years

Moore's law is the observation that the number of transistors in a dense integrated circuit doubles about every two years. The observation is named after Gordon Moore, the co-founder of Fairchild Semiconductor and CEO of Intel, whose 1965 paper described a doubling every year in the number of components per integrated circuit, and projected this rate of growth would continue for at least another decade. In 1975, looking forward to the next decade, he revised the forecast to doubling every two years, a compound annual growth rate (CAGR) of 41.4%.

Flash memory Electronic non-volatile computer storage device

Flash memory is an electronic (solid-state) non-volatile computer storage medium that can be electrically erased and reprogrammed.

Programmer (hardware) device that configures programmable non-volatile integrated circuits

A programmer (hardware), device programmer, chip programmer, device burner, or PROM writer is a piece of electronic equipment that arrange written software to configure programmable non-volatile integrated circuits, called programmable devices. The target devices include; PROM, EPROM, EEPROM, Flash memory, eMMC, MRAM, FeRAM, NVRAM, PLD, PLA, PAL, GAL, CPLD, FPGA, and MCU. These are terminologies in the field of computer hardware.

Multi-chip module

A multi-chip module (MCM) is generically an electronic assembly where multiple integrated circuits, semiconductor dies and/or other discrete components are integrated, usually onto a unifying substrate, so that in use it can be treated as if it were a larger IC. Other terms, such as "hybrid" or "hybrid integrated circuit", also refer to MCMs. The individual ICs that make up an MCM are known as Chiplets. Intel and AMD are using MCMs to improve performance and reduce costs, as splitting a large IC into smaller ICs allows for more ICs per wafer, and improved yield.

Transistor count the number of transistors in a device

The transistor count is the number of transistors on an integrated circuit (IC). Transistor count is the most common measure of IC complexity, although there are caveats. For instance, the majority of transistors are contained in the cache memories in modern microprocessors, which consist mostly of the same memory cell circuits replicated many times. The rate at which transistor counts have increased generally follows Moore's law, which observed that the transistor count doubles approximately every two years. All microprocessor, graphics processing unit (GPU) and field-programmable gate array (FPGA) devices listed below are fabricated with MOSFET technology.

Charge trap flash (CTF) is a semiconductor memory technology used in creating non-volatile NOR and NAND flash memory. The technology differs from the more conventional floating-gate MOSFET technology in that it uses a silicon nitride film to store electrons rather than the doped polycrystalline silicon typical of a floating gate structure. This approach allows memory manufacturers to reduce manufacturing costs five ways:

  1. Fewer process steps are required to form a charge storage node
  2. Smaller process geometries can be used
  3. Multiple bits can be stored on a single flash memory cell.
  4. Improved reliability
  5. Higher yield since the charge trap is less susceptible to point defects in the tunnel oxide layer

SONOS, short for "silicon–oxide–nitride–oxide–silicon", more precisely, "polycrystalline silicon"—"silicon dioxide"—"silicon nitride"—"siicon dioxide"—"silicon", is a cross sectional structure of MOSFET, realized by P.C.Y. Chen in 1977. This structure is often used for non-volatile memories, such as EEPROM and flash memories. It is sometimes used for TFT LCD displays. It is one of CTF (charge trap flash) variants. It is distinguished from traditional non-volatile memory structures by the use of silicon nitride (Si3N4 or Si9N10) instead of "polysilicon-based FG (floating-gate)" for the charge storage material. A further variant is "SHINOS" ("silicon"—"hi-k"—"nitride"—"oxide"—"silicon"), which is substituted top oxide layer with high-κ material. Another advanced variant is "MONOS" ("metal–oxide–nitride–oxide–silicon"). Companies offering SONOS-based products include Cypress Semiconductor, Macronix, Toshiba, United Microelectronics Corporation and Floadia.

Open NAND Flash Interface Working Group Association of electronic companies of NAND flash interface technologies sector

The Open NAND Flash Interface Working Group, is a consortium of technology companies working to develop open standards for NAND flash memory and devices that communicate with them. The formation of ONFI was announced at the Intel Developer Forum in March 2006.

In electronics, a multi-level cell (MLC) is a memory element capable of storing more than a single bit of information, compared to a single-level cell (SLC) which can store only one bit per memory element.

Through-silicon via

In electronic engineering, a through-silicon via (TSV) or through-chip via is a vertical electrical connection (via) that passes completely through a silicon wafer or die. TSVs are high performance interconnect techniques used as an alternative to wire-bond and flip chips to create 3D packages and 3D integrated circuits. Compared to alternatives such as package-on-package, the interconnect and device density is substantially higher, and the length of the connections becomes shorter.

Fujio Masuoka is a Japanese engineer, who has worked for Toshiba and Tohoku University, and is currently chief technical officer (CTO) of Unisantis Electronics. He is best known as the inventor of flash memory, including the development of both the NOR flash and NAND flash types in the 1980s. He also invented the first gate-all-around (GAA) MOSFET (GAAFET) transistor, an early non-planar 3D transistor, in 1988.

Crossbar is a company based in Santa Clara, California. Crossbar develops a class of non-volatile resistive random-access memory (RRAM) technology. The company in 2013 announced its goal was a terabyte of storage on a single integrated circuit, compatible with standard CMOS semiconductor manufacturing processes.

The memory cell is the fundamental building block of computer memory. The memory cell is an electronic circuit that stores one bit of binary information and it must be set to store a logic 1 and reset to store a logic 0. Its value is maintained/stored until it is changed by the set/reset process. The value in the memory cell can be accessed by reading it.

High Bandwidth Memory high-performance RAM interface for 3D-stacked DRAM from AMD and Hynix

High Bandwidth Memory (HBM) is a high-performance RAM interface for 3D-stacked SDRAM from Samsung, AMD and SK Hynix. It is to be used in conjunction with high-performance graphics accelerators and network devices. The first HBM memory chip was produced by SK Hynix in 2013, and the first devices to use HBM were the AMD Fiji GPUs in 2015.

References

  1. LaPedus, Mark (2014-06-19). "Mobile Packaging Market Heats Up". Semiconductor Engineering. Retrieved 2016-04-28.
  2. Thomas, Glen. "Package-on-Package Flux". Indium Corporation. Retrieved 2015-07-30.
  3. Amkor Technology. "Package on Package (PoP | PSfvBGA | PSfcCSP | TMV® PoP)" . Retrieved 2015-07-30.
  4. Garrou, Philip (6 August 2008). "Introduction to 3D Integration". Handbook of 3D Integration: Technology and Applications of 3D Integrated Circuits (PDF). Wiley-VCH. p. 4. doi:10.1002/9783527623051.ch1. ISBN   9783527623051.
  5. Imoto, T.; Matsui, M.; Takubo, C.; Akejima, S.; Kariya, T.; Nishikawa, T.; Enomoto, R. (2001). "Development of 3-Dimensional Module Package, "System Block Module"". Electronic components and technology conference. Institute of Electrical and Electronics Engineers (51): 552–7.
  6. 1 2 James, Dick (2014). "3D ICs in the real world". 25th Annual SEMI Advanced Semiconductor Manufacturing Conference (ASMC 2014): 113–119. doi:10.1109/ASMC.2014.6846988.
  7. "System-in-Package (SiP)". Toshiba . Retrieved 3 April 2010.
  8. "TOSHIBA COMMERCIALIZES INDUSTRY'S HIGHEST CAPACITY EMBEDDED NAND FLASH MEMORY FOR MOBILE CONSUMER PRODUCTS". Toshiba . April 17, 2007. Retrieved 23 November 2010.
  9. "United States Patent US 7,923,830 B2" (PDF). 2011-04-12. Retrieved 2015-07-30.
  10. "Hynix Surprises NAND Chip Industry". Korea Times . 5 September 2007. Retrieved 8 July 2019.

Further reading