# Patent

## Title
Memory bandwidth aggregation using simultaneous access of stacked semiconductor memory die

## Abstract

A packaged semiconductor device includes a data pin, a first memory die, and a second memory die stacked with the first memory die. The first memory die includes a first data interface coupled to the data pin and a first memory core having a plurality of banks. The second memory die includes a second memory core having a plurality of banks. A respective bank of the first memory core and a respective bank of the second memory core perform parallel row access operations in response to a first command signal and parallel column access operations in response to a second command signal. The first data interface of the first die provides aggregated data from the parallel column access operations in the first and second die to the data pin.

## Background
RELATED APPLICATIONS
This application claims the benefit of priority under 35 U.S.C. 119(e) to Provisional Application Ser. No. 61/655,950, filed Jun. 5, 2012, entitled MEMORY BANDWIDTH AGGREGATION USING SIMULTANEOUS ACCESS OF STACKED SEMICONDUCTOR MEMORY DIE, which is incorporated herein by reference in its entirety for all purposes.


TECHNICAL FIELD
The present embodiments relate generally to semiconductor memories, and specifically to semiconductor memory die arranged in a stacked configuration in a package.
BACKGROUND
Semiconductor die can be stacked in a package and coupled using through-die vias (e.g., through-silicon vias). For example, semiconductor memory die can be stacked to increase the amount of memory provided by a packaged semiconductor memory device. However, using through-die vias in die stacks presents significant engineering challenges. For example, through-die vias consume die area; their use thus increases die size.
Accordingly, there is a need for efficient schemes for using through-die vias to couple stacked memory die.



BRIEF DESCRIPTION OF THE DRAWINGS
The present embodiments are illustrated by way of example and are not intended to be limited by the figures of the accompanying drawings.
FIGS. 1A-1C are schematic cross-sectional views of packaged semiconductor memory devices with stacked memory die in accordance with some embodiments.
FIGS. 2A-2B are schematic block diagrams of a master memory die stacked with a slave memory die in accordance with some embodiments.
FIG. 3A is a timing diagram illustrating timing of read operations for two stacked memory die in accordance with some embodiments.
FIG. 3B is a timing diagram illustrating aggregation of data accessed from and serialized by a master die and a slave die in parallel in accordance with some embodiments.
FIGS. 4A and 4B are schematic diagrams showing circuitry in a read path of two stacked memory die in accordance with some embodiments.
FIGS. 5A and 5B are schematic diagrams showing circuitry in a write path of two stacked memory die in accordance with some embodiments.
FIG. 6 is a cross-sectional block diagram of an electronic system that includes a memory controller and a packaged semiconductor memory device with stacked memory die in accordance with some embodiments.
FIG. 7A is a flow diagram illustrating a method of operating a packaged semiconductor memory device in which data is read from the device, in accordance with some embodiments.
FIG. 7B is a flow diagram illustrating a method of operating a packaged semiconductor memory device in which data is written to the device, in accordance with some embodiments.



Like reference numerals refer to corresponding parts throughout the drawings and specification.
DETAILED DESCRIPTION
Embodiments are disclosed in which data accessed from multiple memory die arranged in a stacked configuration is aggregated.
In some embodiments, a packaged semiconductor memory device includes a data pin, a first memory die, and a second memory die. The first memory die includes a first data interface coupled to the data pin and a first memory core having a plurality of banks. The second memory die is stacked with the first memory die and includes a second memory core having a plurality of banks. A respective bank of the first memory core and a respective bank of the second memory core are configured to perform memory access operations in parallel, and the first data interface is configured to provide aggregated data from the parallel memory access operations. For example, the respective banks of the first and second memory cores are configured to perform parallel row access operations in response to a first command signal and parallel column access operations in response to a second command signal. The first data interface is configured to provide aggregated data from the parallel column access operations to the data pin.
In some embodiments, a method of operating a packaged semiconductor memory device is performed for a packaged semiconductor memory device that includes a data pin, a first memory die having a first memory core, and a second memory die stacked with the first memory die and having a second memory core. The method includes performing memory access operations in parallel in a bank of the first memory core and a bank of the second memory core, aggregating data from the parallel memory access operations, and transmitting the aggregated data from the data pin. For example, the method includes performing parallel row access operations in the bank of the first memory core and the bank of the second memory core, performing parallel column access operations in the bank of the first memory core and the bank of the second memory core, aggregating data from the parallel column access operations, and transmitting the aggregated data from the data pin.
In some embodiments, an electronic system includes a semiconductor memory controller and a packaged semiconductor memory device. The packaged semiconductor memory device includes a first memory die and a second memory die stacked with the second memory die. The first and second memory die include respective first and second memory cores, each having a plurality of banks. A respective bank of the first memory core and a respective bank of the second memory core are configured to perform memory access operations in parallel. The first memory die further includes a data interface configured to transmit aggregated data from the parallel column access operations to the memory controller. For example, the respective banks of the first and second memory cores are configured to perform row access operations in response to a first command signal and parallel column access operations in response to a second command signal, and the data interface of the first memory die is configured to transmit aggregated data from the parallel column access operations to the memory controller.
Reference will now be made in detail to various embodiments, examples of which are illustrated in the accompanying drawings. In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the disclosure. However, some embodiments may be practiced without these specific details. In other instances, well-known methods, procedures, components, and circuits have not been described in detail so as not to unnecessarily obscure aspects of the embodiments.
FIG. 1A is a schematic cross-sectional view of a packaged semiconductor memory device 100 in accordance with some embodiments. In the device 100, two memory die 104a and 104b are stacked on top of a package substrate 102 (e.g., a printed circuit board). In some embodiments, the memory die 104a and 104b are dynamic random-access memory (DRAM) die. The memory die 104a and 104b include through-die vias 112 that couple circuitry in the die 104a to corresponding circuitry in the die 104b. When the die 104a and 104b are silicon-based, the through-die vias 112 are referred to as through-silicon vias (TSVs). The die 104a and 104b are connected by interconnects 114 (e.g., metallic bumps) that connect corresponding through-die vias 112 on the die 104a and 104b. Circuitry on the die 104a thus may transmit signals to corresponding circuitry on the die 104b through a through-die via 112 on the die 104a, an interconnect 114, and a corresponding through-die via 112 on the die 104b. Circuitry on the die 104b may transmit signals to circuitry on the die 104a in a similar manner.
In some embodiments, the bottom die 104a is coupled to the package substrate 102 (e.g., in a flip-chip configuration) by interconnects (e.g., metallic bumps) 110. Attached to the package substrate 102 are pins 106, including signal pins for receiving and transmitting signals as well as power and ground pins. (The term pin as used herein includes pins, balls, lands, bumps, micro-bumps, and any other contacts suitable for electrically connecting the packaged device 100 to a circuit board or other underlying substrate). Examples of signal pins 106 include data pins for transmitting and/or receiving data, data strobe pins for transmitting and/or receiving data strobe signals, command-and-address (C/A) pins for receiving commands and associated memory addresses, and clock pins for receiving clock signals. A respective data pin may be bi-directional or uni-directional.
A respective signal pin 106 is coupled to a respective interconnect 110, and thus to the bottom die 104a, by traces and vias 108 in the package substrate 102. The respective signal pin 106 may further be coupled to the top die 104b by through-die vias 112 and an interconnect 114.
In some embodiments, the bottom die in a stack also may be electrically coupled to the substrate using bond wires. FIG. 1B is a schematic cross-sectional view of a packaged semiconductor memory device 130 in which two memory die 134a and 134b are stacked on a package substrate 132. The bottom die 134a is electrically coupled to the substrate 132 by bond wires 136 that couple respective bond pads on the bottom die 134a to corresponding lands on the substrate 132; these corresponding lands are coupled in turn to respective pins 106 (e.g., by respective traces and vias 138 in the substrate 132). The top die 134b and bottom die 134a are coupled by through-die vias 112 and interconnects 114, as described for FIG. 1A.
FIGS. 1A and 1B illustrate examples of packaged semiconductor devices 100 and 130 with two stacked die. In some embodiments, three or more die may be stacked in a package. FIG. 1C is a schematic cross-sectional view of a packaged semiconductor memory device 150 with four stacked die 154a-d in accordance with some embodiments. The four stacked die 154a-d are stacked on a package substrate 152. The four die 154a-d are connected by interconnects 114 (e.g., metallic bumps) that connect corresponding through-die vias 112 on the die 154a-d. Circuitry on a respective one of the die 154a-d thus may transmit signals to corresponding circuitry on the other three die through through-die vias 112 and corresponding interconnects 114.
In the example of FIG. 1C, the bottom die 154a is coupled to the package substrate 152 by interconnects 110, as described for the device 100 (FIG. 1A). In other examples, the bottom die may also or alternatively be coupled to the substrate 152 by bond wires (e.g., as shown for the device 130, FIG. 1B). The upper die 154b-d are electrically coupled to the substrate 152 by through-die vias 112, interconnects 114, and interconnects 110.
In some embodiments, one of the memory die in a stacked die configuration (e.g., in the device 100, 130, or 150, FIGS. 1A-1C) is configured as a master die and the remaining memory die in the stack is/are configured as slave die. For example, the bottom die 104a, 134a, or 154a (FIGS. 1A-1C) is configured as the master die, and the other die is/are configured as a slave or slaves. (Alternatively, a die with another position in the stack is configured to be the master die.) Memory access instructions are provided to the master die; in response, memory access operations are performed in parallel in both the master and slave die. For example, a bank in the memory core of each die is selected and memory access operations are performed in the selected banks. Accessed data from the slave die are provided to the master die, which aggregates (e.g., interleaves) the accessed data with its own accessed data. In some embodiments, each slave die serializes its accessed data and provides the serialized data to the master die. The master die serializes its own accessed data and aggregates the master and slave serialized data into a single serialized data stream.
FIG. 2A is a schematic block diagram of a master memory die 200a stacked with a slave memory die 200b in a package in accordance with some embodiments. The memory die 200a and 200b are DRAM die in this example. In some embodiments, the memory die 200a and 200b are examples of the die 104a and 104b (FIG. 1A) or 134a and 134b (FIG. 1B).
The master die 200a includes a DRAM core 202a with a plurality of memory banks 204a-1 through 204a-n, where n is an integer greater than one. Each bank 204a includes an array of memory cells arranged in rows and columns. The master die 200a also includes an interface 210a that functions as a data interface to receive and transmit data, a command-and-address (C/A) interface to receive commands (e.g., memory access commands, such as row access commands and column access commands) and their associated addresses, and a clock (CK) interface to receive an external clock signal. In some embodiments, the interface 210a generates an internal clock signal based on the external clock signal (e.g., using a delay-locked loop (DLL) or phase-locked loop (PLL)). The interface 210a thus is coupled to one or more data pins, one or more C/A pins, and a clock pin. In some embodiments, the interface 210a is also coupled to a data strobe (DQS) pin.
Coupled between the interface 210a and the DRAM core 202a is a data path 206a. For write operations, the interface 210a receives serialized write data; the data path 206a deserializes a portion of the write data and provides the deserialized portion to the core 202a. For read operations, the data path 206a serializes read data fetched from the core 202a and provides the serialized read data to the interface 210a. Also coupled between the interface 210a and the core 202a is C/A decode circuitry 208a, also referred to as C/A decoder 208a, which decodes C/A signals from the interface 210a and provides the decoded C/A commands and associated addresses to the core 202a. 
The master memory die 200a also includes a configuration register 212a. The memory die 200a can be configured as the master die by storing a corresponding value in the configuration register 212a (e.g., in response to a command provided to the interface 210a). The configuration register 212a is coupled to the interface 210a and C/A decoder 208a and provides an enable signal that activates both circuits when it stores the value indicating that the die 200a is the master die.
The slave memory die 200b similarly includes a DRAM core 202b with banks 204b-1 through 204b-n, interface 210b, data path 206b, C/A decoder 208b, and configuration register 212b, all situated as described for the corresponding elements of the master memory die 200a. The die 200b is configured as the slave die by storing a corresponding value in the configuration register 212b. When the configuration register 212b stores this value, it de-asserts the enable signal for the decoder 208b and interface 210b and thus turns off the decoder 208b and interface 210b (as indicated by the cross-hatch patterns of the decoder 208b and interface 210b in FIG. 2A).
The configuration registers 212a and 212b thus allow a given die 200 to be configured as either the master die or a slave die, depending on its position in the stack. Typically, the interface 210 of a single die 200 in a stack is connected to the corresponding data, DQS, C/A, and/or clock pins. (In the example of FIG. 2A, the interface 210a is connected to the data, DQS, C/A, and clock pins.) That die is configured as the master die and the other die are configured as the slave die, by writing appropriate values to the configuration registers 212.
The master die 200a and slave die 200b are coupled by a plurality of through-die vias (e.g., TSVs). A through-die via 214 is coupled between outputs of the C/A decoders 208a and 208b. The through-die via 214 provides decoded C/A commands from the C/A decoder 208a of the master die 200a to the core 202b of the slave die 200b. The C/A decoder 208a thus is coupled to the cores 202a and 202b of both die 200a and 200b. Another through-die via 218 is coupled between the read outputs of the data paths 206a and 206b and provides read data from the read output of the data path 206b to the read input of the interface 210a. Still another through-die via 216 is coupled to clock outputs of interfaces 210a and 210b and coupled between data paths 206a and 206b. The through-die via 216 provides a clock signal from the interface 210a to the data path 206b. Additional through-die vias 220 and 222 are coupled between write outputs of the interfaces 210a and 210b, and thus also between write inputs of the data paths 206a and 206b, and provide write data and an associated write data strobe signal (DQS) from the interface 210a to the data path 206b. Each of the through-die vias 214, 216, 218, 220, and 222 as shown schematically in FIG. 2A corresponds physically to a through-die via 112 (FIGS. 1A-1B) in each of the two die 200a and 200b, as connected by an interconnect 114 (FIGS. 1A-1B).
FIG. 3A is a timing diagram illustrating timing of read operations for the stacked die 200a and 200b in accordance with some embodiments. FIG. 3A shows a clock signal (CK) 302, command signals 304, and data signals at various locations in the die 200a and 200b during read operations. The interface 210a provides CK 302 to data path 206a and also to data path 206b using through-die via 216.
To read data from the cores 202a and 202b, a row access command signal (ACT) is provided to the C/A input of the interface 210a. The row access command may also be referred to as a page activation command or a bank activation command. No signal is provided to the interface 210b, which is disabled and is not connected to C/A pins. The interface 210a forwards the ACT signal to the C/A decoder 208a, which decodes the command (and its associated row address) and provides control signals corresponding to the decoded command to the core 202a and, by way of through-die via 214, the core 202b. The decoded ACT command specifies a row within a bank of each die 200a and 200b. The specified banks are activated in parallel in cores 202a and 202b during period 306. For example, FIG. 2B illustrates activation of banks 204a-n and 204b-n in parallel (as indicated by the fill pattern) in response to the ACT signal. Specifically, the specified row in each of banks 204a-n and 204b-n is activated. The banks 204a-n and 204b-n thus logically form a single bank spanning the two die 200a and 200b. 
A first column access command signal (RD1) is then provided to the C/A input of the interface 210a. The interface 210a forwards the RD1 signal to the C/A decoder 208a, which decodes the command (and its associated column address) and provides control signals corresponding to the decoded command to the core 202a and, by way of through-die via 214, the core 202b. The decoded RD1 command specifies columns sharing a first column address in the banks 204a-n and 204b-n. In response to the decoded RD1 command, data is fetched from memory cells in the activated row and the specified columns during period 308. Each bank 204a-n and 204b-n thus provides parallel data to its respective data path 206a or 206b in response to RD1: bank 202a-n provides parallel data D1a[3:0] to data path 206a and bank 204b-n provides parallel data D1b[3:0] to data path 206b. In the example of FIG. 3A, the first column address specifies four physical columns in each bank and the parallel data from each bank is four bits wide (i.e., is ×4 or “by four”). Other data widths (e.g., ×2 or ×8) are possible in other examples.
Data path 206a serializes data D1a[3:0] into a sequence of bits D1a[3], D1a[2], D1a[1], and D1a[0]. Data path 206-b serializes data D1b[3:0] into a sequence of bits D1b[3], D1b[2], D1b[1], and D1b[0]. (Other orders are possible). This serialization begins during period 310. The data paths 206a and 206b provide the serialized data to the interface 210a in a manner such that the serialized data from each data path 206a and 206b are aggregated into a serialized stream of bits D1[7:0]. This aggregation begins during period 312. In the example of FIG. 3A, data bits from data paths 206a and 206b are interleaved: D1[7] is D1a[3], D1[6] is D1b[3], and so on. (The order of alternation may be reversed.) Serialized data from the data path 206b is provided to the interface 210a using through-die via 218. The interface 210a outputs the aggregated serialized bits D1[7:0] to a data pin (e.g., a pin 106, FIGS. 1A-1B). In the example of FIG. 3A, D1[7:0] are output at double data rate (DDR): bits are transmitted on both the rising and falling edges of CK 302.
While data for RD1 is being serialized, a second column access command RD2 is provided to the C/A input of the interface 210a. RD2 is processed in the manner described above for RD1. In response, bank 202a-n provides parallel data D2a[3:0] to data path 206a and bank 204b-n provides parallel data D2b[3:0] to data path 206b. Data path 206a serializes data D2a[3:0] into a sequence of bits D2a[3], D2a[2], D2a[1], and D2a[0]. Data path 206-b serializes data D2b[3:0] into a sequence of bits D2b[3], D2b[2], D2b[1], and D2b[0]. The data paths 206a and 206b provide the serialized data to interface 210a in a manner such that the serialized data from each data path 206a and 206b are interleaved, and thus aggregated, into a serialized stream of bits D2[7:0]. Serialized data from the data path 206b is provided to interface 210a using through-die via 218. The interface 210a outputs the aggregated serialized bits D2[7:0] at double data rate. Commands RD1 and RD2 are timed such that interface 210a outputs D2[7:0] immediately after outputting D1[7:0].
Additional column access commands may be provided at specified intervals (e.g., intervals of four CK 302 cycles) to read data in additional groups of columns of the row accessed in response to the ACT command. The timing for these additional column access commands corresponds to the timing shown for RD1 and RD2 in FIG. 3A.
The row access operations and column access operations are performed substantially simultaneously in the die 200a and 200b, since they are performed in parallel. While substantially simultaneous, they may not be precisely simultaneous, due for example to process variations and delays in providing signals from the master die 200a to the slave die 200b. 
FIG. 3B illustrates aggregation of data accessed from and serialized by master die 200a and slave die 200b in parallel in accordance with some embodiments. In response to a column access operation (e.g., RD1 or RD2, FIG. 3A), four bits m1, m2, m3, and m4 are fetched from a bank of the master core 202a and four bits s1, s2, s3, and s4 are fetched in parallel from a corresponding bank of the slave core 202b. These fetches are performed in parallel. The master data path 206a serializes the first four bits into a sequence m1, m2, m3, and m4. The slave data path 206b serializes the second four bits into a sequence s1, s2, s3, and s4. This serialization by the master and slave data paths 206a and 206b is also performed in parallel. For four successive cycles of CK 302, the master data path 206a transmits data 324: a respective bit is transmitted to the interface 210a during a first portion 330 of the cycle and the transmitting output is tristated (i.e., put in a high-impedance or high-Z state) during a second portion 332 of the cycle. The first portion 330 begins on the rising edge of CK 302 and the second portion 332 begins on the falling edge of CK 302. Also during the four successive cycles, the slave data path 206b transmits data 326: a respective bit is transmitted to the interface 210a during the second portion 332 of the cycle and the transmitting output is tristated (i.e., put in a high-impedance or high-Z state) during the first portion 330 of the cycle. (Alternatively, the master data path 206a transmits during the second portion 332 and the slave data path 206b transmits during the first portion 330). The result is a double-date-rate aggregated data stream 328 with alternating bits m1, s1, and so on from the master core 202a and slave core 202b. The interface 210a transmits the aggregated data stream 328 (e.g., to a memory controller 602, FIG. 6) via a data pin.
While FIG. 3B illustrates aggregating data from the master die 200a and slave die 200b by interleaving bits from the respective die, other aggregation techniques are possible. For example, the master data path 206a may provide a burst of multiple (e.g., four) bits to the interface 210a, after which the slave data path 206b provides a corresponding burst of multiple bits to the interface 210a (or vice-versa). Also, when a die stack includes more than two die (e.g., includes four die 154a-d, FIG. 1C), data from each die may be aggregated, for example, by interleaving bits from each die (e.g., in round-robin) or by aggregating bursts of bits from successive die.
FIG. 4A illustrates circuitry in a read path 400 of the memory die 200a and 200b (FIGS. 2A-2B) in accordance with some embodiments. The data paths 206a and 206b include read inputs 402a and 402b that receive parallel data from cores 202a and 202b. Serializers 404a and 404b serialize the data (e.g., data D1a[3:0], D2a[3:0], D1b[3:0], and D2b[3:0], FIG. 3A). Tri-state buffers 406a and 406b transmit serialized bits via outputs 408a and 408b (and, for die 200b, using through-die via 218) to the interface 210a in an alternating manner, as shown for data sequences 324 and 326 (FIG. 3B), such that aggregated data sequence 328 (FIG. 3B) is received at input 410a of the interface 210a. (The sequence 328 is also received at the input 410b of the interface 210b, but the interface 210b is disabled.) The clock (CK) signal is used to enable/disable tri-state buffers 406a and 406b. The clock (CK) signal provided to tri-state buffer 406b (using through-die via 216) is inverted with respect to tri-state buffer 406a, to achieve the interleaved sequence 328.
The interfaces 210a and 210b may include double-data-rate retimers 412a and 412b coupled to buffers 414a and 414b. The double-data-rate retimer 412a receives the aggregated data sequence 328, retimes the sequence 328 using both rising and falling edges of a transmit clock (Tx CK), and provides the retimed sequence 328 to the buffer 414a, which drives the retimed sequence 328 onto an output 416a coupled to a data pin.
In some embodiments, the master die 200a and slave die 200b together include multiple instances of the read path 400, as shown in FIG. 4B. Each instance 400 is coupled to the cores 202a and 202b to receive data fetched from the cores 202a and 202b during column access operations. Each instance 400 is also coupled to a respective data pin (e.g., an output data pin or a bidirectional data pin) and transmits serialized data from column access operations via its respective data pin.
Attention is now directed to performing write operations in the master die 200a and slave die 200b of FIGS. 2A-2B. FIG. 5A illustrates circuitry in a write path 500 of the die 200a and 200b in accordance with some embodiments. Each interface 210a and 210b includes a buffer 506a and 506b. Each data path 206a and 206b includes a flip-flop 512a and 512b coupled to a deserializer 514a and 514b. During write operations, serial write data (e.g., from a memory controller 602, FIG. 6) is provided via a data pin (e.g., a pin 106, FIG. 1A-1B) to a write input 502a of the interface 210a. In some embodiments, the write data is received at a double data rate. The buffer 506a receives the serialized data and drives the serialized data onto a write output 508a of the interface 210a. The write output 508a is coupled to inputs 510a and 510b of the data paths 206a and 206b; these inputs are coupled in turn to flip-flops 512a and 512b. Through-die via 220 couples the write output 508a to the input 510b. 
In some embodiments, a data strobe signal (DQS) accompanies the serialized write data. The interface 210a provides DQS to a through-die via 222 and thereby to the data path 206b as well as to the data path 206a. (The circuitry coupling the interface 210a to the through-die via 222 is not shown in FIG. 5A, for simplicity.) The DQS signal clocks the flip-flops 512a and 512b, with the DQS signal provided to the flip-flop 512b being inverted with respect to the flip-flop 512a. The flip-flop 512a clocks in data on the rising edge of DQS (and thus during a first portion of the cycle of the DQS signal) and the flip-flop 512b clock in data on the falling edge of DQS (and thus during a second portion of the cycle of the DQS signal). The flip-flops 512a and 512b thereby receive bits in an alternating manner (and also disregard bits in an alternating manner), with each one receiving half of the bits of the serial write data. (In other embodiments, a burst of bits is received by the data path 206a, after which a burst of bits is received by the data path 206b, or vice-versa).
The flip-flops 512a and 512b provide their data to deserializers 514a and 514b, each of which deserializes the bits clocked in by its respective flip-flop. The resulting parallel data is provided to the cores 202a and 202b, which write the data into a specified address in a specified bank 204. Data is thus written to a specified one of the banks 204a-1 through 204a-n (FIGS. 2A-2B) and to a specified one of the banks 204b-1 through 204b-n (FIGS. 2A-2B) in parallel.
In some embodiments, the master die 200a and slave die 200b together include multiple instances of the write path 500, as shown in FIG. 5B. Each instance 500 is coupled to the cores 202a and 202b to provide data to cores 202a and 202b during write operations. Each instance 500 is also coupled to a respective data pin (e.g., an input data pin or a bidirectional data pin) and receives serialized data for write operations via its respective data pin.
FIG. 6 is a cross-sectional block diagram of an electronic system 600 in accordance with some embodiments. The system 600 includes a memory controller 602 and the packaged semiconductor memory device 100 (FIG. 1A). Alternatively, the system 600 includes the packaged semiconductor memory device 130 (FIG. 1B) or 150 (FIG. 1C), or another packaged semiconductor device with stacked memory die. While the memory controller 602 is shown as a stand-alone chip, in some embodiments the memory controller 602 is part of a larger integrated circuit (e.g., a processor).
The packaged semiconductor memory device 100 and memory controller 602 are mounted on a printer circuit board (PCB) 608. Pins 106 connect the device 100 to the PCB 608 and pins 604 connect the memory controller 602 to the PCB 608. Traces and vias 606 in the PCB 608 couple the memory controller 602 to the packaged semiconductor memory device 100. The memory controller 602 transmits C/A signals (e.g., row access command signals, column access command signals, and write command signals) through respective traces and vias 606 to the packaged semiconductor memory device 100. For write operations, the memory controller 602 also transmits serial write data (and, in some embodiments, a data strobe signal) through respective traces and vias 606 to the packaged semiconductor memory device 100. In response to column access commands (e.g., RD1 and RD2, FIG. 3A), the packaged semiconductor memory device 100 transmits serial data (e.g., aggregated data 328, FIG. 3B, such as D1[7:0] and D2[7:0], FIG. 3A) to the memory controller 602.
FIG. 7A is a flow diagram illustrating a method 700 of operating a packaged semiconductor memory device (e.g., device 100 or 130, FIGS. 1A-1B) in which data is read from the device, in accordance with some embodiments. The packaged semiconductor memory device includes (702) a data pin, a first memory die (e.g., master die 200a, FIGS. 2A-2B) having a first memory core (e.g., core 202a, FIGS. 2A-2B), and a second memory die (e.g. slave die 200b, FIGS. 2A-2B) stacked with the first memory die and having a second memory core (e.g., core 202b, FIGS. 2A-2B).
Row access operations are performed (704) in parallel in a bank of the first memory core and a bank of the second memory core. For example, row access operations are performed in parallel in banks 204a-n and 204b-n (FIG. 2B) in response to a single row access command signal (e.g., the ACT command signal, FIG. 3A).
Column access operations are performed (706) in parallel in the bank of the first memory core and the bank of the second memory core. For example, column access operations are performed in parallel in banks 204a-n and 204b-n (FIG. 2B) in response to a single column access command signal (e.g., the RD1 command signal, FIG. 3A).
Data from the parallel column access operations is aggregated (708). In some embodiments, data accessed from the respective banks is serialized (710) in each die (e.g., by serializers 404a and 404b, FIGS. 4A-4B). The serialized data from the second memory die is provided (712) to the first memory die using a through-die via (e.g., through-die via 218, FIGS. 2A-2B and 4A-4B). The serialized data from each die is interleaved (714) in the first memory die (e.g., resulting in aggregated data stream 328, FIG. 3A, such as serial data stream D1 [7:0], FIG. 3B).
In some embodiments, a clock signal is provided from the first memory die to the second memory die using a through-die via (e.g., through-die via 216, FIGS. 2A-2B and 4A-4B). To provide (712) the serialized data from the second memory die to the first memory die, respective bits of the serialized data from the second memory die are transmitted to the first memory die during respective portions (e.g., portion 332, FIG. 3B) of the clock signal's cycle but not during other portions (e.g., portion 330, FIG. 3B) of the cycle.
The aggregated data is transmitted (716) from the data pin. In some embodiments, the data rate at which data in each die is serialized in operation 710 is a fraction of the data rate at which the aggregated data is transmitted in operation 716. For example, the data rate at which data in each die is serialized in operation 710 is half the data rate at which the aggregated data is transmitted in operation 716.
In some embodiments, a series of parallel column access operations is performed in the bank of the first memory core and the bank of the second memory core in response to a series of column access commands (e.g., in response to successive commands RD1 and RD2, FIG. 3A). Data from the series of parallel column access operations is aggregated and the aggregated data is transmitted via the data pin.
In some embodiments, the packaged semiconductor memory device (e.g., device 150, FIG. 1C) further includes a plurality of additional memory die stacked with the first and second memory die, each of which includes a memory core having a plurality of banks. Row access operations are performed in respective banks of the additional memory die, in parallel with the row access operations (704) in the first and second memory cores. Column access operations are then performed in the respective banks of the additional memory die, in parallel with the column access operations (706) in the first and second memory cores. In each memory die, the data accessed in the column access operations is serialized; the serialized data from the second memory die and the plurality of additional memory die is provided to the first memory die using a through-die via. The serialized data from each memory die is aggregated (e.g., interleaved) and transmitted (716) from the data pin. In some embodiments, the aggregated data is transmitted at a data rate equal to the data rate of the serialized data from each memory die multiplied by the number of memory die.
FIG. 7B is a flow diagram illustrating a method 750 of operating a packaged semiconductor memory device (e.g., device 100 or 130, FIGS. 1A-1B) in which data is written to the device, in accordance with some embodiments. The packaged semiconductor memory device includes (752) a data pin, a first memory die (e.g., master die 200a, FIGS. 2A-2B) having a first memory core (e.g., core 202a, FIGS. 2A-2B), and a second memory die (e.g., slave die 200b, FIGS. 2A-2B) stacked with the first memory die and having a second memory core (e.g., core 202b, FIGS. 2A-2B).
Serialized write data is received (754) in the first memory die from the data pin.
The serialized write data is provided (756) from the first memory die to the second memory die using a through-die via (e.g., through-die via 220, FIGS. 2A-2B and 5A-5B). In some embodiments, a data strobe is provided from the first memory die to the second memory die using a through-die via (e.g., through-die via 222, FIGS. 2A-2B and 5A-5B). For example, flip-flops 512a and 512b (FIGS. 5A-5B) using the data strobe to receive the respective first and second portions of the serialized write data.
A first portion of the serialized write data is deserialized (758) in the first memory die (e.g., by deserializer 514a, FIGS. 5A-5B). The deserialized first portion is provided (760) to the first memory core. A second portion of the serialized write data is deserialized (762) in the second memory die (e.g., by deserializer 514b, FIGS. 5A-5B). The deserialized second portion is provided (764) to the second memory core.
The methods 700 (FIG. 7A) and 750 (FIG. 7B) thus allow for data to be read from and written to stacked memory die coupled by through-die vias. While the methods 700 (FIG. 7A) and/or 750 (FIG. 7B) include a number of operations that appear to occur in a specific order, it should be apparent that the methods 700 (FIG. 7A) and/or 750 (FIG. 7B) can include more or fewer operations, which can be executed serially or in parallel. Two or more operations may be combined into a single operation.
The circuitry of FIGS. 2A-2B, 4A-4B, and 5A-5B provides an efficient way of coupling two or more memory die with through-die vias. Because data fetched from the cores in the method 700 (FIG. 7A) is serialized in each die before being aggregated, a single through-die via 218 is used to transmit data from the slave die to the master die in each instance of a read path 400 (FIGS. 4A-4B). Similarly, because write data is deserialized in each die and the write data provided from the master die to the slave die is therefore serialized (e.g., as in the method 750, FIG. 7B), two through-die vias 220 and 222 are used to transmit write data and the data strobe from the master die to the slave die in each instance of a write path 500 (FIGS. 5A-5B).
Also, aggregating data from each die in the stack allows the column-data-width and the page size of each die in the stack to be reduced. For example, when two die 200a and 200b are stacked as shown in FIGS. 2A-2B, the column-data-width of each die is half the size it would otherwise be (e.g., each die fetches four bits instead of eight bits during a column access operation). The reduced column-data-width reduces die area. The reduced page size reduces power supply noise, IR drops, and internal voltage droop in the die, resulting in improved power integrity and more robust and reliable performance. In some embodiments, this improved power integrity and performance can be traded to reduce the limit on how many banks can be activated in a specified period (e.g., to reduce the four-activate window tFAW).
The foregoing description, for purpose of explanation, has been described with reference to specific embodiments. However, the illustrative discussions above are not intended to be exhaustive or to limit all embodiments to the precise forms disclosed. Many modifications and variations are possible in view of the above teachings. The disclosed embodiments were chosen and described to best explain the underlying principles and their practical applications, to thereby enable others skilled in the art to best implement various embodiments with various modifications as are suited to the particular use contemplated.

## Claims

1. A packaged semiconductor memory device, comprising:
a data pin;
a first memory die comprising:
a first data interface coupled to the data pin, and
a first memory core having a plurality of banks; and

a second memory die stacked with the first memory die and comprising a second memory core having a plurality of banks; wherein:
a respective bank of the first memory core and a respective bank of the second memory core are to perform parallel row access operations in response to a first command signal and parallel column access operations in response to a second command signal; and
the first data interface is to provide aggregated data from the parallel column access operations to the data pin.

2. The packaged semiconductor memory device of claim 1, wherein:
the respective bank of the first memory core and the respective bank of the second memory core are to perform a series of parallel column access operations in response to a series of column access commands; and
the first data interface is to provide aggregated data from the series of parallel column access operations to the data pin.

3. The packaged semiconductor memory device of claim 1, wherein:
the first memory die further comprises a first data path, coupled between the first memory core and the first data interface, comprising a serializer to serialize data accessed from the respective bank of the first memory core;
the second memory die further comprises a second data path, coupled to the second memory core, comprising a serializer to serialize data accessed from the respective bank of the second memory core; and
the memory device further comprises a first through-die via, coupled to the second data path and the first data interface, to provide the serialized data from the second data path to the first data interface.

4. The packaged semiconductor memory device of claim 3, wherein the first interface is to provide interleaved serial data from the first and second data paths as the aggregated data.

5. The packaged semiconductor memory device of claim 3, wherein:
the memory device further comprises a second through-die via to provide a clock signal from the first memory die to the second memory die, the clock signal having an associated clock cycle;
the second data path comprises an output, coupled to the first data interface by the first through-die via, to transmit a data bit during a first portion of the clock cycle and to be in a high-impedance state during a second portion of the clock cycle; and
the first data path comprises an output, coupled to the first data interface, to transmit a data bit during the second portion of the clock cycle and to be in a high-impedance state during the first portion of the clock cycle.

6. The packaged semiconductor memory device of claim 3, wherein:
the memory device comprises a plurality of pins including the data pin; and
the second memory die comprises a second data interface coupled to the second data path and not coupled to the plurality of pins.

7. The packaged semiconductor memory device of claim 3, wherein:
the first data interface is to provide the aggregated data to the data pin at a first data rate;
the first data path is to provide serialized data to the first data interface at a second data rate that is a fraction of the first data rate; and
the second data path is to provide serialized data to the first data interface at the second data rate.

8. The packaged semiconductor memory device of claim 7, wherein the second data rate is half the first data rate.

9. The packaged semiconductor memory device of claim 7, wherein:
the memory device comprises a number of memory die including the first and second memory die; and
the second data rate equals the first data rate divided by the number of memory die.

10. The packaged semiconductor memory device of claim 3, wherein:
the memory device further comprises a third through-die via to provide serialized write data from the first data interface to the second data path;
the first data path further comprises a deserializer to deserialize a first portion of the write data and an output to provide the deserialized first portion to the first memory core; and
the second data path further comprises a deserializer to deserialize a second portion of the write data and an output to provide the deserialized second portion to the second memory core.

11. The packaged semiconductor memory device of claim 10, wherein the first and second portions of the write data respectively comprise alternating bits of the write data.

12. The packaged semiconductor memory device of claim 10, wherein:
the memory device further comprises a fourth through-die via to provide a data strobe from the first memory die to the second memory die, the data strobe having an associated cycle;
the first data path comprises an input, coupled to the first data interface, to receive the write data during a first portion of the cycle and to disregard the write data during a second portion of the cycle; and
the second data path comprises an input, coupled to the first data interface by the first through-die via, to receive the write data during the second portion of the cycle and to disregard the write data during the first portion of the cycle.

13. The packaged semiconductor memory device of claim 10, wherein:
the data pin is an output data pin; and
the memory device further comprises an input data pin, coupled to the first data interface, to receive the serialized write data.

14. The packaged semiconductor memory device of claim 10, wherein the data pin is bidirectional.

15. The packaged semiconductor memory device of claim 1, wherein:
the first memory die comprises command and address (C/A) decode circuitry to decode the first and second command signals; and
the memory device further comprises a fifth through-die via, coupled between the C/A decode circuitry and the second memory core, to provide the decoded first and second command signals to the second memory core.

16. The packaged semiconductor memory device of claim 15, further comprising a plurality of command and address (C/A) pins to receive the first and second command signals.

17. The packaged semiconductor memory device of claim 15, wherein the second memory die comprises C/A decode circuitry coupled to the second memory core and configurable to be deactivated during operation of the memory device.

18. The packaged semiconductor memory device of claim 1, wherein the data pin comprises a solder ball, bump, or micro-bump.

19. The packaged semiconductor memory device of claim 1, further comprising a plurality of additional memory die stacked with the first and second memory die and each comprising a memory core having a plurality of banks, wherein:
a respective bank of each memory core is to perform a row access operation in parallel with respective banks of the other memory cores in response to the first command signal and is to perform a column access operation in parallel with the respective banks of the other memory cores in response to the second command signal; and
the first data interface is to provide aggregated data from each of the memory cores to the data pin.

20. The packaged semiconductor memory device of claim 19, wherein:
each memory die comprises a data path coupled to its memory core to serialize data accessed from the respective bank; and
the memory device further comprises a through-die via, coupled to the data path of each memory die, to provide serialized data from the second memory die and the plurality of additional memory die to the first data interface.

21. A method of operating a packaged semiconductor memory device, wherein the packaged semiconductor memory device comprises a data pin, a first memory die having a first memory core, and a second memory die stacked with the first memory die and having a second memory core, the method comprising:
performing parallel row access operations in a bank of the first memory core and a bank of the second memory core in response to a first command signal;
performing parallel column access operations in the bank of the first memory core and the bank of the second memory core in response to a second command signal;
aggregating data from the parallel column access operations; and
transmitting the aggregated data from the data pin.

22. The method of claim 21, further comprising:
performing a series of parallel column access operations in the bank of the first memory core and the bank of the second memory core in response to a series of column access commands;
aggregating data from the series of parallel column access operations; and
transmitting the aggregated data from the series of parallel column access operations from the data pin.

23. The method of claim 21, further comprising:
in the first memory die, serializing first data from the bank of the first memory core;
in the second memory die, serializing second data from the bank of the second memory core; and
providing the serialized second data to the first memory die using a first through-die via.

24. The method of claim 23, wherein the aggregating comprises interleaving the serialized first data with the serialized second data.

25. The method of claim 23, further comprising providing a clock signal from the first memory die to the second memory die using a second through-die via, wherein:
the clock signal has an associated clock cycle; and
providing the serialized second data to the first memory die comprises transmitting a data bit of the second data during a first portion of the clock cycle and not transmitting any of the second data during a second portion of the clock cycle.

26. The method of claim 23, wherein:
the aggregated data is transmitted at a first data rate; and
the first data and the second data are both serialized at a second data rate that is a fraction of the first data rate.

27. The method of claim 26, wherein the second data rate is half the first data rate.

28. The method of claim 26, wherein:
the memory device comprises a number of memory die including the first and second memory die; and
the second data rate equals the first data rate divided by the number of memory die.

29. The method of claim 21, further comprising:
receiving serialized write data in the first memory die; and
providing the serialized write data from the first memory die to the second memory die using a third through-die via.

30. The method of claim 29, further comprising:
deserializing a first portion of the serialized write data in the first memory die and providing the deserialized first portion to the first memory core; and
deserializing a second portion of the serialized write data in the second memory die and providing the deserialized second portion to the second memory core.

31. The method of claim 29, further comprising providing a data strobe from the first memory die to the second memory die using a fourth through-die via.

32. The method of claim 21, further comprising:
in the first memory die, decoding the first and second command signals; and
providing the decoded first and second command signals to the second memory core using a fifth through-die via.

33. The method of claim 21, wherein the packaged semiconductor memory device further comprises a plurality of additional memory die stacked with the first and second memory die and each comprising a memory core having a plurality of banks, the method further comprising:
performing row access operations in respective banks of the additional memory die, in parallel with the row access operations in the first and second memory cores; and
performing column access operations in the respective banks of the additional memory die, in parallel with the column access operations in the first and second memory cores;
wherein the aggregating comprises aggregating data from each memory die.

34. The method of claim 33, further comprising:
in each memory die, serializing data accessed in the parallel column access operations; and
providing serialized data from the second memory die and the plurality of additional memory die to the first memory die using a through-die via.

35. An electronic system, comprising:
a semiconductor memory controller; and
a packaged semiconductor memory device coupled to the memory controller and comprising a first memory die and a second memory die stacked with the second memory die, wherein:
the first memory die comprises a first memory core having a plurality of banks;
the second memory die comprises a second memory core having a plurality of banks;
a respective bank of the first memory core and a respective bank of the second memory core are to perform parallel row access operations in response to a first command signal from the memory controller and parallel column access operations in response to a second command signal from the memory controller; and
the first memory die further comprises a data interface to transmit aggregated data from the parallel column access operations to the memory controller.