Semiconductor memory device with in memory logic operations

This application claims the benefit of and priority to Japanese Patent Application No. 2017-180319, filed Sep. 20, 2017, the entire contents of which are incorporated herein by reference.

Embodiments described herein relate generally to a semiconductor memory device which includes a nonvolatile memory.

Deep learning is applied in various fields such as image processing and speech recognition, and expectations for hardware capable of performing an operation process on a large amount of data processed by the deep learning are increased. In such a device for performing the operation process on a large amount of data, data can be read from a memory cell array, and the read data can be supplied to an operation circuit to perform the operation process.

FIG. 1 is a circuit diagram illustrating a configuration of a semiconductor memory device of a first embodiment.

FIG. 2 is a diagram illustrating a circuit connection between a nonvolatile memory, a read circuit array, a multiply-accumulate operator array, and an operation controller illustrated in FIG. 1 .

FIG. 3 is a diagram illustrating a configuration of a multiply-accumulate operator in the semiconductor memory device of the first embodiment.

FIG. 4 is a circuit diagram of a memory cell array of the nonvolatile memory in the semiconductor memory device of the first embodiment.

FIG. 5 is a circuit diagram illustrating a configuration of a semiconductor memory device of a modification of the first embodiment.

FIG. 6 is a circuit diagram illustrating a configuration of a semiconductor memory device of a second embodiment.

FIG. 7 is a cross-sectional view illustrating a configuration of the semiconductor memory device of the second embodiment.

An exemplary embodiment provides a semiconductor memory device which is able to realize high speed and low power consumption of an operation process in an operation circuit.

In general, according to some embodiments, a semiconductor memory device includes a nonvolatile memory which stores data in a nonvolatile manner, a read circuit which reads the data from the nonvolatile memory, an operation circuit which receives the read data from the read circuit and carry out at least one operation, a first bus which is connected between the read circuit and the operation circuit and having a first bit width, a controller circuit which is electrically connected to the operation circuit, and a second bus which is connected to the controller and having a second bit width smaller than the first bit width.

Hereinafter, embodiments will be described with reference to the drawings. In the following explanation, the components having the same function and configuration are given the same reference signs. In addition, devices and methods to specify technical ideas of the present disclosure will be exemplified for the embodiments described below, and materials, shapes, structures, and arrangements of the components may be defined in various forms including the following description.

Each functional block may be realized through one or more computer hardware and/or computer software components, or a combination thereof. Each functional block is not necessary to be distinctive as the examples of the present disclosure. For example, some of functions described as being executed by an exemplary functional block may be executed by a functional block different from the exemplary functional block. Further, the exemplary functional block may be subdivided into detailed functional blocks.

A semiconductor memory device of a first embodiment will be described.

First, a configuration of a semiconductor memory device according to the first embodiment will be described. FIG. 1 is a circuit diagram illustrating the configuration of the semiconductor memory device of the first embodiment.

As illustrated in the drawing, a semiconductor memory device 100 includes a nonvolatile memory 10 , a read circuit array 20 , a multiply-accumulate operator array 30 , an input buffer 40 , an output buffer 50 , an operation controller 60 , a parallel conversion circuit 70 , and a memory controller 80 . In some embodiments, the operation controller 60 and the memory controller 80 are connected to an external host device 200 (for example, various types of computers).

The nonvolatile memory 10 includes, for example, a NAND flash memory. The NAND flash memory stores data in a memory cell in a nonvolatile manner. In the NAND flash memory, reading and programming are performed on a page basis, which means the memory cells in a page are simultaneously programmed and read. The size of page is typically several thousands of bits. A memory cell array of the NAND flash memory will be described below in detail.

In some embodiments, the read circuit array 20 includes sense amplifiers which are arranged in an array shape. The sense amplifiers may read the data stored in the memory cell of the nonvolatile memory 10 by a page or by bits smaller in number than bits of the page. Hereinafter, the data read by the read circuit array 20 are denoted as read data.

In some embodiments, a bus BU 1 having a first bit width (for example, bits of the page) is connected between the read circuit array 20 and the multiply-accumulate operator array 30 . The multiply-accumulate operator array 30 includes multiply-accumulate operators which are arranged in an array shape. The multiply-accumulate operator may perform a multiply-accumulate operation between the read data read from the nonvolatile memory 10 by the read circuit array 20 and an input data supplied from the input buffer 40 , and output an operation result (hereinafter, referred to as operation data).

In some embodiments, the input buffer 40 temporarily stores the input data received from the operation controller 60 . Further, the output buffer 50 may temporarily store the operation data received from the multiply-accumulate operator array 30 .

In some embodiments, the operation controller 60 and the host device 200 are connected by a bus BU 2 which has a second bit width smaller (or narrower) than the first bit width of the bus BU 1 . In other words, the bus width (the second bit width) of the bus BU 2 may be smaller than the bus width (the first bit width) of the bus BU 1 . The operation controller 60 may receive a command supplied from the host device 200 , and control the multiply-accumulate operator array 30 according to the received command. The operation controller 60 may supply the input data received from the host device 200 to the multiply-accumulate operator array 30 through the input buffer 40 . The operation controller 60 may further receive the operation data output from the multiply-accumulate operator array 30 through the output buffer 50 . Then, the operation controller 60 may output the operation data to the host device 200 using the bus BU 2 . The operation controller 60 may be configured as a circuit.

In some embodiments, similar to the multiply-accumulate operator array 30 , the parallel conversion circuit 70 is connected with the read circuit array 20 by the bus BU 1 which has the first bit width. The parallel conversion circuit 70 and the memory controller 80 may be connected by a bus BU 3 which has a third bit width. The parallel conversion circuit 70 may convert the read data transmitted through the bus BU 1 having the first bit width from the read circuit array 20 into data of the third bit width (for example, 8 bits) smaller than the first bit width (for example, 16 bits, 32 bits, or 64 bits). The third bit width may be the same as or different from the second bit width. Hereinafter, the data converted by the parallel conversion circuit 70 are denoted by conversion data. The parallel conversion circuit 70 may output the conversion data to the memory controller 80 using the bus BU 3 .

In some embodiments, the memory controller 80 and the host device 200 are connected by a bus BU 4 which has a fourth bit width smaller (or narrower) than the first bit width of the bus BU 1 . In other words, the bus width (the fourth bit width) of the bus BU 4 may be smaller than the bus width (the first bit width) of the bus BU 1 . The fourth bit width may be the same as or different from the third bit width. The memory controller 80 may receive a command supplied from the host device 200 , and control the nonvolatile memory 10 , the read circuit array 20 , and the parallel conversion circuit 70 according to the command. The memory controller 80 may further include an ECC circuit. The ECC circuit may perform an error checking and correcting process (ECC) on the data. In other words, the ECC circuit may generate parity on the basis of write data when the data are programmed, generate a syndrome from the parity to detect an error and correct the error when reading the data. The memory controller 80 may perform the ECC process on the conversion data received from the parallel conversion circuit 70 , and output the corrected data to the host device 200 using the bus BU 4 . The memory controller 80 may be configured as a circuit.

In some embodiments, in the semiconductor memory device 100 , the nonvolatile memory 10 , the read circuit array 20 , the multiply-accumulate operator array 30 , the input buffer 40 , the output buffer 50 , the operation controller 60 , and the parallel conversion circuit 70 are disposed on the same semiconductor chip (e.g., silicon substrate) or in the same package. In some embodiments, the memory controller 80 is disposed on the same semiconductor chip (e.g., silicon substrate) or in the same package. Further, the circuits may be arbitrarily disposed on the same semiconductor chip or in the same package.

Next, the detailed configurations of the nonvolatile memory 10 , the read circuit array 20 , the multiply-accumulate operator array 30 , and the operation controller 60 will be described. FIG. 2 is a diagram illustrating a circuit connection between the nonvolatile memory, the read circuit array, the multiply-accumulate operator array, and the operation controller illustrated in FIG. 1 .

In some embodiments, in the nonvolatile memory 10 , weighted data (hereinafter, referred to as parameter) is stored. The parameter may be used in the operation process in the multiply-accumulate operator array 30 . For example, referring to FIG. 2 , the nonvolatile memory 10 includes memory regions R 1 , R 2 , . . . , and Rn, where “n” is a natural number of 1 or more. In the memory regions R 1 , R 2 , . . . , and Rn, parameters D 1 , D 2 , . . . , and Dn may be stored respectively.

In some embodiments, in the memory cells in the memory regions R 1 , R 2 , . . . , and Rn, bit lines BL 1 , BL 2 , . . . , and BLn are connected, respectively. The bit lines BL 1 to BLn whose number correspond to bits of a page for example, may transmit signals of the memory regions R 1 to Rn in reading.

In some embodiments, the read circuit array 20 includes sense amplifiers S 1 , S 2 , . . . , and Sn which correspond to the bit lines BL 1 , BL 2 , . . . , and BLn, respectively. The bit lines BL 1 , BL 2 , . . . , and BLn may be connected to the sense amplifiers S 1 , S 2 , . . . , and Sn, respectively. The sense amplifiers S 1 to Sn may read the read data from the signals transmitted through the bit lines BL 1 to BLn. Further, the bit line may be configured to transmit one bit of data, or may be configured to transmit 8 bits, 16 bits, 32 bits, or 64 bits.

In some embodiments, the multiply-accumulate operator array 30 includes multiply-accumulate operators P 1 , P 2 , . . . , and Pn which correspond to the sense amplifiers S 1 , S 2 , . . . , and Sn (or the memory regions R 1 , R 2 , . . . , and Rn), respectively. The sense amplifiers S 1 , S 2 , . . . , and Sn and the multiply-accumulate operators P 1 , P 2 , . . . , and Pn may be connected by the bus BU 1 which has the first bit width. The bus BU 1 may include data lines DL 1 , DL 2 , . . . , and DLn. In other words, the sense amplifiers S 1 , S 2 , . . . , and Sn may be connected to the multiply-accumulate operators P 1 , P 2 , . . . , and Pn through the data lines DL 1 , DL 2 , . . . , and DLn.

In some embodiments, the number of data lines DL 1 to DLn of the bus BU 1 is set to be equal to the number of bit lines BL 1 to BLn. In some embodiments, the configuration may also be formed in which the number (the first bit width) of data lines DL 1 to DLn may be set to the number smaller than that of the bit lines, and larger than the number of bits of the second bit width of the bus BU 2 .

In some embodiments, the multiply-accumulate operation circuit array 30 is connected to the input buffer 40 and the output buffer 50 . Input data DI stored in the input buffer 40 may be supplied to the multiply-accumulate operator array 30 . Operation data DO output from the multiply-accumulate operator array 30 may be stored in the output buffer 50 .

In some embodiments, the operation controller 60 and the host device 200 are connected by the bus BU 2 which has the second bit width. Referring to FIG. 2 , the bus BU 2 includes external input/output lines EL 1 , EL 2 , . . . , and EL 8 , for example. In other words, the operation controller 60 may be connected to the host device 200 through the external input/output lines EL 1 , EL 2 , . . . , and EL 8 . The external input/output lines EL 1 to EL 8 may transmit input/output data between the operation controller 60 and the host device 200 . The second bit width (or bus width) of the bus BU 2 is, for example, 8 bits, which is smaller than the first bit width of the bus BU 1 .

Next, the detailed configuration of the multiply-accumulate operator Pn in the multiply-accumulate operator array 30 will be described. FIG. 3 is a diagram illustrating a configuration of the multiply-accumulate operator Pn.

In some embodiments, the multiply-accumulate operator Pn includes registers 31 , 32 , and 35 , a multiplier 33 , and an adder 34 . The operation of the multiply-accumulate operator is as follows. The register 31 may store the parameter Dn supplied from the sense amplifier Sn in the read circuit array 20 . The register 32 may store the input data DI supplied from the input buffer 40 . The multiplier 33 may receive the parameter Dn and the input data DI, and multiply the parameter Dn and the input data DI. The adder 34 may add multiplied data DP and data DO fed back from the register 35 , and output the added data to the register 35 . The register 35 may store the added data, and output the added data as the data DO to the output buffer 50 .

Next, a memory cell array of the NAND flash memory will be described as an example of the nonvolatile memory 10 . The NAND flash memory includes a plurality of blocks BLK (see FIG. 4 ) in the memory cell array. FIG. 4 is a circuit diagram of the block in the memory cell array which is provided in the NAND flash memory.

In some embodiments, as illustrated in FIG. 4 , the block BLK includes four string units SU 0 , SU 1 , SU 2 , and SU 3 , for example. Further, each string unit may include a plurality of NAND strings NS. Further, the number of string units SU in one block BLK and the number of NAND strings NS in one string unit SU are arbitrary. Hereinafter, “SU” denotes each of the plurality of string units SU 0 to SU 3 .

In some embodiments, each of the NAND string NS includes, for example, eight memory cell transistors MT 0 , MT 1 , . . . , and MT 7 and select transistors ST 1 and ST 2 . Further, a dummy transistor (not shown) may be provided between the memory cell transistor MT 0 and the select transistor ST 2 and between the memory cell transistor MT 7 and the select transistor ST 1 . Hereinafter, “MT” denotes each of the memory cell transistors MT 0 to MT 7 , and “ST” denotes each of the select transistors ST 1 and ST 2 .

In some embodiments, the memory cell transistor MT is provided with a layered gate which includes a control gate and a charge storage layer, and stores data in a nonvolatile manner. Further, the memory cell transistor MT may be a MONOS (Metal-Oxide-Nitride-Oxide-Silicon) type in which an insulating film is used as the charge storage layer, or may be an FG (Floating Gate) type in which a conductive film is used as the charge storage layer. Further, the number of memory cell transistors MT may be other numbers such as 16, 32, 64, or 128, in addition to “8” as shown in FIG. 4 . Furthermore, the number of select transistors (e.g., ST 1 and ST 2 ) is arbitrary.

In some embodiments, the sources or drains of the memory cell transistors MT 0 to MT 7 are connected in series between the select transistors ST 1 and ST 2 . As shown in FIG. 4 , the drain of the memory cell transistor MT 7 at the one end of the series connection is connected to the source of the select transistor ST 1 , and the source of the memory cell transistor MT 0 on the other end is connected to the drain of the select transistor ST 2 .

In some embodiments, the gates of the select transistors ST 1 of the string units SU 0 to SU 3 are connected to select gate lines SGD 0 , SGD 1 , SGD 2 , and SGD 3 respectively. Hereinafter, “SGD” denotes each of the select gate lines SGD 0 to SGD 3 . The gates of the select transistors ST 1 in the same string unit SU may be connected to the same select gate line SGD in common. For example, the gates of the select transistors ST 1 in the string unit SU 0 are connected to the select gate line SGD 0 in common.

In some embodiments, the gates of the select transistors ST 2 of the string units SU 0 to SU 3 are connected to the select gate line SGS. The gates of the select transistors ST 2 in the same string unit SU may be connected to the same select gate line in common. For example, the gates of the select transistors ST 2 in the string unit SU 0 may be connected to the select gate line SGS in common.

In some embodiments, the control gates of the memory cell transistors MT 0 to MT 7 in the same block BLK are respectively connected to word lines WL 0 to WL 7 in common. In other words, while the word lines WL 0 to WL 7 are connected between the plurality of string units SU in the same block BLK in common, the select gate lines SGD and SGS are independent at every string unit SU even in the same block.

In some embodiments, in the NAND strings NS disposed in the memory cell array in a matrix configuration, the drains of the select transistors ST 1 of the NAND strings NS of the same row are connected to any one of the bit lines BL 0 , BL 1 , . . . , and BL (n−1) in common. Further, “n” is a natural number of 1 or more. In FIG. 4 , the starting bit line is denoted as BL 0 . Hereinafter, in a case where the bit line BL is denoted, it means each of the bit lines BL 0 to BL(n−1). In other words, the bit line BL is connected to the NAND strings NS in the plurality of string units SU in common.

In some embodiments, the sources of the select transistors ST 2 of the NAND strings NS in the string units SU 0 to SU 3 are connected to a source line SL in common.

Reading and programming of data are collectively performed on the plurality of memory cell transistors MT commonly connected to any word line WL in any string unit SU of any block BLK. A unit of the reading and programming processing is called “page”.

In some embodiments, a data erase range may be set to other forms in addition to one block BLK. For example, the plurality of blocks may be collectively erased, or some regions in one block BLK may be collectively erased.

Next, the operation of the semiconductor memory device of the first embodiment will be described. In some embodiments, referring to FIG. 2 , the nonvolatile memory 10 includes the memory regions R 1 , R 2 , . . . , and Rn, and weighted data (or parameters) D 0 to Dn is stored in the memory regions R 1 , R 2 , . . . , and Rn, respectively.

In some embodiments, the sense amplifiers S 1 to Sn in the read circuit array 20 read the parameters from the memory regions R 1 to Rn, respectively.

In some embodiments, the multiply-accumulate operators P 1 to Pn in the multiply-accumulate operator array 30 receive the parameters D 1 to Dn read by the sense amplifiers S 1 to Sn through the data lines DL 1 to DLn, respectively. In other words, the parameters D 1 to Dn are transmitted from the sense amplifiers S 1 to Sn to the multiply-accumulate operators P 1 to Pn using the bus BU 1 (the data lines DL 1 to DLn) having a first bit width. The first bit width may correspond to the number of bits of the page. Alternatively, the first bit width may be smaller than the page, and correspond to the number of bits larger than the second bit width of the bus BU 2 . In some embodiments, the multiply-accumulate operators P 1 to Pn each receive the input data DI from the input buffer 40 . The multiply-accumulate operators P 1 to Pn may perform a multiply-accumulate operation with the parameters D 1 to Dn and the input data DI, and output the operation data DO.

In this way, the multiply-accumulate operators P 1 to Pn can receive the parameters D 1 to Dn obtained by one reading operation of the read circuit array 20 , and can perform the multiply-accumulate operation using the parameters D 1 to Dn. Therefore, it is possible to improve a processing speed of the multiply-accumulate operation in the multiply-accumulate operator array 30 .

In some embodiments, the output buffer 50 stores the operation data DO output from the multiply-accumulate operator array 30 , and outputs the operation data DO to the operation controller 60 .

In some embodiments, the operation controller 60 outputs the received operation data DO to the host device 200 through the external input/output lines EL 1 to EL 8 . In other words, the operation data DO is transmitted from the operation controller 60 to the host device 200 using the bus BU 2 (the external input/output lines EL 1 to EL 8 ) of the second bit width. The second bit width may be 8 bits, for example.

In some embodiments, the read circuit array 20 and the multiply-accumulate operator array 30 are directly connected, and the memory region Rn and the multiply-accumulate operator Pn are associated with each other. For example, a data distribution circuit is provided, and the data distribution circuit distributes the parameter Dn supplied from the sense amplifier Sn in the read circuit array 20 to the multiply-accumulate operator Pn corresponding to the parameter Dn. With reference to FIG. 5 , this example will be described.

FIG. 5 is a circuit diagram illustrating a configuration of a semiconductor memory device showing a modification of the first described embodiment. As illustrated in the drawing, a semiconductor memory device 110 includes a data distribution circuit 90 between the read circuit array 20 and the multiply-accumulate operator array 30 .

In some embodiments, the read circuit array 20 and the data distribution circuit 90 are connected by the bus BU 1 having a first bit width similarly to the multiply-accumulate operator array 30 in FIG. 1 . The data distribution circuit and the multiply-accumulate operator array 30 may be connected by a bus BU 5 of the first bit width similarly. The data distribution circuit 90 may distribute the parameter Dn supplied from the sense amplifier Sn in the read circuit array 20 to the multiply-accumulate operator Pn corresponding to the parameter Dn. In some embodiments, the data distribution circuit 90 includes a buffer configured to temporarily store the the parameters supplied from the sense amplifiers.

In some embodiments, the parameter Dn is distributed to the multiply-accumulate operator Pn corresponding to the parameter Dn by the data distribution circuit 90 . Therefore, there is no need to store the parameter Dn associated to the memory region Rn in advance. The remaining configuration is similar to those of the above-described first embodiment.

Effect of First Embodiment

According to the embodiments illustrated in FIG. 1 to FIG. 5 (as the first embodiment), it is possible to provide the semiconductor memory device which is able to realize high speed and low power consumption in operation.

In the first embodiment, the read data read from the nonvolatile memory 10 by the read circuit array 20 is supplied to the multiply-accumulate operator array 30 without any change. There is no need to adjust a bit width of the read data, for example, before the read data is supplied to the multiply-accumulate operator array 30 . Therefore, it is possible to improve a processing speed of the multiply-accumulate operation in the multiply-accumulate operator array 30 , and the power consumption can be reduced.

In addition, in the embodiment illustrated in FIG. 5 , the data (parameter Dn) corresponding to the multiply-accumulate operator Pn can be distributed by the data distribution circuit 90 , so that there is no need to store the data associated to the memory region Rn in the nonvolatile memory in advance, and the flexibility of the nonvolatile memory is improved.

With reference to FIG. 6 and FIG. 7 , the second embodiment will be described as to an example in which the nonvolatile memory 10 and the multiply-accumulate operator array 30 are disposed on different semiconductor chips, and are connected by a TSV (Through Silicon Via). The following description of the second embodiment highlights the differences from the first embodiment.

FIG. 6 is a circuit diagram illustrating a configuration of a semiconductor memory device of the second embodiment. In some embodiments, a package 300 includes semiconductor chips 310 and 320 . The terminals of the semiconductor chip 310 and the semiconductor chip 320 may be connected by a TSV (Through Silicon Via) 330 .

In some embodiments, in the semiconductor chip 310 , the nonvolatile memory 10 and the read circuit array 20 are disposed. In the semiconductor chip 320 , the multiply-accumulate operator array 30 , the input buffer 40 , the output buffer 50 , and the operation controller 60 may be disposed. The read circuit array 20 in the semiconductor chip 310 and the multiply-accumulate operator array 30 in the semiconductor chip 320 may be electrically connected by the TSV 330 .

The structure of the package 300 will be described using FIG. 7 , which depicts a cross-sectional view of the structure of the package 300 . In some embodiments, the package 300 is made as a package by stacking the semiconductor chip 320 and the semiconductor chip 310 on a package substrate 340 . As a method of stacking the semiconductor chips 320 and 310 , a TSV method may be used.

In the following, the structure of the package 300 will be described in detail. In some embodiments, on an upper surface of the package substrate 340 , the semiconductor chip 320 is disposed, and the semiconductor chip 310 is further disposed on the semiconductor chip 320 .

In some embodiments, in the semiconductor chip 320 , at least one TSV 321 is provided from an upper surface of the semiconductor chip 320 to a bottom surface of the semiconductor chip 320 . In some embodiments, in the semiconductor chip 310 , at least one TSV 330 is provided from an upper surface of the semiconductor chip 310 to a bottom surface of the semiconductor chip 310 . The TSVs 321 and 330 may be vias which are electrically conductive from the upper surface to the bottom surface of each semiconductor chip. A bump 331 may be provided between the TSVs 321 and 330 . The TSVs 321 and 330 and the bump 331 may be electrically connected between the semiconductor chips 320 and 310 .

In some embodiments, an electrode 322 is provided on the bottom surface of the semiconductor chip 320 . A bump 323 may be provided between the electrode 322 and the package substrate 340 . For example, the semiconductor chip 320 is electrically connected to the package substrate 340 through the TSV 321 , the electrode 322 , and the bump 323 . In addition, the semiconductor chip 310 may be electrically connected to the package substrate 340 through the TSV 330 , the bump 331 , the TSV 321 , the electrode 322 , and the bump 323 .

In some embodiments, a bump 342 is provided on the bottom surface of the package substrate 340 . In a case where the package 300 is a BGA (ball grid array) package, the bump 342 may be a soldering ball. The package substrate 340 may be electrically connected to the outside (for example, the host device 200 ) through the bump 342 .

In some embodiments, the package 300 is configured as an integrated circuit dedicated to the operation process. For example, when the parallel conversion circuit 70 and the memory controller 80 are added (see FIG. 1 ), it is possible to form a general purpose nonvolatile memory.

The remaining configuration and operation of the second embodiment are similar to those of the first embodiment.

Effect of Second Embodiment

In the second embodiment, the nonvolatile memory 10 and the multiply-accumulate operator array 30 are disposed on different semiconductor chips, and connected by the TSV. With such a configuration, even in a case where the nonvolatile memory 10 and the multiply-accumulate operator array 30 are not possible to be disposed on the same semiconductor chip, the read circuit array 20 and the multiply-accumulate operator array 30 can be connected by the TSV 330 , so that it is possible to realize a high-speed operation process and to reduce power consumption. The other effects are similar to those of the above-described first embodiment.

While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the present disclosure. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the present disclosure. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the present disclosure.