Patent Application
20170062440
The present application claims priority from Japanese Patent Application No. 2015-169379 filed on Aug. 28, 2015, the content of which is hereby incorporated by reference into this application.
The present invention relates to a semiconductor device and a method of manufacturing the semiconductor device. For example, the present invention is suitably used for a semiconductor device having a nonvolatile memory cell.
A memory cell including a split-gate-type cell using a metal-oxide-nitride-oxide-semiconductor (MONOS) film is used as a type of a nonvolatile memory, in some cases. At this time, the memory cell includes two MISFETs of a control transistor having a control gate electrode and a memory transistor having a memory gate electrode.
For example, Patent Document 1 (Specification of U.S. Pat. No. 7,847,343) discloses a non-volatile semiconductor memory device having a split gate configuration in which a memory gate is formed on a convex type substrate.
Moreover, Patent Document 2 (Japanese Patent Application Laid-Open Publication No. 2009-54707) discloses a split-gate type MONOS memory cell in which a thickness of a gate insulating film below an end portion in a gate-length direction of a selection gate electrode is made thicker than a thickness of a gate insulating film below a center portion in the gate-length direction thereof.
The present inventors research and develop a semiconductor device having a nonvolatile memory cell as described above, and study a Fowler-Nordheim (FN) type erasing method that erases the accumulated charge by injecting a hole from a memory gate (MG).
However, it has been found that retention property (charge holding property) is degraded when holes are injected from the memory gate (MG).
Accordingly, it is desired to develop a semiconductor device having a non-volatile memory cell having favorable retention property.
Other object and novel characteristics of the present invention will be apparent from the description of the present specification and the accompanying drawings.
The typical ones of the inventions disclosed in the present application will be briefly described as follows.
A semiconductor device shown in one embodiment disclosed in the present application has: a first gate electrode part placed above a semiconductor substrate; and a second gate electrode part placed above the semiconductor substrate so as to be adjacent to the first gate electrode part. Moreover, a first insulating film formed between the first gate electrode part and the semiconductor substrate has a thick film portion at its end portion on the second gate electrode part side. A thickness of this thick film portion is larger than a film thickness of an end portion of the first insulating film on the side opposite to the second gate electrode part side.
According to a semiconductor device described in a typical embodiment disclosed in the present application, a property of the semiconductor device can be improved.
In the embodiments described below, the invention will be described in a plurality of sections or embodiments when required as a matter of convenience. However, these sections or embodiments are not irrelevant to each other unless otherwise stated, and the one relates to the entire or a part of the other as a modification example, details, or a supplementary explanation thereof. Also, in the embodiments described below, when referring to the number of elements (including number of pieces, values, amount, range, and others), the number of the elements is not limited to a specific number unless otherwise stated or except the case where the number is apparently limited to a specific number in principle. The number larger or smaller than the specified number is also applicable.
Further, in the embodiments described below, the components (including element steps) are not always indispensable unless otherwise stated or except the case where the components are apparently indispensable in principle. Similarly, in the embodiments described below, when the shape of the components, positional relation thereof, and others are mentioned, the substantially approximate and similar shapes and others are included therein unless otherwise stated or except the case where it is conceivable that they are apparently excluded in principle. The same goes for the numerical value (including the number of pieces, numerical values, the amount, the range, and others) described above.
Hereinafter, the embodiments are described in detail based on the drawings. Note that components having the same function are denoted by the same or relative reference characters throughout all the drawings for describing the embodiments, and the repetitive description thereof is omitted. Also, when there are a plurality of similar units (portions), a symbol is added to a reference character of a generic name to indicate an individual or a specific portion in some cases. Also, in the following embodiments, the description of the same or similar portions is not repeated in principle unless otherwise required.
Also, in some drawings used in the embodiments, hatching is omitted even in a cross-sectional view so as to make the drawings easy to see. Also, hatching is used even in a plan view so as to make the drawings easy to see.
Also, in the cross-sectional view and the plan views, a size of each portion does not correspond to that of a practical device, and a specific portion is shown to be relatively large so as to make the drawings easy to see in some cases. Also, even when the cross-sectional views and the plan views correspond to each other, a specific portion is shown to be relatively large so as to make the drawings easy to see in some cases.
A configuration of a semiconductor device according to the present embodiment is described below, with reference to the drawings. The semiconductor device according to the present embodiment has a memory cell (a memory transistor, and a control transistor) formed in a memory cell region MA. The transistor mentioned herein is also called a metal insulator semiconductor field effect transistor (MISFET).
As shown in
More specifically, the memory cell has the control gate electrode part CG placed above a semiconductor substrate 100 (a fin F), and the memory gate electrode part MG placed above the semiconductor substrate 100 (the fin F) and next to the control gate electrode part CG. Each of the control gate electrode part CG and the memory gate electrode part MG is made of, for example, a silicon film. A metal silicide film SIL is formed on the upper side of the silicon film.
Moreover, in the present embodiment, the control gate electrode part CG and the memory gate electrode part MG are placed on a fin F having a rectangular parallelepiped shape via an insulating film (CG1, ONO). The fin F is formed of an upper portion of the semiconductor substrate 100 (fin F), and a plane shape of the fin F has a line shape (rectangular shape having its longer side in an X-direction) having a certain width (length in a Y-direction) as described later. In
Furthermore, between the control gate electrode part CG and the semiconductor substrate 100 (fins F), a control gate insulating film CGI is placed. This control gate insulating film CGI is made of, for example, a silicon oxide film. In the present embodiment, the control gate insulating film CGI has a large film thickness in its end portion on the memory gate electrode part MG side. In other words, the control gate insulating film CGI has a thick film portion CGIa at its end portion on the memory gate electrode part MG side. In the further other words, the film thickness in the end portion of the control gate insulating film CGI on the memory gate electrode part MG side (film thickness of the thin film portion CGIa) is larger than the film thickness in the end portion of the control gate insulating film CGI on the side opposed to the memory gate electrode part MG side. In this manner, by increasing the film thickness of the end portion of the control gate insulating film CGI on the memory gate electrode part MC side, the retention property (charge holding property) of the memory cell can be improved. The details will be described later.
The memory cell further has an insulating film ONO (106, 107, 108) placed between the memory gate electrode part MG and the semiconductor substrate 100 (the fin F). The insulating film ONO is formed of, for example, a lower layer insulating film 106, a middle layer insulating film 107 placed on the lower layer insulating film 106, and an upper layer insulating film 108 placed on the middle layer insulating film 107. The middle layer insulating film 107 becomes a charge accumulating part. The lower layer insulating film 106 is made of, for example, a silicon oxide film. The middle layer insulating film 107 is made of, for example, a silicon nitride film. The upper layer insulating film 108 is made of, for example, a silicon oxynitride film.
The insulating film ONO (106, 107, 108) is placed between the memory gate electrode part MG and the semiconductor substrate 100 (the fin F), and between the control gate electrode part CG and the memory gate electrode part MG.
The memory cell further has a drain region MD and a source region MS which are formed in the fin F of the semiconductor substrate 100. A sidewall insulating film (a sidewall, a side wall spacer) SW made of an insulating film is formed on a side wall part of a composite pattern of the memory gate electrode part MG and the control gate electrode part CG.
The drain region MD is made of an n+-type semiconductor region 119b, and an n+-type semiconductor region 119a. The n+-type semiconductor region 119a is formed to be self aligned with respect to the side wall of the control gate electrode part CG. The n+-type semiconductor region 119b is formed to be self aligned with respect to a side surface of the sidewall insulating film SW on the control gate electrode part CG side, and has a deeper junction depth and a higher impurity concentration than those of the n+-type semiconductor region 119a.
The source region MS is made of an n+-type semiconductor region 111b, and an n−-type semiconductor region 111a. The n−-type semiconductor region 111a is formed to be self aligned with respect to the side wall of the memory gate electrode part MG. The n+-type semiconductor region 111b is formed to be self aligned with respect to a side surface of the side wall insulating film SW on the memory gate electrode part MG side, and has a deeper junction depth and a higher impurity concentration than those of the n−-type semiconductor region 111a.
Such a source region (or drain region) formed of a low-concentration semiconductor region and a high-concentration semiconductor region is called a lightly doped drain (LDD) structure.
In the present specification, note that the drain region MD and the source region MS are defined on the basis of an operation time. It is collectively assumed that a semiconductor region to which a low voltage is applied at the time of a reading operation described later is called a source region MS, and that a semiconductor region to which a high voltage is applied at the time of the reading operation is called a drain region MD.
A metal silicide film SIL is formed on the upper portion of the drain region MD (n+-type semiconductor region 119b) and of the source region MS (n+-type semiconductor region 111b). Also, a metal silicide film SIL is formed on the upper portion of the memory gate electrode MG. Also, a cap insulating film CAP is formed on the upper portion of the control gate electrode CG. The cap insulating film CAP is made of, for example, a silicon nitride film.
Moreover, on the memory cell, interlayer insulating films IL1, IL2, IL3 and IL4 are formed. Each of these films is made of, for example, a silicon oxide film. A plug P1 is formed in the interlayer insulating film IL1, and a wiring M1 is formed on the plug P1. A plug P2 is formed in the interlayer insulating film IL3, and a wiring M2 is formed on the plug P2. Each of the wirings M1 and M2 is, for example, a buried wiring, and is made of a conductive material such as metal. Here, the wirings M1 and M2 are buried in the interlayer insulating films IL2 and IL4.
Here, the two memory cells shown in
A region between the control gate electrode parts CG which sandwich the drain region MD therebetween is assumed to be a region CCA. A region between the memory gate electrode parts MG which sandwich the source region MS therebetween is assumed to be a region MMA. In
As described above, a memory cell group (row) is configured by arranging a plurality of memory cells in the right-left direction of
As shown in
The control gate electrode parts CG (CG1, CG2, CG3, CG4) and memory gate electrode parts MG (MG1, MG2, MG3, MG4) of the memory cell extend in the Y-direction (direction intersecting an A-A cross sectional portion, vertical direction of the paper) so as to cross the fins F. Moreover, the source lines SL (SL1, SL2) extend in the Y-direction above the fins F so as to cross the fins F. The source region (MS, n+-type semiconductor region 111b) and the source line SL in the fin F are connected to each other through the plug (contact plug, connection part) P1. On the plurality of fins F, the source lines SL are placed in the Y-direction so as to connect plugs P1 on the source lines SL that are along each other in the Y-direction.
The control gate electrode part CG and the memory gate electrode part MG are placed so as to be symmetrical to each other with respect to the source line SL. The drain region MD (n+-type semiconductor region 119b) and the drain line DL in the fin F are connected to each other through the plug (contact plug, connection part) P1, P2 or others. On the respective fins F, the wirings (ML1, ML2, ML3, ML4) are placed in the X-direction so as to connect the plugs P2 on the drain region MD that are along each other in the X-direction.
As shown in
As shown in
The memory section B is configured of, for example, a control circuit 1001, an input/output circuit 1002, an address buffer 1003, a row decoder 1004, a column decoder 1005, a verification sense amplifier circuit 1006, a high-speed read sense amplifier circuit 1007, a writing circuit 1008, a memory cell array 1009, and a power supply circuit 1010. The control circuit 1001 stores temporarily and controls a control signal which is input from the logic section A. The control circuit 1001 also controls potentials of the control gate electrode part CG and the memory gate electrode part MG of the memory cell in the memory cell array 1009. Various types of data such as data read from the memory cell array 1009 or written to the memory cell array 1009, and program data, are input to and output from the input/output circuit 1002. The address buffer 1003 stores temporarily an address which is input from the logic section A. The row decoder 1004 and the column decoder 1005 are each connected to the address buffer 1003. The row decoder 1004 performs decoding based on a row address output from the address buffer 1003, and the column decoder 1005 performs decoding based on a column address output from the address buffer 1003. The verification sense amplifier circuit 1006 is a sense amplifier used for verification of erasing and writing, and the high-speed read sense amplifier circuit 1007 is a sense amplifier for reading, which is used at the time of data reading. The writing circuit 1008 controls the data writing by latching the written data which is input via the input/output circuit 1002. The power supply circuit 1010 is configured of a voltage generating circuit which generates various voltages used at the time of data writing, erasing, and verification, a current trimming circuit 1011 which generates a voltage of a certain value and which supplies the voltage to the writing circuit, and others.
Note that configurations shown in
Subsequently, an example of a basic operation of the memory cell is described. As the operations of the memory cell, three operations of the memory cell (1) reading operation, (2) erasing operation, and (3) writing operation are described. However, these operations have various definitions, and, particularly, the erasing operation and the writing operation may be defined to be opposite to each other.
For example, a positive potential of about 1.2 V is applied to the drain region MD on the control gate electrode part CG side, and a positive potential of about 1.2 V is applied to the control gate electrode part CG, so that the channel below the control gate electrode part CG is turned on. Then, by setting the memory gate electrode part MG to a predetermined potential (that is, a middle potential between a threshold value in the writing state and a threshold value in the erasing state), charge information that has been held can be read out as an electric current. Here, by setting the middle potential between the threshold value in the writing state and the threshold value in the erasing state to 0 V, it is not required to boost a voltage to be applied to the memory gate electrode part MG inside the power-supply circuit, so that a speed of the reading operation can be increased.
For example, a voltage of 12 V is applied to the memory gate electrode part MG, a voltage of 0 V is applied to the control gate electrode part CG, a voltage of 0 V is applied to the source region MS on the memory gate electrode part MG side, and a voltage of 0 V is applied to the drain region MD on the control gate electrode part CG side. In this manner, a hole is injected by the FN tunneling phenomena from the memory gate electrode part MG side into a silicon nitride film (middle layer insulating film 107, charge accumulating part), so that the erasing of the accumulated charge (here, electron) is performed (FN tunnel erasing method). However, the drain region MD on the control gate electrode part CG side may be electrically opened. Also, a potential of about 1 V may be applied to the control gate electrode part CG.
An erasing condition used when the erasing is further performed (N>1) after the verification subsequent to the first erasing (N=1) is not necessarily the same as that of the first erasing. A first example of an erasing pulse is shown in
A second example of an erasing pulse is shown in
For example, a voltage of 9.5 V is applied to the memory gate electrode part MG, a voltage of 0.9 V is applied to the control gate electrode part CG, a voltage of 5.7 V is applied to the source region MS on the memory gate electrode part MG side, and a potential lower than that of the source region, for example, 0.3 V, is applied to the drain region MD on the control gate electrode part CG side. Thus, electrons are collectively injected to the end portion of the memory gate electrode part MG on the control gate electrode part CG side. This injection method is referred to as an SSI (Source Side Hot Electron) injection method.
A writing condition used when the writing is further performed (N>1) after the verification subsequent to the first writing (N=1) is not necessarily the same as that of the first writing. A first example of a writing pulse is shown in
A second example of a writing pulse is shown in
In this manner, according to the present embodiment, since the thick film portion CGIa is formed in the end portion of the control gate insulating film CGI on the memory gate electrode part MG side, the retention property (charge holding property of the memory cell) can be improved.
As described above, when holes are injected from the memory gate electrode part MG side to the silicon nitride film (middle layer insulating film 107, charge accumulating part) by using an FN tunnel phenomenon through an FN tunnel erasing method, electric field concentration occurs on each of corners of the memory gate electrode part MG in the comparative example shown in
Subsequently, when electrons are injected to the end portion of the memory gate electrode part MG on the control gate electrode part CG side by the SSI injection method (SSI writing method), the holes cannot be completely eliminated due to a difference in an injection method. Therefore, as shown in
Then, since the localized electrons and the localized holes disappear in a pair, a predetermined amount of electrons cannot be maintained. Particularly, at the corner of the memory gate electrode part MG, a required amount of electrons cannot be maintained. In this manner, the retention property (holding property) is deteriorated (
Moreover, when the fin F structure is adopted, not only the upper surface of the fin F but also the side surface of the fin F serves as a channel region, and therefore, the mismatch in the distributions of the electrons and the holes tends to occur on the side surface of the fin F. Therefore, the deterioration in the retention property due to the localization of the electrons and the holes becomes large. For example, there is a case in which the width of a fin is about 10 nm and the height of the fin is about 40 nm. In this case, the channel region on the side surface of the fin F becomes larger than the channel region on the upper surface of the fin F, and therefore, a counter measure against the mismatch in the distributions of the electrons and the holes become important.
On the other hand, in the present embodiment, as shown in
Further, since the thick film portion CGIa is formed on not only the upper surface of the fin F but also on the side surface of the fin F, the mismatch in the distributions of electrons and holes can be moderated.
The thick film portion CGIa in the end portion of the control gate insulating film CGI on the memory gate electrode part MG side shown in
Each of
As shown in
Subsequently, by the SSI injection system, the electrons are injected to the end portion of the memory gate electrode part MG on the control gate electrode part CG side. In this case, as shown in
When the thick film portion CGIa is formed in the end portion of the control gate insulating film CGI on the memory gate electrode part MG side as in the present embodiment, it is found that the retention property is improved more than that in the case of the comparative example without the thick film portion. When the fin structure is adopted, a ratio of the side surface of the fin F to the channel region becomes high as described above, and therefore, it is very effective to improve the retention property by moderating the mismatch in the distributions of electrons/holes. In this manner, the configuration of the present embodiment is effectively applied to a memory cell having the fin structure.
In
As shown in
For the gate electrode part GE, for example, the same-layer film as that of the control gate electrode part CG can be used. Moreover, the peripheral transistor has a gate insulating film GI placed between the gate electrode part GE and the semiconductor substrate 100 (fin F). The gate insulating film GI such as a silicon oxide film can be used. Moreover, as the gate insulating film GI, the same-layer film as that of the control gate insulating film CGI may be used. However, in the end portion of the gate insulating film GI, it is not required to form the thick film portion CGIa.
Furthermore, on the side wall of the gate electrode part GE, a sidewall insulating film SW made of an insulating film is formed. The source/drain region SD is formed of an n+-type semiconductor region 119b and an n−-type semiconductor region 119a. The n−-type semiconductor region 119a is formed to be self-aligned with respect to the side wall of the gate electrode part GE. Moreover, the n+-type semiconductor region 119b is formed to be self-aligned with respect to the side surface of the sidewall insulating film SW, and has a deeper junction depth and a higher impurity concentration than those of the n−-type semiconductor region 119a. On the upper portion of this source/drain region SD (n+-type semiconductor region 119b), a metal silicide film SIL is formed. Moreover, on the upper portion of the gate electrode GE, a cap insulating film CAP is formed.
Moreover, on the peripheral transistor (cap insulating film CAP), interlayer insulating films IL1, IL2, IL3 and IL4 are formed. Each of these films is formed of, for example, a silicon oxide film. Note that plugs and wirings may be formed in the interlayer insulating films (IL1 to IL4) although not shown.
Subsequently, with reference to
First, as shown in
Then, by etching the surface of the insulating film, the surface of the element isolation region 103 is receded. Thus, the upper portion of the semiconductor substrate 100 between the element isolation regions 103 is formed into a convex portion (convex portion having a rectangular parallelepiped shape). This convex portion becomes the fin F (see a hatching portion in
At this time, it is preferable to adjust the width of the fin F, the width and depth of the element isolation region 103, the thickness of the memory gate electrode part MG, and others so that the bottom surface of the memory gate electrode part MG formed on the element isolation region 103 is upper than a half position of the height of the fin F (height difference between the upper surface of the fin F and the upper surface of the element isolation region 103). In this manner, by placing the bottom surface of the memory mate electrode part MG to be upper than the half position of the height of the fin F, the electrons can be more effectively injected to the corner portions of the memory gate electrode part MG by the injection electric field of hot electrons from the memory gate electrode part MG.
Subsequently, by removing the silicon nitride film HM2, a p-type impurity (for example, boron (B) or others) is ion-implanted while using the silicon oxide film HM1 as a through film. Thus, the p-type impurity is introduced into the fin F (semiconductor substrate 100 (fin F)). The introduction region of the p-type impurity is referred to as a p-type well (not shown). An n-type well may be formed by ion-implanting an n-type impurity to a region not shown.
Subsequently, as shown in
Subsequently, as shown in
Subsequently, as shown in
Subsequently, as shown in
Then, on the insulating film ONO (106, 107, 108), a conductive film 109 which becomes the memory gate electrode part MG is formed. For example, on the insulating film ONO (106, 107, 108), a polysilicon film having a thickness of about 40 nm is deposited as the conductive film 109 by a CVD method or others.
Then, as shown in
For example, the polysilicon film is etched back. In the etch-back process, by using anisotropic dry etching, the polysilicon film is removed by a predetermined thickness from the surface thereof. By this process, the polysilicon film can remain to be the side wall form (a side wall film form) on the side wall of the control gate electrode part CG via the insulating film ONO. Note that the polysilicon films remain on both sides of the region CCA, and one of them becomes the main gate electrode part MG. Note that the other side-wall-form polysilicon film is removed by a photolithography technique and a dry etching technique. In order to improve the processability of the memory gate, note that a dummy gate formation region may be formed. For example, in the end portion of the memory array, there is a risk of variation in the property even when a memory cell is formed. For example, the dimension of the polysilicon film is varied to cause the variation in the property of the memory cell. Therefore, such an end portion of the memory array is formed as the dummy gate formation region, and a polysilicon film formed on both end portions of the control gate electrode part CG is formed as a dummy gate, so that control is performed not to contribute to the operation of the memory cell.
Then, the insulating film ONO (106, 107, 108) is etched while using the memory gate electrode part MG as a mask. In this manner, the insulating film ONO (106, 107, 108) remains between the memory gate electrode part MG and the semiconductor substrate 100 (fin F), and between the control gate electrode part CG and the memory gate electrode part MG.
Then, as shown in
Then, a source region MS and a drain region MD are formed in the memory cell region MA, and the source/drain region SD is formed in the peripheral circuit region PA.
For example, an n−-type semiconductor regions 111a, 119a are formed by injecting n-type impurity such as arsenic (As) or phosphorus (P) into the semiconductor substrate 100 (fin F) while using the memory gate electrode part MG and the control gate electrode part CG as masks. At this time, the n−-type semiconductor region 111a is formed to be self aligned with respect to the side wall of the memory gate electrode part MG. And, an n−-type semiconductor region 119a is formed by injecting n-type impurity such as arsenic (As) or phosphorus (P) into the semiconductor substrate 100 (fin F) while using the gate electrode part GE as a mask. At this time, the n−-type semiconductor region 119a is formed to be self aligned with respect to the side wall of the gate electrode part GE.
Then, a sidewall film (a sidewall insulating film) SW is formed on the side wall of each of the memory gate electrode part MG, the control gate electrode part CG, and the gate electrode part GE. For example, a silicon oxide film is deposited on the semiconductor substrate 100 (fin F) including the memory gate electrode part MG, the control gate electrode part CG, and the gate electrode part GE by a CVD method or others. The sidewall film SW is formed by removing the silicon oxide film by a predetermined thickness from the surface thereof, by using anisotropic dry etching. Then, n+-type semiconductor regions 111b, 119b are formed by injecting n-type impurity such as arsenic (As) or phosphorus (P) into the semiconductor substrate 100 (fin F) while using the memory gate electrode part MG, the control gate electrode part CG, the gate electrode part GE, and the side wall insulating film SW as masks. At this time, the n+-type semiconductor regions 111b, 119b are formed to be self aligned with respect to the sidewall insulating film SW. The n+-type semiconductor region 111b has a higher impurity concentration and a deeper junction depth than those of the n−-type semiconductor region 111a. The n+-type semiconductor region 119b has a higher impurity concentration and a deeper junction depth than those of the n−-type semiconductor region 119a. By this process, the source region MS including the n−-type semiconductor region 111a and the n+-type semiconductor region 111b is formed, and the drain region MD including the n−-type semiconductor region 119a and the n+-type semiconductor region 119b is formed. Also, the source/drain region SD including the n+-type semiconductor region 119a and the n+-type semiconductor region 119b is formed.
Then, a metal silicide film SIL is formed on the memory gate electrode part MG, the source region MS, the drain region MD, and the source/drain region SD by using a salicide technique.
For example, a metal film (now shown) is formed on the memory gate electrode part MG, the source region MS, the drain region MD, and the source/drain region SD, and then, the semiconductor substrate 100 (fin F) is subjected to a heat treatment, so that the metal film reacts with the memory gate electrode part MG, the source region MS, the drain region MD, and the source/drain region SD. As a result, a metal silicide film SIL is formed. The metal film is made of, for example, nickel (Ni), a nickel-platinum (Pt) alloy, or others, and can be formed by a sputtering method or others. Then, an unreacted metal film is removed. By the metal silicide film SIL, contact resistance and diffusion resistance can be reduced.
After that, as shown in
By the above-described manufacturing process, the semiconductor device according to the present embodiment can be formed.
In the semiconductor device of the first embodiment, the thick film portion of the control gate insulating film CGI is prepared as a single-layer film (single layer thermal-oxide film). However, the thick film portion of the control gate insulating film CGI may be prepared as a stacked film (for example, a stacked film of a thermal-oxide film and a deposit film).
Hereinafter, with respect to drawings, a structure of a semiconductor device of the present embodiment will be described.
A semiconductor device of the present embodiment has a memory cell (memory transistor, control transistor) formed in a memory cell region MA and a peripheral transistor formed in a peripheral circuit region PA (see
Each of
As shown in
More specifically, the memory cell has the control gate electrode part CG placed on the semiconductor substrate 100 (fin F) and the memory gate electrode part MG which is placed on the semiconductor substrate 100 (fin F) and which is adjacent to the control gate electrode part CG.
The control gate electrode part CG and the memory gate electrode part MG are placed on the rectangular-parallelepiped-shape fin F via a gate insulating film. The fin F is made of an upper portion of the semiconductor substrate 100 (fin F), and a plane shape of the fin F has a line shape (rectangular shape having its longer side in an X-direction) having a certain width (length in a Y-direction).
The control gate electrode part CG and the memory gate electrode part MG extend in the Y-direction (direction intersecting an A-A cross-sectional portion, that is, vertical direction in the paper) so as to cross the fin F (see
The memory gate electrode part MG is formed of, for example, a polysilicon film.
Moreover, the control gate electrode part CG is formed of a stacked film of a silicon germanium film 105a and a polysilicon film 105b formed thereon. Here, the end portion of the silicon germanium film 105a on the memory gate electrode part MG side is retreated from the end portion of the polysilicon film 105b on the memory gate electrode part MG side. That is, a hollow portion (concave portion, undercut portion, see “R” of
Furthermore, the insulating films ONO (106, 107, 108) between the memory gate electrode part MG and the semiconductor substrate 100 (fin F) is provided, and a control gate insulating film CGI between the control gate electrode part CG and the semiconductor substrate 100 (fin F) is provided.
The insulating films ONO is formed of, for example, the lower layer insulating film 106, the middle layer insulating film 107 formed thereon, and the upper layer insulating film 108 further formed thereon.
The control gate insulating film CGI has a thick film portion CGIa in its end portion on the memory gate electrode part MG side. This thick film portion CGIa is formed of a stacked film. That is, the thick film portion CGIa is formed of a stacked film of a first insulating film portion and a second insulating film portion formed thereon. The first insulating film portion is a portion in an end portion of an insulating film 104 on the memory gate electrode part MG side, the insulating film 104 through which a film thickness is almost the same being placed on the semiconductor substrate 100 (fin F) between the control gate electrode part CG and the semiconductor substrate 100 (fin F). The second insulating film portion is a part of the lower layer insulating film 106 of the insulating films ONO (106, 107, 108) placed between the memory gate electrode part MG and the semiconductor substrate 100 (fin F), the part being a portion 106a of the end portion on the control gate electrode part CG side. This portion 106a is placed so as to come into a lower portion of the control gate electrode part CG, the lower portion being a lower portion of the longitudinal portion (vertical portion) of the lower layer insulating film 106.
In this manner, by increasing the film thickness of the end portion of the control gate insulating film CGI on the memory gate electrode part MG side, the retention property (charge holding property) of the memory cell can be improved as explained in the first embodiment.
Moreover, the memory cell further has a drain region MD and a source region MS formed in the fin F of the semiconductor substrate 100. Furthermore, a metal silicide film SIL is formed on the upper portions of the drain region MD (n+-type semiconductor region 119b), the source region MS (n+-type semiconductor region 111b), etc. And, a metal silicide film SIL is formed on the upper portion of the memory gate electrode part MG. And, a cap insulating film CA is formed on the upper portion of the control gate electrode part CG. The cap insulating film CAP is formed of, for example, a silicon nitride film.
Furthermore, on the memory cell, interlayer insulating films (IL1, IL2, IL3, IL4) are formed. In these films, plugs (P1, P2) and wirings (M1, M2) are formed.
In the above-described memory cell, note that the configuration of the memory array (
Moreover, in the semiconductor device, in addition to the memory cell region MA, a peripheral circuit region PA in which a peripheral circuit is formed may be provided. Since the configuration of the peripheral transistor formed in the peripheral circuit region PA is the same as that of the first embodiment, the description thereof will be omitted (see
Subsequently, with reference to
First, as shown in
Subsequently, the silicon nitride film HM2 is removed, a p-type impurity (for example, boron (B) or others) is ion-implanted thereto by using the silicon oxide film HM1 as a through film, so that a p-type well (not shown) is formed.
Subsequently, as shown in
Subsequently, on the insulating film 104, a conductive film for the control gate electrode part CG and the gate electrode part GE is formed. For example, a stacked film of a silicon germanium film 105a having a film thickness of about 8 nm and a polysilicon film 105b having a film thickness of about 60 nm is formed. That is, the control gate electrode part CG is formed of the silicon germanium film 105a and the polysilicon film 105b. Moreover, the gate electrode part GE is formed of the silicon germanium film 105a and the polysilicon film 105b. These films are formed by using, for example, a CVD method or others. Subsequently, the cap insulating film CAP is formed on the polysilicon film 105b. For example, on the polysilicon film 105b, a silicon nitride film having a thickness of about 20 nm is formed by using a CVD method or others.
Subsequently, as shown in
Subsequently, as shown in
Subsequently, on the lower layer insulating film 106, for example, a silicon nitride film is formed as a middle layer insulating film 107 to be deposited to have a thickness of about 7 nm by a CVD method or others. The middle layer insulating film 107 functions as a charge accumulating part of a memory cell. Subsequently, on the middle layer insulating film 107, an upper layer insulating film 108 is formed. Subsequently, on the middle layer insulating film 107, for example, a silicon oxide film is deposited as the upper layer insulating film 108 to have a thickness of about 9 nm by a CVD method or others.
Subsequently, on the insulating film ONO (106, 107, 108), a conductive film 109 which becomes the memory gate electrode part MG is formed. For example, on the insulating film ONO (106, 107, 108), a polysilicon film 105b having a thickness of about 40 nm is deposited as the conductive film 109 by a CVD method or others.
Subsequently, as shown in
Subsequently, as shown in
Subsequently, a source region MS and a drain region MD are formed in the memory cell region MA, and a source/drain region SD is formed in the peripheral circuit region PA. These regions can be formed as similar to the first embodiment.
Subsequently, a metal silicide film SIL is formed on the memory gate electrode part MG, the source region MS, the drain region MD, and the source/drain region SD by using a salicide technique. The metal silicide film SIL can be formed as similar to the first embodiment.
After that, as shown in
By the above-described manufacturing process, the semiconductor device according to the present embodiment can be formed.
In the semiconductor device of the first embodiment, the gate electrode part GE of the peripheral transistor is formed by the same film as that of the control gate electrode part CG. However, the gate electrode part GE of the peripheral transistor may be formed by a film different from that of the control gate electrode part CG.
Hereinafter, with respect to drawings, a structure of a semiconductor device of the present embodiment will be described.
A semiconductor device of the present embodiment has a memory cell (memory transistor, control transistor) formed in a memory cell region MA and a peripheral transistor formed in a peripheral circuit region PA.
Each of
As shown in
More specifically, the memory cell has the control gate electrode part CG placed on the semiconductor substrate 100 (fin F) and the memory gate electrode part MG which is placed on the semiconductor substrate 100 (fin F) and which is adjacent to the control gate electrode part CG.
The control gate electrode part CG and the memory gate electrode part MG are placed on the rectangular-parallelepiped-shape fin F via a gate insulating film. The fin F is made of an upper portion of the semiconductor substrate 100 (fin F), and a plane shape of the fin F has a line shape (rectangular shape having its longer side in an X-direction) having a certain width (length in a Y-direction).
The control gate electrode part CG and the memory gate electrode part MG extend in the Y-direction (direction intersecting an A-A cross-sectional portion, that is, vertical direction in the paper) so as to cross the fin F (see
Each of the memory gate electrode part MG and the control gate electrode part CG is formed of, for example, a polysilicon film.
And, the control gate insulating film CGI is placed between the control gate electrode part CG and the semiconductor substrate 100 (fin F). This control gate insulating film CGI is formed of, for example, a silicon oxide film. And, this control gate insulating film CGI has a thick film portion CGIa in its end portion on the memory gate electrode part MG side.
In this manner, by increasing the film thickness of the end portion of the control gate insulating film CGI on the memory gate electrode part MG side, the retention property (charge holding property) of the memory cell can be improved as explained in the first embodiment.
The memory cell further has the insulating films ONO (106, 107, 108) placed between the memory gate electrode part MG and the semiconductor substrate 100 (fin F).
Moreover, the memory cell further has a drain region MD and a source region MS formed in the fin F of the semiconductor substrate 100. Furthermore, a metal silicide film SIL is formed on the upper portions of the drain region MD (n+-type semiconductor region 119b), the source region MS (n+-type semiconductor region 111b), etc. And, a metal silicide film SIL is formed on the upper portion of the memory gate electrode part MG and the control gate electrode part CG.
Furthermore, on the memory cell, interlayer insulating films (IL1, IL2, IL3, IL4) are formed. In these films, plugs (P1, P2) and wirings (M1, M2) are formed.
In the above-described memory cell, note that the configuration of the memory array (
Moreover, in the semiconductor device, in addition to the memory cell region MA, a peripheral circuit region PA in which a peripheral circuit is formed may be provided. The configuration of the peripheral transistor formed in the peripheral circuit region PA will be described below.
As shown in
As the gate electrode part GE, for example, a film different from that of the control gate electrode part CG can be used. Moreover, the peripheral transistor has a gate insulating film GI placed between the gate electrode part GE and the semiconductor substrate 100 (fin F). As the gate insulating film GI, a film different from the control gate insulating film CGI can be used.
For example, as the gate insulating film GI, a stacked film of a thermal-oxide film and a high-k insulating film can be used. Moreover, as the gate electrode part GE, a metal electrode film can be formed. As the metal electrode film, a stacked film made of tantalum nitride/titanium/aluminum can be used. In this manner, an insulating film having a high dielectric constant film can be used as the gate insulating film GI, and a conductive film having a metal film or a metal alloy film can be used as the gate electrode part GE.
Moreover, the gate insulating film GI is formed on the bottom surface and side wall of the concave portion formed in an interlayer insulating film IL0. Moreover, the gate electrode part GE is buried inside the concave portion via the gate insulating film GI.
On the side wall portion of the gate electrode part GE, a sidewall insulating film SW made of an insulating film is formed. The source/drain region SD is made of an n+-type semiconductor region 119b and an n-type semiconductor region 119a. The n−-type semiconductor region 119a is formed so as to be self-aligned with respect to the side wall of the gate electrode part GE. Moreover, the n+-type semiconductor region 119b is formed so as to be self-aligned with respect to the side surface of the sidewall insulating film SW, and has a deeper junction depth and a higher impurity concentration than those of the n−-type semiconductor region 119a. On the upper portion of this source/drain region SD (n+-type semiconductor region 119b), a metal silicide film SIL is formed.
Moreover, on the peripheral transistor (cap insulating film CAP), interlayer insulating films IL1, IL2, IL3 and IL4 are formed. Each of these films is made of, for example, a silicon oxide film. In
Subsequently, with reference to
First, as shown in
Subsequently, the silicon nitride film HM2 is removed, a p-type impurity (for example, boron (B) or others) is ion-implanted thereto by using the silicon oxide film HM1 as a through film, so that a p-type well (not shown) is formed.
Subsequently, as shown in
Subsequently, on the insulating film 104, a polysilicon film for the control gate electrode part CG and the gate electrode part GE is formed by using a CVD method or others. Subsequently, a silicon nitride film having a thickness of about 30 nm is formed on the polysilicon film 105 as an insulating film IF1 by using a CVD method or others.
Subsequently, as shown in
Subsequently, as shown in
Subsequently, on the insulating film ONO (106, 107, 108), a conductive film (polysilicon film) 109 which becomes the memory gate electrode part MG is formed.
Subsequently, as shown in
Subsequently, an n−-type semiconductor region 111a is formed by injecting an n-type impurity such as arsenic (As), phosphorus (P) or others into the semiconductor substrate 100 (fin F) in the region MMA of the memory cell region MA. Subsequently, a sidewall film (sidewall insulating film) SW is formed on the side wall portion of the memory gate electrode part MG, and an n+-type semiconductor region 111b is formed by injecting the n-type impurity such as arsenic (As), phosphorus (P) or others into the semiconductor substrate 100 (fin F) in the region MMA. By these processes, a source region MS, made of the n−-type semiconductor region 111a and the n+-type semiconductor region 111b, is formed.
Subsequently, a buried insulating film BL for use in burying the region MMA of the memory cell region MA is formed. For example, on the entire surface of the semiconductor substrate 100, a silicon oxide film, more specifically, an SOG (Spin On Glass) film, is formed as the buried insulating film BL. The SOG film has a high wet-etching rate, and is preferably used for the buried insulating film BL.
Subsequently, as shown in
Subsequently, as shown in
Subsequently, as shown in
Subsequently, a metal silicide film SIL is formed on the memory gate electrode part MG, the control gate electrode part CG, the source region MS, the drain region MD, and the source/drain region SD by using a salicide technique. The metal silicide film SIL can be formed as similar to the first embodiment.
Subsequently, as shown in
Subsequently, the cap insulating film CAP, and the polysilicon film 105 and the insulating film 104 in the peripheral circuit region PA, are removed by etching. By this process, a concave portion (trench) is formed in the gate electrode part formation region of the peripheral transistor (see
Subsequently, as shown in
Subsequently, on the gate insulating film GI, a metal electrode film to be the gate electrode part GE is formed. For example, after forming a titanium nitride film on the gate insulating film GI as a barrier film (not shown), a metal electrode film is deposited on this titanium nitride film. As the metal electrode film, a stacked film having a film thickness of about 20 nm made of tantalum nitride/titanium/aluminum can be used. These films can be formed by, for example, a sputtering method or others. When a p-channel type MISFET is formed as the peripheral transistor, note that a stacked film having a film thickness of about 20 nm made of tantalum nitride/titanium nitride/tantalum nitride can be used as the metal electrode film.
Subsequently, as shown in
After that, as shown in
By the above-described manufacturing process, the semiconductor device according to the present embodiment can be formed.
In the semiconductor device of the first embodiment, the control gate insulating film CGI is prepared as a single layer thermal-oxide film. However, a flat portion and a thick film portion of the control gate insulating film CGI may be prepared as different films from each other (a thermal-oxide film and a deposit film).
Hereinafter, with respect to drawings, a structure of a semiconductor device of the present embodiment will be described.
A semiconductor device of the present embodiment has a memory cell (memory transistor, control transistor) formed in a memory cell region MA and a peripheral transistor formed in a peripheral circuit region PA (see
Each of
As shown in
More specifically, the memory cell has the control gate electrode part CG placed on the semiconductor substrate 100 (fin F) and the memory gate electrode part MG which is placed on the semiconductor substrate 100 (fin F) and which is adjacent to the control gate electrode part CG.
The control gate electrode part CG and the memory gate electrode part MG are placed on the rectangular-parallelepiped-shape fin F via a gate insulating film. The fin F is made of an upper portion of the semiconductor substrate 100 (fin F), and a plane shape of the fin F has a line shape (rectangular shape having its longer side in an X-direction) having a certain width (length in a Y-direction).
The control gate electrode part CG and the memory gate electrode part MG extend in the Y-direction (direction intersecting an A-A cross-sectional portion, that is, vertical direction in the paper) so as to cross the fin F (see
Each of the memory gate electrode part MG and the control gate electrode part CG is formed of, for example, a polysilicon film.
And, the control gate insulating film CGI is placed between the control gate electrode part CG and the semiconductor substrate 100 (fin F). This control gate insulating film CGI is formed of, for example, a silicon oxide film. And, this control gate insulating film CGI has a flat portion (lateral portion) in which the film thickness is almost the same and a thick film portion CGIa having a film thickness larger than that of the flat portion and being located in its end portion on the memory gate electrode part MG side.
In this manner, by increasing the film thickness of the end portion of the control gate insulating film CGI on the memory gate electrode part MG side, the retention property (charge holding property) of the memory cell can be improved as explained in the first embodiment.
The memory cell further has the insulating films ONO (106, 107, 108) placed between the memory gate electrode part MG and the semiconductor substrate 100 (fin F).
Moreover, the memory cell further has a drain region MD and a source region MS formed in the fin F of the semiconductor substrate 100. Furthermore, a metal silicide film SIL is formed on the upper portions of the drain region MD (n+-type semiconductor region 119b), the source region MS (n+-type semiconductor region 111b), etc. And, a metal silicide film SIL is formed on the upper portion of the memory gate electrode part MG and the control gate electrode part CG.
Furthermore, on the memory cell, interlayer insulating films (IL1, IL2, IL3, IL4) are formed. In these films, plugs (P1, P2) and wirings (M1, M2) are formed.
In the above-described memory cell, note that the configuration of the memory array (
Moreover, in the semiconductor device, in addition to the memory cell region MA, a peripheral circuit region PA in which a peripheral circuit is formed may be provided. The configuration of the peripheral transistor formed in the peripheral circuit region PA is the same as that in the case of the first embodiment, and therefore, the description thereof is omitted (see
Subsequently, with reference to
First, as shown in
Subsequently, the silicon nitride film HM2 is removed, a p-type impurity (for example, boron (B) or others) is ion-implanted thereto by using the silicon oxide film HM1 as a through film, so that a p-type well (not shown) is formed.
Subsequently, as shown in
Subsequently, on the insulating film HM3, a silicon nitride film having a thickness of about 80 nm is formed as an insulating film (sacrificed film, insulating film for spacer) SPM by using a CVD method or others.
Subsequently, as shown in
Subsequently, as shown in
Subsequently, as shown in
Subsequently, on the insulating film 104 and the insulating film SPM, a polysilicon film 105 having a film thickness of about 150 nm for the control gate electrode part CG and the gate electrode part GE is formed. Subsequently, the polysilicon film 105 is removed by using a CMP method or others, until the insulating film SPM is exposed. Subsequently, the insulating film SPM and the insulating film HM3 forming the lower layer thereof are removed by etching. By these processes, a concave portion (trench) is formed in the region MMA (see
Subsequently, as shown in
Subsequently, a conductive film 109 to be the memory gate electrode part MG is formed on the insulating films ONO (106, 107, 108). For example, on the insulating films ONO (106, 107, 108), a polysilicon film having a thickness of about 40 nm is deposited as the conductive film 109 by using a CVD method or others.
Subsequently, as shown in
Subsequently, as shown in
Subsequently, the source region MS and the drain region MD are formed in the memory cell region MA, and a source/drain region SD is formed in the peripheral circuit region PA. These regions can be formed as similar to those of the first embodiment.
Subsequently, a metal silicide film SIL is formed on the control gate electrode part CG, the memory gate electrode part MG, the source region MS, the drain region MD, the gate electrode part GE, and the source/drain region SD by using a salicide technique. The metal silicide film SIL can be formed as similar to the first embodiment.
After that, as shown in
By the above-described manufacturing process, the semiconductor device according to the present embodiment can be formed.
In the semiconductor device of the above-described first to fourth embodiments, the memory cell and the peripheral transistor are formed on the fins. However, the memory cell and the peripheral transistor may be formed on a flat active region of a semiconductor substrate.
For example, the region of fins F shown in
The upper layer insulating film 108 forming the insulating film ONO may be prepared as a stacked film. For example, the upper layer insulating film 108 is formed of a stacked film of a silicon oxynitride film formed on the middle layer insulating film 107, a silicon nitride film formed thereon and a silicon oxide film formed thereon. In other words, the upper layer insulating film 108 is formed of a stacked film obtained by stacking the silicon oxynitride film, the silicon nitride film and the silicon oxide film from below.
The second embodiment may have a configuration in which the hollow portion (concave portion, undercut portion) of the silicon germanium film 105a below the end portion of the polysilicon film on the memory gate electrode part MG side is formed to be larger so that parts of each of the insulating films ONO (106, 107, 108) and the memory gate electrode part MG comes into the hollow portion. The part of the insulating film ONO coming into the hollow portion is indicated by a reference symbol “ONOa”, and the part of the memory gate electrode part MG coming into the hollow portion is indicated by a reference symbol “MGa”.
In this manner, the film thickness of the end portion of the control gate insulating film CGI on the memory gate electrode part MG side is made larger, so that the retention property (charge holding property) of the memory cell can be improved as described in the first embodiment.
Moreover, by the part MGa of the memory gate electrode part MG coming into the hollow portion, a resistance of the channel below the control gate electrode part CG can be reduced at the time of reading, so that the reading property can be improved.
In the foregoing, the invention made by the present inventors has been concretely described based on the embodiments. However, it is needless to say that the present invention is not limited to the foregoing embodiments and various modifications and alterations can be made within the scope of the present invention.
For example, the memory cell of the second or fourth embodiment and the peripheral transistor of the third embodiment may be combined with each other.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2015-169379 | Aug 2015 | JP | national |
