JP4006566B2 - Semiconductor device, memory system and electronic device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a semiconductor device such as a static random access memory (SRAM), a memory system including the semiconductor device, and an electronic apparatus.
[0002]
[Background Art and Problems to be Solved by the Invention]
An SRAM, which is a kind of semiconductor memory device, has the characteristics that the system can be simplified because the refresh operation is not required and the power consumption is low. For this reason, SRAM is used suitably for the memory of electronic devices, such as a mobile phone, for example.
[0003]
An object of the present invention is to provide a semiconductor device capable of increasing the stability of a memory cell, a memory system including the same, and an electronic apparatus.
[0004]
[Means for Solving the Problems]
(1) A semiconductor device according to the present invention includes:
A semiconductor device comprising a memory cell including a first load transistor, a second load transistor, a first drive transistor, a second drive transistor, a first transfer transistor and a second transfer transistor,
A first active region extending in a first direction and in which the first and second load transistors are formed;
A second active region extending in a first direction and formed with the first and second drive transistors and the first and second transfer transistors;
Extending in the second direction and located in the first conductive layer, which is an upper layer of the first and second active regions, and located intersecting the second active region in plan view, And a first word line including a gate electrode of the first transfer transistor;
Extending in the second direction, located in the first conductive layer, and intersecting the second active region in plan view, and the gate electrode of the second transfer transistor Including a second word line;
Extending in a second direction, located in the first conductive layer, intersecting the first and second active regions in plan view, and the first word line A first gate-gate electrode layer positioned between the second word line and including gate electrodes of the first load transistor and the first drive transistor;
Extending in a second direction, located in the first conductive layer, intersecting the first and second active regions in plan view, and the first word line A second gate-gate electrode layer positioned between the second word line and including gate electrodes of the second load transistor and the second drive transistor;
With
The gate lengths of the first and second transfer transistors are larger than the gate lengths of the first and second drive transistors, and / or the gate widths of the first and second drive transistors are the first and second transfer transistors. It is larger than the gate width of the transistor.
[0005]
Here, the “active region” refers to an element formation region defined by an element isolation region, and specifically, a region where an impurity diffusion layer is formed and a region where a channel under a gate electrode is formed. including.
[0006]
According to the present invention, the gate lengths of the first and second transfer transistors are larger than the gate lengths of the first and second drive transistors, and / or the gate widths of the first and second drive transistors are the first and second. It is larger than the gate width of the two transfer transistors. For this reason, since the beta ratio of the drive transistor and the transfer transistor can be increased, the stability of the memory cell can be increased.
[0007]
(2) The semiconductor device according to the present invention can be as follows.
[0008]
The second active region includes a drive transistor formation region in which the first and second drive transistors are formed, and a transfer transistor formation region in which the first and second transfer transistors are formed,
The width of the drive transistor formation region is larger than the width of the transfer transistor formation region.
[0009]
According to the present invention, the gate widths of the first and second drive transistors can be made larger than the gate widths of the first and second transfer transistors.
[0010]
(3) The semiconductor device according to the present invention can be as follows.
[0011]
The widths of the first and second word lines are larger than the widths of the first and second gate-gate electrode layers.
[0012]
According to the present invention, the gate lengths of the first and second transfer transistors can be made larger than the gate lengths of the first and second drive transistors.
[0013]
(4) The semiconductor device according to the present invention can be as follows.
[0014]
It extends in the second direction and is located in the second conductive layer that is the upper layer of the first conductive layer, and connects the drain of the first load transistor and the drain of the first drive transistor. A first drain-drain connection layer;
A second drain-drain connection layer extending in a second direction, located in the second conductive layer, and connecting a drain of the second load transistor and a drain of the second driving transistor;
A first drain-gate connection layer located in a third layer conductive layer, which is an upper layer of the second layer conductive layer, and connecting the first drain-drain connection layer and the second gate-gate electrode layer When,
A second drain-gate connection layer located in the third conductive layer and connecting the second drain-drain connection layer and the first gate-gate electrode layer;
Is provided.
[0015]
A flip-flop is configured by making a predetermined connection to the first load transistor, the second load transistor, the first drive transistor, and the second drive transistor. According to the present invention, a flip-flop is configured using three conductive layers (gate-gate electrode layer, drain-drain connection layer, drain-gate connection layer). For this reason, the pattern of each layer can be simplified (for example, a substantially linear pattern) compared with the case where a flip-flop is formed using two conductive layers. As described above, according to the present invention, the pattern of each layer can be simplified. For example, the memory cell size is 2.5 μm. ² The following fine semiconductor device can be obtained.
[0016]
(5) The semiconductor device according to the present invention can be as follows.
[0017]
A power supply line having a pattern extending in a first direction and located in the second conductive layer and connected to the sources of the first and second load transistors;
A local wiring layer for a ground line that has a pattern extending in a second direction, is located in the second layer conductive layer, and is connected to the sources of the first and second drive transistors;
A bit line contact pad layer located in the second conductive layer and connected to the first transfer transistor;
A bit line contact pad layer located in the second conductive layer and connected to the second transfer transistor;
A ground line having a pattern extending in the second direction and located in a fourth layer conductive layer that is an upper layer of the third layer conductive layer, and connected to the local wiring layer for the ground line;
A main word line having a pattern extending in the second direction and located in the fourth conductive layer;
A bit line local wiring layer having a pattern extending in the second direction and located in the fourth conductive layer and connected to the bit line contact pad layer;
A / bit line local wiring layer having a pattern extending in the second direction and located in the fourth conductive layer and connected to the / bit line contact pad layer;
A bit line having a pattern extending in the first direction and located in a fifth conductive layer, which is an upper layer of the fourth conductive layer, and connected to the local wiring layer for bit lines;
A / bit line having a pattern extending in the first direction and located in the fifth conductive layer and connected to the / bit line local wiring layer;
Is provided.
[0018]
According to the present invention, the power supply line, the ground line, the main word line, the bit line, and the / bit line can be arranged in a balanced manner. The local wiring layer for the ground line is used for connection between the source of the first and second drive transistors and the ground line. The bit line contact pad layer and the bit line local wiring layer are used for connection between the bit line and the first transfer transistor. The / bit line contact pad layer and the / bit line local wiring layer are used to connect the / bit line and the second transfer transistor. The power line is, for example, V _DD Wiring. The ground wire is, for example, V _SS Wiring. When the main word line is provided, the above word line becomes a sub word line.
[0019]
(6) The semiconductor device according to the present invention can be as follows.
[0020]
The first and second active regions, the first and second gate-gate electrode layers, and the first and second word lines have a substantially linear pattern.
[0021]
These elements constitute the bulk layer. According to the present invention, since these elements have a substantially linear pattern, that is, a simple pattern, the bulk layer can be miniaturized.
[0022]
(7) The semiconductor device according to the present invention can be as follows.
[0023]
The size of the memory cell is 2.5 μm ² It is as follows.
[0024]
(8) A memory system according to the present invention includes the semiconductor device according to any one of (1) to (7).
[0025]
(9) An electronic apparatus according to the present invention includes the semiconductor device according to any one of (1) to (7).
[0026]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described. In this embodiment, the semiconductor device according to the present invention is applied to an SRAM. First, the outline of the structure of the SRAM according to the present embodiment will be described, and then the details of the structure will be described.
[0027]
[Outline of SRAM structure]
FIG. 1 is an equivalent circuit diagram of the SRAM according to the present embodiment. The SRAM according to this embodiment is a type in which one memory cell is configured by six MOS field effect transistors. That is, the n-channel type driving transistor Q _Three And p-channel load transistor Q _Five Thus, one CMOS inverter is configured. Further, the n-channel type driving transistor Q _Four And p-channel load transistor Q ₆ Thus, one CMOS inverter is configured. A flip-flop is formed by cross-coupling the two CMOS inverters. The flip-flop and the n-channel transfer transistor Q ₁ , Q ₂ Thus, one memory cell is configured.
[0028]
As shown in FIGS. 2 to 7, the SRAM memory cell according to the present embodiment has a structure having five conductive layers above the field. Hereinafter, FIGS. 2 to 7 will be briefly described with reference to FIG. Note that the symbol R in these drawings indicates a formation region of one memory cell.
[0029]
FIG. 2 is a plan view showing the field, and includes active regions 11 and 13 having a pattern extending substantially linearly in the Y direction. FIG. 3 is a plan view showing the first conductive layer, and includes gate-gate electrode layers 21a and 21b and sub word lines 23a and 23b having a pattern extending substantially linearly in the X direction. The gate-gate electrode layer 21a is composed of the drive transistor Q _Three And load transistor Q _Five The gate-gate electrode layer 21b includes the drive transistor Q. _Four And load transistor Q ₆ The sub-word line 23a includes a transfer transistor Q. ₁ The sub-word line 23b includes a transfer transistor Q. ₂ Of the gate electrode. FIG. 4 is a plan view showing the second conductive layer, a drain-drain connection layer 31a having a pattern extending substantially linearly in the X direction, a drain-drain connection layer 31b having an L-shaped pattern, and a Y direction. V having a pattern extending substantially linearly _DD Including the wiring 33 and the like. FIG. 5 is a plan view showing the third conductive layer, and includes a drain-gate connection layer 41a having an L-shaped pattern and a drain-gate connection layer 41b having a U-shaped pattern. FIG. 6 is a plan view showing the fourth conductive layer, and includes a BL local wiring layer 51a, a / BL local wiring layer 51b, a main word line 53, V having a pattern extending substantially linearly in the X direction. _SS Wiring 55 is included. FIG. 7 is a plan view showing the fifth conductive layer, and includes bit lines 61a and / bit lines 61b having a pattern extending substantially linearly in the Y direction.
[0030]
[Details of SRAM structure]
Details of the structure of the SRAM according to the present embodiment will be described in order from the lower layer with reference to FIGS. FIG. 8 is a plan view showing the field and the first conductive layer, FIG. 9 is a plan view showing the field, the first conductive layer, and the second conductive layer, and FIG. 10 is the second conductive layer and the first conductive layer. FIG. 11 is a plan view showing a third conductive layer, FIG. 11 is a plan view showing a first conductive layer and a third conductive layer, and FIG. 12 is a plan view showing a second conductive layer and a fourth conductive layer. 13 is a plan view showing the fourth conductive layer and the fifth conductive layer, FIG. 14 is a cross-sectional view taken along the line A1-A2 of FIGS. 2 to 13, and FIG. FIG. 14 is a cross-sectional view taken along line B1-B2 of FIG.
[0031]
{Field, first conductive layer}
First, the fields will be described. As shown in FIG. 2, the field has active regions 11 and 13 and an element isolation region 19. The active regions 11 and 13 are formed on the surface of the silicon substrate.
[0032]
The active region 11 has a pattern extending substantially linearly in the Y direction. The active region 11 extends to the formation region of another memory cell positioned above and below in FIG. 2 with respect to the formation region R of the memory cell. The active region 11 has a drive transistor Q _Three , Q _Four Drive transistor formation region 11a, which is a region in which a transistor is formed, and a transfer transistor Q ₁ , Q ₂ And a transfer transistor formation region 11b, which is a region in which is formed. Width W of drive transistor formation region 11a _11a Is the width W of the transfer transistor formation region 11b. _11b Greater than. Width W _11a Is, for example, 0.22 to 0.33 μm and the width W _11b Is, for example, 0.16 to 0.20 μm.
[0033]
The active region 13 has a pattern extending substantially linearly in the Y direction, and is formed at a distance from the active region 11. Both ends of the active region 13 stop extending in the memory cell formation region R. The active region 13 includes a load transistor Q _Five , Q ₆ Is formed. The length of the active region 13 is, for example, 0.16 to 0.20 μm, and the width is, for example, 0.16 to 0.20 μm.
[0034]
The active region 11 and the active region 13 are separated from each other by an element isolation region 19 (depth, for example, 0.35 to 0.45 μm). As the element isolation region 19, for example, there is STI (shallow trench isolation). The length in the X direction of the memory cell formation region R is, for example, 1.0 to 1.4 μm, and the length in the Y direction is, for example, 1.6 to 2.0 μm.
[0035]
The A1-A2 cross section and B1-B2 cross section of the field shown in FIG. 2 are as shown in FIGS. 14 and 15, respectively. These cross sections show a p-well 12, an n-well 14 and the like formed in the silicon substrate.
[0036]
Next, the first conductive layer located in the upper layer of the field will be described with reference to FIGS. A pair of gate-gate electrode layers 21a and 21b are arranged in parallel in the formation region R of one memory cell. The gate-gate electrode layers 21a and 21b intersect the active regions 11 and 13 when viewed in plan. The gate-gate electrode layer 21a is composed of the drive transistor Q _Three And load transistor Q _Five These gate electrodes are connected to each other. The gate-gate electrode layer 21b is connected to the driving transistor Q. _Four And load transistor Q ₆ These gate electrodes are connected to each other.
[0037]
The sub word lines 23a and 23b are located apart from the active region 13 when viewed in plan, and are positioned so as to intersect with the active region 11 when viewed in plan. Gate-gate electrode layers 21a and 21b are located between the sub word line 23a and the sub word line 23b. The sub word line 23a is connected to the transfer transistor Q. ₁ The sub word line 23b is connected to the transfer transistor Q. ₂ It becomes a gate electrode.
[0038]
Width W of the sub word lines 23a and 23b _23a , W _23b Is the width W of the gate-gate electrode layers 21a, 21b. _21a , W _21b Bigger than. Width W _23a , W _23b Is, for example, 0.14 to 0.17 μm and width W _21a , W _21b Is, for example, 0.12 to 0.15 μm.
[0039]
The gate-gate electrode layers 21a and 21b and the sub word lines 23a and 23b have, for example, a structure in which a silicide layer is formed on a polysilicon layer.
[0040]
The A1-A2 cross section and B1-B2 cross section of the first conductive layer shown in FIGS. 3 and 8 are as shown in FIGS. 14 and 15, respectively. In these cross sections, the sub-word line 23a and the gate-gate electrode layer 21a appear.
[0041]
Next, n formed in the active region 11 ⁺ The type impurity regions 15a, 15b, 15c, 15d, and 15e will be described with reference to FIG. N in order to sandwich the sub word line 23a in plan view. ⁺ Type impurity regions 15a and n ⁺ N-type impurity region 15b and n-type electrode region 21a so as to sandwich n-type impurity region 15b. ⁺ Type impurity regions 15b and n ⁺ N-type impurity region 15c is located and n-side so as to sandwich gate-gate electrode layer 21b ⁺ Type impurity regions 15c and n ⁺ N type impurity region 15d is located, and n is arranged so as to sandwich sub word line 23b. ⁺ Type impurity regions 15d and n ⁺ A type impurity region 15e is located.
[0042]
n ⁺ The type impurity region 15a is formed by the transfer transistor Q ₁ Source or drain. n ⁺ The type impurity region 15b is formed by the transfer transistor Q ₁ Source or drain, driving transistor Q _Three It becomes the drain of. n ⁺ The type impurity region 15c is connected to the driving transistor Q. _Three , Q _Four Become a common source. n ⁺ The type impurity region 15d is connected to the driving transistor Q. _Four Drain, transfer transistor Q ₂ Source or drain. n ⁺ The type impurity region 15e is formed by the transfer transistor Q ₂ Source or drain.
[0043]
Next, p formed in the active region 13 is formed. ⁺ The type impurity regions 17a, 17b, and 17c will be described with reference to FIG. P in such a way as to sandwich the gate-gate electrode layer 21a in plan view. ⁺ Type impurity regions 17a and p ⁺ P-type impurity region 17b is located and p-type so as to sandwich gate-gate electrode layer 21b. ⁺ Type impurity regions 17b and p ⁺ A type impurity region 17c is located. p ⁺ The type impurity region 17a is connected to the load transistor Q _Five The drain of p ⁺ The type impurity region 17c is connected to the load transistor Q ₆ The drain of p ⁺ The type impurity region 17b is connected to the load transistor Q _Five , Q ₆ Become a common source. As shown in FIG. ⁺ Type impurity regions 15a, 15b, p ⁺ A type impurity region 17a appears.
[0044]
As shown in FIGS. 14 and 15, an interlayer insulating layer 71 such as a silicon oxide layer is formed so as to cover the field and the first conductive layer. The interlayer insulating layer 71 is planarized by CMP.
[0045]
{Second layer conductive layer}
The second conductive layer will be described with reference to FIGS. The second conductive layer is located above the first conductive layer. The second conductive layer includes drain-drain connection layers 31a, 31b, V _DD Wiring 33, bit line contact pad layer 35a, / bit line contact pad layer 35b, and ground line local wiring layer 37 are included. The second conductive layer is connected to the field n via a contact conductive portion 73 (hereinafter referred to as field / second layer-contact conductive portion 73) which is a conductive portion connecting the second conductive layer and the field. ⁺ Type impurity region and p ⁺ Connected to the type impurity region.
[0046]
Between the drain-drain connection layer 31a and the drain-drain connection layer 31b, the drain-drain connection layers 31a, 31b are positioned so that the gate-gate electrode layers 21a, 21b are positioned in plan view. . The drain-drain connection layer 31a has n ⁺ Type impurity region 15b (drain) and p ⁺ It is located above the type impurity region 17a (drain). The end 31a1 of the drain-drain connection layer 31a is connected to the n-layer via the field / second layer-contact conductive portion 73. ⁺ The end portion 31a2 of the drain-drain connection layer 31a is connected to the p-type impurity region 15b (drain) via the field / second layer-contact conductive portion 73 and p ⁺ It is connected to the type impurity region 17a (drain). The drain-drain connection layer 31b has n ⁺ Type impurity region 15d (drain) and p ⁺ It is located above the type impurity region 17c (drain). The end 31b1 of the drain-drain connection layer 31b is connected to the n-layer via the field / second layer-contact conductive portion 73. ⁺ The L-shaped corner 31b3 of the drain-drain connection layer 31b is connected to the p-type impurity region 15d (drain) via the field / second layer-contact conductive portion 73, and p ⁺ It is connected to the type impurity region 17c (drain). The width of the drain-drain connection layers 31a and 31b is, for example, 0.16 to 0.20 μm.
[0047]
V _DD The width of the wiring 33 is, for example, 0.16 to 0.20 μm. V _DD The protrusion 33a of the wiring 33 extends in the X direction, and p ⁺ It is located above the type impurity region 17b (source). The convex portion 33a is connected to p through the field / second layer-contact conductive portion 73. ⁺ It is connected to the type impurity region 17b.
[0048]
The ground wiring local wiring layer 37 has n ⁺ It is located above the type impurity region 15c (source). The local wiring layer 37 for the ground line is connected via the field / second layer-contact conductive portion 73 to n ⁺ It is connected to the type impurity region 15c. The local wiring layer 37 for grounding wire is V _SS Wiring 55 (FIG. 6) and drive transistor Q _Three , Q _Four The source of n ⁺ It functions as a wiring layer for connecting the type impurity region 15c. The local wiring layer 37 for the ground line is shared by the memory cell in the formation region R and the memory cell located on the right side in FIG.
[0049]
Bit line contact pad layer 35a has n ⁺ It is located above the type impurity region 15a. The bit line contact pad layer 35a is connected via the field / second layer-contact conductive portion 73 to n ⁺ It is connected to the type impurity region 15a. Bit line contact pad layer 35a includes bit line 61a (FIG. 7) and transfer transistor Q. ₁ N to become the source and drain of ⁺ It functions as a pad layer for connecting the type impurity region 15a. The bit line contact pad layer 35a is shared by the memory cell in the formation region R and the memory cell located above the formation region R in FIG.
[0050]
/ Bit line contact pad layer 35b has n ⁺ It is located above the type impurity region 15e. / Bit line contact pad layer 35b is connected to n through the field / second layer-contact conductive portion 73. ⁺ It is connected to the type impurity region 15e. / Bit line contact pad layer 35b includes / bit line 61b (FIG. 7) and transfer transistor Q ₂ N to become the source and drain of ⁺ It functions as a pad layer for connecting the type impurity region 15e. The bit line contact pad layer 35b is shared by the memory cell in the formation region R and the memory cell located below in FIG.
[0051]
Next, the cross-sectional structure of the second conductive layer will be described with reference to FIG. The second conductive layer can be composed of, for example, only a refractory metal nitride layer. The thickness of the second conductive layer is, for example, 100 to 200 nm. An example of the refractory metal nitride layer is a titanium nitride layer. Moreover, the following aspect may be sufficient as a 2nd layer conductive layer. 1) It may have a structure in which a refractory metal nitride layer 32 is formed on a metal layer 30 made of a refractory metal. In this case, the metal layer 30 made of a refractory metal serves as an underlay, for example, a titanium layer. Examples of the material for the metal layer of the refractory metal include titanium and tungsten. 2) The structure of the second conductive layer may be composed only of a metal layer of a refractory metal.
[0052]
Next, the cross-sectional structure of the field / second layer-contact conductive portion 73 will be described with reference to FIG. The interlayer insulating layer 71 has n in the field. ⁺ Type impurity region and p ⁺ A plurality of through holes 75 exposing the type impurity region are formed. In these through holes 75, field / second layer-contact conductive portions 73 are embedded. Field / second layer-contact conductive portion 73 includes a plug 77 embedded in through hole 75 and a barrier layer 79 located on the bottom surface and side surface of through hole 75. An example of the material of the plug 77 is tungsten. The barrier layer 79 is preferably composed of a metal layer made of a refractory metal and a refractory metal nitride layer formed on the metal layer. An example of the material for the metal layer made of a refractory metal is titanium. An example of the material of the refractory metal nitride layer is titanium nitride. The diameter of the upper end portion of the through hole 75 is, for example, 0.18 to 0.22 μm, and the diameter of the lower end portion is, for example, 0.14 to 0.18 μm.
[0053]
As shown in FIGS. 14 and 15, an interlayer insulating layer 81 such as a silicon oxide layer is formed so as to cover the second conductive layer. The interlayer insulating layer 81 is planarized by CMP.
[0054]
{Third conductive layer}
The third conductive layer will be described with reference to FIGS. The third conductive layer is located above the second conductive layer. The third conductive layer includes drain-gate connection layers 41a and 41b. The width of the drain-gate connection layers 41a and 41b is, for example, 0.16 to 0.20 μm.
[0055]
The drain-gate connection layer 41a has an L-shaped pattern, and its end 41a1 is located above the end 31a1 of the drain-drain connection layer 31a (FIG. 10). The end 41a1 of the drain-gate connection layer 41a is a contact conductive portion 83 (hereinafter referred to as a second layer / third layer-contact conductive portion 83) which is a conductive portion connecting the third conductive layer and the second conductive layer. To the end 31a1 of the drain-drain connection layer 31a (FIG. 10). The end 41a2 of the drain-gate connection layer 41a is located above the center of the gate-gate electrode layer 21b (FIG. 11). The end 41a2 of the drain-gate connection layer 41a is a contact conductive portion 93 (hereinafter referred to as a first layer / third layer-contact conductive portion 93) which is a conductive portion connecting the third conductive layer and the first conductive layer. And the central portion of the gate-gate electrode layer 21b (FIG. 11).
[0056]
The drain-gate connection layer 41b is U-shaped, and its end 41b1 is located above the end 31b2 of the drain-drain connection layer 31b (FIG. 10). The end portion 41b1 of the drain-gate connection layer 41b is connected to the end portion 31b2 of the drain-drain connection layer 31b through the second layer / third layer-contact conductive portion 83 (FIG. 10). The end 41b2 of the drain-gate connection layer 41b is located above the center of the gate-gate electrode layer 21a (FIG. 11). The end portion 41b2 of the drain-gate connection layer 41b is connected to the central portion of the gate-gate electrode layer 21a via the first layer / third layer-contact conductive portion 93 (FIG. 11).
[0057]
Next, the cross-sectional structure of the third conductive layer will be described with reference to FIGS. The third conductive layer can have the structure described in the second conductive layer.
[0058]
Next, the sectional structure of the second layer / third layer-contact conductive portion 83 will be described with reference to FIG. Second and third layer-contact conductive portions 83 are buried in the through holes 85 that penetrate the interlayer insulating layer 81. The second layer / third layer-contact conductive portion 83 can have the structure described in the field / second layer-contact conductive portion 73.
[0059]
Next, the cross-sectional structure of the first layer / third layer-contact conductive portion 93 will be described with reference to FIG. The first layer / third layer-contact conductive portion 93 is buried in a through hole 95 penetrating the two interlayer insulating layers 71 and 81. In this cross section, the first layer / third layer-contact conductive portion 93 is connected to the gate-gate electrode layer 21a. The first layer / third layer-contact conductive portion 93 can have the structure described in the field / second layer-contact conductive portion 73. The diameter of the upper end portion of the through hole 95 is, for example, 0.18 to 0.22 μm, and the diameter of the lower end portion is, for example, 0.14 to 0.18 μm.
[0060]
As shown in FIGS. 14 and 15, an interlayer insulating layer 101 such as a silicon oxide layer is formed so as to cover the third conductive layer. The interlayer insulating layer 101 is planarized by CMP.
[0061]
{Fourth conductive layer}
The fourth conductive layer will be described with reference to FIGS. The fourth conductive layer is located above the third conductive layer. The fourth conductive layer includes a bit line local wiring layer 51a, a / bit line local wiring layer 51b, a main word line 53, V, and a pattern extending substantially linearly in the X direction. _SS Wiring 55 is included. Between the bit line local wiring layer 51a and the bit line local wiring layer 51b, the main word line 53, V _SS The wiring 55 is located.
[0062]
V _SS The wiring 55 is located above the ground wiring local wiring layer 37 and is a contact conductive portion 113 (hereinafter referred to as a second layer / fourth layer) that is a conductive portion connecting the fourth conductive layer and the second conductive layer. -It is connected to the local wiring layer 37 for ground line through the contact conductive portion 113 (FIG. 12). V _SS The width of the wiring 55 is, for example, 0.4 to 1.0 μm.
[0063]
The main word line 53 is located above the drain-drain connection layer 31a. By main word line 53, sub word lines 23a and 23b (FIG. 8) are activated and deactivated. The width of the main word line 53 is, for example, 0.18 to 0.24 μm. In the present embodiment, the word line has a structure including a sub word line and a main word line, but a structure in which the main word line is not provided may be used.
[0064]
The bit line local wiring layer 51a is located above the bit line contact pad layer 35a. The bit line local wiring layer 51a includes a bit line 61a (FIG. 7) and a transfer transistor Q. ₁ N to become the source and drain of ⁺ It functions as a wiring layer for connecting the type impurity region 15a (FIG. 8). The end portion 51a1 of the local wiring layer 51a for the bit line is connected to the bit line contact pad layer 35a via the second layer / fourth layer-contact conductive portion 113. The bit line local wiring layer 51a is shared by the memory cell in the formation region R and the memory cell located above the formation region R in FIG. The width of the bit line local wiring layer 51a is, for example, 0.2 to 0.4 μm.
[0065]
The / bit line local wiring layer 51b is located above the / bit line contact pad layer 35b. / Bit line local wiring layer 51b includes bit line 61b (FIG. 7) and transfer transistor Q. ₂ N to become the source and drain of ⁺ It functions as a wiring layer for connecting the type impurity region 15e (FIG. 8). The end 51b1 of the / bit line local wiring layer 51b is connected to the / bit line contact pad layer 35b via the second layer / fourth layer-contact conductive portion 113. / Bit line local interconnection layer 51b is shared by memory cells in formation region R and memory cells located below in FIG. / The width of the bit line local wiring layer 51b is, for example, 0.2 to 0.4 μm.
[0066]
Next, the cross-sectional structure of the fourth conductive layer will be described with reference to FIG. The fourth conductive layer has, for example, a structure in which a refractory metal nitride layer 52, a metal layer 54, and a refractory metal nitride layer 56 are stacked in this order from the bottom. Specific examples of each layer are as follows. An example of the refractory metal nitride layer 52 is a titanium nitride layer. Examples of the metal layer 54 include an aluminum layer, a copper layer, or an alloy layer thereof. An example of the refractory metal nitride layer 56 is a titanium nitride layer. Moreover, the following aspect may be sufficient as a 4th layer conductive layer. 1) An embodiment composed only of a refractory metal nitride layer. 2) An embodiment composed only of a metal layer.
[0067]
A hard mask layer 59 made of a silicon oxide layer is formed on the fourth conductive layer. The fourth conductive layer is patterned using the hard mask layer 59 as a mask. This is because it is difficult to pattern the fourth conductive layer using only the resist as a mask due to miniaturization of the memory cell.
[0068]
Next, the cross-sectional structure of the second layer / fourth layer-contact conductive portion 113 will be described with reference to FIG. The second layer / fourth layer-contact conductive portion 113 is buried in a through hole 115 penetrating the two interlayer insulating layers 81 and 101. In this section, the second layer / fourth layer-contact conductive portion 113 connects the bit line contact pad layer 35a and the bit line local wiring layer 51a. The second layer / fourth layer-contact conductive portion 113 can have the structure described in the field / second layer-contact conductive portion 73. The diameter of the upper end portion of the through hole 115 is, for example, 0.18 to 0.24 μm, and the diameter of the lower end portion is, for example, 0.14 to 0.18 μm.
[0069]
As shown in FIGS. 14 and 15, an interlayer insulating layer 121 such as a silicon oxide layer is formed so as to cover the fourth conductive layer. The interlayer insulating layer 121 is planarized by CMP.
[0070]
{Fifth conductive layer}
The fifth conductive layer will be described with reference to FIGS. The fifth conductive layer is located above the fourth conductive layer. The fifth conductive layer includes bit lines 61a and / bit lines 61b having a pattern extending substantially linearly in the Y direction. / A signal complementary to the signal flowing through the bit line 61a flows through the bit line 61b. The width of the bit line 61a and / bit line 61b is, for example, 0.20 to 0.26 μm.
[0071]
The bit line 61a is connected to a bit via a contact conductive portion 133 (hereinafter referred to as a fourth layer / fifth layer-contact conductive portion 133) which is a conductive portion connecting the fifth conductive layer and the fourth conductive layer. It is connected to the end 51a1 of the local wiring wiring layer 51a. The / bit line 61b is connected to the end portion 51b2 of the / bit line local wiring layer 51b via the fourth layer / fifth layer-contact conductive portion 133.
[0072]
Next, the cross-sectional structure of the fifth conductive layer will be described with reference to FIGS. The fifth conductive layer can have the structure described in the fourth conductive layer. A hard mask layer 69 made of a silicon oxide layer is formed on the fifth conductive layer. The reason for forming the hard mask layer 69 is the same as that of the hard mask layer 59.
[0073]
The above is the detailed structure of the SRAM according to the present embodiment.
[0074]
[Main effects of SRAM according to this embodiment]
The main effects of the SRAM according to the present embodiment are the following two.
[0075]
{Effect 1}
According to the present invention, the stability of the memory cell can be increased. The reason is as follows. It is generally known that increasing the beta ratio between the drive transistor and the transfer transistor increases the stability of the memory cell. The beta ratio is expressed by (capacity of drive transistor) / (capacity of transfer transistor). Therefore, if the capability of the drive transistor is increased and the capability of the transfer transistor is decreased, the beta ratio increases.
[0076]
The capability of the drive transistor is (gate width W of drive transistor _D ) / (Gate length L of driving transistor) _D ). Therefore, the gate width W of the driving transistor _D And the gate length L of the driving transistor _D If the value is reduced, the capability of the driving transistor can be increased.
[0077]
The capacity of the transfer transistor is (the gate width W of the transfer transistor _T ) / (Transfer transistor gate length L _T ). Therefore, the gate width W of the transfer transistor _T And the gate length L of the transfer transistor _T If is increased, the capacity of the transfer transistor can be reduced.
[0078]
That is, in terms of the gate width, the gate width W of the driving transistor _D And the gate width W of the transfer transistor _T Decreasing the value increases the beta ratio. In terms of gate length, the transfer transistor gate length L _T And the gate length L of the driving transistor _D Decreasing the value increases the beta ratio.
[0079]
In the present embodiment, as shown in FIG. 8, the width W of the drive transistor formation region 11a. _11a The drive transistor Q represented by _Three , Q _Four Gate width W _D Is the width W of the transfer transistor formation region 11b. _11b Transfer transistor Q represented by ₁ , Q ₂ Gate width W _T Bigger than. Further, the width W of the sub word lines 23a and 23b. _23a , W _23b Transfer transistor Q represented by ₁ , Q ₂ Gate length L _T Is the width W of the gate-gate electrode layers 21a, 21b. _21a , W _21b The drive transistor Q represented by _Three , Q _Four Gate length L _D Bigger than. Therefore, according to the present embodiment, the beta ratio can be increased, and thereby the stability of the memory cell can be increased.
[0080]
In this embodiment, attention is paid to both the gate length and the gate width, but only one of them may be noted. That is, paying attention to the gate length, the transfer transistor Q ₁ , Q ₂ Gate length L _T Drive transistor Q _Three , Q _Four Gate length L _D You can just make it bigger. Focusing on the gate width, the driving transistor Q _Three , Q _Four Gate width W _D Transfer transistor Q ₁ , Q ₂ Gate width W _T You can just make it bigger.
[0081]
{Effect 2}
According to this embodiment, the SRAM memory cell can be reduced in size. Details will be described below. In this embodiment, information is stored in a flip-flop of a memory cell. The flip-flop connects the input terminal (gate electrode) of one inverter to the output terminal (drain) of the other inverter, and the input terminal (gate electrode) of the other inverter to the output terminal (drain) of one inverter. Configured by connecting. That is, the flip-flop is a cross-coupled connection between the first inverter and the second inverter. When a flip-flop is configured by using two conductive layers, for example, a drain-drain connection layer that connects the drains of the inverter and a drain-gate connection layer that connects the gate of the inverter and the drain of the inverter are combined. By using two conductive layers, a cross-couple connection can be made.
[0082]
However, according to this structure, the conductive layer is formed over a region where the drain of one inverter is located, a region where the gate of the other inverter is located, and a region connecting them. Therefore, the conductive layer has a pattern having three end portions (for example, a pattern having a branch portion such as a T shape or an h shape) or a spiral pattern in which the arm portions enter each other. In addition, as a T-shaped pattern, it is disclosed by FIG. 1 of Unexamined-Japanese-Patent No. 10-41409, for example. The h-shaped pattern is disclosed in, for example, M.Ishida, et.al., IEDM Tech.Digest (1998), FIG. The spiral pattern is disclosed in, for example, M.Ishida, et.al., IEDM Tech.Digest (1998), FIG. When such a complicated pattern is miniaturized, it is difficult to accurately reproduce the shape in the photoetching process, so that a desired pattern cannot be obtained, which hinders downsizing of the memory cell size.
[0083]
According to the present embodiment, as shown in FIGS. 3, 4, and 5, the gate-gate electrode layer (21a, 21b) that becomes the gate of the CMOS inverter, and the drain-drain connection layer that connects the drains of the CMOS inverter. (31a, 31b), drain-gate connection layers (41a, 41b) for connecting the gate of one CMOS inverter and the drain of the other CMOS inverter are formed in different layers. Thus, in this embodiment, since the flip-flop is configured using three conductive layers, the pattern of each layer is simplified compared to the case where the flip-flop is configured using two conductive layers (for example, , Almost linear). Therefore, according to the present embodiment, the pattern of each layer can be simplified. For example, in the 0.12 μm generation, the memory cell size is 2.5 μm. ² The following fine SRAM can be obtained.
[0084]
[Application example of SRAM to electronic equipment]
The SRAM according to the present embodiment can be applied to an electronic device such as a portable device, for example. FIG. 16 is a block diagram of a part of a mobile phone system. The CPU, SRAM, and DRAM are connected to each other by a bus line. Further, the CPU is connected to a keyboard and an LCD driver by a bus line. The LCD driver is connected to the liquid crystal display unit by a bus line. A CPU, SRAM, and DRAM constitute a memory system.
[0085]
FIG. 17 is a perspective view of a mobile phone 600 including the mobile phone system shown in FIG. The cellular phone 600 includes a main body 610 including a keyboard 612, a liquid crystal display 614, a receiver 616 and an antenna 618, and a lid 620 including a transmitter 622.
[Brief description of the drawings]
FIG. 1 is an equivalent circuit diagram of an SRAM according to an embodiment.
FIG. 2 is a plan view showing a field of the SRAM memory cell array according to the embodiment;
FIG. 3 is a plan view showing a first conductive layer of the SRAM memory cell array according to the embodiment;
FIG. 4 is a plan view showing a second conductive layer of the SRAM memory cell array according to the embodiment;
FIG. 5 is a plan view showing a third conductive layer of the SRAM memory cell array according to the embodiment;
6 is a plan view showing a fourth conductive layer of the SRAM memory cell array according to the embodiment; FIG.
FIG. 7 is a plan view showing a fifth conductive layer of the SRAM memory cell array according to the embodiment;
FIG. 8 is a plan view showing a field and a first conductive layer of the SRAM memory cell array according to the embodiment;
FIG. 9 is a plan view showing a field, a first conductive layer, and a second conductive layer of the SRAM memory cell array according to the embodiment;
FIG. 10 is a plan view showing a second conductive layer and a third conductive layer of the SRAM memory cell array according to the embodiment;
FIG. 11 is a plan view showing a first conductive layer and a third conductive layer of the SRAM memory cell array according to the embodiment;
FIG. 12 is a plan view showing a second conductive layer and a fourth conductive layer of the SRAM memory cell array according to the embodiment;
FIG. 13 is a plan view showing a fourth conductive layer and a fifth conductive layer of the SRAM memory cell array according to the embodiment;
14 is a cross-sectional view taken along line A1-A2 of FIGS.
15 is a cross-sectional view taken along line B1-B2 of FIGS.
FIG. 16 is a block diagram of a part of a mobile phone system including the SRAM according to the embodiment;
17 is a perspective view of a mobile phone including the mobile phone system shown in FIG.
[Explanation of symbols]
11 Active region
11a Drive transistor formation region
11b Transfer transistor formation region
12 p-well
13 Active region
14 n-well
15a, 15b, 15c, 15d, 15en ⁺ Type impurity region
17a, 17b, 17cp ⁺ Type impurity region
19 Element isolation region
21a, 21b Gate-gate electrode layer
23a, 23b Sub word line
30 Metal layer made of refractory metal
31a, 31b Drain-drain connection layer
31a1, 31a2, 31b1, 31b2 end
31b3 L-shaped corner
32 Nitride layer of refractory metal
33 V _DD wiring
33a Convex
35a Bit line contact pad layer
35b / bit line contact pad layer
37 Local wiring layer for ground wire
40 Metal layer made of refractory metal
41a, 41b Drain-gate connection layer
41a1, 41a2, 41b1, 41b2 end
42 Nitride layer of refractory metal
51a Local wiring layer for bit lines
51a1 end
51b / Local wiring layer for bit line
51b1 51b2 end
52 Nitride layer of refractory metal
53 Main word line
54 Metal layer
55 V _SS wiring
56 Nitride layer of refractory metal
59 Hard Mask
61a bit line
61b / bit line
62 Nitride layer of refractory metal
64 metal layers
66 High melting point metal nitride layer
69 hard mask
71 Interlayer insulation layer
73 Field, second layer-contact conductive part
75 Through hole
77 plug
79 Nitride layer of refractory metal
81 Interlayer insulation layer
83 2nd and 3rd layers-Contact conductive part
85 Through hole
87 plug
89 Refractory metal nitride layer
93 1st and 3rd layers-Contact conductive part
95 Through hole
97 plug
99 Nitride layer of refractory metal
101 Interlayer insulation layer
113 2nd and 4th layer-Contact conductive part
115 through hole
117 plug
119 Nitride layer of refractory metal
121 Interlayer insulation layer
133 4th layer, 5th layer-contact conductive part
R formation region of one memory cell

Claims (7)

A semiconductor device comprising a memory cell including a first load transistor, a second load transistor, a first drive transistor, a second drive transistor, a first transfer transistor and a second transfer transistor,
A first active region extending in a first direction and in which the first and second load transistors are formed;
A second active region extending in a first direction and formed with the first and second drive transistors and the first and second transfer transistors;
Extending in the second direction and located in the first conductive layer, which is an upper layer of the first and second active regions, and located intersecting the second active region in plan view, And a first word line including a gate electrode of the first transfer transistor;
Extending in the second direction, located in the first conductive layer, and intersecting the second active region in plan view, and the gate electrode of the second transfer transistor Including a second word line;
Extending in a second direction, located in the first conductive layer, intersecting the first and second active regions in plan view, and the first word line A first gate-gate electrode layer positioned between the second word line and including gate electrodes of the first load transistor and the first drive transistor;
Extending in a second direction, located in the first conductive layer, intersecting the first and second active regions in plan view, and the first word line A second gate-gate electrode layer positioned between the second word line and including gate electrodes of the second load transistor and the second drive transistor;
It extends in the second direction and is located in the second conductive layer, which is an upper layer of the first conductive layer, and connects the drain of the first load transistor and the drain of the first drive transistor. A first drain - drain connection layer;
A second drain - drain connection layer extending in a second direction, located in the second conductive layer, and connecting a drain of the second load transistor and a drain of the second driving transistor ;
A first drain - gate connection layer located in a third layer conductive layer, which is an upper layer of the second layer conductive layer, and connecting the first drain - drain connection layer and the second gate - gate electrode layer When,
A second drain - gate connection layer located in the third conductive layer and connecting the second drain - drain connection layer and the first gate - gate electrode layer ;
A power supply line having a pattern extending in a first direction and located in the second conductive layer and connected to the sources of the first and second load transistors;
A local wiring layer for a ground line that has a pattern extending in a second direction, is located in the second layer conductive layer, and is connected to the sources of the first and second drive transistors;
A bit line contact pad layer located in the second conductive layer and connected to the first transfer transistor;
A bit line contact pad layer located in the second conductive layer and connected to the second transfer transistor;
A ground line having a pattern extending in the second direction and located in the fourth conductive layer, which is an upper layer of the third conductive layer, and connected to the local wiring layer for the ground line;
A main word line having a pattern extending in the second direction and located in the fourth conductive layer;
A bit line local wiring layer having a pattern extending in the second direction and located in the fourth conductive layer and connected to the bit line contact pad layer;
A / bit line local wiring layer having a pattern extending in the second direction and located in the fourth conductive layer and connected to the / bit line contact pad layer;
A bit line having a pattern extending in the first direction and located in a fifth conductive layer , which is an upper layer of the fourth conductive layer, and connected to the local wiring layer for bit lines;
A / bit line having a pattern extending in the first direction and located in the fifth conductive layer and connected to the / bit line local wiring layer ;
The gate lengths of the first and second transfer transistors are larger than the gate lengths of the first and second drive transistors, and / or the gate widths of the first and second drive transistors are the first and second transfer transistors. A semiconductor device larger than the gate width of a transistor. In claim 1,
The second active region includes a drive transistor formation region in which the first and second drive transistors are formed, and a transfer transistor formation region in which the first and second transfer transistors are formed,
The width of the drive transistor formation region is a semiconductor device larger than the width of the transfer transistor formation region. In claim 1 or 2,
The semiconductor device, wherein the first and second word lines have a width greater than that of the first and second gate-gate electrode layers. In any one of Claims 1-3 ,
The semiconductor device, wherein the first and second active regions, the first and second gate-gate electrode layers, and the first and second word lines have a substantially linear pattern. In any one of Claims 1-4 ,
A semiconductor device, wherein the size of the memory cell is 2.5 μm ² or less. Comprising the semiconductor device according to any one of claims 1 to 5 memory system. Comprising the semiconductor device according to any one of claims 1 to 5 electronic device.

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