JP2018088553A - Field effect transistor and wireless communication device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a field effect transistor capable of reducing an external component of an off capacitance and a manufacturing method thereof.SOLUTION: A field effect transistor includes a gate electrode, a semiconductor layer having a source region and a drain region that sandwich the gate electrode, contact plugs that is provided on the source region and the drain region, first metals laminated on the contact plug, and a low dielectric constant region that is provided in a region between the first metals in the in-plane direction of the semiconductor layer and provided in a first region at least below the lower surface of the first metal in the lamination direction.SELECTED DRAWING: Figure 7

Description

  The present disclosure relates to a field effect transistor (FET) suitable for a switch element of a high-frequency device and a manufacturing method thereof.

  A high-frequency switch (RF-SW) for turning on and off a high frequency (RF) is used for a front end of a mobile communication terminal such as a mobile phone. An important characteristic of such a high frequency switch is a reduction in the loss of the high frequency passing therethrough. For that purpose, it is important to reduce the resistance of the on-state FET (on-resistance) or the capacitance of the off-state FET (off-capacitance), that is, to reduce the product of the on-resistance and off-capacitance (Ron * Coff). .

  The off-capacitance includes a component (intrinsic component) generated in a diffusion layer, a substrate, and the like, and a component (extrinsic component) generated in a gate electrode, a contact plug, a wiring thereon, and the like. For example, in the field of fine MOSFETs, it has been proposed to reduce the parasitic capacitance between the gate electrode and the contact plug by creating a gap around the gate electrode, thereby reducing external components (see, for example, Patent Document 1). .

JP 2002-359369 A

  However, in the configuration of Patent Document 1, it is difficult to sufficiently reduce the parasitic capacitance between the gate electrode and the wiring on the contact plug, or the capacitance (inter-wiring capacitance) generated between the wirings on the contact plug, There was still room for improvement.

  An object of the present disclosure is to provide a field effect transistor capable of reducing an external component of off-capacitance and a manufacturing method thereof.

A field effect transistor according to the present disclosure includes the following components (A) to (E).
(A) Gate electrode (B) Semiconductor layer having a source region and a drain region with the gate electrode in between (C) Contact plug provided on the source region and the drain region (D) Stacked on the contact plug A low dielectric constant region provided in a region between the first metals in the in-plane direction of the first metal (E) semiconductor layer and provided in a first region at least below the lower surface of the first metal in the stacking direction

  In the field effect transistor of the present disclosure, a low dielectric constant region is provided in a region between the first metals in the in-plane direction of the semiconductor layer, and in at least a first region below the lower surface of the first metal in the stacking direction. Yes. Therefore, the parasitic capacitance between the gate electrode and the contact plug or the parasitic capacitance between the gate electrode and the first metal is reduced, and the external component of the off capacitance is reduced.

The manufacturing method of the field effect transistor according to the present disclosure includes the following steps (A) to (E).
(A) Step of forming a gate electrode on the upper surface side of the semiconductor layer (B) Step of forming a source region and a drain region on the semiconductor layer with the gate electrode interposed therebetween (C) Contact plug on the source region and the drain region (D) A step of laminating the first metal on the contact plug (E) A region between the first metal in the in-plane direction of the semiconductor layer, at least below the lower surface of the first metal in the laminating direction Providing a low dielectric constant region in the first region

  According to the field effect transistor of the present disclosure or the method of manufacturing the field effect transistor of the present disclosure, the region between the first metals in the in-plane direction of the semiconductor layer is at least lower than the lower surface of the first metal in the stacking direction. Since the low dielectric constant region is provided in the first region, the external component of the off capacitance can be reduced.

  Note that the effects described here are not necessarily limited, and may be any effects described in the present disclosure.

It is a figure showing an example of the high frequency switch which has a field effect transistor concerning a 1st embodiment of this indication. It is a figure showing the SPST switch which is the basic composition of the high frequency switch shown in FIG. FIG. 3 is an equivalent circuit diagram of the SPST switch shown in FIG. 2. FIG. 4 is an equivalent circuit diagram when the SPST switch shown in FIG. 3 is on. FIG. 4 is an equivalent circuit diagram when the SPST switch shown in FIG. 3 is off. It is a top view showing the whole field effect transistor composition concerning a 1st embodiment of this indication. It is sectional drawing in the VII-VII line of FIG. It is a figure which decomposes | disassembles and represents the off capacity | capacitance of a general field effect transistor for every component. FIG. 8 is a cross-sectional view illustrating Modification 1 of the low dielectric constant region illustrated in FIG. 7. FIG. 8 is a cross-sectional view illustrating Modification Example 2 of the low dielectric constant region illustrated in FIG. 4 is a cross-sectional view illustrating a configuration of a field effect transistor according to Reference Example 1. FIG. A simulation for investigating the relationship between the width of the low dielectric constant region and the external component of the capacitance for the present embodiment shown in FIG. 7, the modified example 2 shown in FIG. 10, and the reference example 1 shown in FIG. It is a figure showing a result. FIG. 8 is a cross-sectional view illustrating a positional relationship between the field effect transistor and the low dielectric constant region illustrated in FIG. 7 and a multilayer wiring portion. FIG. 8 is a plan view illustrating a positional relationship between the field effect transistor and the low dielectric constant region illustrated in FIG. 7 and a gate contact. It is sectional drawing in the XV-XV line | wire of FIG. It is sectional drawing in the XVIA-XVIB line | wire of FIG. It is sectional drawing in the XVIIB-XVIIC line | wire of FIG. It is sectional drawing in the XVIIIC-XVIIID line | wire of FIG. FIG. 8 is a cross-sectional view illustrating a method of manufacturing the field effect transistor illustrated in FIG. 7 in order of steps. FIG. 20 is a cross-sectional diagram illustrating a process following the process in FIG. 19. FIG. 21 is a cross-sectional diagram illustrating a process following the process in FIG. 20. FIG. 22 is a cross-sectional diagram illustrating a process following the process in FIG. 21. FIG. 23 is a cross-sectional diagram illustrating a process following the process in FIG. 22. FIG. 24 is a cross-sectional diagram illustrating a process following the process in FIG. 23. FIG. 25 is a cross-sectional diagram illustrating a process following the process in FIG. 24. FIG. 26 is a cross-sectional diagram illustrating a process following the process in FIG. 25. FIG. 27 is a cross-sectional diagram illustrating a process following the process in FIG. 26. FIG. 28 is a cross-sectional diagram illustrating a process following the process in FIG. 27. FIG. 29 is a cross-sectional diagram illustrating a process following the process in FIG. 28. FIG. 30 is a cross-sectional diagram illustrating a process following the process in FIG. 29. FIG. 31 is a cross-sectional diagram illustrating a process following the process in FIG. 30. It is sectional drawing showing the structure of the field effect transistor which concerns on 2nd Embodiment of this indication. It is sectional drawing showing the structure of the field effect transistor which concerns on 3rd Embodiment of this indication. It is sectional drawing showing the structure of the field effect transistor which concerns on 4th Embodiment of this indication. It is a top view showing the composition of the field effect transistor concerning a 5th embodiment of this indication. It is sectional drawing in the XXXVI-XXXVI line | wire of FIG. It is sectional drawing in the XXXVII-XXXVII line | wire of FIG. FIG. 36 is a plan view illustrating a method of manufacturing the field effect transistor illustrated in FIG. 35 in order of steps. It is sectional drawing in the XXXIX-XXXIX line | wire of FIG. FIG. 39 is a plan view illustrating a process following the process in FIG. 38. It is sectional drawing in the XXXXI-XXXXI line of FIG. FIG. 41 is a cross-sectional view taken along a line XXXII-XXXII in FIG. 40. It is a top view showing the composition of the field effect transistor concerning a 6th embodiment of this indication. It is a block diagram showing an example of a radio | wireless communication apparatus.

Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. The description will be given in the following order.
1. First embodiment (high-frequency switch, field effect transistor; first layer below the lower surface of the first metal in the stacking direction; a second region between the lower surface and the upper surface of the first metal; Example of providing a low dielectric constant region in the third region above the upper surface of the metal)
2. Second Embodiment (Field Effect Transistor: Example in which a second metal is laminated on a first metal and a low dielectric constant region is extended between the second metals)
3. Third Embodiment (Field Effect Transistor: Example in which a low dielectric constant region is provided with a width larger than a portion of the first insulating film and the second insulating film covering the surface of the gate electrode)
4). Fourth Embodiment (Field Effect Transistor: Example in which first and second regions of low dielectric constant region are filled with fifth insulating film, and third region is a gap)
5. Fifth Embodiment (Field Effect Transistor; Example in which a low dielectric constant region is provided in a direction intersecting the gate electrode)
6). Sixth Embodiment (Field Effect Transistor; Example in which a low dielectric constant region is provided in a finger part of a gate electrode and at least a part of a connection part)
7). Application example (wireless communication equipment)

(First embodiment)
FIG. 1 illustrates a configuration of a high-frequency switch having a field effect transistor according to the first embodiment of the present disclosure. The high-frequency switch 1 is used for a front end of a portable information terminal such as a mobile phone. Depending on the number of input / output ports, the SPST (Single Pole Single Through), SPDT (shown in FIG. 2) is used. Single Pole Double Through), SP3T... SPNT (N is a real number). FIG. 1 shows an example of the SP10T switch. The SP10T switch has, for example, one pole connected to the antenna ANT and ten contacts. The high-frequency switch 1 can have various configurations, but any configuration of the high-frequency switch 1 is a combination of the basic circuit configurations of the SPST switch shown in FIG.

  FIG. 3 shows an equivalent circuit of the SPST switch 1A shown in FIG. The SPST switch 1A includes, for example, a first port Port1, a second port Port2, a first switching element FET1, and a second switching element FET2 connected to the antenna ANT. The first switching element FET1 is connected between the first port Port1 and the ground. The second switching element FET2 is connected between the first port Port1 and the second port Port2.

  In the SPST switch 1A, on / off control is performed by applying control voltages Vc1, Vc2 to the gates of the first switching element FET1 and the second switching element FET2 via resistors. At the time of turning on, as shown in FIG. 4, the first switching element FET2 becomes conductive and the first switching element FET1 becomes nonconductive. At the time of OFF, as shown in FIG. 5, the first switching element FET1 is turned on and the second switching element FET2 is turned off.

  The on-resistance and the off-capacitance of the first switching element FET1 and the second switching element FET2 are obtained by using values Ron [Ωmm], Coff [fF / mm], and gate widths Wg1 and Wg2 [mm] per unit length. , Ron / Wg1, Ron / Wg2, Coff * Wg1, and Coff * Wg2, respectively. The on-resistance is inversely proportional to the gate widths Wg1 and Wg2, and the off-capacitance is proportional to the gate widths Wg1 and Wg2.

  Another feature of on-resistance and off-capacitance is that loss due to on-resistance is not frequency dependent, but off-capacitance loss increases with increasing frequency. If an attempt is made to increase the gate width Wg in order to reduce the loss, a high frequency loss due to the input capacitance occurs. Therefore, in order to reduce the loss using the largest possible gate width Wg, it is important to reduce both Ron and Coff per unit length, that is, to reduce Ron * Coff (product) as much as possible.

  FIG. 6 is a plan view illustrating an overall configuration of the field effect transistor according to the first embodiment of the present disclosure. This field effect transistor 10 is a field effect transistor for a high frequency device that constitutes the first switching element FET1 or the second switching element FET2 in the SPST switch 1A shown in FIG. 3, and includes a gate electrode 20, a source electrode 30S, a drain Electrode 30D.

  The gate electrode 20 has a multi-finger structure having a plurality of finger portions 21 extending in the same direction (for example, the Y direction) and a connecting portion (gate routing wiring) 22 for connecting the plurality of finger portions 21. . Note that the gate width Wg of the field effect transistor 10 used in the high frequency switch 1 is considerably larger than that of a field effect transistor used for logic or the like in order to reduce loss, and is several hundreds of um to several mm. The length (finger length) L21 of the finger part 21 is, for example, several tens of um. The connecting portion 22 is connected to a gate contact (not shown in FIG. 6, see FIG. 14). In FIG. 6, the gate electrode 20 is shown with diagonal lines.

  In the following description and drawings, the longitudinal direction of the finger portion 21 of the gate electrode 20 is defined as the Y direction, the longitudinal direction of the connecting portion 22 is defined as the X direction, and the direction (lamination direction) perpendicular to both is defined as the Z direction.

  Similar to the gate electrode 20, the source electrode 30 </ b> S includes a finger portion 31 </ b> S extended in the same direction (for example, the Y direction), and a connecting portion (source routing wiring) 32 </ b> S that connects the plurality of finger portions 31 </ b> S. The coupling part 32S is connected to a source contact (not shown).

  Similar to the gate electrode 20, the drain electrode 30 </ b> D includes a finger part 31 </ b> D extended in the same direction (for example, the Y direction) and a connecting part (drain routing wiring) 32 </ b> D that connects the plurality of finger parts 31 </ b> D. The coupling part 32D is connected to a drain contact (not shown).

  The finger portions 31S of the source electrode 30S and the finger portions 31D of the drain electrode 30D are alternately arranged in the gap between the finger portions 21 of the gate electrode 20. The finger portion 21 of the gate electrode 20, the finger portion 31S of the source electrode 30S, and the finger portion 31D of the drain electrode 30D are disposed inside the active region (active region) AA. The connecting portion 22 of the gate electrode 20, the connecting portion 32S of the source electrode 30S, and the connecting portion 32D of the drain electrode 30D are element isolation regions AB outside the active region AA (not shown in FIG. 6, see FIG. 14). .) Is arranged.

  FIG. 7 shows a cross-sectional configuration taken along the line VII-VII in FIG. 6. One finger portion 21 of the gate electrode 20 and one finger portion 31S and drain electrode of the source electrode 30S disposed on both sides thereof are shown. One finger part 31D of 30D is represented. The field effect transistor 10 includes the gate electrode 20, the semiconductor layer 50, the contact plugs 60S and 60D, the first metal M1, and the low dielectric constant region 70 described above.

  The gate electrode 20 is provided on the semiconductor layer 50 with the gate oxide film 23 therebetween. The gate electrode 20 has a thickness of 150 nm to 200 nm, for example, and is made of polysilicon. The gate oxide film 23 has a thickness of about 5 nm to 10 nm, for example, and is made of silicon oxide (SiO 2).

  The semiconductor layer 50 is made of, for example, silicon (Si). The semiconductor layer 50 has a source region 50S and a drain region 50D made of n-type (n +) silicon with the gate electrode 20 therebetween. Low resistance regions 51S and 51D made of high-concentration n-type (n ++) silicon or silicide are provided on the surfaces of the source region 50S and the drain region 50D for connection to the contact plugs 60S and 60D. Extension regions 52S and 52D made of low-concentration n-type (n−) silicon are provided between the source region 50S and the gate electrode 20 and between the drain region 50D and the gate electrode 20.

  For example, the semiconductor layer 50 is provided on the support substrate 53 with a buried oxide film 54 interposed therebetween. That is, the support substrate 53, the buried oxide film 54, and the semiconductor layer 50 constitute an SOI (Silicon on Insulator) substrate 55. The support substrate 53 is made of, for example, a high resistance silicon substrate. The buried oxide film 54 is made of, for example, SiO2.

  The contact plugs 60S and 60D are connected to the low resistance regions 51S and 51D of the source region 50S. The contact plugs 60S and 60D have, for example, a laminated structure (not shown) of a titanium (Ti) layer, a titanium nitride (TiN) layer, and a tungsten (W) layer. The titanium layer is a film that reduces contact resistance with the lower layer of the contact plugs 60S and 60D. The titanium nitride layer is a barrier metal that suppresses diffusion of a tungsten layer provided on the inside thereof into silicon.

  The first metal M1 includes, for example, a source electrode 30S stacked on the contact plug 60S and a drain electrode 30D stacked on the contact plug 60D. For example, the first metal M1 has a thickness of 500 nm to 1000 nm and is made of aluminum (Al).

  The low dielectric constant region 70 is provided in a region between the first metals M1 in the XY plane direction of the semiconductor layer 50, that is, a region between the source electrode 30S and the drain electrode 30D (above the finger portion 21 of the gate electrode 20). It has been. Further, the low dielectric constant region 70 is provided in the first region A1 at least below the lower surface of the first metal M1 in the stacking direction Z. Thereby, in this field effect transistor 10, it is possible to reduce the external component of the off capacitance.

  That is, as shown in FIG. 8, the off-capacitance includes components (internal components) Cin generated in the diffusion layer, the substrate, etc., the gate electrode 20, the contact plugs 60S and 60D, and the first metal M1 thereon. And the like (extrinsic component) Cex.

  The internal component Cin includes, for example, the following. Capacitance Cssub, Cdsub generated between the source region 50S or the drain region 50D and the support substrate 53. Capacitances Csg and Cdg generated between the source region 50S or the drain region 50D and the gate electrode 20. A capacitance Cds generated between the source region 50S and the drain region 50D. Capacitances Csb and Cdb generated between the source region 50S or the drain region 50D and the lower part (body) of the semiconductor layer 50.

  The external component Cex includes, for example, the following. A capacitance between the gate electrode 20 and the contact plugs 60S and 60D or a capacitance CgM between the gate electrode 20 and the first metal M1. Capacitance (inter-wiring capacitance) CMM1 generated between the first metals M1.

  Note that FIG. 8 shows an off-capacitance of a general field effect transistor that is decomposed for each component. In FIG. 8, components corresponding to the field effect transistor 10 of the present embodiment shown in FIG. 7 are denoted by the same reference numerals.

  In order to reduce the off capacity, it is particularly effective to reduce the external component Cex. In the present embodiment, the external component Cex is reduced by providing the low dielectric constant region 70 in the above-described regions in the XY in-plane direction and the stacking direction Z. As a result, the product (Ron * Coff) of the on-resistance and the off-capacitance can be reduced, and the loss of the high-frequency switch 1 can be reduced.

  Specifically, as shown in FIG. 7, the low dielectric constant region 70 includes, in the stacking direction Z, the first region A1 described above and the second region A2 between the lower surface and the upper surface of the first metal M1. It is preferable to be provided in the third region A3 above the upper surface of the first metal M1. Accordingly, the capacitance between the gate electrode 20 and the contact plugs 60S and 60D, the capacitance CgM between the gate electrode 20 and the first metal M1, or the capacitance generated between the first metals M1 (inter-wiring capacitance). CMM1 and the like are suppressed, and the external component Cex of off capacitance is reduced.

(Modification 1)
Alternatively, as shown in FIG. 9, the low dielectric constant region 70 may be provided in the first region A1 and the second region A2 in the stacking direction Z. Even in this case, the capacitance between the gate electrode 20 and the contact plugs 60S and 60D, the capacitance CgM between the gate electrode 20 and the first metal M1, or the capacitance generated between the first metals M1. (Inter-wiring capacitance) CMM1 and the like are suppressed, and the external component Cex of the off capacitance is reduced.

(Modification 2)
Furthermore, the low dielectric constant region 70 may be provided in the first region A1 in the stacking direction Z as shown in FIG. Also in this case, the capacitance between the gate electrode 20 and the contact plugs 60S and 60D or the capacitance CgM between the gate electrode 20 and the first metal M1 is suppressed, and the external component Cex of the off capacitance is reduced.

(Reference Example 1)
FIG. 11 illustrates a cross-sectional configuration of a field effect transistor 10R according to Reference Example 1. Reference Example 1 has the same configuration as the field effect transistor 10 of the present embodiment shown in FIG. 7 except that the low dielectric constant region 70 is provided in the second region A2 in the stacking direction Z. doing.

(simulation result)
12 shows the width of the low dielectric constant region 70 of the external component Cex of the capacitance in the present embodiment shown in FIG. 7, the modification 2 shown in FIG. 10, and the reference example 1 shown in FIG. The simulation result which investigated the dependence with respect to W70 is represented.

  As can be seen from FIG. 12, the external component Cex of the capacitance tends to decrease as the width W70 of the low dielectric constant region 70 increases. In the second modification example in which the low dielectric constant region 70 is provided in the first region A1 and the second region A2 in the stacking direction Z, the low dielectric constant region 70 is provided only in the second region A2 in the stacking direction Z as compared with the reference example 1. Thus, the external component Cex of the capacity is reduced. Further, in the present embodiment in which the low dielectric constant region 70 is provided in the first region A1, the second region A2, and the third region A3 in the stacking direction Z, the low dielectric constant region 70 depends on the extending length in the stacking direction Z. However, it can be seen that the effect of reducing the external component Cex having a capacity equal to or greater than that of the second modification can be obtained.

  Further, the field effect transistor 10 shown in FIG. 1 includes at least one insulating film 80 on the semiconductor layer 50 and an opening provided from the upper surface of the at least one insulating film 80 toward the upper surface of the gate electrode 20. (Concave portion) P. The low dielectric constant region 70 is preferably provided in the opening P. As a result, the width WP of the opening P can be increased. Therefore, the problem that it is difficult for the etching solution to enter the narrow gap when the gap is provided in the vicinity of the gate electrode 20 by wet etching is solved. Thereby, the etching uniformity within the wafer surface of the SOI substrate 55 and the uniformity of the characteristics of the field effect transistor 10 can be improved. The width WP of the opening P is preferably, for example, 100 nm to 1000 nm because the opening P is provided between the source electrode 30S and the drain electrode 30D.

  At least one insulating film 80 preferably includes a plurality of insulating films having different etching rates. In the manufacturing process to be described later, the etching stop position of the opening P can be controlled with high accuracy by utilizing the difference in the etching rates of the plurality of insulating films. Therefore, the surface loss of the gate electrode 20, the side surface of the gate electrode 20 is scraped and the etching reaches the Si surface, the Si surface dose loss, the gate oxide film 23 side etching variation, It is possible to suppress an increase in the variation in threshold voltage caused thereby, stably manufacture the field effect transistor 10, and improve the reliability of the field effect transistor 10.

  Specifically, at least one insulating film 80 preferably includes, for example, a first insulating film 81, a second insulating film 82, and a third insulating film 83. The first insulating film 81 covers the surface (upper surface and side surfaces) of the gate electrode 20 and the upper surface of the semiconductor layer 50. The second insulating film 82 covers the surface of the first insulating film 81. The third insulating film 83 is provided between the surface of the second insulating film 82 and the lower surface of the first metal M1. The second insulating film 82 is preferably made of a material having a different etching rate from the first insulating film 81 and the third insulating film 83. For example, the first insulating film 81 and the third insulating film 83 are preferably composed of a silicon oxide (SiO 2) film, and the second insulating film 82 is preferably composed of a silicon nitride (SiN) film. As a result, the second insulating film 82 can have a function as an etching stopper layer. The opening P preferably penetrates at least the third insulating film 83 and reaches the upper surface of the second insulating film 82.

  In addition, at least one insulating film 80 preferably further includes a fourth insulating film 84. The fourth insulating film 84 covers the upper surface of the third insulating film 83 and the surface (upper surface and side surfaces) of the first metal M1. The opening P preferably reaches the upper surface of the second insulating film 82 from the upper surface of the fourth insulating film 84 through the fourth insulating film 84 and the third insulating film 83. The fourth insulating film 84 is preferably composed of, for example, a silicon oxide (SiO 2) film.

  Furthermore, it is preferable that at least one insulating film 80 further includes a fifth insulating film 85 on the fourth insulating film 84. An air gap AG (Air Gap) is preferably provided as a low dielectric constant region 70 in at least a part of the opening P. The configuration of the low dielectric constant region 70 or the gap AG is not particularly limited as long as it has a lower dielectric constant than the silicon oxide (SiO 2, dielectric constant 3.9) film constituting the third insulating film 83 and the fourth insulating film 84. For example, air (dielectric constant 1.0) may exist in the air gap AG or a vacuum may be used. The upper part of the gap AG is preferably closed by the fifth insulating film 85. As a result, the gap AG is hermetically sealed by the fifth insulating film 85. The fifth insulating film 85 may cover the side surface and the bottom surface of the opening P. The fifth insulating film 85 is made of, for example, a silicon oxide (SiO 2) film. Note that a sixth insulating film 86 made of, for example, silicon oxide (SiO 2) may be provided on the fifth insulating film 85 as necessary.

  For example, the low dielectric constant region 70 is preferably provided with a width W70 that is equal to or less than a width W82 of a portion of the first insulating film 81 and the second insulating film 82 that covers the surface of the gate electrode 20.

  FIG. 13 shows the positional relationship in the stacking direction Z between the field effect transistor 10 and the low dielectric constant region 70 shown in FIG. The field effect transistor 10 and the low dielectric constant region 70 are provided in the element region AA1 of the active region AA. The multilayer wiring portion 90 is provided in the wiring area AA2 outside the element area AA1 in the active area AA. The element region AA1 and the wiring region AA2 are separated by an element isolation layer 100 by an STI (Shallow Trench Isolation) method.

  The multilayer wiring unit 90 includes, for example, a first wiring layer 91 and a second wiring layer 92. For example, the first wiring layer 91 is the same layer as the source electrode 30S and the drain electrode 30D, that is, the first metal M1. The second wiring layer 92 is, for example, a second metal M2 that is an upper layer than the first metal M1. The first wiring layer 91 and the second wiring layer 92 are connected by, for example, a contact plug 93.

  The low dielectric constant region 70 is not provided between the first wiring layers 91 of the multilayer wiring portion 90 or between the second wiring layers 92. That is, the low dielectric constant region 70 is provided inside the field effect transistor 10 in the element region AA1 in the active region AA.

  FIG. 14 shows the positional relationship in the XY plane direction between the field effect transistor 10 and the low dielectric constant region 70 shown in FIG. 7 and the gate contact GC. The field effect transistor 10 and the low dielectric constant region 70 are provided in the active area AA. The gate contact GC is provided in the element isolation region AB outside the active region AA. In the element isolation region AB, an element isolation layer 100 by the STI method is provided over the entire surface instead of the semiconductor layer 50.

  In the active area AA, the finger part 21 of the gate electrode 20, the finger part 31S of the source electrode 30S, and the finger part 31D of the drain electrode 30D are provided. The finger portion 21 of the gate electrode 20 extends in one direction (for example, the Y direction). The finger part 31S of the source electrode 30S and the finger part 31D of the drain electrode 30D are extended in parallel to the finger part 21 of the gate electrode 20 on both sides of the finger part 21 of the gate electrode 20. The contact plugs 60S and 60D are provided below the finger part 31S of the source electrode 30S and the finger part 31D of the drain electrode 30D, and extend in parallel to the finger part 21 of the gate electrode 20. The low dielectric constant region 70 is provided on the finger portion 21 of the gate electrode 20 and extends in parallel to the finger portion 21 of the gate electrode 20. In other words, the low dielectric constant region 70 is provided at a position overlapping the finger portion 21 of the gate electrode 20 in the XY in-plane direction.

  In the element isolation region AB, a connecting portion 22 of the gate electrode 20, a connecting portion 32S of the source electrode 30S, and a connecting portion 32D of the drain electrode 30D are provided. The connecting portion 22 of the gate electrode 20 is connected to the gate contact GC. The connecting portion 32S of the source electrode 30S is connected to a source contact (not shown). The connecting portion 32D of the drain electrode 30D is connected to a drain contact (not shown).

  FIG. 15 illustrates a cross-sectional configuration of the gate contact GC illustrated in FIG. The gate contact GC has a connecting portion 22 of the gate electrode 20, a gate contact plug 24, and a gate contact layer 25 in this order on the element isolation layer 100 by the STI method. The gate contact plug 24 is provided in the same layer as the contact plugs 60S and 60D. The gate contact layer 25 is provided in the same layer as the source electrode 30S and the drain electrode 30D, that is, the first metal M1.

  FIG. 16 illustrates a cross-sectional configuration taken along line XVIA-XVIB in FIG. FIG. 17 illustrates a cross-sectional configuration along the line XVIIB-XVIIC in FIG. FIG. 18 illustrates a cross-sectional configuration taken along line XVIIIC-XVIIID in FIG.

  As shown in FIGS. 14 to 18, the low dielectric constant region 70 is preferably provided avoiding the gate contact GC. This is because when the low dielectric constant region 70 is provided on the connecting portion 22 of the gate contact GC, it is difficult to provide the gate contact plug 24 on the connecting portion 22.

  The gate contact GC is preferably covered with at least one insulating film 80, that is, the first insulating film 81 to the sixth insulating film 86, similarly to the gate electrode 20 in the field effect transistor 10. Since the gate contact GC is covered with at least one insulating film 80, the reliability of the gate contact GC is maintained.

  The field effect transistor 10 can be manufactured as follows, for example.

  19 to 31 show a method for manufacturing the field effect transistor 10 in the order of steps. First, as shown in FIG. 19, an SOI substrate 55 having a buried oxide film 54 and a semiconductor layer 50 is prepared on a support substrate 53, and an element isolation layer by, eg, STI method is provided on the semiconductor layer 50 of the SOI substrate 55. 100 is formed to delimit the element region AA1 in the active region AA.

  Next, a silicon oxide film is formed as an implantation through film (not shown) by, for example, a thermal oxidation method, and after performing well implantation and channel implantation on the active area AA, the implantation through film is removed. Subsequently, as shown in FIG. 20, a gate oxide film 23 made of, eg, silicon oxide is formed with a thickness of, eg, about 5 nm to 10 nm by thermal oxidation. After that, a gate electrode material film (not shown) made of polysilicon is formed with a thickness of, for example, 150 nm to 200 nm by, for example, CVD (Chemical Vapor Deposition). By processing this gate electrode material film by, for example, photolithography and etching, the gate electrode 20 is formed on the upper surface side of the semiconductor layer 50 with the gate oxide film 23 therebetween as shown in FIG. .

  After forming the gate electrode 20, as shown in FIG. 21, the gate electrode 20 and the offset spacer (not shown) are used as a mask by arsenic (As) or phosphorus (P) implantation IMPL. Extension regions 52S and 52D are formed on both sides. Further, a sidewall (not shown) is formed on the side surface of the gate electrode 20, and arsenic (As) or phosphorus (P) implantation is performed. Thereby, the source region 50S and the drain region 50D are formed in the semiconductor layer 50 with the gate electrode 20 therebetween. After that, the sidewall is removed.

  After forming the source region 50S and the drain region 50D, as shown in FIG. 22, the first insulating film 81 made of, eg, silicon oxide is formed on the surface of the gate electrode 20 and the upper surface of the semiconductor layer 50 by, eg, CVD. It is formed with a thickness of several tens of nm, for example, 10 nm to 30 nm.

  After the first insulating film 81 is formed, as shown in FIG. 23, the surface of the first insulating film 81 is made of a material having a different etching rate from the first insulating film 81, for example, silicon nitride, for example, by CVD. The second insulating film 82 is formed with a thickness of several nm to several tens of nm, for example, 5 nm to 30 nm.

  After forming the second insulating film 82, as shown in FIG. 24, the third insulating film 83 made of silicon oxide is formed on the second insulating film 82 by, for example, CVD with a thickness of, for example, 500 nm to 1000 nm. To do.

  After forming the third insulating film 83, as shown in FIG. 25, the third insulating film 83, the second insulating film 82, and a part of the first insulating film 81 are removed by photolithography and etching, and the source region 50S. A contact hole H1 is formed in the drain region 50D. The contact hole H1 is provided in parallel with the finger portion 21 of the gate electrode 20, as shown in the plan view of FIG.

  After the contact hole H1 is formed, as shown in FIG. 26, the low resistance regions 51S and 51D are formed by high concentration arsenic (As) or phosphorus (P) implantation IMPL.

  After forming the low resistance regions 51S and 51D, as shown in FIG. 27, contact plugs 60S and 60D having a laminated structure of a titanium layer, a titanium nitride layer and a tungsten layer are formed in the contact hole H1. Contact plugs 60S and 60D are provided on source region 50S and drain region 50D. Further, the contact plugs 60S and 60D are provided in parallel with the finger portion 21 of the gate electrode 20, as shown in the plan view of FIG.

  After forming the contact plugs 60S and 60D, as shown in FIG. 28, the source electrode 30S and the drain electrode 30D made of aluminum (Al) are formed on the contact plugs 60S and 60D as the first metal M1. The finger part 31S of the source electrode 30S and the finger part 31D of the drain electrode 30D are provided in parallel with the finger part 21 of the gate electrode 20, as shown in the plan view of FIG.

  After forming the source electrode 30S and the drain electrode 30D, as shown in FIG. 29, the fourth insulating film 84 made of silicon oxide is formed on the upper surface of the third insulating film 83 and the surface of the first metal M1 by, for example, the CVD method. Form.

  After forming the fourth insulating film 84, as shown in FIG. 30, the opening P is formed by photolithography and dry etching. The opening P is in a region between the first metals M1 in the XY in-plane direction of the semiconductor layer 50, specifically, a region between the source electrode 30S and the drain electrode 30D (above the finger portion 21 of the gate electrode 20). Form. The width WP of the opening P is, for example, 100 nm to 1000 nm. At this time, the second insulating film 82 functions as an etching stopper, and the etching of the opening P proceeds through the fourth insulating film 84 and the third insulating film 83 made of silicon oxide, and on the upper surface of the second insulating film 82. Stop.

  After the opening P is formed, as shown in FIG. 31, a fifth insulating film 85 made of silicon oxide is formed on the fourth insulating film 84 by, eg, CVD. The fifth insulating film 85 is deposited overhanging the upper portion of the opening P. Therefore, before the fifth insulating film 85 is buried in the opening P, the upper portion of the opening P is closed by the fifth insulating film 85, and a gap AG hermetically sealed is formed in the opening P. The side surface and the bottom surface of the opening P may be covered with the fifth insulating film 85. The air gap AG has a lower dielectric constant than the third insulating film 84, the fourth insulating film 84, and the fifth insulating film 85 (silicon oxide, dielectric constant 3.9), and functions as a low dielectric constant region 70. Air (dielectric constant 1.0) may be present in the gap AG, and may be a vacuum, and is not particularly limited. The air gap AG, that is, the low dielectric constant region 70 includes a first region A1 below the lower surface of the first metal M1, a second region A2 between the lower surface and the upper surface of the first metal M1, and an upper surface of the first metal. Is also provided continuously and integrally over the upper third region A3.

  After that, as shown in FIG. 7, a sixth insulating film 86 is formed on the fifth insulating film 85 as necessary. Although not shown, the second metal M2, the third metal M3, etc. are formed on the fifth insulating film 85 by sequentially forming an insulating film and a metal layer in the same manner as the first metal M1. Also good. Thus, the field effect transistor 10 shown in FIG. 7 is completed.

  In the field effect transistor 10, a first region A1 below the lower surface of the first metal M1 in the stacking direction Z in the region between the first metals M1 in the XY in-plane direction of the semiconductor layer 50, and the first metal A low dielectric constant region 70 is provided in the second region A2 between the lower surface and the upper surface of M1 and the third region A3 above the upper surface of the first metal M1. Therefore, the capacitance between the gate electrode 20 and the contact plugs 60S and 60D, the capacitance CgM between the gate electrode 20 and the first metal M1, or the capacitance (inter-wiring capacitance) CMM1 generated between the first metals M1. And the external component Cex of the off-capacitance is reduced.

  As described above, in the present embodiment, the low dielectric constant is applied to the region between the first metals M1 in the XY in-plane direction of the semiconductor layer 50 and to the first region A1 at least below the lower surface of the first metal M1 in the stacking direction Z. A rate region 70 is provided. Therefore, it is possible to reduce the external component Cex of the off-capacitance, reduce the product (RonCoff) of the on-resistance and the off-capacitance, and promote the reduction in loss that is an important characteristic of the high-frequency switch 1. Become.

  Further, the low dielectric constant region 70 is provided across the first region A1, the second region A2, and the third region A3 in the stacking direction Z. Therefore, the capacitance between the gate electrode 20 and the contact plugs 60S and 60D, the capacitance CgM between the gate electrode 20 and the first metal M1, the capacitance (inter-wiring capacitance) CMM1 generated between the first metals M1, etc. It is possible to reduce the external component Cex of the off capacitance.

  Further, at least one insulating film 80 including a plurality of insulating films having different etching rates is provided on the semiconductor layer 50. Therefore, it becomes possible to control the etching stop position of the opening P with high accuracy by utilizing the difference in the etching rates of the plurality of insulating films. Therefore, the surface loss of the gate electrode 20, the side surface of the gate electrode 20 is scraped and the etching reaches the Si surface, the Si surface dose loss, the gate oxide film 23 side etching variation, It is possible to suppress an increase in the variation in threshold voltage caused thereby, stably manufacture the field effect transistor 10, and improve the reliability of the field effect transistor 10.

  In addition, an opening P is provided from the upper surface of at least one insulating film 80 toward the upper surface of the gate electrode 20, and the low dielectric constant region 70 is provided in the opening P. Therefore, the width WP of the opening P can be increased. Therefore, the problem that it is difficult for the etching solution to enter the narrow gap when the gap is provided in the vicinity of the gate electrode 20 by wet etching is solved. Thereby, the etching uniformity within the wafer surface of the SOI substrate 55 and the uniformity of the characteristics of the field effect transistor 10 can be improved.

(Second Embodiment)
In the first embodiment, the case where only the first metal M1 is stacked on the contact plugs 60S and 60D has been described. However, the present disclosure can also be applied to the case where the second metal M2 is stacked on the first metal M1 as in the field effect transistor 10A illustrated in FIG. In this case, the low dielectric constant region 70 is also extended between the second metals M2, thereby reducing the capacitance (inter-wiring capacitance) CMM2 between the second metals M2 and reducing the off capacitance. It is possible to further suppress the external component Cex.

  The second metal M <b> 2 is provided between the fourth insulating film 84 and the fifth insulating film 85. The first metal M1 and the second metal M2 are connected by a contact plug 94. Further, at least one insulating film 80 further includes a seventh insulating film 87 covering the upper surface of the fourth insulating film 84 and the surface of the second metal M2. The opening P penetrates the seventh insulating film 87, the fourth insulating film, and the third insulating film 83 from the upper surface of the seventh insulating film 87 and reaches the upper surface of the second insulating film 82. In the opening P, an air gap AG similar to that of the first embodiment is provided as the low dielectric constant region 70.

  In the stacking direction Z, the air gap AG includes a first region A1 below the lower surface of the first metal M1, a second region A2 between the lower surface and the upper surface of the first metal M1, and an upper surface of the first metal M1. Is also provided in the upper third region A3. In the third region A3, the gap AG is provided between the first metal M1 and between the second metal M2. Therefore, in the present embodiment, as in the first embodiment, the capacitance between the gate electrode 20 and the contact plugs 60S and 60D or the capacitance CgM between the gate electrode 20 and the first metal M1, or In addition to suppressing the capacitance (inter-wiring capacitance) CMM1 generated between the first metals M1, the capacitance (inter-wiring capacitance) CMM2 generated between the second metals M2 is also suppressed, and the external component of the off-capacitance Cex is reduced.

(Third embodiment)
In the first embodiment, the low dielectric constant region 70 is provided with a width W70 that is equal to or less than the width W82 of the portion of the first insulating film 81 and the second insulating film 82 that covers the surface of the gate electrode 20. Explained the case. However, when the width of the finger portion 21 of the gate electrode 20 is reduced, the low dielectric constant region 70 is formed between the first insulating film 81 and the second insulating film 82 as in the field effect transistor 10B shown in FIG. Of these, a width W70 larger than the width W82 of the portion covering the surface of the gate electrode 20 may be provided.

(Fourth embodiment)
Further, in the first embodiment, the case where the air gap hermetically sealed in the opening P is provided as the low dielectric constant region 70 has been described. However, the low dielectric constant region 70 is not limited to the gap AG, and may be made of a material having a lower dielectric constant than the third insulating film 83 and the fourth insulating film 84 (insulating film through which the opening P passes). Specifically, for example, when the third insulating film 83 and the fourth insulating film 84 are silicon oxide (SiO 2, dielectric constant 3.9) films, the fifth insulating film 85 is made of SiOC (carbon-added oxide). It is also possible to make silicon and a dielectric constant of 2.9) so that at least a part of the opening P is filled with the fifth insulating film 85. For example, as in the field effect transistor 10C shown in FIG. 34, the first region A1 and the second region A2 of the low dielectric constant region have a lower dielectric constant than the third insulating film 83 and the fourth insulating film 84. The insulating film 85 may be embedded. In addition, the air gap AG may be provided in the third region A3 of the low dielectric constant region 70.

(Fifth embodiment)
In addition, in the first embodiment, the case where the low dielectric constant region 70 is extended in parallel with the finger portion 21 of the gate electrode 20 has been described. However, like the field effect transistor 10D shown in FIGS. 35 to 37, the low dielectric constant region 70 is in a direction intersecting the finger portion 21 of the gate electrode 20, for example, with respect to the finger portion 21 of the gate electrode 20. You may be extended in the perpendicular | vertical direction (X direction). As a result, the influence of misalignment between the gate electrode 20 and the opening P and the low dielectric constant region 70 can be reduced. In this case, a plurality of low dielectric constant regions 70 may be arranged side by side along the extending direction (Y direction) of the finger portion 21 of the gate electrode 20.

  38 to 42 show the method of manufacturing the field effect transistor 10 according to the present embodiment in the order of steps. In addition, the process which overlaps with 1st Embodiment is demonstrated with reference to FIG. 19 thru | or FIG.

  First, as shown in FIGS. 38 and 39, the gate electrode 20 is formed on the upper surface side of the semiconductor layer 50 by the steps shown in FIGS. 19 to 29 in the same manner as in the first embodiment. After the source region 50S and the drain region 50D are formed in the layer 50, the first insulating film 81 to the third insulating film 83, the contact plugs 60S and 60D, the first metal M1, and the fourth insulating film 84 are formed.

  Next, as shown in FIGS. 40 to 42, a resist film R1 is formed on the fourth insulating film 84, and an opening P is formed by dry etching using the resist film R1 as a mask.

  Subsequently, the resist film R1 is removed, and as shown in FIGS. 35 to 37, a fifth insulating film 85 is formed on the fourth insulating film 84, and the upper portion of the opening P is blocked by the fifth insulating film 85. Thus, an air gap AG hermetically sealed in the opening P is formed. Thus, the field effect transistor 10D shown in FIGS. 35 to 37 is completed.

(Sixth embodiment)
Furthermore, in the first embodiment, as shown in FIG. 14, the low dielectric constant region 70 (gap AG) is provided above the finger portion 21 of the gate electrode 20 in the active region AA. Explained the case. However, as in the field effect transistor 10E shown in FIG. 43, the low dielectric constant region 70 may be provided above the finger part 21 or at least above a part of the coupling part 22. Specifically, the low dielectric constant region 70 is preferably provided above the region of the connecting portion 22 that avoids the finger portion 31D and the connecting portion 32D of the drain electrode 30D. In FIG. 43, the low dielectric constant region 70 above the finger portion 21 of the gate electrode 20 is omitted.

(Application example)
FIG. 44 illustrates an example of a wireless communication device. The wireless communication device 3 is a mobile phone system having multiple functions such as voice, data communication, and LAN connection. The high frequency module 3 includes, for example, an antenna ANT, a high frequency switch 1, a high power amplifier HPA, a high frequency integrated circuit RFIC (Radio Frequency Integrated Circuit), a baseband unit BB, an audio output unit MIC, and a data output unit DT. And an interface unit I / F (for example, a wireless local area network (W-LAN), Bluetooth (registered trademark), etc.). The high frequency switch 1 is configured by the high frequency switch 1 described with reference to FIGS. 1 to 5 in the first embodiment. The high frequency integrated circuit RFIC and the baseband unit BB are connected by an interface unit I / F.

  In the wireless communication device 3, at the time of transmission, that is, when a transmission signal is output from the transmission system of the wireless communication device 3 to the antenna ANT, the transmission signal output from the baseband unit BB is the high frequency integrated circuit RFIC, The signal is output to the antenna ANT via the high power amplifier HPA and the high frequency switch 1.

  During reception, that is, when a signal received by the antenna ANT is input to the reception system of the wireless communication device 3, the reception signal is input to the baseband unit BB via the high frequency switch 1 and the high frequency integrated circuit RFIC. The signal processed by the baseband unit BB is output from an output unit such as an audio output unit MIC, a data output unit DT, and an interface unit I / F.

  While the present disclosure has been described with reference to the embodiment, the present disclosure is not limited to the above embodiment, and various modifications can be made.

  Furthermore, for example, in the above-described embodiment, the configuration of the high-frequency switch 1, the field effect transistor 10, and the wireless communication unit 3 has been specifically described, but these are limited to those including all of the illustrated components. It is not something. It is also possible to replace some components with other components.

  In addition, although the case where the field effect transistor 10 is applied to the high frequency switch 1 of the wireless communication device 3 has been described in the above embodiment, the field effect transistor 10 is not only a high frequency switch (RF-SW) but also a PA (Power Amplifier). It is also applicable to other high frequency devices such as

  Furthermore, the shape, material, and thickness of each layer described in the above embodiment, the film formation method, and the like are not limited. Other shapes, materials, and thicknesses may be used, or other film formation methods may be used. Good.

  Furthermore, for example, in the above embodiment, the case where the support substrate 53 of the SOI substrate 55 is a high resistance silicon substrate has been described. However, the SOI substrate 55 may be a so-called SOS (Silicon on Sapphire) substrate having a support substrate 53 made of sapphire. Since the support substrate 53 made of sapphire is insulative, the field effect transistor 10 formed on the SOS substrate exhibits characteristics closer to that of a compound FET such as GaAs. Note that the present disclosure is not limited to the SOI substrate or the SOS substrate, and can be applied to the case where the field effect transistor 10 is formed on a bulk substrate.

  In addition, the effect described in this specification is an illustration to the last, and is not limited, Moreover, there may exist another effect.

In addition, this technique can also take the following structures.
(1)
A gate electrode;
A semiconductor layer having a source region and a drain region with the gate electrode interposed therebetween;
A contact plug provided on the source region and the drain region;
A first metal laminated on the contact plug;
A low dielectric constant region provided in a region between the first metals in the in-plane direction of the semiconductor layer, and provided in a first region at least below the lower surface of the first metal in the stacking direction. Field effect transistor.
(2)
The electric field according to (1), wherein the low dielectric constant region is provided in the first region and a second region between the lower surface of the first metal and the upper surface of the first metal in the stacking direction. Effect transistor.
(3)
The field effect transistor according to (2), wherein the low dielectric constant region is provided in the first region, the second region, and a third region above the upper surface of the first metal in the stacking direction. .
(4)
At least one insulating film provided on the semiconductor layer;
An opening provided from the upper surface of the at least one insulating film toward the upper surface of the gate electrode,
The field effect transistor according to (3), wherein the low dielectric constant region is provided in the opening.
(5)
The field effect transistor according to (4), wherein the at least one insulating film includes a plurality of insulating films having different etching rates.
(6)
The at least one insulating film comprises:
A first insulating film covering a surface of the gate electrode and an upper surface of the semiconductor layer;
A second insulating film covering a surface of the first insulating film;
A third insulating film provided between the surface of the second insulating film and the lower surface of the first metal;
Including
The second insulating film is made of a material having a different etching rate from the first insulating film and the third insulating film,
The field effect transistor according to (4) or (5), wherein the opening penetrates at least the third insulating film and reaches the upper surface of the second insulating film.
(7)
The at least one insulating film further includes a fourth insulating film that covers an upper surface of the third insulating film and a surface of the first metal;
The field effect transistor according to (6), wherein the opening reaches the upper surface of the second insulating film from the upper surface of the fourth insulating film.
(8)
The at least one insulating film further includes a fifth insulating film on the fourth insulating film,
At least a part of the opening is provided with a gap as the low dielectric constant region,
The field effect transistor according to (7), wherein an upper portion of the gap is blocked by the fifth insulating film.
(9)
The field effect transistor according to (8), wherein the fifth insulating film covers a side surface and a bottom surface of the opening.
(10)
The low dielectric constant region is provided with a width equal to or less than a width of a portion of the first insulating film and the second insulating film that covers the surface of the gate electrode. Any one of (6) to (9) The field effect transistor as described.
(11)
The gate electrode is extended in one direction;
The field effect transistor according to any one of (1) to (10), wherein the contact plug, the first metal, and the low dielectric constant region are extended in parallel to the gate electrode.
(12)
An element region in which the source region and the drain region are provided in the semiconductor layer;
A wiring region having a multilayer wiring part;
An element isolation layer that partitions the element region and the wiring region; and
The field effect transistor according to any one of (1) to (11), wherein the low dielectric constant region is provided in the element region.
(13)
An active region including the element region and the wiring region;
An element isolation region provided outside the active region and provided with the element isolation layer;
The element isolation region has a gate contact connected to the gate electrode on the element isolation layer,
The field effect transistor according to (12), wherein the low dielectric constant region is provided to avoid the gate contact.
(14)
A second metal is further provided between the fourth insulating film and the fifth insulating film,
The at least one insulating film further includes a seventh insulating film that covers an upper surface of the fourth insulating film and a surface of the second metal;
The field effect transistor according to (8), wherein the opening reaches the upper surface of the second insulating film from the upper surface of the seventh insulating film.
(15)
The low dielectric constant region is provided with a width larger than a width of a portion of the first insulating film and the second insulating film that covers a surface of the gate electrode. Any one of (6) to (9) The field effect transistor according to 1.
(16)
The fifth insulating film made of a material having a lower dielectric constant than the third insulating film and the fourth insulating film is embedded in at least a part of the opening as the low dielectric constant region. Field effect transistor.
(17)
The gate electrode is extended in one direction;
The contact plug and the first metal extend in parallel to the gate electrode,
The field effect transistor according to any one of (1) to (16), wherein the low dielectric constant region is extended in a direction intersecting the gate electrode.
(18)
The gate electrode has a plurality of finger portions extended in the same direction, and a connecting portion for connecting the plurality of finger portions,
The field effect transistor according to any one of (1) to (17), wherein the low dielectric constant region is provided above the finger part or above at least a part of the coupling part.
(19)
The field effect transistor according to any one of (1) to (18), which is a field effect transistor for a high-frequency device.
(20)
Forming a gate electrode on the upper surface side of the semiconductor layer;
Forming a source region and a drain region with the gate electrode in between in the semiconductor layer;
Providing a contact plug on the source region and the drain region;
Laminating a first metal on the contact plug;
A step of providing a low dielectric constant region in a region between the first metals in the in-plane direction of the semiconductor layer and in at least a first region below the lower surface of the first metal in the stacking direction. Production method.

DESCRIPTION OF SYMBOLS 1 ... High frequency switch, 3 ... Wireless communication apparatus, 10, 10A-10E ... Field effect transistor, 20 ... Gate electrode, 21 ... Finger part, 22 ... Connection part, 23 ... Gate oxide film, 24 ... Gate contact plug, 25 ... Gate contact layer, 30S ... source electrode, 31S ... finger part, 32S ... connection part, 30D ... drain electrode, 31D ... finger part, 32D ... connection part, 50 ... semiconductor layer, 50S ... source region, 50D ... drain region, 51S , 51D ... low resistance region, 52S, 52D ... extension region, 53 ... support substrate, 54 ... buried oxide film, 55 ... SOI substrate, 60S, 60D ... contact plug, 70 ... low dielectric constant region, 80 ... at least one layer of insulation 81, first insulating film, 82, second insulating film, 83, third insulating film, 84, fourth insulating film, 85 5th insulating film, 86 ... 6th insulating film, 87 ... 7th insulating film, 90 ... Multi-layer wiring part, 91 ... 1st wiring layer, 92 ... 2nd wiring layer, 93 ... Contact plug, 100 ... Element isolation layer, A1 ... first region, A2 ... second region, A3 ... third region, AA ... active region, AA1 ... element region, AA2 ... wiring region, AB ... element isolation region, AG ... gap, M1 ... first metal, M2 ... second metal, P ... opening.

The present disclosure relates to a field effect transistor (FET) suitable for a switch element of a high-frequency device and a wireless communication apparatus including the field effect transistor .

An object of the present disclosure is to provide a field effect transistor capable of reducing an external component of off-capacitance and a wireless communication device including the field effect transistor .

The 1st field effect transistor by this indication is provided with the component of the following (A)-( F ).
(A) Gate electrode (B) Semiconductor layer having a source region and a drain region with the gate electrode in between (C) First contact plug provided on the source region and a second contact provided on the drain region A plurality of contact plugs including plugs (D) A plurality of first metals respectively stacked on a plurality of contact plugs
(E) One or more insulating films provided in a region between at least the plurality of contact plugs in the in-plane direction of the semiconductor layer ( F ) The upper surface of the gate electrode between the plurality of contact plugs in the in-plane direction of the semiconductor layer And a low dielectric constant region provided in a first region below the lower surfaces of at least a plurality of first metals in the stacking direction.
At least one insulating film of the one or more insulating films occupies at least a part of a region between one contact plug of the plurality of contact plugs and the side surface of the gate electrode.
A second field effect transistor according to the present disclosure includes the following components (A) to (G).
(A) Gate electrode
(B) A semiconductor layer having a source region and a drain region with a gate electrode therebetween
(C) A plurality of contact plugs including a first contact plug provided on the source region and a second contact plug provided on the drain region
(D) A plurality of first metals respectively stacked on a plurality of contact plugs.
(E) A first group of one or more insulating films provided in at least a region between the plurality of contact plugs in the in-plane direction of the semiconductor layer and provided below the lower surfaces of the plurality of first metals in the stacking direction.
(F) A second group of one or more insulating films provided in at least a region between the plurality of contact plugs in the in-plane direction of the semiconductor layer and provided above a part of the upper surface of the gate electrode in the stacking direction.
(G) a first electrode disposed between the plurality of contact plugs in the in-plane direction of the semiconductor layer and above at least a part of the upper surface of the gate electrode and below the lower surfaces of at least the plurality of first metals in the stacking direction; Low dielectric constant region provided in the region
At least one insulating film in the first group of one or more insulating films occupies at least a part of a region between one contact plug of the plurality of contact plugs and the side surface of the gate electrode.
A third field effect transistor according to the present disclosure includes the following components (A) to (F).
(A) Gate electrode
(B) A semiconductor layer having a source region and a drain region with a gate electrode therebetween
(C) A plurality of contact plugs including a first contact plug provided on the source region and a second contact plug provided on the drain region
(D) A plurality of first metals respectively stacked on a plurality of contact plugs.
(E) One or more insulating films provided in a region between at least a plurality of contact plugs in the in-plane direction of the semiconductor layer
(F) Provided between the plurality of contact plugs in the in-plane direction of the semiconductor layer and provided in a region extending from above at least a part of the upper surface of the gate electrode to at least the upper surfaces of the first metal in the stacking direction. The lower dielectric constant region is located below the lower surfaces of the plurality of first metals.
At least one insulating film of the one or more insulating films occupies at least a part of a region between one contact plug of the plurality of contact plugs and the side surface of the gate electrode.

In the first field effect transistor of the present disclosure, between the plurality of contact plugs in the in-plane direction of the semiconductor layer , above at least a part of the upper surface of the gate electrode and from the lower surfaces of at least the plurality of first metals in the stacking direction. In the lower first region, a low dielectric constant region is provided. In addition, at least one of the one or more insulating films occupies at least a part of a region between one contact plug of the plurality of contact plugs and the side surface of the gate electrode. Therefore, the parasitic capacitance between the gate electrode and the contact plug or the parasitic capacitance between the gate electrode and the first metal is reduced, and the external component of the off capacitance is reduced.
In the second field effect transistor of the present disclosure, between the plurality of contact plugs in the in-plane direction of the semiconductor layer, above at least a part of the upper surface of the gate electrode and from the lower surfaces of at least the plurality of first metals in the stacking direction. In the lower first region, a low dielectric constant region is provided. In addition, at least one insulating film of the one or more insulating films of the first group occupies at least a part of a region between one contact plug of the plurality of contact plugs and the side surface of the gate electrode. . Therefore, the parasitic capacitance between the gate electrode and the contact plug or the parasitic capacitance between the gate electrode and the first metal is reduced, and the external component of the off capacitance is reduced.
In the third field effect transistor of the present disclosure, between the plurality of contact plugs in the in-plane direction of the semiconductor layer, it extends from above at least a part of the upper surface of the gate electrode in the stacking direction to the upper surfaces of at least the plurality of first metals. A low dielectric constant region is provided in the existing region. The lower end of the region where the low dielectric constant region is provided is located below the lower surfaces of the plurality of first metals. In addition, at least one of the one or more insulating films occupies at least a part of a region between one contact plug of the plurality of contact plugs and the side surface of the gate electrode. Therefore, the parasitic capacitance between the gate electrode and the contact plug or the parasitic capacitance between the gate electrode and the first metal is reduced, and the external component of the off capacitance is reduced.

  A high-frequency device according to the present disclosure includes a high-frequency switch having a field-effect transistor and a high-frequency integrated circuit connected to the high-frequency switch, and the field-effect transistor has the following components (A) to (F). is there.
(A) Gate electrode
(B) A semiconductor layer having a source region and a drain region with a gate electrode therebetween
(C) A plurality of contact plugs including a first contact plug provided on the source region and a second contact plug provided on the drain region
(D) A plurality of first metals respectively stacked on a plurality of contact plugs.
(E) One or more insulating films provided in a region between at least a plurality of contact plugs in the in-plane direction of the semiconductor layer
(F) Between the plurality of contact plugs in the in-plane direction of the semiconductor layer, the first electrode is provided above at least a part of the upper surface of the gate electrode and at the lower side of the lower surfaces of the plurality of first metals in the stacking direction. Low dielectric constant region provided in the region
  At least one insulating film of the one or more insulating films occupies at least a part of a region between one contact plug of the plurality of contact plugs and the side surface of the gate electrode.

According to the first field effect transistor of the present disclosure or the wireless communication device of the present disclosure, the stacking direction is disposed between the plurality of contact plugs in the in-plane direction of the semiconductor layer and above at least part of the upper surface of the gate electrode. The low dielectric constant region is provided in the first region below at least the lower surfaces of the plurality of first metals . Further, at least one insulating film occupies at least a part of a region between one contact plug of the plurality of contact plugs and the side surface of the gate electrode. Therefore , it is possible to reduce the external component of the off capacitance.
According to the second field effect transistor of the present disclosure, between the plurality of contact plugs in the in-plane direction of the semiconductor layer, above at least a part of the upper surface of the gate electrode, at least the plurality of first metals in the stacking direction. A low dielectric constant region is provided in the first region below the lower surface. Further, at least one insulating film of the one or more insulating films of the first group occupies at least a part of a region between one contact plug of the plurality of contact plugs and the side surface of the gate electrode. did. Therefore, it is possible to reduce the external component of the off capacitance.
According to the third field effect transistor of the present disclosure, between the plurality of contact plugs in the in-plane direction of the semiconductor layer, the top surfaces of at least the plurality of first metals from above the at least part of the top surface of the gate electrode in the stacking direction. A low dielectric constant region is provided in the region extending up to. The lower end of the region where the low dielectric constant region was provided was positioned below the lower surfaces of the plurality of first metals. Further, at least one of the one or more insulating films occupies at least a part of a region between one contact plug of the plurality of contact plugs and the side surface of the gate electrode. Therefore, it is possible to reduce the external component of the off capacitance.

(First embodiment)
FIG. 1 illustrates a configuration of a high-frequency switch having a field effect transistor according to the first embodiment of the present disclosure. The high-frequency switch 1 is used for a front end of a portable information terminal such as a cellular phone. Depending on the number of input / output ports, the SPS shown in FIG.
They are used in various configurations such as T (Single Pole Single Throw ), SPDT (Single Pole Double Throw ), SP3T... SPNT (N is a real number). FIG. 1 shows an example of the SP10T switch. The SP10T switch has, for example, one pole connected to the antenna ANT and ten contacts. The high-frequency switch 1 can have various configurations, but any configuration of the high-frequency switch 1 is a combination of the basic circuit configurations of the SPST switch shown in FIG.

In the SPST switch 1A, on / off control is performed by applying control voltages Vc1, Vc2 to the gates of the first switching element FET1 and the second switching element FET2 via resistors. At the time of ON, as shown in FIG. 4, the second switching element FET2 becomes conductive, and the first switching element FET1 becomes nonconductive. At the time of OFF, as shown in FIG. 5, the first switching element FET1 is turned on and the second switching element FET2 is turned off.

(simulation result)
12 shows the width of the low dielectric constant region 70 of the external component Cex of the capacitance in the present embodiment shown in FIG. 7, the modification 1 shown in FIG. 9 , and the reference example 1 shown in FIG. The simulation result which investigated the dependence with respect to W70 is represented.

As can be seen from FIG. 12, the external component Cex of the capacitance tends to decrease as the width W70 of the low dielectric constant region 70 increases. Further, in the first modification is provided a low dielectric constant region 70 in the first region A1 and second region A2 in the stacking direction Z, as compared to Reference Example 1 in the stacking direction Z of the low dielectric region 70 provided in only the second region A2 Thus, the external component Cex of the capacity is reduced. Further, in the present embodiment in which the low dielectric constant region 70 is provided in the first region A1, the second region A2, and the third region A3 in the stacking direction Z, the low dielectric constant region 70 depends on the extending length in the stacking direction Z. However, it turns out that the external component Cex reduction effect of the capacity | capacitance equivalent to or more than the modification 1 is acquired.

Furthermore, the field effect transistor 10 shown in FIG. 7 includes at least one insulating film 80 on the semiconductor layer 50 and an opening provided from the upper surface of the at least one insulating film 80 toward the upper surface of the gate electrode 20. (Concave portion) P. The low dielectric constant region 70 is preferably provided in the opening P. As a result, the width WP of the opening P can be increased. Therefore, the problem that it is difficult for the etching solution to enter the narrow gap when the gap is provided in the vicinity of the gate electrode 20 by wet etching is solved. Thereby, the etching uniformity within the wafer surface of the SOI substrate 55 and the uniformity of the characteristics of the field effect transistor 10 can be improved. The width WP of the opening P is preferably, for example, 100 nm to 1000 nm because the opening P is provided between the source electrode 30S and the drain electrode 30D.

After the opening P is formed, as shown in FIG. 31, a fifth insulating film 85 made of silicon oxide is formed on the fourth insulating film 84 by, eg, CVD. The fifth insulating film 85 is deposited overhanging the upper portion of the opening P. Therefore, before the fifth insulating film 85 is buried in the opening P, the upper portion of the opening P is closed by the fifth insulating film 85, and a gap AG hermetically sealed is formed in the opening P. The side surface and the bottom surface of the opening P may be covered with the fifth insulating film 85. The air gap AG has a lower dielectric constant than the third insulating film 83 , the fourth insulating film 84, and the fifth insulating film 85 (silicon oxide, dielectric constant 3.9), and functions as a low dielectric constant region 70. Air (dielectric constant 1.0) may be present in the gap AG, and may be a vacuum, and is not particularly limited. The air gap AG, that is, the low dielectric constant region 70 includes a first region A1 below the lower surface of the first metal M1, a second region A2 between the lower surface and the upper surface of the first metal M1, and an upper surface of the first metal. Is also provided continuously and integrally over the upper third region A3.

The second metal M <b> 2 is provided between the fourth insulating film 84 and the fifth insulating film 85. The first metal M1 and the second metal M2 are connected by a contact plug 94. Further, at least one insulating film 80 further includes a seventh insulating film 87 covering the upper surface of the fourth insulating film 84 and the surface of the second metal M2. The opening P penetrates the seventh insulating film 87, the fourth insulating film 84, and the third insulating film 83 from the upper surface of the seventh insulating film 87 and reaches the upper surface of the second insulating film 82. In the opening P, an air gap AG similar to that of the first embodiment is provided as the low dielectric constant region 70.

(Fourth embodiment)
Further, in the first embodiment, the case where the air gap hermetically sealed in the opening P is provided as the low dielectric constant region 70 has been described. However, the low dielectric constant region 70 is not limited to the gap AG, and may be made of a material having a lower dielectric constant than the third insulating film 83 and the fourth insulating film 84 (insulating film through which the opening P passes). Specifically, for example, when the third insulating film 83 and the fourth insulating film 84 are silicon oxide (SiO 2, dielectric constant 3.9) films, the fifth insulating film 85 is made of SiOC (carbon-added oxide). It is also possible to make silicon and a dielectric constant of 2.9) so that at least a part of the opening P is filled with the fifth insulating film 85. For example, as in the field effect transistor 10C shown in FIG. 34, the first region A1 and the second region A2 of the low dielectric constant region 70 have a lower dielectric constant than the third insulating film 83 and the fourth insulating film 84. 5 may be embedded with an insulating film 85. In addition, the air gap AG may be provided in the third region A3 of the low dielectric constant region 70.

Figure 38 to Figure 42 is to the method of manufacturing the field effect transistor 10 D according to the embodiment shown in process order. In addition, the process which overlaps with 1st Embodiment is demonstrated with reference to FIG. 19 thru | or FIG.

(Application example)
FIG. 44 illustrates an example of a wireless communication device. The wireless communication device 3 is a mobile phone system having multiple functions such as voice, data communication, and LAN connection. The wireless communication device 3 includes, for example, an antenna ANT, a high frequency switch 1, a high power amplifier HPA, a high frequency integrated circuit RFIC (Radio Frequency Integrated Circuit), a baseband unit BB, an audio output unit MIC, and a data output unit. DT and interface unit I / F (for example, wireless LAN (W-LAN; Wireless Local Area Network), Bluetooth (registered trademark), etc.). The high frequency switch 1 is configured by the high frequency switch 1 described with reference to FIGS. 1 to 5 in the first embodiment. The high frequency integrated circuit RFIC and the baseband unit BB are connected by an interface unit I / F.

Claims (20)

A gate electrode;
A semiconductor layer having a source region and a drain region with the gate electrode interposed therebetween;
A contact plug provided on the source region and the drain region;
A first metal laminated on the contact plug;
A low dielectric constant region provided in a region between the first metals in the in-plane direction of the semiconductor layer, and provided in a first region at least below the lower surface of the first metal in the stacking direction. Field effect transistor. The field effect according to claim 1, wherein the low dielectric constant region is provided in the first region and a second region between a lower surface of the first metal and an upper surface of the first metal in the stacking direction. Transistor. The field effect transistor according to claim 2, wherein the low dielectric constant region is provided in the first region, the second region, and a third region above the upper surface of the first metal in the stacking direction. At least one insulating film provided on the semiconductor layer;
An opening provided from the upper surface of the at least one insulating film toward the upper surface of the gate electrode,
The field effect transistor according to claim 3, wherein the low dielectric constant region is provided in the opening. The field effect transistor according to claim 4, wherein the at least one insulating film includes a plurality of insulating films having different etching rates. The at least one insulating film comprises:
A first insulating film covering a surface of the gate electrode and an upper surface of the semiconductor layer;
A second insulating film covering a surface of the first insulating film;
A third insulating film provided between the surface of the second insulating film and the lower surface of the first metal;
Including
The second insulating film is made of a material having a different etching rate from the first insulating film and the third insulating film,
The field effect transistor according to claim 4, wherein the opening penetrates at least the third insulating film and reaches the upper surface of the second insulating film. The at least one insulating film further includes a fourth insulating film that covers an upper surface of the third insulating film and a surface of the first metal;
The field effect transistor according to claim 6, wherein the opening reaches the upper surface of the second insulating film from the upper surface of the fourth insulating film. The at least one insulating film further includes a fifth insulating film on the fourth insulating film,
At least a part of the opening is provided with a gap as the low dielectric constant region,
The field effect transistor according to claim 7, wherein an upper portion of the gap is blocked by the fifth insulating film. The field effect transistor according to claim 8, wherein the fifth insulating film covers a side surface and a bottom surface of the opening. The field effect transistor according to claim 6, wherein the low dielectric constant region is provided with a width equal to or less than a width of a portion of the first insulating film and the second insulating film that covers a surface of the gate electrode. The gate electrode is extended in one direction;
The field effect transistor according to claim 1, wherein the contact plug, the first metal, and the low dielectric constant region are extended in parallel to the gate electrode. An element region in which the source region and the drain region are provided in the semiconductor layer;
A wiring region having a multilayer wiring part;
An element isolation layer that partitions the element region and the wiring region; and
The field effect transistor according to claim 1, wherein the low dielectric constant region is provided in the element region. An active region including the element region and the wiring region;
An element isolation region provided outside the active region and provided with the element isolation layer;
The element isolation region has a gate contact connected to the gate electrode on the element isolation layer,
The field effect transistor according to claim 12, wherein the low dielectric constant region is provided to avoid the gate contact. A second metal is further provided between the fourth insulating film and the fifth insulating film,
The at least one insulating film further includes a seventh insulating film that covers an upper surface of the fourth insulating film and a surface of the second metal;
The field effect transistor according to claim 8, wherein the opening reaches the upper surface of the second insulating film from the upper surface of the seventh insulating film. The field effect transistor according to claim 6, wherein the low dielectric constant region is provided with a width larger than a width of a portion of the first insulating film and the second insulating film that covers a surface of the gate electrode. The electric field according to claim 7, wherein a fifth insulating film made of a material having a dielectric constant lower than that of the third insulating film and the fourth insulating film is embedded in at least a part of the opening as the low dielectric constant region. Effect transistor. The gate electrode is extended in one direction;
The contact plug and the first metal extend in parallel to the gate electrode,
The field effect transistor according to claim 1, wherein the low dielectric constant region is extended in a direction intersecting the gate electrode. The gate electrode has a plurality of finger portions extended in the same direction, and a connecting portion for connecting the plurality of finger portions,
The field effect transistor according to claim 1, wherein the low dielectric constant region is provided above the finger part or above at least a part of the coupling part. The field effect transistor according to claim 1, which is a field effect transistor for a high frequency device. Forming a gate electrode on the upper surface side of the semiconductor layer;
Forming a source region and a drain region with the gate electrode in between in the semiconductor layer;
Providing a contact plug on the source region and the drain region;
Laminating a first metal on the contact plug;
A step of providing a low dielectric constant region in a region between the first metals in the in-plane direction of the semiconductor layer and in at least a first region below the lower surface of the first metal in the stacking direction. Production method.

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