JP2007134651A - Thin-film capacitor, its manufacturing method, mounting substrate and semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thin-film capacitor with stable electrical characteristics. <P>SOLUTION: This thin-film capacitor has a dielectric layer between a first electrode layer and a second electrode layer, and the dielectric layer has a Ta oxide film layer containing C. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a thin film capacitor, a mounting substrate having the thin film capacitor, and a semiconductor device.

  In recent years, with the thinning of semiconductor devices on which semiconductor chips are mounted, thinning of decoupling capacitors (sometimes called decoupling capacitors or bypass capacitors) for suppressing fluctuations in the power supply voltage of the semiconductor chips and stabilizing the operation. There is a request.

  In order to further improve the operating speed of the semiconductor chip in the future, it is expected that the operating frequency of the semiconductor chip will be increased. Therefore, in order to reduce the inductance of the connection of the decoupling capacitor, the decoupling capacitor should be as semiconductor as possible. A structure installed near the chip is preferable. For this reason, various thin film capacitors corresponding to the above requirements have been proposed.

In such a thin film capacitor, a metal oxide (for example, Ta oxide) that can be easily formed into a thin film and can be formed with a relatively high dielectric constant may be used as the dielectric layer. there were.
JP 2003-347168 A

  However, there is a concern that the above-described metal oxide, for example, Ta oxide, may change its electrical characteristics by heating. For example, when a dielectric layer made of an oxide of Ta is formed and then the dielectric layer is heated, the resistance value of the dielectric layer may be lowered. This is considered to be caused by diffusion (desorption) of oxygen in the metal oxide by heating.

  Accordingly, the present invention provides a novel and useful thin film capacitor, a manufacturing method for manufacturing the thin film capacitor, a mounting substrate using the thin film capacitor, and a semiconductor device using the thin film capacitor, which solve the above problems. It is an issue.

  A specific problem of the present invention is to provide a thin film capacitor having stable electrical characteristics, a manufacturing method for manufacturing the thin film capacitor, a mounting substrate using the thin film capacitor, and a semiconductor device using the thin film capacitor. It is.

  According to a first aspect of the present invention, there is provided a thin film capacitor in which a dielectric layer is formed between a first electrode layer and a second electrode layer. This is solved by a thin film capacitor having a Ta oxide film layer.

  The thin film capacitor has characteristics that electric characteristics are stable and fluctuation of electric characteristics due to heating is small.

  Further, when the dielectric layer further includes a Ta oxide film layer, the electric characteristics of the capacitor are further improved.

  Further, when the Ta oxide film layer containing C is formed by anodizing the Ta layer containing C, the control of the film thickness of the Ta oxide film layer containing C is facilitated, resulting in variations in electrical characteristics. Becomes smaller.

  In the second aspect of the present invention, the above-described problems are solved by a step of forming a first electrode layer, a step of forming a dielectric layer on the first electrode layer, and on the dielectric layer. Forming a second electrode layer, wherein the step of forming the dielectric layer includes a film forming step of forming a Ta layer containing C and the C. The problem is solved by a method of manufacturing a thin film capacitor including an oxidation step of oxidizing the Ta layer.

  According to the method for manufacturing the thin film capacitor, it is possible to manufacture a thin film capacitor having stable electrical characteristics and little variation in electrical characteristics due to heating.

  The film formation step includes a first film formation step for forming a Ta layer on the first electrode layer, and a second film formation step for forming a Ta layer containing C on the Ta layer. The variation of the electrical characteristics of the formed thin film capacitor is reduced, which is preferable.

  The Ta layer and the Ta layer containing C may be formed by a sputtering method.

  In the oxidation step, it is preferable that at least a part of the Ta layer is oxidized together with the Ta layer containing C because variation in electric characteristics of the formed thin film capacitor is reduced.

  According to a third aspect of the present invention, there is provided a mounting substrate having a thin film capacitor connected to a semiconductor chip and mounting the semiconductor chip, wherein the thin film capacitor includes the first electrode layer and the first electrode layer. This is solved by a mounting substrate characterized in that a Ta oxide film layer containing C is formed between the second electrode layers.

  The mounting board is characterized in that the electrical characteristics of the thin film capacitor are stable and the mounted semiconductor device operates stably.

  According to a fourth aspect of the present invention, there is provided a semiconductor device having a thin film capacitor connected to a semiconductor chip, wherein the semiconductor chip is mounted on a mounting substrate. This is solved by a semiconductor device characterized in that a Ta oxide film layer containing C is formed between the first electrode layer and the second electrode layer.

  The semiconductor device is characterized in that the electrical characteristics of the thin film capacitor are stable and the mounted semiconductor device operates stably.

  According to the present invention, it is possible to provide a thin film capacitor having stable electrical characteristics, a manufacturing method for manufacturing the thin film capacitor, a mounting substrate using the thin film capacitor, and a semiconductor device using the thin film capacitor. Become.

  Next, embodiments of the present invention will be described with reference to the drawings.

  1A is a cross-sectional view schematically showing a thin film capacitor 100 according to Embodiment 1 of the present invention, and FIG. 1B is a plan view of the thin film capacitor shown in FIG. 1A. 1B corresponds to FIG. 1A, and the same reference numerals are given to the same portions in FIGS. 1A and 1B.

  Referring to FIGS. 1A and 1B, the thin film capacitor 100 includes a dielectric layer 105 formed between a lower electrode layer (first electrode layer) 103 and an upper electrode layer (second electrode layer) 106. This is a thin film capacitor.

  The lower electrode layer 103 is made of, for example, Cu, and is formed on a substrate 101 made of, for example, Si via an insulating layer 102 made of, for example, a silicon oxide film. When the lower electrode layer 103 is formed by an electrolytic plating method, a seed layer 103A serving as a power feeding layer at the time of electrolytic plating is formed between the insulating layer 102 and the lower electrode layer 103. Similarly, when the upper electrode layer 106 is formed by an electrolytic plating method, a seed layer 106A serving as a power feeding layer at the time of electrolytic plating is formed between the dielectric layer 105 and the upper electrode layer 106. .

  A Ta layer 104 is formed between the dielectric layer 105 and the lower electrode layer 103. The Ta layer 104 is a layer formed in the step of forming the dielectric layer 105.

  In addition, a substantially cylindrical plug 103B is formed in an opening 106B that penetrates the upper electrode layer 106, the seed layer 106A, and the dielectric layer 105 so as to stand on the Ta layer 104. .

  In the above configuration, the upper electrode layer 106 and the lower line are connected between the power line and the ground line by connecting the power line and the ground line of the semiconductor chip to the upper electrode layer 106 and the plug 103B, for example. A thin film capacitor (decoupling capacitor) in which the dielectric layer 105 is formed can be inserted between the electrode layers 103. In this case, the thin film capacitor can stabilize the operation while suppressing fluctuations in the power supply voltage of the semiconductor chip.

  In the above structure, the lower electrode layer 103 may be omitted. In this case, the Ta layer 104 functions as an electrode (lower electrode layer) facing the upper electrode layer 106.

  The thin film capacitor 100 according to this embodiment is characterized in that the dielectric layer 105 includes a dielectric layer 105B made of a Ta oxide film layer (a layer containing Ta, oxygen, and carbon) containing C (carbon).

In the conventional thin film capacitor, the dielectric layer is formed of a Ta oxide film (Ta oxide, Ta ₂ O ₅ ), so that when the dielectric layer is heated, oxygen diffuses (desorbs) and the dielectric layer There was a case where the resistance value of the lowering. On the other hand, in the thin film capacitor 100 according to the present embodiment, since the dielectric layer 105 includes a dielectric layer 105B made of a Ta oxide film layer containing C, diffusion of oxygen in the dielectric layer 105 is suppressed and heated. Even if it is a case, it has the characteristic that an electrical property (electrical resistance etc.) is stable.

  The dielectric layer 105 further includes a dielectric layer 105A made of a Ta oxide film layer (a Ta oxide film layer to which C is not substantially added). That is, the dielectric layer 105 has a structure in which a dielectric layer 105A made of a Ta oxide film layer and a dielectric layer 105B made of a Ta oxide film layer containing C (a layer containing Ta, oxygen and carbon) are laminated. have.

  This is because when the dielectric layer 105 is formed, a Ta layer and a Ta layer to which C is added are stacked, and then oxidation is performed from the side of the Ta layer to which C is added by anodic oxidation. It is. Next, a method for manufacturing the thin film capacitor 100 including the method for forming the dielectric layer 105 will be described.

  FIG. 2A to FIG. 2G are diagrams for explaining the manufacturing method of the thin film capacitor 100 step by step. However, in the following drawings, the same reference numerals are given to the parts described above, and the description may be omitted.

  2A, an insulating layer 102 made of, for example, a silicon oxide film is formed on a substrate 101 made of, for example, Si so as to have a thickness of 300 nm.

  Next, in the step shown in FIG. 2B, a seed layer 103A made of, for example, Cu (thickness 500 nm) / Ta (thickness 50 nm) is formed on the insulating layer 102 by, for example, a sputtering method.

  Next, the lower electrode layer 103 is formed on the seed layer 103A so as to have a thickness of 10 μm by, for example, electrolytic plating of Cu using the seed layer 103A as a power feeding layer.

  Next, a Ta layer 104 is formed on the lower electrode layer 103 so as to have a thickness of 500 nm by sputtering using Ar gas, for example.

Next, a Ta layer 105b containing C is formed on the Ta layer 104 by, for example, a reactive sputtering method using Ar gas and CO ₂ gas so as to have a thickness of 100 nm. In this case, the material of the target used for sputtering with Ta, and the CO ₂ is added, for example, about 5% Ar gas used in sputtering, so that C is added to the film to be formed. In this case, oxygen is also added to the Ta layer 105b containing C.

Further, the gas added to the Ar gas is not limited to CO ₂ , and for example, other gas containing a C element may be used. Further, as a method of adding C, a material containing Ta and C may be used as a target.

  Further, the Ta layer 105b containing C may be formed by, for example, an evaporation method or a CVD method.

  Next, in the step shown in FIG. 2C, the Ta layer 105b containing C is oxidized by, for example, anodic oxidation (200V) to form a dielectric layer 105B made of a Ta oxide film layer containing C. In this case, at least a part of the Ta layer 104 is oxidized together with the Ta layer 105b containing C by the anodic oxidation in this step, and a Ta oxide film layer (a Ta oxide film layer substantially containing no C) is obtained. ) Dielectric layer 105A is formed. Here, a dielectric layer 105 is formed by laminating the dielectric layer 105A made of a Ta oxide film layer and the dielectric layer 105B made of a Ta oxide film layer containing C. In this case, when the anodic oxidation is performed so that the oxidation proceeds to the Ta layer 104, at least the Ta layer 105b containing C is surely oxidized, and the electric characteristics of the dielectric layer 105 are improved. Further, the dielectric constant of the dielectric layer 105A made of a Ta oxide film layer is higher than the dielectric constant of the dielectric layer 105B made of a Ta oxide film layer containing C. Therefore, the dielectric constant of the entire dielectric layer 105 can be increased by forming the dielectric layer 105A.

  In addition, as described above, since the dielectric layer 105B is formed to suppress a change in electrical characteristics after the dielectric layer 105 is heated, the dielectric layer 105B and the dielectric layer 105A are suppressed. And a dielectric layer having a high electric permittivity and a high dielectric constant can be formed.

  In this case, the Ta oxide film layer containing C means a film containing at least a Ta element, an O element, and a C element, and does not ask for a bonding state in a strict sense. In addition to these elements, impurities or additives may be contained.

  Next, in the step shown in FIG. 2D, the dielectric layer 105 is patterned by, for example, a dry etching method using a patterned mask so that the Ta layer 104 is partially exposed.

  2E, a seed layer 106A made of, for example, Cu (thickness 500 nm) / Ta (thickness 50 nm) is formed on the dielectric layer 105 by, for example, a sputtering method.

  Next, the upper electrode layer 106 is formed on the seed layer 106A so as to have a thickness of 10 μm, for example, by electrolytic plating of Cu using the seed layer 106A as a power feeding layer. Similarly, a substantially cylindrical plug 103B is formed so as to stand on the Ta layer 104 by, for example, Cu electrolytic plating.

  Next, in the step shown in FIG. 2F, the thin film capacitor 100 shown in FIGS. 1A and 1B is formed by grinding and thinning the substrate 101 to a required predetermined thickness (for example, about 50 μm). be able to.

  In the subsequent steps, as shown in FIG. 2G, for example, an insulating film (protective film) 107 may be formed so as to cover the thin film capacitor 100 as necessary. The insulating film 107 is formed of, for example, a material such as a photosensitive resist, and is formed by patterning so that a part of the upper surface of the plug 103B and a part of the upper electrode 106 are exposed for connection. . Thereafter, in order to increase the hardness of the insulating film 107, the entire wiring board 100 is heated at 200 ° C. for about 1 hour, for example.

  In this case, in the thin film capacitor 100 according to the present embodiment, the dielectric layer 105 includes the dielectric layer 105B made of a Ta oxide film layer containing C. Therefore, even when heated, the electrical characteristics (electric resistance, etc.) ) Is stable.

  Next, the results of examining the electrical characteristics of the thin film capacitor before and after heating will be described with reference to FIGS. 3A and 3B. FIG. 3A shows the results of examining the electrical characteristics (IV characteristics) of the above-described thin film capacitor 100 after capacitor formation and before heating (before heating in the process of FIG. 2G). On the other hand, FIG. 3B shows the result of examining the electrical characteristics in the same manner after the capacitor was formed (after heating at 200 ° C. for 1 hour, after the heating in the step of FIG. 2G).

  Referring to FIGS. 3A and 3B, it was confirmed that there was no substantial change in the IV characteristics of the capacitor before and after heating, and there was almost no change in the electrical characteristics of the dielectric layer due to heating.

  Further, for comparison with the above thin film capacitor 100, a comparative capacitor in which the dielectric layer 105B made of a Ta oxide film layer containing C was not formed in the thin film capacitor 100 was formed. In this case, the comparative capacitor has a structure in which the dielectric layer 105B is replaced with a Ta oxide film layer, and the other structure is the same as that of the thin film capacitor 100.

  FIG. 4A is a result of examining the electrical characteristics of the above-described comparative capacitor after the capacitor formation and before heating (equivalent to heating in the process of FIG. 2G). FIG. 4B shows the result of examining the electrical characteristics in the same manner after heating after capacitor formation (heating at 200 ° C. for 1 hour, equivalent to after heating in the step of FIG. 2G).

  4A and 4B, it can be seen that in the case of the above-described comparative capacitor, the leakage current increases after heating. This is presumably because the electrical characteristics of the dielectric layer made of the Ta oxide film layer have changed. As described above, various factors can be considered for changing the electrical characteristics of the dielectric layer. One of the possibilities is that oxygen in the Ta oxide film layer diffuses (desorbs oxygen). In the thin film capacitor according to this example, it is considered that such oxygen diffusion is suppressed.

  An example in which the thin film capacitor 100 described in the first embodiment is installed on a mounting substrate on which a semiconductor chip is actually mounted will be described below.

  FIG. 5A to FIG. 5C are diagrams illustrating the manufacturing method of the mounting board according to the second embodiment of the present invention, following the procedure. However, in the following drawings, the same reference numerals are given to the parts described above, and the description will be omitted.

  First, in the process shown in FIG. 5A, the thin film capacitor 100 is installed on the core substrate 201. In this figure, the dielectric layers 105A and 105B, the seed layers 103A and 106A and the like described in FIGS. 1A, 2F, and 2G are not shown (the same applies to the following drawings). In addition, a plurality of via plugs 201 penetrating the core substrate 201 are formed on the core substrate 201, for example.

  Next, in the step shown in FIG. 5B, for example, using a semi-additive method, the wiring portion 203A made of pattern wiring is formed on the side of the core substrate 201 where the thin film capacitor 100 is installed (hereinafter referred to as the first side). On the second side opposite to the first side of the core substrate 201, a wiring part 203B made of pattern wiring is formed.

  Next, an insulating layer (for example, a build-up layer made of resin) 204A is formed on the first side of the core substrate 201 so as to cover the thin film capacitor 100 and the wiring portion 203A. Similarly, an insulating layer 204B is formed on the second side of the core substrate 201.

  Next, a wiring portion 205A including a via plug penetrating the insulating layer 204A and a pattern wiring connected to the via plug is formed. Similarly, a wiring portion 205B is formed that includes a via plug that penetrates the insulating layer 204B and a pattern wiring connected to the via plug.

  In this case, the plurality of wiring portions 205A formed are connected to the wiring portion 204A, the upper electrode layer 106, the plug 103B, or the like.

  Next, in the step shown in FIG. 5C, an insulating layer (build-up layer) 206A is formed so as to cover the wiring part 205A, and similarly, an insulating layer 206B is formed so as to cover the wiring part 205B.

  Next, a wiring portion 207A including a via plug penetrating the insulating layer 206A and a pattern wiring connected to the via plug is formed. Similarly, a wiring portion 207B is formed that includes a via plug that penetrates the insulating layer 206B and a pattern wiring connected to the via plug.

  In this case, the via plug of the wiring unit 207A is connected to the pattern wiring of the wiring unit 205A, and similarly, the via plug of the wiring unit 207B is connected to the pattern wiring of the wiring unit 205B. It is formed.

  Next, a solder resist layer 208A is formed on the insulating layer 206A so as to have an opening through which a part of the wiring portion 207A is exposed. Further, a connection layer 209A made of, for example, a plating layer is formed on the exposed wiring portion 207A. Similarly, a solder resist layer 208B is formed on the insulating layer 206B so as to have an opening through which a part of the wiring portion 207B is exposed. Further, a connection layer 209B made of, for example, a plating layer is formed on the exposed wiring part 207B.

  In this manner, the mounting substrate 200 on which the semiconductor chip is mounted, in which the thin film capacitor 100 is incorporated, can be formed.

  In the mounting substrate 200, a semiconductor chip is mounted on the connection layer 209A. In this case, the thin film capacitors are connected via the wiring portions 207A and 205A so as to be inserted between the power supply line and the ground line of the semiconductor chip.

  In the mounting substrate 200 according to the present embodiment, since the thin film capacitor 100 is thinned and incorporated, it is possible to cope with the downsizing and thinning of the mounting substrate. In addition, since the electrical characteristics of the thin film capacitor 100 are stable, it is possible to efficiently stabilize the operation by suppressing fluctuations in the power supply voltage of the mounted semiconductor chip.

  FIG. 6 shows a semiconductor device according to Embodiment 3 of the present invention. However, in the figure, the same reference numerals are given to the parts described above, and the description will be omitted.

  Referring to FIG. 6, the semiconductor device 300 according to the present example has a structure in which a semiconductor chip 301 is mounted on the mounting substrate 200 described in the second example. The semiconductor chip 301 is mounted by electrically connecting solder bumps 302 formed on, for example, electrode pads (not shown) to the connection layer 209A.

  In this case, the thin film capacitors are connected via the wiring portions 207A and 205A so as to be inserted between the power supply line and the ground line of the semiconductor chip.

  In the semiconductor device 300 according to the present embodiment, since the thin film capacitor 100 is thinned and incorporated, it is possible to cope with the downsizing and thinning of the semiconductor device. In addition, since the electrical characteristics of the thin film capacitor 100 are stable, it is possible to efficiently stabilize the operation by suppressing fluctuations in the power supply voltage of the mounted semiconductor chip.

  In the above embodiment, the case where the dielectric layer 105 mainly includes the dielectric layer 105B made of a Ta oxide film layer (a layer containing Ta, oxygen, and carbon) containing C (carbon) has been described. It is not limited to this. For example, the dielectric layer 105B may be formed of an Nb oxide film layer (a layer containing Nb, oxygen, and carbon) containing C (carbon). In this case, since Ta and Nb have similar characteristics, it is possible to obtain the same effect as when Ta is used.

  Although the present invention has been described with reference to the preferred embodiments, the present invention is not limited to the specific embodiments described above, and various modifications and changes can be made within the scope described in the claims.

  According to the present invention, it is possible to provide a thin film capacitor having stable electrical characteristics, a manufacturing method for manufacturing the thin film capacitor, a mounting substrate using the thin film capacitor, and a semiconductor device using the thin film capacitor. Become.

1 is a cross-sectional view showing a thin film capacitor according to Example 1. FIG. 1 is a plan view showing a thin film capacitor according to Example 1. FIG. It is a figure (the 1) which shows the manufacturing method of the thin film capacitor of FIG. 1A. It is FIG. (2) which shows the manufacturing method of the thin film capacitor of FIG. 1A. It is FIG. (3) which shows the manufacturing method of the thin film capacitor of FIG. 1A. It is FIG. (4) which shows the manufacturing method of the thin film capacitor of FIG. 1A. It is FIG. (5) which shows the manufacturing method of the thin film capacitor of FIG. 1A. It is FIG. (6) which shows the manufacturing method of the thin film capacitor of FIG. 1A. FIG. 7B is a view (No. 7) showing a method for manufacturing the thin film capacitor of FIG. 1A; It is a figure (the 1) which shows the electrical property of a thin film capacitor. FIG. 6 is a second diagram illustrating electrical characteristics of the thin film capacitor. FIG. 6 is a third diagram illustrating electrical characteristics of the thin film capacitor. It is FIG. (4) which shows the electrical property of a thin film capacitor. FIG. 10 is a diagram (No. 1) illustrating a method for manufacturing a mounting board according to a second embodiment. FIG. 10 is a diagram (No. 2) illustrating the method for manufacturing the mounting board according to the second embodiment. FIG. 11 is a diagram (No. 3) illustrating the method for manufacturing the mounting board according to the second embodiment. 6 is a diagram showing a semiconductor device according to Example 3. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Thin film capacitor 101 Substrate 102 Insulating layer 103 Lower electrode layer 103A Seed layer 103B Plug 104 Ta layer 105, 105A, 105B Dielectric layer 106 Upper electrode layer 106A Seed layer 106B Opening 107 Insulating layer 200 Mounting substrate 201 Core substrate 202 Via plug 203A , 203B, 205A, 205B, 207A, 207B Wiring part 204A, 204B, 206A, 206B Insulating layer 208A, 208B Solder resist layer 209A, 209B Connection layer 300 Semiconductor device 301 Semiconductor chip 302 Solder bump

Claims (9)

A thin film capacitor in which a dielectric layer is formed between a first electrode layer and a second electrode layer,
The dielectric layer has a Ta oxide film layer containing C.   2. The thin film capacitor according to claim 1, wherein the dielectric layer further includes a Ta oxide film layer.   3. The thin film capacitor according to claim 1, wherein the Ta oxide film layer containing C is formed by anodizing a Ta layer containing C. A thin film capacitor comprising: a step of forming a first electrode layer; a step of forming a dielectric layer on the first electrode layer; and a step of forming a second electrode layer on the dielectric layer. A manufacturing method of
The step of forming the dielectric layer includes
A film forming step of forming a Ta layer containing C;
An oxidation step of oxidizing the Ta layer containing C, and a method of manufacturing a thin film capacitor. The film forming step includes
A first film forming step of forming a Ta layer on the first electrode layer;
5. The method of manufacturing a thin film capacitor according to claim 4, further comprising a second film forming step of forming a Ta layer containing C on the Ta layer.   6. The method of manufacturing a thin film capacitor according to claim 5, wherein the Ta layer and the Ta layer containing C are formed by a sputtering method.   7. The method of manufacturing a thin film capacitor according to claim 5, wherein in the oxidation step, at least a part of the Ta layer is oxidized together with the Ta layer containing C. A mounting substrate having a thin film capacitor connected to the semiconductor chip for mounting the semiconductor chip,
The thin film capacitor is
A mounting substrate, wherein a Ta oxide film layer containing C is formed between a first electrode layer and a second electrode layer. A semiconductor device having a thin film capacitor connected to a semiconductor chip, wherein the semiconductor chip is mounted on a mounting substrate,
The thin film capacitor is
A semiconductor device, wherein a Ta oxide film layer containing C is formed between a first electrode layer and a second electrode layer.

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