JP2009295719A - Through plug wire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing through plugs, which can suppress generation of problems that when plugs pierced through a semiconductor substrate chip are microfabricated, connection resistance with an electrode connected to the plugs is increased, a leak current may is increased, or insulation destruction or stress migration is generated. <P>SOLUTION: End parts of through plugs 350 for electrically connecting an electrode pad 400 formed on the surface of a semiconductor substrate 100 to a connection electrode 380 formed on the rear face of the substrate 100 are partially entered into the electrode pad 400 and the connection electrode 380. An insulating separation part 210 for insulating the through plugs 350 from the semiconductor substrate 100 is partially entered into an insulating film 205 formed on the surface side of the semiconductor substrate 100. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a structure of a through plug wiring, and more particularly, to a technique for forming a three-dimensional stacked LSI in which through plugs are provided in a plurality of semiconductor chips provided with circuits, and these are stacked and connected.

  In recent years, a three-dimensional LSI in which a plurality of semiconductor chips are stacked has been proposed. In the three-dimensional LSI, a through plug that penetrates the semiconductor substrate of each semiconductor chip is provided to electrically connect the stacked semiconductor chips.

  An example of the structure of a through plug that penetrates a semiconductor substrate used in a three-dimensional LSI is disclosed in Patent Document 1, for example. FIG. 18 is a plan view for explaining this structure, and FIG. 19 schematically shows a cross-sectional structure at a position AB in FIG. An insulating isolation region 200 is provided in part of the semiconductor substrate 100 so as to penetrate the substrate, and a through plug 300 penetrating the substrate is provided in the insulating isolation region. A three-dimensional LSI is configured by connecting electrodes provided on the upper and lower semiconductor chips to the upper and lower ends of the through plug exposed on the front and back sides of the semiconductor substrate.

As another through plug structure penetrating the semiconductor substrate, there is one described in Patent Document 2. FIG. 20 schematically illustrates a planar structure for explaining this structure. FIG. 21 schematically shows a cross-sectional structure at the position AB in FIG. A rectangular donut-shaped through plug 302 insulated and separated by an insulating film 202 is provided in a part of the semiconductor substrate 100 so as to penetrate the substrate, and the semiconductor substrate isolation region 101 surrounded by the rectangular donut-shaped through plug is provided in the semiconductor substrate isolation region 101. In addition, a linear through plug 301 insulated and separated by the insulating film 201 is provided. In the conventional example, the connection between the semiconductor chips is performed using both the rectangular donut-shaped through plug 302 and the linear through plug 301, and the connection between the semiconductor chips that input and output a large current such as a theoretical circuit is also supported. I can do it.
JP 2006-165025 A JP 2006-19431 A

  The through-plug having the conventional structure shown in FIGS. 18 to 21 is characterized in that a through-plug insulated and separated by an insulating film is provided so as to penetrate from the front surface side to the back surface side of the semiconductor substrate. To further emphasize, the conventional through plug is in contact with the insulating film and is provided so as to be surrounded by the insulating film.

  The insulating film has a function of insulating and separating the semiconductor substrate and the through plug. The electrical connection to the upper end and the lower end of the through plug is achieved by connecting the exposed end of the through plug to an electrode provided on the surface of another semiconductor chip using a metal such as a bump or a solder ball. Do.

  Since bumps or solder balls are used for electrical connection, the connection portion requires an area of about 60 to 100 microns. Therefore, the semiconductor chips are electrically connected to each other via the bonding pads (dimensions of about 100 microns square) used in the conventional semiconductor chip to realize a three-dimensional LSI.

  The miniaturization and densification of LSIs have been progressing year by year, and a technology capable of electrical connection with finer dimensions has been required even for through plugs used in three-dimensional LSIs. That is, there is a demand for a fine through plug technology for mutually connecting transistor circuits provided in different semiconductor chips. The dimension required for a fine through-plug is required to be at least 10 microns or less. In such a through-plug structure with such a fine dimension, the contact area with the electrode connected to the plug is the cross-sectional area of the through-plug. Since the connection is made with a small contact area, there is a disadvantage that connection resistance increases and connection failures frequently occur.

  Furthermore, when trying to miniaturize the through-plug having the conventional structure shown in FIG. 21, since the plug diameter that penetrates the semiconductor is desired to be as large as possible, the thickness of the insulating film 202 that insulates and isolates the through-plug 302 and the semiconductor substrate 100 is several It will be as thin as 100 nanometers or less. When the insulating film is thinned, the leakage current path 130 generated between the through plug and the semiconductor substrate increases, which causes serious problems such as malfunction of the LSI or failure of the LSI due to dielectric breakdown.

  On the other hand, if the insulating film 202 to be insulated and separated is provided with a sufficiently large thickness, the thermal expansion coefficient between the insulating film and the electrode material used for the through plug is large. Therefore, particularly in the vicinity of the upper end and the lower end of the through plug. It adds a lot of stress. As a result, the phenomenon (stress migration) in which the electrode material used for the through plug moves along the flow of current becomes remarkable, and a problem arises in that a cavity is formed in a part of the through plug and is disconnected. The disconnection due to the stress migration becomes more serious as the diameter of the through plug becomes smaller, and therefore becomes a very serious problem in a fine through plug wiring. Since disconnection due to stress migration occurs after a certain amount of time has elapsed, a failure occurs after the product is put on the market, so that the influence is extremely great in that the long-term reliability is significantly deteriorated.

  The present invention provides a through plug wiring that can reduce the connection resistance even when the diameter of the through plug is extremely small, has excellent insulation between the through plug and the semiconductor substrate, and has excellent long-term reliability characteristics. The purpose is that.

  According to the present invention, in a three-dimensional stacked LSI composed of a plurality of semiconductor chips provided with a circuit, the semiconductor substrate of the semiconductor chip is embedded in each of at least one hole penetrating according to the shape of the through plug. The through plug, the insulating isolation part embedded in the hole penetrating the semiconductor substrate in a shape surrounding the through plug, and the front and back surfaces of the semiconductor substrate connected to the through plug And a through-plug wiring characterized by comprising an electrode provided.

  Further, the through-plug wiring is characterized in that at least one of the electrodes provided on the front surface and the back surface of the semiconductor substrate has a buried structure in which a part of the through-plug is cut.

  Further, the through plug wiring is characterized in that the insulating film provided on the front and back surfaces of the semiconductor substrate has a buried structure in which a part of the insulating isolation portion is cut.

  Further, the through-plug wiring is characterized in that the cross-sectional shape of the hole through which the semiconductor substrate is passed in accordance with the shape of the through-plug is a line, a square or a circular shape.

  In addition, a conductive buffer film made of conductive polysilicon, a metal nitrogen compound, or a metal silicon compound is provided between the through-plug and the semiconductor substrate forming the through-hole side wall formed in the shape of the through-plug. This is a featured through plug wiring.

  The region of the semiconductor substrate surrounded by the insulating isolation part is a remaining region where a hole for embedding the through plug is removed, and is in contact with the through plug via the conductive buffer film or directly. This is a featured through plug wiring.

  According to the present invention, since the contact area with other electrodes connected to both end portions of the through plug can be increased, a through plug wiring structure with a fine dimension can be realized while keeping the connection resistance low.

  In addition, the through-plug wiring according to the present invention can realize a plug having a practically low connection resistance of 0.1 milliohm or less with good reproducibility even if the plug diameter is a fine plug of 10 microns or less. Therefore, it is possible to connect transistor circuit blocks between different semiconductor chips to each other and to connect the transistor circuits themselves to each other. Therefore, it is extremely effective for further increasing the density of the three-dimensional stacked LSI.

  According to the present invention, since the insulating film for insulating and separating the through plug and the semiconductor substrate can be provided with a sufficiently large thickness, the leakage current generated between the through plug and the semiconductor substrate is at a low level that does not cause a problem in practice. It can be suppressed, or dielectric breakdown can be prevented. Therefore, a high-quality and highly reliable three-dimensional stacked LSI is realized that prevents malfunction of the LSI and has few failures.

  Furthermore, since the through plug wiring according to the present invention is provided with a semiconductor substrate material between the through plug and the insulating isolation film, the stress applied to the through plug is small. For this reason, since a stress migration phenomenon can be prevented, there is an effect that even if the cross-sectional dimension of the through plug becomes fine, disconnection hardly occurs. Therefore, it is possible to provide a three-dimensional stacked LSI having excellent long-term reliability.

The structure of the through plug wiring according to the present invention and the manufacturing process will be described below with reference to the drawings.
(Embodiment of brother 1)

  FIG. 1 is a diagram for explaining the structure of a first through plug wiring according to the present invention, and is a plan view seen from the back side of a semiconductor substrate (all transistors, wirings, etc. are completed) provided with transistor circuits. The structure is shown schematically. In the figure, 100 is a semiconductor substrate, 210 is an insulation separation part, 101 is a semiconductor substrate region separated by the insulation separation part 210, 350 is a through plug, and 400 is provided on the surface of the semiconductor substrate (in the figure, on the back side of the paper). 2 shows electrode pads for transmitting signals to the inside and outside of the manufactured semiconductor chip.

  FIG. 2 schematically shows a cross-sectional structure at the position AB in FIG. In the figure, 110 is a region in which circuit elements such as a source and drain of a transistor are provided, 205 is an insulating film provided on the surface of the semiconductor substrate, 220 and 230 are the first insulating film and the second insulating film provided on the back surface of the semiconductor substrate. Two insulating films, 380, are connection electrodes that are connected to the through plugs 350, respectively. Note that the connection electrode 380 is omitted in FIG. 1 for easy explanation of the structure. In this example, the through plug 350 is made of a metal such as copper, nickel, or tungsten, a metal silicon compound, a metal nitrogen compound, or conductive polysilicon.

  The feature of the present invention is that the through plug 350 is provided so as to bite in the thickness direction of the electrode pad 400 provided on the front surface (lower side in FIG. 2) of the semiconductor substrate, and the rear surface (upper side in FIG. 2) of the semiconductor substrate. The electrode 380 is provided so as to bite in the thickness direction. With this structure, the contact area between the electrode pad 400 and the electrode 380 with respect to the through plug 350 can be increased, so that the contact resistance is kept sufficiently low.

  Furthermore, in the through plug wiring of the present invention, the through plug 350 is configured to contact the separated semiconductor substrate region 101. Although a silicon crystal is used for the semiconductor substrate, the silicon crystal has less stress on the through plug material than the insulating film. For this reason, the phenomenon of stress migration is unlikely to occur, and therefore a cavity is unlikely to occur in the through plug.

  Further, in the through plug wiring, the through plug 350 is in contact with the separated semiconductor substrate region 101, and the separated semiconductor substrate region 101 has the same potential as the through plug. Therefore, the separated semiconductor substrate region 101 also helps to reduce the through plug resistance.

In this embodiment, the insulating isolation part 210 is simply in contact with the insulating film 205 on the surface of the semiconductor substrate. When the thickness of the insulating isolation part 210 is several thousand angstroms or less, leakage occurs through the bonding interface of the film. The current path 140 is easily generated, and a leak current is generated between the through plug 350 and the semiconductor substrate 100. This phenomenon causes a short circuit or an unnecessary increase in power consumption, which significantly impairs the performance of the LSI. Or it causes breakdown by causing dielectric breakdown. A structure that prevents this is the second embodiment of the present invention shown in FIG.
(Embodiment of brother 2)

FIG. 3 is a diagram for explaining a second embodiment according to the present invention, and schematically shows a cross-sectional structure of the through wiring. In this embodiment, the insulating separation part 210 is provided so as to bite into the insulating film 205 on the surface of the semiconductor substrate. By adopting this structure, the leakage current generated in the conventional insulating separation film having fine dimensions can be suppressed to a level that does not impede practically. In addition, the insulating separation film 210 is also provided to penetrate into the first insulating film 220 on the back surface side of the semiconductor substrate, and the leakage current through the interface of the insulating film can be suppressed to a level that can be ignored in practice. .
(Embodiment of brother 3)

  In the through plug wiring having the structure shown in FIGS. 2 and 3, the through plug 350 is in contact with the separated semiconductor substrate region 101. When a metal material is used for the through plug 350, the metal material causes an abnormal reaction with silicon, which is a semiconductor substrate, during heat treatment at several hundred degrees Celsius, and a fine cavity is generated in the through plug and the semiconductor substrate in the vicinity thereof. There is a case. When such a cavity is generated, there arises a problem that the through plug is disconnected or the resistance is increased. Such a phenomenon depends on the type of metal material used for the through plug, but can be avoided by further devising the structure of the through plug.

  FIG. 4 shows a third embodiment in which the structure of the through plug is devised, and schematically shows a cross-sectional structure of the through wiring. In the figure, the same symbols as those in FIGS. 2 and 3 have the same function, and 352 is a conductive buffer film. This embodiment is characterized in that the periphery of the through plug 350 made of the first material is surrounded by the conductive buffer film 352 made of the second material. In such a structure, a material having a high conductivity such as copper, nickel, or tungsten is used as the material of the through plug, and a silicon compound material such as polysilicon and tungsten or tantalum, or tungsten, tantalum, or titanium is used as the conductive buffer film. The nitride material is used.

  Polysilicon, silicon compound materials, and nitride materials used for the conductive buffer film 352 have a property that the chemical reaction force with respect to silicon used for the semiconductor substrate is small. Since abnormal reactions are unlikely to occur, the generation of cavities and disconnections at the relevant portions are effectively prevented.

In this example, it has been described that polysilicon and silicon compound material such as tungsten or tantalum or nitride material such as tungsten, tantalum or titanium are used as the through plug material. However, a compound crystal such as GaAs is used as the semiconductor substrate. Needless to say, other materials that do not easily react may be used.
(Embodiment of brother 4)

FIG. 5 shows a fourth embodiment according to the present invention, and shows a planar structure viewed from the back side of the semiconductor substrate. In the figure, the same symbols as those in FIG. 1 denote the same functions. In this embodiment, the through plugs 350 are provided in a stripe shape, which has an effect of providing a wide contact area with the connected electrodes. Note that also in this structure, the cross-sectional structure taken along AB is the same as that in FIG.
(Embodiment of brother 5)

FIG. 6 shows a fifth embodiment according to the present invention, and shows a planar structure viewed from the back side of the semiconductor substrate. In the figure, the same symbols as those in FIG. 1 denote the same functions. In this embodiment, the through plug 350 is provided in a rectangular donut shape, and has an effect of allowing a large current to flow by widening the contact area with the connected electrode. It is obvious that the shape and the number of the through plugs can be freely selected as long as the contact area with the electrode provided thereon is not limited.
(Manufacturing process 1)

  The structure of the through plug according to the present invention is formed by the following manufacturing process. 7 to 15 are for explaining the process of forming the through plug wiring of the embodiment shown in FIG. 3, and show the sectional structure of the through plug wiring. First, in FIG. 7, a support substrate 500 is bonded using a resin 250 to the surface of a semiconductor substrate (transistors, wirings, and the like already manufactured) provided with a transistor circuit on the surface of the semiconductor substrate. Examples of preferable materials for the support substrate include glass and silicon. After the support substrate 500 is bonded, the back surface side (the upper side in FIG. 7) of the semiconductor substrate is ground and polished, so that the substrate has a desired thickness. A preferable thickness at this time is 30 to 300 microns.

  Next, in FIG. 8, after providing the first insulating film 220 on the back surface of the semiconductor substrate, a photoresist 600 is applied. Subsequently, for example, by using an exposure apparatus capable of alignment with infrared light, positioning is performed with respect to the electrode pad 400 provided on the surface of the semiconductor substrate, and exposure / development is performed, thereby surrounding a region where the through plug is to be provided. An opening pattern 221 is provided in a desired portion of the photoresist 600 in the portion. In addition to the method of aligning with infrared light, an optical pattern link method that stores the optical pattern on the back side in advance is also employed as the exposure apparatus used in this process.

  Next, in FIG. 9, the first insulating film 220 is selectively removed using the photoresist opening pattern 221 as a mask to form an opening pattern 222 of the insulating film.

  Next, in FIG. 10, the through hole 102 is dug into the semiconductor substrate 100 by using, for example, dry etching means with the hole pattern 222 of the first insulating film 220 as a mask. In this etching, the thickness of the semiconductor substrate 100 is dug, and further, the insulating film 205 is partially bitten. Good results were obtained when the amount of biting into the insulating film 205 was 0.02 to 0.2 microns.

  Next, in FIG. 11, an insulating film is embedded in the hole 102 to provide an insulating separation part 210. Preferable examples of the insulating film material include SiO 2 type, SiON type, and PSG type, and they are formed by a method such as a chemical vapor deposition method or a coating method. The insulating separation film 210 may be provided with a plurality of layers made of different materials in order to obtain sufficient insulation.

  Next, in FIG. 12, after the second insulating film 230 is provided on the back surface of the semiconductor substrate, the photoresist pad is positioned again with respect to the electrode pad 400 provided on the semiconductor substrate surface, and the through plug is inserted. An opening pattern 231 is provided in the second insulating film 230 at the position to be dug.

  Next, in FIG. 13, using the opening pattern 231 of the second insulating film 230 as a mask, the first insulating film 220, the semiconductor substrate 100, and the insulating film 205 are dug, and further in the thickness direction of the wiring pad 400. Also, a through hole 104 is provided by digging so as to partially bite. Good results were obtained when the amount of partial biting into the wiring pad 400 was 0.01 to 0.1 microns.

  Next, in FIG. 14, a conductive material is embedded in the through hole 104, and a through plug 350 is provided. Preferable examples of the conductive material include tungsten silicide, conductive polysilicon, and conductive paste, and any one can be selected freely.

  Next, in FIG. 15, a photoresist film 600 is provided, and the second insulating film 230 in the region including the end of the through plug 350 on the back surface side of the substrate is selectively removed by a method such as dry etching in the exposure process. A wiring connection region 105 is provided. Through this process, the end of the through plug 350 has a structure that greatly protrudes from the surface of the second insulating film 220. As a preferable overhang amount of this through plug, good results were obtained with 0.01 to 0.3 microns.

  Thereafter, using the photoresist pattern 600 as a mask, a metal electrode is selectively provided in the wiring connection region 105 by means such as electroless plating, and a connection electrode 380 is provided, and the through plug wiring structure shown in FIG. Is formed. Preferred materials for the connection electrode 380 are Al, Ni, Cu, and alloys containing them, and any one can be freely selected. Further, good results were obtained when the thickness of the connection electrode 380 was 0.5 to 2 microns.

In the above-described manufacturing process, it has been described that glass or silicon is used as the support substrate. However, a semiconductor chip may be used to adhere to the surface side on which the circuit is formed. In this case, it is necessary to align the position with respect to the circuit pattern of the semiconductor chip serving as the support substrate.
(Manufacturing process 2)

  The through plug wiring having the structure shown in FIG. 4 is formed by the following process. First, through the same steps as described in the embodiment of the younger brother 6 described above, the process up to the formation of the through hole 104 shown in FIG. Subsequently, as shown in FIG. 16, a conductive buffer film 352 is provided on the side wall of the formed through-hole 104 by means such as a CVD method or a sputter deposition method. As the material of the conductive buffer film, a silicon compound such as tungsten or tantalum, or a nitride such as tungsten, tantalum, or titanium is used. Such a film has an effect of preventing chemical reaction with silicon as a substrate, and a good result was obtained with a thickness of 0.01 to 0.2 microns.

  Next, as shown in FIG. 17, a through plug 350 is provided. As the material of the through plug, a highly conductive material such as copper, nickel, tungsten, or conductive polysilicon is used. Thereafter, the through plug wiring shown in FIG. 4 is formed through the same process as described in the embodiment of the younger brother 6 described above.

"Plan view explaining the structure of the first through plug wiring according to the present invention" "Cross-sectional view for explaining the structure of the first through plug wiring according to the present invention" “Cross sectional view for explaining the structure of the second through plug wiring according to the present invention” "Cross-sectional view illustrating the structure of the third through plug wiring according to the present invention" "Plan view explaining the structure of the fourth through plug wiring according to the present invention" "Plan view explaining the structure of the fourth through plug wiring according to the present invention" "Process sectional view 1 of through plug wiring of the present invention" "Process sectional view 2 of through-plug wiring of the present invention" "Process sectional view 3 of the through plug wiring of the present invention" "Process sectional view 4 of through plug wiring of the present invention" "Process sectional view 5 of through-plug wiring of the present invention" "Process sectional view 6 of through plug wiring of the present invention" "Process sectional view 7 of through plug wiring of the present invention" "Process sectional view 8 of through plug wiring of the present invention" "Process sectional view 9 of through plug wiring of the present invention" "Process sectional view 1 of other through plug wiring of the present invention" “Process sectional view 2 of another through plug wiring of the present invention” "Plan view explaining the structure of a conventional through wiring" "Cross-sectional view explaining the structure of a conventional through wiring" "Plan view explaining another structure of conventional through wiring" "Cross-sectional view explaining another structure of conventional through wiring"

Explanation of symbols

100 Semiconductor substrate
101 Isolated semiconductor substrate area
102, 104 Through hole
105 Wiring connection area
110 Area where circuit elements are provided
130, 140 Leakage current path
200 Isolation region
201, 202, 205 Insulating film
210 Isolation section
221, 222, 231 Opening pattern
220 First insulation film
230 Second insulation film
250 resin
300, 301, 302, 350 Through plug
352 Conductive buffer film
380 Connection electrode
400 wiring pads
500 Support substrate
600 photoresist

Claims (6)

In a three-dimensional stacked LSI composed of a plurality of semiconductor chips provided with a circuit,
The through plug embedded in each of at least one hole, penetrating the semiconductor substrate of the semiconductor chip according to the shape of the through plug; and
An insulating isolation part embedded in a hole provided through the semiconductor substrate in a shape surrounding all of the through plug;
Electrodes provided on the front and back surfaces of the semiconductor substrate connected to the through plug;
Through-plug wiring characterized by comprising.   The through plug wiring according to claim 1, wherein at least one of the electrodes has an embedded structure in which a part of the through plug is cut.   3. The through plug wiring according to claim 1, wherein the insulating film provided on the front surface and the back surface of the semiconductor substrate has a buried structure in which a part of the insulating isolation portion is cut.   The through plug wiring according to any one of claims 1 to 3, wherein a cross-sectional shape of a hole through which the semiconductor substrate passes through in accordance with a shape of the through plug is a line, a square shape, or a circular shape. .   A conductive buffer film made of conductive polysilicon, a metal nitrogen compound, or a metal silicon compound is provided between the through plug and the semiconductor substrate forming a through hole side wall formed in the shape of the through plug. The through plug wiring according to any one of claims 1 to 4.   The region of the semiconductor substrate surrounded by the insulating isolation part is a remaining region where a hole for embedding the through plug is removed, and is in contact with the through plug through the conductive buffer film or directly. The through plug wiring according to any one of claims 1 to 5.

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