JP2008108768A - Manufacturing method of semiconductor device - Google Patents

Abstract

Provided is a method for manufacturing a semiconductor device in which hydrogen can be sufficiently supplied to an interface between a gate insulating film of a transistor and a semiconductor substrate without increasing the processing temperature.
A method of manufacturing a semiconductor device according to the present invention includes a step of forming a transistor on a surface of a semiconductor substrate, and interlayer insulating films and 12 and wiring layers and 13 on the surface of the semiconductor substrate and on the transistor. And a step of forming a passivation film 14 on the uppermost wiring layer 13 and the interlayer insulating film 12. Before the step of forming the passivation film 14, the back surface of the semiconductor substrate 1 is formed. A film (for example, a diffusion prevention film 8) is formed. After the step of forming the passivation film 14, the step of removing the film from the back surface of the semiconductor substrate 1, and the gate insulating film of the transistor from the back surface of the semiconductor substrate 1. And supplying hydrogen to the interface of the semiconductor substrate 1.
[Selection] Figure 2

Description

  The present invention relates to a method for manufacturing a semiconductor device having a transistor. In particular, the present invention relates to a method for manufacturing a semiconductor device in which hydrogen can be sufficiently supplied to the interface between a gate insulating film of a transistor and a semiconductor substrate without increasing the processing temperature.

  FIG. 5 is a cross-sectional view of a conventional semiconductor device in which hydrogen sintering is performed. In the hydrogen sintering process, hydrogen is supplied to the interface between the gate insulating film of the transistor and the silicon substrate to reduce defects (silicon dangling bonds). The hydrogen sintering process is generally performed from the surface side of the semiconductor device (see, for example, Patent Document 1).

  In the semiconductor device illustrated in FIG. 5, a transistor including a gate insulating film 103 is formed on the surface of a silicon substrate 100. On the transistor and silicon substrate 100, a first interlayer insulating film 109 and a second interlayer insulating film 112 are stacked in this order. A first-layer Cu wiring 110 is embedded in the surface of the first interlayer insulating film 109, and a tungsten plug and a second-layer Cu wiring 113 are embedded in the second-layer interlayer insulating film 112. Yes. The interlayer insulating film 112 and the Cu wiring 113 are covered with a passivation film 114. The passivation film 114 has a film that is difficult for hydrogen to pass through, such as a silicon nitride film.

  In the interlayer insulating films 109 and 112, grooves for embedding the Cu wirings 110 and 113 are formed by etching. In each of the interlayer insulating films 109 and 112, etching stopper films 109b and 112b in an etching process for forming a groove are provided. As the etching stopper films 109b and 112b, a film that does not easily transmit hydrogen, such as a silicon nitride film, a silicon carbide film, or a silicon carbonitride film, is used.

  Further, a connection groove for connecting the Cu wiring 110 and a transistor (for example, the gate electrode 104) is formed on the bottom surface of the groove for embedding the Cu wiring 110, and on the bottom surface of the groove for embedding the Cu wiring 113. Is formed with a connection hole for connecting the Cu wiring 110 and the Cu wiring 113. These connection holes are formed by etching. On the interlayer insulating film 109, an etching stopper film 111 in an etching process for forming a connection hole is formed. As the etching stopper film 111, a film that does not easily transmit hydrogen, such as a silicon nitride film, a silicon carbide film, or a silicon carbonitride film, is used.

  Further, the trenches in which the Cu wirings 110 and 113 are embedded and the side walls of the connection holes are covered with diffusion preventing films 110a and 113a for preventing the diffusion of Cu. As the diffusion preventing films 110a and 113a, films that are difficult to transmit hydrogen, such as Ti, TiN, Ta, TaN, and MnSiO, are used.

  Further, the Cu wirings 110 and 113 are formed in the grooves and connection holes formed in the interlayer insulating films 109 and 112, and after the Cu film is formed on the interlayer insulating films 109 and 112 by the sputtering method and the plating method, It is formed by polishing and removing the Cu film located on 112. If Cu adheres to the back surface of the silicon substrate 100 in the process of forming the Cu film, since the diffusion coefficient of Cu in the silicon is high, Cu is supplied to the interface between the gate insulating film 103 and the silicon substrate 100, and the transistor characteristics deteriorate. To do. In order to prevent this, a diffusion prevention film 108 is formed on the back surface of the silicon substrate 100 before the interlayer insulating film 109 is formed.

JP-A-9-64194

  As described above, a plurality of films that do not easily transmit hydrogen, such as an etching stopper film, a diffusion prevention film, and a passivation film, are formed over the transistor. For this reason, in order to supply a sufficient amount of hydrogen from above the semiconductor substrate to the interface between the gate insulating film and the semiconductor substrate as in the prior art, it is necessary to increase the processing temperature (for example, 400 ° C.). When the processing temperature becomes high, a load is applied to components (for example, wiring) constituting the semiconductor device, so that the processing temperature is preferably low.

  The present invention has been made in consideration of the above-described circumstances, and an object of the present invention is to sufficiently supply hydrogen to the interface between the gate insulating film of the transistor and the semiconductor substrate without increasing the processing temperature. An object of the present invention is to provide a method for manufacturing a semiconductor device.

In order to solve the above problems, a method of manufacturing a semiconductor device according to the present invention includes a step of forming a transistor having a gate insulating film on a surface of a semiconductor substrate,
Forming at least one interlayer insulating film and a wiring layer on the surface of the semiconductor substrate and on the transistor;
Forming a passivation film on each of the uppermost wiring layer and the interlayer insulating film;
In a state where the step of forming the passivation film is completed, a film is formed on the back surface of the semiconductor substrate,
After the step of forming the passivation film,
Removing the film from the back surface of the semiconductor substrate;
Supplying hydrogen to the interface between the gate insulating film of the transistor and the semiconductor substrate by diffusing hydrogen into the semiconductor substrate from the back surface of the semiconductor substrate.

  According to this method for manufacturing a semiconductor device, since there is no film on the back surface of the semiconductor substrate in the step of supplying hydrogen, a sufficient amount from the back surface of the semiconductor substrate to the interface without increasing the processing temperature. Of hydrogen can be supplied.

  The step of forming the transistor includes, for example, a step of forming a gate insulating film, a step of forming a gate electrode on the gate insulating film, a step of forming an insulating film on and around the gate electrode, and the insulating Forming a sidewall covering the sidewall of the gate electrode by etching back the film. In this case, in the step of forming the insulating film, the film is formed on the back surface of the semiconductor substrate.

  Before the step of forming the interlayer insulating film and the wiring layer, the method includes the step of forming the film on the back surface of the semiconductor substrate in order to prevent metal impurities from diffusing into the transistor through the semiconductor substrate. May be. The passivation film includes a film having a low hydrogen permeability, such as a silicon nitride film.

  When the interlayer insulating film and the wiring layer are each formed in two or more layers, the step of forming the interlayer insulating film and the wiring layer includes, for example, a step of forming the first interlayer insulating film, Forming an etching stopper film on the interlayer insulating film, forming a second interlayer insulating film on the etching stopper film, forming a groove on the second interlayer insulating film, and A step of forming a connection hole in the bottom surface of the groove by etching using an etching stopper film as a stopper, and a step of forming a wiring by embedding a conductor in the groove and the connection hole. In this case, the etching stopper film may include a film having a low hydrogen permeability, for example, at least one of a silicon nitride film, a silicon carbide film, and a silicon carbonitride film.

A step of forming a diffusion prevention film on at least the side wall of the groove between the step of forming a connection hole in the bottom surface of the groove and the step of forming a wiring by embedding a conductor in the groove and the connection hole; May be. The diffusion preventing film may include a film having a low hydrogen permeability, such as a Ti film and a TiN film, a Ta film and a TaN film, or a MnSiO film.
The step of supplying hydrogen from the back surface of the semiconductor substrate to the gate interface of the transistor is performed using, for example, a batch type thermal diffusion furnace. When a batch type thermal diffusion furnace is used, hydrogen can be supplied to the interface also from the surface of the semiconductor device.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. 1 and 2 are views for explaining a method of manufacturing a semiconductor device according to the first embodiment of the present invention. In the present embodiment, a semiconductor device is formed on the surface of a silicon substrate, and then a film formed on the back surface of the silicon substrate is removed, and then a hydrogen sintering process is performed using a batch-type thermal diffusion furnace. In this method, hydrogen is supplied from the back and front surfaces of the transistor to the interface between the gate insulating film of the transistor and the semiconductor substrate.

  First, as shown in the cross-sectional view of FIG. 1A, an element isolation film 2 is embedded in the surface of the silicon substrate 1 using a trench isolation method, and an element region in which a transistor is formed is isolated from other regions. . The element isolation film 2 is formed of a silicon oxide film. The element isolation film 2 may be formed by a LOCOS oxidation method. Next, the silicon substrate 1 is thermally oxidized. Thereby, the gate insulating film 3 is formed on the silicon substrate 1 located in the element region.

  Next, a polysilicon film is formed on the gate insulating film 3, and this polysilicon film is selectively removed. Thereby, the gate electrode 4 is formed on the gate insulating film 3. In the step of forming the polysilicon film, a polysilicon film (not shown) is also formed on the back surface of the silicon substrate 1.

  Next, impurities are introduced into the silicon substrate 1 using the element isolation film 2 and the gate electrode 4 as a mask. Thereby, a low concentration impurity region 6 is formed in the silicon substrate 1. Next, an insulating film (for example, a laminated film of a silicon oxide film and a silicon nitride film) is formed on the entire surface including on the gate electrode 4, and this insulating film is etched back. Thereby, the side wall of the gate electrode 4 is covered with the side wall 5. In the step of forming an insulating film to be a sidewall, an insulating film is also formed on the back surface of the silicon substrate 1.

Next, impurities are introduced into the silicon substrate 1 using the element isolation film 2, the gate electrode 4, and the sidewalls 5 as a mask. As a result, two impurity regions 7 serving as a source and a drain are formed in the silicon substrate 1.
In this way, a transistor is formed on the surface of the silicon substrate 1.

  Next, as shown in the cross-sectional view of FIG. 1B, a diffusion prevention film 8 is formed on the back surface of the silicon substrate 1. The diffusion prevention film 8 is a film in which, for example, a silicon oxide film and a silicon nitride film are laminated in this order, and metal impurities such as Cu adhering to the back surface of the silicon substrate 1 diffuse in the silicon substrate 1 in a wiring formation process to be described later. This is a film for preventing this.

  Next, an insulating film 9a constituting the interlayer insulating film 9 is formed on the entire surface including the top of the transistor. Next, a resist pattern (not shown) is formed on the insulating film 9a, and the insulating film 9a is etched using this resist pattern as a mask. Thereby, a connection hole located on the transistor (for example, on the gate electrode 4) is formed in the insulating film 9a. Thereafter, the resist pattern is removed. Next, a barrier metal film is formed in the connection hole and on the insulating film 9a, and a tungsten film is further formed on the barrier metal film. Next, the barrier metal film and the tungsten film located on the insulating film 9a are polished and removed by the CMP method. Thereby, the barrier metal film 15a and the tungsten plug 15 are buried in the connection hole.

  Next, an etching stopper film 9b is formed on the tungsten plug 15 and the insulating film 9a, and an insulating film 9c constituting the interlayer insulating film 9 is further formed on the etching stopper film 9b. Next, a resist pattern (not shown) is formed on the insulating film 9c, the insulating film 9c is etched using the resist pattern as a mask, and the etching stopper film 9b is etched under different etching conditions. Thereby, a groove located on the tungsten plug 15 is formed in the insulating film 9c. The tungsten plug 15 is exposed at the bottom of the groove. Thereafter, the resist pattern is removed.

  Next, a barrier metal film 10a is formed in the trench and on the insulating film 9c, and a Cu film is further formed on the barrier metal film 10a by sputtering and plating. Next, the barrier metal film 10a and the Cu film located on the insulating film 9c are polished and removed by the CMP method. Thus, the barrier metal film 10a and the Cu wiring 10 are embedded in the trench.

  Next, as shown in the cross-sectional view of FIG. 1C, an etching stopper film 11 is formed over the insulating film 9c and the wiring 10. The etching stopper film 11 is, for example, a silicon nitride film, a silicon carbide film, or a silicon carbonitride film. Next, an insulating film 12a, an etching stopper film 12b, and an insulating film 12c constituting the second interlayer insulating film 12 are formed on the etching stopper film 11 in this order.

  Next, a groove is formed in the insulating film 12c, and a connection hole is formed in the etching stopper film 12b and the insulating film 12a. The method for forming the groove and the connection hole is the same as the method for forming the groove and the connection hole in the interlayer insulating film 9 except that the step of forming the barrier metal film and the tungsten plug film is omitted. In the step of forming the connection hole, the etching stopper film 11 functions as an etching stopper. Next, a diffusion prevention film 13 a is formed in the groove and the connection hole of the interlayer insulating film 12, and the second-layer wiring 13 is embedded. The formation method of the diffusion prevention film 13a and the wiring 13 is substantially the same as the formation method of the diffusion prevention film 10a and the wiring 10. However, the wiring 13 and the diffusion preventing film 13a are also embedded in the connection hole formed in the insulating film 12a.

  Next, a passivation film 14 is formed on the interlayer insulating film 12 and the wiring 13. The passivation film 14 is a film in which, for example, a silicon oxide film and a silicon nitride film are stacked in this order.

  Next, all the films (including the diffusion prevention film 8) formed on the back surface of the silicon substrate 1 are removed. For this removal, for example, wet etching or dry etching is used.

  Next, as shown in the longitudinal sectional view of FIG. 2A, the silicon substrate 1 is inserted into a batch-type thermal diffusion furnace 50, and hydrogen sintering is performed. The inside of the processing chamber 51 of the thermal diffusion furnace 50 is a hydrogen atmosphere, and the inside is heated by a heater 53 arranged around the atmosphere. A heat retaining unit 54 is located on the bottom surface of the processing chamber 51. A wafer board 52 is disposed on the heat retention unit 54. The wafer board 52 holds a plurality of silicon substrates 1 separated from each other. In a state of being held on the wafer board 52, the front surface side of the silicon substrate 1 is exposed to a hydrogen atmosphere, and the back surface is exposed to a hydrogen atmosphere except for a very small part in contact with the wafer board 52.

  The cross-sectional view of FIG. 2B is a cross-sectional view of the semiconductor device for explaining how hydrogen diffuses in the hydrogen sintering process. As described above, during the hydrogen sintering process, most of the back surface is exposed to the hydrogen atmosphere. All the films formed on the back surface of the silicon substrate 1 are removed. Moreover, the diffusion coefficient of hydrogen in silicon is sufficiently large. Therefore, hydrogen diffuses from the back surface of the silicon substrate 1, and a sufficient amount of hydrogen is supplied to the interface between the gate insulating film 3 and the silicon substrate 1. Since the surface side of the silicon substrate 1 is also exposed to the hydrogen atmosphere, hydrogen is supplied to the above-mentioned interface also from the surface side.

  FIG. 3 is a graph showing the processing temperature dependence of the interface state when the hydrogen sintering process is performed by the method shown in the present embodiment. For comparison, the processing temperature dependence of the interface state when the film on the back surface of the silicon substrate 1 is not removed is also shown. The vertical axis is a relative value where the interface state is 1 when the hydrogen sintering treatment is not performed.

  When the film on the back surface of the silicon substrate 1 is not removed, the processing temperature needs to be 400 ° C. or higher in order to make the interface state 0.3 or lower. On the other hand, according to the present embodiment, the interface state is 0.3 or less even when the processing temperature is 350 ° C. or less. From this figure, according to the present embodiment, it can be seen that the processing temperature can be lowered as compared with the conventional one.

  As described above, according to the first embodiment of the present invention, all the films formed on the back surface of the silicon substrate 1 are removed before performing the hydrogen sintering process. Therefore, hydrogen diffuses from the back surface of the silicon substrate 1, and a sufficient amount of hydrogen is supplied to the interface between the gate insulating film 3 and the silicon substrate 1 without performing the hydrogen sintering process at a high temperature.

  FIG. 4 is a cross-sectional view for explaining the method for manufacturing a semiconductor device according to the second embodiment of the present invention. The method of manufacturing a semiconductor device according to the present embodiment includes a point that an etching stopper film is not formed in the interlayer insulating films 9 and 12, a point that only a connection hole is formed in the interlayer insulating film 9 without forming a groove, and an interlayer insulating film The tungsten plug 10b is embedded in the connection hole formed in 9 to electrically connect the transistor and the wiring 10, and the tungsten plug 13b is embedded in the connection hole formed in the interlayer insulating film 12 to connect the wirings 10 and 13 to each other. Diffusion prevention film on the point of electrical connection, the point that the wirings 10 and 13 are not embedded in the interlayer insulating films 9 and 12 and are formed using Al alloy, and the side wall of the connection hole and the back surface of the silicon substrate 1 This is different from the first embodiment in that is not formed. Hereinafter, the same components as those of the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

  In the present embodiment, the tungsten plugs 10b and 13b are formed by forming a tungsten film in the connection hole and on the interlayer insulating films 9 and 12, and then polishing and removing the tungsten film located on the interlayer insulating films 9 and 12 by CMP. It is formed by. The wiring 10 is formed by forming an Al alloy film on the interlayer insulating film 9 and the tungsten plug 10b by sputtering, and then selectively removing the Al alloy film. The wiring 13 is also formed by the same method as the wiring 10.

  According to this embodiment, the same effect as that of the first embodiment can be obtained. In addition, since the wirings 10 and 13 are made of an Al alloy having a lower melting point than Cu, the superiority of the present invention becomes more remarkable.

  Note that the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention. For example, in each of the above embodiments, the wiring layer and the interlayer insulating film are each two layers, but each may be three or more layers. In such a case, hydrogen becomes more difficult to diffuse from the surface side of the semiconductor device, so that the superiority of the present invention becomes more remarkable. In the above-described embodiment, the hydrogen sintering process is performed using batch thermal diffusion, but a furnace single wafer hydrogen sintering apparatus may be used.

FIGS. 6A to 6C are cross-sectional views for explaining a method for manufacturing a semiconductor device according to the first embodiment. FIGS. (A) is a longitudinal cross-sectional view of the thermal diffusion furnace 50 when performing a hydrogen sintering process, and (B) is a cross-sectional view of a semiconductor device for explaining how hydrogen diffuses in the hydrogen sintering process. The graph which shows the process temperature dependence of an interface state at the time of performing a hydrogen sintering process by the method shown in 1st Embodiment. Sectional drawing for demonstrating the manufacturing method of the semiconductor device which concerns on 2nd Embodiment. FIG. 5 is a cross-sectional view of a conventional semiconductor device in which hydrogen sintering is performed.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,100 ... Silicon substrate, 2 ... Element isolation film, 3,103 ... Gate insulating film, 4,104 ... Gate electrode, 5 ... Side wall, 6 ... Low concentration impurity region, 7 ... Impurity region, 8, 10a, 13a 110a, 113a ... Diffusion prevention film, 9, 12, 109, 112 ... Interlayer insulating film, 9a, 9c, 12a, 12c ... Insulating film, 9b, 11, 12b, 109b, 112b, 111 ... Etching stopper film, 10, DESCRIPTION OF SYMBOLS 13 ... Wiring, 10b, 13b, 15 ... Tungsten plug, 14, 114 ... Passivation film, 15a ... Barrier metal film, 50 ... Thermal diffusion furnace, 51 ... Processing chamber, 52 ... Wafer board, 53 ... Heater, 54 ... Heat retention Unit, 110, 113 ... Cu wiring

Claims (9)

Forming a transistor having a gate insulating film on a surface of a semiconductor substrate;
Forming at least one interlayer insulating film and a wiring layer on the surface of the semiconductor substrate and on the transistor;
Forming a passivation film on each of the uppermost wiring layer and the interlayer insulating film;
In a state where the step of forming the passivation film is completed, a film is formed on the back surface of the semiconductor substrate,
After the step of forming the passivation film,
Removing the film from the back surface of the semiconductor substrate;
Supplying hydrogen to the interface between the gate insulating film of the transistor and the semiconductor substrate by diffusing hydrogen into the semiconductor substrate from the back surface of the semiconductor substrate;
A method for manufacturing a semiconductor device comprising: The step of forming the transistor comprises:
Forming a gate insulating film on the surface of the semiconductor substrate;
Forming a gate electrode on the gate insulating film;
Forming an insulating film on and around the gate electrode;
Forming a sidewall covering the sidewall of the gate electrode by etching back the insulating film;
Comprising
The method for manufacturing a semiconductor device according to claim 1, wherein in the step of forming the insulating film, the film is formed on a back surface of the semiconductor substrate.   Before the step of forming the interlayer insulating film and the wiring layer, the method includes the step of forming the film on the back surface of the semiconductor substrate in order to prevent metal impurities from diffusing into the transistor through the semiconductor substrate. A method for manufacturing a semiconductor device according to claim 1.   The method for manufacturing a semiconductor device according to claim 1, wherein the passivation film includes a silicon nitride film. The interlayer insulating film and the wiring layer are each formed in two or more layers,
The step of forming the interlayer insulating film and the wiring layer includes:
Forming a first interlayer insulating film;
Forming an etching stopper film on the first interlayer insulating film;
Forming a second interlayer insulating film on the etching stopper film;
Forming a groove on the second interlayer insulating film and forming a connection hole on a bottom surface of the groove by etching using the etching stopper film as a stopper;
Forming a wiring by embedding a conductor in the groove and the connection hole;
The manufacturing method of the semiconductor device as described in any one of Claims 1-4 which comprises these.   6. The method of manufacturing a semiconductor device according to claim 5, wherein the etching stopper film includes at least one of a silicon nitride film, a silicon carbide film, and a silicon carbonitride film.   A step of forming a diffusion prevention film on at least the side wall of the groove between the step of forming a connection hole in the bottom surface of the groove and the step of forming a wiring by embedding a conductor in the groove and the connection hole; A method for manufacturing a semiconductor device according to claim 5 or 6.   The method of manufacturing a semiconductor device according to claim 7, wherein the diffusion prevention film includes a Ti film and a TiN film, a Ta film and a TaN film, or a MnSiO film.   The method for manufacturing a semiconductor device according to claim 1, wherein the step of supplying hydrogen from the back surface of the semiconductor substrate to the gate interface of the transistor is performed using a batch type thermal diffusion furnace.

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