JP2005322745A - Semiconductor element, method for manufacturing the same, solid-state imaging element, and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor element which is easily manufactured with a good yield, a method for manufacturing the semiconductor element, a solid-state imaging element, and a method for manufacturing the solid-state imaging element. <P>SOLUTION: In the semiconductor element, a circuit element or a wiring region is formed on the surface side of a semiconductor layer, a supporting substrate is bonded onto the surface side, and a protective film is formed on the surface or the like of the wiring region on the side of the supporting substrate. In the solid-state imaging element, the wiring region is formed on the surface side of a semiconductor layer 13 having a light receiver PD formed thereon, a supporting substrate 20 is bonded onto the surface side, a protective film 16 is formed on a surface or the like of a wiring region on the side of the supporting substrate 20, and light is directed thereinto from its rear surface side. Upon manufacturing these elements, the supporting substrate 20 is bonded to a substrate having the protective film 16 formed thereon and subjected to wet etching to make the substrate thin. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to a semiconductor element having a circuit element formed on a semiconductor substrate and a method for manufacturing the semiconductor element. In particular, it is suitable for application to a semiconductor element having a structure in which a multilayer wiring layer is formed on a semiconductor substrate.
The present invention also relates to a solid-state imaging device having a configuration in which light is irradiated from the back surface side, a so-called back-illuminated structure, and a method for manufacturing the solid-state imaging device.

As semiconductor devices become highly integrated, transistors and other semiconductor elements tend to be further reduced to further increase the packaging density.
For this reason, even in a CMOS sensor (CMOS type solid-state imaging device), it is required to miniaturize a pixel and highly integrate the device.

  However, in the conventional CMOS sensor, the light receiving sensor unit is irradiated with light from the lens formed on the wiring unit and detected through the wiring layer. As the device becomes finer, vignetting of incident light occurs due to obstacles such as a wiring layer, so the aperture ratio of the light receiving sensor portion is reduced, and sufficient light cannot be irradiated to the light receiving sensor portion. . For this reason, the problem that a sensitivity falls or a shading becomes large also arises.

Therefore, by irradiating the light receiving sensor part with light from the back side (the side opposite to the wiring part), it becomes possible to achieve an effective aperture ratio of 100% without being affected by obstacles such as a wiring layer, The sensitivity can be greatly increased.
For this reason, development of a so-called back-illuminated CMOS sensor, which is configured to irradiate light to the light-receiving sensor unit from the back side (the side opposite to the wiring unit), has been performed.

In a back-illuminated image sensor, in order to increase the light detection sensitivity and obtain high sensitivity, it is considered to thin the semiconductor substrate on which the light receiving sensor portion is formed (for example, Patent Document 1 or Patent). Reference 2).
JP-A-6-77461 (FIG. 3) JP-A-6-283702 (FIG. 2)

  However, when the semiconductor substrate on which the light receiving sensor portion is formed is thin, flatness cannot be obtained due to the stress inherent to the substrate, and mechanical strength is weakened.

Therefore, in order to obtain flatness and mechanical strength, it can be considered that the support substrate is bonded to the semiconductor substrate before the semiconductor substrate is thinned.
That is, after the semiconductor substrate and the support substrate are bonded together in a wafer state, the semiconductor substrate is thinned.

  However, when a back-illuminated solid-state imaging device is manufactured by the method of thinning the semiconductor substrate after bonding the support substrate to the semiconductor substrate as described above, the following problems occur.

As a method of thinning the semiconductor substrate, for example, wet etching can be employed.
By employing wet etching, the thickness of the semiconductor substrate can be accurately controlled.

However, even if the wet etching chemical solution is exposed only to the back side of the semiconductor substrate, the chemical solution also circulates to the edge portion of the wafer. Therefore, at this edge portion, the interlayer oxide film formed on the semiconductor substrate, the support substrate, and the semiconductor substrate The adhesive layer or the like used for bonding to the support substrate is etched and damaged by the chemical solution.
This causes problems such as peeling of the semiconductor substrate, surface roughness of the edge portion of the support substrate, and reduction of the substrate diameter.

  For the reasons described above, it is difficult to manufacture a solid-state imaging device having a back-illuminated structure by thinning a semiconductor substrate on which a semiconductor region or the like of a light receiving sensor portion is formed.

In addition to a solid-state imaging device having a back-illuminated structure, it is conceivable to form a multilayer wiring layer on a semiconductor substrate on which circuit elements are formed in a semiconductor element.
When manufacturing such a semiconductor element, for example, the semiconductor substrate on which the circuit element is formed may be thin for the purpose of obtaining desired characteristics in the circuit element such as a transistor.
Accordingly, even in such a case, the same problem as in the case of manufacturing a solid-state imaging device having a back-illuminated structure occurs.

  In order to solve the above-described problems, the present invention provides a semiconductor device and a manufacturing method thereof, a solid-state imaging device and a manufacturing method thereof that can be easily manufactured with a high yield.

  In the semiconductor element of the present invention, a circuit element is formed near the surface of the semiconductor layer, a wiring portion having a wiring layer in an insulating layer is formed on the surface side of the semiconductor layer, and a support substrate is further provided on the surface side of the wiring portion. A protective film made of a material having an etching selectivity with respect to the semiconductor layer is formed on at least the surface of the wiring portion on the support substrate side.

  The method for manufacturing a semiconductor element of the present invention includes a step of forming a circuit element near the surface of a semiconductor layer of a substrate having a semiconductor layer, and forming a wiring portion having a wiring layer in an insulating layer on the surface side of the semiconductor layer; Thereafter, in the wafer in which the wiring portion is formed in the semiconductor layer, the wafer is made of a material that covers at least one of the main surface of the front surface and the outer surface of the edge portion and can have an etching selectivity with the semiconductor layer. The method includes a step of forming a protective film, a step of bonding a support substrate to the further surface side of the wiring portion, and a step of thinning the substrate, and performing wet etching with an etchant in the step of thinning the substrate.

  In the solid-state imaging device of the present invention, a wiring part having a wiring layer in an insulating layer is formed on the surface side of the semiconductor layer on which the light receiving part is formed, and light is incident from the back side opposite to the surface side of the semiconductor layer. A protective substrate made of a material capable of obtaining an etching selectivity with respect to the semiconductor layer is formed on at least the surface of the wiring portion on the support substrate side. It is what.

  The method for manufacturing a solid-state imaging device of the present invention includes a step of forming a light receiving portion in the semiconductor layer of a substrate having a semiconductor layer, and a step of forming a wiring portion having a wiring layer in an insulating layer on the surface side of the semiconductor layer. Then, in the wafer in which the wiring portion is formed in the semiconductor layer, from a material that covers at least one of the main surface of the front surface and the outer surface of the edge portion and has an etching selectivity with the semiconductor layer. A step of forming a protective film, a step of adhering a support substrate to the further surface side of the wiring portion, and a step of thinning the substrate, and performing wet etching with an etchant in the step of thinning the substrate. .

According to the configuration of the semiconductor element of the present invention described above, the circuit element is formed in the vicinity of the surface of the semiconductor layer, and the wiring portion having the wiring layer in the insulating layer is formed on the surface side of the semiconductor layer. Since the support substrate is bonded to the front surface side, the strength of the chip of the semiconductor element can be ensured by the support substrate even if the semiconductor layer is thinned.
Further, a protective film made of a material capable of taking an etching selectivity with the semiconductor layer is formed on at least the surface of the wiring portion on the support substrate side, so that in the wet etching process when manufacturing the semiconductor element of this configuration, It is possible to protect at least the wiring portion from being etched by the protective layer.

  According to the method for manufacturing a semiconductor element of the present invention described above, the circuit element is formed near the surface of the semiconductor layer of the substrate having the semiconductor layer, and the wiring portion having the wiring layer in the insulating layer is formed on the surface side of the semiconductor layer. In the wafer having the wiring portion formed in the semiconductor layer and then forming the wiring portion, the etching selectivity with respect to the semiconductor layer covers at least one of the main surface of the table and the outer surface of the edge portion. A step of forming a protective film made of a removable material, a step of adhering a support substrate to the further surface side of the wiring portion, and a step of thinning the substrate, and performing wet etching with an etchant in the step of thinning the substrate Thus, when the substrate is thinned by performing wet etching with an etching solution, at least the wiring portion or the edge portion of the wafer is not etched by the protective film formed earlier. It is possible to protect the.

According to the above-described configuration of the solid-state imaging device of the present invention, the wiring portion having the wiring layer in the insulating layer is formed on the surface side of the semiconductor layer where the light receiving portion is formed, and is opposite to the surface side of the semiconductor layer. Since it has a structure in which light is incident from the back side, a so-called back side illumination type structure is formed.
In addition, since the support substrate is bonded to the further surface side of the wiring portion, the strength of the chip of the solid-state image sensor can be secured by the support substrate even if the semiconductor layer is thinned.
Furthermore, a protective film made of a material capable of obtaining an etching selectivity with respect to the semiconductor layer is formed on at least the surface of the wiring portion on the support substrate side, so that in a wet etching process when manufacturing a solid-state imaging device having this configuration The protective layer can protect at least the wiring portion from being etched.

  According to the above-described method for manufacturing a solid-state imaging device of the present invention, the step of forming the light receiving portion in the semiconductor layer of the substrate having the semiconductor layer, and the wiring portion having the wiring layer in the insulating layer on the surface side of the semiconductor layer And, in the wafer having the wiring portion formed in the semiconductor layer, and covering at least one of the main surface of the front surface and the outer surface of the edge portion, the etching selectivity with the semiconductor layer A step of forming a protective film made of a material that can be removed, a step of bonding a support substrate to the further surface side of the wiring portion, and a step of thinning the substrate. In the step of thinning the substrate, wet etching with an etchant is performed. By doing so, it is possible to manufacture a solid-state imaging device having a so-called back-illuminated structure in which light is incident from the back side opposite to the wiring layer of the semiconductor layer in which the light receiving portion is formed, and to etch When thinning the substrate by performing a wet etching by a liquid, with the protection film formed previously can be edge portions of at least the wiring portion or wafer is protected from being etched.

Further, in the above-described semiconductor element and semiconductor device manufacturing method, solid-state imaging element, and solid-state imaging element manufacturing method of the present invention, the semiconductor layer can be a silicon layer and the protective film can be made of silicon nitride.
In this configuration, silicon nitride is a material that can take an etching selection ratio with silicon, and at least the wiring portion can be protected from being etched by the protective film made of silicon nitride.

In the semiconductor element and the solid-state imaging element of the present invention described above, a protective film made of a material that can have an etching selectivity with respect to the semiconductor layer can be formed on both surfaces of the support substrate. .
When this structure is adopted, the support substrate can be protected from being etched by the protective film.

Further, in the semiconductor element of the present invention described above, a structure in which a wiring portion having a wiring layer is formed in the insulating layer on the back surface opposite to the front surface side of the semiconductor layer, and a circuit is also provided near the back surface of the semiconductor layer. A structure in which an element is formed may be employed.
Similarly, in the semiconductor element manufacturing method of the present invention described above, after thinning the substrate, forming a wiring portion having a wiring layer in the insulating layer also on the back surface side opposite to the front surface side of the semiconductor layer, Further, it is possible to form a circuit element near the back surface of the semiconductor layer.
With these structures, the number of wiring layers and circuit elements per unit area can be increased, and the semiconductor element can be highly integrated.

Further, in the above-described semiconductor element and semiconductor device manufacturing method of the present invention, the support substrate includes a semiconductor substrate on which a circuit element is formed, and a wiring portion having a wiring layer in an insulating layer, and the wiring portion of the support substrate. Can be arranged on the bonding surface side.
In this configuration, since circuit elements and wiring layers are also formed on the support substrate, the number of wiring layers and circuit elements per unit area can be increased, and high integration of semiconductor elements can be achieved. Is possible.

Further, in the above-described semiconductor element and the manufacturing method of the semiconductor element, the solid-state imaging element, and the manufacturing method of the solid-state imaging element, the support substrate is bonded by the adhesive layer, and the etching selectivity of the semiconductor layer can be obtained by the adhesive layer. It can be made of a material.
When this structure is adopted, it is possible to prevent the adhesive layer from being etched and peeled off by the etching solution.
Furthermore, by bonding using the adhesive layer as an organic coating film, the adhesive layer can be easily formed on the entire wafer by coating.
Furthermore, by bonding the adhesive layer as a thermosetting organic coating film, the adhesive layer does not soften even when heat stress is applied in the post-bonding film forming process or heat treatment process. Thus, no gas is generated, the adhesiveness at the interface of the adhesive surface is not deteriorated, and peeling of the interface does not occur.

Further, in the above-described semiconductor element and the manufacturing method of the semiconductor element, the solid-state imaging element, and the manufacturing method of the solid-state imaging element of the present invention, the support substrate is bonded by the adhesive layer, and the adhesive layer is formed on the surface side of the semiconductor layer. Adhesion is possible at a temperature lower than the characteristic deterioration temperature of the circuit element or wiring layer, and the structure is made of a material that does not cause peeling on the adhesion surface by heat treatment below the characteristic deterioration temperature of the circuit element or wiring layer after bonding. it can.
With this configuration, bonding can be performed at a low temperature that is lower than the characteristic deterioration temperature so that the circuit elements and wiring layers are not affected during bonding. Can be prevented from occurring.

In the method for manufacturing a semiconductor device and the method for manufacturing a solid-state imaging device of the present invention described above, the substrate is a stacked substrate in which a semiconductor substrate, an intermediate layer, and a semiconductor layer are stacked, and the intermediate layer is a semiconductor substrate and a semiconductor. It is made of a material having an etching selectivity with respect to the layer, and in the step of thinning the substrate, wet etching can be performed when removing the semiconductor substrate, and then the intermediate layer can be removed.
In such a case, the intermediate layer can be used as an etching stopper in the wet etching process of the semiconductor substrate, and the thickness of the semiconductor layer after the semiconductor substrate and the intermediate layer are removed can be accurately controlled.

In the semiconductor device manufacturing method and the solid-state imaging device manufacturing method of the present invention described above, the support substrate is at least one of the front main surface, the back main surface, and the outer surface of the edge portion of the wafer. It is also possible to adopt a configuration in which a protective film made of a material that can provide an etching selectivity with the semiconductor layer is formed.
In this case, the surface of the support substrate on which the protective film is formed (at least one of the front main surface, the back main surface, and the outer surface of the edge portion of the wafer) is protected by the protective film. It can be protected from being etched.

According to the above-described present invention, since the wiring portion and the like are protected from being etched by the protective film at the time of manufacturing, the semiconductor element and the solid-state imaging element can be manufactured with high yield.
Therefore, the reliability of the semiconductor element and the solid-state imaging element can be improved.

  In addition, according to the method for manufacturing a semiconductor element and the method for manufacturing a solid-state imaging device of the present invention, the number of steps for forming a protective film made of a material that can take an etching selectivity with the semiconductor layer is increased. A solid-state imaging device can be manufactured.

As one embodiment of the present invention, steps of manufacturing a solid-state imaging device having a back-illuminated structure are shown in FIGS.
In this embodiment mode, a solid-state imaging device having a back-illuminated structure is manufactured using a substrate in which a silicon layer is formed over an oxide film on a semiconductor substrate, that is, a so-called SOI substrate.

As shown in FIG. 1, an SOI substrate 10 in which a silicon layer 13 is formed on a silicon substrate 11 via a silicon oxide film 12 is prepared.
First, as shown in FIG. 2, a semiconductor region such as the photodiode PD of the light receiving sensor portion is formed in the silicon layer 13 of the SOI substrate 10.
Next, as shown in FIG. 3, a wiring portion in which the gate electrode G and the multilayer wiring layer 15 are formed in the insulating layer 14 is formed on the surface side of the silicon layer 13.

  Subsequently, as shown in FIG. 4, a protective film 16 made of, for example, silicon nitride is formed on the SOI substrate 10 on which the wiring portion is formed so as to cover both surfaces and the surface of the edge portion 10A.

  Next, as shown in FIG. 5, an adhesive layer 25 is formed on the upper surface on the wiring portion side. For example, an organic coating film to be the adhesive layer 25 is applied.

  Next, as shown in FIG. 6, the support substrate 20 having the protective film 22 formed on the surface is placed on the adhesive layer 25. For example, a substrate in which a protective film 22 made of silicon nitride is formed on the surface of the silicon substrate 21 is used as the support substrate 20.

Next, heat treatment is performed as necessary to cure the adhesive layer 25. At this time, the temperature of the heat treatment is set to a temperature lower than the deterioration temperature of the semiconductor region such as the light receiving sensor portion formed on the silicon layer 13 of the SOI substrate 10, the wiring layer 15, or the contact layer.
Thereby, the SOI substrate 10 and the support substrate 20 are bonded in a wafer state.

Subsequently, the back side of the SOI substrate 10, that is, the side opposite to the side on which the wiring portion is formed is thinned.
First, as shown in FIG. 7, the substrate is turned upside down.
Next, as shown in FIG. 8, the silicon substrate 11 on the back surface side of the SOI substrate 10 is thinned to some extent by polishing such as a CMP (Chemical Mechanical Polishing) method.
Next, the remaining silicon substrate 11 is completely removed by wet etching using an etching solution.
Further, the silicon oxide film 12 constituting the SOI substrate 10 is removed by using another etching solution, and as shown in FIG. 9, the back side of the silicon layer 13 on which the light receiving sensor part is formed is exposed. .

  At this time, the edge portion of the silicon layer 13 and the main surface on the adhesive layer 25 side (surface side) are covered with the protective film 16, and the support substrate 21 is covered with the protective film 22. The adhesive layer 25, the wiring layer 15 and the like are not damaged by the etching solution.

  On the other hand, as a comparative control, the wet etching process using this etching solution was performed in a state where the protective film 16 and the protective film 22 were not formed and the SOI substrate 10 and the silicon substrate 21 were exposed. In this case, as shown in FIG. 17, the etching solution 60 wraps around the edge portions of the substrates 10 and 21, so that the portion indicated by the arrow 61 in the drawing is removed, and the silicon substrate 21 that serves as the support substrate or the bonding The layer 25, the wiring layer 15 and the like are damaged.

  Therefore, the protective film 16 and the protective film 22 can protect the support substrate 21, the adhesive layer 25, the wiring layer 15, and the like from damage due to the etching solution.

  Next, although not shown, a passivation film, a color filter, a microlens, and the like are formed on the back surface side of the silicon layer 13 of the SOI substrate 10 as necessary. Note that the color filter and the microlens are formed in the light receiving sensor portion where the photodiode PD is formed.

In this way, a wafer on which a back-illuminated solid-state imaging device is manufactured is obtained.
Thereafter, the wafer is diced into chips, and a back-illuminated solid-state imaging device chip can be manufactured.

In the case of the present embodiment, in the manufactured back-illuminated solid-state imaging device, the protective film 16 remains between the wiring portion formed on the surface side of the silicon layer 13 and the adhesive layer 25, and The protective film 22 remains on both surfaces of the support substrate 20. In this respect, the configuration is different from a back-illuminated solid-state imaging device manufactured by another manufacturing method in which no protective film is formed.
Since the protective film 16 and the protective film 22 remain, no particular problem occurs in the characteristics of the solid-state imaging device.

By the way, as a method of bonding the SOI substrate 10 and the support substrate 20 in a wafer state, a method of temporarily bonding the SOI substrate 10 and the support substrate 20 and then bonding them by high-temperature heat treatment at 400 ° C. or higher, for example, is conceivable.
By performing high-temperature heat treatment in this way, adhesion can be improved.
However, if bonding is performed after forming circuit elements such as transistors and wiring layers on the SOI substrate 10 by this method, the characteristics of the circuit elements change or the wiring layers melt due to high-temperature heat treatment. Circuit elements and wiring layers cannot be formed on the substrate 10.

In view of this, in order not to deteriorate the wiring layer formed in advance on the SOI substrate 10, a method of bonding the substrates at a low temperature equal to or lower than the characteristic deterioration temperature of the wiring layer is conceivable.
However, in this method, since the adhesive strength is weakened because the adhesive is bonded at a low temperature, the adhesive surface may be peeled off at a poorly adhered portion due to thermal stress in the film forming process or the heat treatment process after bonding. There are things to do. In addition, the adhesive layer 25 may not be sufficiently solidified, and an outgas is generated in a subsequent film forming process or heat treatment process, and this outgas may generate a void on the bonding surface, causing the adhesive surface to peel off. is there.
If the adhesive surface is peeled in this way, the flatness of the back surface of the SOI substrate 10 cannot be obtained, and thereafter, the resist patterning process cannot be performed on the back surface side. Further, in the process of dicing the wafer, the thinned silicon layer may be peeled off from the support substrate 20.
Therefore, it becomes difficult to form a desired device.

  Therefore, the adhesive layer 25 can be bonded at a temperature lower than the characteristic deterioration temperature of the wiring layer formed on the surface side of the silicon layer 13 of the SOI substrate 10, and may be bonded depending on the heat treatment below the characteristic deterioration temperature of the wiring layer after bonding. It is desirable that the surface is made of a material that does not peel off.

Various materials can be used as the adhesive layer 25 made of such a material. For example, an organic coating film can be used.
As this organic coating film, for example, a thermosetting organic coating film can be used.
The SOI substrate 10 and the supporting substrate are selected by selecting the material of the organic coating film so that the curing temperature of the thermosetting organic coating film is equal to or lower than the characteristic deterioration temperature of the element, the wiring layer 15 and the contact layer. Even when 20 is bonded at a temperature lower than the characteristic deterioration temperature of the element, wiring layer 15 or contact layer, the adhesive layer 25 can be sufficiently solidified. Thereby, both the boards 10 and 20 can be bonded with sufficient adhesive strength.

In particular, when a material having good step embedding property is used as the organic coating film, the coating film surface has good flatness, and the flatness of the bonding interface can be ensured.
Thereby, in each bonding surface of the contact bonding layer 25, adhesiveness improvement can be aimed at and a void can be eliminated.
Further, since it is possible to prevent the support substrate 20 from being attached to the SOI substrate 10 in an inclined state, the controllability of the thickness of the remaining silicon layer 13 when the back surface side of the SOI substrate 10 is planarized. Can be improved.
Therefore, the yield and quality of a semiconductor device using a bonded substrate can be improved.

Furthermore, in the case of using a thermosetting organic coating film, by selecting the material of the organic coating film, it can be solidified even when heat stress is applied in the film forming process and heat treatment process after bonding. Since the softening of the adhesive layer 25 and the generation of gas from the inside of the adhesive layer 25 can be prevented, the adhesion at the bonding interface does not deteriorate, and the peeling of the interface does not occur.
This prevents the bonded surface from being peeled even by thermal stress in a process after bonding, for example, a film forming process of an oxide film, or mechanical stress in a dicing process, for example.
Therefore, also from this viewpoint, the yield of the semiconductor device using the bonded substrate can be improved.

  Furthermore, as a material of the adhesive layer 25, by using a material that can take a selective ratio with respect to an etching chemical used in the wet etching process for thinning the back side of the SOI substrate 10, the adhesion in the wet etching process is achieved. It is possible to reliably prevent the substrate from peeling from the layer 25.

According to the above-described embodiment, before the SOI substrate 10 and the support substrate 20 are bonded together, the protective film 16 that can take a selective ratio with respect to the chemical solution that wet-etches the back side of the SOI substrate 10 in advance, for example, silicon nitride A film is formed to cover and protect the wiring portion formed on the surface side of the SOI substrate 10.
Similarly, a protective film 22 made of, for example, a silicon nitride film is formed on the surface of the support substrate 20 so as to cover the silicon substrate 21.

Thereby, after the SOI substrate 10 and the support substrate 20 are bonded together by the adhesive layer 25, the etching amount at the edge portion of the bonded substrate is minimized in the process of thinning the back surface side of the SOI substrate 10 by the wet etching process. It can be suppressed.
For this reason, the insulating layer 14 in the wiring part is etched, and the thinned silicon layer 13 is peeled off, the surface of the edge portion of the support substrate 20 is rough, and the diameter of the support substrate 20 is reduced. Can be solved.
Therefore, the manufacturing yield of the solid-state imaging device manufactured using the bonded substrates can be improved.

In addition, according to the present embodiment, since the SOI substrate 10 is used, the silicon oxide film 12 has an etching selection ratio with respect to silicon. Therefore, the portions other than the edge portions of the substrates 10 and 20 are also Controllability of the thickness of the silicon layer 13 remaining after etching can be improved.
Thereby, desired characteristics of the solid-state imaging device can be obtained, and the manufacturing yield can be increased.

  In the above embodiment, since the SOI substrate 10 and the support substrate 20 are both silicon substrates, the protective film 16 for the SOI substrate 10 and the protective film 22 for the support substrate 20 are both formed of a silicon nitride film. However, the protective films of both substrates to be bonded are not necessarily limited to the same material.

In addition, as a material for the protective film covering each substrate, a material having resistance to an etching solution, such as the silicon nitride film described above, is more preferable.
However, a material other than a material resistant to the etching solution can be used for the protective film of the present invention. For example, if the material has a slower etching rate with an etchant than a silicon substrate, it is possible to suppress damage to the edge portion of the substrate by using the etching selectivity due to the difference in speed.

  Even if only the silicon substrate 11 is used instead of the SOI substrate 10, a back-illuminated solid-state imaging device can be similarly manufactured. The case is shown below.

As another embodiment of the present invention, a process of manufacturing a solid-state imaging device having a backside illumination structure will be described.
In the present embodiment, a photodiode of the light receiving sensor part is formed on a part of the surface side of the silicon substrate 11.
Then, wiring portions (wiring layer 15 and insulating layer 14) are formed on the surface side of the silicon substrate 11.
Thereafter, a protective film 16 is formed on both the front and back main surfaces and edge portions so as to cover the silicon substrate 11 and the wiring portion.
That is, FIG. 10 shows a state corresponding to FIG. 7 of the previous embodiment.

After the state shown in FIG. 10, the silicon substrate 11 is thinned to some extent by a method such as CMP (Chemical Mechanical Polishing).
Thereafter, a wet etching process is performed using an etching solution to thin the silicon substrate 11 as shown in FIG.
At this time, since the silicon substrate 11 is thinned by the wet etching process, the controllability of the thickness of the silicon substrate 11 remaining after the etching process and the flatness of the etched surface are improved as compared with the method of thinning only by polishing or the like. Become good.

  At this time, the edge portion of the silicon layer 11 and the main surface on the adhesive layer 25 side (surface side) are covered with the protective film 16, and the support substrate 21 is covered with the protective film 22. The adhesive layer 25, the wiring layer 15 and the like are not damaged by the etching solution.

  Therefore, the protective film 16 and the protective film 22 can protect the support substrate 21, the adhesive layer 25, the wiring layer 15, and the like from damage due to the etching solution.

In FIG. 11, the photodiode PD of the light receiving sensor unit is not exposed on the back side.
This is because the surface by the etching process has a defect or the like, and if there is a photodiode up to this surface, the defect becomes a source of dark current.

  Next, although not shown, a passivation film, a color filter, a microlens, and the like are formed on the back surface side of the silicon layer 11 as necessary. Note that the color filter and the microlens are formed in the light receiving sensor portion where the photodiode PD is formed.

In this way, a wafer on which a back-illuminated solid-state imaging device is manufactured is obtained.
Thereafter, the wafer is diced into chips, and a back-illuminated solid-state imaging device chip can be manufactured.

Also in the case of the present embodiment, in the manufactured back-illuminated solid-state imaging device, the protective film 16 remains between the wiring portion formed on the front surface side of the silicon layer 11 and the adhesive layer 25. The protective film 22 remains on both surfaces of the support substrate 20. In this respect, the configuration is different from a back-illuminated solid-state imaging device manufactured by another manufacturing method in which no protective film is formed.
Since the protective film 16 and the protective film 22 remain, no particular problem occurs in the characteristics of the solid-state imaging device.

According to the above-described embodiment, before the silicon substrate 11 and the support substrate 20 are bonded to each other, the protective film 16 that has a selective ratio with respect to the chemical solution that wet-etches the back side of the silicon substrate 11 in advance, for example, silicon nitride A film is formed to cover and protect the wiring portion formed on the surface side of the silicon substrate 11.
Similarly, a protective film 22 made of, for example, a silicon nitride film is formed on the surface of the support substrate 20 so as to cover the silicon substrate 21.

Thereby, after the silicon substrate 11 and the support substrate 20 are bonded together by the adhesive layer 25, the etching amount at the edge portion of the bonded substrate is minimized in the process of thinning the back surface side of the silicon substrate 11 by the wet etching process. It can be suppressed.
For this reason, the insulating layer 14 in the wiring portion is etched, and the thinned silicon layer 11 is peeled off, the surface of the edge portion of the support substrate 20 is rough, and the diameter of the support substrate 20 is reduced. Can be solved.
Therefore, the manufacturing yield of the solid-state imaging device manufactured using the bonded substrates can be improved.

In each of the above-described embodiments, the support substrate 20 is configured by covering the silicon substrate 21 with the protective film 22. However, in the present invention, a material having resistance to the etching solution or a material having a low etching rate by the etching solution. The support substrate may be configured without providing a protective film.
In this case, any material can be used as the support substrate as long as it has a small difference in thermal expansion coefficient from silicon and can sufficiently secure adhesion to the adhesive layer.
Even in this case, the effect of the present invention can be obtained in the substrate on which the protective film is formed (such as an SOI substrate).

Furthermore, in the present invention, the protective film may be formed only on the edge portion of the wafer and in the vicinity thereof on both substrates to be bonded.
In this case, since the edge portion where the protective film is formed is removed by dicing for each chip, the protective film does not remain in the finally manufactured solid-state imaging device.

  In each of the above-described embodiments, the case where the manufacturing method of the present invention is applied to a CMOS solid-state image sensor has been described. However, the present invention can be applied to solid-state image sensors having other configurations. For example, the present invention can be similarly applied to a back-illuminated CCD solid-state imaging device.

  In each of the above-described embodiments, a back-illuminated solid-state imaging device is manufactured. However, a semiconductor device in which circuit elements such as transistors are formed in a semiconductor layer can be manufactured in the same manner. It is.

  In the case of manufacturing a semiconductor device, among the steps of manufacturing a back-illuminated solid-state imaging device, the step of forming a photodiode, the step of forming a color filter, and the step of forming a microlens become unnecessary. Other steps can be performed in substantially the same manner.

In the case of a semiconductor element, although not shown, a wiring portion is formed not only on the front surface side of the semiconductor layer but also on the back surface side of the thinned semiconductor layer, or a circuit element is formed near the interface of the semiconductor layer. It is also possible to use a configuration that does this. When manufacturing these configurations (a configuration in which the wiring portion or the circuit element is on both the front and back surfaces of the semiconductor layer), after the back surface side of the semiconductor layer is thinned, the circuit element and the wiring portion are formed on the back surface side.
However, when the circuit element is formed on the back surface side, it is desirable to manufacture using an SOI substrate in order to improve the state of the interface on the back surface side.

Subsequently, still another embodiment of the present invention will be described.
In this embodiment, the present invention is applied to a semiconductor element in which a wiring portion and a circuit element are formed on two bonded substrates as a special form of a semiconductor element in which circuit elements such as transistors are formed in a semiconductor layer. Is.

Hereinafter, the semiconductor element of this embodiment is shown together with its manufacturing method.
First, two substrates shown in FIG. 12 are manufactured.
One substrate is formed by forming circuit elements such as transistors on the surface side of the silicon layer 33 based on the SOI substrate 30 formed by forming the silicon layer 33 on the silicon substrate 31 via the silicon oxide film 32. Yes. On the surface side of the silicon layer 33, a wiring portion in which a gate electrode G and a multilayer wiring layer 35 are formed in an insulating layer 34 is provided. A protective film 36 made of, for example, silicon nitride is formed so as to cover both the front and back main surfaces and the surface of the edge portion.
The other substrate is formed with a circuit element such as a transistor on the surface side of the silicon substrate 41, and a wiring portion in which the gate electrode G and the multilayer wiring layer 43 are formed in the insulating layer 42 on the surface of the silicon substrate 41. Provided. A protective film 44 made of, for example, silicon nitride is formed so as to cover both the front and back main surfaces and the surface of the edge portion.
For each of the protective films 36 and 44, a material capable of taking a selection ratio with respect to a chemical solution that wet-etches the back side of the SOI substrate 30, for example, silicon nitride is used.

  Next, an adhesive layer is formed on at least one substrate by, for example, a coating film, and the other substrate is placed. Thereby, as shown in FIG. 13, the two substrates are bonded in the wafer state by the adhesive layer 45. Thereafter, heat treatment is performed as necessary to cure the adhesive layer 45.

Next, as shown in FIG. 14, the silicon substrate 31 on the back surface side of the SOI substrate 30 is thinned to some extent by polishing such as CMP.
Next, the remaining silicon substrate 31 is completely removed by wet etching using an etching solution.
Further, the silicon oxide film 32 constituting the SOI substrate 30 is removed using another etching solution, and the back surface side of the silicon layer 33 is exposed as shown in FIG.

  At this time, the edge portion of the silicon layer 33 and the main surface on the adhesive layer 45 side (surface side) are covered with the protective film 36, and the other silicon substrate 41 is covered with the protective film 44. 41, the adhesive layer 45, the wiring layers 35 and 43, etc. are not damaged by the etching solution.

Thereafter, contact layers, pads, and the like are formed in order to contact the wiring layers 35 and 43 of each wiring portion with external wiring.
The positions where the pads are formed may be in the silicon layer 33, the back surface side of the silicon layer 33, the silicon substrate 41, the lower surface (back surface) side of the silicon substrate 41, or the like. Of these, if the pad is formed on the back side of the silicon layer 33, connection to external wiring is facilitated and the depth of the contact hole for connecting the pad and the wiring layer is not so large.

Here, FIG. 16A to FIG. 16C show a manufacturing process of one embodiment when the pad is formed on the back surface side of the silicon layer 33. 16A to 16C show enlarged cross-sectional views of main parts of the wafer shown in FIGS. 12 to 15.
FIG. 16A shows a state in which two substrates are bonded together with an adhesive layer 45 as shown in FIG. FIG. 16B shows a state in which the silicon substrate 31 and the silicon oxide film 32 of the SOI substrate 30 are removed as shown in FIGS.

In this embodiment, the contact layer 39 is then formed as shown in FIG. 16C.
First, a through hole having a width wider than that of the contact layer is formed in the silicon layer 33.
Next, the through hole is filled with the insulating layer 37. Further, an insulating layer 38 is formed on the silicon layer 33 so as to cover it. It is also possible to form these insulating layers 37 and 38 with the same insulating layer at the same time.
Next, a contact hole that reaches the wiring layer 35 in the insulating layer 34 through the insulating layers 38 and 37 and the insulating layers 38, 37, 34, the protective film 36, the adhesive layer 45, and the protective film 44 are insulated. A necessary number of contact holes reaching the wiring layer 43 in the layer 42 are formed.
Subsequently, the contact hole 39 is filled and a contact layer 39 is formed of metal or the like.
Next, after forming a wiring layer 51 on the insulating layer 38, the wiring layer 51 is patterned into a predetermined pattern.
Then, an insulating layer 52 is formed so as to cover the wiring layer 51. In this way, the state shown in FIG. 16C is obtained.

In this embodiment, the pad is formed by being connected to the wiring layer 51 although not shown. For example, a contact layer connected to the wiring layer 51 from the upper surface is formed in the insulating layer 52, and the contact layer is connected to a pad formed on the insulating layer 52.
It is also conceivable to open the insulating layer 52 on a part of the wiring layer 51 and use the part of the wiring layer 51 directly as a pad.

By performing the above-described steps, a wafer on which a semiconductor element is manufactured is obtained.
Thereafter, the wafer can be diced into chips to manufacture semiconductor device chips.

In the semiconductor element of the present embodiment, the number of circuit elements per unit area is increased by two silicon layers 33 and a silicon substrate 41 in which circuit elements such as transistors are formed. Can do.
Thereby, a semiconductor element having a high degree of integration can be realized.

In the case of the present embodiment, in the manufactured semiconductor element, the protective film 36 remains between the wiring portion formed on the surface side of the silicon layer 33 and the adhesive layer 45, and also on both sides of the silicon substrate 41 side. The protective film 44 remains. In this respect, the configuration is different from a semiconductor device manufactured without providing a protective film.
Since the protective film 36 and the protective film 44 remain, no particular problem occurs in the characteristics of the semiconductor element.

According to the above-described embodiment, before the two substrates are bonded together, the protective film 36, for example, a silicon nitride film is formed in advance, and the wiring portion formed on the surface side of the SOI substrate 30 is covered and protected. I have to.
Similarly, a protective film 44 made of, for example, a silicon nitride film is formed so as to cover the silicon substrate 41.

Thereby, in the process of thinning the back surface side of the SOI substrate 30 by the wet etching process, the etching amount at the edge portion of the bonded substrate is minimized.
For this reason, the insulating layer 34 in the wiring part is etched, and the thinned silicon layer 33 is peeled off, the surface of the edge portion of the silicon substrate 41 is rough, and the diameter of the silicon substrate 41 is reduced. It can be prevented from occurring.
Therefore, the manufacturing yield of semiconductor elements manufactured using the bonded substrates can be improved.

In addition, according to the present embodiment, since the SOI substrate 30 is used, the silicon oxide film 32 has an etching selection ratio with respect to silicon, so that portions other than the edge portion of the SOI substrate 30 are also etched. The controllability of the thickness of the remaining silicon layer 33 can be improved.
Thereby, desired characteristics of the semiconductor element can be obtained, and the manufacturing yield can be increased.

  In the present invention, not only the SOI substrate, but also other semiconductor substrates can be used as long as they are composed of a semiconductor substrate, an intermediate layer, and a semiconductor layer, and the intermediate layer is composed of the semiconductor substrate and the semiconductor layer and a material having etching selectivity. It is also possible to use it. In this case, the same effect as that obtained when the SOI substrate is used can be obtained.

  The present invention is not limited to the above-described embodiment, and various other configurations can be taken without departing from the gist of the present invention.

It is process drawing which shows the manufacturing method of the solid-state image sensor of one embodiment of this invention. It is process drawing which shows the manufacturing method of the solid-state image sensor of one embodiment of this invention. It is process drawing which shows the manufacturing method of the solid-state image sensor of one embodiment of this invention. It is process drawing which shows the manufacturing method of the solid-state image sensor of one embodiment of this invention. It is process drawing which shows the manufacturing method of the solid-state image sensor of one embodiment of this invention. It is process drawing which shows the manufacturing method of the solid-state image sensor of one embodiment of this invention. It is process drawing which shows the manufacturing method of the solid-state image sensor of one embodiment of this invention. It is process drawing which shows the manufacturing method of the solid-state image sensor of one embodiment of this invention. It is process drawing which shows the manufacturing method of the solid-state image sensor of one embodiment of this invention. It is process drawing which shows the manufacturing method of the solid-state image sensor of other embodiment of this invention. It is process drawing which shows the manufacturing method of the solid-state image sensor of other embodiment of this invention. It is process drawing which shows the manufacturing method of the semiconductor element of further another embodiment of this invention. It is process drawing which shows the manufacturing method of the semiconductor element of further another embodiment of this invention. It is process drawing which shows the manufacturing method of the semiconductor element of further another embodiment of this invention. It is process drawing which shows the manufacturing method of the semiconductor element of further another embodiment of this invention. FIGS. 12A to 12C are process diagrams (enlarged cross-sectional views of main parts of a wafer) for explaining an embodiment of a process for forming a contact layer in the semiconductor element whose process diagrams are shown in FIGS. It is a figure explaining the problem when there is no protective film.

Explanation of symbols

  10, 30 SOI substrate, 11, 21, 31, 41 Silicon substrate, 12, 32 Silicon oxide film, 13, 33 Silicon layer, 14, 34, 42 (Insulation layer) Insulation layer, 15, 35, 43, 51 Wiring Layer, 16, 22, 36, 44 protective film, 20 support substrate, 25, 45 adhesive layer, 37, 38, 52 insulating layer, 39 contact layer, G gate electrode, PD photodiode

Claims (32)

Circuit elements are formed near the surface of the semiconductor layer,
A wiring portion having a wiring layer in an insulating layer is formed on the surface side of the semiconductor layer,
A support substrate is bonded to the further surface side of the wiring part,
A semiconductor element, wherein a protective film made of a material having an etching selectivity with respect to the semiconductor layer is formed at least on a surface of the wiring portion on the support substrate side.   2. The semiconductor element according to claim 1, wherein the semiconductor layer is a silicon layer, and the protective film is made of silicon nitride.   2. The semiconductor element according to claim 1, wherein a protective film made of a material capable of obtaining an etching selectivity with respect to the semiconductor layer is formed on both surfaces of the support substrate.   The semiconductor element according to claim 1, wherein a wiring portion having a wiring layer in an insulating layer is also formed on a back surface side opposite to the front surface side of the semiconductor layer.   The semiconductor element according to claim 4, wherein a circuit element is also formed near the back surface of the semiconductor layer.   The support substrate includes a semiconductor substrate on which circuit elements are formed, and a wiring portion having a wiring layer in an insulating layer, and the wiring portion of the support substrate is disposed on an adhesive surface side. Item 2. The semiconductor element according to Item 1.   The semiconductor element according to claim 1, wherein the support substrate is bonded by an adhesive layer, and the adhesive layer is made of a material having an etching selectivity with respect to the semiconductor layer.   The support substrate is bonded by an adhesive layer, and the adhesive layer can be bonded at a temperature lower than the characteristic deterioration temperature of the circuit element or wiring layer formed on the surface side of the semiconductor layer. 2. The semiconductor element according to claim 1, wherein the semiconductor element is made of a material that does not peel off from the adhesion surface by heat treatment at a temperature lower than the characteristic deterioration temperature of the layer. Forming a circuit element near the surface of the semiconductor layer of a substrate having a semiconductor layer, and forming a wiring portion having a wiring layer in an insulating layer on the surface side of the semiconductor layer;
Thereafter, in the wafer in which the wiring portion is formed in the semiconductor layer, the material that covers at least one of the main surface of the front surface and the outer surface of the edge portion and can have an etching selectivity with the semiconductor layer Forming a protective film comprising:
Adhering a support substrate to a further surface side of the wiring part;
And thinning the substrate,
A method of manufacturing a semiconductor element, wherein wet etching with an etchant is performed in the step of thinning the substrate.   The method for manufacturing a semiconductor device according to claim 9, wherein the semiconductor layer is a silicon layer, and silicon nitride is used for the protective film.   The substrate is a laminated substrate formed by laminating a semiconductor substrate, an intermediate layer, and the semiconductor layer, and the intermediate layer is made of a material having an etching selectivity with respect to the semiconductor substrate and the semiconductor layer, and the substrate is thinned. 10. The method of manufacturing a semiconductor device according to claim 9, wherein in the step, the wet etching is performed when the semiconductor substrate is removed, and then the intermediate layer is removed.   The support substrate is made of a material that covers at least one of the front main surface, the back main surface, and the outer surface of the edge portion of the wafer, and is made of a material having an etching selectivity with respect to the semiconductor layer. The method for manufacturing a semiconductor device according to claim 9, wherein a film is formed.   10. The semiconductor element according to claim 9, wherein after the substrate is thinned, a wiring portion having a wiring layer in an insulating layer is also formed on a back surface side opposite to the front surface side of the semiconductor layer. Production method.   The semiconductor element according to claim 13, wherein after the substrate is thinned, a circuit element is also formed near the back surface of the semiconductor layer, and then the wiring portion is formed on the back surface side.   As the support substrate, a substrate composed of a semiconductor substrate on which circuit elements are formed and a wiring portion having a wiring layer in an insulating layer is used, and the wiring portion of the supporting substrate is disposed on the bonding surface side for bonding. The method of manufacturing a semiconductor device according to claim 9.   10. The method of manufacturing a semiconductor element according to claim 9, wherein in the step of bonding the support substrate, bonding is performed through an adhesive layer made of a material that can take an etching selectivity with the semiconductor layer.   The method of manufacturing a semiconductor element according to claim 16, wherein the adhesive layer is an organic coating film.   The method of manufacturing a semiconductor device according to claim 17, wherein the organic coating film is a thermosetting type.   In the step of bonding the support substrate, the circuit element or wiring layer formed on the surface side of the semiconductor layer can be bonded at a temperature lower than the characteristic deterioration temperature, and the circuit element or wiring layer after bonding is deteriorated. 10. The method of manufacturing a semiconductor element according to claim 9, wherein the bonding is performed through an adhesive layer made of a material that does not cause peeling on the bonding surface by a heat treatment at a temperature below. A wiring portion having a wiring layer in an insulating layer is formed on the surface side of the semiconductor layer where the light receiving portion is formed,
Having a structure in which light is incident from the back side opposite to the front side of the semiconductor layer;
A support substrate is bonded to the further surface side of the wiring part,
A solid-state imaging device, wherein a protective film made of a material capable of obtaining an etching selectivity with respect to the semiconductor layer is formed on at least a surface of the wiring portion on the support substrate side.   21. The solid-state imaging device according to claim 20, wherein the semiconductor layer is a silicon layer, and the protective film is made of silicon nitride.   21. The solid-state imaging device according to claim 20, wherein a protective film made of a material capable of obtaining an etching selectivity with respect to the semiconductor layer is formed on both surfaces of the support substrate.   21. The solid-state imaging device according to claim 20, wherein the support substrate is bonded by an adhesive layer, and the adhesive layer is made of a material having an etching selectivity with respect to the semiconductor layer.   The support substrate is bonded by an adhesive layer, and the adhesive layer can be bonded at a temperature lower than the characteristic deterioration temperature of the circuit element or the wiring layer formed on the surface side of the semiconductor layer. 21. The solid-state imaging element according to claim 20, wherein the solid-state imaging element is made of a material that does not peel off on an adhesive surface by a heat treatment at a temperature lower than a characteristic deterioration temperature of the wiring layer. Forming a light receiving portion in the semiconductor layer of the substrate having a semiconductor layer;
Forming a wiring portion having a wiring layer in an insulating layer on the surface side of the semiconductor layer;
Thereafter, in the wafer in which the wiring portion is formed in the semiconductor layer, the material that covers at least one of the main surface of the front surface and the outer surface of the edge portion and can have an etching selectivity with the semiconductor layer Forming a protective film comprising:
Adhering a support substrate to a further surface side of the wiring part;
And thinning the substrate,
In the step of thinning the substrate, wet etching with an etchant is performed. A method for manufacturing a solid-state imaging device.   26. The method of manufacturing a solid-state imaging element according to claim 25, wherein the semiconductor layer is a silicon layer, and silicon nitride is used for the protective film.   The substrate is a laminated substrate formed by laminating a semiconductor substrate, an intermediate layer, and the semiconductor layer, and the intermediate layer is made of a material having an etching selectivity with respect to the semiconductor substrate and the semiconductor layer, and the substrate is thinned. 26. The method of manufacturing a solid-state imaging device according to claim 25, wherein in the step, the wet etching is performed when the semiconductor substrate is removed, and then the intermediate layer is removed.   The support substrate is made of a material that covers at least one of the front main surface, the back main surface, and the outer surface of the edge portion of the wafer, and is made of a material having an etching selectivity with respect to the semiconductor layer. 26. The method of manufacturing a solid-state imaging device according to claim 25, wherein the film is formed.   26. The method of manufacturing a solid-state imaging device according to claim 25, wherein in the step of bonding the support substrate, bonding is performed through an adhesive layer made of a material that can have an etching selectivity with respect to the semiconductor layer.   30. The method of manufacturing a solid-state imaging device according to claim 29, wherein the adhesive layer is an organic coating film.   31. The method of manufacturing a solid-state imaging device according to claim 30, wherein the organic coating film is a thermosetting type. In the step of bonding the support substrate, bonding is possible below the characteristic deterioration temperature of the circuit element or the wiring layer formed on the surface side of the semiconductor layer, and characteristic deterioration of the circuit element or the wiring layer after bonding 26. The method of manufacturing a solid-state imaging device according to claim 25, wherein the bonding is performed through an adhesive layer made of a material that does not cause separation on the bonding surface by heat treatment at a temperature lower than the temperature.

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