JP2012028477A - Method of manufacturing semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent emission of gas from an organic insulating film.SOLUTION: A method of manufacturing a semiconductor device comprises steps of: forming an organic insulating film 18 on a function part 13 of a semiconductor device formed on a substrate 10 so as not to cover the upper end of the substrate 10; forming an inorganic insulating film 20 so as to cover the top surface of the organic insulating film 18 and the side surfaces of the organic insulating film 18 on the upper end,; and bonding the substrate and a supporting base in vacuum after the formation step of the inorganic insulating film 20.

Description

  The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for manufacturing a semiconductor device including a step of bonding substrates in a vacuum.

  In a semiconductor device having a structure of a substrate and a semiconductor layer formed on the substrate, it has been devised to remove the substrate from the semiconductor layer (Patent Document 1). In this case, the upper surface of the semiconductor layer is supported using a support substrate.

JP 2002-353235 A

  Since the thickness of the active portion of the semiconductor device is usually as thin as several μm, it is temporarily fixed to some supporting substrate in order to peel it from the substrate at the time of manufacture and handle it. When temporarily fixing to the support substrate, since the surface of the semiconductor device is usually uneven, it is conceivable that an organic insulating film is formed to protect the uneven surface. However, the organic insulating film has a property of easily releasing gas in a vacuum. When using a method for bonding materials in an ultra-high vacuum, there is a problem that it is difficult to maintain the ultra-high vacuum.

  The present invention has been made in view of the above problems, and is characterized by suppressing the release of gas from the organic insulating film.

  The present invention includes a step of forming an organic insulating film on a functional portion of a semiconductor device formed on a substrate so that the organic insulating film is not covered on an end portion of the substrate, and an upper surface of the organic insulating film. And a step of bonding the substrate and the support substrate in a vacuum after the step of forming an inorganic insulating film so as to cover the side surface of the organic insulating film on the end portion and the step of forming the inorganic insulating film A method for manufacturing a semiconductor device, comprising: According to the present invention, it is possible to suppress the release of gas from the organic insulating film.

  In the above structure, the step of bonding in the vacuum may be a structure using a surface activated bonding method.

  In the above configuration, after the step of forming the inorganic insulating film, the step of forming a bonding layer on the lower surface of the support substrate and the upper surface of the inorganic insulating film, and the step of forming the bonding layer, respectively, the vacuum By bonding the bonding layers together, the substrate and the support substrate can be bonded to each other.

  In the above configuration, after the step of bonding in the vacuum, the step of removing the substrate from the lower surface of the active portion of the semiconductor device, and the step of removing the substrate on the lower surface of the active portion of the semiconductor device in vacuum And a step of bonding another substrate.

  In the above configuration, the substrate may be a Si substrate, and the another substrate may be a SiC substrate.

  According to the present invention, it is possible to suppress the release of gas from the organic insulating film.

FIG. 1A to FIG. 1C are cross-sectional views (part 1) illustrating the method for manufacturing the semiconductor device according to the first embodiment. FIG. 2 is a top view of the wafer. 3A and 3B are cross-sectional views (part 2) illustrating the method for manufacturing the semiconductor device according to the first embodiment. 4A and 4B are cross-sectional views (part 3) illustrating the method for manufacturing the semiconductor device according to the first embodiment. 5A and 5B are cross-sectional views (part 4) illustrating the method for manufacturing the semiconductor device according to the first embodiment. 6A to 6C are cross-sectional views (part 5) illustrating the method for manufacturing the semiconductor device according to the first embodiment.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIGS. 1A to 1C and FIGS. 3A to 6C are cross-sectional views illustrating a method of manufacturing a semiconductor device according to the first embodiment. The substrate 10 and the semiconductor layer 12 constitute a wafer. A plurality of semiconductor elements such as FETs (Field Effect Transistors) are formed in the wafer, but for the sake of simplification, one FET is illustrated. The left and right edges in each figure correspond to the edge of the wafer.

  As shown in FIG. 1A, the semiconductor layer 12 is formed on the substrate 10. A source electrode 14, a gate electrode 15, and a drain electrode 16 are formed on the semiconductor layer 12. The substrate 10 is, for example, a Si substrate. The semiconductor layer 12 is, for example, a nitride semiconductor layer. For example, as the semiconductor layer 12, an AlN buffer layer, a GaN channel layer, an n-type AlGaN electron supply layer, and an n-type GaN cap layer are sequentially formed on the substrate 10. As the source electrode 14 and the drain electrode 16, for example, a Ta layer and an Al layer are formed from the semiconductor layer 12 side. As the gate electrode 15, for example, an Ni layer and an Au layer are formed from the semiconductor layer 12 side. Although not shown, in order to reduce the resistance of each electrode, a metal layer of several μm is formed on each electrode. Further, the outermost surface of the wafer is covered with a silicon nitride film except for the bonding pad portion. In addition, unevenness of several μm is formed on the outermost surface of the wafer. The semiconductor layer 12, the source electrode 14, the gate electrode 15, the drain electrode 16, and a metal layer of several μm on each electrode (not shown) and the entire silicon nitride film constitute an active portion 13 of the semiconductor device.

  As shown in FIG. 1B, an organic insulating film 18 is formed on the active portion of the semiconductor device. The outermost surface can be planarized by the organic insulating film 18. That is, the upper surface of the organic insulating film 18 is flattened. An organic insulating film 18 is formed on the end portion of the substrate 10 so as not to cover the organic insulating film 18. For example, photosensitive polyimide is used as the organic insulating film 18. For example, the organic insulating film 18 is spin-coated on the semiconductor layer 12 so that the film thickness becomes 7 μm. By exposing and developing, the organic insulating film 18 on the edge of the substrate 10 is removed. The organic insulating film 18 is cured by heat treatment.

  FIG. 2 is a top view of the wafer. Note that at least the organic insulating film 18 at the edge of the wafer may be removed. For example, the organic insulating film 18 on the edge of the wafer and the scribe line that separates semiconductor elements such as FETs (Field Effect Transistors) may be removed. As shown in FIG. 2, the organic insulating film 18 is formed except for the edge of the wafer which is the substrate 10. As the organic insulating film 18, for example, polyimide, BCB (benzodiclobutene), or Al polymer can be used. The organic insulating film 18 is preferably made of a material having a flat upper surface for subsequent bonding with the support substrate. Moreover, it is preferable that the material is soft enough to protect the electrode and the active part of the semiconductor device. Furthermore, it is preferable to have temperature resistance enough to withstand heat treatment in the subsequent steps. For example, it is preferable that the film is not deformed by the temperature (for example, 200 ° C. to 300 ° C.) during the formation of the inorganic insulating film.

  As shown in FIG. 1C, the inorganic insulating film 20 is formed so as to cover the upper surface of the organic insulating film 18 and the end surface of the organic insulating film 18 on the end portion. For example, silicon nitride is used as the inorganic insulating film 20. For example, the inorganic insulating film 20 having a film thickness of 300 nm is formed using a plasma CVD (Chemical Vapor Deposition) method. The inorganic insulating film 20 is preferably dense enough to suppress the release of gas from the organic insulating film 18. Further, it is preferable to completely cover the upper surface and side surfaces of the organic insulating film 18. Furthermore, it is preferable that the film be removable in the subsequent steps. As the inorganic insulating film 20, silicon oxide or aluminum nitride can also be used.

  Since the end portion of the substrate 10 is usually a portion outside the shot of the stepper exposure, it often takes a large unevenness or dusty surface form as a result of leaving an unnecessary insulating film or metal film in the wafer process. For this reason, even if the inorganic insulating film 20 is formed on the side surface of the organic insulating film 18 formed in this portion, the inorganic insulating film 20 on the side surface is affected by the large unevenness and dusty surface form. It is difficult to effectively suppress the release of gas. In Example 1, the organic insulating film 18 on the edge of the substrate 10 is removed, and the inorganic insulating film 20 is formed on the side surface of the organic insulating film 18. Thereby, the side surface of the organic insulating film 18 can be covered more effectively. Therefore, it is possible to suppress the release of gas from the organic insulating film 18 in a later process.

  As illustrated in FIG. 3A, the bonding layer 22 is formed so as to cover the inorganic insulating film 20. A bonding layer 24 is also formed on the lower surface of the support substrate 26. As the bonding layers 22 and 24, for example, Al having a film thickness of 10 μm formed by vapor deposition is used. The bonding layers 22 and 24 are preferably made of materials that are easily diffused and bonded together. Moreover, it is preferable that it is a material which is easy to remove in a subsequent process. As the bonding layers 22 and 24, a metal other than Al can be used. It is preferable to use Al as a material that easily diffuses and is easily removed. As the support substrate 26, for example, a sapphire substrate is used. It is preferable that the support substrate 26 can support the substrate 10 and has a flat bottom surface.

  As shown in FIG. 3B, the bonding layers 22 and 24 are bonded using a surface activation bonding method. In the ultra high vacuum, the surfaces of the bonding layers 22 and 24 are irradiated with Ar ions or the like. Thereby, the surface is activated. By bonding the bonding layers 22 and 24 together, the bonding layers 22 and 24 are bonded. Since the top surfaces of the inorganic insulating film 20 and the bonding layer 22 are flat by the organic insulating film 18, the bonding layer 22 and the bonding layer 24 can be easily bonded at room temperature. At this time, if gas is released from the organic insulating film 18, it takes time to reach an ultra-high vacuum. Alternatively, the inside of the chamber of the apparatus for surface activated bonding is contaminated. In Example 1, the inorganic insulating film 20 can suppress the release of gas from the organic insulating film 18. Note that when a vapor deposition film, a sputtered film, or the like is used as the bonding layer 22, since the bonding layer 22 is not dense, the release of gas from the organic insulating film 18 is suppressed only by the bonding layer 22 without using the inorganic insulating film 20. It ’s difficult.

As shown in FIG. 4A, the end portion of the substrate 10 is protected using wax 28. The bonding layers 22 and 24 are protected by the wax 28 that melts at 100 ° C. to 120 ° C., for example. As shown in FIG. 4B, the substrate 10 is removed. When the substrate 10 is, for example, a Si substrate, Si is etched by a mixed solution of HF (hydrofluoric acid) and HNO ₃ (nitric acid). At this time, the nitride semiconductor is not etched. As a method of removing the substrate 10, there is a method of providing a peeling layer between the substrate 10 and the semiconductor layer 12 and removing the substrate 10 from the peeling layer, in addition to the method of etching the substrate 10. For example, the substrate 10 can be separated from the semiconductor layer 12 by using the substrate 10 as a sapphire substrate, using AlInN as a separation layer, and irradiating the AlInN with a laser.

  As shown in FIG. 5A, the wax 28 is removed. For removing the wax 28, for example, an organic solvent such as IPA (isopropyl alcohol) is used. As shown in FIG. 5B, the semiconductor layer 12 and another substrate 30 are bonded by a surface activated bonding method. As another substrate 30, for example, a polycrystalline SiC substrate can be used. By using the surface activated bonding method, even a highly ionic crystal can be directly bonded to another substrate. Thereby, the nitride semiconductor layer having high ionicity can be directly bonded to the dissimilar substrate as in the first embodiment.

  A single-crystal SiC substrate is a material that can form a nitride semiconductor layer directly thereon and has good thermal conductivity, but is very expensive. Therefore, as in the first embodiment, an inexpensive Si substrate is used as the substrate on which the nitride semiconductor layer 12 is formed. As shown in FIG. 5A, an inexpensive and high thermal conductivity polycrystalline SiC substrate is bonded to the nitride semiconductor layer 12. Thereby, the structure in which the nitride semiconductor layer 12 is formed on the polycrystalline SiC substrate having good thermal conductivity can be formed at low cost.

  As shown in FIG. 6A, the support substrate 26 is removed by removing the bonding layers 22 and 24. For example, when the bonding layers 22 and 24 are Al, the bonding layers 22 and 24 are etched using hydrochloric acid. As shown in FIG. 6B, the inorganic insulating film 20 is removed. For example, when the inorganic insulating film 20 is silicon nitride, the inorganic insulating film 20 is etched using a buffered hydrofluoric acid solution or a fluorine-based gas. As shown in FIG. 6C, the organic insulating film 18 is removed. For example, when the organic insulating film 18 is polyimide, the organic insulating film 18 is etched by oxygen ashing. Thus, the semiconductor device according to Example 1 is completed.

  According to the first embodiment, as shown in FIG. 1B, the organic insulating film 18 can be flattened by forming the organic insulating film 18 on the active portion of the semiconductor device. Thereby, the board | substrate 10 can be joined to the support substrate 26 like FIG.3 (b). As shown in FIG. 2, the organic insulating film 18 is not covered on the end portion of the substrate 10. As shown in FIG. 1C, the inorganic insulating film 20 covers the upper surface of the organic insulating film 18 and the side surface of the organic insulating film 18 on the end portion. Therefore, after the inorganic insulating film 20 is formed, the release of gas from the organic insulating film 18 can be effectively suppressed in the step of bonding the substrate 10 and the support substrate 26 in a vacuum.

  As a method of bonding the substrate 10 and the support substrate 26 in a vacuum, surface activated bonding can be used.

  As shown in FIG. 3A, bonding layers 22 and 24 are formed on the lower surface of the support substrate 26 and the upper surface of the inorganic insulating film 20, respectively. As shown in FIG. 3B, the upper surfaces of the inorganic insulating films 20 are bonded to the support substrate 26 by bonding the bonding layers 22 and 24 together in a vacuum. Thereby, as shown in FIG. 6A, the supporting substrate 26 can be removed from the semiconductor layer 12 by etching the bonding layers 22 and 24 in a later step.

  As shown in FIG. 4A, the substrate 10 is removed from the lower surface of the active part of the semiconductor device (for example, the lower surface of the semiconductor layer 12). As shown in FIG. 5B, another substrate 30 can be bonded to the lower surface of the active part of the semiconductor device (for example, the lower surface of the semiconductor layer 12) in a vacuum. Thereby, the semiconductor layer 12 can be formed on another substrate 30 different from the substrate 10. A surface activated bonding method can be used for bonding the semiconductor layer 12 and another substrate 30. Also in this case, the release of gas from the organic insulating film 18 can be suppressed.

  The semiconductor layer 12 is a nitride semiconductor layer, and the substrate 10 can be a Si substrate. Thereby, the substrate 10 can be removed by etching the substrate 10 as shown in FIG. Further, the another substrate 30 can be a SiC substrate. Thereby, as described above, a substrate with good thermal conductivity can be provided. Furthermore, an inexpensive substrate can be used by making another substrate 30 a polycrystalline SiC substrate.

  In the first embodiment, the example of the nitride semiconductor is described as the semiconductor layer 12, but the semiconductor layer 12 may be other semiconductor layers. The nitride semiconductor is a semiconductor containing nitrogen, such as InN, AlN, InGaN, InAlN, or AlInGaN.

  In the first embodiment, the FET is described as an example of the semiconductor element formed in the semiconductor layer. However, the semiconductor element may be a transistor such as a bipolar transistor, a PD (Photo Diode), an LED (Light Emitting Diode), or an LD (Laser Diode). An optical semiconductor element such as

  Although the embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications and changes can be made within the scope of the gist of the present invention described in the claims. It can be changed.

DESCRIPTION OF SYMBOLS 10 Substrate 12 Semiconductor layer 13 Functional part of semiconductor device 18 Organic insulating film 20 Inorganic insulating film 22, 24 Bonding layer 26 Support substrate 30 Another substrate

Claims (5)

Forming an organic insulating film on a functional part of a semiconductor device formed on a substrate, and forming an organic insulating film on an end portion of the substrate so as not to cover the organic insulating film;
Forming an inorganic insulating film so as to cover an upper surface of the organic insulating film and a side surface of the organic insulating film on the end;
After the step of forming the inorganic insulating film, the step of bonding the substrate and the support substrate in a vacuum,
A method for manufacturing a semiconductor device, comprising:   2. The method of manufacturing a semiconductor device according to claim 1, wherein the step of bonding in vacuum uses a surface activated bonding method. After the step of forming the inorganic insulating film, forming a bonding layer on each of the lower surface of the support substrate and the upper surface of the inorganic insulating film;
After the step of forming the bonding layer, bonding the substrate and the support substrate by bonding the bonding layers in the vacuum; and
The method of manufacturing a semiconductor device according to claim 1, wherein: After the step of joining in the vacuum,
Removing the substrate from the lower surface of the active portion of the semiconductor device;
After the removing step,
Bonding another substrate to the lower surface of the active portion of the semiconductor device in a vacuum;
The method of manufacturing a semiconductor device according to claim 1, wherein:   5. The method of manufacturing a semiconductor device according to claim 4, wherein the substrate is a Si substrate, and the another substrate is a SiC substrate.

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