JP2013236016A - Manufacturing method of semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a semiconductor device including a peeling process of a support substrate where the peeling treatment is properly conducted without causing problems even when some of an adhesive layer protrude from a proper adhesion region of the adhesion layer when a semiconductor wafer and the support substrate, which are bonded through the adhesion layer, are separated from each other after required process treatment is done.SOLUTION: A manufacturing method of a semiconductor device includes: a second process where light from an ultraviolet light lamp 10 is radiated to an adhesion layer 3 from the support substrate 2 side and a support substrate 2 is peeled from the semiconductor wafer 1 after process treatment, in which a thickness of a semiconductor wafer 1 is reduced from a rear surface and a required semiconductor element function region is formed on the rear surface, is done; and a third process where the adhesion layer 3 remaining on the semiconductor wafer 1 is peeled and removed in immersion treatment using a peeling liquid.

Description

  The present invention relates to a method for manufacturing a semiconductor device, and in particular, in order to reduce the thickness of the substrate, a process of peeling the support substrate after attaching the support substrate to the surface of the semiconductor substrate and grinding the back surface is preferable. It relates to the improvement of the manufacturing method including.

  An electronic circuit for performing a designed function is disposed in a main part of the computer or communication device. In this electronic circuit, a plurality of integrated circuits (hereinafter referred to as ICs) in which a large number of single-function electronic devices such as transistors and resistors are integrated on a one-chip semiconductor substrate are often mounted. . Among these ICs, those including a power semiconductor device as a single-function electronic device are called power ICs. As one of such power semiconductor devices, an insulated gate bipolar transistor (hereinafter, IGBT) is known.

  This IGBT is attracting attention because it is a semiconductor device that has both high-speed switching characteristics and voltage drive characteristics of MOSFETs and low on-voltage characteristics of bipolar transistors. The range of applications has expanded from industrial fields such as general-purpose inverters, AC servos, uninterruptible power supplies (UPS), or switching power supplies to consumer equipment fields such as microwave ovens, rice cookers, and strobes. Further, in order to expand application fields, IGBTs are required to further reduce loss from the market. As one means for reducing the loss and increasing the efficiency of the IGBT, there is a method of reducing the thickness of the semiconductor substrate as much as possible within a range where a design withstand voltage can be obtained or within an allowable range of a manufacturing process.

  A conventional method relating to reducing the thickness of the semiconductor substrate as much as possible will be described below. In general, when the thickness of the semiconductor substrate is reduced, the mechanical strength of the semiconductor wafer is reduced, and many wafer cracks occur in the manufacturing process, making handling (handling) difficult. In order to solve this problem, in order to reinforce the mechanical strength after thinning the semiconductor wafer, the semiconductor wafer is bonded to a supporting substrate such as a quartz glass substrate in advance before thinning, A method of thinning a semiconductor wafer by grinding the semiconductor wafer surface (back surface) is known. This method will be specifically described.

  FIG. 8 shows a conventional method for thinning a semiconductor wafer, and FIGS. 8A to 8G are sectional views of the principal steps of manufacturing the semiconductor wafer shown in the order of the manufacturing steps. A quartz glass substrate 51 is used as the support substrate. The diameter of the quartz glass substrate 51 is about 0.1 mm to 1 mm larger than the diameter of the semiconductor wafer 54.

  An adhesive 53 is applied to the surface side of the semiconductor wafer 54 (FIG. 1A). At this time, in order to protect the unevenness of various diffusion layers (not shown) on the surface side of the semiconductor wafer 54 and surface side functional layers such as surface side electrodes and control electrodes, a thick adhesive 53 is applied (10 μm). ˜30 μm). The quartz glass substrate 51 is attached to the semiconductor wafer 54 so as to be coaxially opposed to each other through the adhesive 53 ((b) in the figure). The semiconductor wafer 54 and the quartz glass substrate 51 are fixed to each other by pressing 61 in a state where heat is applied ((c) in the figure).

  Next, the back surface 56 (FIG. 5C) of the semiconductor wafer 54 is back-ground (the ground thickness 57) to form a thin film semiconductor wafer 58, and then the back surface 59 of the thin film semiconductor wafer 58 after grinding is subjected to hydrofluoric acid. Spin-etch with solution to remove processing distortion caused by grinding. Thereafter, a required diffusion layer (not shown) is formed on the back surface 59 of the thin film semiconductor wafer 58, and a back side main electrode (not shown) is formed on the diffusion layer (FIG. 4D).

  Next, the back surface 59 of the thin film semiconductor wafer 58 is attached to a UV tape 60 (an adhesive tape that can be peeled off by ultraviolet irradiation). After that, the surface of the adhesive 53 is irradiated with a laser 62 from the quartz glass substrate 51 side to weaken the adhesive force between the quartz glass substrate 51 and the adhesive 53 ((e) in the figure). The quartz glass substrate 51 is removed. The adhesive 53 remaining on the thin film semiconductor wafer 58 is removed with an organic chemical (FIG. 5F). Thereafter, the thin film semiconductor wafer 58 is cut at a portion (scribe line) indicated by a one-dot chain line 64 ((g) in the figure) (Patent Document 1).

  In another document, a surface element structure portion of a semiconductor element is formed on the surface of a semiconductor wafer. A support substrate is bonded to the surface on which the surface-side element structure portion is formed. Grind the backside of the semiconductor wafer to reduce the substrate thickness. A functional region is formed on the back surface of the semiconductor wafer. The support substrate is peeled from the semiconductor wafer by irradiating the adhesive layer with ultraviolet rays. There is a description of a method capable of preventing the semiconductor wafer from cracking by performing the process of thinning the semiconductor wafer in this way (Patent Document 2). There is also a document disclosing use of an ultraviolet lamp as an ultraviolet light source when irradiating with ultraviolet light in order to reduce the adhesive strength of an adhesive for bonding a semiconductor wafer to a semiconductor substrate at the time of peeling (Patent Document 3). ). In addition, there is a description of a situation in which an adhesive that bonds the semiconductor wafer and the support substrate protrudes to the outer periphery of the semiconductor wafer (Patent Document 4).

Japanese Patent Laying-Open No. 2005-129653 (FIG. 8) JP 2004-140101 A (summary) JP 2005-150453 A (summary) JP 2005-114306 A (FIG. 2, paragraph 0013)

  In the method described in Patent Document 1, the semiconductor wafer 54 and the support substrate 51 are once bonded together via an adhesive 53, and backside grinding and necessary process processing are performed on the exposed surface of the semiconductor wafer 54. In order to peel off the support substrate 51 from the wafer 54, a UV laser or infrared laser light is irradiated from the transparent support substrate 51 side to weaken the bonding of the adhesive 53. However, in the case of this laser system, since the range of the light irradiation region is narrow, it is necessary to scan the laser beam to widen the irradiation range and irradiate the entire adhesive coating film. Laser scanning of the flat adhesive coating area sandwiched between the semiconductor wafer and the support substrate only reduces the adhesive tackiness of the irradiated flat area and makes it easy to peel off. Absent. Therefore, as shown in FIG. 9, when the semiconductor wafer 54 and the support substrate 51 are bonded together by pressure bonding, the protruding coating film 40 in a state where the adhesive 53 protrudes from the side surfaces of the semiconductor wafer 54 and the support substrate 51 is formed. However, since the protruding coating 40 is not on the extension of the flat adhesive coating, the surface of the protruding adhesive is not properly irradiated with laser, and there is a problem that the support substrate is difficult to peel off from the semiconductor wafer. Sometimes.

  The present invention has been made in consideration of the above-described problems, and an object of the present invention is to provide a semiconductor wafer and a supporting substrate attached via an adhesive layer, a semiconductor wafer, A method for manufacturing a semiconductor device including a support substrate peeling process capable of appropriately performing a peeling process without any trouble even when there is an adhesive layer protruding from an appropriate adhesion region of the adhesive layer when the support substrates are separated from each other Is to provide.

  In order to achieve the object of the invention described above, in the present invention, a semiconductor substrate that has undergone a process treatment for producing a required semiconductor element functional region on one main surface is converted into an ultraviolet light radiating treatment and an ultraviolet transmissive support substrate. A first step of attaching the one main surface as a bonding surface through an adhesive layer that can be peeled off by immersing in a stripping solution, reducing the thickness of the semiconductor substrate from the other main surface and providing the other main surface A second step of peeling the support substrate from the semiconductor substrate by irradiating the adhesive layer with an ultraviolet lamp from the support substrate side after performing the process for forming the semiconductor element functional region of A semiconductor device manufacturing method comprising: a third step of peeling and removing the remaining adhesive layer by immersing in a stripping solution. In the second step, the semiconductor substrate is reduced in thickness from the other main surface, and a required semiconductor element functional region is formed on the reduced surface, and then the required semiconductor element functional region is formed. It is also preferable to apply a dicing tape on the surface, and then irradiate the adhesive layer with an ultraviolet lamp from the support substrate side to peel the support substrate from the semiconductor substrate. The ultraviolet lamp is preferably a mercury lamp, an excimer lamp, a xenon lamp, or an LED lamp. The wavelength of the ultraviolet lamp is preferably 400 nm or less, particularly 250 nm or less. The material of the support substrate is preferably any glass selected from quartz glass, sapphire glass, Tempax (registered trademark) glass, and alkali-free glass. The support substrate is preferably larger by about 0.1 mm to 1 mm than the diameter of the semiconductor substrate. The merit of the present invention can also be obtained when the adhesive layer is applied across the bonding surface between the semiconductor substrate and the support substrate and the side surface of the support substrate.

  According to the present invention, when a semiconductor substrate and a support substrate pasted via an adhesive layer are peeled from each other after a required process, the semiconductor substrate and the support substrate protruded from an appropriate adhesive region of the adhesive layer. Even if there is an adhesive layer, a method for manufacturing a semiconductor device including a support substrate peeling process capable of appropriately performing a peeling process without hindrance can be provided.

It is process process sectional drawing (the 1) of the semiconductor substrate for demonstrating the manufacturing method of the semiconductor device processed thinly to the extent which requires the support substrate concerning this invention. It is process process sectional drawing (the 2) of the semiconductor substrate for demonstrating the manufacturing method of the semiconductor device processed thinly to the extent which requires the support substrate concerning this invention. It is process process sectional drawing (the 3) of the semiconductor substrate for demonstrating the manufacturing method of the semiconductor device processed thinly to the extent which requires the support substrate concerning this invention. FIG. 10 is a process cross-sectional view of a semiconductor substrate for explaining a method of manufacturing a semiconductor device processed to be thin enough to require a support substrate according to the present invention (part 4); It is process process sectional drawing (the 5) of the semiconductor substrate for demonstrating the manufacturing method of the semiconductor device processed thinly to the extent which requires the support substrate concerning this invention. FIG. 11 is a process cross-sectional view (No. 6) of a semiconductor substrate for describing a method for manufacturing a semiconductor device processed to be thin enough to require a support substrate according to the present invention; It is process process sectional drawing (the 7) of the semiconductor substrate for demonstrating the manufacturing method of the semiconductor device processed thinly to the extent which requires the support substrate concerning this invention. It is process process sectional drawing of the semiconductor substrate for demonstrating the manufacturing method of the conventional semiconductor device processed thinly to the extent which requires a support substrate. It is sectional drawing of the semiconductor substrate for demonstrating the problem in the manufacturing method of the conventional semiconductor device shown in FIG.

Embodiments of the method for manufacturing a semiconductor device according to the present invention will be described below in detail with reference to the drawings. In the present specification and the accompanying drawings, it means that electrons or holes are majority carriers in layers and regions with n or p, respectively. Further, + and − attached to n and p mean that the impurity concentration is relatively high or low, respectively. In the following description of the embodiments and the accompanying drawings, the same reference numerals are given to the same components, and duplicate descriptions are omitted. In addition, the accompanying drawings described in the embodiments are not drawn to an accurate scale and dimensional ratio for easy understanding and understanding. The present invention is not limited to the description of the examples described below unless it exceeds the gist.
<Example 1>
Regarding the method for manufacturing a semiconductor device of the present invention, a method for manufacturing a semiconductor device having a thickness of 100 μm or less as a semiconductor wafer (hereinafter, the semiconductor wafer may be used as a semiconductor substrate) will be described below. When a process of immediately depositing or adhering a layer or film on a thin semiconductor substrate surface having a thickness of 100 μm from the beginning of the wafer process is performed, warpage generated in the semiconductor substrate tends to increase due to a difference in thermal expansion coefficient. If the semiconductor substrate is warped, depending on the degree, the semiconductor substrate may be cracked or the semiconductor substrate adsorption device may be abnormal (error, etc.).

  For this reason, even in a wafer process for manufacturing a thin semiconductor device having a finished semiconductor substrate thickness of 100 μm or less, a thick semiconductor substrate having an initial thickness of 600 μm or more is used, for example. It is preferable that the process of reducing the thickness of the semiconductor substrate to 100 μm is performed in the later steps as much as possible. At the beginning of the process, a process of forming a required semiconductor functional region on one main surface (referred to as the front surface) side is performed in a thick semiconductor substrate state. In order to form a necessary semiconductor functional region on the other main surface (back surface) side of the semiconductor substrate, the back surface side of the semiconductor substrate is ground and reduced to a predetermined thickness. At that time, in order to reinforce the wafer strength after the semiconductor substrate is thinned, the above-mentioned semiconductor substrate having been subjected to the required process on the front side in advance is changed to a support substrate having a low thermal expansion coefficient such as a quartz glass substrate. Affix the front side as the joint surface.

  Thereafter, the semiconductor substrate surface (back surface) on the non-bonded side is ground to thin the semiconductor substrate, thereby adopting a method in which wafer cracking hardly occurs during the thinning process. As the support substrate, in addition to the above-mentioned quartz glass (silica glass), any stable glass, glass ceramic glass, or ceramics having good ultraviolet transmittance, heat resistance, and chemical resistance can be used. For example, borosilicate glass such as Tempax (registered trademark) glass having high heat resistance, sapphire glass (alumina glass), glass ceramics having good strength and heat resistance, and the like can be used.

  Hereinafter, a case where a power device such as an IGBT using a thin semiconductor substrate (for example, a finished thickness of 100 μm) is manufactured will be described. In the case of an IGBT, the surface side of the semiconductor substrate is a surface on which a device surface structure (semiconductor functional region) such as an emitter electrode, a gate electrode, and a MOS gate structure is formed, and the back side is formed of a collector layer and a collector electrode The surface to be used.

  A semiconductor functional region (not shown) such as an emitter electrode, a gate electrode, and a MOS gate structure is formed on the front side of a 650 μm thick FZ-n type semiconductor substrate by a well-known process. End the street. Before entering the formation process on the back surface side of the semiconductor substrate 1, a support substrate 2 transparent to ultraviolet rays (UV light) is provided on the front surface side of the semiconductor substrate 1 having the above-described semiconductor functional region via an adhesive layer 3. Crimp so that there is no gap (Fig. 1). The support substrate 2 may have a thickness of about 0.1 mm to 1 mm, and may be a quartz glass substrate having substantially the same diameter as the semiconductor substrate 1.

  The pressure bonding of the support substrate 2 via the adhesive layer 3 will be described in detail. As the support substrate 2, in addition to quartz glass similar to that described above, glass that efficiently transmits the irradiation ultraviolet wavelength, such as Tempax (registered trademark) glass and sapphire glass, and ultraviolet transmittance and heat resistance as described above. In addition, stable glass ceramic glass or ceramic having good chemical resistance can be used. The adhesive layer 3 is adhered by adhering the semiconductor substrate 1 on a spinner (not shown) using a spin coater, dropping the adhesive solution while rotating the spinner, and adsorbing the semiconductor substrate 1 with the semiconductor functional region side facing up. A layer coating is formed.

  The adhesive used to form such an adhesive layer 3 has the property of being dissolved by immersion in an organic stripping solution such as thinner or amine, and the adhesive strength is reduced by irradiation with UV light. It is desirable to have a peelable property.

  Further, in the process of peeling the adhesive layer 3, the semiconductor substrate 1 having the semiconductor functional region formed on the surface side comes into contact with the stripping solution. It is necessary to use a stripping solution that does not dissolve or swell the polyimide film.

  Thereafter, the solvent in the adhesive coating film is removed by a required post-baking process (about 200 to 300 ° C., 1 hour) in an electric furnace or the like to obtain an adhesive layer 3. When forming the above-mentioned adhesive layer coating film, it is necessary to absorb the irregularities on the outermost surface of the semiconductor functional region of the semiconductor substrate 1 to make it flat, so that the thickness of the adhesive layer coating film is about 5 to 40 μm. Thus, it is desirable to obtain the viscosity of the adhesive solution and the spinner rotation number as appropriate in advance. For crimping, the alignment is performed so that the central axes of the semiconductor substrate 1 and the support substrate 2 coincide with each other with the support substrate 2 facing up, and the adhesive layer 3 is sandwiched while being heated in a vacuum (about 200 to 300 ° C.). Crimp with. Although the thickness of the adhesive layer 3 is further reduced by this pressure bonding, the thickness of the adhesive layer is maintained so as to be flattened by eliminating the uneven step on the outermost surface of the semiconductor functional region. As shown in FIG. 11, the adhesive layer coating film that protrudes from the pressure-bonded surface to the side surface of the semiconductor substrate by pressure bonding adheres to the side surface of the support substrate or the semiconductor substrate. Since such an adhesive layer coating that protrudes from the side surface occurs, conventionally, the protruding adhesive layer coating is not reliably irradiated with an ultraviolet wavelength laser, and the support substrate and the semiconductor substrate are separated in a later step. The problem was that it could not be done reliably.

  In the present invention, this problem is solved by using a UV lamp that efficiently includes an ultraviolet wavelength instead of a laser beam having an ultraviolet wavelength. In other words, the UV lamp, unlike the laser having the same phase and coherent properties of a single wavelength, radiates in a radial direction from the light source, so that it is sufficient for the adhesive layer coating portion protruding from the side surface of the semiconductor substrate as described above. It is because the adhesive force of the coating film portion that has been irradiated and protruded can be reduced and peeled off.

  According to the embodiment described above, as described above, even if the adhesive layer coating film protrudes from the side surface of the semiconductor substrate 1 by pressure bonding, the separation between the support substrate 2 and the semiconductor substrate 1 in the subsequent process is ensured. Since the problem that it cannot be performed is solved, even if the adhesive layer coating film protrudes from the side surface, the process can proceed to the next step without any trouble.

That is, a semiconductor substrate 1 bonded with a support substrate 2 via an adhesive layer 3 is placed in a back grinding apparatus (not shown) and the back surface of the semiconductor substrate 1 is ground to a predetermined thickness (100 μm). The thickness is reduced (FIG. 2). The ground surface is cleaned with a processing solution including etching. Phosphorus is ion-implanted into the cleaned back surface of the semiconductor substrate 1 at a dose of 1 × 10 ¹¹ to 1 × 10 ¹³ cm ⁻² and an acceleration energy of 5 MeV (not shown). Subsequently, boron is ion-implanted from the same back surface at a dose of 1 × 10 ¹³ to 1 × 10 ¹⁵ cm ⁻² and an acceleration energy of 50 KeV. Thereafter, the back surface of the semiconductor substrate 1 is irradiated with a laser to activate the ion implantation layer by annealing to form an n ⁺ layer serving as a buffer layer and a p ⁺ layer serving as a collector layer (not shown).

  Next, a plurality of metals such as aluminum, titanium, nickel, and gold are vapor-deposited on the back surface of the semiconductor substrate 1 to form a back electrode 4 that serves as a collector electrode (FIG. 3). A dicing tape 5 having heat resistance and chemical resistance is attached to the back surface of the semiconductor substrate 1, and a ring-shaped dicing frame 6 is attached to the dicing tape 5 in order to ensure transportability (FIG. 4). The UV layer 10 irradiates the adhesive layer with ultraviolet wavelength light from the support substrate 2 side, weakens the adhesive force of the adhesive layer 3 interposed between the surface side of the semiconductor substrate 1 and the support substrate 2, and peels the support substrate 2. (FIG. 5). At this time, the ultraviolet wavelength light applied to the adhesive layer 3 lowers the adhesive force between the support substrate 2 and the adhesive layer closer to the light source than between the semiconductor substrate 1, so that the support substrate 2 is peeled off. As a result, the adhesive layer 3 tends to remain on the surface of the semiconductor substrate 1. In order to dissolve the adhesive layer 3, the semiconductor substrate 1 is immersed in a stripping solution at room temperature to 80 ° C. or the stripping solution is sprayed from the upper part of the semiconductor substrate 1. The immersion time varies depending on the amount of the adhesive layer and the temperature of the stripping solution, but is about 1 to 30 minutes (FIG. 6).

The material of the dicing tape 5 is preferably made of a chemical resistant polyolefin (PO) or polyethylene terephthalate (PET). As the UV lamp 10, a mercury lamp, excimer lamp, xenon lamp or the like is preferable. If the illuminance of the UV lamp 10 is 5 J / cm ² or more, the processing is completed in a short time. As the stripper for removing the adhesive layer 3 remaining on the surface of the semiconductor substrate 1, an organic solution such as thinner or amine is preferable.

  Then, the semiconductor substrate 1 from which the adhesive layer residue has been removed from the surface of the semiconductor substrate 1 is attached to a dicing apparatus, and the dicing blade saw 7 of the dicing apparatus is cut into a dice shape to form chips (see FIG. FIG. 7), the completion of a semiconductor device (IGBT) chip.

  In the conventional method of detaching the support substrate by irradiating the adhesive layer of the UV laser, when the adhesive layer protrudes from the semiconductor substrate and the support substrate, it is possible to reliably irradiate the protruding coating film 40 due to the influence of the focal length of the laser or the like. In some cases, the support substrate 51 cannot be normally detached from the semiconductor substrate 54 (FIG. 9). In order to solve these problems, by using an irradiation method of a UV lamp such as a mercury lamp, an excimer lamp, or a xenon lamp that can irradiate the entire surface of the substrate with a relatively uniform illuminance regardless of the focal length of light, a semiconductor substrate or Even when the protruding coating film 40 is attached to the side wall of the support substrate, the UV light source is irradiated on the entire adhesive layer, so that the support substrate can be easily detached from the semiconductor substrate.

DESCRIPTION OF SYMBOLS 1 Semiconductor substrate 2 Support substrate 3 Adhesion layer 4 Metal film 5 Dicing tape 6 Dicing frame 7 Dicing blade saw 10 UV lamp 40 Extrusion coating film

Claims (6)

A semiconductor substrate that has undergone a process process for producing a required semiconductor element functional region on one main surface is placed on an ultraviolet transmissive support substrate through an adhesive layer that can be peeled off by an ultraviolet light irradiation process and an immersion process in a stripping solution. A first step of pasting the one main surface as a bonding surface, and performing a process of reducing the thickness of the semiconductor substrate from the other main surface and forming a required semiconductor element functional region on the reduced surface , A second step of irradiating the entire surface of the adhesive layer with an ultraviolet lamp from the support substrate side to peel the support substrate from the semiconductor substrate; peeling the adhesive layer remaining on the semiconductor substrate by a dipping process in a stripping solution; And a third step of removing the semiconductor device. In the second step, the semiconductor substrate is reduced in thickness from the other main surface, and a required semiconductor element functional region is formed on the reduced surface, and then the required semiconductor element functional region is formed. The dicing tape is affixed to the finished surface, and thereafter the adhesive substrate is irradiated with an ultraviolet lamp from the side of the support substrate to separate the support substrate from the semiconductor substrate. Semiconductor device manufacturing method. 3. The method of manufacturing a semiconductor device according to claim 2, wherein the ultraviolet lamp is any one of a mercury lamp, an excimer lamp, and a xenon lamp. 4. The method of manufacturing a semiconductor device according to claim 1, wherein a material of the support substrate is any glass selected from quartz glass, heat-resistant glass, and chemical-resistant glass. 5. The method for manufacturing a semiconductor device according to claim 1, wherein the support substrate has substantially the same diameter as the semiconductor substrate. 6. The method of manufacturing a semiconductor device according to claim 1, wherein the adhesive layer is applied across a bonding surface between the semiconductor substrate and the support substrate and a side surface of the support substrate. .

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