JP5471064B2 - Manufacturing method of semiconductor device - Google Patents

Description

  The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for manufacturing a semiconductor device used when manufacturing a thin semiconductor device having a small device thickness.

  Conventionally, development of a thin semiconductor device in which the thickness of the device is reduced as compared with an existing device is progressing. When manufacturing a thin semiconductor device, for example, in the case of a field stop type IGBT (insulated gate bipolar transistor), first, the structure of the front surface is formed on the wafer, and then the electrode of aluminum-silicon alloy is formed. . Next, the wafer back surface is ground and further etched to obtain a desired wafer thickness (thinning step). Then, after cleaning the wafer, ions of phosphorus (P) and boron (B) are implanted, and annealing is performed at a temperature of about 400 ° C. Thereafter, a protective film is formed of polyimide on the front surface of the wafer, and a back electrode is formed on the back surface of the wafer. Finally, the wafer is diced to form individual chips.

  In the above-described manufacturing process, for example, when an FZ wafer is used, the wafer thickness after the thinning process is very thin, about 120 to 140 μm for a device with a withstand voltage of 1200 V class and about 60 to 100 μm with a device with a withstand voltage of 600 V class. . When the wafer thickness is reduced in this way, the strength of the wafer is reduced, and cracks and cracks are likely to occur during dicing, thereby increasing the defect rate of the wafer.

  Therefore, in order to prevent the wafer from cracking when dicing the thinned wafer, there is a technique in which the wafer and the support substrate are bonded with an ultraviolet (UV) curable adhesive to increase the strength and dicing is performed. It has been proposed (see, for example, Patent Document 1). In addition, in order to prevent the wafer from cracking and cracking during dicing, a trench is formed along the dicing line on the front surface of the non-thinned wafer, and then grinding is performed from the back surface of the wafer. There has been proposed a technique for forming the chip (for example, see Patent Document 2).

  Further, the thinned wafer is easily warped under the influence of various film stresses. If the wafer is warped, it may cause a trouble in the subsequent manufacturing process and transfer process. Therefore, a technique for preventing the warpage of the wafer is known by thinning only the central portion of the wafer while leaving the outer periphery of the wafer several mm (for example, 2 to 5 mm).

  Also, as a similar technique, an oxide film is formed on both sides of the wafer, the film on the backside of the wafer is removed leaving the outer peripheral edge, and the remaining oxide film is used as a mask to make a thin layer only at the center of the wafer. There is a known method (see, for example, Patent Document 3). Also known is a method in which only the central portion of the wafer is thinned by masking the outer peripheral edge of the wafer with a seal packing provided in the etching pot and exposing the exposed surface of the central portion of the wafer to an etching solution. (For example, refer to Patent Document 4).

  In the wafer manufactured by the above-described manufacturing method, the outer peripheral portion that is not thinned is referred to as a “rib portion”. Although the thickness of the rib portion depends on the thickness of the device forming portion (wafer center portion), for example, if it is 200 μm or more, there is an effect of preventing wafer warpage.

  However, since a wafer having ribs formed on the outer periphery has a step between the wafer center and the rib, when the dicing tape is applied to the back surface of the wafer in the dicing process, the wafer and the dicing tape are around the step. There will be a gap between the two. If there is a gap between the wafer and the dicing tape, problems such as silicon scraps entering the gap or chips formed in a portion not attached to the dicing tape scatter during dicing. On the other hand, if the dicing tape is forcibly applied to the periphery of the step, the device formed on the periphery of the step may be damaged.

In order to solve such problems, when dicing a wafer having a rib portion, there is a technology that performs dicing using a stage that is substantially the same size as the central portion of the wafer (a recess portion where no rib portion is formed). It has been proposed (see, for example, Patent Document 5).
JP 2004-140101 A JP 2004-006635 A JP 2004-253527 A Japanese Patent No. 3620528 JP 2003-332271 A

However, the technique of Patent Document 5 described above requires a tool such as a stage that matches the wafer, and an existing dicing apparatus cannot be used. For this reason, there is a problem that a new capital investment is required and the production cost of the semiconductor device is increased.

In addition, a method of removing the rib portion by separating the wafer central portion and the rib portion before the dicing process or grinding the surface of the rib portion to eliminate a step from the wafer central portion is also conceivable.
However, when the wafer central portion and the rib portion are separated, the wafer (particularly the thin wafer central portion) is bent, cracked, or warped in the separation process. If the wafer bends or warps, cutting that separates the central portion of the wafer from the rib portion cannot be performed with high accuracy.

  SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and to provide a semiconductor device manufacturing method capable of preventing wafer bending, cracking, warping and cutting accuracy failure when a rib portion is separated from a wafer central portion.

To achieve the above object, according to the first aspect of the present invention in the claims, the outer peripheral portion of the thickness of that a concave portion is provided in a central portion of the first main surface side of the semiconductor wafer (backside) And reducing the thickness of the central portion of the semiconductor wafer by filling the concave portion of the central portion of the semiconductor wafer with a resist material made of a polymer material. A step of applying a protective tape to the second main surface side (front side) of the semiconductor wafer, and a central portion of the semiconductor wafer having the protective tape applied to the second main surface side. And cutting the rib portion from the central portion of the semiconductor wafer.

  According to the invention of claim 2, the polymer material according to claim 1 is characterized in that the polymer material is an alkylene glycol polymer, a cellulose polymer, a urea polymer, a melamine polymer, an epoxy polymer, or It may be any of amide polymers.

  According to the present invention, the rib portion is formed by grinding and thinning the central portion while leaving the rib portion on the outer peripheral portion of the back surface of the semiconductor wafer, and embedding a resist material made of a polymer material in the recess surrounded by the rib portion. Can be prevented from bending, cracking, warping and cutting accuracy failure when the wafer is separated from the wafer center.

It is principal part manufacturing process sectional drawing of the semiconductor device of one Example of this invention. FIG. 2 is a cross-sectional view of the essential part manufacturing process of the semiconductor device according to the embodiment of the invention, following FIG. 1; FIG. 3 is a main-portion manufacturing process cross-sectional view of the semiconductor device of the embodiment of the invention, following FIG. 2; FIG. 4 is a main-portion manufacturing process cross-sectional view of the semiconductor device according to the embodiment of the invention, following FIG. 3; FIG. 5 is a cross-sectional view of the essential part manufacturing process of the semiconductor device according to the embodiment of the invention, following FIG. 4; FIG. 6 is a cross-sectional view of the essential part manufacturing process of the semiconductor device according to the embodiment of the invention, following FIG. 5; FIG. 7 is a cross-sectional view of the main part manufacturing process of the semiconductor device according to the embodiment of the invention, following FIG. 6; FIG. 8 is a cross-sectional view of the main part manufacturing process of the semiconductor device according to the embodiment of the invention, following FIG. 7;

  Embodiments will be described in the following examples.

1 to 8 are process diagrams showing a method of manufacturing a semiconductor device according to one embodiment of the present invention, and are cross-sectional views of main part manufacturing processes shown in the order of processes.
After forming a surface structure (a base layer, a source layer, a gate electrode, etc.) of a desired element (not shown) on the surface A on the front side of the semiconductor wafer 1, a protective tape 2 is attached to the surface A on the front side (FIG. 1).

  Next, in order to provide the rib portion 4 for ensuring the mechanical strength on the outer peripheral portion of the backside surface B of the semiconductor wafer which is turned upside down, the central portion of the backside surface B of the semiconductor wafer 1 is provided. Is ground and thinned by a grinding process using a grinder 3, and the rib portion 4 is left on the outer peripheral portion of the back surface. After grinding, an etching process is performed to remove processing distortion during the grinding process.

  The width T of the rib portion 4 is, for example, about 2 mm to 5 mm from the outer peripheral end of the semiconductor wafer 1 toward the center. The thickness of the central portion (wafer central portion) of the semiconductor wafer 1 after grinding is 50 to 150 μm, for example, 80 μm. Further, the thickness of the rib portion 4 remains the same as that of the semiconductor wafer before grinding (for example, 650 μm).

  Incidentally, C in the figure is the surface on the back side of the thinned portion of the central portion of the semiconductor wafer 1, and is the surface after the etching process (FIG. 2). The rib portion 4 is also slightly thinned by the etching process, but a step (for example, 570 μm) is formed between the central portion and the rib portion.

Next, the protective tape 2 is peeled from the surface A on the front side of the semiconductor wafer 1 (FIG. 3).
Next, a high-concentration semiconductor layer (drain layer, collector layer, etc.) is formed at a desired depth (not shown) on the backside surface B of the semiconductor wafer 1, and a desired back electrode (drain electrode or collector electrode) (not shown) is formed thereon. ) Is formed (FIG. 4).

  Since the outer peripheral portion of the semiconductor wafer 1 is reinforced by the rib portion 4, even after performing the step of forming a high-concentration semiconductor layer or back electrode on the back side surface B after thinning the central portion, The semiconductor wafer 1 is not easily damaged. Here, the process of forming the semiconductor layer is a process such as ion implantation or heat treatment, and the process of forming the back electrode is a process such as vapor deposition, sputtering, or plating.

  Next, the semiconductor wafer 1 is turned upside down again, and the protective tape 5 is applied again to the surface A on the front side of the semiconductor wafer 1 that is on the upper side, and the concave portion ( A resist agent 6 made of a polymer material, which is a polymer material, is embedded in the back surface C). Examples of the polymer material include alkylene glycol polymers, cellulose polymers, urea polymers, melamine polymers, epoxy polymers, amide polymers, and the like.

  The resist agent 6 is dropped into the recess by a dispenser (not shown). The volume of the recess when the central portion of the semiconductor wafer 1 is ground may be calculated in advance, and a predetermined amount of resist agent 6 may be supplied from the dispenser based on the calculation result. At this time, the supply amount of the resist agent 6 may be the same as the volume of the concave portion, or the resist agent 6 may be supplied in anticipation of the shrinkage amount of the resist agent in the pre-bake and post-bake steps described later.

Since the resist agent 6 has fluidity before curing, the resist agent 6 spreads in the recess when dropped into the recess. It becomes almost flat in a few minutes at room temperature.
Alternatively, the front surface A of the semiconductor wafer 1 may be fixed to a stage (not shown), and the semiconductor wafer 1 may be rotated to spread the range agent 6 in the recess.

  In addition, as described later, the resist agent 6 is applied and filled in the recesses in order to separate the ribs 4 without damaging the semiconductor wafer, so that the surface B on the back side of the semiconductor wafer 1 is flattened to some extent. It is in. Therefore, there is no problem even if air is entrained in the resist agent 6 and some bubbles are formed when the resist agent 6 is applied.

  By filling the recess with the resist agent 6, the total thickness of the semiconductor wafer 1 in the central portion of the semiconductor wafer and the thickness of the filled resist agent 6 is substantially the same as the thickness of the semiconductor wafer 1 in the rib portion 4. can do.

  Here, it is desirable that the total thickness of the semiconductor wafer 1 in the central portion of the semiconductor wafer and the thickness of the filled resist agent 6 is the same as the thickness of the semiconductor wafer 1 in the rib portion 4. This is because it is easier to separate the rib portion 4 without damaging the semiconductor wafer when the semiconductor wafer 1 is continuously flat from the rib portion 4 on the back surface side to the center portion.

  However, since the filling of the resist agent 6 is intended to separate the rib portion 4 without damaging the semiconductor wafer, there may be a level difference that does not hinder the cutting of the rib portion. For example, there is no practical problem even if the resist agent 6 is about several percent lower or higher than the thickness of the semiconductor wafer 1 in the rib portion 4.

  In addition, after apply | coating the said resist agent 6 used here, for example, after heating at 80 degreeC-100 degreeC for 10 minutes to a prebake, it heats and hardens it at 80 degreeC to 160 degreeC for 30 minutes after a postbake. (FIG. 5).

  Next, the rib portion 4 on the outer peripheral portion of the semiconductor wafer 1 is separated from the central portion of the semiconductor wafer 1 by the grinder 7 along the dicing line 8 in a state where the protective tape 5 is adhered from the surface A on the front side of the semiconductor wafer 1.

  Since the inside of the concave portion is filled with the hardened resist agent 6, it is almost flattened at the height of the rib portion 4. Therefore, as shown in FIG. 6, even when the front surface A of the semiconductor wafer 1 is placed on a stage (not shown), the semiconductor wafer 1 is not bent and can be cut by the grinder 7.

The central portion of the semiconductor wafer 1 after cutting the rib portion 4 becomes a thin semiconductor wafer 1a (FIG. 6).
Next, the resist agent 6 adhered to the back surface C with the protective tape 5 applied is removed by wet etching using, for example, sulfuric acid / hydrogen peroxide solution, and then the semiconductor wafer 1a is washed with ultrapure water or the like. And dry (FIG. 7). Since the protective tape 5 is attached to the front side surface, even if the back side surface is wet-etched, the protective layer (not shown) on the front side surface is protected.

  Next, the back surface C of the thin semiconductor wafer 1a is affixed to a dicing tape 9 fixed to the dicing ring 10, and after the protective tape 5 is peeled off, the semiconductor wafer 1a is separated from the front surface A of the semiconductor wafer 1a by the dicing line 11. Is cut into a semiconductor chip 12 (FIG. 8).

Next, the semiconductor chip 12 (semiconductor element) is taken out from the dicing tape 9, and the semiconductor chip 12 is packaged to complete the semiconductor device.
In this invention, the protective tape 5 is applied to the second main surface of the semiconductor wafer, the concave portion of the semiconductor wafer 1 inside the rib portion 4 is filled with a resist agent 6 made of a polymer (polymer material) , and the protective tape is applied. By cutting the semiconductor wafer from the second main surface side, it is possible to prevent the semiconductor wafer 1 from being bent, cracked, warped and poor in cutting accuracy when the rib portion is separated from the wafer central portion.

1 Semiconductor wafer 1a Semiconductor wafer (thin)
2 Protective tape 3, 7 Grinder 4 Rib 5 Protective tape 6 Resist agent 8, 11 Dicing line 9 Dicing tape 10 Dicing ring 12 Semiconductor chip

Claims (2)

A step of leaving a rib portion on the outer peripheral portion is thinner than the outer peripheral portion of the thickness of that a concave portion is provided in a central portion of the first main surface side of the semiconductor wafer,
Wherein the recess of the central portion of the semiconductor wafer at the center of the filled resist agent comprising a polymeric material the semiconductor wafer, the thickness of said filled the thickness the total thickness of the outer peripheral portion of the resist material of the semiconductor wafer A step of applying a protective tape to the second main surface side of the semiconductor wafer;
Cutting the central part of the semiconductor wafer to which the protective tape is attached from the second main surface side, and cutting the rib part from the central part of the semiconductor wafer;
A method for manufacturing a semiconductor device, comprising:   The semiconductor device according to claim 1, wherein the polymer material is any one of an alkylene glycol polymer, a cellulose polymer, a urea polymer, a melamine polymer, an epoxy polymer, or an amide polymer. Method.

Images