JP3167668B2 - Substrate splitting method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a semiconductor device, and more particularly, to a method for separating a device grown on a monolithic substrate.

[0002]

BACKGROUND OF THE INVENTION Blue / green light emitting devices have been developed using thick sapphire substrates (approximately 100-500 μm thick and 50 mm diameter).
Hexagonal crystal symmetry (wurzite type) grown on a disc-shaped substrate wafer in the range of -150 mm)
Is a thin (about 1-10 μm) GaN-based compound device structure with The device, often a side are typically rectangular shape 200-500. Would therefore many individual devices on a single substrate are assembled in close proximity. Because GaN and sapphire are nearly as hard as diamond, and because the natural cleavage plane of sapphire is not perpendicular to its surface, device isolation (ie, isolation of the "wafer" into individual "dies").
Is extremely difficult. Thus, isolated fracture surface in the wafer, also smooth but rather, and neither the vertical nor flat, these things great influence on the performance and reliability of the device.

[0003] One conventional method for separating devices is to cut the device with a saw (dicing saw). Because sapphire and GaN-based compounds are too hard, the saw blade has a life so short that it is practically unusable for cutting small devices (typically less than 250 cm in a straight line). In addition, sawing requires a wide kerf of about 150 μm or more, which requires waste for sawing. Sawing also causes excessive chipping and unwanted cracks, which propagate into the active area of the device, degrading its performance and reliability.

[0004] Another conventional method is a method to separate the die with a laser cut. Unfortunately, sapphire requires very short laser emission wavelengths (less than 230 nm), which produces very high heat with the use of lasers. The die then undergoes undesired thermal expansion. Moreover, the separation quality is not significantly better than that obtained by sawing.

[0005] Yet another conventional method, "scribe and break", uses a scribe line to define a die separation area and separates the dies along the line by propagation of the break beginning at the scribe mark. In this method, the "passage" between the dies is 50-
It is of the order of 150 μm, occupies a large area on the wafer, and is completely unsuitable in terms of throughput and cost. Also, with a hard surface as described above, the useful life of the scoring tool is typically less than 500 cm in a straight line.

[0006]

All of the above-mentioned conventional methods waste expensive substrate material and produce a fracture surface with insufficient smoothness. A method that can efficiently use a costly and difficult-to-scribe substrate is desired. It would be more cost and throughput beneficial if the method would extend the life of the cutting tool. Ultimately, methods that produce clean, smooth, vertical fracture surfaces will improve the performance and reliability of the final device.

[0007] A similar problem is that GaN-based devices grown on GaN substrates (or substrates other than sapphire); certain glasses used in the manufacture of flat panel displays; or other glass or quartz-based devices (eg, This is encountered when trying to separate other hard-to-cleavable material-based devices, such as wafer-attached night-visible systems. Other problem systems include gallium phosphide (Ga
Difficult semiconductors, such as P) or compound semiconductors, in which the substrate or wafer layer from which the scribing is initiated is a different material system than some other layers of the device. What
Note that "scribing difficult" is when the board is scored and broken
In addition, the state where the ruled line that can solve the above-mentioned problem was done
It is difficult to do.

[0008]

According to the present invention, a difficult-to-scribe substrate having a device surface is first thinned (for example, by a process such as lapping, grinding, etching, lift-off, etc.) and a subsequent cleavage process is performed. To an appropriate thickness. On the other side of the substrate, a layer ("coating") of dielectric or other non-ductile material is grown or deposited.

When scoring this "cover" surface, the "cover" material plays the role of a scribing aid layer. That is, the coating material is selected so that the scored line is softer and cleaner than the substrate. Its thickness is optimized to produce sufficient break propagation. An optional metal layer is placed over the scoring aid layer. This metal layer serves to shield the cutting tool from the piezoelectric discharge and to dissipate the heat generated by the scoring and separation of the die.

[0010] When scribing on the other side of the substrate without scribing on the "coating" surface, the thickness and hardness of the "coating" will optimize the scoring surface to achieve clean break propagation. To maintain tension at An optional metal layer is placed over the scoring aid layer. This metal layer serves to shield the cutting tool from the piezoelectric discharge and to dissipate the heat generated by the scoring and separation of the die.

[0011]

1A-C illustrate a cross section of a wafer according to one embodiment of the present invention with improved rupture propagation. In FIG. 1A, a dielectric layer 2 is grown on a thinned back surface of a substrate 4 that is difficult to score, such as sapphire, gallium nitride (GaN), or gallium phosphide (GaP). In FIG. 1B, a dielectric "coating" is deposited on the surface of the device layer 4a of the sapphire substrate. FIG. 1A,
1B, an optional metal layer 6, such as aluminum, is deposited on the dielectric layer 2. In FIG. In each of FIGS. 1A and 1B, the scribe is made on the thinned substrate 4.
And finally on the side coated with metal . An optional second dielectric layer and a second metal layer may be deposited on the side opposite the deposited side of the dielectric and metal layers (not shown). FIG.
In C, a single dielectric layer 8 is deposited on the thinned substrate side, while scribing is performed on the uncoated device side.

Whenever a score is made on the "cover" side, the "cover" plays the role of a scribing aid layer. That is, a material that is softer than sapphire and can be easily cleaved, such as silicon dioxide (SiO ₂ ), is selected as the coating. As a result, the score lines on the "coating" material are cleaner and better defined than on sapphire. With a good break initiation, good break propagation over hard materials is achieved. In addition, the fracture is further promoted by applying stresses to the wafer that lead to clean fracture propagation. As a result, the life of the scribing tool is extended, and the yield of device separation is improved and the device assembly cost is reduced.

The optional metal layer 6 has the effect of making the die cutting tool slippery, reducing the impact of the tool on the substrate and dissipating heat. The heat generated by the cutting process contributes to tool wear which reduces the score quality. In addition, this layer acts to shield the tool from piezoelectric discharges which would also increase wear and wear.

The scribing aid layer 2 may be aluminum nitride, alumina, silicon nitride, silicon oxy-nitride, or a comparable dielectric or non-ductile layer, but silicon oxide or silicon dioxide is also desirable. . Alternatively, the difficult-to-scribe substrate 4 may be a semiconductor, i.e. GaP, silicon, silicon carbide, or GaN, spinel, glass such as G7, or a large quartz plate.

2A and 2B show an example of a flowchart of a process performed in accordance with the present invention. In the process of FIG. 2A, the scribe is made on the coated side, and in the process of FIG. 2B, the scribe is made on the side opposite to the coated side. In step 10, a plate or wafer with a thin device layer on a thick substrate is assembled. Next, step 20
In step 30 of processing the wafer at to form a large number of interconnected devices, a difficult scoring substrate having a device surface is first thinned (eg, by a process such as lapping, grinding, etching, lift-off, etc.). To a thickness suitable for the subsequent cleavage treatment. For example, to a thickness of about 50-150μm in thickness that used in most material systems by wrapping the rear face of the substrate. Step 30 consists of steps 20 and 40A, 4
0B, typically at step 10B.
After that, it may be anywhere before steps 60A and 60B. In steps 40A and 40B, typically 5-10
A dielectric layer having a thickness between 00 nm is grown on the desired surface of the substrate. The dielectric layer may be deposited by sputtering, evaporation, ion beam evaporation, chemical vapor deposition (CVD), plasma enhanced CVD, and even spin-on-glass. In step 40A, the coating of the dielectric layer or the like is formed into a division promoting layer having an appropriate thickness and hardness for improving the quality of the score line in the subsequent process and improving the onset of fracture. In step 40B, the coating of the dielectric layer or the like is performed on the opposite side to increase the quality of the post-processing score line,
The split promoting layer has an appropriate thickness and hardness so as to generate an appropriate tension for improving the onset of rupture. In steps 50A and 50B, an optional metal layer is deposited on the surface to be scored. In step 50A, a metal layer is deposited over the coating, and in step 50B, the metal layer is deposited on the uncoated side. The metal layer preferably has good malleability, good electrical conductivity and good thermal conductivity. Step 60
In A and 60B, the wafer structure is scribed and then broken along the scribe lines to obtain individual devices. In step 60A, scoring and breaking are performed on the side with the coating, and in step 60B, on the side without the coating.

[0016] The coating, which is a dielectric or non-ductile layer, is preferably deposited on the selected surface such that the surface to be scored is in tension. This promotes clean break propagation and reduces die edge chipping and reduces the path required between the dies.

The main difference between the processes shown in FIGS. 2A and 2B is in the role of the dielectric or non-ductile layer ("coating"). In FIG. 2A, ("coating") is relatively soft (eg, silicon dioxide) and is primarily intended for clean scoring and break initiation (simplification of scoring). Thus, coating to place the scribing surface in a suitable tension is a secondary problem. In FIG. 2B, the primary purpose of ("coating") is to coat the opposite scoring surface in an appropriate tension for optimal break propagation after break initiation (facilitation of breakage). At this time, since the scribing tool does not contact the material,
The material can be quite hard (eg, silicon nitride).

Finally, a coating that combines the process shown in FIGS. 2A and 2B is possible by coating the surface to be scored with a relatively soft and easily cleavable material and coating the other surface with a relatively hard material. The thicknesses of the relatively soft ("coating") material and the relatively hard ("coating") material are oriented towards the start of scoring (easy scoring) and the onset of breaking (easy breaking), respectively. Can also be optimized.

Although the present invention has been described with reference to the embodiments, the embodiments of the present invention are not limited to the above, and the embodiments of the present invention will be exemplified below for reference. Serve. (Embodiment 1) A step of facilitating a substrate that is difficult to score, a step of thinning the substrate that is difficult to score, and a step of thinning the substrate that is difficult to score, having a surface to be scribed and a non-scribed surface. Applying a first non-ductile layer on one side (40A, 40A);
B); a step of scribing a scribing line on the surface of the board on which scribing is difficult, and a step of breaking the board along the scribing line; (Embodiment 2) Substrates which are difficult to score are sapphire, silicon (silicon),
Silicon carbide, gallium nitride, gallium phosphide, glass, and scribed difficult substrate dividing method embodiment 1, wherein the benzalkonium selected from the group consisting of quartz.

(Embodiment 3) The first non-ductile layer is a coating made of a material selected from the group consisting of aluminum nitride, alumina, silicon oxide, silicon dioxide, silicon nitride, and silicon oxy-nitride. The method for dividing a substrate having difficulty in scoring according to the first embodiment. (Embodiment 4) Further, prior to the step of scribing, a step (40) of overlaying a metal layer on the surface of the substrate on which scoring is difficult to be scored.
A, 40B). (Embodiment 5) An embodiment 1 further comprising a step (40A, 40B) of applying a second non-ductile layer on a second surface of the substrate that is difficult to score, on the second surface with respect to the first surface, prior to the scribing step. How to divide the hard-to-scribe board described.

Embodiment 6 The second non-ductile layer is a coating made of a material selected from the group consisting of aluminum nitride, alumina, silicon oxide, silicon dioxide, silicon nitride, and silicon oxy-nitride. The method for dividing a substrate having difficulty in scoring according to the fifth embodiment, characterized in that: (Embodiment 7) Further, prior to the step of scoring, a step (50) of overlaying a metal layer on the surface of the substrate on which scoring is difficult to be scored.
A, 50B).

[Brief description of the drawings]

FIG. 1A is a cross-sectional view of a wafer according to a first embodiment of the present invention with improved scoring and breaking.

FIG. 1B is a cross-sectional view of a wafer according to a second embodiment of the present invention with improved scribing and breakage.

FIG. 1C is a cross-sectional view of a wafer according to a third embodiment of the present invention with improved scribing and breakage.

FIG. 2A is a flowchart of a first process of the present invention.

FIG. 2B is a flowchart of a second process of the present invention.

[Explanation of symbols]

 2 Dielectric layer 4 Substrate difficult to score 4a Device layer 6 Metal layer 8 Dielectric layer

──────────────────────────────────────────────────続 き Continued on the front page (73) Patent owner 399117121 395 Page Mill Road Palo Alto, California U.S.A. S. A. (56) References JP-A-5-166923 (JP, A) JP-A-62-54938 (JP, A) JP-A-61-251051 (JP, A) JP-A-61-251050 (JP, A) JP-A-60-253241 (JP, A) JP-A-55-86133 (JP, A) JP-A-54-140460 (JP, A) JP-A-2-116739 (JP, U) JP-A 58-86 83143 (JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) H01L 21/301

Claims (7)

(57) [Claims] 1. A step and providing a base plate; step and thinning to a thickness suitable to board the cleavage processing of the substrate; and a performing scribed surface and Hikei writing the obtained by thinning a method applying a first non-ductile layer selected thickness and hardness according to the first said surface and front Kimoto plate on a first of said surfaces of the base <br/>plate; scribed in the substrate Step of overlaying a metal layer on the surface to be treated
When; steps and breaking the substrate along the該罫document line; division method adult Ru board provided steps and which scribed a scribed line on a surface to be the scribe that overlay the metal layer. Wherein said substrate is sapphire, silicon, silicon carbide, gallium nitride, a method of dividing gallium phosphide, glass, and board according to claim 1, characterized in that it is selected from the group consisting of quartz. 3. The method of claim 1, wherein the first non-ductile layer is a coating comprising a material selected from the group consisting of aluminum nitride, alumina, silicon oxide, silicon dioxide, silicon nitride, and silicon oxy-nitride. dividing method based board according to claim 1 wherein. 4. The method according to claim 1, further comprising the step of applying a second non-ductile layer on a second said surface relative to said first surface of said substrate prior to said step of overlaying said metal layer.
Board dividing method according. 5. The method of claim 1, wherein the second non-ductile layer is a coating comprising a material selected from the group consisting of aluminum nitride, alumina, silicon oxide, silicon dioxide, silicon nitride, and silicon oxy-nitride. dividing method based board according to claim 4,. 6. Furthermore, prior to the ruffled writing step, before
Dividing method according to claim 5, wherein the base plate including a step of overlay metal layer to the non-scribed surface of serial board. Wherein said substrate is silicon, silicon carbide, gallium nitride, gallium phosphide, glass, and the division of the group <br/> board according to claim 1, wherein a is selected from the group consisting of quartz Method.