JPS61149316A - Method of cutting pressure sensor wafer - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a cutting method for cutting a pressure sensor wafer formed by bonding a silicon pressure-sensitive element wafer and a pedestal wafer into a plurality of pressure sensor chips.

(Prior Art) Generally, a dicing method is used to cut a semiconductor pressure sensor wafer by rotating a blade having diamond abrasive grains at a cutting edge at high speed.

That is, as shown in FIG. 2, the silicon pressure sensitive elements constituting the semiconductor pressure sensor wafer 6 are scanned by scanning the blade along the lattice-shaped cutting path dicing lines drawn and formed on the surface of the silicon pressure sensitive element wafer 1. The wafer 1 and the pedestal wafer 5 are cut at once and separated into individual pressure sensor chips. By the way, in dicing using a diamond blade, the quality of processing results depends on whether the cutting conditions 1, such as the type of blade used, the number of rotations, and the cutting speed are suitable for the material of the workpiece. Therefore, in the above-mentioned cutting, the main focus is placed on the pedestal wafer, which is usually several times thicker than the silicon pressure-sensitive element wafer, and cutting conditions suitable for this are selected. however.

The cutting conditions selected here are often not necessarily suitable conditions for the silicon pressure-sensitive element wafers to be cut at the same time, so when observing the individual pressure sensor chips obtained by the above-mentioned cutting.

Because the surface of the flat silicon pressure-sensitive element wafer was cut by dicing, the cross-sectional angle of the cut was θ as shown in Figure 2.
Therefore, it forms almost a right angle as shown in a.

There are chips and cracks of various sizes along the cut edges of silicon pressure-sensitive elements, and a reduction in the yield of pressure sensor chips due to this damage is a problem, and a solution is needed. It was getting worse.

(Object of the invention) The present invention has been made in view of the above-mentioned conventional problems, and
The purpose is to provide a method for cutting a pressure sensor wafer that can reduce chipping and cracking that occur at the cut end of the surface of a silicon pressure-sensitive element wafer, and improve the yield based on these occurrences.

(Structure of the Invention) A first method of the present invention is to cut a pressure sensor wafer formed by bonding a silicon pressure-sensitive element wafer having a plurality of silicon pressure-sensitive elements onto a pedestal wafer into nine pieces. A pressure sensor wafer is constructed by bonding an element wafer to a pedestal wafer.

Thereafter, a groove having a V-shaped cross section is formed along the path to be cut on the silicon pressure sensitive element wafer, and then a cutting blade having a width narrower than the maximum groove width of the V-shaped cross section is used to cut the groove into the silicon pressure sensitive element wafer. This method is characterized in that the pressure sensor wafer is cut along the grooves.

Further, in the second method of the present invention, when cutting a pressure sensor wafer formed by bonding a silicon pressure-sensitive element wafer provided with a plurality of silicon pressure-sensitive elements to a pedestal wafer into two pieces, the silicon pressure-sensitive element wafer is cut into two pieces. A groove having a V-shaped cross section is formed along the path to be cut, and then a silicon pressure-sensitive element wafer is bonded to a pedestal wafer to form a pressure sensor wafer. The pressure sensor wafer is cut along the groove with a cutting blade having a narrow width.

The silicon pressure-sensitive element converts pressure changes into electrical signals, and is made of a silicon material in which a piezoresistive element is arranged in a thin strain-generating part within a region surrounded by a peripheral thick part. .

It was. The grooves having the V-shaped cross section are for making it easier to cut out nine individual silicon pressure sensitive elements on the left side that individually partition the silicon pressure sensitive elements formed on the upper surface of the silicon pressure sensitive element wafer.

The formation of the grooves with the V-shaped cross section is performed using a chemical anisotropic etching technique such as alkaline etching.The above etching technique can form the grooves with the V-shaped cross section all over the wafer at once. There are advantages.

Moreover, as another means for forming the above-mentioned groove.

It is also possible to do it mechanically. That is, a concave groove is formed in advance on the upper surface of the silicon pressure-sensitive element wafer along the silicon pressure-sensitive element using a cutting blade having a convex cross section. This method is suitable for mass production because of its fast finishing speed.

Furthermore, V formed on the upper surface of the silicon pressure sensitive element wafer
The concave grooves having a letter-shaped cross section may be formed on the upper surface of the silicon pressure sensitive element wafer after forming a large number of silicon pressure sensitive elements by a diffusion technique and before bonding to the two-pedestal wafer.

In some cases, a silicon pressure-sensitive element is formed on the upper surface of the silicon pressure-sensitive element wafer, and a pedestal wafer is bonded to a position opposite to the silicon pressure-sensitive element by an electrostatic bonding method. A groove with a V-shaped cross section may be formed.

Yet again. The cutting blade used is a diamond blade, and only silicon pressure-sensitive element wafers are used.

Alternatively, the silicon pressure-sensitive element wafer and the pedestal are integrally cut with high precision.

When the above cutting blade is used, there is an advantage that the angle of the tip of the V-shaped groove can be freely formed by changing the other blade each time in each process.

Further, it is necessary that the cross section of the cutting blade has a width narrower than the maximum groove width of the V-shaped cross section. This is because the cutting blade cuts on the inclined surface of the V-shaped cross section.

Furthermore, the cross-sectional angle of the cut by the cutting blade on the silicon pressure-sensitive element wafer at the time of final cutting is as follows.

If the cross-sectional angle is small, pitching will increase, while if the cross-sectional angle is large, the crank may enter along the V-shaped groove arranged on the silicon pressure sensitive element wafer, so 100 @ ~ 160" is optimal. be.

(Effects of the Invention) In the present invention, the cut that appears on the surface of the silicon pressure-sensitive element wafer by dicing is formed by the intersection line of the slope forming the groove with a V-shaped cross section and the cut surface by dicing. forms an obtuse angle, therefore, it is possible to greatly suppress the occurrence of chipping and cranking caused by the impact of the cutting blade rotating at high speed.

Therefore, the yield of cutting the pressure sensor can be improved.

(Example) An example of the present invention will be described below with reference to FIGS. 3, 4, and 1.

[First Example] This example shows a method in which grooves are formed in advance on a pressure-sensitive element wafer, which is then bonded to a pedestal wafer, and then cut. This corresponds to the second invention.

FIG. 3 shows a cross-sectional view of a silicon pressure-sensitive element wafer l with grooves 4 formed therein before being bonded to a two-pedestal wafer.

Anisotropic etching using an alkaline solution was used to form the groove 4 having a V-shaped cross section.

That is, a silicon nitride film 2 with a thickness of approximately 2000 μm is formed on the surface of a silicon pressure-sensitive element wafer 1 having a (100) crystal plane by plasma CVD, and a silicon nitride film 2 with a width of approximately 150 μm extending in the (110) direction is formed by dry etching. Opening dicing line 3 0 Then dicing line 3
A groove 4 having a V-shaped cross section with a width of approximately 155 μm is formed by alkali etching. The crystal orientation of the silicon pressure-sensitive element wafer 1 is the (100) plane, and the dicing line 3 is (
110) direction in this example.

The two inclined surfaces 4a that constitute the groove 4 having a ``■'' cross section are as follows.

The tip of the groove 4, which has a V-shaped cross section and has an inclination angle of about 55@, can be formed to have an angle of about 70°.

FIG. 4 shows a cross-sectional view of a pressure sensor wafer 6 in which a silicon pressure-sensitive element wafer 1 and a pedestal wafer 5 are electrostatically bonded. Alternatively, it is formed by bonding a low melting point glass. The silicon pressure sensitive element wafer 1
The two pedestal wafers 5 have a thickness of 0.22 m and 1 m, respectively.
．． With 0 cranes.

The size of each wafer is approximately 3 inches in diameter and 3 inches square, respectively.

The silicon pressure-sensitive element wafer 1 is divided into grooves 4 having a grid-like V-shaped cross section with a width of about 155 μm drawn and formed on the surface thereof, and each division has a silicon pressure-sensitive element of about 3 fin angles. Element 8 is formed. A counterbore 9 is applied to the center portion of the silicon pressure-sensitive element 8 on the joint surface 7 side by alkali etching or the like.

A thin diaphragm lO is formed on its surface.

Generally, four diffused resistors acting as piezoresistive elements are arranged on the surface side of the diaphragm IO, and a well-known bridge circuit is formed by internal wiring. The pedestal wafer 5 is usually made of amorphous glass or crystallized glass, and each of the pedestals 5 corresponding to the silicon pressure-sensitive elements 8 formed in the silicon pressure-sensitive element wafer 1 has a plurality of pressure-sensitive elements. A pressure introduction port 11 having a diameter of about 1 day is formed through the pressure introduction port 11 so as to face the diaphragm 10 of No. 8.

The pressure sensor wafer 6 formed in this way is as follows.

As shown in FIG. 1, the pressure sensor chips 12 are pasted onto a support plate 13 and then cut into a plurality of pressure sensor chips 12 using a dicing device.

That is, first, a support plate 13 made of a silicon wafer having a circumferential size larger than that of the semiconductor pressure sensor wafer 6 is prepared, and wax 14 is applied to the lower surface of the pedestal wafer 5 of the semiconductor pressure sensor wafer 6 on the support plate 13. Paste. Next, before cutting, this pasted body is placed on a sample stage of a dicing device with the silicon pressure-sensitive element wafer l side facing up. Next, the semiconductor pressure sensor wafer 6 is positioned on the cutting table so that one of the grooves 4 having a V-shaped cross section with a width of about 155 μm etched on the surface of the silicon pressure sensitive element wafer l is at a predetermined cutting position. Then, using a resin blade with a width of 100 μm, cut a groove 15 along the center line of the concave groove 4 with a V-shaped cross section at a cutting speed of about 1/sec.
Form a notch.

Cutting grooves 15 are cut into support plate 13 by making cuts approximately 0.3u deep each time and repeating this 4 to 5 times.
reach. By performing this operation on all of the grooves 4 having a lattice-like V-shaped cross section formed on the silicon pressure sensitive element wafer 1, the semiconductor pressure sensor wafer 6 is cut into dice by the cutting grooves I5.

After the cutting operation is completed, the pasted body is transferred from the dicing device onto a heater plate, the wax 14 is softened, each pressure sensor chip 12 is individually separated and removed, and each pressure sensor chip 12 is washed with a predetermined solvent. Remove attached wax.

The obtained pressure sensor chip 12 is assembled into a desired package and electrically connected to form a semiconductor pressure sensor, and in this semiconductor pressure sensor, the diaphragm 10 is deflected due to the pressure difference between the inside and outside, increasing or decreasing the resistance value of each piezoresistive element. This allows the pressure to be detected as the output voltage of the bridge circuit.

Thus, the cut B on the surface of the silicon pressure-sensitive element wafer by the above-mentioned dicing is formed by the intersection line of the cutting groove 15 and the inclined surface 4a constituting the groove 4 having a V-shaped cross section. The cross-sectional angle θb of the cut B' forms an obtuse angle of approximately 145'. Therefore, the chipping and cranking that occur along the cut B by dicing 3 are greatly controlled, and the occurrence of defects due to these damages is almost eliminated. , the yield of the pressure sensor wafer 6 cutting process was significantly improved.

[Second Example] In this second example, a silicon pressure-sensitive element wafer l having a (110) crystal plane is used, and a groove 4 having a V-shaped cross section is formed in the (110) direction and the (100) direction perpendicular to this. Configure. 1st
A groove 4 having a V-shaped cross section is formed by alkali etching the dicing line 3 in the same manner as in the example, but in this case (the groove in the 1103 direction is approximately 35°
, [100] direction grooves are composed of inclined surfaces having an inclination angle of approximately 45@. By dicing these grooves, the cross-sectional angles of the cut ends of the silicon pressure-sensitive element wafer 1 are approximately 125° and 135@, respectively. Become. In the case of this second embodiment as well, chipping and cranking occurring at the cut end due to dicing were sufficiently reduced, and the yield of the pressure sensor wafer cutting process was improved.

In the first and second embodiments, since the pre-processing is performed at the wafer stage when the silicon pressure sensitive element wafer 1 is handled, there is an advantage that grooves having a V-shaped cross section can be formed all over the wafer at once by the photolithography process and the alkali etching process.

[Third Example] In this third example, the grooves of the dicing lines 3 were formed using a dicing device. In other words, as a pre-process, a blade with a thickness of 150 mm and a tip with a V-shaped cross section of approximately 90 inches is used.
Using a μm metal blade, cut approximately 75 μm along the dicing line of the silicon pressure-sensitive element wafer l, thereby forming grooves 4 with a V-shaped cross section on all dicing lines 3 on the silicon pressure-sensitive element wafer l. do. Continuing to cut using a resin blade with a thickness of 100 μm in the same manner as in the above example, approximately 135 mm
It was possible to form a cut with a cross-sectional angle of 100 mm, resulting in a high-yield cut with little chipping or cranking.

In this third embodiment, it is necessary to mechanically cut grooves with a V-shaped cross section on all dicing lines, but by changing the other blade each time in each process, the angle of the tip of the groove with a V-shaped cross section can be adjusted. 90″ mentioned above
Another advantage is that it can be formed relatively freely.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view of a pressure sensor wafer showing the dicing process of the method of the present invention, Fig. 2 is a cross-sectional view of a pressure sensor wafer without the conventional cutting method, and Fig. 3 is a silicon pressure-sensitive element subjected to alkali etching. A cross-sectional view of the wafer. FIG. 4 is a cross-sectional view of the pressure sensor wafer before dicing. l...Silicon pressure sensitive element wafer. 4... Groove with V-shaped cross section, 5... Pedestal wafer. 6... Pressure sensor wafer, 7... Bonding surface. 8... Silicon pressure sensitive element, 10... Diaphragm. 11...Pressure inlet, 12...Pressure sensor chip. 13... Support plate, 14... Wax, 15...
cutting groove. A/B...Cut.

Claims (1)

[Claims] (1) When individually cutting a pressure sensor wafer formed by bonding a silicon pressure-sensitive element wafer provided with a plurality of silicon pressure-sensitive elements to a pedestal wafer, the silicon pressure-sensitive element wafer is bonded to a pedestal wafer. to form a pressure sensor wafer, and then form a concave groove having a V-shaped cross section along the path to be cut on the silicon pressure-sensitive element wafer, and then form a concave groove having a V-shaped cross section narrower than the maximum groove width of the V-shaped cross section. A method for cutting a pressure sensor wafer, comprising cutting the pressure sensor wafer along the groove with a cutting blade having a width. (2) The method for cutting a pressure sensor wafer according to claim (1), wherein the groove having a V-shaped cross section is formed by anisotropic etching. (3) When individually cutting a pressure sensor wafer formed by bonding a silicon pressure-sensitive element wafer provided with a plurality of silicon pressure-sensitive elements to a pedestal wafer, follow the cutting path on the silicon pressure-sensitive element wafer. to form a concave groove having a V-shaped cross section, then bond the silicon pressure sensitive element wafer to the pedestal wafer to form a pressure sensor wafer, and then use a cutting blade having a width narrower than the maximum groove width of the V-shaped cross section. By,
A method for cutting a pressure sensor wafer, comprising cutting the pressure sensor wafer along the groove. (4) The method for cutting a pressure sensor wafer according to claim (3), wherein the groove having a V-shaped cross section is formed by a cutting blade having a cutting edge having a convex V-shaped cross section.