JPH0155970B2 - - Google Patents

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 together and separated into individual pressure sensor chips. By the way, the quality of processing results in dicing using a diamond blade depends on whether the cutting conditions, such as the type of blade used, the number of revolutions, and the cutting speed, are suitable for the material of the workpiece. Therefore, when cutting the pedestal wafer, which is usually several times thicker than the silicon pressure-sensitive element wafer, cutting conditions suitable for the pedestal wafer are selected. However, the cutting conditions selected here are often not necessarily appropriate conditions for the silicon pressure-sensitive element wafer that is to be cut at the same time. Therefore, when observing the individual pressure sensor chips obtained by the above-mentioned cutting, it is found that since the surface of the flat silicon pressure-sensitive element wafer was cut by dicing, the cross-sectional angle of the cut end was as shown by θa in Fig. 2. Therefore, chips and cracks called chipping exist along the cut edge of the silicon pressure-sensitive element in various sizes, and a decrease in the yield of pressure sensor chips due to this damage is a problem. Improvement measures were required.

(Objective of the Invention) The present invention has been made in view of the above-mentioned conventional problems, and its purpose is to reduce chipping and cracking that occur at the cut end of the surface of a silicon pressure-sensitive element wafer, and to improve the yield rate due to these damages. The present invention aims to provide a method for cutting a pressure sensor wafer that can improve the performance of the pressure sensor wafer.

(Structure of the Invention) The first method of the present invention is to individually cut 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. A pressure sensor wafer is constructed by bonding an element wafer to a pedestal wafer,
After that, a concave groove having a V-shaped cross section is formed along the path to be cut on the silicon pressure-sensitive element wafer, and then, using a cutting blade having a width narrower than the maximum groove width of the V-shaped cross section, The present invention is characterized in that the pressure sensor wafer is cut along the grooves.

Further, a second method of the present invention includes 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.
When individually cutting, a groove having a V-shaped cross section is formed on the silicon pressure-sensitive element wafer along the path to be cut, and then the silicon pressure-sensitive element wafer is bonded to a pedestal wafer to form a pressure sensor wafer. Then, the pressure sensor wafer is cut along the groove using a cutting blade having a width narrower than the maximum groove width of the V-shaped cross section.

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. .

Further, the groove having the V-shaped cross section is used to individually partition the silicon pressure sensitive elements formed on the upper surface of the silicon pressure sensitive element wafer and to facilitate cutting out the individual silicon pressure sensitive elements.

The formation of the groove having a V-shaped cross section is performed using a chemical anisotropic etching technique such as alkali etching. The above-mentioned etching technique has the advantage that grooves having a V-shaped cross section can be formed all over the wafer at one time.

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

Furthermore, the V-shaped cross-section groove formed on the top surface of the silicon pressure-sensitive element wafer is formed on the top surface of the silicon pressure-sensitive element wafer after forming a large number of silicon pressure-sensitive elements by diffusion technology and before bonding to the pedestal wafer. It's okay.

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 facing the silicon pressure-sensitive element by an electrostatic bonding method, and then the silicon pressure-sensitive element wafer is bonded. A groove having a V-shaped cross section may be formed on the upper surface.

Furthermore, when a blade having a V-shaped cross section is used, there is an advantage that the angle of the tip of the V-shaped groove can be freely formed by changing the blade each time in each process.

Further, the cross-sectional width of the cutting blade needs to be 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, when 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 small, pitting will occur more frequently, and conversely, if the cross-sectional angle is large, the cutting blade will not cut the silicon pressure-sensitive element wafer. Since cracks may occur along the V-shaped groove, the optimum angle is 100° to 160°.

(Effects of the Invention) In the present invention, the cut surface that appears on the surface of the silicon pressure-sensitive element wafer by dicing is formed by the intersection line of the inclined surface forming the groove with a V-shaped cross section and the cut surface by dicing. The cross section of the cut end forms an obtuse angle. Therefore, the occurrence of chipping and cracking caused by the impact of the blade rotating at high speed during cutting can be significantly suppressed. Therefore, the yield of cutting pressure sensor wafers can be improved.

(Example) Examples of the present invention are shown in FIGS. 3, 4, and 1.
It will be explained below with the help of figures.

[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.

Figure 3 shows the concave groove 4 before being bonded to the pedestal wafer.
1 shows a cross-sectional view of a silicon pressure-sensitive element wafer 1 on which a wafer 1 is formed.

Anisotropic etching using an alkaline solution was used as a method for forming the groove 4 having a V-shaped cross section.
In other words, approximately
A silicon nitride film 2 with a thickness of 2000 Å is formed, and by dry etching it extends approximately in the [110] direction.
A dicing line 3 with a width of 150 μm is opened. Next, the dicing line 3 is etched with alkali to form a groove 4 having a V-shaped cross section and a width of approximately 155 μm. In this embodiment, in which the crystal orientation of the silicon pressure-sensitive element wafer 1 is the (100) plane and the dicing line 3 is oriented in the [110] direction, the two inclined surfaces 4a constituting the groove 4 having a V-shaped cross section are approximately The angle at the tip of groove 4, which has a V-shaped cross section and forms an inclination angle of 55 degrees, is approximately
Can be formed at 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. 1.0
mm, and the size of each wafer is approximately 3 inches in diameter and 3 inches square, respectively.

The silicon pressure-sensitive element wafer 1 is partitioned by grooves 4 having a grid-like V-shaped cross section with a width of about 155 μm formed by etching on its surface, and each partition has a silicon plate of about 3 mm square. A pressure element 8 is formed. Further, the central portion of the silicon pressure sensitive element 8 on the side of the bonding surface 7 is subjected to a counterbore 9 by alkali etching or the like, and a thin diaphragm 10 is formed on the surface thereof. Further, on the surface side of the diaphragm 10, normally four diffused resistors acting as piezoresistive elements are arranged, and a well-known bridge circuit is formed by internal wiring. Further, 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 inlet 1 with a diameter of about 1 mm is placed opposite the diaphragm 10 of 8.
1 is formed through it.

Pressure sensor wafer 6 formed in this way
As shown in FIG. 1, the pressure sensor chips 12 are pasted on 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 that is one size larger than the semiconductor pressure sensor wafer 6 is prepared, and a wax 14 is placed on the support plate 13.
The lower surface of the pedestal wafer 5 in the semiconductor pressure sensor wafer 6 is attached using the following. Next, before cutting, this pasted body is placed on a sample stage of a dicing device with the silicon pressure sensitive element wafer 1 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 1 is at a predetermined cutting position. Thereafter, a cutting groove 15 is cut along the center line of the groove 4 having a V-shaped cross section at a cutting speed of about 1 mm/sec using a resin blade having a width of 100 μm. The cut groove 15 is made to reach the support plate 13 by making a cut to a depth of about 0.3 mm each time and repeating this 4 to 5 times. 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 15. .

After the cutting operation was completed, the adhesive was transferred from the dicing device onto a heater plate, the wax 14 was softened, each pressure sensor chip 12 was individually separated and removed, and the adhesive was washed with a prescribed solvent to adhere to each pressure sensor chip 12. Remove 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, thereby increasing or decreasing the resistance value of each piezoresistive element. The pressure can be detected as the output voltage of the bridge circuit.

The cut B on the surface of the silicon pressure-sensitive element wafer by the dicing is formed by the intersection line of the cutting groove 15 and the inclined surface 4a forming 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°. For this reason, chipping and cracking that occur along the cut edge B by dicing 3 are significantly controlled, so that the occurrence of defects due to these damages is almost eliminated, and the yield of the cutting process of the pressure sensor wafer 6 is significantly improved.

[Second Embodiment] In this second embodiment, a silicon pressure-sensitive element wafer 1 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 thereto. Configure. A groove 4 with a V-shaped cross section is formed by alkali etching the dicing line 3 in the same manner as in the first embodiment, but in this case, the groove in the [110] direction is approximately 35 degrees, and the groove in the [100] direction is By dicing these grooves, each of which is composed of an inclined surface having an inclination angle of approximately 45 degrees, the cross-sectional angles of the cut ends of the silicon pressure-sensitive element wafer 1 are approximately 125 degrees and 135 degrees, respectively. In the case of this second embodiment as well, chipping and cracking 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-process is performed at the wafer stage when the silicon pressure-sensitive element wafer 1 is handled, it is possible to form grooves with a V-shaped cross section over the entire surface of the wafer at once by the photolithography process and the alkali etching process. There are advantages.

[Third Example] In this third example, the grooves of the dicing lines 3 were formed using a dicing device. That is, as a pre-process, a cut of about 75 μm is made along the dicing line of the silicon pressure-sensitive element wafer 1 using a 150 μm thick metal blade with a V-shaped cutting edge with a tip of about 90°. V
Grooves 4 having a letter-shaped cross section are formed on all dicing lines 3 on the silicon pressure sensitive element wafer 1.
Subsequently, cutting was performed in the same manner as in the above example using a resin blade having a thickness of 100 μm, whereby a cut with a cross-sectional angle of about 135° was formed, and cutting with a high yield and less chipping and cracking was obtained.

In the 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, the tips of the grooves with a V-shaped cross section can be cut. It has the advantage that the angle can be formed relatively freely other than the above-mentioned 90°.

[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 showing a conventional cutting method, and FIG.
The figure is a cross-sectional view of a silicon pressure-sensitive element wafer subjected to alkali etching, and FIG. 4 is a cross-sectional view of a pressure sensor wafer before dicing. 1... Silicon pressure sensitive element wafer, 4... Groove with V-shaped cross section, 5... Pedestal wafer, 6... Pressure sensor wafer,
7... Joint surface, 8... Silicon pressure sensitive element, 10... Diaphragm, 11... Pressure introduction port, 12... Pressure sensor chip, 13... Support plate, 14... Wax, 15...
Cutting groove, A, B...cut, θa, θb...cross-sectional angle of the 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 the pedestal wafer. A pressure sensor wafer is constructed by forming a pressure sensor wafer, and then a concave 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 groove having a width narrower than the maximum groove width of the V-shaped cross section is formed. A method for cutting a pressure sensor wafer, comprising cutting the pressure sensor wafer along the groove with a cutting blade having a cutting blade. 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 a blade having a cutting edge having a V-shaped cross section. 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, a V is cut along the path to be cut on the silicon pressure-sensitive element wafer. A concave groove having a V-shaped cross section is formed, and then a silicon pressure sensitive element wafer is bonded to a pedestal wafer to form a pressure sensor wafer, and then a cutting blade having a width narrower than the maximum groove width of the V-shaped cross section is used. A method for cutting a pressure sensor wafer, comprising cutting the pressure sensor wafer along the groove. 4. The method of cutting a pressure sensor wafer according to claim 3, wherein the groove having a V-shaped cross section is formed by anisotropic etching.