JPH0419712B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a semiconductor pressure sensor, and more particularly to a method for manufacturing a standard pressure sensor for an automobile.

[Conventional technology]

In general, standard pressure type pressure sensors for automobiles are made by diffusing impurities such as boron on one side of a silicon diaphragm to form a strain gauge, as shown in Japanese Patent Laid-Open No. 55-52925, for example. In order to determine the reference pressure of the strain gauge, a reference pressure chamber is provided by airtightly bonding a cap made of horosilicate glass. The airtightness of the bond between the silicon diaphragm and the borosilicate glass cap allows the standard pressure (usually vacuum, but may also be an inert gas with an extremely small coefficient of thermal expansion) to be maintained for a long period of time. This has a significant impact on Therefore, since the coefficient of thermal expansion of silicon, which is the material of the diaphragm, and that of homosilicate glass, which is the material of the cap, are almost the same, we heated them to about 400°C and created a bond between the two materials. The best way to bond silicon diaphragms and horosilicate glass caps is by electrostatic bonding, which can be airtight, strong, and strain-free without adhesive by applying a voltage of approximately 1000V. There is. Therefore, regarding electrostatic bonding and other bonding methods,
The flatness of the bonded surfaces is required, meaning that the surface roughness of the bonded surfaces of the two materials to be bonded must be 1 μm or less. Further, even when the borosilicate glass cap is not bonded, if dust or the like adheres to the strain gauge forming surface, desired accuracy cannot be achieved, so a certain surface roughness is required.

Such sensor chips have conventionally been manufactured by the following method. That is, first, on both sides of a round semiconductor (silicon) wafer,
Form an oxide film. The front side of the silicon wafer is a passivation film, and the back side is for masking. Second, hundreds of pressure sensor chips are formed on a silicon wafer, with strain gauges formed on one side of each chip. Third, the oxide film in the window for the silicon diaphragm is removed from the other side of the silicon wafer. When this window is opened,
Fourth, a diaphragm is formed by alkali etching. With this alkali etching, for example, the etching rate is fast for a silicon single crystal with 100 planes, but it is slow for the 111 plane orientation, so by taking advantage of this fact, it is possible to create an etched shape such as a dome. It has gained.

Once the diaphragm is formed, the fifth step is to separate the silicon wafer into individual chips. Several methods are used for this division.
One of them is a method of damaging the wafer using a scriber called scribing and then breaking the wafer. Breaking was done by placing the scribed wafer on a tape and pressing a roller over it to break it.

Another method is to attach the wafer to a silicon pedestal with wax after forming the diaphragm, and then cut the wafer to the pedestal with a dicer. When the chips are separated into chips using these methods, the sixth step is to dip them in a solvent that dissolves adhesive or wax when cutting with tape, or remove the chips from the tape or pedestal. Remove one by one. After the chips are divided into chips, the dummy silicon plate is waxed again, the chips are arranged on top of the dummy silicon plate, and both sides are mechanically cleaned to obtain a predetermined surface roughness.

[Problem to be solved by the invention]

In this way, conventional semiconductor pressure sensors have undergone the above-mentioned steps in manufacturing. According to such conventional methods, when braking is performed after scribing, chipping (roughness of the cut end with cracks) occurs when braking, which is not a big problem in the case of elements such as diodes, but pressure In cases such as sensors, residual distortion is a problem, so it is better to cut it out completely. That is, the method involves applying wax to a silicon pedestal, placing a wafer on top of it, and making a cut up to the silicon pedestal to completely cut it out.

However, with this method, it is possible to achieve accuracy as a pressure sensor, but when the blade cuts the wafer and reaches the wax underneath, the wax melts due to the frictional heat generated by the rotation of the blade. Silicon and contamination (silicon chips) generated when cutting the silicon wafer get mixed into the wax, and the water that is applied while cutting with a blade causes the wax to solidify again, still containing the silicon contamination. I end up. After this, in order to separate the silicon wafer from the silicon pedestal, the wax is dissolved with an organic solvent, but at this time,
The silicon contamination that was mixed in the wax gets mixed into the organic solvent, causing a phenomenon in which it adheres all over the chip. For this reason, it becomes necessary to mechanically polish the chips after they are taken out, which poses a problem.

An object of the present invention is to provide a method for manufacturing a semiconductor pressure sensor that can reduce manufacturing steps, reduce chipping, and reduce silicon contamination.

[Means to solve the problem]

In order to achieve the above object, the present invention includes a first step of forming an oxide film on both sides of a silicon wafer, and a second step of forming a strain gauge on one side of the silicon wafer on which the oxide film is formed. a third step of removing the oxide film for forming a diaphragm on the other side of the silicon wafer and for forming a V-groove of a predetermined width around the silicon diaphragm;
a fourth step of simultaneously forming a diaphragm and a V-groove by alkali etching; a fifth step of attaching the alkali-etched surface of the silicon wafer on the diaphragm side to a tape; a sixth step of forming a groove with a substantially constant width in the depth direction and a depth of approximately half the thickness of the silicon wafer by cutting at a position corresponding to the V-groove on the side surface; and applying stress. A method of manufacturing a semiconductor pressure sensor includes a seventh step of forming a chip by braking, and an eighth step of separating the chip from the tape in an organic solvent after braking.

[Effect]

When forming the diaphragm by etching, it also makes braking easier, prevents variations in chip shape, and prevents cracks.
Furthermore, it is possible to prevent the generation of residual stress.
In addition to forming a groove, braking is performed with a cut groove of approximately constant width formed by mechanical cutting from the surface opposite to the corresponding position of the V-groove, so that the number of manufacturing steps can be reduced. Furthermore,
Chipping (roughness of the cut end with cracks) can be reduced, and silicon contamination can be reduced.

In particular, since braking is performed with the sharp shape of the deepest part of the "V groove" and the "kerf" of a certain width formed, the force during braking is concentrated on the sharp part, resulting in a clean cut surface. There is less risk of problems such as residual distortion caused by excessive braking.

〔Example〕

Examples of the present invention will be described below.

FIG. 1 shows one step of an embodiment of a method for manufacturing a reference pressure type pressure sensor according to the present invention.

In the figure, a diffused resistor such as boron is diffused on the upper surface of a diaphragm 5 formed on one surface of a silicon substrate 1, and this diffused resistor forms a strain gauge 2 on the upper surface of the diaphragm 5. . A passivation 3a, which is an oxide film, is formed on the other surface of the silicon substrate 1. Furthermore, a passivation 3b, which is an oxide film, is also formed on one surface of the silicon substrate 1. Further, the strain gauge 2 is provided with an electrode 4. Furthermore, a V-groove 6 is provided on the diaphragm formation side of the silicon substrate 1 at a location corresponding to the size of the chip formation area.

The manufacturing method up to this point is as follows.

(1) Passivation, which is an oxide film, is formed on both sides of the silicon substrate 1.

(2) Form a strain gauge 2 on one surface of the silicon substrate 1.

(3) Remove the oxide film on the other side of the silicon substrate 1 that is large enough to be etched with alkali. That is, windows are opened for the diaphragm 5 and the V-groove 6 formed by alkali etching.

(4) The portion of the silicon substrate 1 from which the oxide film was removed is etched with alkali to form the diaphragm 5
A depth of 50 μ formed around this diaphragm 5
A V-groove 6 having a diameter of m or less is formed.

The process that has been completed up to the above steps is shown in FIG. This is shown for one chip, but when the entire silicon wafer is viewed from the diaphragm forming side, it becomes as shown in FIG.

Next, the silicon wafer shown in FIG. 1 is pasted on tape 8 with adhesive 7 and cut with a dicer to form cutting grooves 9, as shown in FIG. 3. The steps up to FIG. 3 are shown as follows following the steps shown in FIG. 1.

(5) Attach the diaphragm 5 forming surface of the silicon substrate 1 to the tape 8 to which the adhesive 7 is attached.

(6) Half cut silicon substrate 1 with a thickness of approximately 180 μm by dicing etc.
A 90 μm incision, that is, a cutting groove 9, is formed in about half of the area. The position of the cutting groove 9 corresponds to the V-groove 6.

The subsequent steps are: (7) Apply stress to the tape 8 and scrape it to form each chip.

(8) Remove the tape adhesive from each chip using an organic solvent.

It is.

The semiconductor pressure sensor thus formed is used as shown in FIG. That is, a silicon substrate 1 is mounted on a die 10 having a pressure introduction port, and the die 10 is fixed by an adhesive 12 to a casing 11 to which a lead frame 14 is attached. At the top of this casing 11,
A cap 15 is attached. Further, the electrode 4 formed on the silicon substrate 1 and the lead frame 14 are connected by a wire 13.

Therefore, according to this embodiment, since the silicon wafer is not completely cut out by dicing, silicon contamination does not dissolve into the wax. Therefore, the silicon chip is not contaminated during the wax removal process, and no mechanical polishing process is required.

〔Effect of the invention〕

According to the present invention, when forming a diaphragm by etching, a V-groove is formed at the same time to facilitate braking, prevent variations in chip shape, prevent the occurrence of cracks, and furthermore prevent the generation of residual stress. At the same time, since braking is performed with a cut groove of approximately constant width formed by mechanical cutting from the surface opposite to the position corresponding to the V-groove, the number of manufacturing steps can be reduced. Furthermore, chipping (roughness of the cut end with cracks) can be reduced, and silicon contamination can be reduced.

In particular, since braking is performed with the sharp shape of the deepest part of the "V groove" and the "kerf" of a certain width formed, the force during braking is concentrated on the sharp part, resulting in a clean cut surface. There is less risk of problems such as residual distortion caused by excessive braking.

As described above, according to the present invention, the number of manufacturing steps can be reduced, chipping can be reduced, and silicon contamination can be reduced.

[Brief explanation of drawings]

FIG. 1 is a structural diagram of a pressure sensor in one process showing an embodiment of the present invention, FIG. 2 is an overall view of a silicon wafer in the process shown in FIG. 1, and FIG. Structure diagram of the pressure sensor showing the subsequent process, No. 4
The figure is an overall configuration diagram in which a pressure sensor manufactured according to an embodiment of the present invention is incorporated into an apparatus. 1...Silicon substrate, 2...Strain gauge, 3a,
3b...passivation, 4...electrode, 5...
Diaphragm, 6...V groove, 9...cutting groove.

Claims (1)

[Claims] 1 A first step of forming an oxide film on both sides of a silicon wafer, and a second step of forming a strain gauge on one side of the silicon wafer on which the oxide film is formed.
a third step of removing the oxide film for forming a diaphragm on the other side of the silicon wafer and for forming a V groove of a predetermined width around the silicon diaphragm; a fourth step of simultaneously forming grooves; a fifth step of attaching the diaphragm side of the alkali-etched silicon wafer to the tape; and a fifth step of attaching the alkali-etched silicon wafer to the tape, corresponding to the V-grooves on the opposite side of the tape. a sixth step of forming a kerf with a substantially constant width in the depth direction and a depth of approximately half the thickness of the silicon wafer by cutting at the position; and a seventh step of forming a chip by applying stress and braking. and an eighth step of removing the chip from the tape in an organic solvent after braking.