JPH0476959A - Manufacture of semiconductor pressure sensor - Google Patents

Abstract

PURPOSE:To provide a semiconductor pressure sensor capable of high- temperature operation with good performance accuracy by forming an oxide film on a silicon substrate, converting polysilicon on the oxide film into single crystal, and introducing impurity to the single crystal to form diffused resistors that the electrically insulated from one another. CONSTITUTION:An oxide film 14 is formed on a silicon substrate 11 having a protruding seed 11a, which is used to convert polysilicon 15 deposited on the oxide film into single crystal. The single-crystal silicon is doped to form diffused resistors 15a-15d, and the other areas of the single-crystal than these resistors are removed. Since the diffused resistors are formed on the insulating film 12 in this manner, they are electrically insulated from one another. According to this method, it is easy to provide a low-cost pressure sensor capable of stable operation in a high-temperature atmosphere and having good performance and accuracy. Simultaneously with forming the diffused resistors, impurity can be introduced in different concentration to form diffused leads so that different metallic parts may be eliminated. As a result, thermal stress at high temperature is relaxed, and temperature drift is reduced.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method of manufacturing a semiconductor pressure sensor, in particular, a method of manufacturing a semiconductor pressure sensor, in particular, forming a diaphragm by thinning a part of a silicon substrate.
A method for manufacturing a semiconductor pressure sensor in which a resistor is formed on a silicon substrate corresponding to the diaphragm, the resistor is deformed together with the silicon substrate by pressure applied to the diaphragm, and pressure is measured by detecting a change in resistance value due to this deformation. It is related to.

[Conventional technology]

FIG. 6 is a diagram showing a conventional method of manufacturing a semiconductor pressure sensor disclosed in, for example, Japanese Patent Application Laid-Open No. 63-156365, in which a silicon Using the oxide layer 2 as a mask, etching is performed to form the recess 3 (FIG. 6a) (FIG. 6b).

On the other hand, a silicon oxide layer 5 is formed in a predetermined region on the main surface of the second single crystal silicon substrate 4 (FIG. 6g), and a resistive layer 6 is formed using this silicon oxide layer 5 as a mask. Subsequently, after removing the silicon oxide layer 5, silicon nitride H7 is formed on the front surface of the main surface of the second single crystal silicon substrate 4, and a BPSG layer 8 is further formed on this (FIG. 6d).
).

Then, the BPSG 1 formed on the second single crystal silicon substrate 4 is aligned on the main surface of the first single crystal silicon substrate 1 so that the upper and lower patterns overlap as set.
18 (Fig. 6e).

Thereafter, the second single crystal silicon substrate 4 is removed by etching (FIG. 6f), and a surface protection layer 9 and a wiring layer 10 are formed (FIG. 6g) to form a semiconductor pressure sensor.

[Problem to be solved by the invention J] The conventional method for manufacturing a semiconductor pressure sensor is carried out as described above, so two silicon substrates are prepared, an oxide layer is formed on one silicon substrate, and an oxide layer is formed on the other silicon substrate. After making the surfaces of the silicon substrates mirror-like, they are bonded together by anodic bonding, which inevitably requires two silicon substrates, which poses a cost problem from the start.

Furthermore, it is necessary to finish the surface of the silicon substrate to a mirror finish, and the yield is influenced by this finished state. Moreover, after bonding the two silicon substrates together, it is necessary to polish the surfaces, but since the amount of polishing is large, there are problems such as difficulty in obtaining accurate surface flatness.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a method of manufacturing a semiconductor pressure sensor that can inexpensively obtain a semiconductor pressure sensor with guaranteed performance accuracy.

[Means to solve the problem]

The method for manufacturing a semiconductor pressure sensor according to the invention described in claim (1) includes a seed part forming step of forming a convex seed part on the surface of a silicon substrate, and a step of forming a polysilicon layer on an oxide layer provided on the surface of the silicon substrate. After sequentially depositing a silicon layer and a nitride layer, a recrystallization process is performed in which a laser is irradiated and scanned to melt and recrystallize the polysilicon layer to form a single crystal silicon layer, and a portion that will become a diffusion resistance is left behind. After removing the single crystal silicon layer by etching, a resistor forming step was performed in which impurities were injected into the remaining portion to form a diffused resistor, and the oxide layer in the portion that would become the contact was removed to form a metal layer on the entire surface. Thereafter, a wiring forming step of removing the metal layer leaving a wiring region, a protective layer forming step of forming an insulating layer on the entire surface other than the contact portion to serve as a protective layer, and a step of forming the silicon substrate corresponding to the diffused resistor. This process consists of a diaphragm forming step in which a diaphragm is formed by isotropically etching the back surface of the diaphragm.

The invention as evidenced in claim 2 etches and removes the single crystal silicon layer leaving a portion that will become a diffused resistor and a diffused lead, and then implants impurities into the remaining portion to form a diffused resistor and changes the amount of the implanted impurity. The method includes a diffusion resistor for forming diffusion leads and a diffusion lead formation process.

Further, the invention as claimed in claim 3 provides that after removing the oxide layer in the portion that will become the contact and forming the metal layer on the entire surface except for the portion corresponding to the seed portion, the metal layer is removed leaving the wiring area. This includes a wiring forming process for removing.

[Function] The method for manufacturing a semiconductor pressure sensor according to the invention described in claim 1 includes forming an oxide layer on a silicon substrate on which a convex seed portion is formed, and depositing polycrystalline silicon on the oxide layer on the seed portion. After forming a plurality of diffused resistors by implanting impurities into the single crystal silicon 1, by removing the single crystal silicon layer other than the diffused resistor part, the diffused resistors are formed on the insulating layer which is an oxide layer. The diffused resistors are electrically insulated from each other. As a result, a semiconductor pressure sensor that can stably operate even in a high-temperature atmosphere and has guaranteed performance accuracy can be obtained at low cost by a simple manufacturing method.

In the invention set forth in claim 2, by forming the diffused leads by changing the amount of implanted impurities at the same time as forming the diffused resistor in the invention set forth in claim 1, there is no dissimilar metal part, so that heat can be maintained even in a high temperature atmosphere. Stress is relaxed and temperature drift can be reduced.

Further, in the invention according to claim 3, by not providing a wiring area in a portion corresponding to the seed portion,
It can maintain high voltage resistance and can operate stably even in high-temperature atmospheres.

[Example] Hereinafter, an example of the present invention will be described with reference to the drawings. 1st
In the figure, 11 is an N-type silicon substrate, 12 is an underlying oxide layer, 13 is a nitride layer, 14 is an oxide layer, 15 is a polysilicon layer, 16 is a nitride layer, 17 is an antireflection layer, 18 is a high temperature oxide layer, 19 is aluminum counterfeit as a metal layer, 2
0 is a glass coat layer as a protective layer.

Next, the manufacturing method of the above embodiment will be explained.

A 500-thick underlayer oxide (SiOa) 12 is formed on one layer of N-type silicon (Si) substrate (5T1), and an 800-thick nitride layer (Si, N4) is formed on top of the underlayer oxide (SiOa) 12.
13 is deposited (ST-2).

The nitride layer 1 is left with a portion corresponding to the seed portion 11a.
3. The underlying oxide layer 12 and the N-type silicon substrate 11 are sequentially etched away (ST-3 to ST-5). in this case,
The etching amount H1 of the N-type silicon substrate 11 is approximately 3,500.

Next, after removing the resist 21 on the remaining nitride layer 13 (ST-6), an oxide layer 14 with a thickness T=1.1 μm is formed on the N-type silicon substrate layer by thermal oxidation (ST-6).
-7). The remaining nitride layer 13 is removed, the remaining underlying oxide layer 12 is removed, and the oxide layer 14 is removed.
The surface is flattened by etching away by about 0.1 μm (ST-8, 5T-9).

Thereafter, a polysilicon layer 15 is deposited to a thickness of 5000 on the oxidized N14 (5T-10), and a nitride layer 1 is deposited on it.
6 to a thickness of 500 mm (5T-11), and this nitride layer 1
The resist 22 is etched away so that 6 remains on the stripe to form an antireflection layer 17 (ST-12, S
T-13).

Next, a laser (not shown) (argon laser) is irradiated and scanned from above to melt the polysilicon layer 15 and then recrystallize it into a single crystal (ST-14). After that, the antireflection layer 17 and the nitride layer 16 are removed (ST-15
).

The recrystallized polysilicon layer 15 is removed by etching together with the resist 23, leaving a portion that will become a diffusion resistance (ST-16, ST-17).

Impurities (for example, boron) are added to the remaining polysilicon layer 5.
is implanted to form a plurality of diffused resistors 15a to 15d (ST
-18), as a result, a plurality of diffused resistors can be formed on the insulating layer, which is an oxide layer, in an electrically isolated state, and then an oxide layer 14 is formed to cover the diffused resistors.
A high temperature oxide layer 18 is deposited on the entire surface (ST-19).

Next, after removing the high-temperature oxide layer 18 that will become the contact together with the resist layer 23 (ST-20
>, remove the resist layer 23 by etching (ST-21
). After that, an aluminum layer 19 is formed on the entire surface (5T-22), and other parts and the resist layer 24 are removed by etching, leaving the aluminum layer 19 corresponding to the wiring area (ST-23, 5T24). A protective layer 20 (ST-25) is applied to the entire surface by glass coating.

Thereafter, a part of the protective layer 20 is removed by etching to form an electrode pad 29, and the back surface of the N-type silicon substrate 1 is polished to form a wafer with a desired thickness, and gold (Au) 25 is deposited on the back surface. (ST-26), remove the gold 25 and resist 26 in the portion that will become the diaphragm (5T-27, 5T-28), and use the remaining gold 25 as a mask to etch the back surface of the N-type silicon substrate 11. A thin wall portion 27 is removed to form a diaphragm (ST
-29).

Here, the above ST-1 to ST-5T-9 are seed part forming steps,
ST-10 to ST-15 are recrystallization steps, ST-16 to
5T-18 is the diffusion resistance forming process 5T-19 to 5T-25
5T-26 to 5T-29 represent a wiring forming process and a diaphragm forming process.

In addition, the above 5T-3, 5T-12, ST-16, 5T-
Resist layers 21 to 24.26 in 23,5T-27
is applied during mask matching (pattern matching) for etching in each pre-stage. This will serve as a mask for etching.

By the above manufacturing method, multiple diffused resistors made of single crystal silicon can be formed on an insulating layer formed on a semiconductor silicon single crystal substrate in a mutually electrically insulated state, and are stable even in a high temperature atmosphere. A semiconductor pressure sensor that can be operated in this manner is obtained.

In addition, in the above manufacturing method, when forming a diffused resistor by injecting impurities into single crystal silicon, a high concentration of impurities is injected into the single crystal silicon to form a low resistance diffused lead 28 as shown in FIGS. 2 and 3. By forming and wiring as shown, the diffused resistors 15a to 15d can be connected to each other.

Reference numeral 29 denotes an electrode pad for connecting an external lead, which is made of an aluminum layer and formed on a part of the diffusion lead 28.

Furthermore, in the above manufacturing method, as shown in FIGS. 4 and 5, the wiring region 19 in the portion corresponding to the seed portion 11a is
By making a hole 30 in the hole 30 and not providing a wiring region in a portion corresponding to the seed portion 11a, high voltage resistance can be maintained and stable operation can be achieved even in a high temperature atmosphere.

[Effects of the Invention] As described above, according to the invention described in claim 1, an oxide layer is formed on a silicon substrate on which a convex seed portion is formed, and the polycrystalline silicon deposited on this oxide layer is The seed part is melted and recrystallized to form a single crystal, and impurities are injected into this single crystal silicon layer to form a diffused resistance, and the remaining single crystal silicon layer is removed. A plurality of electrically insulated diffused resistors are formed. As a result, a semiconductor pressure sensor that can stably operate even in a high-temperature atmosphere and has guaranteed performance accuracy can be obtained at low cost by a simple manufacturing method.

Further, according to the invention as claimed in claim 2, by forming a plurality of diffused resistors on the insulating layer and at the same time forming diffused leads that connect the diffused resistors, the presence of dissimilar metal parts is avoided. As a result, thermal stress can be relaxed even in a high-temperature atmosphere, and temperature drift can be reduced.

According to the invention described in claim 3, by not providing a wiring area in the portion corresponding to the seed portion, high voltage resistance can be maintained and stable operation is possible even in a high temperature atmosphere. Effects such as this can be obtained.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing a method for manufacturing a pressure sensor according to an embodiment of the invention as claimed in claim 1, and FIG. 2 is a plan view of essential parts showing a method for manufacturing a pressure sensor according to an embodiment of the invention as claimed in claim 2. , FIG. 3 is a sectional view thereof, FIG. 4 is a plan view of essential parts showing a method for manufacturing a pressure sensor according to an embodiment of the invention as claimed in claim 3, FIG. 5 is a sectional view thereof, and FIG. 6 is a conventional method for manufacturing a pressure sensor. It is an explanatory view explaining a manufacturing method of a pressure sensor. 11 is a silicon substrate, lla is a seed part, 14 is an oxide layer, 15 is a polysilicon layer, 15a to 15d are diffused resistors,
16 is a nitride layer, 19 is an aluminum WI (metal layer),
20 is a glass coat layer (protective layer), 28 is a diffusion lead,
30 is a hole. In addition, in the figures, the same reference numerals indicate the same or corresponding parts. Figure 1 (¥1) Figure 1 (¥04)

Claims (3)

[Claims] (1) Seed part forming step of forming a convex seed part on the surface of the silicon substrate, and after sequentially depositing a polysilicon layer and a nitride layer on the oxide layer provided on the surface of the silicon substrate, laser irradiation is performed. , a recrystallization step in which the polysilicon layer is melted and recrystallized by scanning, and after the single crystal silicon layer is etched away leaving a portion that will serve as a diffusion resistance, impurities are injected into the remaining portion and diffused. A diffusion resistor formation step for forming a resistor, a wiring formation step for removing the oxide layer in the portion that will become the contact and forming a metal layer over the entire surface, and then removing the metal layer leaving the wiring area; Manufacturing a semiconductor pressure sensor comprising a protective layer forming step of forming a protective layer made of an insulating material over the entire surface, and a diaphragm forming step of isotropically etching the back surface of a silicon substrate corresponding to the diffused resistor to form a diaphragm. Method. (2) Seed part forming step of forming a convex seed part on the surface of the silicon substrate, and after sequentially depositing a polysilicon layer and a nitride layer on the oxide layer provided on the surface of the silicon substrate, laser irradiation is performed. , a recrystallization step of scanning to melt and recrystallize the polysilicon layer to form a single-crystal silicon layer, and etching away the single-crystal silicon layer leaving a portion that will become a diffusion resistor and a diffusion lead, There is a diffusion resistance and diffusion lead formation process in which impurities are implanted into the remaining portion to form a diffusion resistance, and diffusion leads are formed by varying the amount of implanted impurities. After removing the oxide layer in the portion that will become the contact, Manufacturing a semiconductor pressure sensor comprising a protective layer forming step of forming a protective layer made of an insulating material over the entire surface, and a diaphragm forming step of isotropically etching the back surface of a silicon substrate corresponding to the diffused resistor to form a diaphragm. Method. (3) Seed part forming step of forming a convex seed part on the surface of the silicon substrate, and after sequentially depositing a polysilicon layer and a nitride layer on the oxide layer provided on the surface of the silicon substrate, laser irradiation is performed. , a recrystallization step of scanning to melt and recrystallize the polysilicon layer to form a single-crystal silicon layer, and etching away the single-crystal silicon layer leaving a portion that will become a diffusion resistance, and then removing the remaining portion. After removing the oxidized layer in the part that will become the contact and forming a metal layer on the entire surface except for the part corresponding to the seed part, the wiring area is a wiring forming step of removing the metal layer leaving behind a portion of the metal layer; a protective layer forming step of forming a protective layer made of an insulating material on the entire surface other than the contact; and isotropic etching of the back surface of the silicon substrate corresponding to the diffused resistor. A diaphragm forming step of forming a diaphragm.