JPH07240395A - Method for manufacturing semiconductor device - Google Patents

Abstract

PURPOSE:To easily eliminate a retaining structure in a short time, by using an N-type semiconductor substrate, diffusing phi type impurities in the surface part of the semiconductor substrate except at least a retaining structure forming position, irradiating a specified light in specified reaction gas, and eliminating the retaining structure by etching. CONSTITUTION:A cantilever 2 and a peripheral frame part are connected by a retaining structure 3. On the surface of a silicon substrate 1, the conductivity type of only the retaining structure 3 part is N-type, and that of the other part is P-type. Since a P-type layer 5 is formed on the surface of the part except the retaining structure 3, electrons are not formed in the case of light irradiation and the reaction with NF3 gas as the reaction gas is not induced. On the contrary, electrons are formed in the N-type retaining structure 3 in the case of light irradiation, so that etching reaction is induced as the result of reaction with NF3 gas. Hence only the N-type retaining structure 3 part is etched and eliminated by light irradiation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a semiconductor device having a cantilever used as a detecting portion such as an acceleration sensor, a pressure sensor and an ultrasonic sensor.

[0002]

2. Description of the Related Art A semiconductor sensor, for example, a semiconductor acceleration sensor, applies a force generated by acceleration to a cantilever made of, for example, a silicon thin plate by some method, and detects the deflection of the cantilever caused by the acceleration. To detect. The process technology developed for semiconductor devices is applied to the manufacture of this minute cantilever, and silicon is often used as a thin plate material. Semiconductor device process technologies such as photolithography and etching enable simultaneous mass production of semiconductor sensors with cantilevers on a silicon wafer.

FIGS. 3B and 3C show an example of a semiconductor device having a cantilever. (B) is a perspective view of the silicon substrate 1, and (c) is the silicon substrate 1 shown in (b).
FIG. In FIGS. 3B and 3C, 1 is a silicon substrate, 2 is a cantilever, 1 a is a cantilever 2.
Is a cavity formed below. In order to actually use it as a sensor element, a large number of silicon substrates 1 are formed on a wafer and then separated and attached to a package or the like. However, since the cantilever 2 that is a movable part is very fragile, a separation process by a subsequent dicing or the like is performed. In addition, it is often damaged during the assembly process of attaching to the package or the bonding process for wiring, and while the sensor element with a built-in cantilever greatly contributes to downsizing, it is fragile and costly. There was a problem.

Therefore, as shown in FIG. 3 (a), the cantilever 2 formed on the silicon substrate 1 is supported and mechanically reinforced by the support structure 3, and the separation process by dicing or the assembly process or wiring for attaching to the package is performed. After the process of impacting the cantilever such as the bonding process for irradiating the supporting structure 3 of the sensor element with a focused argon ion laser in a reaction gas atmosphere such as NF ₃ , the laser irradiation causes heating. By inducing a thermochemical reaction between the reaction gas and silicon, as shown in FIG.
A method has been proposed in which the supporting structure 3 is removed as shown in (b) and FIG. 3 (c) (Proc. IEEE MEMS,
pp.53-59 (1993 Feb)). According to this manufacturing method, the cantilever 2 which is easily damaged by mechanical impact is reinforced with the support structure 3 until mechanical reinforcement is unnecessary, and when the reinforcement is no longer needed, the argon that is focused on the support structure 3 is collected. The cantilever 2 can be freed by irradiating it with laser light in a reaction gas and removing it by etching. In this way, it becomes possible to protect the cantilever 2 from the mechanical shock generated in the manufacturing process.

[0005]

As described above, in the sensor element having the silicon cantilever 2, the support structure 3 is provided until the step of mechanically impacting the cantilever 2 is completed, and those steps are performed. After completion of the above, by irradiating the sensor element with a laser focused in a reaction gas atmosphere, damage during the dicing process, the assembly process or the bonding process can be prevented. However, there is a problem that a lot of time is required because it is necessary to align the respective support structures 3 with each other and perform laser irradiation with respect to the assembled sensor element.

The present invention has been made in view of the above problems,
An object of the invention is to provide a method of manufacturing a semiconductor device having a cantilever, which can easily remove a supporting structure and in a short time.

[0007]

In order to achieve the above object, a method of manufacturing a semiconductor device according to claim 1 is a method of manufacturing a semiconductor device having a cantilever, wherein the cantilever is mechanically formed only in the manufacturing process. In a method of manufacturing a semiconductor device, including a step of providing a supporting structure for reinforcement to and removing the supporting structure when it is no longer needed, an n-type semiconductor substrate is used, and at least the surface of the semiconductor substrate excluding the supporting structure forming position. The method is characterized by including a step of diffusing a p-type impurity in a portion and a step of irradiating a predetermined light in a predetermined reaction gas to remove the support structure by etching.

A method of manufacturing a semiconductor device according to a second aspect of the present invention is a method of manufacturing a semiconductor device having a cantilever, in which a supporting structure for mechanically reinforcing the cantilever is provided only in the manufacturing process, which is unnecessary. In a method of manufacturing a semiconductor device, including the step of removing the support structure at
Using a p-type semiconductor substrate, diffusing n-type impurities in a portion of the semiconductor substrate that will be the support structure, and irradiating predetermined light in a predetermined reaction gas to remove the support structure by etching. It is characterized by including and.

A method of manufacturing a semiconductor device according to a third aspect of the present invention is a method of manufacturing a semiconductor device having a cantilever, wherein a supporting structure for mechanically reinforcing the cantilever is provided only in the manufacturing process, which is unnecessary. In a method of manufacturing a semiconductor device, including the step of removing the support structure at
The conductive type of the portion forming the support structure is n-type, and a step of amorphizing the surface portion of the semiconductor substrate other than the portion forming the support structure is performed, and a predetermined light is irradiated in a predetermined reaction gas. A step of removing the support structure by etching.

Further, the method of manufacturing a semiconductor device according to a fourth aspect is a method of manufacturing a semiconductor device having a cantilever, wherein a supporting structure for mechanically reinforcing the cantilever is provided only in the manufacturing process, and it is not necessary. In a method of manufacturing a semiconductor device including a step of removing the support structure at a point of time, a conductivity type of a portion forming the support structure is n-type,
Amorphizing the surface of the semiconductor substrate, recrystallizing only the surface portion of the semiconductor substrate forming the support structure by local annealing, irradiating a predetermined light in a predetermined reaction gas, and And a step of removing the support structure by etching.

[0011]

According to the method of manufacturing a semiconductor device of the present invention, when the support structure formed on the n-type semiconductor substrate is removed by etching, p is formed on the surface of the semiconductor substrate which is not removed by etching.
By forming the mold layer, it is possible to prevent electrons from being generated on the surface of the semiconductor substrate by light irradiation and to cause an etching reaction with the reaction gas, and selectively remove only the support structure by etching. Further, since only the support structure can be removed by etching by irradiating the sensor element with predetermined light in the reaction gas, a large number of sensor elements can be manufactured at one time.

A method of manufacturing a semiconductor device according to claim 2 is
An n-type impurity is introduced into a portion of a support structure formed on a p-type semiconductor substrate, the portion of the support structure is previously set as an n-type region, light is irradiated in a reaction gas, and the n-type region is irradiated by light irradiation. The reaction gas reacts with the electrons generated on the surface of the support structure to selectively etch and remove only the part of the support structure. Further, since only the support structure can be removed by etching by irradiating the sensor element with predetermined light in the reaction gas, a large number of sensor elements can be manufactured at one time.

A method of manufacturing a semiconductor device according to claim 3 is
By amorphizing the surface portion other than the portion forming the support structure of the semiconductor substrate in advance, it is possible to prevent electrons from being generated by light irradiation on the surface of the portion of the semiconductor substrate which is not removed by etching and reacting with the reaction gas by etching. , Only the support structure is selectively removed by etching. Further, since only the support structure can be removed by etching by irradiating the sensor element with predetermined light in the reaction gas, a large number of sensor elements can be manufactured at one time.

A method of manufacturing a semiconductor device according to claim 4 is
The semiconductor substrate is made amorphous beforehand, and only the surface of the part that forms the support structure is locally annealed using light energy or electron beam to recrystallize, and electrons are generated only on the surface of the support structure by light irradiation. Then, an etching reaction with the reaction gas is carried out, and only the portion of the support structure is selectively removed by etching. In this case, it is necessary to irradiate only the support structure portion with light energy or an electron beam, but since the step of irradiating light and performing local annealing can be performed in a wafer state, as in the conventional case,
This can be easily performed as compared with the method of positioning individual sensor elements and irradiating the support structure with a laser. Further, since only the support structure can be removed by etching by irradiating the sensor element with predetermined light in the reaction gas, a large number of sensor elements can be manufactured at one time.

As described above, according to the method of manufacturing a semiconductor device of the present invention, at least the surface of the portion other than the support structure is provided with etching resistance, and predetermined light irradiation is performed in a predetermined reaction gas to perform the support structure. It is characterized in that only this is collectively removed by etching.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the method for manufacturing a semiconductor device of the present invention will be described with reference to FIG. In the process diagram of FIG.
For simplification, one of the sensor elements arranged in large numbers on the wafer (silicon substrate 1) is shown. Also,
The same components as those of the conventional configuration will be designated by the same reference numerals.

The manufacturing method will be described below. First, Fig. 1
As shown in (a), a silicon substrate 1 having an n-type conductivity and a (100) crystal plane is prepared, and an oxide film is formed on the surface of the silicon substrate 1 in the void portion 4 which becomes a void when the cantilever 2 is completed. (Not shown) is formed by a photolithography technique. Then, using this oxide film as a mask, phosphorus, which is a p-type impurity, is diffused into regions other than the voids 4 to form a p-type layer 5 of about 1 μm from the surface.

Next, in order to form the cavity 1a shown in FIG. 3 (c), an oxide film or a nitride film is formed on the back surface of the silicon substrate 1, and the cavity 1a is formed by the photolithography technique. An opening is provided, and the back surface of the silicon substrate 1 is etched by alkali anisotropic etching such as KOH. At this time, the etching is finished while leaving the thickness of the cantilever 2. After that, the silicon substrate 1 is thoroughly washed with pure water or an organic solvent. By using photolithography technology again, a resist is formed so that the portion to be the support structure 3 is opened, and reactive ion etching (Reactive Ion Etching: RI) using CHF ₃ gas and oxygen gas is performed.
By performing E), as shown in (b), a structure in which the cantilever 2 and the surrounding frame portion are connected by the support structure 3 is formed.

In this state, on the surface of the silicon substrate 1, only the portion of the support structure 3 has n type conductivity, and the other portions have p type conductivity. In this state, a dicing process, a package mounting process, and a bonding process are performed. However, in the drawings described below, the configurations of the package, the bonding wire, and the like are omitted. Even after the above steps, the cantilever 2 has the support structure 3
Since it is mechanically reinforced by, it will not be damaged by water pressure for cutting. In addition, the cantilever 2 is not damaged even by a mechanical shock during mounting or bonding.

Next, the silicon substrate 1 which has undergone the above steps is placed in a chamber, and light is irradiated from a direction perpendicular to the silicon (100) surface. The silicon substrate 1 is heated to about 150 ° C. and irradiated with a mercury lamp in NF ₃ gas. Since the p-type layer 5 is formed on the surface of the portion other than the support structure 3, electrons are not generated even when irradiated with light, so that the reaction gas NF
₃ Reaction with gas is not induced, but electrons are generated by light irradiation in the n-type support structure 3, so NF
Etching reaction occurs by reacting with ₃ gas. By this reaction, only the portion of the n-type support structure 3 is removed by etching by light irradiation, and the other portions are left as they are. Therefore, as shown in (c), the support structure 3 is selectively removed. Etching can be removed collectively. As described above, the method for manufacturing a semiconductor device of the present invention does not require alignment at the time of etching removal and an optical system for converging or scanning light, as compared with the conventional method, and the sensor element having the cantilever 2 is unnecessary. It is possible to collectively process a large amount of.

In the embodiment described above, the n-type silicon substrate 1 is used, but the p-type silicon substrate 1 is used to diffuse the n-type impurities only in the support structure 3. Then, the cantilever 2 is formed in the same manner as the steps described above by forming the n-type layer, and after the assembly is completed, only the portion of the supporting structure 3 is irradiated with light in a reaction gas to be removed by etching. Is possible.

A different embodiment of the present invention will be described with reference to FIG. 2A and 2B are process diagrams for forming a pressure sensor using an n-type silicon substrate 1 having a crystal plane of (100). FIG. 2A is a perspective view, and FIG. 2B is a cross section of the silicon substrate 1 of FIG. Figure,
(C) is a perspective view showing a state in which the support structure 3 is removed. First, as shown in (a) and (b), the resistance region 6 is formed on the surface of the root portion of the cantilever 2 to be formed. Then, only a portion to be the support structure 3 is masked with a resist pattern formed by a photolithography technique, and He ions are implanted at 1015 / cm ² at 200 keV to form a thin amorphous layer 7 on the surface.

Next, in order to form the cavity 1a below the cantilever, an oxide film or a nitride film is formed on the back surface of the silicon substrate 1, and an opening is provided at the location where the cavity 1a is formed by photolithography, and KOH Etching of the back surface of the silicon substrate 1 is performed by alkali anisotropic etching such as. At this time, the etching is finished while leaving the thickness of the cantilever 2. After that, the silicon substrate 1 is thoroughly washed with pure water or an organic solvent. Again, the photolithography technique and the reactive etching are performed so that only the portion to be the support structure 3 remains. As a result, a structure is formed in which only the portion of the support structure 3 has the n-type conductivity and the surface of the other portions is made amorphous.

Next, the sensor element formed on the silicon substrate 1 is separated by dicing. Since the cantilever 2 is mechanically reinforced by the support structure 3, it is damaged by water pressure for cutting or the like. It will not be damaged by mechanical shock during mounting or bonding.

The silicon substrate 1 is attached to a lead frame, a header or the like, and placed in a chamber that can irradiate light from a direction perpendicular to the silicon (100) surface.
The silicon substrate 1 is heated to about 150 ° C and irradiated with a mercury lamp in NF ₃ gas. Electrons are not generated on the surface of the portion other than the support structure 3 regardless of the conductivity type because the surface is made amorphous. Therefore, the etching reaction with NF ₃ gas is not induced, but electrons are generated by the light irradiation in the part of the support structure 3 which is n-type,
An etching reaction occurs by reacting with NF ₃ gas. By the above reaction, only the n-type support structure 3 is removed by etching by light irradiation, and the other parts are left.

Further, a different embodiment of the present invention will be described. First, after forming the resistance layer 6 shown in FIG. 2, ions are implanted into the entire silicon substrate 1 to make the surface amorphous. Then, only the surface of the portion to be the support structure 3 is locally crystallized by using light energy of a laser or the like or an electron beam to recrystallize. After that, after assembling the sensor element in the same manner as the process shown in FIG. 2 and performing light irradiation in the reaction gas, only the support structure 3 is removed by etching. This is a part where electrons are generated by light irradiation in the recrystallized part and an etching reaction is induced, but the surface is not recrystallized (amorphized part).
This is because the etching reaction is not induced in.

In addition, through the embodiment shown in FIG. 1 and FIG.
For example, as reaction gas NF₃Showed that this gas
The SF is not limited to₆, Cl₂, CF_Fouretc
Can be used. It also induces an etching reaction.
Although the mercury lamp is shown as the light source to
Used by KrF excimer laser, ArF excimer laser, etc.
It is possible. Also, the support structure 3 is removed on the silicon substrate.
Wiring that is not resistant to etching is formed.
Even on the surface of the wiring, etc.₂, Si₃N _FourEtc.
Perform a similar process by adding a protective film.
You can

Further, in the embodiment shown in FIG. 2, He is given as an example of ions to be implanted to make the surface of the silicon substrate amorphous, but not only inert atoms such as Ar but also ions are implanted. Other ions can be used as long as they are not activated as carriers, and even if light ions are used, they can be used if the implantation amount and the energy for ion implantation are taken into consideration.

[0029]

As described above, according to the method of manufacturing a semiconductor device according to the first to fourth aspects, the supporting structure for mechanically reinforcing the cantilever in the manufacturing process can be easily collectively formed in the semiconductor process. Since it can be removed, the process time can be shortened and the semiconductor device having the cantilever can be manufactured at low cost.

Further, when the method for manufacturing a semiconductor device according to claim 3 or 4 is used, by amorphizing the surface, the portion can be made resistant to etching for removing the support structure. Therefore, a portion of which the surface is made amorphous may include an n-type conductivity type region.

[Brief description of drawings]

FIG. 1 is a process drawing showing an embodiment of a method for manufacturing a semiconductor device according to the present invention.

FIG. 2 is a process drawing showing a different embodiment of the method for manufacturing a semiconductor device according to the present invention.

FIG. 3 is a process chart showing an example of a conventional method for manufacturing a semiconductor device.

[Explanation of symbols]

 1 Silicon substrate (semiconductor substrate) 2 Cantilever 3 Support structure

Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI Technical display location H01L 21/302 29/84 A 8932-4M H01L 21/302 Z

Claims (4)

[Claims] 1. A method of manufacturing a semiconductor device having a cantilever, comprising a step of providing a support structure for mechanically reinforcing the cantilever only in the manufacturing step, and removing the support structure when no longer needed. In the method of manufacturing a semiconductor device, an n-type semiconductor substrate is used, and a step of diffusing p-type impurities in at least a surface portion of the semiconductor substrate except the support structure formation position, and irradiating a predetermined light in a predetermined reaction gas And removing the supporting structure by etching. 2. A method of manufacturing a semiconductor device having a cantilever, comprising a step of providing a support structure for mechanically reinforcing the cantilever only in the manufacturing step, and removing the support structure when no longer needed. A method of manufacturing a semiconductor device, wherein a p-type semiconductor substrate is used, and an n-type impurity is diffused into a portion of the semiconductor substrate that becomes the support structure;
A step of irradiating a predetermined light in a predetermined reaction gas to remove the support structure by etching, and a method for manufacturing a semiconductor device. 3. A method of manufacturing a semiconductor device having a cantilever, comprising a step of providing a support structure for mechanically reinforcing the cantilever only in the manufacturing step, and removing the support structure when no longer needed. In a method of manufacturing a semiconductor device, a conductivity type of a portion forming the support structure is n-type, and a surface portion of the semiconductor substrate other than the portion forming the support structure is made amorphous, and in a predetermined reaction gas. A step of irradiating a predetermined light to remove the support structure by etching, and a method of manufacturing a semiconductor device. 4. A method of manufacturing a semiconductor device having a cantilever, comprising a step of providing a support structure for mechanically reinforcing the cantilever only in the manufacturing step, and removing the support structure when no longer needed. In a method of manufacturing a semiconductor device, a step of making a conductivity type of a portion forming the support structure n-type and amorphizing a surface of the semiconductor substrate, and locally annealing only a surface portion of the semiconductor substrate forming the support structure. And a step of irradiating a predetermined light in a predetermined reaction gas to remove the support structure by etching, the method for manufacturing a semiconductor device.