JP3570183B2 - Method for manufacturing semiconductor device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a semiconductor device in which an insulating plate is bonded to both surfaces of a silicon substrate, and more particularly to a method of manufacturing a semiconductor device in which a metal thin-film electrode is formed through a through hole provided in an insulating plate.
[0002]
[Prior art]
A semiconductor acceleration sensor as a semiconductor device has a structure in which an electromechanical acceleration sensing unit (hereinafter, referred to as an acceleration sensing unit) is formed in a silicon substrate, and the silicon substrate is sandwiched between relatively thick glass substrates. A through hole is formed in one of the glass substrates, and a metal thin film electrode is formed on the silicon substrate in the through hole for electrical connection to the outside.
[0003]
FIG. 2 is an explanatory view of a manufacturing process of an acceleration sensing unit in a conventional semiconductor acceleration sensor. 2A, a glass substrate 2 is bonded to a silicon substrate 1, and in FIG. 2B, portions 5a and 5c of the oxide film 5 of the silicon substrate 1 which require electrode formation and portions 5b and 5c which require etching are opened by photolithography. After that, a photoresist 6 is applied to the entire surface of the oxide film 5 including this opening, and selectively masked with a glass mask 7 to expose only the opening 5a for forming an electrode and the photoresist 6 on the peripheral edge thereof. .
[0004]
Next, in FIG. 2C, the exposed portion, that is, the opening 5a of the oxide film 5 and the photoresist 6 on the periphery thereof are removed by development, and in FIG. 2D, the opening 5a of the oxide film 5 from which the photoresist 6 is removed and the opening 5a. The entire surface of the photoresist 6 including the peripheral portion is covered with the metal thin film 4. As the metal thin film 4, a chromium / gold (hereinafter, referred to as Cr / Au) multilayer thin film that resists a heated potassium hydroxide solution (hereinafter, referred to as a KOH solution) as an etching agent is used.
[0005]
Next, in FIG. 2E, the photoresist 6 is removed using a resist removing solution. At this time, the metal thin film 4 coated on the photoresist 6 is also removed. As a result, in the opening 5a of the oxide film 5, only the metal thin film adhered to the silicon substrate 1 remains as the metal thin film electrode 4a. As described above, the metal thin film electrode 4a of Cr / Au is formed by the lift-off method using the photomechanical method.
[0006]
Next, in FIG. 2F, a gap 1g and a gap 1h are formed by silicon etching, an acceleration sensing unit including the fixed electrode unit 1a to the outer frame 1c is formed, and in FIG. 2G, the oxide film 5 on the silicon substrate 1 is removed. Then, the glass substrate 3 on which the through holes 3a and the counterbores 3b are formed in advance on the surface of the silicon substrate 1 is aligned and joined so that the through holes 3a coincide with the electrodes 4a. Is completed by sandwiching both surfaces of the substrate between the glass substrates 2 and 3 in a sandwich shape.
[0007]
The above-described method of manufacturing an acceleration sensing unit in a semiconductor acceleration sensor as a conventional semiconductor device uses a photoengraving method in an exposure process of a photoresist 6 in a process of manufacturing a metal thin film electrode 4a. An aligner (not shown) is required, which increases manufacturing equipment costs. In addition, it is necessary to perform a positioning operation for opening a portion 5a of the oxide film 5 of the silicon substrate 1 that requires electrode formation and a portion 5b and 5c that requires etching by photolithography, but this operation is extremely complicated. .
[0008]
In addition, it is necessary to align the silicon substrate 1 on which the metal thin-film electrode 4a has been formed with the glass substrate 3 having the through-hole 3a formed thereon, and work so as not to damage the metal thin-film electrode 4a. There is a need to. Further, since the metal thin-film electrode 4a is formed before silicon etching with a KOH solution, it is necessary to use an expensive metal such as Cr / Au having excellent corrosion resistance.
[0009]
[Problems to be solved by the invention]
The conventional method of manufacturing a semiconductor device includes the above manufacturing steps. In the step of exposing the photoresist 6 in the step of manufacturing the metal thin-film electrode 4a, a photolithography method is used, so that an expensive glass mask or precision mask aligner is required. In addition, there has been a problem that the alignment work for photoengraving is complicated, and it is difficult to reduce the manufacturing cost.
[0010]
The present invention has been made to solve the above problems, and when forming a metal thin film electrode in a through hole provided in an insulating plate, by forming without using a photoengraving method, It is an object of the present invention to provide a method for manufacturing a semiconductor device capable of reducing the manufacturing cost.
[0011]
[Means for Solving the Problems]
A method of manufacturing a semiconductor device according to a first aspect of the present invention includes a step of joining a silicon substrate and an insulating plate having a predetermined thickness and a through hole formed in advance corresponding to a portion on the silicon substrate where an electrode is to be formed. And forming a metal thin film on at least the surface of the insulating plate and a portion where the electrode is formed in the through-hole, applying a resist on the surface of the metal thin film, and placing the resist in the through-hole such that the surface is substantially flat. Thick coating, so as to expose the metal thin film except inside the through-hole, soak the resist to such an extent that it remains at the bottom in the through-hole, immersing it in a solution for a predetermined time, Removing the resist remaining in the through hole after removing the metal thin film that has been provided, and forming a metal thin film electrode on the silicon substrate in the through hole. It is a method of forming.
[0012]
A method of manufacturing a semiconductor device according to a second aspect of the present invention is the method of manufacturing a semiconductor device according to the first aspect, wherein the step of pre-baking the applied resist is performed after the step of applying a resist on the surface of the metal thin film. And forming a metal thin film electrode on a silicon substrate in a through hole.
[0013]
A method for manufacturing a semiconductor device according to a third aspect of the present invention is a method for manufacturing a semiconductor device according to the first or second aspect, wherein at least a step of preparing an insulating plate having a thickness of 3 μm or more is provided. .
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
Embodiment 1 FIG.
Embodiment 1 of the present invention will be described with reference to FIG. FIG. 1 is a diagram illustrating a manufacturing process of a semiconductor acceleration sensor as a semiconductor device according to the first embodiment. In the figure, those denoted by the same reference numerals as those of the conventional example indicate the same or equivalent parts as those of the conventional example.
[0015]
In FIG. 1A, a gap 1f having a depth of about 100 μm is formed by silicon etching on one side of a wafer-shaped silicon substrate 1 having a thickness of about 200 μm, both sides of which are mirror-polished, and a thickness as an insulating plate is formed on this side. The glass substrate 2 having a thickness of about 400 μm is anodically bonded. Anodic bonding is known as a technique for directly bonding a silicon wafer and a glass substrate by applying a high voltage of about 1000 V to a silicon wafer under a high temperature environment of several hundred degrees.
[0016]
Next, in FIG. 1B, a gap 1 g and a gap 1 h are formed on the silicon substrate 1 as an integral body of the silicon substrate 1 and the glass substrate 2 by silicon anisotropic etching, so that the fixed electrode portion 1 a to the outer frame 1 c are removed. Forming an acceleration sensing unit.
[0017]
Next, in order to protect the acceleration sensing part, a glass substrate 3 having a thickness of about 400 μm as an insulating plate on which a through hole 3a and a counterbore 3b are previously formed is anodically bonded to the surface of the silicon substrate 1. As a result, a structure is obtained in which both sides of the silicon substrate 1 are sandwiched between glass substrates 2 and 3 as insulating plates. The glass substrates 2 and 3 are made of a heat-resistant glass material having a thermal expansion coefficient substantially equal to that of the silicon substrate 1.
[0018]
Next, in FIG. 1C, the entire surface of the glass substrate 3 including the through hole 3a is coated with the metal thin film 4. As the metal thin film electrode material, an aluminum thin film having a thickness of several μm or an alloy thin film containing aluminum as a main component, which is widely used as a wiring material for silicon semiconductors, is used for resistance heating evaporation, electron beam evaporation, sputter evaporation. And the like.
[0019]
Next, in order to separate the electrodes in the individual through holes 3a electrically short-circuited by the metal thin film 4, a photoresist 6 is spin-coated on the metal thin film 4 covering the entire surface of the glass including the through holes 3a. I do. Since the depth of the through hole 3a of the glass substrate 3 is about 400 μm, which is the same as the thickness of the glass substrate 3, the photoresist 6 is applied thicker in the through hole 3a than the flat surface of the glass substrate 3. Next, the applied photoresist 6 is pre-baked to be semi-solidified.
[0020]
Next, in FIG. 1D, the photoresist 6 which has been semi-solidified by being immersed in a developing solution as a solvent for a predetermined time and developed is dissolved, and at this time, the photoresist 6 in the flat portion of the glass substrate 3 is completely dissolved. However, the thickly applied resist in the through hole 3a is dissolved to such an extent that the resist remains without being completely dissolved. In this state, the photoresist 6a remaining in the through hole 3a is post-baked and completely solidified.
[0021]
In the first embodiment, the step of exposing the photoresist 6 after the pre-baking is unnecessary. That is, since the thickness of the photoresist 6 in the flat portion is about several μm, which is extremely thin as compared with the thickness of the resist in the through-hole 3a, even if the exposure step for the photoresist 6 is omitted, after semi-solidification by pre-baking, development When the photoresist 6 applied on the plane of the metal thin film 4 is completely removed by immersion in the liquid for a predetermined time, the photoresist 6 having a necessary and sufficient thickness can be left in the through hole 3a.
[0022]
Next, in FIG. 1E, the metal thin film 4 is selectively etched to leave the metal thin film 4 only in the through-hole 3a protected by the photoresist 6a. In FIG. 1F, the photoresist 6a is removed with a removing solution. The formation of the metal thin film electrode 4a is completed by increasing the adhesion between the silicon surface and the metal thin film.
[0023]
As described above, in the first embodiment, the through hole 3a of the glass substrate 3 has a depth of about 400 μm, and the photoresist 6 is applied thicker in the through hole 3a than the flat surface of the glass substrate 3. The exposure step of the photoresist 6 after the pre-baking was omitted. That is, after the photoresist 6 is spin-coated on the metal thin film 4 and pre-baked to be semi-solidified, the photoresist 6 in the flat portion of the glass substrate 3 is dissolved, but remains in the thickly coated through hole 3a without being completely dissolved. The photoresist 6a that had been dissolved to a certain extent and remained in the through hole 3a was post-baked.
[0024]
As described above, the step of exposing the photoresist 6 after pre-baking is not required, so that photolithography using a glass mask is not required, and it is not necessary to consider non-uniformity of resist coating, and it is not necessary to perform self-alignment. Since no mask is required, there is no need for operations such as mask positioning, and there is no worry about mask displacement. That is, compared with the conventional example, an expensive precision mask aligner and a glass mask are not required, and the photoresist 6 is removed by immersing in a developing solution as a solution for a predetermined time. This eliminates the need for simple equipment, saves labor in the manufacturing process, reduces equipment costs, and makes it possible to manufacture a semiconductor acceleration sensor as a semiconductor device at lower cost.
[0025]
In the first embodiment, the photoresist 6 is used as a resist applied on the surface of the metal thin film 4. However, since the exposure step is omitted, a photosensitive resist such as a negative photoresist or a positive photoresist is not necessarily required. Inexpensive resist can be used. Therefore, a developing solution is not necessarily required for removing the resist, and a less expensive resist solvent can be used.
[0026]
In the first embodiment, a step of pre-baking the photoresist 6 is provided before the step of dipping the resist 6 applied on the surface of the metal thin film 4 in a developing solution for a predetermined time. It is possible to omit the pre-bake by selecting the resist material. However, the pre-bake makes the resist semi-solidified immediately after the application, and makes it extremely easy and reliable to perform subsequent handling work, control of the immersion time in the solution, and the like.
[0027]
In the first embodiment, after the glass substrate 3 is anodically bonded to the silicon substrate 1 on which the acceleration sensing unit is formed, the surface of the glass substrate 3 including the through holes 3a is coated with the metal thin film 4. Since there is no silicon etching step in the post-process, an expensive electrode material such as Cr / Au shown in the conventional example is not required as the metal thin film 4 serving as an electrode, and is widely used as a wiring material for silicon semiconductors. A thin aluminum film having a thickness of several μm or an alloy thin film containing aluminum as a main component can be coated by a method such as resistance heating evaporation, electron beam evaporation, or sputter evaporation. Since the silicon substrate 1 and the glass substrate 3 were anodic-bonded before forming the silicon substrate 1, the positioning operation of the silicon substrate 1 and the glass substrate 3 was performed. Are free, the manufacturing cost can be reduced significantly.
[0028]
In the first embodiment, the glass substrates 2 and 3 each having a thickness of about 400 μm are used as the insulating plate. However, a glass thickness of about 400 μm is not necessarily required. That is, for the purpose of simply omitting photolithography (exposure) for removing the resist applied on the surface of the metal thin film 4, a thickness of 3 μm or more is sufficient.
[0029]
Further, in the first embodiment, the heat-resistant glass substrates 2 and 3 having a thermal expansion coefficient substantially equal to that of the silicon substrate 1 are used as the insulating plate. However, the insulating plate is not limited to the heat-resistant glass material. An inorganic or organic insulating material that mechanically protects and electrically insulates the acceleration sensing unit formed on the substrate 1 may be used. For the glass substrate 2, the bonding surface with the silicon substrate 1 is insulated. Metal plate may be used.
[0030]
In the first embodiment, the method for manufacturing the acceleration sensing unit in the semiconductor acceleration sensor has been described as an example. However, the present invention is not limited to the method for manufacturing the acceleration sensing unit in the semiconductor acceleration sensor. An insulating plate having a predetermined thickness and a through-hole formed in advance is bonded thereto, and is applied to a general method of manufacturing a semiconductor device of a type in which an electrode for connection between the silicon substrate and the outside is formed in the through-hole. it can.
[0031]
【The invention's effect】
According to the first invention, in the step of forming the metal thin film electrode in the through hole on the surface of the insulating plate, the resist applied on the surface of the metal thin film formed on the surface of the insulating plate including the through hole is formed. The exposure step was omitted, and the resist was removed except for the bottom in the through-hole by immersing in the solution for a predetermined time, so that a glass mask or the like was unnecessary, and operations such as mask positioning were also performed. There is an effect that a manufacturing method of a semiconductor device which is unnecessary, does not require a photosensitive resist, simplifies the manufacturing process, and can reduce capital investment and material cost can be obtained.
[0032]
According to the second aspect of the invention, a step of pre-baking the applied resist is added after the step of applying the resist on the surface of the metal thin film in the first aspect, so that the applied resist is semi-solidified. However, an effect that the handling operation, management of the immersion time in the solution, and the like are extremely easy and reliable can be obtained.
[0033]
According to a third aspect, in the method of manufacturing a semiconductor device according to the first or second aspect, the through-hole is formed, and the thickness of the insulating plate is set to 3 μm or more. Since the thickness of the resist is increased by an amount corresponding to the thickness of the insulating plate, an effect is obtained that the operation of removing the resist while leaving only the inside of the through hole is easier and more reliable.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a manufacturing process of an electromechanical acceleration sensing unit in a semiconductor acceleration sensor according to a first embodiment of the first to third inventions;
FIG. 2 is a diagram illustrating a manufacturing process of an electromechanical acceleration sensing unit in a conventional semiconductor acceleration sensor.
[Explanation of symbols]
Reference Signs List 1 silicon substrate, 1a fixed electrode part, 1b mass, 1c outer frame, 1f gap, 1g gap, 1h gap, 2, 3 glass substrate, 3a through hole, 3b counterbore, 4 metal thin film, 4a metal thin film electrode, 6 photoresist

Claims (3)

Bonding a silicon substrate and an insulating plate having a predetermined thickness in which a through-hole is formed in advance corresponding to a portion of the silicon substrate on which an electrode is to be formed; and Forming a metal thin film at the site where the electrodes are formed, applying a resist on the surface of the metal thin film, thickly in the through hole so that the surface is substantially flat, and excluding the inside of the through hole A step of immersing the resist in a solution for a predetermined time so as to dissolve the resist to the extent that it remains at the bottom in the through hole so that the metal thin film is exposed, and removing the exposed metal thin film, and then removing the through hole. Removing the resist remaining in the through hole, and forming a metal thin film electrode on the silicon substrate in the through hole. Law. Bonding a silicon substrate and an insulating plate having a predetermined thickness in which a through-hole is formed in advance corresponding to a portion of the silicon substrate on which an electrode is to be formed; and Forming a metal thin film at a portion where an electrode is formed, and applying a resist on the surface of the metal thin film in a through hole so that the surface is substantially flat; and prebaking the applied resist. And soaking the metal thin film except for the inside of the through hole so as to dissolve the resist to the extent that it remains at the bottom in the through hole, and immersing the resist in the solution for a predetermined time. Removing the resist remaining in the through-hole after removing the metal thin film; and forming a metal thin film on the silicon substrate in the through-hole. The method of manufacturing a semiconductor device, which comprises forming a pole. 3. The method for manufacturing a semiconductor device according to claim 1, further comprising a step of preparing an insulating plate having a thickness of 3 μm or more.

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