JP2016039177A - Lift-off mask, semiconductor device manufactured by using the same, and mems element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lift-off mask capable of reducing processing time for a lift-off processing step and removing residual, while keeping mask removal ability of chemical, a semiconductor device using the same and a MEMS element.SOLUTION: The lift-off mask comprises an opening 1a for forming a desired thin film pattern; and at least one of openings 1b, 1c for chemical inflow and for not forming the desired thin film pattern.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a lift-off mask, and a semiconductor device and a MEMS device manufactured using the lift-off mask.

  Conventionally, a lift-off mask is used for a semiconductor element, a MEMS (Micro Electro Mechanical Systems) element, and the like in a manufacturing process for forming a thin film pattern on a substrate. Such a lift-off mask is formed with an opening corresponding to a target thin film pattern. After the formation of the target thin film pattern and the thin film, it is removed together with the thin film formed on the lift-off mask by a chemical solution (hereinafter also referred to as an etching solution) that selectively removes the lift-off mask (hereinafter referred to as a lift-off process). Also called a process).

  FIG. 4 is a schematic plan view showing an example of a substrate 200 on which a lift-off mask 100 is placed for explaining a conventional lift-off process. The lift-off mask 100 includes an opening 100a corresponding to a position where a target thin film having a target thin film pattern necessary for the function of the semiconductor element or the MEMS element is formed, and a plurality of electrodes provided on the surface of the substrate 200 and the peripheral edge thereof. It is placed on the substrate 200 so as to cover the pad 300.

  FIG. 5 is a schematic diagram for explaining a cross section taken along the line BB of the laminate in which the layer 400 constituting the target thin film is further formed on the lift-off mask of FIG. A target thin film 401 is formed on the substrate 200 through the opening 100a, and a thin film 402 to be removed is formed on the lift-off mask 100. Further, the target thin film 401 and the substrate 200 on which the target thin film 401 is formed form a stepped portion. When a chemical solution for removing only the lift-off mask 100 is introduced from the opening, the chemical solution is directed in the direction of the arrow in the drawing, that is, from the center of the substrate toward the end. Thereby, the lift-off mask 100 and the thin film 402 are removed. After the lift-off process, a residue 100r due to the chemical solution or the composition of the lift-off mask 100 may be generated on the substrate 200 and the electrode pad 300 from the side surface to the vicinity of the stepped portion.

  In the method according to the prior art, there are problems that the time of the lift-off treatment process becomes long and the removal ability for the lift-off mask is lowered due to deterioration of the chemical solution. Further, as a result of the residue remaining on the side surface or the vicinity of the target thin film and the electrode pad, there is a problem that foreign matters adhere to the substrate being manufactured due to the presence of the residue.

  In light of the above-described problems, the present invention provides a lift-off mask that reduces the time of the lift-off treatment process while maintaining the ability to remove the chemical mask, and a semiconductor device manufactured using the lift-off mask, which is less likely to generate residues. An object is to provide a MEMS device.

  The present invention has been made to solve the above problems. That is, the present invention is a lift-off mask according to one embodiment. The lift-off mask according to the present invention includes an opening for forming a target thin film pattern and at least one opening for inflow of a chemical solution that does not form the target thin film pattern.

  In the lift-off mask, at least one opening for inflowing the chemical solution is separated from an opening for forming the target thin film pattern, and an outer peripheral edge of the opening for forming the target thin film pattern is formed. It is preferable to be provided surrounding.

  The lift-off mask is a lift-off mask formed so as to cover a substrate constituting a unit element and a plurality of electrode pads provided on the substrate, and the electrode pad is positioned in the vicinity of an end portion of the substrate. An opening for forming the target thin film pattern is disposed at a central portion between the opening for forming the target thin film pattern and a lift-off mask region covering the electrode pad. Preferably, at least one opening for inflowing the chemical solution is disposed.

  In the lift-off mask, it is preferable that at least one opening for inflow of the chemical solution is further disposed between a lift-off mask region covering the electrode pad and a lift-off mask region covering the substrate end. .

  The present invention, according to yet another embodiment, is a method for manufacturing a semiconductor device or a MEMS device. A method of manufacturing a semiconductor element or a MEMS element according to the present invention includes forming a film on a substrate or a predetermined layer constituting a unit element, patterning the film, and forming any one of the lift-off masks described above. A step of forming a thin film on the lift-off mask; and a lift-off treatment step of flowing a chemical into the lift-off mask.

  According to another embodiment, the present invention is a semiconductor device or a MEMS device manufactured using the lift-off mask.

  ADVANTAGE OF THE INVENTION According to this invention, the time of a lift-off process process can be shortened, maintaining the removal capability of a chemical | medical solution mask. In particular, in the case of a metal mask, the possibility of etching-derived residue that tends to occur on the electrode pad is reduced. In the case of a resist mask, the possibility that the resist material remains in the vicinity from the side surface of the stepped portion on the substrate is reduced. In particular, the present invention provides a lift-off mask useful when the area of the target thin film is small with respect to the surface area of the substrate and the portion removed by the lift-off process is large, and a semiconductor device and a MEMS device manufactured using the lift-off mask.

FIG. 1 is a schematic plan view showing an element substrate on which a lift-off mask according to a first embodiment of the present invention is formed. 2 is a cross-sectional view taken along line AA in FIG. FIG. 3 is a schematic cross-sectional view showing a lift-off process step in a state in which a lift-off mask is formed in the semiconductor device and MEMS device manufacturing method using the lift-off mask according to the first embodiment of the present invention. FIG. 4 is a schematic plan view showing an example of conventional lift-off mask formation. FIG. 5 is a schematic diagram for explaining an example of a lift-off process in the cross section taken along the line BB of the laminate in which the target thin film is formed on the lift-off mask of FIG.

  Embodiments of the present invention will be described below with reference to the drawings. In addition, this invention is not limited by embodiment described below.

[Lift-off mask]
The present invention is a lift-off mask according to one embodiment. The following description describes an embodiment in which a lift-off mask is provided on a substrate with electrode pads without any other layers. The lift-off mask of this embodiment includes at least an opening for forming a target thin film pattern, and at least one opening for inflow of a chemical solution and not forming a target thin film pattern.

  FIG. 1 is a schematic plan view of a lift-off mask 1 placed on a substrate 2 constituting a unit element, and FIG. 2 is a cross-sectional view taken along line AA of FIG. In FIG. 1, the substrate 2 has a substantially square shape, and includes four substantially square electrode pads 3 which are embedded in the vicinity of the four corners of the lift-off mask forming surface. Referring to FIG. 2, the lift-off mask formation surface of the substrate 2 and the lift-off mask formation surface of the electrode pad 3 are on the same plane. The “lift-off mask forming surface” refers to the surface of the substrate 2 or the electrode pad 3 that is covered with the lift-off mask 1. The lift-off mask according to the present embodiment can be provided on a larger substrate composed of the substrate 2 constituting a plurality of unit elements. However, for convenience of explanation, the lift-off mask on the substrate 2 constituting the unit element is shown in FIG. 1 is illustrated.

  The lift-off mask 1 is a mask made of a metal material or resist material that is soluble in a chemical solution used in the lift-off process, has a predetermined thickness, and has a substantially rectangular shape that covers at least the outer shape of the substrate 2. Consists of. In FIG. 1, the lift-off mask 1 is formed so as to cover the surface of a substrate 2 and a plurality of electrode pads 3 provided in the vicinity of an end portion on the substrate 2. The lift-off mask 1 includes a first opening 1a, a second opening 1b, and optionally a third opening 1c. The openings 1a to 1c shown in FIG. 2 penetrate the lift-off mask 1, and thereby the surface of the substrate 2 is exposed.

  Hereinafter, each opening will be described. The position where each opening is formed is preferably determined by the relationship between the substrate 2 having the surface covered with the lift-off mask, the electrode pad 3, and other members (not shown).

  The first opening 1a has a substantially rectangular opening region, and is provided at a substantially central portion of the lift-off mask 1 in order to form a target thin film pattern. Further, the first opening 1 a is in a position where it does not contact the electrode pad 3. The term “when the opening does not contact the specific member in the lower layer” means that the thin film formed by the opening does not contact the specific member in the lower layer without the opening being positioned on the specific member. . The shape and dimensions of the first opening 1a can be determined so as to match the shape of the target thin film, and are not limited to a specific shape. In this specification, the target thin film pattern refers to the shape of a thin film formed on the substrate 2 by the lift-off mask 1 and having a specific electric action as a part of a unit element such as a semiconductor element or a MEMS element.

  The second opening 1b has a mouth shape having a predetermined width, and the second opening 1b is mainly provided in the lift-off mask 1 for inflow of a chemical solution. As a result, it is possible to form a thin film pattern that is not necessary for the original purpose, that is, does not bear a specific electrical action as a part of a unit element such as a semiconductor element or a MEMS element. The 2nd opening part 1b is spaced apart from the 1st opening part 1a, and is provided surrounding the outer periphery. In FIG. 2, the second opening 1 b is a region covering the first opening 1 a and the electrode pad 3 when the lift-off mask 1 in a state of covering the substrate 2 and the plurality of electrode pads 3 is viewed in plan view. The second opening 1b is not provided on the electrode pad 3. Further, the second opening 1b is provided at a position where the function of a unit element such as a semiconductor element or a MEMS element is not hindered, for example, an external or internal supply voltage and / or a lead wire for transmitting / receiving a signal and the electrode pad 3 It is provided at a position that does not exist in the position.

  The shape and dimensions of the opening can be appropriately determined so as to satisfy the positional relationship with these lower layers. The illustrated second opening 1b is in communication and has a straight line shape, but the second opening 1b has an O-shape, I-shape, L-shape, U-shape, or The shape may be a combination thereof, or may be a plurality of openings that are not in communication.

  The third opening 1c has a mouth shape having a predetermined width, and can be optionally provided in the lift-off mask 1 for inflow of a chemical solution. Similarly, the third opening 1c can form a thin film pattern unnecessary for the original purpose. The third opening 1c is provided so as to be separated from and surround the outer peripheral edge of the second opening 1b. Further, in FIG. 1, the third opening 1 c includes a region of the lift-off mask 1 that covers the electrode pad 3 when the lift-off mask 1 that covers the substrate 2 and the plurality of electrode pads 3 is viewed in plan view. It is provided between the region of the lift-off mask 1 covering the end of the substrate 2. Furthermore, the 3rd opening part 1c is also provided in the position which does not inhibit the function of unit elements, such as a semiconductor element or a MEMS element. The shape and size of the third opening 1c are not limited to the specific shape shown in the figure, and can be determined in the same manner as the second opening 1b. The shape of the third opening 1c is preferably similar to the shape of the second opening 1b. The “region of the lift-off mask that covers the end portion of the substrate” refers to a region of the lift-off mask 1 that covers the end portion of the substrate and the vicinity thereof.

  Note that the number of openings is not limited to the number shown in the figure, and the chemical solution inflows into the region where the second opening or the third opening is formed within a range that does not hinder the function of a unit element such as a semiconductor element or a MEMS element. For this purpose, fourth and fifth openings may be formed.

  The material and manufacturing method of the lift-off mask having such a structural feature will be described in detail in the method of manufacturing a semiconductor element and a MEMS element using the lift-off mask.

[Method of manufacturing semiconductor device and MEMS device using lift-off mask]
A method for manufacturing a semiconductor element and a MEMS element using the lift-off mask according to the present invention having the above-described configuration will be described. A method of manufacturing a semiconductor device and a MEMS device according to one embodiment of the present invention includes a step of forming a film on a substrate or a predetermined layer constituting a unit element, patterning the film, and forming a lift-off mask, The method includes at least a step of forming a thin film on a lift-off mask and a lift-off process step of flowing a chemical into the thin film.

  The lift-off mask forming step is a step of forming the lift-off mask 1 having the above-described configuration by forming and patterning on the substrate 2 or a desired layer. In the above-described configuration, the form in which the lift-off mask 1 is provided on the substrate 2 has been described. However, the lift-off mask 1 may be formed on the uppermost layer of the stacked structure sandwiching the interlayer insulating film. When the lift-off mask is a metal mask, a metal film is formed on the substrate 2 by a normal film formation method such as vapor deposition. Alternatively, when the lift-off mask is a resist mask, a resist film is formed on the substrate 2 by a film forming method such as photolithography. Subsequently, a lift-off mask having a predetermined opening is formed by patterning the metal film or the resist film. When the lift-off mask is a metal mask, the metal film is patterned by a normal processing method such as a laser method. Alternatively, when the lift-off mask is a resist mask, the resist film is patterned by an exposure method such as photolithography and a development method.

The lift-off mask 1 may be made of a material used for a normal lift-off mask, for example, a metal material or a resist material. Examples of the material of the metal film include a metal material such as aluminum (Al), copper (Cu), nickel (Ni), chromium (Cr), or a laminate including one or more of these, but a specific material. It is not limited to. In addition, examples of the resist material include resist materials such as silicon dioxide (SiO ₂ ) and nitride film (Si ₃ N ₄ / SiN) or a laminate including one or more of these materials, but specific materials include It is not limited.

  The subsequent thin film forming step is a step of forming the thin film 4 including the target thin film on the substrate 2 and the lift mask 1 from above the lift-off mask 1 by the conventional film forming method. Examples of the film forming method for forming the thin film include a coating method such as a PVD method.

  The thin film 4 is made of a metal element such as platinum (Pt), gold (Au), copper (Cu), tantalum (Ta), titanium (Ti) and the like, a metal oxide thereof, a composite oxide thereof, a laminate thereof, or a laminate thereof. However, the present invention is not limited to these.

  FIG. 3 is a schematic cross-sectional view for explaining a thin film forming process and a lift-off process in the method for manufacturing a semiconductor element and a MEMS element in a state where the lift-off mask 1 according to the present invention is formed. A thin film 41 having a target thin film pattern corresponding to the shape of the first opening 1a is formed on the substrate 2 by the thin film forming step. The target thin film 41 functions as part of a unit element such as a semiconductor element or a MEMS element.

  A thin film 42 is formed on the lift-off mask 1 between the first opening 1a and the second opening 1b, and a thin film 43 is formed on the lift-off mask 1 between the second opening 1b and the third opening 1c. The thin film 44 is formed on the lift-off mask 1 between the third opening 1c and the end of the substrate 2. These thin films are removed together with the lift-off mask 1 by a lift-off process.

  Further, a thin film 45 having a thin film pattern corresponding to the shape of the second opening 1 b is formed on the substrate 2 through the second opening 1 b of the lift-off mask 1. Further, optionally, when the third opening 1c exists, a thin film 46 having a thin film pattern corresponding to the shape of the third opening 1c is formed. The thin film 45 and the thin film 46 are not electrically associated with a unit element such as a semiconductor element or a MEMS element, and are in positions that do not hinder the function of the semiconductor element. After these thin films 4 are formed, due to the first opening 1a, the second opening 1b and the third opening 1c of the lift-off mask 1, the thin film 4 also has the openings 4a, 4b and openings. Part 4c is formed.

  In the subsequent lift-off treatment process, the chemical solution is applied to the laminate formed by the thin film formation process. Referring to FIG. 3, the chemical solution that has flowed from the openings 4 a to 4 c of the thin film 4 is removed by selectively dissolving only the lift-off mask 1 that is in contact therewith.

A chemical solution for removing the lift-off mask 1 can be appropriately determined by those skilled in the art from the relationship between the material of the lift-off mask and the material of the target thin film. In the case where the lift-off mask 1 is a metal mask, examples of the chemical liquid include phosphonic acetic acid (H ₃ PO ₄ / HNO ₃ / CH ₃ COOH / H ₂ O). When the lift-off mask 1 is a resist mask, a stripping solution made of organic alkali, for example, TMAH (N (CH ₃ ) ₄ OH) or the like can be used. The chemical solution may contain a conventional oxidizing agent or reducing agent for maintaining the etching grade over time.

  Since the lift-off mask 1 of the present invention is provided with a plurality of openings, the chemical solution penetration path is increased, and the contact area between the lift-off mask and the chemical solution is also increased compared to the prior art. For example, the chemical solution flowing in from the opening 4 a forms a flow from the target film 41 toward the thin film 45. The chemical solution flowing in from the opening 4 b forms a flow from the thin film 45 toward the target thin film 41 and a flow from the thin film 45 toward the electrode pad 3. Moreover, the chemical | medical solution which flowed in from the opening part 4c forms the flow which goes to the electrode pad 3 from the thin film 46, and the flow which goes to the edge part of a board | substrate from the thin film 46. FIG. That is, as compared with the prior art in FIG. 5, when the opening 4b and the opening 4c exist, the lift-off mask 1 can be removed from at least two directions. Although not shown, there is a flow of the chemical liquid toward the front side and the rear side of the paper plane in FIG. 3, and all of these flows can be combined to promote the removal of the lift-off mask 1 by the chemical liquid.

  Further, the step portions formed by the target thin film 41 and the substrate 2, the step portions formed by the thin film 45 and the substrate 2, the step portions formed by the thin film 46 and the substrate 2, and the electrode pads 3 have openings 4a to 4c. The chemical that flows in through Thereby, a lift-off process process can be performed without leaving a residue on the side surface of the stepped portion and the vicinity thereof and on the electrode pad 3.

  After the element manufacturing process is completed, the mounting process can be performed by a conventional method such as wire bonding or wireless bonding. This mounting process can be performed by connecting the target thin film 41, an external or internal power supply or circuit, and the electrode pad 3 through a lead wire using a conventional mounting apparatus. Since the residue on the electrode pad 3 is completely removed by the lift-off process, variations in bonding strength in the mounting process can be reduced. Mounting by wireless bonding is preferable because the contact resistance between the power source or the circuit and the electrode pad 3 is stabilized.

  According to another aspect, the present invention is a semiconductor device or a MEMS device manufactured using a lift-off mask. The lift-off mask forming process, the thin film forming process, and the optional bonding process may be included in a method for manufacturing a semiconductor element or a MEMS element, and the present invention also includes a semiconductor element or a MEMS element manufactured by these methods. Is included. In addition to the target thin film, these elements are configured to include a thin film that is not directly related to the functions of these elements and that does not hinder the functions of these elements. Such a semiconductor element or a MEMS element is an element which has little lift-off mask residue or the like on an electrode pad or a substrate and does not contain foreign matters.

  Here, the problem solved by the present invention will be described in more detail. For example, when the lift-off mask is a metal mask, an etching solution (chemical solution) enters, that is, penetrates, while etching (removing) the lift-off mask from a gap in an opening formed on the lift-off mask. At this time, if the chemical solution penetration path becomes long, it takes time for the chemical solution to penetrate, and the oxidizing agent in the etching solution is consumed, resulting in a decrease in removal ability. As a result, the lift-off process takes time, and the etching solution changes, so that a normal etching reaction cannot be performed, and foreign substances such as etching residues are likely to remain on the substrate side. It was. In particular, when there is a metal electrode pad such as a bonding pad on the substrate side, there has been a problem that foreign matter tends to adhere to the substrate as a result of variations in bonding strength and the entire substrate. Also, for example, when the lift-off mask is a resist mask, as in the case of a metal mask, since the chemical solution penetration path is long, the lift-off process takes time, and the chemical solution is formed at the step between the target thin film and the substrate. There is a problem that the wraparound becomes slow and the resist material tends to remain.

  On the other hand, according to the method of the present invention, by using the lift-off mask having the configuration of the above-described embodiment, the immersion path can be shortened and the processing time of the lift-off process can be shortened. In addition, since the chemical solution on the substrate is improved, the fresh chemical solution can always be supplied. Therefore, the etching grade in the lift-off process step is maintained, and the processing time of the lift-off process step can be shortened. Further, when the lift-off mask is a metal mask, the possibility of etching residues can be reduced. Further, when the lift-off mask is a resist mask, it is possible to reduce the possibility that the resist material remains at the step portion after the lift-off process.

  In the above-described embodiment, the substantially rectangular substrate and the electrode pad are exemplified, but the present invention is not limited to this. The shape of the substrate is not limited to a specific shape. Moreover, the board | substrate with which an electrode pad is not provided, or the electrode pad is provided in the form different from the number and shape shown in figure may be sufficient.

  The lift-off mask according to the present invention and the semiconductor element and MEMS element including the lift-off mask can be applied particularly to a semiconductor sensor such as a gas sensor.

DESCRIPTION OF SYMBOLS 1,100 Lift-off mask 1a, 100a 1st opening part 1b 2nd opening part 1c 3rd opening part 2,200 Substrate 3,300 Electrode pad 4, 42, 43, 44, 45, 46, 402 Thin film 4a, 4b, 4c Openings 41, 401 Target thin film 400 layers

Claims (6)

An opening for forming a target thin film pattern;
A lift-off mask comprising at least one opening for inflow of a chemical solution that does not form a target thin film pattern.   The at least one opening for inflow of the chemical solution is provided apart from the opening for forming the target thin film pattern and surrounding the outer periphery of the opening for forming the target thin film pattern. Item 2. A lift-off mask according to Item 1. 3. The lift-off mask according to claim 1, wherein the lift-off mask is formed so as to cover a substrate constituting the unit element and a plurality of electrode pads provided on the substrate. Located in the
An opening for forming the target thin film pattern is disposed at the center,
A lift-off mask in which at least one opening for injecting the chemical solution is disposed between an opening for forming the target thin film pattern and a region of the lift-off mask covering the electrode pad.   4. The lift-off mask according to claim 3, wherein at least one opening for inflowing the chemical solution is further disposed between a region of the lift-off mask that covers the electrode pad and a region of the lift-off mask that covers the edge of the substrate. . Forming a lift-off mask according to any one of claims 1 to 4 by forming a film on a substrate constituting a unit element or a predetermined layer, and patterning the film;
Forming a thin film on the lift-off mask;
A method for manufacturing a semiconductor element or a MEMS element, comprising: a lift-off process step for allowing a chemical solution to flow into the lift-off mask.   The semiconductor element or MEMS element manufactured using the lift-off mask as described in any one of Claims 1-4.

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