Front-sidewall metallization thickness uniformity control method based on alternating shielding and sputtering timing control

Abstract

The present invention discloses a method for controlling the thickness consistency of the front-side wall metallization based on alternating shielding and sputtering timing control, which belongs to the field of integrated circuit manufacturing and comprises the following steps: S1, taking a ceramic substrate; S2, applying adhesive tape on the side wall surface of the ceramic substrate; S3, metallizing the front side of the ceramic substrate; S4, peeling off the adhesive tape on the side wall of the ceramic substrate and applying adhesive tape on the front side of the ceramic substrate; S5, metallizing the side surface of the ceramic substrate; wherein, k Ti =t2 Ti / t1 Ti =R Tiside / R Tifront , k Pt =t2 Pt / t1 Pt =R Ptside / R Ptfront , k Au =t2 Au / t1 Au =R Auside / R Aufront The present invention is used to achieve uniform thickness of Ti, Pt, and Au on the front and side walls.

Description

Technical Field

[0001] The present invention relates to the field of integrated circuit manufacturing, and more particularly to a method for controlling the thickness uniformity of front-side wall metallization based on alternating shielding and sputtering timing control. Background Art

[0002] The trend toward miniaturization of semiconductor coolers (TECs) also requires the integration and density of the cooler's thermally conductive PN junctions to be as high as possible. Metallization on ceramic substrates, such as aluminum nitride and aluminum oxide, is one of the steps in the fabrication of TEC (semiconductor cooler) integrated circuit structures.

[0003] The existing TEC metallization process is to sputter metal particles onto the front and side surfaces of the ceramic substrate through a sputtering source (a one-step method). This metallization method has the following shortcomings in controlling the thickness of the front surface and sidewalls:

[0004] ⑴ Uneven thickness distribution: Due to the directional deposition of sputtered particles, the deposition rate on the front surface is usually higher than that on the side wall (for example, the side wall thickness is only 30%-50% of that on the front surface), resulting in differences in electrical properties.

[0005] ⑵ High process complexity: Existing technologies (such as inclined sputtering and ion implantation-assisted deposition) require complex equipment modifications and have poor compatibility.

[0006] ⑶ Multiple etching waste: In order to achieve thickness balance, multiple deposition-etching cycles are often required, which increases material and time costs.

[0007] The above background technology is for facilitating understanding of the present invention and is not a known technology disclosed to the general public before the application of the present invention. Summary of the Invention

[0008] To address the above problems, the present invention provides a front-sidewall metallization thickness consistency control method based on alternating shielding and sputtering timing control, which can achieve front / sidewall Ti, Pt, and Au thickness consistency without affecting the bonding strength.

[0009] A method for controlling the thickness uniformity of front-side wall metallization based on alternating shielding and sputtering timing control comprises the following steps:

[0010] S1, take a ceramic substrate;

[0011] S2, applying a tape on the side wall surface of the ceramic substrate, wherein the tape is a tape with a temperature resistance of ≥300°C;

[0012] S3, metallization of the front side of the ceramic substrate: TiPtAu is sputtered onto the ceramic substrate from a sputtering source. The sputtering is magnetron sputtering. The sputtering conditions are:

[0013] Ti target, sputtering power 500W~900W, Ar gas pressure flow 15sccm~30sccm, Ti front deposition rate R Tiside , sputtering time t1 Ti ;

[0014] Pt target, sputtering power 500W~900W, Ar gas pressure flow 15sccm~30sccm, Pt front deposition rate R Ptside , sputtering time t1 Pt ;

[0015] Au target, sputtering power 500W~900W, Ar gas pressure flow 15sccm~30sccm, Au front deposition rate R Auside , sputtering time t1 Au；

[0016] S4, peeling off the tape on the side wall of the ceramic substrate and applying the tape on the front surface of the ceramic substrate;

[0017] S5, side metallization of ceramic substrate: TiPtAu is sputtered onto the ceramic substrate from a sputtering source. The sputtering is magnetron sputtering. The sputtering conditions are:

[0018] Ti target, sputtering power 700W~1000W, Ar gas pressure flow 15sccm~30sccm, Ti side deposition rate R Tifront , sputtering time t2 Ti ;

[0019] Pt target, sputtering power 700W~1000W, Ar gas pressure flow 15sccm~30sccm, Pt side deposition rate R Ptfront , sputtering time t2 Pt ;

[0020] Au target, sputtering power 700W~1000W, Ar gas pressure flow 15sccm~30sccm, Au side deposition rate R Aufront , sputtering time t2 Au ;

[0021] Among them, k Ti = t2 Ti / t1 Ti = R Tiside / R Tifront , k Pt =t2 Pt / t1 Pt = R Ptside / R Ptfront , k Au =t2 Au / t1 Au =R Auside / R Aufront .

[0022] Optionally, in S2 and S4, when pasting, the tape coverage area extends outward by 200 μm to 500 μm.

[0023] Optionally, the tape is a polyimide tape.

[0024] Optionally, the ceramic substrate is an aluminum nitride ceramic substrate or an alumina ceramic substrate.

[0025] Optionally, in S3 and S5, during Ti sputtering, the sputtering power in S3 < the sputtering power in S5, t2 Ti >t1 Ti ; during Pt sputtering, the sputtering power in S3 < the sputtering power in S5, t2 Pt >t1 Pt ; during Au sputtering, the sputtering power in S3 < the sputtering power in S5, t2 Au >t1 Au .

[0026] Optionally, in S3, during Ti sputtering, the sputtering power is 650 W, the Ar gas pressure flow rate is 22 sccm, and the measured Ti front deposition rate R Tiside = 2.5 Å / S, the sputtering time t1 Ti = 800 s, the sidewall deposition target thickness is 2000 Å; during Pt sputtering, the sputtering power is 500 W, the Ar gas pressure flow rate is 22 sccm, and the measured Pt front deposition rate R Ptside = 5 Å / S, the sputtering time t1 Pt = 400 s, the sidewall deposition target thickness is 2000 Å; during Au sputtering, the sputtering power is 600 W, the Ar gas pressure flow rate is 22 sccm, and the measured Au front deposition rate R Auside = 10 Å / S, the sputtering time t1 Au = 100 s, the sidewall deposition target thickness is 1000 Å. [[ID=4[3]]

[0027] Optionally, the target thickness of sputtering Ti is 500 Å to 2000 Å, the target thickness of sputtering Pt is 500 to 2000 Å, and the target thickness of sputtering Au is 350 Å to 1000 Å.

[0028] Optionally, the ceramic substrate is a ceramic substrate for preparing a semiconductor cooler.

[0029] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0030] The present invention adjusts the target power and time, especially making k Ti = t2 Ti / t1 Ti = RTiside / R Tifront , k Pt =t2 Pt / t1 Pt = R Ptside / R Ptfront , k Au = t2 Au / t1 Au =R Auside / R Aufront , accurately offsetting the difference in front / sidewall deposition rates, so that the front / side metallization thickness is consistent, thereby improving the overall electrical performance and having a stronger bonding force.

[0031] The present invention also uses a strippable high-temperature tape to replace the hard mask, avoiding the photolithography process during metallization, and is not only applicable to planar substrates, but also to complex structures of non-planar substrates (such as silicon through vias, three-dimensional packaging, and MEMS devices). BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, a brief introduction will be given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0033] Figure 1 This is a graph showing the relationship between the sputtering time and thickness of the Ti front side of the present invention;

[0034] Figure 2 This is a graph showing the relationship between the sputtering time and thickness of the Pt positive side surface of the present invention;

[0035] Figure 3 This is a graph showing the relationship between the sputtering time and thickness of the front side of the present invention;

[0036] Explanation of the accompanying drawings: 1. front, 2. side. DETAILED DESCRIPTION

[0037] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to a fixed connection, an indirect connection via an intermediate medium, internal communication between two components, or an interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0038] In the description of the present invention, it should be understood that the terms "upper," "lower," "front," "back," "vertical," "horizontal," "top," "bottom," "inner," "outer," and the like, indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate and simplify the description of the present invention. They do not indicate or imply that the devices or elements referred to must have, be constructed, or operate in a specific orientation, and therefore should not be construed as limiting the present invention. In the description of the present invention, "plurality" means two or more, unless otherwise specifically specified.

[0039] The terms "first", "second", "third", "fourth", etc. (if any) in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequential order. It should be understood that the numbers used in this way can be interchangeable where appropriate, so that the embodiments of the present application described herein can, for example, be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device comprising a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0040] To make the purpose, technical solutions, and advantages of the embodiments of this application more clear, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the drawings in the embodiments of this application. Obviously, the described embodiments are part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0041] The following specific embodiments are used to describe the technical solution of the present invention in detail. The following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described in detail in some embodiments.

[0042] A method for controlling the thickness uniformity of front-side wall metallization based on alternating shielding and sputtering timing control comprises the following steps:

[0043] S1, take a ceramic substrate.

[0044] S2: Apply a peelable tape to the sidewall surface of the ceramic substrate (the front surface of the ceramic substrate is exposed at this time). During the application, the tape coverage area extends outward by 200-500 μm to avoid metal climbing caused by edge scattering.

[0045] The tape is a tape with a temperature resistance of ≥300°C. A peelable high-temperature tape is used instead of a hard mask to avoid a photolithography process. The tape can be applied not only to planar substrates but also to non-planar substrates.

[0046] S3, metallization of the front side of the ceramic substrate: TiPtAu is sputtered onto the ceramic substrate from a sputtering source. The sputtering is magnetron sputtering. The sputtering conditions are:

[0047] Ti target, sputtering power 500W~900W, Ar gas pressure flow 15sccm~30sccm, Ti front deposition rate R Tiside , sputtering time t1 Ti .

[0048] Pt target, sputtering power 500W~900W, Ar gas pressure flow 15sccm~30sccm, Pt front deposition rate R Ptside , sputtering time t1 Pt .

[0049] Au target, sputtering power 500W~900W, Ar gas pressure flow 15sccm~30sccm, Au front deposition rate R Auside , sputtering time t1 Au。

[0050] S4, peel off the peelable tape on the side wall of the ceramic substrate, and apply the peelable tape to the front of the ceramic substrate (the side of the ceramic substrate is exposed at this time). During the application, the tape coverage area extends outward by 200-500μm to avoid metal climbing caused by edge scattering.

[0051] S5, side metallization of ceramic substrate: TiPtAu is sputtered onto the ceramic substrate from a sputtering source. The sputtering is magnetron sputtering. The sputtering conditions are:

[0052] Ti target, sputtering power 700W~1000W, Ar gas pressure flow 15sccm~30sccm, Ti side deposition rate R Tifront , sputtering time t2 Ti .

[0053] Pt target, sputtering power 700W~1000W, Ar gas pressure flow 15sccm~30sccm, Pt side deposition rate R Ptfront , sputtering time t2 Pt .

[0054] Au target, sputtering power 700W~1000W, Ar gas pressure flow 15sccm~30sccm, Au side deposition rate R Aufront , sputtering time t2 Au .

[0055] Among them, kTi = t2 Ti / t1 Ti = R Tiside / R Tifront , k Pt =t2 Pt / t1 Pt = R Ptside / R Ptfront , k Au =t2 Au / t1 Au =R Auside / R Aufront .

[0056] The metallized ceramic substrate is used to prepare a semiconductor refrigerator (TEC). The substrate can be aluminum nitride, aluminum oxide, or other ceramic substrates. Those skilled in the art can select the substrate as needed.

[0057] In the present invention, the relationship between the sputtering time and thickness of the Ti positive side is as follows: Figure 1 , the relationship between the sputtering time and thickness of the Pt positive side is as follows Figure 2 The relationship between the sputtering time and thickness of the Au positive side is as follows: Figure 3 , Figure 1-Figure 3 In the figure, 1 refers to the front and 2 refers to the side.

[0058] Example 1

[0059] In this embodiment, the sputtered metal for metallization of the ceramic substrate is TiPtAu, wherein the target thickness of Ti is 2000Å, the target thickness of Pt is 2000Å, and the target thickness of Au is 1000Å.

[0060] A method for controlling the thickness uniformity of front-side wall metallization based on alternating shielding and sputtering timing control comprises the following steps:

[0061] S1, take a ceramic substrate.

[0062] S2, apply polyimide tape to the sidewall surface of the ceramic substrate (the front surface of the ceramic substrate is exposed at this time). During the application, the tape coverage area extends outward by 200-500μm to avoid metal climbing caused by edge scattering.

[0063] S3, metallization of the front side of the ceramic substrate: TiPtAu is sputtered onto the ceramic substrate from a sputtering source. The sputtering is magnetron sputtering. The sputtering conditions are:

[0064] Ti target, sputtering power 650W, Ar gas pressure flow 22sccm, measured Ti front deposition rate R Tiside = 2.5 Å / S, sputtering time t1 Ti= 800s, with a sidewall deposition target thickness of 2000Å.

[0065] Pt target, sputtering power 500W, Ar gas pressure flow 22sccm, measured Pt front deposition rate R Ptside = 5 Å / s, sputtering time t1 Pt = 400s, sidewall deposition target thickness 2000Å.

[0066] Au target, sputtering power 600W, Ar gas pressure flow 22sccm, measured Au front deposition rate R Auside = 10 Å / s, sputtering time t1 Au = 100s, with a sidewall deposition target thickness of 1000Å.

[0067] S4, peel off the polyimide tape covering the side wall of the ceramic substrate, and apply polyimide tape to the front of the ceramic substrate (the side of the ceramic substrate is exposed at this time). During the application, the tape coverage area extends outward by 200-500μm to avoid metal climbing caused by edge scattering.

[0068] S5, side metallization of ceramic substrate: TiPtAu is sputtered onto the ceramic substrate from a sputtering source. The sputtering is magnetron sputtering. The sputtering conditions are:

[0069] Ti target, sputtering power 850W, Ar gas pressure flow 22sccm, measured Ti side deposition rate R Tifront = 1.8Å / S, sputtering time t2 Ti = 1111s, with a sidewall deposition target thickness of 2000Å.

[0070] Pt target, sputtering power 750W, Ar gas pressure flow 22sccm, measured Pt side deposition rate R Ptfront = 2 Å / s, sputtering time t2 Pt = 1000s, sidewall deposition target thickness 2000Å.

[0071] Au target, sputtering power 800W, Ar gas pressure flow 22sccm, measured Au side deposition rate R Aufront = 5.5 Å / s, sputtering time t2 Au = 182s, with a sidewall deposition target thickness of 1000Å.

[0072] The thickness of the ceramic substrate after S5 was tested by XRF, and the results are shown in Table 1 below.

[0073] The bonding strength of the ceramic substrate after S5 was tested, and the results are shown in Table 1 below.

[0074] Example 2

[0075] The difference between this embodiment and embodiment 1 is that in S5, the sputtering conditions are:

[0076] Ti target, sputtering power 650W, Ar gas pressure flow 22sccm, measured Ti side deposition rate R Tifront =0.8Å / s, sputtering time t2 Ti = 2500s, sidewall deposition target thickness 2000Å.

[0077] Pt target, sputtering power 500W, Ar gas pressure flow 22sccm, measured Pt side deposition rate R Ptfront =1.6Å / s, sputtering time t2 Pt = 1250s, sidewall deposition target thickness 2000Å.

[0078] Au target, sputtering power 600W, Ar gas pressure flow 22sccm, measured Au side deposition rate R Aufront =1.8Å / s, sputtering time t2 Au =556s, sidewall deposition target thickness 1000Å.

[0079] The thickness of the ceramic substrate after S5 was tested by XRF, and the results are shown in Table 1 below.

[0080] The bonding strength of the ceramic substrate after S5 was tested, and the results are shown in Table 1 below.

[0081] Comparative Example 1

[0082] In this comparative example, the sputtered metal for metallization of the ceramic substrate is TiPtAu, wherein the target thickness of Ti is 2000Å, the target thickness of Pt is 2000Å, and the target thickness of Au is 1000Å.

[0083] A method for metallizing a ceramic substrate comprises the following steps:

[0084] S1, take a ceramic substrate;

[0085] S2, metallization on the front and side of the ceramic substrate: TiPtAu is sputtered onto the ceramic substrate from a sputtering source. The sputtering is magnetron sputtering. The sputtering conditions are:

[0086] Ti target, sputtering power 650W, Ar gas pressure flow 22sccm, Ti sputtering time t Ti = 800s, deposition target thickness 2000Å.

[0087] Pt target, sputtering power 500W, Ar gas pressure flow 22sccm, Pt sputtering time t Pt = 400s, deposition target thickness 2000Å.

[0088] Au target, sputtering power 600W, Ar gas pressure flow 22sccm, Au sputtering time t Au = 100s, deposition target thickness 1000Å

[0089] The thickness of the ceramic substrate after S2 was tested by XRF, and the results are shown in Table 1 below.

[0090] Comparative Example 2

[0091] In this comparative example, the sputtered metal for metallization of the ceramic substrate is TiPtAu, wherein the target thickness of Ti is 2000Å, the target thickness of Pt is 2000Å, and the target thickness of Au is 1000Å.

[0092] A method for metallizing a ceramic substrate comprises the following steps:

[0093] S1, take a ceramic substrate;

[0094] S2, metallization on the front and side of the ceramic substrate: TiPtAu is sputtered onto the ceramic substrate from a sputtering source. The sputtering is magnetron sputtering. The sputtering conditions are:

[0095] Ti target, sputtering power 850W, Ar gas pressure flow 22sccm, Ti sputtering time t Ti = 1111s, deposition target thickness 2000Å.

[0096] Pt target, sputtering power 750W, Ar gas pressure flow 22sccm, Pt sputtering time t Pt = 1000s, deposition target thickness 2000Å.

[0097] Au target, sputtering power 800W, Ar gas pressure flow 22sccm, Au sputtering time t Au = 182s, deposition target thickness 1000Å.

[0098] The thickness of the ceramic substrate after S2 was tested by XRF, and the results are shown in Table 1 below.

[0099] The bonding strength of the ceramic substrate after S5 was tested, and the results are shown in Table 1 below.

[0100] Table 1 Performance test

[0101] In Table 1, the bonding strength is based on Example 1.

[0102] As can be seen from the table, after the front surface of Example 2 was sputtered using the same sputtering power, the side bonding strength was poor and easy to fall off. In the case of Comparative Example 1 and Comparative Example 2 without the shielding one-step method, although the front side bonding strength of Comparative Example 2 was OK, the thickness difference of the front side was large and could not meet customer requirements. If the front surface is sputtered at high power using a shielding method, this will reduce the utilization rate of the target material and increase the cost of precious metal use. Example 1 uses a method of partial sputtering with different sputtering powers, which not only improves the utilization rate of precious metals, but also can obtain a film layer that meets the requirements.

[0103] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for controlling the thickness uniformity of front-side wall metallization based on alternating shielding and sputtering timing control, characterized in that: The following steps are involved: S1, take the ceramic substrate; S2, applying a tape on the side wall surface of the ceramic substrate, wherein the tape is a tape with a temperature resistance of ≥300°C; S3, metallization of the front side of the ceramic substrate: TiPtAu is sputtered onto the ceramic substrate from a sputtering source. The sputtering is magnetron sputtering. The sputtering conditions are: Ti target, sputtering power 500W~900W, Ar gas pressure flow 15sccm~30sccm, Ti front deposition rate R Tiside , sputtering time t1 Ti ; Pt target, sputtering power 500W~900W, Ar gas pressure flow 15sccm~30sccm, Pt front deposition rate R Ptside , sputtering time t1 Pt ; Au target, sputtering power 500W~900W, Ar gas pressure flow 15sccm~30sccm, Au front deposition rate R Auside , sputtering time t1 Au； S4, peeling off the tape on the side wall of the ceramic substrate and applying the tape on the front surface of the ceramic substrate; S5, side metallization of ceramic substrate: TiPtAu is sputtered onto the ceramic substrate from a sputtering source. The sputtering is magnetron sputtering. The sputtering conditions are: Ti target, sputtering power 700W ~ 1000W, Ar gas pressure flow 15sccm ~ 30sccm, Ti side deposition rate R Tifront , sputtering time t2 Ti ; Pt target, sputtering power 700W ~ 1000W, Ar gas pressure flow 15sccm ~ 30sccm, Pt side deposition rate R Ptfront , sputtering time t2 Pt ; Au target, sputtering power 700W ~1000W, Ar gas pressure flow 15sccm ~ 30sccm, Au side deposition rate R Aufront , sputtering time t2 Au ; Among them, k Ti = t2 Ti / t1 Ti = R Tiside / R Tifront , k Pt =t2 Pt / t1 Pt = R Ptside / R Ptfront , k Au =t2 Au / t1 Au =R Auside / R Aufront .

2. The method for controlling the thickness uniformity of the front-side wall metallization based on alternating shielding and sputtering timing control according to claim 1, characterized in that: In S2 and S4, the tape coverage area extends outward by 200 μm to 500 μm during lamination.

3. The method for controlling the thickness uniformity of the front-side wall metallization based on alternating shielding and sputtering timing control according to claim 1, characterized in that: The adhesive tape is a polyimide adhesive tape.

4. The method for controlling the thickness uniformity of front-side wall metallization based on alternating shielding and sputtering timing control according to claim 1, wherein: The ceramic substrate is an aluminum nitride ceramic substrate or an aluminum oxide ceramic substrate.

5. The method for controlling the thickness uniformity of front-side wall metallization based on alternating shielding and sputtering timing control according to claim 1, wherein: In S3 and S5, during Ti sputtering, the sputtering power in S3 < the sputtering power in S5, t2 Ti > t1 Ti ; during Pt sputtering, the sputtering power in S3 < the sputtering power in S5, t2 Pt > t1 Pt ; during Au sputtering, the sputtering power in S3 < the sputtering power in S5, t2 Au > t1 Au .

6. The method for controlling the thickness uniformity of front-side wall metallization based on alternating shielding and sputtering timing control according to claim 1, wherein: In S3, when Ti is sputtered, the injection power is 650W, the Ar gas pressure flow rate is 22sccm, and the Ti front deposition rate R is measured. Tiside = 2.5 Å / S, sputtering time t1 Ti = 800s, the sidewall deposition target thickness is 2000Å; during Pt sputtering, the sputtering power is 500W, the Ar gas pressure flow rate is 22sccm, and the Pt front deposition rate R is measured. Ptside = 5 Å / s, sputtering time t1 Pt =400s, the sidewall deposition target thickness is 2000Å; during Au sputtering, the sputtering power is 600W, the Ar gas pressure flow rate is 22sccm, and the Au front deposition rate R is measured. Auside = 10 Å / s, sputtering time t1 Au = 100s, with a sidewall deposition target thickness of 1000Å.

7. The method for controlling the thickness uniformity of front-side wall metallization based on alternating shielding and sputtering timing control according to any one of claims 1 to 5, characterized in that: The target thickness for sputtered Ti is 500Å~2000Å, the target thickness for sputtered Pt is 500Å~2000Å, and the target thickness for sputtered Au is 350Å~1000Å.

8. The method for controlling the thickness uniformity of front-side wall metallization based on alternating shielding and sputtering timing control according to any one of claims 1 to 5, characterized in that: The ceramic substrate is a ceramic substrate used for preparing semiconductor refrigerators.

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