Method for metallising semiconductor elements and use thereof
11 claims: 1 independent, 10 dependent
- 1半導体素子の少なくとも一つの表面をアルミニウムで少なくとも部分的に金属化する方法であって、 a)アルミニウム箔を前記表面と少なくとも部分的に直接接触させる段階と、 b)続いて、レーザまたはコヒーレントでない赤外線の効果によって、前記アルミニウム箔を少なくとも部分的に前記半導体素子の前記表面に接続する段階と、 を有し、 前記アルミニウム箔を前記表面と少なくとも部分的に直接接触させる段階は、金属化される対象の前記半導体素子の前記表面の寸法よりも大きな寸法を有し、前記半導体素子上に載置され端部を覆う前記アルミニウム箔を、前記表面に吸着させる段階を含み、 前記アルミニウム箔を前記表面に吸着させる段階は、 前記半導体素子 および前記アルミニウム箔を共に真空デバイスを用いて安全に吸着させる段階を含 み 、 前記アルミニウム箔を少なくとも部分的に前記半導体素子の前記表面に接続する段階は、前記アルミニウム箔を一時的に加熱して、前記表面又は前記表面と前記アルミニウム箔との間に設けられる犠牲層を局所的に溶解する段階を含む、 方法。
- 2前記アルミニウム箔の厚みは、1μmから20μmである、 請求項1に記載の方法。
- 3前記アルミニウム箔はさらに、金属構造を有する、 請求項1または請求項2に記載の方法。
- 4前記金属構造は、前記アルミニウム箔内に長尺状の金属部分として形成される、 請求項3に記載の方法。
- 5前記金属構造は、別の半導体素子との接続に用いられる、 請求項3または請求項4に記載の方法。
- 6前記レーザは、予め定められている構造に照射される、 請求項1から請求項5までの何れか一項に記載の方法。
- 7前記レーザによって、長尺状部分および/または点状構造が形成される、 請求項1から請求項6までの何れか一項に記載の方法。
- 8太陽電池が前記半導体素子として利用される、 請求項1から請求項7までの何れか一項に記載の方法。
- 9前記金属化された部分は、背面側コンタクトとして前記太陽電池に設けられる 請求項8に記載の方法。
- 10太陽電池を製造するための方法であって、 a)半導体素子を準備する段階と、 b)請求項1から請求項9までの何れか一項に記載の方法により、前記半導体素子の少なくとも一つの表面をアルミニウムで少なくとも部分的に金属化する段階と、 を有する方法。
- 11前記半導体素子の少なくとも一つの表面をアルミニウムで少なくとも部分的に金属化する段階は、前記半導体素子の背面側の表面を金属化する段階を含む、 請求項10に記載の方法。
Independent claims11
13 paragraphs, as filed
The present invention relates to a method for metallizing a semiconductor device using aluminum. The present invention can be cost effective, especially in the case of products where processing costs have a significant impact, such as silicon-based solar cells. The present invention also relates to the use of this method, for example, in a solar cell production process.
In the case of crystalline solar cells, which are currently the mainstream, the back contact is formed by mixing an aluminum-containing screen printing paste and a silicon material. The paste is heated for a short time at a temperature higher than the melting point to form an integral aluminum layer. Such an aluminum layer ensures the lateral conductivity of the backside metallization. Further, by mixing aluminum and silicon to form a eutectic, the electrical characteristics on the back side of the solar cell are improved.
<p> According to the above processing procedure, good conductivity is obtained, but the electrical and optical properties are only mediocre. In addition, the heat load required for the paste mixing step limits the possibility of further optimizing the solar cell, for example, because not all subsequent processes provide temperature stability.</p><p> Optical and electrical properties can be significantly improved by first passivating the back side with a dielectric layer made of, for example, silicon oxide, silicon nitride or amorphous silicon. Subsequently, the back surface side is metallized with an aluminum layer. The formation of the aluminum layer is typically carried out by a vacuum method such as vapor deposition coating or sputtering.</p><p> In the case of the method described above, a problem arises due to the vacuum. Here, vacuum should be understood as a pressure of less than 1 mbar. Since a vacuum is created (that is, the processing chamber is exhausted), the processing time is long and the cost is high. Further, a special substance that emits a gas in a vacuum cannot be coated in a vacuum. The third problem is that it is not possible to deposit layers exactly in place in a vacuum. That is, material consumption increases and the processing chamber is contaminated, which can reduce the quality of the coated device.</p><p> When a dielectric layer is used, various methods can be used to subsequently bring the aluminum layer into contact with the silicon. In particular, the LFC method can be used.</p><p> An object of the present invention is to realize a method for coating a semiconductor surface at low cost and at high speed using aluminum at a low processing temperature. This object can be achieved by a method having the characteristics of claim 1. The use of the method according to the present invention is described in claim 18. Each of the dependent terms defines a further advantageous embodiment of the present invention.</p>
<p> In the method according to the present invention, at least one surface of the semiconductor device is at least partially metallized with aluminum, a) the aluminum foil is at least partially in direct contact with the surface, and b) subsequently by energy effect. Includes connecting the aluminum foil, at least in part, to the surface of the semiconductor device.</p><p> Placement of the aluminum foil (step a) is carried out using an appropriate method. It is indispensable that the aluminum foil and the substrate are partially in direct contact with each other. This direct contact is important because otherwise it would only result in holes being formed in the aluminum foil without being adhered to the substrate. For this reason, the direct contact may be frictional and / or the shape may be engaged.</p><p> According to one preferred embodiment, the placement of the aluminum foil (step a) is accomplished by pressing, spraying, and / or adsorbing the aluminum foil against the surface.</p><p> According to an alternative preferred embodiment, the placement of the aluminum foil (step a) is achieved by a liquid film disposed between the surface and the aluminum foil. Therefore, in the present invention, the formation of the liquid film is carried out with the aluminum foil already placed on the surface of the substrate to be coated, or the substrate and / or the aluminum foil is pre-wet and then wetted. It does not matter whether the aluminum foil is placed on the substrate or not. As the liquid film, a water film and / or a solvent film can be used.</p><p> According to another preferred embodiment of the method, the placement of the aluminum foil (step a) is achieved by a sacrificial layer disposed between the surface and the aluminum foil. For this reason, the sacrificial layer is preferably selected from the group consisting of amorphous silicon, dielectric layers, metal layers, layers formed of organic materials, and / or foils formed of these materials. Therefore, the sacrificial layer utilized is completely dissolved in the aluminum foil in step b of the method. For example, when amorphous silicon is used, it completely melts in aluminum when the temperature is about 400 degrees Celsius or higher. The sacrificial layer may be pre-populated on the surface of the aluminum foil or device, similar to the liquid film.</p><p> According to the method according to the present invention, an aluminum foil having an arbitrary layer thickness can be placed on the surface of the semiconductor, and the thickness is preferably 1 μm to 20 μm.</p><p> Further, it is desirable that the dimensions of the aluminum foil match the dimensions of the surface of the semiconductor element to be metallized.</p><p> However, instead of this, the size of the aluminum foil can be made larger than the size of the surface of the semiconductor element to be metallized.</p><p> It is also preferable that the aluminum foil further has a metallic structure. For example, instead of the homogeneous aluminum foil, a foil further having a thin elongated metal portion for connecting the individual semiconductor elements to each other can be used. This elongated metal portion may be simultaneously adhered to the foil, project beyond the end defining the semiconductor element, and be connected to another semiconductor element. As an alternative example of this, a means for electrically connecting individual elements, which is known to those skilled in the art and standard, can be provided below the aluminum foil before the start of processing. The means is adhered to the substrate in step b of the method. It may be adhered to both the substrate and the foil at the same time.</p><p> The connection of the aluminum foils obtained by feature b) is achieved at least in the area where the aluminum foils are in direct contact with the surface.</p><p> A laser can be used to efficiently connect the aluminum foil to the surface partially and entirely (step b of the method). Therefore, it is possible to easily realize a connection having good adhesion. The laser irradiation is guided from above to the aluminum foil and temporarily and strongly heats the aluminum foil to locally melt the substrate or the sacrificial layer provided between them. The laser can also irradiate a given structure. For example, the pattern provided on the foil can also be irradiated. As a result, elongated portions and punctate structures can be formed. The laser is not limited to any particular one, but it is essential that it have a certain wavelength and the strength to at least partially dissolve the aluminum foil. Specifically, an infrared laser can be used. However, the energy effect according to the present invention is not limited to laser treatment alone, and any other suitable embodiment that produces the desired effect is similarly appropriate. For example, the aluminum foil may be irradiated with infrared rays that are sufficiently strong and not coherent.</p><p> This method is particularly suitable when the solar cell is used as a semiconductor element. For this reason, the metallized portion is preferably formed on the solar cell as a back contact.</p>
<figref num="1">It is a figure which shows the reflection curve of the metallized solar cell which concerns on this invention measured by a reflection test assembly.</figref>
The present invention will be described in more detail below with reference to examples. However, the present invention is not limited to the specific embodiments disclosed herein.
For this reason, a variety of suitable methods are used to bring the aluminum foil into direct contact with the substrate. This direct contact is important because otherwise it would only result in holes being formed in the aluminum foil without being adhered to the substrate. Examples of suitable methods for direct contact include mechanical pressing, spraying, and / or adsorption. Further, as a method of adhering the aluminum foil to the substrate, a method of dropping a few drops of liquid between the substrate and the aluminum foil and removing almost all of the liquid for these several drops can be considered. A third possibility is to utilize additional sacrificial layers that dissolve in additional processing steps performed after the placement of the aluminum foil. For this purpose, amorphous silicon, which is completely soluble in aluminum at temperatures above 400 degrees Celsius, is used.
According to a test conducted in advance, the aluminum foil was adhered to the sample by vacuum adsorption. To this end, the aluminum foil was placed on the sample to cover the edges and both the sample and the aluminum foil were safely adsorbed on the processing table using a vacuum device. As a result of performing such a process, all the air existing in the meantime is removed, and the aluminum foil is provided over the entire surface of the sample.
As a final step, the aluminum foil is adhered to the substrate by laser irradiation to obtain a well-adhered connection. This laser irradiation is guided from above with respect to the aluminum foil and temporarily strongly heats the aluminum foil to locally melt the substrate or the sacrificial layer provided between them. The laser irradiates the aluminum foil according to various patterns and treats the aluminum foil over or only partially. Elongated structures and dotted structures can be formed.
There are several possibilities for the relative positioning of the aluminum foil and the substrate. As an example, the aluminum foil may be located at the correct location on the substrate and have dimensions corresponding to the substrate. Therefore, the entire surface and a part of the surface can be metallized. Another possibility is to provide an aluminum foil with a much larger surface area than the substrate, beyond the edges of the substrate. In this case as well, the aluminum foil and the substrate may be completely bonded or only a part thereof may be bonded. In the final laser irradiation step, the aluminum foil may be cut into small pieces to the substrate size or any shape by changing the laser parameters. By cutting with a laser, the edge of the aluminum foil and the edge of the substrate can be adhered well. Aluminum foil protruding beyond the edges of the substrate can be cut. The residual portion of such an aluminum foil may be removed.
The features of the present invention will be clarified in more detail with reference to the examples given below and FIG. However, the subject matter of the present invention is not limited to the specific embodiments referred to in the examples below.
<Example> Dimensions are 20 x 20 mm<sup>2</sup>The above-mentioned solar cell, which does not have a front structure in the float zone silicon, is measured using a current-voltage test assembly for measuring the brightness characteristic line. The structure of the solar cell includes a silicon wafer having a thickness of 250 μm having an emitter layer (to realize a pn junction of the solar cell) on the front surface, an antireflection coating, and front side metallization. This type of structure is also called a high efficiency structure because high efficiency can be achieved if the treatment is properly controlled with the appropriate materials. With such a structure, the variants used in the experiment can be more clearly distinguished by suppressing the leak channels as much as possible to prevent adverse effects. A dielectric coating is applied to the back surface side, and the dielectric coating is provided with a commercially available aluminum foil (for example, one sold in a supermarket having a thickness of about 14 μm) according to the present invention. By doing so, the aluminum foil is fixed to the back side by the adsorption device and adhered at a plurality of points by laser irradiation. The parameters representing the quality of the solar cells shown in the table below were obtained.<tables num="1"><img file="JP5111507B2_D0001.tif" /></tables>
FIG. 1 is a diagram showing a reflection curve of a metallized solar cell according to the present invention as measured by a reflection test assembly. An Ulbricht globe is used to illuminate the sample and measure the rate of reflection as a function of wavelength. Comparing with a reference solar cell (that is, a solar cell not manufactured according to the method according to the invention), it can be seen that in the wavelength band larger than 1000 nm, the reflection is substantially equal on the back side. However, in such a wavelength band, the absorption length of silicon is smaller than the thickness of the solar cell, so that it is hardly suitable for emitting electrons. For wavelength bands associated with current products (ie, less than 1000 nm), there is no difference in reflectivity between reference solar cells and solar cells coated according to the methods according to the invention. Therefore, it is possible to realize a back surface coating having substantially the same reflectivity by a significantly simplified control method.<u style="single">(Item 1)</u><u style="single"> A method of at least partially metallizing at least one surface of a semiconductor device with aluminum.</u><u style="single"> a) Bringing the aluminum foil into direct contact with the surface, at least in part,</u><u style="single"> b) Subsequently, by energy effect, the aluminum foil is at least partially connected to the surface of the semiconductor device.</u><u style="single"> How to include.</u><u style="single">(Item 2)</u><u style="single"> The placement of the aluminum foil (step a) is realized by pressing, spraying, and / or adsorbing the aluminum foil against the surface.</u><u style="single"> The method described in item 1.</u><u style="single">(Item 3)</u><u style="single"> The placement of the aluminum foil (step a) is realized by a liquid film disposed between the surface and the aluminum foil.</u><u style="single"> The method described in item 1.</u><u style="single">(Item 4)</u><u style="single"> Use a water film and / or a solvent film as the liquid film,</u><u style="single"> The method described in item 3.</u><u style="single">(Item 5)</u><u style="single"> The placement of the aluminum foil (step a) is realized by a sacrificial layer disposed between the surface and the aluminum foil.</u><u style="single"> The method described in item 1.</u><u style="single">(Item 6)</u><u style="single"> As the sacrificial layer, an amorphous silicon, a dielectric layer, a metal layer, a layer formed from an organic material, and / or a foil formed from these materials is used.</u><u style="single"> The method described in item 5.</u><u style="single">(Item 7)</u><u style="single"> The thickness of the aluminum foil is 1 μm to 20 μm.</u><u style="single"> The method according to at least one of items 1 to 6.</u><u style="single">(Item 8)</u><u style="single"> The dimensions of the aluminum foil match the dimensions of the surface of the semiconductor element to be metallized.</u><u style="single"> The method according to at least one of items 1 to 7.</u><u style="single">(Item 9)</u><u style="single"> The size of the aluminum foil is larger than the size of the surface of the semiconductor element to be metallized.</u><u style="single"> The method according to at least one of items 1 to 7.</u><u style="single">(Item 10)</u><u style="single"> The aluminum foil further has a metallic structure.</u><u style="single"> The method according to at least one of items 1 to 9.</u><u style="single">(Item 11)</u><u style="single"> The metal structure is formed as an elongated metal portion in the aluminum foil.</u><u style="single"> The method described in item 10.</u><u style="single">(Item 12)</u><u style="single"> The metal structure is used for connection with another semiconductor element.</u><u style="single"> The method according to item 10 or item 11.</u><u style="single">(Item 13)</u><u style="single"> Connecting the aluminum foil to the surface at least partially (step b) is achieved by the effect of the laser.</u><u style="single"> The method according to at least one of items 1 to 12.</u><u style="single">(Item 14)</u><u style="single"> The laser irradiates a predetermined structure.</u><u style="single"> The method described in item 13.</u><u style="single">(Item 15)</u><u style="single"> The laser forms elongated portions and / or point structures.</u><u style="single"> The method according to item 14 or item 15.</u><u style="single">(Item 16)</u><u style="single"> A solar cell is used as the semiconductor element.</u><u style="single"> The method according to at least one of items 1 to 15.</u><u style="single">(Item 17)</u><u style="single"> The metallized portion is provided on the solar cell as a back contact.</u><u style="single"> The method described in item 16.</u><u style="single">(Item 18)</u><u style="single"> Use of the method according to at least one of items 1 to 17 for metallizing a solar cell.</u><u style="single">(Item 19)</u><u style="single"> The use according to item 18, as a contact on the back side of the solar cell.</u>
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Every citation, both ways
| Document | Relation | Office |
|---|---|---|
| JP2004127987A | Cites | Japan |
| JP07249868A | Cites | Japan |
| DE10020412A1 | Cites | Germany |
| JP57089268A | Cites | Japan |
| JP2003246971A | Cites | Japan |
11 members in 6 offices
Priority claims3
| Document | Office | Kind | Date |
|---|---|---|---|
| 1020060449363 | Germany | – | |
| 102006044936 | Germany | A | |
| 2007008279 | European Patent Office (EPO) | W |
Members11
| Document | Office | Kind | |
|---|---|---|---|
| DE102006044936A1 | Germany | A1 | |
| WO2008034638A2 | World Intellectual Property Organization (WIPO) | A2 | |
| WO2008034638A3 | World Intellectual Property Organization (WIPO) | A3 | |
| DE102006044936B4 | Germany | B4 | |
| EP2064748A2 | European Patent Office (EPO) | A2 | |
| US2009221112A1 | United States of America | A1 | |
| CN101529601A | China | A | |
| JP2010504632A | Japan | A | |
| US8003530B2 | United States of America | B2 | |
| JP5111507B2This record | Japan | B2 | |
| EP2064748B1 | European Patent Office (EPO) | B1 |
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Numbers
- Publication
- 5111507
- Application
- 2009528652
Titles2
- Japanese
- 半導体素子を金属化する方法およびその利用
- English
- Methods for metallizing semiconductor devices and their use
Classification
- CPC, 2
- H10F77/211
- Y02E10/50
- IPC, 2
- H01L31 04
- H10P14 40
