JP6312134B2 - Method for manufacturing substrate with germanium layer and substrate with germanium layer - Google Patents

Description

  The present invention relates to a method for manufacturing a substrate with a germanium layer.

  With the recent popularization of bendable display devices such as organic EL (Electro-Luminescence), there is an increasing expectation for the development of electronic devices that have a high degree of freedom in carrying and use and are flexible throughout. For example, by using a flexible material for not only a display device but also a plate-like member such as an exterior housing or a substrate, it can be folded and rolled, or can be worn as a wearable device. Usability is expected to be realized.

  In order to realize such a flexible device, first, it is realistic that the substrate portion is made of a resin material such as bendable PET (polyethylene terephthalate) or PP (polypropylene). On the other hand, in order to increase the processing speed, it is preferable to use an inorganic material (for example, silicon (Si)) having a much higher electron mobility than the organic material as the semiconductor material.

JP 2002-373858 JP

Journal of ELECTRONIC MATERIALS, USA, The Minerals, Metals & Materials Society, Vol. 33, No. 4, p. 353-357

  Here, as an inorganic semiconductor material, germanium (Ge), which is a group IV semiconductor material that operates with lower electric power than Si, has attracted attention in recent years. However, since Ge is difficult to obtain an ingot single crystal, it has not been used so much in mass production. However, Ge is a useful semiconductor material if the above difficulties in the manufacturing process are solved. Therefore, many attempts have been made to crystallize a-Ge after once generating amorphous Ge (a-Ge).

  For example, Patent Document 1 discloses that after a compound semiconductor film having an amorphous structure such as amorphous silicon germanium (a-SiGe) is formed on an insulating film, thermal crystallization is promoted on the semiconductor film. It is described that a metal-containing layer is formed and an amorphous semiconductor film is crystallized by utilizing an increase in stress of the insulating film due to heat treatment. In this document, heat treatment is performed multiple times at different temperatures in order to increase the stress of the insulating film. For this reason, in this document, high heat-resistant glass such as quartz glass is used as the substrate, and the maximum heating temperature is It far exceeds the softening point of a general resin material (for example, about 180 ° C. for PET).

  On the other hand, Non-Patent Document 1 discloses that an amorphous Ge (a-Ge) thin film is formed on a flexible substrate made of PET, and then the flexible substrate is bent to generate stress in the a-Ge film. It is described that the film can be crystallized at a temperature significantly lower than the normal crystallization temperature. The document also describes forming a copper (Cu) film as a crystallization-inducing metal on the a-Ge film. However, in this document, since a method of applying external stress by bending the flexible substrate itself on which a-Ge (and Cu) is deposited is applied, stress is also applied to portions other than the element to be crystallized. There is a problem of adversely affecting.

  The present invention has been made in view of the above circumstances, and the object of the present invention is a method for producing a substrate with a germanium layer, which can easily form a crystalline germanium layer at a desired location on a flexible substrate, And providing a substrate with a germanium layer manufactured by the method.

The manufacturing method of the substrate with a germanium layer according to the present invention made to solve the above problems,
a) forming an amorphous germanium layer on the substrate;
b) forming a crystallization-inducing metal layer that promotes crystallization of amorphous germanium on the formed germanium layer;
c) forming a stress applying layer for applying stress to the crystallization-inducing metal layer on the crystallization-inducing metal layer by a plasma deposition method at an ambient temperature of 80 ° C. to 280 ° C .;
It is characterized by including.

According to the above configuration, the amorphous germanium layer formed on the substrate starts to crystallize from the boundary with the crystallization-inducing metal layer due to the stress applied by the stress application layer, and spreads over the whole. go. Furthermore, since the atmospheric temperature at the time of forming the stress application layer is 280 ° C. or less, even if polyimide is used as the material of the flexible substrate, for example, the substrate deformation due to heat can be avoided. Further, since the germanium layer and the stress application layer can be formed only at the target location of the substrate by masking or the like, unnecessary (sometimes harmful) stress is not applied to other locations on the substrate. Thus, a flexible substrate in which a crystalline germanium layer is formed at a desired location can be easily manufactured.
The plasma deposition method is suitable for forming a layer at a low temperature, and the internal stress of the stress application layer can be freely set by adjusting the forming conditions.

The stress applying layer is preferably a silicon dioxide (SiO ₂ ) layer, more preferably a silicon dioxide layer formed using tetraethyl orthosilicate (TEOS) as a raw material.
Orthoethyl silicate is excellent in that it is highly safe for the human body and easy to handle.

  According to the present invention, it is possible to easily form a crystalline germanium layer at a desired location on a flexible substrate.

Explanatory drawing of the 1st process (a), 2nd process (b), and 3rd process (c) of the manufacturing method of the board | substrate with Ge layer which concerns on one Embodiment of this invention. An enlarged top view near the edge of the crystallization-inducing metal layer formed on the Ge layer of the substrate with the Ge film when no stress is applied by the stress application layer in one example of the embodiment (a), (a (B) of a partially enlarged view of the rectangular area shown in FIG. 5) and a Raman spectrum (c) for each area detected by the Raman mapping. In the same example, an enlarged top view near the edge of the crystallization-inducing metal layer formed on the Ge layer of the substrate with the Ge film when tensile stress (200 MPa) is applied by the stress applying layer (a), ( The Raman mapping (b) of the partially enlarged view of the rectangular area shown in a) and the Raman spectrum (c) for each area detected by the Raman mapping. In the same example, an enlarged top view near the edge of the crystallization-inducing metal layer formed on the Ge layer of the substrate with the Ge film when compressive stress (-100 MPa) is applied by the stress application layer (a), The Raman mapping (b) of the partial enlarged view of the rectangular area shown to (a), and the Raman spectrum (c) for every area | region detected by this Raman mapping. In the same example, an enlarged top view near the edge of the crystallization-inducing metal layer formed on the Ge layer of the substrate with the Ge film when compressive stress (-200 MPa) is applied by the stress applying layer (a), The Raman mapping (b) of the partial enlarged view of the rectangular area shown to (a), and the Raman spectrum (c) for every area | region detected by this Raman mapping. The plot figure which shows the stress dependence of the crystal growth distance of the horizontal direction (plane direction) of the a-Ge layer in the Example. FIG. 6 is an explanatory diagram showing the relationship between the lateral crystal growth distance around the crystallization-inducing metal layer and the relative position in the stress application layer region in the experimental example shown in FIG. 5.

  Hereinafter, an embodiment of a method for producing a substrate with a Ge layer according to the present invention will be described with reference to FIGS. In the following description, members having the same functions as those in the above-described drawings are denoted by the same reference numerals, and description thereof is omitted.

  FIG. 1 is an explanatory diagram of each step in the method for manufacturing the substrate 100 with a Ge layer according to the present embodiment. In this embodiment, first, as shown in (a), the a-Ge layer 30 is formed on the substrate 10 coated with the insulating film 20. If the substrate 10 is made of an insulating material, the insulating film 20 can be omitted.

  Next, as shown in FIG. 2B, a crystallization inducing metal layer 40 is formed on the a-Ge layer 30. The crystallization-inducing metal layer 40 is mainly composed of a metal that forms a eutectic with Ge. In the figure, the crystallization-inducing metal layer 40 is formed so as to cover a part of the upper surface of the a-Ge layer 30 in order to observe lateral crystal growth in the verification experiment described later. It may be formed so as to cover the entire upper surface of 30.

Subsequently, as shown in FIG. 3C, the TEOS-SiO ₂ layer 50 is formed on the crystallization-inducing metal layer 40 (and the region not covered with the crystallization-inducing metal layer 40 on the a-Ge layer 30). (Corresponding to the stress application layer of the present invention). The TEOS-SiO ₂ layer 50 is formed by introducing tetraethyl orthosilicate (TEOS) gas into a reaction tube heated to about 80 ° C. to 200 ° C. using a plasma CVD (plasma-enhanced chemical vapor deposition) method. It is a silicon dioxide (SiO ₂ ) layer. After the TEOS-SiO ₂ layer 50 is formed, the temperature in the reaction tube provided in the film forming apparatus is maintained and left for a predetermined time. During this standing time, the crystallization-inducing metal layer 40 (and the region not covered with the crystallization-inducing metal layer 40 on the a-Ge layer 30) is compressed or pulled by the stress inherent in the TEOS-SiO ₂ layer 50. This stress is applied. How much stress is applied can be arbitrarily set by adjusting the formation conditions of the TEOS-SiO ₂ layer 50 by the plasma CVD method.

〔Example〕
In order to verify the effect of the present embodiment, a plurality of experiments (Experimental Examples 1 to 4) were performed with all conditions other than the applied stress all being aligned. Specifically, an a-Ge layer 30 having a film thickness of 100 nm is formed on a Si substrate (substrate 10) coated with a SiO ₂ film as the insulating film 20 by using a sputtering method, and then a vacuum evaporation method (mask A polka dot pattern of a gold (Au) layer 40 having a film thickness of 200 nm was formed on the a-Ge layer 30 by vapor deposition. And by the plasma CVD method, maintaining the heater temperature TEOS-SiO ₂ layer 50 having a thickness of 500nm after forming on the Au layer (the crystallization inducing metal layer 40) at ambient temperature 150 ℃, TEOS-SiO ₂ layer 50 When 60 minutes had elapsed from the start of the formation of the substrate, the substrate with Ge layer 100 was taken out of the film formation apparatus. The amount of crystal growth of the a-Ge layer 30 in the manufactured substrate 100 with a Ge layer was evaluated using Raman spectroscopy. For the sake of accuracy, the intensity of laser light irradiated in Raman spectroscopy is appropriately attenuated by a neutral density filter, and in all experimental examples, crystallization due to temperature rise in the measurement target region due to laser light irradiation occurs. It was confirmed by microscopic observation that it did not occur.

<Experimental example 1: no stress>
First, as a control experiment, FIG. 2 shows the result when no stress is applied to the crystallization-inducing metal layer 40 (applied stress value by the TEOS-SiO ₂ layer 50: 0). FIG. 4A is an enlarged top view near the edge of a circular crystallization-inducing metal layer 40 (Au layer), with the crystallization-inducing metal layer 40 on the left side and the a-Ge layer 30 on the right side. Has been. FIG. 2B shows a Raman mapping of a partially enlarged view of the rectangular area indicated by a white frame in FIG. In the same figure, the crystallization of a-Ge is not confirmed around the edge of the crystallization-inducing metal layer 40, and the rectangular region is divided into an a-Ge layer 30 region and a crystallization-inducing metal layer 40 region. ing. FIG. 2C shows a Raman spectrum of each region detected by Raman mapping. The spectrum 130 in the region of the a-Ge layer 30 has a gentle peak in the vicinity of the Raman shift of 280 cm ⁻¹ , indicating that a-Ge crystallization has not occurred in the region. When a-Ge is crystallized, a sharp peak appears in the vicinity of the Raman shift of 300 cm ^{−1 in} the spectrum of the region, but such a peak was not found in the spectrum 140 of the region of the crystallization-inducing metal layer 40. That is, it is considered that at least observable crystallization has not occurred even immediately below the crystallization-inducing metal layer 40.

<Experimental example 2: Tensile stress (200 MPa)>
Next, FIG. 3 shows the result when a tensile stress of 200 MPa is applied to the crystallization induction metal layer 40 due to the internal stress of the TEOS-SiO ₂ layer 50. In this experimental example, as indicated by an arrow in FIG. 5A, a crystalline Ge (c-Ge) region 31 was observed so as to surround the periphery of the edge of the crystallization-inducing metal layer 40. A spot-like region that is one step darker than the left and right ends and appears in the center of the Raman mapping shown in FIG. 3B is the c-Ge region 31. In the Raman spectrum shown in FIG. 3C, the spectrum 131 of the c-Ge region 31 has a steep peak near the Raman shift of 300 cm ⁻¹ , and the region is crystallized, that is, the a-Ge layer 30 is lateral. It shows that the crystal grows in the direction. Further, a slight peak appears at the same position in the spectrum 140 in the region of the crystallization-inducing metal layer 40, and it can be seen that crystallization is occurring directly under the crystallization-inducing metal layer 40.

<Experimental example 3: Compressive stress (-100 MPa)>
Next, FIG. 4 shows a result when a compressive stress of −100 MPa is applied to the crystallization induction metal layer 40 due to the internal stress of the TEOS-SiO ₂ layer 50. Similar to Experimental Example 2, a c-Ge region 31 surrounding the periphery of the edge of the crystallization-inducing metal layer 40 was observed (FIGS. 1A and 1B). In addition, the Raman shift shown in FIG. 5C also showed a tendency similar to that of Experimental Example 2 although the peak near 300 cm ⁻¹ was slightly small.

<Experimental example 4: Compressive stress (-200 MPa)>
Next, FIG. 5 shows a result when a compressive stress of −200 MPa is applied to the crystallization induction metal layer 40 due to internal stress of the TEOS-SiO ₂ layer 50. The approximate tendency is the same as in the above experimental examples 2 and 3. However, in this experimental example, the result that the width of the c-Ge region 31, that is, the crystal growth distance in the lateral direction is larger than that in the above two examples. Obtained ((a) and (b) in the figure). Further, as shown in FIG. 5C, a steep peak is observed in the vicinity of the Raman shift of 300 cm ⁻¹ not only in the c-Ge region 31 but also in the spectrum 140 of the region of the crystallization-inducing metal layer 40, It was shown that significant crystallization occurred just below the metal layer 40.

<Stress dependence of crystal growth distance>
Based on the results of Experimental Examples 1 to 4, the relationship between the crystal growth distance (lateral direction) of the a-Ge layer 30 and the applied stress by the TEOS-SiO ₂ layer 50 is shown in FIG. As shown in the figure, at least the lateral crystal growth is not observed without stress, and both tensile stress and compressive stress promote crystallization. However, if the absolute value of the stress value is taken into consideration, the compression (-200 MPa) shows a growth twice as long as the tension (200 MPa), and therefore it is highly likely that compression is more effective for the applied stress.

<Position dependence of crystal growth distance>
The TEOS-SiO ₂ layer 50 is subjected to stronger stress at the edge than at the center of the formation region. Therefore, a-Ge layer 30 in a positional relationship shown in FIG. 7 (a), if the crystallization inducing metal layer 40 (Au layer) pattern and TEOS-SiO ₂ layer 50 are stacked, the edge of the TEOS-SiO ₂ layer 50 In the vicinity of the crystallization-inducing metal layer 40 located in the vicinity of the portion (FIG. 7B), the vicinity of the crystallization-inducing metal layer 40 in a position closer to the central portion of the TEOS-SiO ₂ layer 50 (FIG. 7C). The width of the c-Ge region 31, that is, the crystal growth distance in the lateral direction tends to be large. Further, according to FIGS. 7B and 7C, when compressive stress is applied to the crystallization-inducing metal layer 40 and the a-Ge layer 30, the TEOS-SiO ₂ layer 50 is moved toward the center of the center. Crystal growth seems to progress well. Using these properties, in addition to the conditions for forming the TEOS-SiO ₂ layer 50, the shape of the TEOS-SiO ₂ layer 50 itself, the crystallization inducing metal layer with consideration of the position relationship between the TEOS-SiO ₂ layer 50 40 It is conceivable to improve the efficiency of crystal growth by devising the arrangement of patterns. FIG. 7 is an image obtained under the same experimental conditions as in Experimental Example 4.

<Experimental Example 5: Compressive stress (-200 MPa) + Ambient temperature 80 ° C.>
As an attempt to further lower the temperature, in Experimental Example 4 described above, when the ambient temperature during the formation of the TEOS-SiO ₂ layer 50 was set to 80 ° C., the c-Ge region was detected although it was slight by Raman mapping. Even in the detected Raman spectrum of the c-Ge region, a small peak is observed in the vicinity of the Raman shift of 300 cm ⁻¹ , and the a-Ge layer 30 grows in the lateral direction even under the low temperature environment as in this experimental example. It was shown that.

As described above, according to the present embodiment, crystallization of the a-Ge layer 30 starting from the boundary with the crystallization-inducing metal layer 40 is performed at a very low temperature (150 ° C. or less) by the stress applied by the TEOS-SiO ₂ layer 50. ). If it is this temperature, even if it uses resin materials, such as polycarbonate excellent in the lightness and comparatively cheap PET, as a board | substrate, it does not soften by heat processing. Therefore, crystallization of the amorphous germanium layer formed on the flexible substrate can be easily realized, thereby contributing to the realization of a lightweight and inexpensive flexible device.
Furthermore, the applied stress can be freely adjusted according to the formation conditions of the TEOS-SiO ₂ layer 50 by the plasma CVD method, and is suitable for forming a layer at a low temperature.
In addition, since the TEOS-SiO ₂ layer 50 can be formed only at a target location on the substrate 10 by masking or the like, it is unnecessary at other locations on the substrate 10 and sometimes causes damage to the substrate or components on the substrate. Stress is not applied.

  The present invention is not limited to the above-described embodiments, and appropriate modifications are allowed within the scope of the gist of the present invention. For example, the main component constituting the crystallization-inducing metal layer 40 is not limited to Au used in the above-described embodiments, and for example, eutectic is formed with Ge such as tin (Sn), silver (Ag), and aluminum (Al). Any metal material having properties may be used.

  In the experimental examples 1 to 5 described above, the heat treatment time is unified to 60 minutes for comparison, but if this time is further extended, the crystal growth distance naturally increases. Further, regarding the atmospheric temperature of 150 ° C., if the temperature is further increased, crystal growth is further promoted, so that it may be appropriately set according to the softening point of the material used as the substrate. For example, a polyimide substrate can withstand a high temperature of about 280 ° C. Moreover, the film thickness of each layer is not limited to the above-mentioned value, and can be arbitrarily changed.

DESCRIPTION OF SYMBOLS 10 ... Substrate 100 ... Ge layered substrate 130 ... Raman spectrum 131 in a-Ge layer region ... Raman spectrum in c-Ge region 140 ... Raman spectrum in crystallization-induced metal layer region 20 ... Insulating film 30 ... a-Ge layer 31 ... c-Ge region 40 ... crystallization-inducing metal layer 50 ... TEOS-SiO ₂ layer

Claims (4)

a) forming an amorphous germanium layer on the substrate;
b) forming a crystallization-inducing metal layer that promotes crystallization of amorphous germanium on the formed germanium layer;
c) forming a stress applying layer for applying stress to the crystallization-inducing metal layer on the crystallization-inducing metal layer by a plasma deposition method at an ambient temperature of 80 ° C. to 280 ° C .;
The manufacturing method of the board | substrate with a germanium layer characterized by including these. Furthermore, after the stress applying layer is formed by a plasma deposition method, the step of maintaining the ambient temperature and leaving it for a predetermined time
  The manufacturing method of the board | substrate with a germanium layer of Claim 1 characterized by the above-mentioned. Method for producing a germanium layer-attached substrate according to claim 1 or 2, characterized in that the stress applying layer is a silicon dioxide layer. The method of manufacturing a substrate with a germanium layer according to claim 3 , wherein the stress application layer is a silicon dioxide layer formed using tetraethyl orthosilicate as a raw material.