JP2008177182A - Process for fabricating thin film device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transfer technique which separates a transfer source substrate and a thin film element more surely. <P>SOLUTION: The process for fabricating a thin film device using a transfer technique comprises steps of: (a) forming a peeling layer (12) on one side of a first substrate (10); (b) forming an intermediate layer (14) having a difference in linear expansion coefficient from that of the peeling layer on the peeling layer; (c) forming a transferred body (16) including a thin film element (18) on the intermediate layer; (d) bonding one side of a second substrate (22) to the transferred body; (e) reducing the bonding strength of the peeling layer and the transferred body; and (f) separating the first substrate and the transferred body. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to the manufacture of a thin film device (for example, a thin film transistor) using a transfer technique.

  In recent years, flexible electronic devices that can be bent freely have attracted attention. These electronic devices typified by electronic paper can play a role in the ubiquitous society, such as lightness to carry, absorbability of shock, and flexibility to adapt to hands. As a means for realizing such an electronic device, a method of manufacturing a thin film element such as a thin film transistor using a transfer technique is known (see, for example, Japanese Patent Laid-Open No. 10-125929). This thin film element transfer technique is to form a thin film element (transfer object) such as a thin film transistor once on a transfer source substrate (for example, on a glass substrate), and then place the thin film element from the transfer source substrate at any place ( For example, it refers to a technique for transferring to the surface of a plastic substrate. According to this technique, it is possible to freely form a thin film element even in a place where it is difficult to directly form the thin film element, such as on a plastic substrate. For this reason, the transfer technology is being researched and developed as an important technology for realizing flexible electronic devices. In this transfer technique, a release layer (sacrificial layer) made of an amorphous silicon film or the like is previously formed on a transfer source substrate, and a thin film element is formed on the release layer. Thereafter, the adhesion (bonding strength) between the transfer source substrate and the thin film element is lowered by, for example, irradiating the release layer with laser light, and the thin film element is peeled off. At this time, the thin film element can be moved from the transfer source substrate to the transfer destination location by bonding the thin film element to the transfer destination location using an adhesive or the like.

However, in the above transfer technology, when a step (peeling step) for reducing the bonding strength between the thin film element and the transfer source substrate by laser light irradiation or the like is performed, the film quality of the amorphous silicon film or the like as the peeling layer or the peeling Due to variations in film quality (inhomogeneity) of the lower layer (for example, SiO ₂ film) of the thin film element adjacent to the layer, the thin film element may not be separated cleanly from the transfer source substrate. Due to this defect, the yield when manufacturing the thin film element using the transfer technique is lowered. Accordingly, it is desired to realize a transfer technique that can more reliably separate the transfer source substrate and the thin film element.

Japanese Patent Laid-Open No. 10-125929

  Accordingly, an object of the present invention is to provide a transfer technique that can more reliably separate a transfer source substrate and a thin film element.

A method for manufacturing a thin film device according to the present invention includes:
(A) forming a release layer on one surface of the first substrate;
(B) forming an intermediate layer having a difference in linear expansion coefficient between the release layer and the release layer;
(C) forming a transferred body including a thin film element on the intermediate layer;
(D) bonding one surface of the second substrate to the transfer object;
(E) Decreasing the bonding strength between the release layer and the transfer object by applying energy;
(F) separating the first substrate and the transfer object;
Is a method for manufacturing a thin film device.

  Here, the “thin film element” includes, for example, a thin film transistor, a thin film diode, other thin film semiconductor elements, a thin film circuit including the semiconductor element, a photoelectric conversion element used for a solar cell, an image sensor, and a switching element. , Actuators such as memory, piezoelectric elements, micromirrors (piezo thin film ceramics), magnetic recording media, magneto-optical recording media, recording media such as optical recording media, magnetic recording heads, coils, inductors, thin-film highly permeable materials and the like Combined micro magnetic devices, filters, reflective films, dichroic mirrors, polarizing elements, etc. optical thin films, semiconductor thin films, superconducting thin films (eg YBCO thin films), magnetic thin films, metal multilayer thin films, metal ceramic multilayer thin films, metal semiconductor multilayer thin films Ceramic semiconductor multilayer thin film, organic thin film and multilayer thin film of other materials, etc. Murrell.

  According to the above manufacturing method, by providing a difference in the value of the linear expansion coefficient between the release layer and the intermediate layer, a shear stress is generated when a temperature change occurs in each layer due to the application of energy. By utilizing this shear stress, it becomes possible to favorably peel off the transfer object from the first substrate. Accordingly, it is possible to more reliably separate the transfer source substrate and the thin film element and improve the manufacturing yield of the thin film element.

As the intermediate layer in the above (b), for example, Al ₂ O ₃ film, sapphire film, 3Al ₂ O ₃ .2SiO ₂ film, 2MgO.2Al ₂ O ₃ .5SiO ₂ film, MgO.SiO ₂ film, 2MgO.SiO _{2 Two} films, Y ₂ O ₃ films, TiO ₂ films, SiC films, Si ₃ N ₄ films, AlN films, ZrO ₂ films and the like are preferably used. These films may be used as a single layer, or two or more kinds may be laminated.

  By using these, the difference in the value of linear expansion coefficient between the release layer made of, for example, an amorphous silicon film or the like becomes more remarkable, and the release can be realized better.

  As the peeling layer in (a) above, for example, an amorphous silicon film is preferably used as described above. At this time, the amorphous silicon film is more preferably formed by chemical vapor deposition. As the chemical vapor deposition method, for example, a low pressure chemical vapor deposition method (LPCVD method) or a plasma chemical vapor deposition method (PECVD method) is suitable.

  Thereby, a region containing more hydrogen can be disposed near the interface with the intermediate layer in the release layer. This region with a high hydrogen content is preferable for causing a peeling phenomenon by applying energy by laser irradiation or the like. By having such a high hydrogen-containing region in the vicinity of the interface with the intermediate layer, it acts synergistically with the above-described shear stress, and it becomes possible to generate peeling more satisfactorily.

  More preferably, (a) forms the release layer by removing the surface layer portion of the amorphous silicon film formed by chemical vapor deposition. The surface layer cannot be generally defined depending on the film formation conditions of the amorphous silicon film, but generally refers to a region of about several tens of nanometers from the surface of the amorphous silicon film (surface to be in contact with the intermediate layer). For example, the release layer may be formed by forming the amorphous silicon film by PECVD and removing the surface layer portion of the amorphous silicon film by 10 to 20 nm. Alternatively, the release layer may be formed by forming the amorphous silicon film by LPCVD and removing the surface layer portion of the amorphous silicon film by 10 to 25 nm.

  Here, it is preferable that the hydrogen content of the portion of the release layer in contact with the intermediate layer is higher than the hydrogen content of the surface layer portion of the amorphous silicon film. By removing the surface layer portion, a region having a particularly large hydrogen content in the amorphous silicon film can be disposed in the vicinity of the interface between the release layer and the intermediate layer. Thereby, said synergistic action increases more.

  The transferred object in (c) may include a diffusion preventing layer in contact with the intermediate layer. The diffusion preventing layer refers to a layer that prevents (suppresses) the diffusion of foreign matter from the intermediate layer or the like to the transfer target. For example, a highly dense film such as a silicon nitride film is preferably used.

  Thereby, even if it is a case where the film | membrane containing an alkali ion etc. is employ | adopted as an intermediate | middle layer, for example, the spreading | diffusion of the impurity to a to-be-transferred body can be suppressed.

  The application of energy in the above (e) is preferably performed by light irradiation. More specifically, it is preferable to use a laser.

  Thereby, local energy provision becomes easy. In particular, when an amorphous silicon film is used as the release layer as described above, or when the surface layer of the amorphous silicon film is removed in addition to this, the light is focused on the vicinity of the interface between the release layer and the intermediate layer. By irradiating the film, it becomes possible to more efficiently cause peeling while reducing the influence on other portions.

  In addition, after the application of the energy in (e), the release layer and the intermediate layer are cooled to reduce the bonding strength between the release layer and the transfer target, thereby generating a larger stress. And peeling may be promoted.

  The thin film device manufacturing method described above can also be applied to the manufacture of various electronic devices. Here, the “electronic device” means a general device having a circuit board and other elements and having a certain function, and there is no particular limitation on its configuration. Such electronic devices include, for example, IC cards, mobile phones, video cameras, personal computers, head mounted displays, digital camera finders, electronic notebooks, and the like.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Hereinafter, as one embodiment to which the present invention is applied, a technique of forming a thin film transistor on a substrate and transferring the thin film transistor onto another substrate will be exemplified.

  1 and 2 are schematic cross-sectional views illustrating a method for manufacturing a thin film device of this embodiment. First, a release layer 12 is formed on one surface of a transfer source substrate (first substrate) 10 (FIG. 1A). As the transfer source substrate 10 in this step, a heat-resistant material (quartz glass, soda glass, etc.) having an appropriate thickness (for example, about 700 μm) and capable of withstanding a process temperature of about 350 ° C. to 1000 ° C. when manufacturing a semiconductor device. ) Is used. The use of such a light-transmitting substrate as the transfer source substrate 10 is convenient in the subsequent transfer process. This point will be described later. Moreover, as the peeling layer 12, what has the characteristic which produces peeling by receiving energy provision, such as light irradiation, is used. For example, an amorphous silicon film is preferably used as the release layer 12. In the case where a semiconductor element is formed in a subsequent process, the peeling layer 12 can also be formed using the manufacturing equipment, so that there is no need to change the process significantly, and there is no influence such as diffusion of metal into the semiconductor element. Because. The thickness of the amorphous silicon film may be determined as appropriate, and can be about 100 nm, for example. Note that a metal film, a conductive oxide film, a conductive polymer film, a conductive ceramic, or the like can be used as the release layer 12. These are detailed in the above-mentioned Patent Document 1.

Next, the intermediate layer 14 is formed over the release layer 12 (FIG. 1B). As the intermediate layer 14, a layer having a difference in linear expansion coefficient with the release layer 12 is used. Specifically, when the linear expansion coefficient of the release layer 12 is α _A and the linear expansion coefficient of the intermediate layer 14 is α _B , the absolute value | α _A −α _B | of the difference between α _A and α _B is 0. A film having a numerical value other than (either a single layer film or a multilayer film) may be used as the intermediate layer 14 in the present embodiment. More specifically, the case is alpha than _A alpha _B larger, and when alpha is also alpha _B is less than _A, are considered two patterns. Thus, when the difference in the linear expansion coefficient between the peeling layer 12 and the intermediate layer 14 that are in contact with each other is large, the stress generated between the layers increases due to temperature change. Thereby, peeling of the peeling layer 12 can be accelerated | stimulated in a subsequent process using stress.

ここで、α_Aは膜Ａの線膨張係数、α_Bは膜Ｂの線膨張係数、Ｅ_Aは膜Ａのヤング率である。例えば、膜Ａがアモルファスシリコン膜（ａ−Ｓｉ膜）、膜Ｂが酸化シリコン膜（ＳｉＯ₂膜）であり、レーザー照射により溶融したアモルファスシリコン膜がその融点である１４５０℃から室温である２０℃に冷却される場合を考える。温度が８００℃のとき、α_Aは６．０２×１０^-6[℃^-1]、α_Bは１．４５×１０^-6[℃^-1]、Ｅ_Aは１５８[ＧＰａ]である。線膨張係数およびヤング率がこの温度範囲で一定であると仮定すると、この温度変化によってアモルファスシリコン膜Ａに発生する応力σ_Aは以下の通り、１０３０［ＧＰａ］の引っ張り応力（図３（Ａ）に矢印で示す。）となる。
σ_A ＝Ｅ_A（α_B−α_A）×ΔＴ
＝１５８×（−４．５７×１０^-6)×（−１４３０）
＝１０３０［ＧＰａ］
この膜間に発生する応力が大きければ大きいほど引っ張り応力による変形（図３（Ｂ）に模式的に示す。）が生じ、剥離が容易になる。大きな応力を発生させるには上記数式（１）に基づき、膜間の線膨張係数差（α_B−α_A）が大きい方がよい。本実施形態では、剥離層１２としてアモルファスシリコン膜を採用しているので、このアモルファスシリコン膜との間で線膨張係数差が大きい材料を選定し、剥離層１２と接する中間層１４を形成すればよい。二つの層の線膨張係数の比は、例えば１０倍以上あることが望ましい。このような中間層１４（別言すれば、せん断応力発生層）としては、例えば、Ａｌ₂Ｏ₃膜（アルミナ膜）、サファイア膜、３Ａｌ₂Ｏ₃・２ＳｉＯ₂膜（ムライト膜）、２ＭｇＯ・２Ａｌ₂Ｏ₃・５ＳｉＯ₂膜（コージライト膜）、ＭｇＯ・ＳｉＯ₂膜（ステアタイト膜）、２ＭｇＯ・ＳｉＯ₂膜（フォルステライト膜）、Ｙ₂Ｏ₃膜（イットリア膜）、ＴｉＯ₂膜（チタニア膜）、ＳｉＣ膜（炭化硅素膜）、Ｓｉ₃Ｎ₄膜（窒化硅素膜）、ＡｌＮ膜（窒化アルミニウム膜）又はＺｒＯ₂膜（ジルコニア膜）、などが好適に用いられる。これらのいずれか１つを中間層１４としてもよく、２つ又はそれ以上を適宜組み合わせて（積層して）中間層１４としてもよい。中間層１４として採用し得るこれらの膜の線膨張係数を図４に示す。代表的な数値を挙げると、例えばアルミナ膜の４０〜４００℃における線膨張係数は７．１×１０^-6[℃^-1]となり、シリコン膜との間での線膨張係数差（α_B−α_A）が大きくなる。他の例も同様である。 Here, the intermediate layer 14 will be described in detail with reference to FIG. FIG. 3 is a schematic diagram showing a structure in which two types of films A and B are stacked. The stress σA generated in the film A as the temperature changes from T1 to T2 is expressed by the following equation.

Here, the alpha _A linear expansion coefficient of the film A, the alpha _B linear expansion coefficient of the film B, the E _A is the Young's modulus of film A. For example, the film A is an amorphous silicon film (a-Si film), the film B is a silicon oxide film (SiO ₂ film), and the amorphous silicon film melted by laser irradiation is from its melting point of 1450 ° C. to room temperature of 20 ° C. Consider the case of cooling. When the temperature is 800 ° C., the ^{_{α A 6.02 × 10 -6 [℃}} -1], α B is ^{1.45 × 10 -6 [℃ -1]} , E A is 158 [GPa]. Assuming that the linear expansion coefficient and Young's modulus are constant in this temperature range, the stress σ _A generated in the amorphous silicon film A due to this temperature change is 1030 [GPa] tensile stress as follows (FIG. 3A). Is indicated by an arrow).
σ _A = E _A (α _B −α _A ) × ΔT
= 158 × (−4.57 × 10 ⁻⁶ ) × (−1430)
= 1030 [GPa]
The greater the stress generated between the films, the more the deformation due to the tensile stress (schematically shown in FIG. 3B) occurs and the peeling becomes easier. In order to generate a large stress, it is preferable that the difference in linear expansion coefficient (α _B −α _A ) between the films is large based on the above formula (1). In this embodiment, since an amorphous silicon film is used as the release layer 12, a material having a large linear expansion coefficient difference with the amorphous silicon film is selected, and the intermediate layer 14 in contact with the release layer 12 is formed. Good. The ratio of the linear expansion coefficients of the two layers is preferably 10 times or more, for example. As such an intermediate layer 14 (in other words, a shear stress generating layer), for example, an Al ₂ O ₃ film (alumina film), a sapphire film, a 3Al ₂ O ₃ .2SiO ₂ film (mullite film), a 2MgO.multidot. 2Al ₂ O ₃ · 5SiO ₂ film (cordierite film), MgO · SiO ₂ film (steatite film), 2MgO · SiO ₂ film (forsterite film), Y ₂ O ₃ film (yttria film), TiO ₂ film ( A titania film), a SiC film (silicon carbide film), a Si ₃ N ₄ film (silicon nitride film), an AlN film (aluminum nitride film), a ZrO ₂ film (zirconia film), or the like is preferably used. Any one of these may be used as the intermediate layer 14, or two or more may be appropriately combined (laminated) to form the intermediate layer 14. The linear expansion coefficients of these films that can be employed as the intermediate layer 14 are shown in FIG. As representative values, for example, the linear expansion coefficient at 40 to 400 ° C. of the alumina film is 7.1 × 10 ⁻⁶ [° C. ⁻¹ ], and the difference between the linear expansion coefficients with the silicon film (α _B − α _A ) increases. The same applies to other examples.

Next, a transfer target (transfer target layer) 16 including a thin film transistor 18 is formed over the intermediate layer 14 (FIG. 1C). The transfer target 16 includes a base insulating film 20 in contact with the intermediate layer 14. For example, a silicon oxide (SiO ₂ ) film can be used as the base insulating film 20. The thin film transistor 18 includes a gate electrode 50, a semiconductor film 52, source / drain electrodes 54 and 56, a gate insulating film 58, and an interlayer insulating film 60. Further, a planarization film 62 and electrodes (extraction electrodes) 64 and 66 are added to constitute the transfer target 16. The thin film element that can be included in the transfer target 16 is not limited to this.

A known technique is appropriately used for manufacturing the transfer target 16 including the thin film transistor 18. An example thereof will be described with reference to FIG. First, a base insulating film 20 such as a SiO ₂ film is formed on the upper surface of the intermediate layer 14 (FIG. 5A). Next, a semiconductor film 52 is formed over the base insulating film 20 (FIG. 5B). For example, a semiconductor film such as an amorphous silicon film is formed on the entire upper surface of the base insulating film 20 by chemical vapor deposition, and after being appropriately crystallized by laser annealing or the like, it is patterned into an arbitrary shape. Next, a gate insulating film 58 such as a SiO ₂ film covering the base insulating film 20 and the semiconductor film 52 is formed (FIG. 5C). Next, the gate electrode 50 made of an aluminum film or the like is formed over the semiconductor film 52 and the gate insulating film 58 (FIG. 5D). Next, ion implantation is performed from the upper side of the gate electrode 50, whereby source / drain regions are formed in the respective regions at both ends of the semiconductor film 52 (regions excluding the region immediately below the gate electrode 50) (FIG. 5). (D)). Next, an interlayer insulating film 60 that covers the gate electrode 50 and the gate insulating film 58 is formed (FIG. 5E). For example, a SiO ₂ film is used as the interlayer insulating film 60. Next, through holes that expose the source / drain regions of the semiconductor film 52 are formed in the interlayer insulating film 60 by etching or the like. Next, a conductive film (for example, an aluminum film) is formed on the interlayer insulating film 60 and in the through hole by sputtering or the like. By appropriately patterning this conductive film, source / drain electrodes 54 and 56 electrically and physically connected to the source / drain regions are formed (FIG. 5E). Next, a planarizing film 62 covering the source / drain electrodes 54 and 56 is formed on the interlayer insulating film 60 (FIG. 5F). As the planarizing film 62, an acrylic resin film is formed by, for example, a spin coating method. The flattening film 62 has functions such as flattening the surface of the transfer target 16 and reducing bonding failure at the transfer destination, and is formed in a relatively thick film (for example, about 1.5 μm). Next, through holes for exposing the source / drain electrodes 54 and 56 are formed in the planarizing film 62 by etching or the like. Next, a conductive film (for example, an aluminum film) is formed on the planarizing film 62 and in the through hole by a sputtering method or the like. By appropriately patterning this conductive film, electrodes 64 and 66 electrically and physically connected to the source / drain electrodes 54 and 56, respectively, are formed (FIG. 5F).

  Next, the transfer medium 16 and the transfer destination substrate 22 are joined by interposing the adhesive 24 between the transfer target 16 on the transfer source substrate 10 and the transfer destination substrate (second substrate) 22 (see FIG. FIG. 1D). Examples of the adhesive 24 used in this step include acrylate resin-based and epoxy resin-based adhesives.

  Next, the release layer 12 is irradiated with laser through the transfer source substrate 10 (FIG. 2A). Thereby, peeling occurs in the interface between the peeling layer 12 and the transfer source substrate 10 or in the layer of the peeling layer 12, and the bonding strength between the peeling layer 12 and the transfer target 16 can be reduced. As described above, since the transfer source substrate 10 has translucency, energy can be applied to the release layer 12 by laser irradiation (light irradiation) in this step. Specifically, the release layer 12 is melted or ablated by irradiating the release layer 12 with a laser through the transfer source substrate 10. Ablation refers to a state in which a solid material that has absorbed irradiated light is excited photochemically or thermally, and its surface or internal atoms or molecules are disconnected and released. In this example, the release layer All or part of the twelve constituent materials appear as a phenomenon that causes phase change such as melting and transpiration (vaporization). In addition, a phase change may result in a fine foamed state, which may reduce the bonding force. The application of energy to the release layer 12 may be performed by a method other than laser irradiation. It is also preferable to further add a step of cooling the release layer 12 and the intermediate layer 14 after applying energy by laser irradiation or the like. As a result, a greater stress can be generated and peeling can be promoted.

  Next, the transfer source substrate 10 and the transfer target 16 are separated (FIG. 2B). As a result, the transfer target 16 is transferred from the transfer source substrate 10 to the transfer destination substrate 22 (FIG. 2C). For example, the transfer source substrate 10 is removed from the transfer body 16 by fixing the transfer destination substrate 22 by a method such as vacuum suction and applying an external force to the transfer source substrate 10. As described above, the transfer target 16 including the thin film element (in this example, a thin film transistor) is formed on the transfer destination substrate 22.

  The embodiment described with reference to FIGS. 1 and 2 is a one-time transfer process. Hereinafter, an embodiment regarding the two-time transfer process will be described with reference to FIGS. 6 and 7. The description overlapping with the one-time transfer process is appropriately omitted.

  First, in the same manner as in the above-described embodiment, the transfer target 16 and the temporary transfer are provided by interposing the adhesive 24a between the transfer target 16 on the transfer source substrate 10 and the temporary transfer substrate (second substrate) 22a. The substrate 22a is bonded (FIG. 6A). Here, the temporary transfer substrate 22a in this embodiment is a temporary transfer destination, unlike the transfer destination substrate 22 of the above embodiment. As the temporary transfer substrate 22a, various substrates such as a glass substrate such as quartz glass and soda glass, or a resin substrate can be adopted. In addition, as the adhesive 24a in the present embodiment, it is particularly preferable to use a water-soluble adhesive in consideration of ease of removal in a subsequent process, but is not limited thereto.

  Next, as in the above embodiment, the release layer 12 is irradiated with laser through the transfer source substrate 10 (FIG. 6A), thereby reducing the bonding strength between the release layer 12 and the transfer target 16. . Then, the transfer source substrate 10 and the transfer target 16 are separated (FIG. 6B). As a result, the transfer medium 16 is transferred from the transfer source substrate 10 to the temporary transfer substrate 22a.

  Next, the transfer material 16 and the transfer destination substrate 28 are joined by interposing the adhesive 26 between the transfer target 16 and the transfer destination substrate 28 on the temporary transfer substrate 22a (FIG. 6C). ). Examples of the adhesive 26 used in this step include acrylate resin-based and epoxy resin-based adhesive materials.

  Next, the adhesive 24a is removed, and the temporary transfer substrate 22a is separated from the transfer target 16 (FIG. 7A). In this embodiment, since the adhesive 24a is water-soluble as described above, the adhesive 24a can be dissolved and removed by supplying water as a dissolving liquid to the adhesive 24. . As a result, the transfer target 16 is transferred from the temporary transfer substrate 22a to the transfer destination substrate 28 (FIG. 7B).

Here, the modified example of the said embodiment is demonstrated below. It is preferable that the transfer target in the above-described embodiment further includes a diffusion preventing layer for suppressing an adverse effect on the thin film element due to the diffusion of foreign matters from the intermediate layer. This embodiment is shown in FIGS. 8 and 9, respectively. FIG. 8 is a schematic cross-sectional view showing the structure of a thin film device formed by a single transfer process. The transfer target 16 a shown in FIG. 8 includes a diffusion prevention layer 30 that is in contact with the intermediate layer 14, and is bonded to the transfer destination substrate 22 via an adhesive 24. FIG. 9 is a schematic cross-sectional view showing the structure of a thin film device formed by a two-time transfer process. 9 includes a diffusion prevention layer 30 that is in contact with the intermediate layer 14 and is bonded to a transfer destination substrate 28 via an adhesive material 26. The diffusion prevention layer 30 shown in FIG. 8 or FIG. 9 is formed in the intermediate layer 14 prior to the formation of the base insulating film 20 (see FIG. 5A) in the manufacturing process of the thin film transistor (thin film element) shown in FIG. Formed on top. As the diffusion preventing layer 30, for example, a silicon oxide (SiO ₂ ) film, a silicon nitride (SiN) film, a silicon oxynitride (SiON) film, or a laminate of these (laminated film) can be used. As a method for forming the diffusion prevention layer 30, a physical vapor deposition method (such as sputtering or vapor deposition) or a chemical vapor deposition method (such as LPCVD or PECVD) can be used as appropriate. The thickness of the diffusion preventing layer 30 is desirably 200 nm or more from the viewpoint of sufficiently preventing impurity diffusion, and desirably 1000 nm or less from the viewpoint of preventing generation of cracks in the subsequent process. In addition, by providing such a diffusion prevention layer 30 with a necessary and sufficient thickness, the base insulating film 20 in the above embodiment can be omitted.

  As another modified embodiment, it is also preferable to remove the surface layer portion of the release layer 12 when the release layer 12 is formed. This embodiment will be described with reference to FIG. First, similarly to the above embodiment, an amorphous silicon film 12 'is formed on the transfer source substrate 10 (FIG. 10A). For the formation of the amorphous silicon film 12 ', a chemical vapor deposition method such as a low pressure chemical vapor deposition method (LPCVD method) or a plasma enhanced chemical vapor deposition method (PECVD method) is suitable. The reason will be described later. Next, the surface layer portion of the amorphous silicon film 12 'is removed on the order of several tens of nanometers (FIG. 10B). Specific methods for removal include dry etching and wet etching. Chemical mechanical polishing (CMP) may be applied. By removing the surface layer portion of the amorphous silicon film 12 'in this way, the release layer 12 is obtained (FIG. 10C). By removing the surface layer portion, the surface of the release layer 12 is flattened, so that energy is uniformly applied to the entire film when energy is applied to the release layer 12 by laser irradiation or the like in a later step. Thereby, the effect of causing peeling more uniformly is expected. The reason for the effect of such surface layer removal will be described below with reference to FIGS.

  FIG. 11 shows the results of examining the profile in the depth direction of hydrogen contained in a silicon film (semiconductor film) formed by plasma enhanced chemical vapor deposition (PECVD) using nuclear reaction analysis (NRA). It is a graph. In FIG. 11, the absolute concentration (left vertical axis) of hydrogen contained in the silicon film is indicated by a solid line L11, and the ratio of the number of hydrogen atoms to the number of silicon atoms (right vertical axis) is indicated by a solid line L12. It can be seen that in the semiconductor film formed by the PECVD method, hydrogen is concentrated to a depth of about 35 nm from the surface, and the hydrogen amount is reduced to about 6 atm% and stabilized at a deeper portion. The region where hydrogen is concentrated is a region where peeling due to application of energy by laser irradiation or the like is likely to occur. That is, if hydrogen is contained, hydrogen is released by laser irradiation or the like, and an internal pressure is generated in the peeling layer 12, which becomes a force for peeling the transfer source substrate 10 and the intermediate layer 14. In the case of a silicon film having the characteristics shown in FIG. 11, the peeling layer 12 in which a region containing more hydrogen is arranged on the surface layer can be formed by removing the surface layer portion by about 10 nm to 20 nm. The thickness of the surface layer portion to be removed depends on the film forming conditions, and the above is an example. In consideration of the presence of a large amount of hydrogen up to a relatively deep position in the silicon film formed by PECVD, a silicon film that is about 15 to 35 nm thicker than the desired film thickness is formed as the release layer 12. It is desirable to remove the surface layer portion of the silicon film.

  FIG. 12 is a graph showing the results of examining the profile in the depth direction of hydrogen contained in a silicon film (semiconductor film) formed by a low pressure chemical vapor deposition method (LPCVD method) using a nuclear reaction analysis method (NRA). It is. Also in FIG. 12, the absolute concentration (left vertical axis) of hydrogen contained in the silicon film is indicated by a solid line L11, and the ratio of the number of hydrogen atoms to the number of silicon atoms (right vertical axis) is indicated by a solid line L12. Details of the measurement method and the like are the same as in the case of the PECVD method. It can be seen that in the silicon film formed by the LPCVD method, hydrogen is concentrated to a depth of about 30 nm from the surface. Accordingly, in the case of a silicon film having the characteristics shown in FIG. 12, the peeling layer 12 in which a region containing more hydrogen is arranged on the surface layer can be formed by removing the surface layer portion by about 10 nm to 25 nm. The thickness of the surface layer to be removed depends on the film formation conditions, and the above is an example. The silicon film formed by the LPCVD method does not enter hydrogen so deeply as compared with the silicon film formed by the PECVD method. Therefore, it is desirable to form a silicon film that is about 10 nm to 30 nm thicker than the desired thickness for the release layer 12 and remove the surface layer portion of the silicon film.

  As described above, according to the present embodiment, by providing a difference in the value of the linear expansion coefficient between the release layer and the intermediate layer, a shear stress is generated when a temperature change occurs in each layer due to energy application. By utilizing this shear stress, it becomes possible to favorably peel off the transfer object from the first substrate. Accordingly, it is possible to more reliably separate the transfer source substrate and the thin film element and improve the manufacturing yield of the thin film element.

  The present invention is not limited to the contents of the above-described embodiments, and various modifications can be made within the scope of the gist of the present invention. Although a thin film transistor is shown as an example of the thin film element, various thin film elements as exemplified above may be employed as the transfer target.

It is a schematic cross section explaining the manufacturing method of a thin film device. It is a schematic cross section explaining the manufacturing method of a thin film device. It is a schematic diagram which shows the structure where two types of films | membranes A and B were laminated | stacked. It is a figure which shows the linear expansion coefficient of the film | membrane which can be employ | adopted as an intermediate | middle layer. It is a schematic cross section explaining an example of a manufacturing process of a thin film transistor. It is a schematic cross section explaining the manufacturing method of a thin film device. It is a schematic cross section explaining the manufacturing method of a thin film device. It is a schematic cross section which illustrates the embodiment of the to-be-transferred body containing a diffusion prevention layer. It is a schematic cross section which illustrates the embodiment of the to-be-transferred body containing a diffusion prevention layer. It is a schematic cross section explaining the embodiment which removes the surface layer of a peeling layer. It is a graph which shows the profile of the depth direction of the hydrogen which the silicon film formed by the plasma enhanced chemical vapor deposition method contains. It is a graph which shows the profile of the depth direction of the hydrogen which the silicon film formed by the low pressure chemical vapor deposition method contains.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Transfer source substrate, 12 ... Release layer, 14 ... Intermediate layer, 16, 16a ... Transfer object, 18 ... Thin film transistor, 20 ... Underlying insulating film, 22, 22a ... Temporary transfer substrate (transfer destination substrate), 24, 24a , 26 ... Adhesive, 28 ... Transfer destination substrate, 30 ... Diffusion prevention layer, 50 ... Gate electrode, 52 ... Semiconductor film, 54 ... Drain electrode, 58 ... Gate insulation film, 60 ... Interlayer insulation film, 62 ... Planarization film 64 electrodes

Claims (10)

(A) forming a release layer on one surface of the first substrate;
(B) forming an intermediate layer having a difference in linear expansion coefficient between the release layer and the release layer;
(C) forming a transferred body including a thin film element on the intermediate layer;
(D) bonding one surface of the second substrate to the transfer object;
(E) Decreasing the bonding strength between the release layer and the transfer object by applying energy;
(F) separating the first substrate and the transfer object;
A method for manufacturing a thin film device. In claim 1,
The intermediate layer in (b) is an Al ₂ O ₃ film, sapphire film, 3Al ₂ O ₃ .2SiO ₂ film, 2MgO.2Al ₂ O ₃ .5SiO ₂ film, MgO.SiO ₂ film, 2MgO.SiO ₂ film. , Y ₂ O ₃ film, TiO ₂ film, SiC film, Si ₃ N ₄ film, AlN film, or ZrO ₂ film. In claim 1,
Said (a) is a manufacturing method of a thin film device including forming an amorphous silicon film by a chemical vapor deposition method. In claim 3,
(A) is a method of manufacturing a thin film device, wherein the release layer is formed by removing a surface layer portion of the amorphous silicon film. In claim 3,
(A) is a method for manufacturing a thin film device, in which the amorphous silicon film is formed by PECVD, and the surface layer portion of the amorphous silicon film is removed by 10 to 20 nm to form the release layer. In claim 3,
(A) is a method for manufacturing a thin film device, in which the amorphous silicon film is formed by LPCVD, and the release layer is formed by removing a surface layer portion of the amorphous silicon film by 10 to 25 nm. In any one of Claims 4 thru | or 6.
A method for manufacturing a thin film device, wherein a hydrogen content of a portion of the release layer in contact with the intermediate layer is higher than a hydrogen content of the surface layer portion of the amorphous silicon film. In any one of Claims 1 thru | or 7,
The method for manufacturing a thin film device, wherein the transfer object in (c) includes a diffusion prevention layer in contact with the intermediate layer. In any one of Claims 1 thru | or 8.
The method for producing a thin film device, wherein the application of the energy in (e) is performed by light irradiation. In any one of Claims 1 thru | or 9,
The manufacturing method of the thin film device which reduces the joint strength of the said peeling layer and the said to-be-transferred body by cooling the said peeling layer and the said intermediate layer after provision of the said energy in said (e).

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