TECHNICAL FIELD

The present invention relates to an object, a method, or a manufacturing method. The present invention also relates to a process, a machine, manufacture, or a composition of matter. In particular, one embodiment of the present invention relates to a semiconductor device, a display device, a light-emitting device, a driving method thereof, or a manufacturing method thereof. In particular, one embodiment of the present invention relates to a manufacturing method of a flexible device.

BACKGROUND ART

In recent years, a flexible device in which a semiconductor element, a light-emitting element, and the like are provided over a flexible substrate has been developed. Typical examples of the flexible device include, as well as a lighting device and an image display device, a variety of semiconductor circuits including a semiconductor element such as a transistor.

As a manufacturing method of a semiconductor device including a flexible substrate, a technique has been developed in which after a semiconductor element such as a thin film transistor is formed over a support substrate such as a glass substrate or a quartz substrate, the semiconductor element is transferred to a flexible substrate. In this technique, a step of peeling a layer including the semiconductor element from the support substrate is needed.

For example, Patent Document 1 discloses the following peeling technique using laser ablation: a separation layer formed of amorphous silicon or the like is formed over a substrate, a layer to be peeled which is formed of a thin film element is formed over the separation layer, and the layer to be peeled is bonded to a transfer body with the use of a bonding layer. The separation layer is ablated by laser light irradiation, so that peeling is generated in the separation layer.

In addition, Patent Document 2 discloses the following peeling technique: a metal layer is formed between a substrate and an oxide layer and separation is generated at an interface between the oxide layer and the metal layer by utilizing weak bonding at the interface between the oxide layer and the metal layer, so that a layer to be peeled and the substrate are separated from each other.

[Patent Document 1] Japanese Published Patent Application No. H10-125931

[Patent Document 2] Japanese Published Patent Application No. 2003-174153

DISCLOSURE OF INVENTION

When a peeling interface has low ease of peeling, or peelability at the time of peeling of a semiconductor element from a support substrate, high stress is applied to the semiconductor element, breaking the semiconductor element in some cases.

In view of the above, an object of one embodiment of the present invention is to provide a peeling method with improved peelability, or the like. Another object is to increase yield in a peeling step. Another object is to increase yield in manufacturing a flexible device or the like. Another object is to provide a highly reliable semiconductor device or the like. Another object is to provide a highly reliable semiconductor device provided with a flexible substrate. Another object is to provide a novel semiconductor device or the like. Another object is to provide a method for manufacturing a novel semiconductor device or the like. Note that the descriptions of these objects do not disturb the existence of other objects. In one embodiment of the present invention, there is no need to achieve all the objects. Other objects will be apparent from and can be derived from the description of the specification, the drawings, the claims, and the like.

One embodiment of the present invention is a peeling method including a first step of forming a peeling layer containing tungsten over a support substrate; a second step of forming, over the peeling layer, a layer to be peeled in which a first layer containing silicon oxynitride and a second layer containing silicon nitride are sequentially stacked and an oxide layer containing tungsten oxide between the peeling layer and the layer to be peeled; a third step of forming a compound containing tungsten and nitrogen in the oxide layer by heat treatment; and a fourth step of peeling the peeling layer from the layer to be peeled at the oxide layer.

In addition, a fifth step of performing plasma treatment on a surface of the peeling layer in an atmosphere containing dinitrogen monoxide is preferably performed between the first step and the second step.

In the second step, the first layer containing silicon oxynitride satisfying the following conditions is preferably formed: the silicon oxynitride includes a region in which the nitrogen content measured by secondary ion mass spectrometry (SIMS) is greater than or equal to 5.0×1020molecules/cm3and less than or equal to 1.0×1023molecules/cm3and a region in which the hydrogen content is greater than or equal to 1.0×1020molecules/cm3and less than or equal to 1.0×1022molecules/cm3.

In the second step, the first layer containing silicon oxynitride satisfying the following conditions is preferably formed: the amount of nitrogen released from the silicon oxynitride is greater than or equal to 5×1017molecules/cm3when converted into nitrogen molecules, at temperatures ranging from 100° C. to 450° C. in a spectrum obtained by thermal desorption spectrometry (TDS) at a mass-to-charge ratio of 28, and the amount of hydrogen released from the silicon oxynitride is greater than or equal to 5×1019molecules/cm3when converted into hydrogen molecules, at temperatures ranging from 100° C. to 450° C. in a spectrum obtained by TDS at a mass-to-charge ratio of 2.

Further, in the second step, the second layer containing silicon nitride satisfying the following conditions is preferably formed: the amount of nitrogen released from the silicon nitride is less than or equal to 5×1019molecules/cm3when converted into nitrogen molecules, at temperatures ranging from 100° C. to 450° C. in a spectrum obtained by TDS at a mass-to-charge ratio of 28, and the amount of hydrogen released from the silicon nitride is greater than or equal to 1×1020molecules/cm3when converted into hydrogen molecules, at temperatures ranging from 100° C. to 450° C. in a spectrum obtained by TDS at a mass-to-charge ratio of 2.

It is preferable that the peeling in the fourth step be performed while water or an aqueous solution is made to penetrate between the peeling layer and the layer to be peeled.

Another embodiment of the present invention is a semiconductor device including a bonding layer over a flexible substrate; an oxide layer containing tungsten oxide over the bonding layer; a first layer containing silicon oxynitride over the oxide layer; a second layer containing silicon nitride over the first layer; and a transistor over the second layer. The oxide layer includes a region in which the nitrogen content measured by SIMS is higher than that of the first layer and a region in which the hydrogen content measured by SIMS is higher than that of the first layer.

In the above-described semiconductor device, the concentrations of nitrogen and hydrogen in the first layer, which are measured by SIMS, preferably decrease from the second layer side to the oxide layer side.

According to the present invention, a peeling method with improved peelability can be provided. The yield in a peeling step can also be increased. The yield in manufacturing a flexible device can also be increased. A highly reliable semiconductor device can also be provided. A highly reliable semiconductor device provided with a flexible substrate can also be provided.

