TECHNICAL FIELD

The disclosure relates to improved photoresist dry film layers and in particular to photoresist dry film layers having improved formulations for making thick film laminates.

BACKGROUND AND SUMMARY

Photoresist dry film layers are useful for a wide variety of electronic devices, including but not limited to, fluid jet ejection devices, vaporization devices, and micro-electronic structures. Fluid jet ejection devices include fluidic ejection heads that are useful for ejecting a variety of fluids including inks, cooling fluids, pharmaceuticals, lubricants, vaporizing fluids, and the like. Devices that use fluidic ejection heads continue to be improved as the technology for making the fluidic ejection heads continues to advance. New techniques are constantly being developed to provide low cost, highly reliable fluidic ejection heads for fluid ejection devices for a wide variety of applications.

Fluidic ejection heads used in fluid jet ejection devices have a relatively complicated structure that includes electrical circuits, fluid passageways and a variety of tiny parts assembled with precision to provide a powerful, yet versatile fluidic ejection head. The components of the fluidic ejection head must cooperate with each other and with a variety of fluid formulations to provide the desired characteristics for ejecting fluid therefrom. Accordingly, it is important to match the ejection head components to the fluid and the duty cycle demanded by the fluid ejection device using the fluidic ejection head. Slight variations in production quality can have a tremendous influence on the product yield and resulting fluid ejection performance.

During the fabrication of a fluidic ejection head, photoimageable materials may be used to provide a fluid flow layer and/or a nozzle plate layer. In the preparation of a photoimageable material, a photoresist resin formulation is applied as a liquid to a release film and the formulation is dried on the release film. The release film is then removed from the dry photoimageable material and the dry photoimageable material is laminated to a silicon semiconductor substrate or to a flow feature layer on the silicon semiconductor substrate. The photoimageable material is then imaged and developed to provide a variety of fluid flow features and/or nozzle holes. In some cases, a fluid flow layer containing fluid ejection chambers and fluid flow channels is applied directly to a silicon semiconductor substrate as a spin coated layer and a nozzle plate layer is laminated as a dry film to the fluid flow layer, in other cases, the fluid flow layer is laminated as a dry film to the silicon semiconductor substrate and a nozzle plate is laminated as a dry film to the fluid flow layer.

Due to the different chemical and physical properties of the silicon substrate and fluid flow layer, suitable adhesion of the fluid flow layer to the silicon substrate cannot be achieved without the use of surface treatment of the silicon substrate and/or the use of an adhesion enhancer in the fluid flow layer. Likewise, adhesion between the nozzle plate and the fluid flow layer is important and requires the use of an adhesion enhancer in the formulation for the dry film photoresist material used to make the nozzle plate layer. However, it was discovered that a considerable amount of adhesion enhancer is lost during the step of drying photoresist formulations on the release film. Loss of the adhesion enhancer during the drying step has led to poorer adhesion between the fluid flow layer and the substrate and/or between the fluid flow layer and the nozzle plate layer. Accordingly, what is needed is an improved dry film photoresist formulation that does not suffer from significant loss of the adhesion enhancer during the photoresist formulation drying step.

In view of the foregoing, exemplary embodiments of the disclosure provide an improved photoimageable dry film formulation, a fluidic ejection head containing a thick film layer derived from the improved photoimageable dry film formulation, and a method for making a fluidic ejection head. The improved photoimageable dry film formulation includes a multifunctional epoxy compound, a photoinitiator capable of generating a cation, a non-photoreactive solvent, and from about 0.5 to about 5% by weight a silane oligomer adhesion enhancer based on a total weight of the photoimageable dry film formulation before drying.

In another embodiment, there is provided a method for making an improved fluidic ejection head. The method includes applying a photoresist layer to a release film, wherein the photoresist layer is derived from a photoimageable dry film formulation comprising a multi-functional epoxy compound, a photoacid generator, a silane oligomer adhesion enhancer, and an aryl ketone solvent. The photoimageable dry film formulation on the release film layer is dried to provide a thick film layer. The thick film layer is laminated to a flow feature layer on a semiconductor substrate. Then the release film is removed from the thick film layer. Nozzle holes are imaged in the thick film layer and the imaged thick film layer is developed to provide a nozzle plate for the fluidic ejection head.

A further embodiment provides a fluidic ejection head for ejecting a fluid composition. The fluidic ejection head includes a semiconductor substrate containing fluid ejection devices thereon, A flow feature layer disposed on the semiconductor substrate, and a thick film layer is laminated to the flow feature layer. The thick film layer is derived from a photoimageable dry film formulation comprising a multifunctional epoxy compound, a photoinitiator capable of generating a cation, a non-photoreactive solvent, and from about 0.5 to about 5% by weight a silane oligomer adhesion enhancer based on a total weight of the photoimageable dry film formulation before drying.

In some embodiments, the photoimageable dry film formulation includes from about 1 to about 3 wt. % of the silane oligomer adhesion enhancer based on a total weight of the photoimageable dry film formulation before drying.

In some embodiments, the photoimageable dry film formulation includes an aliphatic ketone solvent. In other embodiments, the aliphatic ketone solvent includes cyclohexanone, and optionally, acetone.

In some embodiments, the silane oligomer adhesion enhancer is an alkoxysilane oligomer compound. In other embodiments, the alkoxysilane oligomer compound is a gamma-glycidoxypropyltrimethoxysilane oligomer of the formula


wherein n ranges from 1 to 4.

In some embodiments, the photoimageable dry film formulation on the release film is dried at a temperature ranging from about 110° to about 150° C.

In some embodiments, a dry film laminate made from the photoimageable dry film formulation is applied to a silicon semiconductor substrate.

In other embodiments, a dry film laminate made from the photoimageable dry film formulation is applied to a flow feature layer of a fluidic ejection head.

An advantage of the embodiments described herein is that the dry film photoimageable layer has improved adhesion between the semiconductor substrate and fluid flow layer and between the fluid flow layer and the nozzle plate compared to dry film photoimageable layers made with conventional adhesion enhancers.

