Etching with improved control of critical feature dimensions at the bottom of thick layers

A method for etching a feature in an etch layer, the method comprising:

• providing a substrate layer;
• fabricating a mask feature from a mask layer material, the mask feature being fabricated at a lateral feature position on the substrate layer, the mask feature having a critical lateral extension, wherein fabricating the mask feature comprises fabricating a mask opening in a mask layer on the substrate layer at the lateral feature position and with the critical lateral extension;
• depositing an etch layer from an etch layer material on the mask feature and on the substrate layer, the etch layer being deposited to a thickness of more than 2 micrometers from an initial contact face, the etch layer material being selectively etchable relative to the mask layer material;
• and
• etching a feature in the etch layer at a first lateral position with a lateral extension larger than the critical lateral extension, the etching using an etchant that selectively removes the etch layer material relative to the mask layer material;
• wherein fabricating the mask feature comprises fabricating a sacrificial etch-stop cap from an etch-stop material in the mask opening, the etch-stop material being selectively etchable relative to the mask layer material and the etch layer material;
• wherein the etch layer material is additionally selectively etchable relative to the etch-stop material;
• and
• wherein etching the feature in the etch layer comprises performing a first selective etching step during which the etch layer is removed selectively relative to the etch-stop cap, and performing a second selective etching step during which the etch-stop cap is removed selectively relative to the etch layer and to the mask layer.

A method for etching a feature in an etch layer, the method comprising:

• providing a substrate layer;
• fabricating a mask feature from a mask layer material, the mask feature being fabricated at a lateral feature position on the substrate layer, the mask feature having a critical lateral extension;
• depositing an etch layer from an etch layer material on the mask feature and on the substrate layer, the etch layer being deposited to a thickness of more than 2 micrometers from an initial contact face, the etch layer material being selectively etchable relative to the mask layer material;
• and
• etching a feature in the etch layer at a first lateral position with a lateral extension larger than the critical lateral extension, the etching using an etchant that selectively removes the etch layer material relative to the mask layer material;
• wherein fabricating the mask feature comprises removing those mask layer sections that are arranged outside the critical lateral extension at the lateral feature position;
• and
• wherein etching the feature in the etch layer comprises performing a first selective etching step during which the etch layer is removed selectively relative to the mask feature and performing a second selective etching step during which the mask feature is removed selectively relative to the etch layer.

A method for etching a feature in an etch layer, the method comprising:

• providing a substrate layer;
• fabricating a mask feature from a mask layer material, the mask feature being fabricated at a lateral feature position on the substrate layer, the mask feature having a critical lateral extension;
• depositing an etch layer from an etch layer material on the mask feature and on the substrate layer, the etch layer being deposited to a thickness of more than 2 micrometers from an initial contact face, the etch layer material being selectively etchable relative to the mask layer material;
• etching a feature in the etch layer at a first lateral position with a lateral extension larger than the critical lateral extension, the etching using an etchant that selectively removes the etch layer material relative to the mask layer material;
• and
• removing the substrate layer relative to the etch layer after etching the feature in the etch layer.