Halftone phase shift photomask blank, making method, and halftone phase shift photomask

Patent metadata

Field	Value
Publication number	US-10859904-B2
Application number	US-202016854400-A
Country	US
Kind code	B2
Filing date	Apr 21, 2020
Priority date	Sep 28, 2016
Publication date	Dec 8, 2020
Grant date	Dec 8, 2020

Abstract

During reactive sputtering using a silicon-containing target, an inert gas, and a nitrogen-containing reactive gas, a hysteresis curve is drawn by sweeping the flow rate of the reactive gas, and plotting the sputtering voltage or current during the sweep versus the flow rate of the reactive gas. In the step of sputtering in a region corresponding to a range from more than the lower limit of reactive gas flow rate providing the hysteresis to less than the upper limit, the target power, the inert gas flow rate and/or the reactive gas flow rate is increased or decreased continuously or stepwise. The halftone phase shift film including a layer containing transition metal, silicon and nitrogen is improved in in-plane uniformity of optical properties.

First claim

The invention claimed is:

1. A method for preparing a halftone phase shift photomask blank having a halftone phase shift film on a transparent substrate, the method comprising the step of depositing a layer containing a transition metal, silicon and nitrogen on the transparent substrate, as a part or the entirety of the halftone phase shift film, by reactive sputtering using one or more silicon-containing targets, an inert gas, and a nitrogen-containing reactive gas, wherein
provided that a hysteresis curve is drawn by applying a power across the one or more silicon-containing targets, feeding the reactive gas into a chamber, increasing and then decreasing the flow rate of the reactive gas for thereby sweeping the flow rate of the reactive gas, measuring a sputtering voltage or current value across any one target upon sweeping of the flow rate of the reactive gas, and plotting the sputtering voltage or current value versus the flow rate of the reactive gas,
the step of depositing a layer containing a transition metal, silicon and nitrogen includes a transition mode sputtering step of sputtering in a region corresponding to a range from more than the lower limit of reactive gas flow rate providing the hysteresis to less than the upper limit, and in a part or the entirety of the transition mode sputtering step, at least one parameter selected from the power applied across the target, the flow rate of the inert gas, and the flow rate of the reactive gas is increased or decreased continuously or stepwise.

2. The method of claim 1 wherein the hysteresis curve is drawn by measuring a sputtering voltage or current value across the target having the highest silicon content among the one or more silicon-containing targets.

3. The method of claim 1 wherein the one or more silicon-containing targets are selected from targets containing silicon, but not a transition metal and targets containing a transition metal and silicon.

4. The method of claim 1 wherein a target containing silicon and a target containing a transition metal, but not silicon are used.

5. The method of claim 1 wherein in the transition mode sputtering step, sputtering is carried out while at least one parameter selected from the power applied across the target, the flow rate of the inert gas, and the flow rate of the reactive gas is increased or decreased continuously such that the layer containing transition metal, silicon and nitrogen may be compositionally graded in thickness direction.

6. The method of claim 1 wherein in the entirety of the transition mode sputtering step, sputtering is carried out while at least one parameter selected from the power applied across the target, the flow rate of the inert gas, and the flow rate of the reactive gas is increased or decreased continuously.

7. The method of claim 1 wherein in the transition mode sputtering step, sputtering is carried out while the flow rate of the reactive gas is increased or decreased.

8. The method of claim 1 wherein the step of depositing a layer containing a transition metal, silicon and nitrogen includes a reaction mode sputtering step of sputtering in a region corresponding to a range equal to or more than the upper limit of reactive gas flow rate providing the hysteresis, and
the transition mode sputtering step is followed by the reaction mode sputtering step, or the reaction mode sputtering step is followed by the transition mode sputtering step.

9. The method of claim 8 wherein in a part or the entirety of the reaction mode sputtering step, sputtering is carried out while at least one parameter selected from the power applied across the target, the flow rate of the inert gas, and the flow rate of the reactive gas is increased or decreased continuously or stepwise.

10. The method of claim 8 wherein from the transition mode sputtering step to the reaction mode sputtering step, or from the reaction mode sputtering step to the transition mode sputtering step, sputtering is carried out while at least one parameter selected from the power applied across the target, the flow rate of the inert gas, and the flow rate of the reactive gas is increased or decreased continuously.

11. The method of claim 1 wherein the step of depositing a layer containing a transition metal, silicon and nitrogen includes a metal mode sputtering step of sputtering in a region corresponding to a range equal to or less than the lower limit of reactive gas flow rate providing the hysteresis, and
the metal mode sputtering step is followed by the transition mode sputtering step, or the transition mode sputtering step is followed by the metal mode sputtering step.

12. The method of claim 11 wherein in a part or the entirety of the metal mode sputtering step, sputtering is carried out while at least one parameter selected from the power applied across the target, the flow rate of the inert gas, and the flow rate of the reactive gas is increased or decreased continuously or stepwise.

13. The method of claim 11 wherein from the metal mode sputtering step to the transition mode sputtering step, or from the transition mode sputtering step to the metal mode sputtering step, sputtering is carried out while at least one parameter selected from the power applied across the target, the flow rate of the inert gas, and the flow rate of the reactive gas is increased or decreased continuously.

14. The method of claim 1 wherein the inert gas is argon gas.

15. The method of claim 1 wherein the reactive gas is nitrogen gas.

16. The method of claim 1 wherein the layer containing a transition metal, silicon and nitrogen consists of a transition metal, silicon and nitrogen.

17. The method of claim 1 wherein the transition metal is molybdenum.

Assignees

• Shinetsu Chemical Co

Inventors

• Kosaka Takuro
• Inazuki Yukio
• Kaneko Hideo

Classifications

• H10P76/2041

  Photolithographic processes · CPC title

• G03F9/7057

  Gas flow, e.g. for focusing, leveling or gap setting · CPC title

• G03F1/66

  Containers specially adapted for masks, mask blanks or pellicles; Preparation thereof · CPC title

• G03F1/32 Primary

  Attenuating PSM [att-PSM], e.g. halftone PSM or PSM having semi-transparent phase shift portion,; Preparation thereof · CPC title

• G03F1/26

  Phase shift masks [PSM]; PSM blanks; Preparation thereof · CPC title