GB1569664A - Etching of grooves in substrates for use in cups devices - Google Patents

Description

(54) IMPROVEMENTS IN OR RELATING TO THE ETCHING OF GROOVES IN SUBSTRATES FOR USE IN SAW DEVICES (71) We, THE GENERAL ELECTRIC COMPANY LIMITED, of 1 Stanhope Gate, London, WIA 1EH, a British Company, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to the etching of grooves in substrates for use in surface acoustic wave devices and more particularly to the etching of grooves by ion bombardment through a mask.

Two ion bombardment techniques which are known for etching a suitably masked substrate with ions are: radio-frequency sputter etching, in which the substrate is bombarded with positively charged ions; and ion beam etching, in which the substrate is bombarded with neutralised ions.

Typically the ions used for bombardment are argon ions.

It is known to use titanium as the masking material in the etching of silicon substrates for use in semiconductor devices.

The present invention provides a method of ion etching a desired groove pattern in a substrate of material suitable for use in a surface acoustic wave device, the method comprising the steps of: forming on the surface of the substrate to be etched a titanium mask exposing the surface in said desired pattern; ion etching the substrate surface exposed by said mask; and removing said mask.

One method according to the invention of ion etching a desired groove pattern in a quartz substrate will now be described, by way of example only, with reference to the accompanying drawings which show the substrate at various stages of the method.

A rectangular quartz substrate 1 has a layer of titanium 2 sputter deposited on its upper surface (Figure 1). The layer 2 of titanium is then photolithographically formed into a mask 3 of a desired pattern (Figure 2).

The quartz substrate 1 and its mask 3 are then subjected to bombardment from above with a flux of positive argon ions.

In this way, both the titanium mask 3 and the surface of the quartz substrate 1 exposed thereby are etched away, thus slightly decreasing the thickness of the titanium mask 3 and imparting the desired groove pattern into the quartz substrate (Figure 3).

Finally the titanium mask 3 is chemically removed, leaving the quartz substrate 1 with the desired groove pattern in its upper surface (Figure 4).

It will be appreciated that any ion etching technique may be used to impart the desired groove pattern into the substrate.

It will also be appreciated that the invention is also applicable to other material suitable for use in surface acoustic wave devices, e.g. lithium niobate, lithium tantalate, etc.

WHAT WE CLAIM IS:- 1. A method of ion etching a desired groove pattern in a substrate of material suitable for use in a surface acoustic wave device, the method comprising the steps of: forming on the surface of the substrate to be etched a titanium mask exposing the surface in said desired pattern; ion etching the substrate surface exposed by said mask; and removing said mask.

2. A method according to Claim 1 wherein the step of forming said titanium mask comprises sputter depositing a layer of titanium on the surface of the substrate to be etched, and photolithographically forming said mask from said layer to expose the surface in said desired pattern; and the step of ion etching the substrate surface comprises ion etching the substrate exposed by said mask with positive argon ions.

3. A method of ion etching a desired groove pattern in a substrate of material suitable for use in a surface acoustic wave device substantially as hereinbefore described with reference to the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (4)

**WARNING** start of CLMS field may overlap end of DESC **. (54) IMPROVEMENTS IN OR RELATING TO THE ETCHING OF GROOVES IN SUBSTRATES FOR USE IN SAW DEVICES (71) We, THE GENERAL ELECTRIC COMPANY LIMITED, of 1 Stanhope Gate, London, WIA 1EH, a British Company, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to the etching of grooves in substrates for use in surface acoustic wave devices and more particularly to the etching of grooves by ion bombardment through a mask. Two ion bombardment techniques which are known for etching a suitably masked substrate with ions are: radio-frequency sputter etching, in which the substrate is bombarded with positively charged ions; and ion beam etching, in which the substrate is bombarded with neutralised ions. Typically the ions used for bombardment are argon ions. It is known to use titanium as the masking material in the etching of silicon substrates for use in semiconductor devices. The present invention provides a method of ion etching a desired groove pattern in a substrate of material suitable for use in a surface acoustic wave device, the method comprising the steps of: forming on the surface of the substrate to be etched a titanium mask exposing the surface in said desired pattern; ion etching the substrate surface exposed by said mask; and removing said mask. One method according to the invention of ion etching a desired groove pattern in a quartz substrate will now be described, by way of example only, with reference to the accompanying drawings which show the substrate at various stages of the method. A rectangular quartz substrate 1 has a layer of titanium 2 sputter deposited on its upper surface (Figure 1). The layer 2 of titanium is then photolithographically formed into a mask 3 of a desired pattern (Figure 2). The quartz substrate 1 and its mask 3 are then subjected to bombardment from above with a flux of positive argon ions. In this way, both the titanium mask 3 and the surface of the quartz substrate 1 exposed thereby are etched away, thus slightly decreasing the thickness of the titanium mask 3 and imparting the desired groove pattern into the quartz substrate (Figure 3). Finally the titanium mask 3 is chemically removed, leaving the quartz substrate 1 with the desired groove pattern in its upper surface (Figure 4). It will be appreciated that any ion etching technique may be used to impart the desired groove pattern into the substrate. It will also be appreciated that the invention is also applicable to other material suitable for use in surface acoustic wave devices, e.g. lithium niobate, lithium tantalate, etc. WHAT WE CLAIM IS:-

1. A method of ion etching a desired groove pattern in a substrate of material suitable for use in a surface acoustic wave device, the method comprising the steps of: forming on the surface of the substrate to be etched a titanium mask exposing the surface in said desired pattern; ion etching the substrate surface exposed by said mask; and removing said mask.

2. A method according to Claim 1 wherein the step of forming said titanium mask comprises sputter depositing a layer of titanium on the surface of the substrate to be etched, and photolithographically forming said mask from said layer to expose the surface in said desired pattern; and the step of ion etching the substrate surface comprises ion etching the substrate exposed by said mask with positive argon ions.

3. A method of ion etching a desired groove pattern in a substrate of material suitable for use in a surface acoustic wave device substantially as hereinbefore described with reference to the accompanying drawings.

4. A surface acoustic wave device in orporating a substrate having therein a groove pattern etched by a method according to Claims 1, 2 or 3.