Titanium Sputtering Target Grain Control via Knead Forging
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Solution Overview
Problem
Conventional titanium targets used for sputtering struggle with maintaining a dense, columnar crystal structure and uniformity, leading to issues with electromigration resistance and sputtering film uniformity, especially as semiconductor elements require smaller crystal grain sizes and randomized crystal orientations to enhance performance.
Innovation Solution
A manufacturing method involving multiple knead forging and heat treatment processes to produce a titanium sputtering target with a purity of 99.99% or more, achieving a crystal grain size of 15 μm or less and random crystal orientation, which suppresses ghost grains and maintains stability and uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the titanium target is made large in size to match large silicon wafers, then the sputtering area is increased, but the controllability of crystal grain size and orientation becomes difficult
Solution Approach 1:
The patent divides the large titanium target into multiple smaller targets arranged in an array. Each small target maintains controlled crystal grain structure and orientation, while collectively they provide the necessary large sputtering area. This segmentation allows precise control of crystal properties in each unit without the difficulties associated with manufacturing large single-piece targets.
Solution Approach 2:
The patent changes the size parameter of individual targets from large to small, while compensating by increasing the number of targets. This parameter transformation enables maintaining crystal grain size control and orientation precision while achieving the required total sputtering area through multiple controlled units rather than one large uncontrolled target.
2Strength
If the titanium target thickness is increased to 8 mm or more to match large silicon wafers, then the mechanical strength is improved, but the uniformity of sputtering film becomes difficult to control
Solution Approach 1:
The patent segments the thick target structure into multiple thinner targets arranged in an array. Each thin target maintains uniform crystal orientation and grain size, ensuring uniform sputtering film deposition. The collective array provides the necessary mechanical strength while individual targets maintain the precision required for uniform film control, avoiding the uniformity problems of thick single-piece targets.
3Device complexity
If conventional sputtering targets are used without specialized manufacturing processes, then the manufacturing complexity is reduced, but the electromigration resistance and film uniformity deteriorate
Solution Approach 1:
The patent applies preliminary cold forging and heat treatment processes to each titanium target before assembly. These preliminary actions create the desired columnar crystal structure with controlled grain size and random orientation, which are essential for electromigration resistance. By performing these actions in advance on each unit target, the complex manufacturing is distributed across multiple simple, controlled operations rather than one complex process.
4Manufacturing precision
If the crystal grain size is reduced to enhance sputtering film quality, then the film uniformity is improved, but the manufacturing precision requirements become more stringent
Solution Approach 1:
The patent segments the manufacturing into multiple independent unit targets, each undergoing controlled cold forging and heat treatment to achieve fine crystal grain structure. This segmentation allows stringent precision requirements to be met in each small unit through controlled processes, rather than attempting to control grain size across a large single target where precision control becomes difficult.
Solution Approach 2:
The patent changes the approach from attempting to control crystal grain size in a single large target to controlling grain size in multiple small targets. This parameter transformation enables achieving fine crystal grains (15 μm or less) with random orientation and uniform structure, as each small target can be precisely controlled through standardized cold forging and heat treatment processes.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method results in a sputtering target with improved electromigration resistance and uniform deposition, suitable for producing high-reliability titanium nitride films for semiconductor elements, maintaining performance even in large targets and over extended sputtering times.
Implementation Method 1
one set is cold forging processes in directions parallel to and perpendicular to a thickness direction of the titanium material
Implementation Method 2
a first heat treatment process in which the titanium material passing through the first knead forging process is heated to a temperature of 700° C. or more to induce recrystallization
Implementation Method 3
heated to a temperature of 700° C. or more to induce recrystallization
Implementation Method 4
a cold rolling process in which cold rolling is performed for the titanium material passing through the second knead forging process
Implementation Method 5
a second heat treatment process in which the titanium material passing through the cold rolling process is heated to a temperature of 300° C. or more to perform a heat treatment
Implementation Method 6
The TiN film is obtained by sputtering a sputtering target made up of, for example, high-purity Ti in a nitrogen atmosphere
Data Source
AI summary
According to an embodiment, two or more sets of knead forging are performed where one set is cold forging processes in directions parallel to and perpendicular to a thickness direction of a columnar titanium material. The titanium material is heated to a temperature of 700° C. or more to induce recrystallization, and thereafter, two or more sets of knead forging are performed where one set is the cold forging processes in the directions parallel to and perpendicular to the thickness direction. Further, the titanium material is cold rolled, and is heat-treated to a temperature of 300° C. or more.