SOD vs. CVD Battle Continues

Electronic News, June 4, 2001 by Jeff Chappell

The focus of the low-k film competition may be shifting from which approach can deliver the lowest k value to which approach is the cheapest and most technically feasible.

Marlborough, Mass.-based Shipley Company LLC last week entered the low-k fray with Zirkon, a spin-on dielectric (SOD) film with a controlled k value ranging from 2.6 to below 2.0, the company said.

The Zirkon LK series of SOD films utilize proprietary chemistry to form pores with a dielectric polymer, Nanogen. The Nanogen polymer is engineered to precisely define pore sizes of less than 5 nanometers, according to Shipley, a subsidiary of specialty chemicals company Rohm and Hans Co., Philadelphia.

Trikon Technologies Inc. last week also made a low-k film announcement, introducing Orion, an organosilicate family of low-k dielectric films geared for sub-0.10-micron copper damascene processes. Newport, Wales-based Trikon (nasdaq: TRKN) first developed Orion with a k value of 2.8 and, along with its industry partners, integrated it into 0.13-micron dual-damascene copper devices, later extending it to a k value of 2.5, said Andy Noakes, Trikon's CVD products marketing manager. The company has demonstrated k values between 2.2 and 2.0 with Orion in the lab at International Sematech, he said.

"We have met our goal and achieved the low-k values of the best spin-on processes with a CVD material that integrates with existing etch, strip and CMP equipment sets," said Nigel Wheeler, Trikon's chief executive officer, in a statement.

Therein lies the seemingly new battleground, as opposed to which type of film can achieve the lowest k value. CVD proponents maintain that they can provide more k value for the buck.

Typically, integrating spin-on films requires more layers, and hence more process steps, than CVD films. Some SOD integration techniques require two hardmask layers, which require the use of CVD tools and steps in addition to spin-coaters. Then the SOD needs to be cured, adding an additional step and tool, while films such as Applied Materials Inc.'s CVD barrier films do not.

"Some of our customers thought that cost of ownership of spin-on came primarily from the chemical itself and not (from) a capital outlay standpoint," said Meggie Gotuaco, Applied's CVD low-k film global product manager. "It is really a combination of both."

Taking an SOD approach can cost up to three times as much as CVD, according to Santa Clara, Calif.-based Applied (nasdaq: AMAT).

"The question to ask is, 'Is that the only way to accomplish what we are trying to do?,' and the answer is, 'No,'" said Ralph Butler, referring to the dual-hardmask technique. Butler is product-marketing manager for advanced low-k materials for Tokyo Electron America, the U.S. subsidiary of Tokyo Electron. Butler further noted that in some cases, curing of the SOD film can be done on the spin-coater tool and not in a separate furnace.

"If there were a large disparity in cost, with no benefit of performance, no one would choose SOD ... so there are people that know how to make the cost numbers work for them," Butler said. "We have ways to compete on a cost basis with the CVD materials."

One thing both sides can agree on is that the low-k integration issue is far from settled for either camp, and while cost may be a factor, extending the low-k values--where SOD films still have an advantage--is still at the heart of the debate.

                         2000 ITRS Interconnect
                        Technology Requirements
Yr. of first production shipment    2001     2002     2003     2004
Technology node                    130 mm
No. of metal levels-logic             7       7-8       8        8
Interlevel metal Insulator-
[k.sub.eff]                        2.9-3.5  2.9-3.5  2.2-2.9  2.2-2.9
Interlevel metal Insulator-bulk k    2.7      2.7      2.0      2.0
Barrier/cladding thickness (nm)      14       13       12       11
Effective conductor resistivity-
logic ([micro]W-cm)                  2.2      2.2      2.2      2.2
No. of metal levels-DRAM              3       3-4       4        4
Effective conductor resistivity-
DRAM ([micro]W-cm)                   3.3      3.3      3.3      3.3
Interlevel metal Insulator-DRAM
[k.sub.eff]                          4.1    3.0-4.1  3.0-4.1  3.0-4.1
Yr. of first production shipment    2005     2008         2011
Technology node                    100 mm    70 mm       50 mm
No. of metal levels-logic            8-9       9          9-10
Interlevel metal Insulator-
[k.sub.eff]                        1.6-2.2    1.6    [less than]1.6
Interlevel metal Insulator-bulk k    1.3      1.3    [less than]1.3
Barrier/cladding thickness (nm)      10        7           5
Effective conductor resistivity-
logic ([micro]W-cm)                  2.2      2.2    [less than]1.8
No. of metal levels-DRAM              4        4           4
Effective conductor resistivity-
DRAM ([micro]W-cm)                   2.2      2.2         2.2
Interlevel metal Insulator-DRAM
[k.sub.eff]                        2.5-3.0  2.5-3.0     2.0-2.5
Yr. of first production shipment        2014
Technology node                        35 mm
No. of metal levels-logic                10
Interlevel metal Insulator-
[k.sub.eff]                        [less than]1.3
Interlevel metal Insulator-bulk k       1.1
Barrier/cladding thickness (nm)          4
Effective conductor resistivity-
logic ([micro]W-cm)                [less than]1.8
No. of metal levels-DRAM                 4
Effective conductor resistivity-
DRAM ([micro]W-cm)                      2.2
Interlevel metal Insulator-DRAM
[k.sub.eff]                           2.0-2.3
Solutions Exist
Solutions being pursued
No known solutions
SOURCE: SEMATECH