Letter 1
300 mm Wafer-Scale SiN Platform for Broadband Soliton
Microcombs Compatible with Alkali Atomic References
SHAO-CHIEN OU
1,2
, ALIN O. ANTOHE
3
, LEWIS G. CARPENTER
3
, GREGORY MOILLE
1,2
, AND KARTIK
SRINIVASAN
1,2,*
1
Joint Quantum Institute, NIST/University of Maryland, College Park, USA
2
Microsystems and Nanotechnology Division, National Institute of Standards and Technology, Gaithersburg, USA
3
American Institute of Manufacturing Integrated Photonics (AIM Photonics), Research Foundation SUNY, Albany, NY, USA
*
Corresponding author: kartik.srinivasan@nist.gov
2025-09-07
Chip-integrated optical frequency combs (OFCs) based
on Kerr nonlinear resonators are of great significance
given their scalability and wide range of applications.
Broadband on-chip OFCs reaching visible wavelengths
are especially valuable as they address atomic clock tran-
sitions that play an important role in position, naviga-
tion, and timing infrastructure. Silicon nitride (SiN)
deposited via low pressure chemical vapor deposition
(LPCVD) is the usual platform for chip-integrated OFCs,
due to its low absorption and repeatable dispersion, and
such fabrication is now standard at wafer sizes up to
200
mm
. However, the LPCVD high temperature and
film stress poses challenges in scaling to larger wafers
and integrating with electronic and photonic devices.
Here, we report the linear performance and broadband
frequency comb generation from microring resonators
fabricated on 300 mm wafers at AIM Photonics, us-
ing a lower temperature, lower stress plasma enhanced
chemical vapor deposition process suitable for thick
(
≈
700
nm
) SiN films and compatible with electronic
and photonic integration. The platform exhibits con-
sistent insertion loss, high intrinsic quality factor, and
thickness variation of
±
2
%
across the whole 300
mm
wafer. We demonstrate broadband soliton microcomb
generation with a lithographically tunable dispersion
profile extending to wavelengths of common alkali atom
transitions. These results are a step towards more highly
integrated and mass-manufacturable devices, enabling
advanced applications including optical clocks, LiDAR,
and beyond. © 2025 Optica Publishing Group
1
OCIS codes: (140.3498) Microcavity devices; (190.4390) Nonlinear optics,
integrated optics; (190.3270) Kerr effect
2
http://dx.doi.org/10.1364/ao.XX.XXXXXX
3
4
5
Optical frequency combs (OFCs) play a crucial role in diverse
6
fields owing to their evenly spaced spectral lines, broadband
7
coverage, and tunability [
1
]. Chip-scale integration is crucial
8
for real-world deployment, in creating compact, efficient, and
9
scalable metrology systems such as optical atomic clocks [
2
],
10
spectrometers [
3
], among others [
4
,
5
]. A promising approach to
11
realizing on-chip low-noise OFCs involves periodically extract-
12
ing a dissipative Kerr soliton (DKS) circulating within a micror-
13
ing resonator [
6
]. Silicon nitride (SiN) has emerged as a material
14
of choice for such microrings due to its combination of low linear
15
loss [
7
], high refractive index [
8
], broad optical transparency [
9
],
16
and strong Kerr effect [
10
]. SiN can also be integrated into con-
17
ventional microelectronic and photonic fabrication workflows,
18
allowing direct incorporation with high-frequency electronic
19
systems [11] and active photonic devices [12].20
There have been many demonstrations of SiN microcomb
21
fabrication on 100
mm
[
13
], 150
mm
[
14
], 200
mm
[
15
] platforms.
22
However, significant challenges remain in scaling such results to
23
a 300
mm
foundry process, primarily due to the large film stress
24
(typically 0.8 GPa to 1 GPa) and high temperature (
≈
800
◦
C) as-
25
sociated with the growth of thick stoichiometric (Si
3
N
4
) films by
26
low pressure chemical vapor deposition (LPCVD) [
16
], the stan-
27
dard approach for SiN DKS OFCs. Despite recent progress with
28
300
mm
LPCVD-fabricated chips [
17
,
18
], improvements in yield
29
and dispersion engineering are needed to take full advantage of
30
the 300
mm
scale fabrication. One potential approach is to inves-
31
tigate modified LPCVD deposition conditions, which have been
32
studied in both the stoichiometric [
19
] and non-stoichiometric
33
regimes [
8
], though a comprehensive process remains elusive.
34
On the other hand, plasma enhanced chemical vapor deposition
35
(PECVD) [
16
,
20
,
21
] and reactive sputtering [
22
,
23
] present al-
36
ternative solutions, but thus far research has primarily focused
37
on telecommunications-band applications and has yet to expand
38
to larger manufacturing-scale processes.39
In this Letter, we demonstrate broadband DKS microcomb
40
generation in a thick (
≈
700
nm
)
SiN
platform based on 300
mm41
wafer-scale fabrication at AIM Photonics [Fig. 1a]. The PECVD
42
SiN
film is grown at
<
500
◦
C on a 5
µm SiO
2
layer produced
43
by thermal oxidation of the silicon wafer, and from wafer deflec-
44
tion measurements, exhibits
≈
280 MPa of mean compressive
45
stress. After patterning of the SiN layer, it is clad with 5
µm
of
46
CVD
SiO
2
, and a total of sixty-four reticle fields are harvested
47
from the 300 mm wafer. Each reticle field measures 26
mm ×48
