PECVD Processes for Compound Semiconductor Devices
This SPTS' PECVD processes for deposition of SiN onto GaN and GaAs in RF, power, and photonic applications.Download
High quality dielectric films are needed for a range of applications in the manufacture of compound semiconductor (CS) devices including metal-insulator-metal (MIM) capacitor, device and final passivation layers, and bow compensation. Plasma enhanced chemical vapor deposition (PECVD) SiN is widely used because of its excellent passivation performance, stress tuneability and electrical reliability together with its compatibility with GaAs, GaN and SiC based RF and power devices.
In the past 5 years, SPTS has experienced more than 40% growth in PECVD sales into CS applications which includes deposition of dielectric films for:
In contrast to Si-based devices, CS devices are still manufactured on smaller wafers and our PECVD processes are available for wafer sizes ranging from 3” to 200mm.
Most compound semiconductors do not have stable native oxide layers, such as SiO2, and oxygen is also a dopant for many compound semiconductors. Hence, PECVD SiN is typically used as a first passivation layer. There are some applications for SiO films deposited by SiH4 or TEOS, for passivation of inter-level metal and wafer level packaging of CS devices, but SiN is more commonly used. SiN has excellent passivation properties, suitable for use as a barrier against electrical current, moisture and metal diffusion.
PECVD SiN process and film properties can be optimized & tuned:
Ultra-Low Power PECVD of SiN for GaN
GaN is highly sensitive to surface plasma damage which can lead to increased transistor leakage currents. Therefore, it is necessary to use a low power density RF when depositing SiN onto GaN using PECVD. The high frequency RF generator and control system of SPTS’s Delta™ APM module has been optimized to allow ultra-low (~0.01W/cm2) power density during SiN film deposition with high accuracy, repeatability and plasma stability. The same hardware can still run standard high-power processes.
Fig 1 Repeatability of SiN passivation film deposited at low power (0.01W.cm-2)
MIM Capacitor Dielectric for GaAs RF-IC
SPTS has many years of experience in high volume manufacturing of dielectric layers for MIM (metal- insulator-metal) capacitors. Deposited at 250°C – 300°C, SiN film thicknesses are typically 50nm – 100nm. Thickness uniformity is critical as this directly determines capacitance uniformity, and the APM module can give film uniformities of ~1% WIW. In volume production it is essential that this performance is reliable over time. The graphs below show the thickness uniformity of 1000Å SiN films maintained throughout multiple PM cycles over a 4-month period in volume production.
Fig 2 Average thickness for 1000 Å SiN films over 4 months, in production
Fig 3 WIW Thickness Range for 1000 Å SiN films over 4 months in production
The electrical performance and long-term reliability of the dielectric films is also very important, and SPTS’s SiN films have a proven performance with voltage breakdown ~ 10MV.cm-1 and resistance to time dependent dielectric breakdown (TDDB).
Anti-Reflective Coating for GaAs-based VCSELs
Fig 4 Schematic diagram of VCSEL structure with anti-reflective coating on the back side of the GaAs substrate
SiN can also be used as an anti-reflective coating which improves the efficiency of VCSELs. Control of thickness and refractive index are paramount for best optical performance. SiN can also be useful as a stress compensation layer minimizing wafer bow for thinned substrates. Applied to the back side of the GaAs wafer, it is important to avoid mechanical damage to the active layers on the frontside. SPTS’s Delta™ PECVD offers an “edge-contact” option with a modified platen and pin-lift which eliminate the need for expensive frontside protection layer.
There are a number of features of the Delta APM module which are important to CS applications (as well as standard silicon) namely:
The Delta™ fxP PECVD is an excellent choice for deposition of dielectrics for a wide range of compound semiconductor applications. It offers a flexible solution that combines excellent dielectric film properties across a wide range of deposition temperatures, combined with high throughput and repeatable processing performance in high volume production
Overview of the plasma processing technologies which SPTS offers for a variety of compound semiconductor applications such as RF, power and photonic device manufacturing.Download
You are using the DNT flag, so cookies related to preferences, statistics and marketing have been disabled.
Necessary cookies help make a website usable by enabling basic functions like page navigation and access to secure areas of the website. The website cannot function properly without these cookies.
|laravel_session||spts.com||Used internally to identify a user||2 hours|
|XSRF-TOKEN||spts.com||Used to protect against cross-site request forgery||2 hours|
|cookie_control||spts.com||Used to remember Cookie Consent preference||2 hours|
|download_details_id||spts.com||Used to remember that the gated form has been filled on downloads||1 month|
|_GRECAPTCHA||google.com||Used when presenting a CAPTCHA when filling out forms||Session|
|player||player.vimeo.com||Required for Vimeo video player||1 year|
|vuid||player.vimeo.com||Required for Vimeo video player||2 years|
|OptanonConsent||player.vimeo.com||Required for Vimeo video player||1 years|
|vimeo_gdpr_optin||player.vimeo.com||Required for Vimeo video player||10 years|
There are no first-party cookies being used for user preferences.
|_ga||spts.com||This cookie is set by Google Analytics for providing browsing statistics. This cookie is used to distinguish users||2 years|
|_gid||spts.com||This cookie is set by Google Analytics for providing browsing statistics. This cookie is used to distinguish users||24 hours|
|_ga_NFV3HF22VQ||spts.com||Used to persist session state||2 years|
|_gat_gtag_UA_15972496_3||spts.com||Contains campaign related information||90 days|
|_hjid||hotjar.com||Hotjar cookie that is set when the customer first lands on a page with the Hotjar script. It is used to persist the Hotjar User ID, unique to that site on the browser. This ensures that behavior in subsequent visits to the same site will be attributed to the same user ID.||1 year|
|_hjAbsoluteSessionInProgress||hotjar.com||This cookie is used to detect the first pageview session of a user. This is a True/False flag set by the cookie.||30 minutes|
|_hjIncludedInPageviewSample||hotjar.com||This cookie is set to let Hotjar know whether that user is included in the data sampling defined by your site's pageview limit.||30 minutes|
|_hjFirstSeen||hotjar.com||This is set to identify a new user’s first session. It stores a true/false value, indicating whether this was the first time Hotjar saw this user. It is used by Recording filters to identify new user sessions.||Session|
|hotjar.com||Hotjar can set other cookies under specific circumstances. For a full list, please see the full list here: https://help.hotjar.com/hc/en-us/articles/115011789248-Hotjar-Cookie-Information#cookies-set-by-the-hotjar-script|
There are no first-party marketing cookies being used.