Technology ”Our technologies verifies each other”

MD         Membrane Destillation. Many implementations exists but only Winsty generates APW

NDLS®  Nanosized’s DLS-based analysis method

APW®    Water generated by Winsty and verified as contamination free by NDLS® and offline dry methods like ESCA and SEM

NPW      APW stored in hydrophobically coated vessels

Primary-/Secondary-/Tertiary contamination

• Primary contamination. Residual contamination after polishing at Point-of-Delivery
• Secondary contamination. Induced by bacterial growth and abrasion/dissolution processes between PoD and PoU.
• Tertiary contamination. Generated by tools like SRD after PoU

PoD        Point-of-Delivery. Water department guarantee UPW quality down to this point.

PoU       Point -of-Use. Water from various taps and connections used up in the clean area

Recipe  Standard procedure for tools and operations. Recipes are either commercial or generated by fab operators themselves, so called Recipe Creation.

RO          Reverse Osmosis. State of art method for generation of UPW

SRD        Spin-Rinse-Dry. State of art rinsing in the fab is performed using SRD-units. There are multiple such units. Severe generator of tertiary contamination

Tool       Mass-fabrication equipment of various types in semiconductor fabs

TAWA   Total Available Wafer Area. A key figure in fab production economy defined as a fabs total wafer area times percentage uncompromised area after wafer start.

Virgin Water       APW used instantaneously. Not stored in vessels nor transported in tubing’s or   pipelines

Winsty  Nanosized’s patented module for APW based on Membrane Distillation

UPW      State of art Ultrapure water, typically generated by Reverse Osmosis and subsequent purification steps like UV treatment, ION exchange, filtering etc. (Polishing).

YET™     Yield Enhancement Tool. A series of ”production tools” comprised by a Winsty unit, a  wafer rinsing module and software. It comes in two versions designed to be located in the fabs clean area delivering Virgin Water to be used “On-Demand”, “Just-in-Time” @ “Point-of-Use” for rinsing. First version is for bare wafers at Wafer Start.

Droplets of Nanosized APW is added to a bare Silicon wafer. After desiccation, the surface is examined using ESCA (Electron Spectroscopy for Chemical Analysis). To focus the ESCA instrument 245 nm Latex nano spheres are used.

The ESCA result is shown in the figure below were present chemical elements of the Silicon wafer surface have distinct peaks along the x-axis.

The elemental composition of the Silicon surface show sole presence of Oxygen (O), Carbon (C) and Silicon (Si) i.e. only expected chemical elements of a Silicon wafer and the conclusion is that APW did not add nor left any residue of matter or substance at all.

Mass spectrum analysis conclusions

Due to the ESCA results shown above there is no need to further evaluate contamination content quantitatively using mass spectrum analysis because there is nothing further to evaluate.

Also moving a sample outside a clean-room environment will degrade that sample.

The strategy for NPW-generation is based on Membrane Distillation. However, first a wet analysis (c.f. PoC – Metrics…) had to be developed to enable an iterative development process. Dynamic Light Scattering (DLS) was regarded to provide a technique sensitive enough as a basis. Thereafter a series of modules and prototypes was developed, tested and adjusted until the present YET-P2 was installed and proven to generate true NPW.

The following three graphs shows the aggressiveness of Virgin water. Over time when stored in a vessel it will start to dissolve the walls of the storage-vessel. The vertical axis shows the Hydrodynamic diameter which is a weighted meanvalue of the particle sizes measured by DLS.

The graphs show the particle degradation when Virgin water is stored in a vessel of Glass, Polypropylene and PVDF.

The proprietary analysis method NDLS was applied on a conventional facility for RO-based UPW. Results were encouraging as a validation of NDLS which, unfortunately, disclosed poor quality of the UPW. However, to measure is to know. NDLS was used to determine UPW quality before and after regular service proving effect of these activities. Anecdotically, UPW quality was found to be better before than after the week-end just as before and after the pandemy, indicated bacterial growth in the system.

Due to the remarkable aggressiveness of Winsty™ water, unless hydrophobically coated pipes (expensive) were installed, Winsty water needs to be produced @ Point-of-Use. The volume needed to rinse/clean a 12″ wafer is expected to be ~1.4 litres and the design of a Winsty module is such that NPW can be dispensed On-Demand and Just-in-Time.

The concept realized by a Winsty module is therefore disruptive in its nature and calls for a paradigm shift, since rinsing water is now produced within the clean room, precisely dispensed in no excess just when needed, making the 100-fold reduction of water consumption feasible.

At July 5 2019 a comparison was made rinsing virgin wafers, after standard HF 5% cleaning and rinsing with the standard UPW used in fab’s of today and the Nanosized Winsty water, NPW.

The summing results show the outstanding superiority of the NPW compared to the standard UPW. In fact, the NPW leaves a result on the virgin wafer so clean that the SEM cannot detect anything at all since a SEM can’t focus on the surface of a very clean bare/virgin Silicon wafer.

The UPW on the other hand leaves traces of bacteria, larger stain(s), and possibly viruses, smaller stains. Further on, several white “lumps of sugar” which the SEM-operator recognizes as typical contamination from organic origin.

The photo shows the residual of evaporated UPW.

Cleaning in the semiconductor industry is normally accomplished using acid like HF 5% and then rinsing using the current UPW. The Nanosized virgin water (NPW) primary use is for rinsing however with the following four (4) experiments we will show a remarkable NPW cleaning effect visualized by a Wafer Inspection System WIS150 for particle inspections.

The top picture shows an inspected virgin wafer whitout a removed protective SiO₂ layer while the bottom picture shows the same wafer dipped for 1 min in 0.2 l NPW after HF cleaning.

The following picture shows the very unsatisfying result of a virgin wafer having been spin rinse dried (SRD) with a spin dry time of 10 min.

Scenario a) below shows the particle count result of the above picture and scenario b) shows the particle count result after the wafer have been subject to 1 min dip in 0,2 l NPW. The table sums the results, describes the flaws and calculates the relative.

• • Note 1: This is a cleaning result of NPW which normally would have been a HF 5% job
  • Note 2: The absolute values of the particle count should be used with care however their relative weight is very accurate

In this experiment we let a dry virgin wafer lay around in open air in the clean room environment for some time. The DB2 count show the particle count of that wafer without any additional processing while the DB1 count shows the effect of a 1 min dip in 0,2 l of NPW of that same dry wafer. Again the table shows the relative numbers of the particle count.

• • Note. This is a very tough test for a non-acid spiked water normally used for rinsing. This shows the effect of NPW on a dry Si surface which is more cumbersome than rinsing a wet Si surface. See the PoC – ”Cleaning a virgin wafer”

At Nov 24 2021, an expert in the field, carried out an analysis using the Thermo Fisher AAS iCE 3000 on three different water types determining Fe-ions and particle content:

1. De-ionized water (Milli-Q®)
2. Reference water (Thermo Fisher). For analysis, Purity grade PA
3. Winsty™ water

Three samples of each water were analysed for Fe-ions and particle content with the following results: 

1. DI water          0.000/0.000/0.000 (ppm),  Particles present, Fe-ion free
2. Ref water        0.001/0.010/0.001 (ppm),  Particles and Fe-ions present
3. Winsty water  0.000/0.000/0.000 (ppm),  Particle free,  Fe-ion free

To obtain simultaneous proofs on absence of metal ions in NPW (c.f. PoC – Analysis of Fe-ions …) and the validity of NDLS, comparative analyses were performed using a standard method, Atomic Absorption Spectroscopy (AAS) on the same samples as NDLS.
An Fe-ion standard was analysed and NPW was proven to be totally free from Fe-traces. The study also proved the utility of NDLS to determine presence of Fe down to ”zero” were AAS failed several dilutions earlier.

The following video shows the need to use IPA (Isopropanol Alcohol) to remove dry spots after rinsing silicon wafers with the current standard UPW (RO, Reversed Osmosis based).

The non-existent dry spots using Nanosized NPW is verified using ESCA (Electron Spectroscopy for Chemical Analysis) surface analysis.

A step in the rinsing process potentially can be removed when using Nanosized NPW ”Virgin water”. IPA is also a high-risk substance due to it being highly flammable.

Six (6) drops of UPW and NPW respectively are left to dry on a silicon wafer.