Should you build or buy a yield management system?


Is it ever worth re-inventing the wheel? Every industry outsources key functions over time. Airlines outsource baggage handling, construction companies outsource pipe-laying. Many fast-growing technology companies outsource enterprise software and many are tempted to build their own. Yield Management Software (“YMS”) is no different.

Why have a YMS at all?

Whether built internally or bought from a vendor, YMS is essential for saving costs and delivering product on-time and with high quality. Manufacturing more wafers just to get enough product to a customer is not good enough. Your margin will disappear and your competition will eat your lunch. On the other hand, providing your engineers with real-time in-depth engineering information from manufacturing has an indisputable ROI. Informed decisions will be made quickly by your skilled engineers to improve your margins and optimise delivery and quality.

Why not build your own?

If I am involved in running an up-and-coming semiconductor company and have a few engineers who are skilled in IT, then I could have them work for a few months on bringing all our data together from our subcons and providing a database accessible by everyone working on yield. These internal IT specialists would be tasked to provide a web-site which is searchable by manufacturing stage and lotid. Any engineer throughout the company could download any data they want when they want it. Indeed I could just hire maybe 5 people to do this for six months. That would cost maybe $300,000 and then I would have a great system for my ten or so end users, right?

Well, let’s see!

Since you’re an up-and-coming company, it may well fulfil your needs initially, but your data volume will grow and your requirements are going to change. So you think: “OK, I’ll hold on to one or two engineers and then 50% of their time can be on the ongoing debug and support of the system.”

So now it’s costing $100K+ a year. Vendors are calling talking about how they can link up the data across manufacturing but one of your engineers in Taiwan says he also can do that within the next few months. You buy new testers and new formats other than industry-standard formats like STDF appear. The IT guys working on the system are not sure about the actual DB design as they were more familiar with the UI and training the users. Then the engineer who wrote the scripts for characterising devices has just retired. And his scripts are not fully documented. The Taiwan engineer got dragged into another project. It’s difficult to find a replacement as it’s specialised work. The cost of all this is only going one way.

The number of people who need to use the system is now above twenty but the support for them is erratic. You will have to invest another couple of hundred K very quickly in specialist hires. Vendors are quoting a fraction of the per annum cost for the current number of users you have for your own YMS and are comfortable with your data formats. But you say, no, I’ll plough ahead with my internal YMS solution.


Six months later, you have decided to move your test engineering to Taiwan to be closer to the foundries. So half the users will be offshore and you don’t have training and support available for them in the YMS, not even taking into account their time-zone. In addition, the website is starting to crash because your volumes have more than doubled and the design was only capable of operating with half a terabyte of data.

New Opportunity Missed

There is a cheaper multisite test solution for testing products from a low margin but fast-growing product line and the YMS is not capable of analysing the data at all. The compatibility of the new data format with the YMS was an afterthought. Now an opportunity has come up for that product line to move to automotive, but since they can’t see the production performance easily, the decision is being slowed, potentially missing a higher margin opportunity.

Advantages of using a Vendor

If however a good and established vendor were used from day one, the setup cost would have been a lot less and every one of the issues encountered would not have been a big deal. YMS vendors, if they are worth their salt, can set up a system for a small but fast-growing company in a few weeks maximum. They would not just provide a website where you can download the data. They would provide an interactive website where you can directly analyse it without downloading the data. You would not have to pay them fully until they delivered to your requirements.

Customers like You

The vendor would link up the data across manufacturing, assuming you have a good MES/ERP system they can use. New formats to you would not be new formats to the YMS vendor. They probably have 30 or 40 customers like you with all types of formats and access to the best ideas for your next YMS challenge. They might have to tweak some parsers but this should not cost the earth.

You would ideally have a multi-year contract with the YMS vendor. Include minimum support requirements in the contract and you should have no worries.

The YMS vendor will also have highly skilled support in different continents. The database design will be able to scale to Terabytes, so don’t worry about fast ramps when you get your contract from Cupertino!

If you move into automotive, the vendor will have all your requirements available in terms of data and monitoring. If you have particular needs, they will work with you quickly and efficiently on them.

Needs Evolving Over Time

So as your needs evolve, your YMS vendor probably already has a solution or can develop one quickly. For example, you may need a special type of SPC alert. You can include in the contract the requirement that the system is extended and upgraded at a reasonable frequency. The vendor should have the skill set to do almost anything you dream up that would help with your yield, quality and even reliability. They will probably charge NRE for custom requirements.

IP considerations

If you are concerned about the IP of the data being generated, ask the YMS vendor if you can host everything yourself. The vendor should be able to support this and not even have to ever see your real data.

Financial Considerations

If your vendor already supplies to much larger companies than your own, their financial stability should not be a concern, but sometimes a vendor may be under pressure by its investors to charge a lot of money. Make sure you know the ongoing costs of upgrades and maintenance. Know who is backing the vendor financially. Some vendors have sold out recently so make sure you cover such a situation in the contract.

Other considerations

Does the vendor have customers who will attest to their after-sales service? Have they demonstrated that they are responsive and agile? How many years have they been in business?

Summary of Advantages of Buy instead of Make

  • Set-up speed Can set-up very quickly, probably days or weeks not months (unless you’re a very big company)

  • YMS Design Scalable and Robust, built on tens of man-years’ of experience

  • Data Variations Has probably seen them all before & dealt with the extremes

  • Software Development Probably uses latest S/W development methods (Agile etc)

  • Support Probably has Worldwide support. Not dependent on certain people. Teams of support engineers

  • Maintainability Probably very stable, scalable system which requires very few resources to support

  • Integration Probably has worked with your MES/ERP before and can integrate with it

  • Depth and Breadth of Analysis Tools If the vendor is in business for years, they will probably have 99% of what you will ever want & if you want something custom, they will be able to do that for you for a minor cost


If after all the above you still are tempted to develop the YMS solution in-house, just make sure that the database design is scalable and that the engineers developing this internally are not going to be distracted from their YMS job by other IT needs later on.

We would obviously recommend contacting a vendor like ourselves and let you concentrate on making the best semiconductors possible.